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Commercial Buildings Special Working Group
Guidance document
Reduced energy use and
improved energy efficiency through
operational and maintenance practices.
1
1.
Introduction
Directive 2002/91/EC of the European Parliament and Council, on the energy performance of
buildings, came into force on 4 January 2003, intended to lead to substantial increases in investments
in energy efficiency measures within buildings.
The 160 million buildings in the EU use over 40% of Europe’s energy and create over 40% of its
carbon dioxide emissions, and that proportion is increasing1.
•
Under the Kyoto protocol, Europe is committed to reducing emissions and the Directive is
intended to contribute to achieving this.
•
•
•
Heating fuel is the most important component
o
57% of domestic consumption
o
52% of non-residential building consumption
Water heating accounts for:
o
25% of domestic consumption
o
9% of non-residential use.
Lighting accounts for up to 25% of emissions due to commercial buildings.
The guidance document was commissioned by companies in the commercial sector that are seeking
to identify and implement energy saving opportunities and improve energy efficiency through
improved Operational and Maintenance practices.
This document serves to provide reference in a single source outlining energy saving potential in the
commercial sector and particularly for the significant energy aspects affecting energy use in the
commercial sector but should not be considered as a definitive guide. For detailed guidance, the
reader is advised to seek specialist advice
Building operation and maintenance (O&M) programs can enhance the operating efficiency of the
building and associated HVAC, Hot Water, lighting, and other energy-using systems.
An effective O&M program should:
•
Set demanding goals which should be reviewed on a regular basis for effectiveness
•
Measure performance indicators such that the building can be benchmarked against other
buildings
1
CIBSE Briefing 6 of EPBD 2003
SEAI Energy Policy Statistical Support Unit
3
DTI / BRE
2
2
•
Adjust to changing occupant demands by modification of HVAC, Lighting, automation
settings etc. as applicable
•
Assist the repair, upgrade and re-commissioning of building systems to meet the current
needs
•
Minimise unplanned failures in the building and systems
An effective and properly designed O&M plan includes the upkeep of the systems such as HVAC, such
that efficiency targets are met over the whole life of the system. Fundamentally, O&M plans are a
means through which long terms goals of improved economy, energy efficiency and resource
conservation are achieved while meeting the health and safety and comfort of the occupants.
Further reference on the key elements of a strategic O&M plan is included in section 15
3
Table of Contents
1.
Introduction ....................................................................................................................... 2
2.
Scope and Methodology ................................................................................................... 8
2.1.
Scope ................................................................................................................................ 8
2.2.
Methodology ...................................................................................................................... 9
3.
Commercial Sector energy analysis .................................................................................. 9
4.
Typical areas of significant energy use ........................................................................... 16
4.1.
Hot Water Generation and Distribution ........................................................................... 16
4.1.1. Fuel Purchasing .............................................................................................................. 17
4.1.2. Boiler Sequencing Controls ............................................................................................. 17
4.1.3. Optimum Firing Strategy ................................................................................................. 18
4.1.4. Air Fuel Ratio .................................................................................................................. 19
4.1.5. Exhaust Temperature ...................................................................................................... 20
4.1.6. Condensing Boilers ......................................................................................................... 20
4.1.7. Distribution Pipe Insulation .............................................................................................. 21
4.1.8. Radiator Circuits Thermostatic Valves ............................................................................ 22
4.1.9. Domestic Hot Water (DHW) ............................................................................................ 22
4.2.
Heating Ventilation and Air conditioning (HVAC) ............................................................ 25
4.2.1. Economy Mixing Section ................................................................................................. 28
4.2.2. Filtration .......................................................................................................................... 30
4.2.3. Heating and Cooling Coils ............................................................................................... 34
4.2.4. Fan and Motor ................................................................................................................. 37
4.2.5. Equipment Calibrations ................................................................................................... 38
4.2.6. Building Management Systems (BMS) ........................................................................... 40
4.2.7. Air Changes per Hour (ACPH) ........................................................................................ 40
4.2.8. HVAC Three Port Valves ................................................................................................ 41
4.2.9. Split Condensing Units. ................................................................................................... 42
4.2.10. Data Server Rooms ......................................................................................................... 44
4.2.11. Computer Room Air Conditioners (CRAC) ...................................................................... 45
4.2.12. HVAC - Further reference ............................................................................................... 47
4.3.
Lighting ............................................................................................................................ 49
4.3.1. T5 Fluorescent lamps ...................................................................................................... 50
4.3.2. Magnetic Ballasts ............................................................................................................ 50
4.3.3. Electronic Ballasts ........................................................................................................... 51
4.3.4. High Bay Lighting ............................................................................................................ 52
4.3.5. Lighting Control Mechanisms .......................................................................................... 54
4.3.6. Group Re-lamping ........................................................................................................... 56
4.3.7. Average Rated life and lumen Output ............................................................................. 57
4.3.8. Exterior Lighting .............................................................................................................. 57
4
4.3.9. Daylight Harvesting ......................................................................................................... 58
4.3.10. Lighting Recommendations ............................................................................................. 60
4.3.11. Lighting – Further reference ............................................................................................ 62
4.4.
Cooling and Refrigeration ............................................................................................... 62
4.4.1. Refrigerant Charge .......................................................................................................... 69
4.4.2. Chilled Water Systems Thermal Expansion Valve .......................................................... 70
4.4.3. Refrigeration Recommendations ..................................................................................... 71
4.5.
Compressed Air .............................................................................................................. 73
4.5.1. Compressed Air Recommendations ............................................................................... 74
4.5.2. Compressed Air Further reference guides ...................................................................... 75
5.
Office Equipment ............................................................................................................. 76
5.1.
General Office equipment ............................................................................................... 76
5.2.
Office Equipment (Computers) ........................................................................................ 77
6.
Building Fabric ................................................................................................................ 79
7.
Water Usage ................................................................................................................... 79
8.
Operational and Maintenance Improvements ................................................................. 81
8.1.
Operation & Maintenance Assessment ........................................................................... 82
8.2.
Service Utility Agreements .............................................................................................. 83
8.3.
Maintenance Management .............................................................................................. 83
8.4.
Best Maintenance Practices ............................................................................................ 84
8.5.
Proactive and Reactive Maintenance .............................................................................. 85
8.6.
Purchasing of energy efficient equipment ....................................................................... 85
9.
Motors ............................................................................................................................. 86
10.
International Energy Policy ............................................................................................. 87
11.
Irish Policies ................................................................................................................... 87
11.1.
Energy Performance of Buildings .................................................................................... 88
12.
Safety Health and Welfare at Work ................................................................................. 90
12.1.
Minimum Temperatures in the Workplace ...................................................................... 90
12.2.
Maximum Temperature in the Workplace ....................................................................... 91
13.
Sustainable Energy Ireland Programmes ....................................................................... 91
14.
Energy Management – The benefits of a systematic approach ...................................... 92
15.
Guidance for analysis of a commercial buildings O&M aspects using this guide. .......... 93
15.1.
Recommended approach to usage. ................................................................................ 93
15.2.
Gathering of existing knowledge. .................................................................................... 93
15.3.
Assessment of current energy data. ............................................................................... 93
15.4.
Assessment of areas of significant energy usage ........................................................... 94
15.5.
Assessment of maintenance practices ............................................................................ 96
16.
Setting an appropriate reduction target. ............................................................................ 97
17.
Verification of improvements. ............................................................................................ 97
5
Table of Figures
Figure 1: Primary Energy Demand (Commercial Sector 1990-2008) .................................................................... 11
Figure 2: Energy demand by utility (Commercial Sector) ......................................................................................... 14
Figure 3: Boiler Sequence Control for Multiple Boiler Installations ...................................................................... 18
Figure 4: Excess air versus efficiency ................................................................................................................................ 19
Figure 5: Thermostatic Radiator Valve ............................................................................................................................. 22
Figure 6: Instantaneous Electric Hot Water Heater ..................................................................................................... 24
Figure 7: Schematic Representation of All-fresh Constant Volume AHU ............................................................ 27
Figure 8: (Example) Overview of typical Air Handling Unit component operations ...................................... 28
Figure 9: AHU incorporating Economy (Mixing) Section .......................................................................................... 29
Figure 10: AHU Filter Life Cycle Cost ............................................................................................................................... 31
Figure 11: Equation for calculating energy loss due to pressure drop ................................................................ 31
Figure 12: (Example) Follow manufacturer recommended Panel Filter Installation Orientation .............. 32
Figure 13: (Example) Recommended Bag Filter Installation .................................................................................... 33
Figure 14: Recommended Type of Bag Filter ................................................................................................................ 34
Figure 15: AHU heating coil showing blockage (Partially Cleaned) due to dirt and debris ......................... 36
Figure 16: Relationship between belt tensioning and fan performance ............................................................ 37
Figure 17: Internal ceiling mounted cassette unit....................................................................................................... 42
Figure 18: Roof top condensing unit (Incorporating Condenser Fan) ................................................................. 43
Figure 19: Fluorescent Lamps indicating Blackened Rings (End of Useful Life) ............................................... 51
Figure 20: Dimmable fluorescent daylight linking control ...................................................................................... 56
Figure 21: Lamp Type Rated Light output...................................................................................................................... 57
Figure 22: Daylight blinds prevent Excessive Solar Glare Reflection .................................................................... 58
Figure 23: Daylight Blinds Room Illumination during bright sunny days ........................................................... 59
Figure 24: Daylight Blinds operation during dull exterior weather conditions. ............................................... 59
Figure 25: Daylight Blinds operation during times of extreme solar glare. ....................................................... 60
Figure 26: Example – Comparison of Co-efficient of Performance of a YORK VFD Centrifugal
compressor versus a fixed speed compressor .............................................................................................................. 68
Figure 27: Vapour Compression Cycle (Single Stage Refrigeration Cycle) ......................................................... 68
Figure 28: Refrigerant Sight Glass ..................................................................................................................................... 69
Figure 29: Electronic Expansion Valve Installation ...................................................................................................... 70
Figure 30: Refrigeration Plant Energy factors ............................................................................................................... 72
Figure 34: Indication of breakdown of energy feed to an air compressor in terms of energy end
dissapation................................................................................................................................................................................. 73
Figure 35: Compressed air key maintenance locations (Simplified Overview) ................................................. 74
Figure 32: Average loads of Office Equipment with potential standby savings .............................................. 77
6
Figure 33: Breakdown of Energy Consuming Equipment (Office Building) ....................................................... 77
Table of Tables
Table 1: Sector Electricity Demand Growth Rates and Share Rates ...................................................................... 12
Table 2: Sector primary fuel source growth rates (1990-2008) ............................................................................... 13
Table 3: Hot water provision by end user and heat source ...................................................................................... 24
Table 4: LPHW – Typical Energy factors and corrective actions ............................................................................. 25
Table 5: ASHRAE Guidelines on Temperature and Humidity Bands for Data Centre’s .................................. 45
Table 6: Example: Planned Maintenance Check-list for HVAC system and components.............................. 46
Table 7: HVAC - Typical Energy factors and corrective actions ............................................................................... 48
Table 8: Fluorescent lamp comparisons (Watts and Energy Savings) .................................................................. 50
Table 9: Comparison Table of Fluorescent vs. HID High-bay lighting .................................................................. 53
Table 10: Lighting – Typical Energy factors and considerations for corrective action ................................... 61
Table 11: Refrigeration – Typical Operational Energy factors and corrective actions .................................... 72
Table 13: Compressed Air – Typical Operational energy factors and corrective actions .............................. 75
Table 12: PC - Energy factors ............................................................................................................................................... 78
7
2.
Scope and Methodology
2.1. Scope
The scope of this document is to provide guidance to the commercial sector regarding
potential operational and maintenance improvements to increase energy efficiency /
reduce energy use, with a particular focus on Significant Energy Users
The systems identified as Significant Energy Users by the sector, which are covered in some detail in
this guideline are outlined below:
• Heating, Ventilation and Air Conditioning (HVAC), including Building Management Systems
(BMS).
• Refrigeration systems, including cassette air conditioning units.
• Low Pressure Hot Water (LPHW) systems.
• Lighting
• Compressed air, small scale generation.
• IT Equipment, including servers
• Building infrastructure
Key to using the guide
The blue box contains a key note or recommendation
•
Refer to the contents section for the particular technology, activity which is being
considered for improvement.
•
The majority of the sections contain keynotes which are highlighted in a ‘blue box’.
o
Where applicable, further reference notes are included in the section following the
‘blue box’ which may include further detail and / or reference.
•
N.B. This is a guidance document and as such, for each of the technology sections there
are many detailed guidance documents available for further detail.
o
For example, the CIBSE series of guidance documents can provide more definite
advice on topics covered e.g. Maintenance - CIBSE Guide M Maintenance
Engineering and Management.
8
2.2. Methodology
In order to get a comprehensive understanding of the current operational efficiency of the sector,
information on the significant energy usage was requested from individual companies associated
with the Special Working Group (SWG).
Statistical data was also reviewed to obtain a broader picture of the performance of the sector.
The methodology undertaken was generally as follows:
•
Liaise with members of the sector on current operational and maintenance practices of their
respective equipment.
•
Review statistical data on the current consumption trends of the sectors.
•
Indicate operational improvements on all equipment identified
•
Indicate maintenance procedure improvements on all equipment identified
•
Indicate where technological advancements in operational efficiencies may warrant the
replacement of worn equipment to a revised selection.
•
Indicate where procedural improvements on maintenance management systems will
provide savings
•
3.
Indicate where civil improvements on building fabric can provide operational savings.
Commercial Sector energy analysis2
The rate of growth in commercial sector energy consumption in the last 25 years has been
approximately three times greater than in the domestic sector, and is projected to exceed
growth in all other sectors except transport.
•
Growth in energy consumption is partly explained by expansion in floor space, with offices, for
example, occupying almost twice as much floor space in 1994 as they did in 1970.
There has been an increase in specific energy demand in some types of commercial premises, with
the growth in demand for:
• Space heating
• Cooling
• Lighting
• Information Technology.
2
SEAI Energy Policy Statistical Support Unit
9
In the office sector demand for air conditioning has grown rapidly, and this has led to a significant
increase in CO2 emissions in relation to energy use.
The proposed changes to Part L of the Building Regulations are expected to give rise to
CO2 savings of only a fraction of the magnitude of the cost-effective potential, and will
have limited impact on existing buildings.
There can be other substantial side-benefits to investment in energy efficiency other than
just the energy use and associated cost reduction
•
Improved worker comfort
•
Health and safety
•
Productivity.
Traditionally energy efficiency policies and programs have focused on the domestic and industrial
sectors, and tended to overlook the service sector. This is reflected in the way statistical data has
detected the increase in (absolute) consumption trends.
Over the period 1990-2008 in the commercial services sector:
•
Final energy consumption grew by 80% (3.3% per annum)
•
Value added generated by the sector, grew by 157%
•
Numbers employed more than doubled (128% increase)
•
Electricity consumption in services increased by 242% (7.1% per annum)
o
representing 45% of energy use in the sector, up from 24% in 1990
To compare how effective these figures are a comparison can be made to the industrial sector:
•
In 2008 the economy entered recession, with gross domestic product (GDP)
falling by 3% compared with 2007.
•
Primary energy use grew by 1.5% in 2008 and energy-related emissions
increased by 1.3%.
However when we focus on how each sector performed we can see how one sector performed
better than the other:
10
•
The industrial sector experienced a decrease in final energy use by 5.4% in 2008
relative to the previous year.
•
The commercial and public services sector experienced an increase of 6.9% in
final energy use in 2008.
Figure 1 shows that the sector has seen a disproportionate increase in Primary energy demand.
Space conditioning has being identified as one of its significant energy users in the
commercial building sector and it has been seen that the sector has had a shift in
emphasis from the traditional heating medium of oil to natural gas and electricity.
Figure 1: Primary Energy Demand (Commercial Sector 1990-2008)
•
Energy demand increased by 6.9% in 2008, or by 1.9% after normalizing for the weather
effects.
•
It can generally be shown that weather fluctuations are one of the most significant energy
drivers for the sector, due to space heating and cooling being one of the biggest energy
demands.
•
Electricity demand increased by 9.7% in 2008 compared with a growth of 4.1% per annum
during 2005 – 2008.
•
What is notable when analyzing this data is that, although the sector was subject to an
increase in energy demand, the economy was beginning to contract, whereas traditional
expectations would be that the profiles would mirror sector performance?
11
It is believed that the reason for this is that although there was a slowdown in turnover and a
•
reduction in employee numbers, the energy requirements of building space conditioning
remained unchanged.
Table 1: Sector Electricity Demand Growth Rates and Share Rates
Sector growth and performance reflects GDP output whereas it may have been expected
•
that electrical energy demands would be reflected throughout all the sectors.
When comparing the commercial sector to the industrial sector, its nearest competitor based
•
on GDP, it can be seen that the industrial sector saw a net decrease in energy demands of
5.9% for the corresponding timeframe.
What this highlights is that although industry would have a relatively high base load
•
compared to the commercial sector it was still able to achieve net results. This may be
attributed to the sector actively implementing energy management policies but it may also
be a reflection of the different energy drivers seen within the manufacturing sector.
EPSUU data gathered by SEAI has indicated the following:
•
Direct fuel use increased by 4.7%
o
Compared with 1.0% per annum in 2005 – 2008.
Although this data does not indicate consumption trends per individual year, it does highlight
an increase in consumption:
•
Oil demand reduced in 2008
•
Gas demand grew by 11%.
•
Renewable energy grew by 50% albeit from a very low base.
12
Table 2: Sector primary fuel source growth rates (1990-2008)
The commercial sector has seen unprecedented change during the last decade:
•
Floor space has significantly increased.
•
52% reduction in oil demand
•
130% increase in natural gas demand
•
91% increase in electrical demand
This indicates the large shift towards natural gas and electricity usage as
opposed to more traditional forms of fuel.
13
Figure 2: Energy demand by utility (Commercial Sector)3
For all building categories in the commercial sector, the areas of significant energy use are
heating, hot water and lighting.
The focus of energy reduction is normally best focussed on the areas of significant energy use on the
basis that this will be most likely place to lead to the larger reductions in consumption.
The following section presents a brief summary of the developments in relation to the key
technologies used in the commercial sector.
3
DTI / BRE
14
An energy aspect is an element of an organisations activities, goods or services
that can affect energy use or energy consumption
An energy aspect is considered significant if it accounts for a high
proportion of a sites energy use and has a potential for one or more of the following:
•
More efficient energy use
•
Increased use of embedded renewable technology
•
Increased energy exchange with the rest of society
Where should you focus your energy reduction efforts?
To identify where the significant potential reductions can be achieved it is important first of all to
appreciate what the Significant Energy Users in the sector are. Figure 2 indicates where energy is
typically used throughout the sector in terms of significance and in relation to the category of
building. It is most likely that the largest energy users will be the most significant energy aspects, i.e.
the greatest potential for energy reduction and improved energy efficiency.
Heating
•
Traditionally met by Low Pressure Hot Water (LPHW) radiator circuits
o
Now being met by a mixture of:

LPHW radiator circuits

Air Handling Units (AHU’s)

Cassette ACU’s

Electrical fan coil units

Natural gas radiant heaters.
Hot Water
•
This demand has been traditionally met by calorifiers indirectly heated from heating circuits
(LPHW) and by electrical element boilers or oil boilers in large installations.
o
This sector has seen a shift towards natural gas boilers
o
Also accounts for the growth market in renewable energies through solar hot water
heating.
o
Additionally with the development of the biomass fuel industry the sector has seen
increased use of fuels with less negative environmental impact
Lighting
•
The sector has seen significant growth in floor space
15
o
Resulted in an increase in artificial lighting and demand for improved lighting quality.
o
There have been significant improvements in lighting technologies that can assist the
sector in improving energy performance in this area.
Catering
•
This sector has seen a significant shift towards natural gas although electrical demand has also
increased.
•
Refrigeration can also have a large energy impact in this sector with many hotels and large
restaurants installing walk in fridge/ freezer units.
Cooling Ventilation
•
The demand in cooling ventilation can be attributed to the
o
Increase in use of AHU’s and ACU’s in the sector.
o
The growth in the IT sector and the development of the data server rooms has seen a
requirement for continuous cooling to protect the data server racks from failing due to
heat fatigue.
Computing
•
With the development of the computerised infrastructure and the transition from paper based
documents to electronic documentation personal computers have become the main working
tool for many in the sector.
•
Simultaneously the sector has seen retail sales transform from cash based transactions to debit
and credit card transactions.
4.
Typical areas of significant energy use
4.1. Hot Water Generation and Distribution
Heating has being identified as the largest Significant Energy Aspect of the commercial
sector (reference Figure 2)
•
Although HVAC systems provide for conditioning space temperatures they require a hot
water system for providing the thermal energy input.
Hot water, commonly referred to as Low Pressure Hot Water (LPHW) distribution systems are typically
used. LPHW is typically generated as a heating medium, within an oil/gas burner, and is pumped via a
distribution system to the various end users such as those listed below
16
•
Air handling Unit (AHU) heating coils
•
Radiator circuits
•
As a primary heat source for a Domestic Hot Water (DHW) calorifier.
•
Warehouse Fan Coil Units (FCU’s)
Oil and natural gas burners are used extensively within the sector, and due to the development of the
biofuels industry, wood pellet/chip burners are seeing increased use.
Additionally with the development of the natural gas network oil fired burners are progressively
being replaced with their natural gas counterparts.
Another significant energy users identified is hot water generation, for Domestic Hot Water (DHW)
purposes. For a hot water system to operate efficiently it is important that a few basic energy and cost
factors be addressed.
4.1.1. Fuel Purchasing
When assessing the operational cost of a boiler the cost of fuel must be factored in. Natural gas is
currently one of the cheapest fuels available, but due to the gas infrastructure network, may not be
available to all members in the sector. Companies who currently burn oil, and are able to
interconnect to the gas network, should consider converting their burner from oil to Natural gas.
Economies of scale can be achieved with multi-site companies purchasing jointly
For multi-site companies, consideration could be given to joint energy purchase contracts
to leverage economies of scale
4.1.2. Boiler Sequencing Controls
The thermal efficiency of a heating boiler decreases when it is operating under low thermal
load due to the increasing significance of fixed heat losses
•
The thermal efficiency of a heating boiler decreases when it is operating under low thermal
load due to the increasing significance of fixed heat losses such as:
•
Radiation/convection losses from the hot boiler casing
•
Draught losses up the flue when the burner is not firing
•
Purge losses when the burner starts up and/or shuts down
17
Energy savings can be obtained in multi-boiler installations by ensuring that only the
minimum number of boilers is allowed to fire at any time.
•
This can be most reliably achieved by installing an electronic boiler sequence controller to
regulate the operation of the plant in response to the heat load.
Figure 3: Boiler Sequence Control for Multiple Boiler Installations
It is highly recommended that companies that have multiple boiler installations incorporate
sequencing control and regularly assess the operational efficiency.
•
Poorly performing boiler sequence controllers are relatively common.
o
A common cause is incorrect adjustment of the sequence controller set-point
relative to the individual boiler operating thermostats.
o
Another common cause with multiple boiler installations is where the heated fluid is
pumped through a boiler that is sequenced off leading to flue losses and radiant
losses in more than one boiler. This can be avoided with correct isolation when
boiler is off, automatically if appropriate.
4.1.3. Optimum Firing Strategy
Optimum start controllers vary the start times of building heating systems depending on the
weather and the heat retention capacity within the building.
•
In milder weather, a building’s heating start times will be delayed, thereby saving energy.
•
The replacement of existing fixed start time control with optimum start/stop control can
typically generate 10% energy savings when compared to heating systems operating to
dedicated time schedules.
18
•
In addition to delivering energy savings, optimum start control can substantially improve
comfort by preventing under-heating at times of occupancy and by shutting down the
heating system during the day if the external temperature rises (Day Economization).
•
Optimum start controls have the capacity to greatly improve the environment and comfort
within the building and deliver operating cost savings.
4.1.4. Air Fuel Ratio
If a burner plant is run with more excess air than necessary the excess air absorbs
heat in the process, energy is wasted in the process, and the energy is lost to atmosphere
through the exhaust stream.
If a burner does not receive sufficient air the burner process is less effective and
excess fuel is lost to atmosphere in the exhaust stream.
Figure 4: Excess air versus efficiency
•
The stoichiometric air/fuel ratio is defined as the exact quantity of air required to completely
combust a particular fuel: for example 1 kg of natural gas typically requires a minimum of
17.2 kg of air for complete combustion.
All burners require a degree of excess air to ensure that the fuel has access to the required
amount of oxygen.
•
It is not uncommon for burners to be operated with inefficient combustion of fuel.
o
For oil burners this is evident with excess soot and heavy emissions at the exhaust
flue/stack or by a white exhaust plume..
•
Typical values of excess air required to achieve maximum efficiency for different fuels are:
o
5-10% for Natural Gas
o
5-20% for Fuel Oil
o
15-60% for Coal
It is recommended that all burners receive a scheduled adjustment per manufacturer’s
recommendations where fuel combustion ratios are set for efficient and reliable operation.
Combustion controls should be adjusted by a competent person at least annually and set
for the actual boiler load requirements as opposed to maximum possible boiler output.
19
4.1.5. Exhaust Temperature
If the exhaust stream temperature is higher than normal, the cause is associated with
either water side or fire side fouling.
•
If fire side fouling, i.e. a buildup of soot and ash, is taking place, the efficiency of heat transfer
from the boiler to the water is reduced and correspondingly the exhaust temperature will be
hotter than normal.
The effect of fireside sooting on fuel consumption is such that fouling of 1-2mm can
increase fuel consumption by as much as 5%.
•
What often occurs is that fouling occurs on the water side because of insufficient or
inadequate treatment chemicals and the poor quality water can cause a layer of calcium or
other suspended material to accumulate on the water side surface.
•
Again boiler efficiencies can be reduced by as much as 5% per 1mm layer of contaminant.
It is recommended that all boilers be serviced and cleaned, if required, based upon
operational hours and inspection. If chemical treatment is lacking, systems may be
flushed and cleaned and appropriate corrosion inhibitor added to the system, in
accordance with boiler system and water treatment specialist specifications.
4.1.6. Condensing Boilers
A condensing boiler will always be more efficient than a non-condensing unit, because
even when it is not in condensing mode it will still give about 85% efficiency - going up to
well over 90% when condensing.
•
A new conventional boiler will be at the very most 78% efficient
•
Older boilers will be between 55 and 65% efficient.
20
Condensing boilers meet the criteria for grade A or B efficiency that are required by the
latest version of the building regulations (Part L).
In order to gain maximum efficiency from a condensing boiler, a good control system must
also be in place.
•
A basic room thermostat and fixed boiler temperature setting will not get the very best out
of a boiler.
A better approach to achieve best efficiency from a condensing boiler is to have an
outdoor weather sensor (known as 'weather compensation') which enables the boiler to
run the central heating only as hot as is necessary, rather than running at the set
temperature all the time.
• When water at a higher temperature is needed for the hot water cylinder, the controls will take
this into account and produce hotter water until the demand is met.
By using a weather compensator, the water returning to the boiler should more often be
in the range required for the flue gases to fully condense, approx 50°C, just below the
'dew point' of the flue = 58°C (Natural Gas fired boiler). The boiler will then be in
condensing mode for most of the time it is operating, so will run at its maximum efficiency
for the majority of the operating time. This should not be attempted on non-condensing
boilers as there is an added risk of corrosion to exhausts
4.1.7. Distribution Pipe Insulation
Insulation on piping is often in a poor condition or perhaps even missing. This increases what is
termed “distribution loses” where the boiler has to burn additional fuel to compensate for the heat
lost from the distribution system. Often these losses can occur in areas which are subject to
overheating, where measures are then taken to dissipate the heat through opening windows and
doors for example.
The insulation of exposed pipe work can pay for itself in a relatively short period where savings are
achieved in reduced fuel consumption. It is therefore recommended that all distribution pipe work
and valves be lagged to appropriate levels.
21
4.1.8. Radiator Circuits Thermostatic Valves
Using TRVs can be part of the controls used in a heating system for it to meet the latest
Building Regulations. Savings of about 10% of heating costs are typically achieved, with a
payback period of typically less than 2.5 years.
•
Thermostatic radiator valves (TRVs), can be used to control low temperature hot water
heating systems with conventional radiators.
•
They control the flow of hot water to a radiator, according to the temperature of the
surroundings. The appropriate use of TRVs can prevent over-heating of a room, hence saving
energy and reducing energy costs.
Figure 5: Thermostatic Radiator Valve
Ensure that the TRV is not obstructed
•
Inadequate heating can result from radiators being covered or blocked by furniture.
•
Radiators only work effectively when they are not obstructed.
•
TRVs should not be covered or blocked.
•
If a TRV is used with a low set-point in one room, ensure the door to that room is kept closed
otherwise the TRVs controlling radiators in adjacent areas will try to heat the air in there also.
4.1.9. Domestic Hot Water (DHW)
To cater for domestic water needs oil and gas boilers also generate hot water, or what is commonly
known as domestic hot water (DHW), at both central and localised locations. The location of the
22
burners depends greatly on the building size and the volume of hot water required. Traditionally
large calorifiers were used for storing hot water, which was pumped around the building to the
various end users.
With the storage of hot water one needs to be mindful of legionnaires Disease.
•
Legionella bacteria can survive under a wide array of environmental conditions and have
been found in water at temperatures between 6.0°C and 55°C.
o
Therefore in order to offset the risk, the cylinder temperature is typically maintained
at a minimum 60°C.
o
The significance of this, as far as energy conservation is concerned, is that stored
water has to be maintained at a temperature greater than what‘s required for end
users purely on health and safety grounds.
o
Care must be taken to ensure that water is delivered to end users at a lower
temperature than 60°C to prevent scalding.
o
It is possible to maintain lower stored water temperatures provided that
temperatures are increased periodically to kill off bacteria. The period depends on
the standard storage temperature chosen.
Manufacturers have developed instantaneous satellite burners, where hot water can be generated on
demand.
•
The advantage that these units have to offer over conventional systems is that generation
and distribution losses associated with large calorifier and distribution systems are reduced.
•
Electrically heated units are also commercially available which can offer a sizable reduction
in installation costs.
•
Electrically heated systems can be viable for systems with intermittent demands.
23
Figure 6: Instantaneous Electric Hot Water Heater
•
Decentralized hot water systems are those where individual heaters are installed close to the
points of supply.
•
They are most often used when there is limited and intermittent hot water demand.
•
Suitably specified, decentralized hot water systems can be installed with payback periods of
under 4 years.
Table 3: Hot water provision by end user and heat source
With the development of the renewable energy sector and especially with solar hot water collector
systems, companies can provide for their hot water needs by installing a suitably sized solar collector
system.
Energy Issue
Unnecessary fuel
consumption
Description of Energy
Wasted
Common Cause for
Occurrence
The LPHW temperature
setpoint does not reflect
the heating requirements.
Traditional control philosophy
of maintaining the LPHW
setpoint at a fixed high
setpoint
24
Corrective action
Incorporate
temperature
compensation
control where a
floating set-point
is maintained
based upon
ambient
temperature
conditions or
another
appropriate
indicator of load
requirement
Poor Firing
Controls
Excessive fuel is being
consumed to generate
load requirements
Burners are not maintained
correctly, linkages on boiler
controls inaccurate, fireside
and waterside fouling, fuel air
mixture incorrect
Base load
excessively high
Fuel being consumed
purely to maintain the
distribution system at
operating temperature
Insulation lacking or
distribution pipes poorly
lagged. Wet insulation
Clean and
maintain burners
at appropriate
intervals,
typically based
on operating
hours., monitor
consumption
rates and check
combustion
controls
Repair/replace
lagging on all
exposed
distribution pipework
For further information on renewable energy systems please reference the SEAI link below.
http://www.seai.ie/Renewables/Solar_Energy
Table 4: LPHW – Typical Energy factors and corrective actions
4.2. Heating Ventilation and Air conditioning (HVAC)
Effective Energy management in Heating Ventilation and Air Conditioning (HVAC)
systems is fundamentally concerned with:
•
Minimising unnecessary consumption of energy resources
•
Providing the desired environmental conditions and services at the lowest cost.
The ranges of commercial building types in which HVAC systems are used are very diverse and may
include:
•
Offices
•
Retail premises
•
Sports centres
•
Cinemas
•
Restaurants
25
Effective energy management involves measuring or estimating energy consumption and
analysis of the relevant energy factors to establish a reasonable basis for improving the
energy performance of the HVAC system.
All the components of the HVAC system need to operate in unison to properly maintain
desired conditions. They use relatively large amounts of energy so applying appropriate
operational strategies and good maintenance practice can significantly reduce energy
consumption.
Air-distribution system components include:
•
Air handling Units and associated components
o
Dampers and linkages
o
Filters
o
Heating and Cooling Coils
•
Ductwork
•
Controls
Most commercial sector buildings incorporate economy, or mixing sections, in their AHU’s.
•
Mixing systems: These systems re-circulate some of the exhausted air from a room into the
fresh air intake to reduce the thermal energy load of the AHU.
Once operated correctly the operational cost of a re-circulating AHU should be significantly
less than for an AHU which uses once through air only
•
The AHU control system can determine the most appropriate mixing of fresh and extracted
air to minimise conditioning energy when compared to an AHU which takes in only outside
air, treats it, transfers it to the conditioned space, and ultimately, the conditioned air is
expelled from the space to atmosphere without recovery of the potentially available energy
(Figure 7)
26
Figure 7: Schematic Representation of All-fresh Constant Volume AHU
•
Air is heated in an AHU by passing it across heating coils.
o
An air heater battery normally comprises of a number of heating elements, arranged
at right angles to the direction of air flow, contained within a sheet metal casing
with flanged ends.
o
The heating elements are either plain or finned tubes, carrying the heating water.
o
The amount of heat added is typically controlled by a modulating valve and is
usually controlled by the Building Management System (BMS) system with
reference to a temperature probe, for example, installed in the air stream after the
pre-heating coil as control reference, or perhaps with reference to the temperature
in the space being heated in the case of the final heating coil.
•
Air cooling coils, sometimes referred to as cooling batteries, are similar to air heaters with the
additional provision of a collection tray and drain for condensate.
o
The cooling medium is typically chilled water and the tubes are normally arranged
horizontally.
o
Large commercial installations, which use chilled water coils, could have one HVAC
chiller which generates the chilled water requirements for all the AHU’s.
o
On the other hand small commercial buildings could have a dedicated cassette type
refrigeration system where the evaporator coil is in effect the cooling coil of the
AHU.
To ensure that an Air Handling Unit (AHU) works efficiently we need to be mindful of how all the
various unit operations interact with each other. For example, inefficient control of a heating coil can
cause a corresponding and unnecessary cooling load.
27
To understand how operational efficiencies can be improved the various components of the AHU will
be discussed.
Figure 8: (Example) Overview of typical Air Handling Unit component operations
4.2.1. Economy Mixing Section
Why consider a HVAC system with a mixing section?
In order to maintain indoor air quality with the least amount of thermal energy input, air
handling units commonly have what’s known an economy or mixing sections.
•
In temperate climates, mixing the right amount of cooler outside air with warmer return air
can be used to achieve the desired supply air temperature.
•
The mixing chamber therefore automatically adjusts the position of the dampers thus
controlling the ratio between the return, outside, and exhaust air.
What is a mixing section?
•
Mixing section dampers consist of a bank of louvers connected via mechanical linkage to
either a pneumatic or electrically driven actuator.
•
Within the commercial sector the predominant actuator would be the electrically driven unit.
28
Figure 9: AHU incorporating Economy (Mixing) Section
Ensure efficient mixing control
To ensure efficient mixing control it is essential is that the mix damper actuators are
aligned for correct rotation: very often the position of the dampers in the field do not reflect
the control output from the building management system (BMS). It is essential that these
systems are effectively commissioned and regularly inspected and tested.
•
The control theory behind a mixing section is that of a simple mixing ratio where the
combined percentages of the damper positions should roughly equate to 100%
o
If a fresh air damper is 20% open then the recirculation damper should be
approximately 80% open and the exhaust damper should be approximately 20%
open.
o
In effect 20% fresh air and 80% recirculation air equates to 100% total delivered air
and 80% re-circulated air and 20% exhaust air equates to 100% total exhaust air.
Typical operational issues with mixing sections
•
One or more of the dampers are seized
•
One or more of the actuators are malfunctioning or in need of repair/replacement
•
The damper position does not actually reflect the BMS control output desired position.
•
The damper ratios are incorrect due to incorrect installation, configuration or
commissioning.
Operational and Maintenance guidelines for mixing dampers;
29
•
Ensure that the linkage ratios are correct for all control outputs.
•
Initiate a planned maintenance regime of lubricating the damper linkage mechanisms.
•
Periodically perform an AHU inspection to ensure that the ‘field’ damper positions correlate
to the BMS output.
•
Periodically clean down the damper chamber to prevent dirt and debris from clogging the
damper mechanisms
4.2.2. Filtration
Filters within an AHU serve two main purposes:
•
To provide for the required air quality particulate required
•
To maintain the equipment and spaces in a clean state
Ensure that the filters perform as designed:
Ensure that the filters are installed in the correct orientation.
•
Installing filters incorrectly can cause them to become blocked prematurely in which case
they may need to be replaced due to unnecessary pressure drop. It is not at all unusual to
find filters installed incorrectly in commercial building AHU’s due to a lack of understanding/
training of operators and maintainers.
Filters can have a significant impact on the energy costs associated with an air handling unit.
Energy can account for 70% of the total life cycle cost of filters
The energy consumption is directly proportional to the average pressure drop over the
filter.
30
Figure 10: AHU Filter Life Cycle Cost 4
Key energy factors in the determination of energy cost associated with filters are:
•
Air flow-rate
•
Pressure drop
•
Operating hours per year.
The following equation allows pressure drop to be equated to energy costs.
Figure 11: Equation for calculating energy loss due to pressure drop
Filters should be replaced, in accordance with manufacturer’s recommendations, when
the maximum differential pressure is reached, where it becomes more economical to
change the filters than operate at a higher differential pressure. The accepted maximum
differential pressure at which it is recommended to change filters is twice the initial
differential pressure across the filter when initially installed.
There is a correct manner in installing both panel and bag filters within AHU’s.With correctly installed
panel filters, the pleat is in a vertical position, any larger particles trapped by the filter media can
potentially fall, under gravity, to the base of the filter thus prolonging filter life through reduced
differential pressure.
4
Camfil Farr Ireland ltd, Segment Brochure, Life Cycle Costs (LCC) Clean Air with Economic
Benefits
31
Figure 12: (Example) Follow manufacturer recommended Panel Filter Installation Orientation
For panel filters the correct method of installation is generally as follows;
•
Always refer to manufacturer’s recommendations for correct filter orientation and
installation.
o
Ensure filter is installed with pleats vertical to prevent sagging
o
Ensure filter is installed in correct orientation- direction of air flow.

Check filter edges for airflow direction markings, i.e. media should be
pressed against wire mesh by air flow
32
Figure 13: (Example) Recommended Bag Filter Installation
The correct method of selection and installation for bag filters is as follows;
•
Ensure pockets of bag filters are vertical, as can be seen in Figure 13 above
o
To ensure air flow will inflate pockets fully, and therefore utilise all of the potential
media area.
•
Consider a bag with the largest area (m2) of filter media possible.
o
The larger the area the less differential pressure drop across the filter for a given
particulate load, longer life potential, reduced maintenance.
Always refer to manufacturer’s technical literature for correct filter specification when
selecting the most appropriate filter for the application, bearing in mind potential loading
and required airflow
33
Figure 14: Recommended Type of Bag Filter
The tapered bag filter, as shown in Figure 14 for example, produces a lower pressure
•
differential across the filter when compared to the parallel pocket filter.
Filter manufacturers state that a 1Pa pressure increase across a filter can add €1.00 to the
Life Cycle Cost (LCC) for every filter, at an energy input cost of 0.010€/kWh.
Initial selection of filters in the first instance, despite the higher first time cost, can if operated
•
correctly lead to a lower Life Cycle Cost overall when accounting for higher filter capacity
and reduced maintenance requirements.
Consideration must be given to the correct choice of filter
•
Minimise differential pressure
•
Meet the required particulate levels in the space over the installed life of the filter
•
Minimise electrical energy consumption
•
Increase potential installed filter life
4.2.3. Heating and Cooling Coils
Ensure that heating and cooling coils are monitored and cleaned if necessary
34
•
The heating and cooling coils in an AHU are relatively maintenance free, with the exception
of ensuring that they are periodically inspected, monitored and cleaned if necessary on both
the water side and air side of the coil.
Ensure that heating and cooling coil valves are monitored and functionally tested on a
regular basis
•
If the valves are not maintained, control accuracy can drift, where for example the BMS could
be commanding a valve closed, the valve may be partially open in the field.
o
Not only does this incur an excessive energy demand but for AHU’s with both
heating and cooling coils this anomaly can incur unnecessary heating and cooling
demands.
•
In some design cases, depending on geographical location and AHU construction, the
heating coil may be the first unit of operation of the AHU.
o
This is typically a design feature for locations that are prone to freezing fogs where
the air is pre-heated to prevent filters becoming clogged with ice particles.
o
In situations like this the coil could in effect also act as a filter where in time it is
more prone to become blocked with dust, dirt and debris than a coil which is
installed after a pre-screening filter. (a pre-screen filter is also referred to as a
flyscreen at times)
Air-side coil blockage does not necessarily cause an increase in electricity use
When a coil becomes blocked the differential pressure across the coil increases, where
for constant volume units, a VSD has to ramp up to overcome the additional pressure,
and incur additional energy by the fan motor.
For fixed speed applications, air flow can be dramatically reduced due to filter blockage
and although this incurs less energy, a point may be reached where potential issues
could arise such as rooms overheating, under cooling, depleted / stale air and
associated stuffy conditions etc.
35
Figure 15: AHU heating coil showing blockage (Partially Cleaned) due to dirt and debris
Figure 15 shows a heating coil which had become blocked. The differential pressure across the coil
had risen from a design clean reference value of 30Pa to 320Pa in operation. This example was a large
constant volume AHU and the cleaning of the coil resulted in an electrical power reduction of 8kW
after cleaning and an approximate financial saving of €8,500 per year. It took two operators one day
to perform the cleaning task. The payback was immediate.
In order for heating and cooling coils to perform efficiently, regular operational and
maintenance controls should be considered
•
Establish a planned maintenance schedule for inspecting the coil surfaces and clean as
required.
•
Perform a functionality check on the coil valves to ensure that the valve position reflects the
BMS output signal.
•
Perform a functionality check on the coil valves to verify complete shutoff when
commanded closed by the BMS
o
A leaking heating / cooling valve may be highlighted by a differential temperature
gain / loss respectively in the air stream when the valve is indicated to be closed.
•
Consider active condition monitoring and alarm to the BMS for the air-side differential
pressure across the coil for applications as discussed above.
36
4.2.4. Fan and Motor
Ensure that belts and pulleys are installed in accordance with manufacturer’s
recommendations
•
Most AHU fans are driven by wedge belts, commonly known as V-belts, coupled to the
motor via a pulley arrangement.
•
Fixed speed fans have a pulley ratio engineered to achieve the required air flow and pulleys
are sized to determine the speed of the fan to deliver the required air volume.
•
All belts should be installed in accordance to the recommendations outlined, for example,
within BS 3790:2006: Specification for belt drives, V-Belts, and their corresponding pulleys.
•
Consultation with belt vendors on transmission belt efficiencies, all vendors stipulated that
regardless of the belt type installed, that if the correct installation methods are not adhered
to, that all belt types will not perform correctly.
•
They also emphasised the importance of correct belt tension and the adverse effects
associated with inadequate maintenance.
o
Not only is correct tension critical in reducing slippage and associated energy
increase, but also to prevent premature wear of the belts and pulleys. The wedging
action of correct V-Belt tension increases the force of the belt against the pulley
groove which helps prevent slippage and increases torque, subject to manufacturer
limits.
Figure 16: Relationship between belt tensioning and fan performance
•
Figure 16 illustrates the potential adverse effects associated with installing a belt in which
the belt tension is not correct.
•
Another factor to be considered in improving belt efficiency is belt alignment
37
o
A correctly aligned (and tensioned) belt drive means less friction and vibration is
generated by the drive system, which means less wear on belts, belt pulleys,
bearings and seals. This means the running time and reliability of the plant is
increased, energy and operating costs are kept to a minimum and overall plant
efficiency is improved.
Some manufacturers quote efficiencies that can be made from the use of toothed belts that eliminate
the potential for slip. There is potential doe savings with this type of transmission but these belts
typically cause a higher noise to be generated within the AHU and can cause difficulties at start up.
In order for transmission systems to perform efficiently, regular operational and
maintenance controls should be considered
To achieve an efficient drive the following regular planned maintenance program is recommended:
•
Schedule for greasing bearings on fan shaft bearing housings
•
Align transmission belts in accordance with manufacturer’s specifications.
•
Tension belts in accordance with manufacturers specifications.
•
Check the condition of the transmission pulleys and replace once the sheave of the belt
indicates heat fatigue and when the belt does not sit properly on the pulley sheave.
•
Check motor and fan mountings to ensure that there is no adverse movement which could
induce vibration.
•
Carry out regular power consumption reviews and assess trends
4.2.5. Equipment Calibrations
An AHU can only operate as efficiently as the instruments that control and monitor key
system parameters will allow
•
A common fault observed with AHU controls is the incorrect location, or sensor type, at key
locations in an AHU.
o
For example, an incorrectly located frost stat on a frost heating coil could
unnecessarily enable the coil valve, where to counteract for excessive heat gains a
cooling coil is simultaneously enabled.
38
•
For effective control all sensors need to be located to ensure that they are in direct contact
with the forced air through an AHU and all sensors need to traverse the entire length of a coil
for accurate reading of the air temperature.
•
Additionally all room sensors should be mounted such that they are not adversely affected
by internal heat gains.
o
For example, space can be a premium in some canteens where chilled vending
machines are located at peripheral walls. Too often the room sensor is covered and
indicates a false room temperature due to the heat gain from the vending machine
condenser, which does not represent the actual room temperature. In this case, to
compensate, an AHU over cools the supply air to the room.
All instrumentation that has a direct bearing on the energy consumption of an AHU should
be calibrated to a defined time schedule. Establish the initial frequency in accordance with
manufacturers recommendation and adjust according to review.
•
Instrument accuracy can drift overtime resulting in unnecessary consumption. Instruments
like pressure transducers, relative humidity sensors, airflow transducers and pressure
switches are typically calibrated on an annual frequency.
•
Temperature transmitters tend to retain their accuracy for longer periods and as such are
typically calibrated on an 18 month basis.
The frequency of calibration should be reviewed of accuracy over time and adjusted
according to potential impact to energy consumption due to accuracy drift and the history
of drift identified.
•
All calibration data should be recorded in a dedicated instrument calibration review log. For
example, within the Computerised Maintenance Management System (CMMS) where trend
analysis can be used to identify problematic sensors may be appropriate to some
installations.
•
The data could also be used for frequency scheduling of key instruments effecting energy
consumption of an AHU.
In order for key control and reference instrumentation to perform efficiently, regular
calibration should be considered
To achieve efficient control the following maintenance procedures are recommended;
39
•
Survey all sensors and assess their effectiveness in their current locations and correct as
necessary. This may require replacement or relocation of a sensor inter alia.
o
Calibrate all pressure and humidity transmitters that have a direct bearing on the
energy consumption of an AHU to a twelve month cycle, at a minimum.
o
Calibrate all temperature transmitters that have a direct bearing on the energy
consumption of an AHU to an eighteen month cycle, at a minimum.
o
Check the accuracy of valves and actuators and when control anomalies are
identified perform a calibration and span adjustment of the valve positioner.
4.2.6. Building Management Systems (BMS)
The Building Management System (BMS) , is typically a centralised control and monitoring network
to control the buildings plant and equipment such as AHU’s, chillers, boilers and lighting circuits etc.
Like all control systems the operational efficiency can deteriorate if ignored for prolonged periods. it
is prudent to regularly monitor these systems for ongoing effectiveness.
It is recommended that a competent person be assigned the task of reviewing the BMS systems data,
at appropriate intervals, to identify operational anomalies. In doing this at regular intervals systems
anomalies can be addressed and unnecessary energy use and costs reduced..
4.2.7. Air Changes per Hour (ACPH)
ACPH: The movement of a volume of air in a given period of time; if a space has say ten air changes
per hour, it means that the air in the space will be displaced ten times in a one-hour period.
Typically, the higher the ACPH the more air that has to be treated and thus incur a higher energy
demand than may be necessary. To calculate the ACPH of a room the total volume of air supplied to
the room (m3/hr) is typically divided by the volume of the room (m3).
Historically ACPH are excessive to actual requirements and savings can be achieved by reducing the
ACPH to met specification, whilst adhering to recommended guidelines.
A reduction in ACPH rates will typically produce a proportional step reduction in energy
costs of heating and cooling, and more significantly, fan motive power reduction
(Centrifugal Fan), in accordance with the fan affinity laws*
40
Flow and speed
The flow of air through a centrifugal fan will be proportional to the speed of the fan,
provided all other parameters remain constant.
Pressure and speed
The pressure developed across a centrifugal fan unit will be proportional to the square
of the speed of the fan (ie to the square of the flow)
Power and speed
The power consumption of a centrifugal fan will be proportional to the cube of the fan
speed (ie the cube of the air flow)
4.2.8. HVAC Three Port Valves
If the divert flow of 3 port secondary system was eliminated, it is estimated that 60-70%
pumping savings could be achieved.
•
To ensure immediate availability of hot water at AHU coils, LPHW systems were traditionally
designed using three port valves.
o
Three port valve design is such that if an end user, such as a AHU heating coil, did
not require heating at total design flow, flow would be diverted through the divert
port of the valve.
o
In essence these systems are constant volume systems because regardless of end
user requirements the total flow in the systems consists of a ratio of process flow
and divert flow. The problem that this poses, as far as energy consumption is
concerned, is that to pump this volume of water around a system excess energy is
consumed in the process.
•
The most efficient way of delivering hot water to end users is to use two port valves and a
Variable Speed Drive (VSD) with a control reference from a supply and return header
differential pressure transducer.
o
The system would operate to maintain a set pressure, based on flow, where the VSD
would modulate to maintain the desired system pressure.
o
The added benefit that such a system can offer is that the absorbed power of the
pump would correlate to end user demands.
Converting from 3 port to 2 port
41
•
It is sometimes possible to convert a three port system to a two port system by closing the
divert port on the valves.
o
Caution; Depending on the valve trim characteristics and the actuator torque
characteristics some valves may not be able to ensure complete shutoff. It is highly
recommended that if this opportunity is being considered that the valve
manufacturer is consulted and/or a trial be conducted to determine how the
installed valves respond to two port configuration.
o
To determine if retrofitting a VSD is merited the operational load and run hours of
the pump need to be determined.
o
The installation of a VSD may not be feasible in certain circumstances as the net
savings may be off-set by the capital cost required to retrofit a VSD.
o
A case by case study should be completed to determine how applicable this
opportunity is for end user as it will affect flow balances within the system.
o
For large systems with multiple valves, complex controls may be required to retain
control of the system pressures at all necessary points in the system.
4.2.9. Split Condensing Units.
Split-type air-conditioners are used extensively in residential and office buildings and often have the
outdoor condensing units installed at the sidewalls or on the roofs. The evaporator unit is typically
fitted into the ceiling of the room to be cooled, whilst the condenser unit is situated outside the
building. The two are typically connected using copper pipe. Most units currently installed are dual
purpose units which can either heat or cool, depending on setpoint and ambient conditions.
Figure 17: Internal ceiling mounted cassette unit
42
Figure 18: Roof top condensing unit (Incorporating Condenser Fan)
To ensure that these units operate efficiently it’s important that the following operational
and maintenance procedures are considered.
•
Incorporate temperature dead bands where the system would heat at 19°C and cool at
23°C for example, to prevent cycling loads /simultaneous heating and cooling
•
Incorporate a time scheduler because more often units remain operational in unoccupied
rooms. If time schedule functionality is not in place, security, caretakers, etc, should be
encouraged to turn off all operational units encountered during out of office hours during
their rounds.
•
Consider installing new technology
Today's best air conditioners use 30%–50% less energy to produce the same amount
of cooling as air conditioners made in the mid 1970s. Even if your air conditioner is
only 10 years old, you may save 20%–40% of your cooling energy costs by replacing
it with a newer, more efficient model. Check with your supplier and service provider.
•
Proper sizing and installation are key elements in determining air conditioner efficiency.
o
An over sized unit will operate inefficiently.
o
An under sized unit may not be able to achieve a comfortable temperature on the
hottest days.
43
•
If you are replacing an older or failed split system, be sure that the evaporator coil is
replaced with a new one that exactly matches the condenser coil in the new condensing
unit. (The air conditioner's efficiency will not likely improve if the existing evaporator coil is
left in place; in fact, the old coil could cause the new compressor to fail prematurely.
•
Place the condensing unit in a shady spot, this can typically reduce your air conditioning
costs by 1%–2%.
•
Locate the control sensors away from direct heat sources, such as windows or adjacent to
internal heat sources. In some cases an averaging temperature may be more appropriate
based on a temperature of a number of units.
•
Perform regular checks, e.g. change/ clean filters accordingly.
If multiple cassette type units are installed within a space, ensure that he controls are
such that individual units do not “compete with one another to control the air
temperature in the space but work to assist one another.
4.2.10.
Data Server Rooms
On account of high heat emissions from data servers, the cooling system infrastructure can be a
significant part of the overall energy consumption of a data centre. Cooling system components such
as chillers, computer room air conditioning units (CRAC), direct expansion air handler (DX) units,
pumps, and cooling towers are installed to achieve the optimum computing environment to reduce
server downtime and increase life.
Up to 40% of the total data centre electrical energy is consumed in cooling requirements
alone.
•
If once through AHU’s were used to dissipate the internal heat gains, the system would
require sizable ducts and AHU’s requiring significant capital expenditure.
o
It would not suffice to use 100% fresh air AHU’s, which could afford free cooling, as
there is an additional requirement to maintain the server room within an acceptable
Relative Humidity (RH) band. This configuration would prove expensive to operate,
not only in motive power but also in increased dehumidification costs. There may
also be a concern with noise attenuation due to the volume of air required through
the ducts.
44
Table 5: ASHRAE Guidelines on Temperature and Humidity Bands for Data Centre’s
Standard practice is for a fresh air AHU to maintain the humidity band and account for leakage rates
due to room pressurisation where CRAC units operate to dissipate the internal heat gains. Leakage
rates should be kept to a minimum in both the AHU and server rooms.
4.2.11.
Computer Room Air Conditioners (CRAC)
CRAC units are located at the perimeter of the room where they extract air at ceiling level and deliver
the conditioned air beneath a suspended floor (Plenum) of the room. Perforated floor tiles are located
at key locations within the room which facilitate the diffusion of chilled air from floor to ceiling level
where upon absorbing heat from the servers the air is drawn back into the CRAC thus continuing the
cycle. The air change rates (ACPH) required for maintaining the room at optimum temperature is
handled by the operation of these CRAC.
In order to improve the efficiency of the dissipation of the heat gains, many designs have
been devised to improve the configuration of air diffusers through the layout of the racks
into what has commonly become known as ‘hot aisle’ - ‘cold aisle’. Specialist advice
should be sought to assess alternatives for the energy efficient cooling of data centres
•
This principle facilitates reasonably good air management and prevents early mixing of cold
air with room air before entering the racks.
•
In order to achieve an efficient mode of operation the suction (Air Intake) of the CRAC units
needs to be taken from the hot aisles.
•
The CRAC units are primarily a form of fan coil unit (FCU) which typically uses chilled water as
a medium for absorbing sensible heat from the air to be cooled.
•
Alternatively the chilling can be provided by a split ACU which uses a vapour compression
cycle to extract heat from the rack room and dissipate the heat externally at a unit
condenser.
45
•
Care should be taken to ensure that air flow through the data units and equipment is not
blocked in any way as this leads to room temperatures being maintained to unnecessary low
levels to allow the heat to be dissipated from equipment.
Maintenance Schedule for Air Distribution Systems
Description
Suggested
Maintenance
Frequency
Comments
Fill out daily Check all setpoints such as pressure and temperature for proper Daily
log
setting and function.
Overall
inspection
Inspect the unit to ensure it is operating in a “normal” condition Weekly
for vibration, noise, and odours. Verify gauges and thermometers
are reading within range. Inspect for leakage due to access doors
not being properly closed. Verify that any internal lighting is off.
Verify all safety guards are in place.
Inspect pulleys Inspect belt tension and alignment. Look for rubber shavings Weekly
and belts
under the pulleys.
Grease fan and Inspect visible grease for metal shavings, indicating a possible Semi-annually
motor bearings failing bearing. Wipe away all excess grease after greasing.
Inspect grease tubing if installed for integrity to make sure
grease is getting to the bearings. Check bearings for excessive
heat, noise, or vibration.
Fan casing
Check for cleanliness and proper tightness at all anchorage Semi-annually
points. Inspect isolators if installed for free movement. Inspect
flexible gaskets between the fan and casing or duct for integrity
issues such as misalignment or leakage.
Condensate
drains
Clean drain pan, flush with biocide and eliminate pockets of Semi-annually
standing water.
Dampers
Inspect damper actuator and linkage for proper operation by Annually
cycling fully opened to fully closed. Inspect blade gaskets if
present for integrity and flexibility. Replace if damaged.
Filters
Inspect filter rack for integrity. Inspect local pressure differential Annually
gauge, tubing, and pitot tubes for condition.
Coils
Inspect coil fins for physical damage, and comb out any bent fins. As-required by
Clean coils if significant dirt is present and hampering coil performance
performance.
Electrical
connections
Tighten any loose terminal connections.
Annually
Outdoor grilles Inspect and clean grilles at all exterior building penetrations
Annually
Sensors
Annually
Clean and calibrate sensors
Table 6: Example: Planned Maintenance Check-list for HVAC system and components
46
4.2.12.
HVAC - Further reference
Sustainable Energy Authority of Ireland (SEAI), has run a number of special working groups (SWG)
focussed on HVAC. Although primarily based on Industrial applications, the core knowledge gained
from these reviews is an excellent reference tool to all HVAC owners.
The output of these special working groups can be found at;
www.SEAI.ie/Your_Business/Energy_Agreements/Special_Working_Groups
Energy Issue
Simultaneou
s heating and
cooling
Description
Wasted
of
Energy
Air heated unnecessarily and
cooled unnecessarily leading
to excessive cost of heating
and cooling
Common
Occurrence
Cause
for
Passing valves
Incorrectly commissioned
valves
Actuators on mixing section
stuck
Incorrect sensors used
BMS incorrectly programmed
Incorrectly aligned belts and
Excessive
loading of
fan motor
Motor load increased to
compensate for inefficient
apparatus
pulleys, poor belt tension, worn
belts, Filters, Air-side coil faces
blocked with dust, dirt, and
debris5
Excessive
ACPH
Undue amount of air required
to be treated
Systems oversized for actual
requirements, no account
taken for diversity
Corrective action
Ensure mixing
section dampers
are free to rotate,
calibrate valves
accordingly and
investigate
control
anomalies with
BMS systems.
Ensure belts and
pulleys are
aligned,
tensioned and in
good condition.
Ensure filters are
in a good
condition and
checked/replace
d as required.
Ensure coil faces
are clean and free
from debris
Challenge
current ACPH and
amend to actual
user
requirements
5 A reduction in airflow through blocked filters and coils in constant volume AHU’s will incur a
load increase by the fan motor VSD to compensate. In fixed volume AHU’s the corresponding
blockages would incur a load decrease in motive energy.
47
Table 7: HVAC - Typical Energy factors and corrective actions
For further detailed guidance on HVAC and other significant energy processes, refer to CIBSE
guidance documents
48
4.3. Lighting
Lighting technology has seen significant improvements in both luminaire and lamp
construction. With the advancement in compact fluorescent luminaires (CFL’s) and
fluorescent technologies, which are predominantly used in the commercial sector,
significant operational and maintenance savings can be achieved for a reasonable
investment
•
The new family of fluorescent lamps (T5):
o
•
Provide savings through lower absorbed power and more lumens per watt
They are commercially available for integration to occupancy sensing and dimmable control
lighting systems.
Retrofitting existing luminaires to more energy efficient models, while incorporating
occupancy sensing and active switching controls, can provide companies with operational
savings of up to 70% in lighting energy requirements.
High bay lighting can be a Significant Energy User for certain categories in the sector where for
example, High Intensity Discharge (HID) luminaires are used for warehouse and exterior lighting
locations.
Due to advancements in the construction of T5 high bay fluorescent luminaires and
CFL spotlights, companies can now retrofit their existing luminaires to more efficient
units, and they can also incorporate occupancy detection measures at the same time.
Improvements in operational and maintenance procedures can produce significant savings.
Although some of the recommendations will incur capital expenditure the energy reduction
associated with these upgrades warrant the investment involved.
The potential energy saving from converting T12 to T8 luminaires can be as much as 50%
•
Table 8 below indicates the potential operational savings from converting conventional T12
and T8 luminaires to the latest family of T5 luminaires.
49
•
Incorporating active switching controls will produce additional savings.
Standard T8/T12 FTL
and Fixture
Type of T8 FTL , including
rated power and
electromagnetic ballast
Type of T5 High
Efficiency FTL with
electronic ballast
Power
Saved
(Watts)
%
Energy
Saved
2 feet T8 (590mm)
18W
27W
14W
16.5W
10.5W
38%
2 feet T12 (590mm)
20W
30W
14W
16.5W
13.5W
45%
4 feet T8 (1200mm)
36W
46W
28W
30W
16W
34%
4 feet T12 (1200mm)
40W
49W
28W
30W
19W
38%
5 feet T8 (1500mm)
58W
72W
35W
39W
33W
45%
5 feet T12 (1500mm)
65W
78W
35W
39W
39W
Table 8: Fluorescent lamp comparisons (Watts and Energy Savings)
50%
When referring to fluorescent lighting they are generally referred to as T12, T8, and T5. The number
given after the T refers to the diameter of the tube in eights of an inch, thus a T8 lanp has a diameter
of one inch (25.4mm). This allows easy visual identification of the lamp fitted.
4.3.1. T5 Fluorescent lamps
The T8 lamp is slowly being replaced with the newer T5 family of luminaires. The “T” designation in a
fluorescent lamp nomenclature stands for tubular, the shape of the lamp. The number immediately
following the T indicates the diameter of the lamp in eights of an inch. A T8 lamp has a diameter of
eight-eights of an inch whilst the T5 lamp for example, has a diameter of five eights of an inch.
High Output fluorescents offer the potential for reduced capital, installation, operation and
maintenance cost.
•
While the standard T5 and T5 High Output (HO) are the same diameter and length, the 4-ft
T5 for example is rated at 2,900 lumens whereas 4-ft T5 HO lamp is rated as high as 5,000
lumens: twice the maintained light output of a T8 lamp.
•
This means that, depending on the retrofit application, fewer fluorescent fixtures or lamps
need to be used to maintain the same light level, thus providing potential savings on
installation and long-term maintenance requirements.
4.3.2. Magnetic Ballasts
Where feasible, due to equipment failure, magnetic ballasts should be retrofitted to
electronic ballasts
50
Fluorescent lamps historically were commonly supplied with 'glow-starters'. Glow-starters, although
inexpensive, do not allow for the efficient starting of fluorescent tubes and are characterized by
flickering on start-up and when the tube or other lamp components are beginning to fail.
•
The inefficient starting process of glow-starters significantly shortens the potential life of the
tube, often seen by the blackening of the tube ends from deposits of the cathode filament as
illustrated in Error! Reference source not found.
•
Where feasible, due to equipment failure, magnetic ballasts should be retrofitted to
electronic ballasts
Figure 19: Fluorescent Lamps indicating Blackened Rings (End of Useful Life)
4.3.3. Electronic Ballasts
Fluorescent lamps with electronic ballasts consume 25% – 30% less energy than
conventional magnetic ballasts. At the same time the average life of the lamps is extended
by more than 50%.
Further potential benefits of electronic ballast versus magnetic ballast
•
Less mercury and other waste products are generated.
•
The total volume of lamp waste is reduced by about 30%.
•
The amount of hazardous waste for disposal in industrial, commercial or public facilities, or
for recycling, correspondingly decreases.
Electronic ballasts have many advantages over magnetic ballasts
51
Electronic ballasts are better than magnetic ballasts in three significant areas:
•
Electronic ballast functions about 22% more efficiently than a conventional ballast.
•
Fluorescent lamp requires less energy, as it is not switched off at every zero-crossing of the
AC voltage and apart from an energy saving, the life of the lamp increases by more than
50%.
•
Due to the electronic ballast mode of operation, the interval at which lamps are replaced
may be extended from approximately 2 to 4 years.
It is possible to retrofit flourescents of one generation lamp to another.
T8 tubes can replace T12 -no additional modifications required – (Magnetic ballast)
T8 tubes fitted to a fitting with a magnetic ballast can have the ballast replaced with an electronic
(high frequency) ballast to yield savings. This has the added advantage of removing the starter from
the circuit which also yields maintenance savings by removing this mode of failure.
T8 lamps with either a magnetic or electronic ballast can be converted to a T5 fitting by the
replacement of the tube and utilising a proprietry conversion kit.
Note. The light from a T5 lamp is more intense than that from other flourescent lamps and can lead
to issues with glare. It is prudent to only retrofit a small number of lamps in an area iniitally in a trial
to assess potential glare issues before investing in relamping whole areas.
4.3.4. High Bay Lighting
Many of the commercial sector businesses have storage and warehouse space. Traditionally these
areas were served by High Intensity Discharge (HID) luminaires, predominantly metal halide. The
biggest factor against the use of controlled switching with HID luminaires is with the restrike time
needed for the lamp to achieve full light output. The lamps tend to be rated at 250/400 watts with a
ballast load of 60 watts.
The latest family of T5 High Output (HO) luminaires are designed as direct replacement to
HID luminaires, where the total energy requirement is 50% of a corresponding HID
luminaire
•
The latest family of T5 High Output (HO) luminaires are designed as direct replacement to
HID luminaires, where the total energy requirement is 50% of a corresponding HID luminaire
•
With active control the savings could be in the region of 75%.
•
Additional benefits include:
o
Increased life expectancy
52
o
Improved quality light output
o
Reduced maintenance costs.
o
Instant strike and restrike
Fixture Comparison
HP8-6-6 Lamp
400 Watt HID
Initial Lumens
19,000
36,000
5%
30-50%
Avg. Fixture Efficiency
98%
75%
Maintained Lumens
18,200
18,900
Energy Consumed
210 Watts
460 Watts
Maintained Lumens/Watt
84
40.6
Lamp Lumen Depreciation
Table 9: Comparison Table of Fluorescent vs. HID High-bay lighting
T5 fluorescents have significant operational and maintenance benefits over the equivalent
HID
•
Less light output (lumen) depreciation over the life of the luminaire
•
Higher fixture efficiency
•
50% reduction in power whilst maintaining light outputs
•
The capability to implement occupancy control measures due to instant strike
•
Increased lamp life
Latest long life T5’s are being manufactured for 60,000hrs - Significant reduction in
maintenance costs over HID lamps which have a mean life expectancy of 1000 hours
Alternatively induction light luminaires can be used which provide for the same control
features as the T5 fluorescents. These luminaires consume the equivalent energy as
T5HO for the same light output and have a life expectancy of 80,000hrs.
53
4.3.5. Lighting Control Mechanisms
Lighting control systems can greatly influence the energy demands of a lighting
installation, potentially reducing energy consumption by up to 40%.
Control systems vary from the simple manual switch, through to sophisticated occupancy detection
and daylight linked controls systems
The factors influencing the specification of controls include:
•
Occupancy
•
Occupancy pattern
•
Daylight availability
•
Type of lighting (e.g. can it be dimmed) the desired level of control sophistication and costs.
•
Variability of occupancy
•
Nature of the area
The specification of control strategy and system performance can be a technically demanding task.
The principle means of controlling lighting availability are;
•
Manual switching;
o
The simplest and most basic control for most lighting installations is the manual
switch.
o
The lack of switching in appropriate locations and poor occupant control can lead
to unnecessary lighting.
•
Manual dimming;
o
An alternative to the manual switch is manual dimming, which allows users to
regulate the voltage to the lamp, thus reducing the power consumed.
o
Dimming encourages more efficient use of the lighting, but unless used correctly
has the same disadvantages as manual switching.
•
Timed delayed switching;
o
Similar to manual switching in that the user switches on the lighting but the lighting
switches out after a predetermined interval incorporated in the timing device.
o
Most suitable for open areas or small rooms with short periods of occupancy
54
•
Timed switching;
o
Time controls can be provided in addition to manual switching or dimming,
allowing greater control over the operating hours of the lighting installation.
o
This is an economical solution, effectively helping to save energy used for lighting.
o
This may not be the best solution because occupancy pattern and hours may be
variable. Also, this type of control is not suitable for maximising the use of daylight.
•
Presence/absence detection;
o
Detection of an occupant’s presence or absence from a space can again be used in
conjunction with other control strategies.
o
Occupancy detection is particularly effective in partially occupied spaces such as a
library, toilets, corridors, warehouses or offices.
o
Occupancy detection in open plan spaces can result in nuisance switching and
complaints from office users, but should still be considered.
o
There are a number of types of occupancy detectors available with different modes
of operation including Passive Infra Red (PIR), Ultrasonic, and active types. Dual
mode technologies are also available.
•
Photoelectric control – daylight linking;
o
One of the most effective methods of achieving maximum energy saving is through
photoelectric, daylight linked control.
o
This can take several forms but generally relates to the monitoring of either external
daylight level or internal daylight entering a space.
o
In conjunction with luminaire switching or more preferably dimming, the internal
luminance is controlled to maximise the use of daylight.
o
The two main controls strategies for photoelectric control are on/off switching and
dimming.
55
Figure 20: Dimmable fluorescent daylight linking control
Figure 20 illustrates the concept of daylight linking control. Subject to the availability of natural light,
the luminaire outputs are automatically varied, such that a predetermined lux level is maintained
throughout the room at the most appropriate and least energy use level of the individual lamps.
4.3.6. Group Re-lamping
•
More often lamps are allowed to expire where call outs for lamp replacement are based
upon diminished light levels or due to a failed light.
•
These call outs incur man hours to repair, besides the disruption to the area on replacing
worn lamps.
•
Additionally lamp stock has to be maintained to facilitate these works and excessive time is
spent on both retrieving and disposing of lamps.
Group re-lamping has proved successful in minimizing maintenance costs
Group re-lamping has proved successful in minimizing maintenance costs for the following
reasons:
•
Labour costs are lower when group re-lamping policies are implemented as opposed to
individual lamp replacements, through increased labour effectiveness.
•
Increased light output, ensuring higher potential for light levels being maintained at
optimum levels.
•
Reduced un-planned burnouts, again light levels maintained at optimum levels.
•
Less lamp stocking, group re-lamping involves performing lamp change outs at
predetermined times; this will save on stock retention as stock is sourced for the duration of
the change out.
•
Fewer work interruptions, in an office environment replacing worn lamps can incur
disruption to desk based employees. This should result not only in the cost associated with
replacing the lamps but the lost time to desk staff on facilitating the change out. If a group
re-lamping policy was put in place the change out could occur during out of office hours
with minimum disruption to office staff.
56
4.3.7. Average Rated life and lumen Output
Average rated life of a fluorescent lamp is the median value of life expectancy of a group
of lamps.
•
T8 economy tubes have a rated life expectancy of 8,000-20,000hrs depending on the lamp.
To get the stated life expectancy from a long life rated tube, the lamp ballast must typically
be matched to the tube.
•
T5 lamps have a rated life expectancy of 20,000-60,000hrs in which the colour output from
the lamps can drop to 90-95% output at its rated life.
Figure 21: Lamp Type Rated Light output
The significant benefit of a group re-lamping program, from maintenance perspective, is
that purchasing the high life lamps saves most significantly on the lamp replacement
labour costs and that light output levels are not diminished throughout the rated life of the
lamp.
4.3.8. Exterior Lighting
The new technology external luminaires are rated with a life expectancy of 60,00080,000hrs, versus the 10,000hrs rated life for a low pressure sodium lamp.
•
Exterior lighting is another area that has seen significant advancements in luminaire
construction.
•
Traditionally low pressure sodium lamps were used where the power absorbed per lamp
ranged from 80-250 Watts.
57
•
With the advancements in LED technology, a new family of luminaires are available that can
provide better lighting conditions at a fraction of the absorbed power.
•
Maintenance costs to replace worn lamps is therefore significantly reduced
4.3.9. Daylight Harvesting
Many personnel, when queried why artificial lighting is used during daylight hours, indicate that the
use of artificial lighting is warranted because of the unwanted effect of solar glare and the resultant
closure of blinds.
Daylight blinds reduce glare and allow daylight to enter the space in a controlled way,
instead of the more common standard horizontal or vertical blinds, which cut out the light
to the working space when they are drawn to alleviate glare or excessive sunlight.
•
There may be little need to use artificial lighting during normal office working hours,
especially during sunny periods, if daylight blinds are installed.
•
They are a great energy saving retrofit option.
The following series of figures indicates how the daylight blinds typically operate.
Figure 22: Daylight blinds prevent Excessive Solar Glare Reflection
•
The lower part of the daylight optimized Venetian blind provides for a dazzle-free
workstation. The upper slats reflect the sunlight against the ceiling and illuminate the room
evenly, ref. Figure 22
58
Figure 23: Daylight Blinds Room Illumination during bright sunny days
•
If the sky is overcast or clear without direct sunlight, the slat is folded up.
•
In this way, the entire slat surface is available to guide the daylight.
•
The daylight-optimised Venetian blind with concave mirror slats provides for illumination of
the depths of the room. The principle of operation of the blinds can be seen in Figure 23
Figure 24: Daylight Blinds operation during dull exterior weather conditions.
•
During sunny days when the rooms would be prone to solar glare the operation of the
hinged slats reflect the direct sunlight, thus preventing glare.
59
Figure 25: Daylight Blinds operation during times of extreme solar glare.
•
If daylight blinds are installed, it is important that all personnel are fully aware on how to
operate the blinds effectively to minimise the need for artificial lighting.
•
For areas where daylight blinds are recommended it would not make economical sense to
retrofit the existing luminaries simultaneously.
•
It is therefore recommended that dedicated task lighting at PC’s should be utilised,
incorporating compact fluorescent lamps (CFL). It is believed that the lighting levels
provided by such lamps would meet the needs of individual user requirements once
sufficient natural daylight is available to traverse the room unimpeded.
4.3.10.
Lighting Recommendations
To ensure that the lighting system is as efficient as possible it is recommended that the following
lighting systems operational and maintenance procedures are considered;
•
A group re-lamping policy
•
When lamps are being replaced that diffusers are dusted down and cleaned.
•
Electronic ballasts are used instead of magnetic ballast for ballast failures
o
•
T5/T5HO lamps and luminaires used instead of T8 luminaires
o
•
Retrofit kits are commercially available.
Retrofit kits are commercially available to install T5 technology into T8 luminaires.
Implement a controlled switching regime
o
This does not necessarily mean automated changes but ensuring lights are
switched off when not required.
o
This could simply be a caretaker/security man switching off all lighting during
evening rounds.
•
Where feasible install occupancy detection for circuits where manual control is not effective.
•
Where feasible, avail of natural daylight and control glare issues through daylight blinds.
60
•
Once efficient maintenance and group re-lamping is put in place, look at isolating
luminaires, based on lighting requirements, because lighting systems are perhaps overdesigned to allow for future lux reduction.
•
Once the above procedures are effective look at potentially redesigning the lighting system
to reflect actual requirements. This could save energy through less luminaires being required
and for offices with suspended ceilings the luminaires can easily be removed to more
suitable locations.
When purchasing lighting that makes claims to high values of energy efficiency ensure
that the lamp make and model is registered under the Accelerated Capital Allowance
scheme funded by the Dept of finance with the list being maintained by SEAI. This
ensures that the lamp manufacturer can demonstrate that his lamp meets the highest
standards laid down for lighting by lighting experts and assures the user that the
technology promoted and used is fit for purpose.
Energy Issue
Unnecessary
lighting load
Artificial
lighting
used during
daylight
hours
Unnecessary
exterior
daytime
lighting
Description of Energy Wasted
Common Cause for Occurrence
Corrective action
Lighting active in unoccupied
areas for prolonged periods
Wall switches used, personnel
not actively switching off lights
upon exiting a room
Install occupancy
control sensors for
all areas that are
intermittently
used
Lights switched on during
daylight hours in office areas
with glass facades.
Poor building construction
resulting in sun glare, blinds
closed for providing for
comfortable
working
environment. Lights turned on
to increase internal light levels.
Look at office
layout
for
combating glare
effect. The use of
daylight blinds in
lieu of standard
suspended blinds.
Photo-optical switches faulty or
exterior lighting manually
switched
Repair
faulty
photo cells and
retrofit
manual
switching
arrangements to
automatic
switching
Exterior lights active during
daylight hours
Table 10: Lighting – Typical Energy factors and considerations for corrective action
61
4.3.11.
Lighting – Further reference
In response to sector demand, Sustainable Energy Authority of Ireland (SEAI) has
commissioned a series of studies and publications on lighting efficiency which are
referenced here.
These publications consider all key aspects of lighting efficiency from lamp type to effective controls.
It is highly recommended that the SEAI publications are read in conjunction with this report:
•
General Lighting; A guide to energy efficiency and cost effective lighting.
•
Offices; A guide to energy efficiency and cost effective lighting.
•
Retail; A guide to energy efficiency and cost effective lighting.
•
Lighting Controls; A guide to energy efficiency and cost effective lighting.
These publications can be sourced at the following link;
www.SEAI.ie/Publications/Your_Business_Publications
4.4. Cooling and Refrigeration
Water chiller package is a broad term describing an overall package that includes refrigeration plant,
water chiller and air or water cooled condenser. This name infers that the compressor, condenser,
chiller and internal piping and controls are combined into a single unit.
The main components of the typical refrigeration plant are:
•
Compressor
•
Condenser
•
Thermal expansion valve
•
Evaporator.
The effective selection and operational management of all key refrigeration plant
components are essential for the continuing efficiency of operation
Water chillers may range in size from small capacity reciprocating compressor units with air or watercooled condensers up to large units incorporating centrifugal or screw compressors.
Large water chillers are normally water cooled using the recirculated water from a cooling tower
although air-cooled condensers are now becoming more popular, particularly where there potential
occurrence of Legionnaires disease is a key concern
62
Central chilled water units are used in air-conditioning systems comprising air handling units each
fitted with chilled water coils. These air handling units can be either located in a central plant room or
distributed throughout the building.
The types of compressor used can vary according to the required capacity of the individual
units.
•
As a general reference: Chiller type versus system Load:
o
Reciprocating compressors are typically used for small to medium sized water
chillers
o
Medium to large capacity water chillers typically incorporate screw compressors
o
Very large units typically utilise centrifugal compressors.
To achieve efficient operation it is necessary that the water chiller be able to effectively
alter its refrigeration capacity as the cooling demand changes.
•
Consider Performance characteristics at the intermediate loads from low load to maximum
load
•
Selection of the type of water chiller must also take into account the minimum load at which
the chiller may be required to operate.
•
If turn down ratio is insufficient to meet the minimum cooling requirement of the building
with one machine then consider a modular design incorporating a number of machines
Information regarding the performance at varying operating conditions should be obtained
from the water chiller manufacturers and assessment of this data should form part of the
selection criteria for purchasing water chilling equipment and determining an appropriate
control strategy
As a general reference:
•
Reciprocating compressors can unload to between 12-15%
•
Screw compressors down to 10-15%
•
Centrifugal chillers down to 20-25%.
63
A 1°C reduction in Condenser Temperature Water temperature can reduce electrical
powerrequirements by 2 to 4%
•
For water condensing refrigeration equipment to achieve maximum energy efficiency, the
cooling tower water (CTW) system should operate at the lowest possible temperature.
N.B. Data from water chiller manufacturers should be obtained in order to determine the minimum
acceptable condenser water.
A 1°C increase in Chilled Water temperature setting can reduce electrical power
requirements by 2 to 4%
•
The chilled water temperature should be maintained as high as possible to reduce the
energy consumption of the compressor.
The temperature differentials across both the condenser and chiller heat exchangers
should be optimized to be as high as possible.
•
Ensuring that the temperature differential across the heat exchangers is as high as possible
will give the added benefit of reduced hydraulic power. Temperature differences between
the condenser water and the fluid that it rejects its heat to should be as low as possible.
Similar for the evaporator, the evaporating temperature of the gas should be as close as
possible to the desired chilled water temperature.
The maintenance program should ensure that heat transfer efficiency is maintained as high
as possible
•
Adequate water treatment should be provided in order to maintain the heat exchange
surfaces in a clean condition to achieve maximum heat transfer efficiency.
•
A program to monitor heat exchanger efficiency should be put in place.
•
Key measurement variables to regularly assess heat exchanger effectiveness include:
o
Flow-rate of secondary fluid in Heat Exchanger
o
Entering and Leaving Pressures
o
Entering and Leaving Temperatures
64
Monitor the Energy Performance of the Refrigeration plant and associated systems such
as the pumps and the cooling towers etc. as applicable.
•
N.B. The energy consumed in the support services is often higher than the energy used in
the refrigeration plant alone.
65
There are a number of refrigeration systems performance indicators which can be used to
monitor the effectiveness of the refrigeration system in isolation or more appropriately, the
energy performance of all the process components such as the tower fans, pumps etc.
Performance Indicators for Electric driven refrigeration compressor plant include
•
Co-efficient of Performance (COP):
o
Ratio of the electrical energy input to the refrigeration output

•
kW(output) per kW(Compressor electricity input)
Co-efficient of System Performance (COSP):
o
Ratio of the *total system electrical energy input to the total output

kW(output) per kW(Compressor + pumps + cooling towers input etc. as
applicable)
•
IPLV - Integrated Part Load Value:
o
IPLV is an abbreviation for Integrated Part Load Value.

This was developed by the Air-Conditioning and Refrigeration Institute and
measures the efficiency of air conditioners under a variety of conditions -that is, when the unit is operating at 25%, 50%, 75% and 100% of capacity
and at different temperatures. IPLV is only calculated for non-residential
central air conditioners
The different types of refrigeration plant have different Co-efficient of Performance (COP)
•
Typical values at full load operation for electricity driven refrigeration compressor
plant:
o
Reciprocating: 0.27 – 0.29 kWe/kWr
o
Centrifugal: 0.18 - 0.22 kWe/kWr
o
Screw: 0.18 - 0.22 kWe/kWr
Modular chiller design
66
A water chiller system which incorporates multiple compressors can provide good staging
in reduction of capacity.
Chilled Water System Control
With a single chilled water system operating, control is usually by means of an integrated unit
temperature controller installed on the chiller package/
Where multiple chillers are installed, it is essential that correct control be maintained in
order to achieve energy efficient operation.
•
Allowing multiple chilled water units to operate independently under the control of their own
equipment may result in extremely high energy costs.
•
The control reference for the staging in and out of compressors is essential to reliable and
efficient operation.
Staging of multiple chiller installations can be achieved by utilising an electronic control
system to calculate the actual cooling load on the building.
•
This load can be calculated by assessing the positions of each chilled water valve and using
this information to estimate the actual cooling load at any given time.
•
An alternative scheme is to measure the chilled water flow rate together with flow and
return temperatures and use this to calculate the cooling load.
o
Having calculated the cooling load it is then possible to stage the chilled water
equipment to achieve minimum energy consumption.
o
It is important that the load profile for each chiller be considered and that the
sequencing be carried out by operating the water chillers at their most efficient
operating point to achieve minimum energy consumption.
o
In this way, the water chilling unit which has the capacity closest to the actual
requirement can be energised to operate at peak efficiency.
Variable speed drives on centrifugal chilled water units will allow a more economic
operation of the equipment at lower capacity operation.
67
Figure 26: Example – Comparison of Co-efficient of Performance of a YORK VFD Centrifugal compressor
versus a fixed speed compressor6
Annual savings of a VSD over a fixed speed machine can typically average 30%
The refrigeration cycle in brief
Figure 27: Vapour Compression Cycle (Single Stage Refrigeration Cycle)
The capacity of a refrigerant to absorb heat energy is greatest when changing state from liquid to
vapour.
68
•
In the evaporator liquid refrigerant vaporises in order to absorb heat energy from the
chilled water.
•
The refrigerant vapour is then compressed through the chiller compressor and discharged
to the condenser which dissipates the heat gained to ‘atmosphere’.
•
A thermal expansion valve reduces the condenser pressure in order to reduce refrigerant
temperature.
•
From here the refrigerant enters the evaporator to begin the cycle again.
4.4.1. Refrigerant Charge
Too little refrigerant will result in a smaller part of the evaporator surface being used which
will cause a reduction in evaporation temperature and increase chiller power requirements.
•
A lack of refrigerant charge can sometimes be checked by fitting a sight glass on the liquid
line feeding the expansion or control valve.
•
Most large refrigeration systems have a sight glass where you can check for bubbles in the
refrigerant.
o
If bubbles are clearly visible it’s an indication that there’s a leak in the system.
o
All leaks should be repaired immediately by a competent person.
With reference to Figure 28 below the refrigerant level should be midway between the minimum and
maximum level, in the sight glass, and the refrigerant should be free of bubbles.
Figure 28: Refrigerant Sight Glass
69
4.4.2. Chilled Water Systems Thermal Expansion Valve
The purpose of the expansion valve is to reduce the pressure between the condenser and
the evaporator and to regulate the flow of refrigerant from the condenser to the evaporator
at a rate determined by the cooling load.
The ideal automatic expansion valve would maintain the following;
•
Control the flow of refrigerant to maintain a minimum excess level of superheat at the
evaporator outlet with a sufficient flow to ensure that all the refrigerant has been boiled
before it enters the compressor
•
Protect the compressor from liquid carry-over from the evaporator (Excess Flow)
•
For any load, allow the highest evaporation temperature and lowest condensing
temperature leading to the highest attainable COP and minimum energy consumption and
cost.
•
The thermal expansion valve (TEV) is an effective control device for set conditions but it has
its limitations in that it cannot efficiently accommodate significantly varying changes in
system conditions.
o
•
These changes include varying evaporating and condensing temperatures,
Electronic expansion valves have now replaced the thermostatic expansion valves which
uses electronic sensing (Temperature and Pressure) and microprocessor control which offers
greater controllability.
o
Electronic expansion valves offer greater cooling capacity for the same size
evaporator or allow smaller evaporators to be installed.
Figure 29: Electronic Expansion Valve Installation
70
4.4.3. Refrigeration Recommendations
A small change in operating setpoints can have a significant effect on operational costs.
To ensure that a refrigeration system operates as efficiently as possible consider the
following operational and maintenance energy factors
•
Operate the Condensor at as low a temperature as possible
o
•
1ºC reduction in condensing temperature will reduce costs by 2 to 4%.
Operate the evaporator at as high a temperature as possible
o
1ºC increase in evaporating temperature will reduce costs by 2 to 4%.
•
Ensure evaporators and condensers are kept clean.
•
Maintain auxiliary pumps and fans at optimum efficiency
o
•
Ensure that condensers are inspected and cleaned on a regular basis.
o
•
Poor control of auxiliaries can increase costs by 20% or more.
Fouling and blocking is a common problem with all condensers and evaporators
Both fans and pumps are significant energy users in refrigeration systems and their efficiency
will be reduced by a lack of maintenance.
o
Bearings should be monitored, lubrication procedures in place and faulty
equipment maintained/replaced as soon as an anomaly is discovered.
•
Establish routine leak detection checks.
o
Leaks are likely to occur at the following; valve stems (cap should be fitted and
tight), compressor mechanical seals, gaskets, pipe fittings (Fretted pipework), and
due to vibration.
•
Checks should be performed as applicable on;
o
Compressor oil levels
o
Suction and discharge pressures and temperatures.
o
The data should be trended to allow ongoing performance review.
71
Figure 30: Refrigeration Plant Energy factors 7
Energy Issue
Description of Energy Wasted
Common Cause for Occurrence
Poor
Value
The chiller is consuming
excess energy for the actual
cooling load requirements
Chiller oversized for system
requirements
Excessive energy is consumed
to achieve operational set
point
Potential lack of refrigerant,
non condensable (Air) in the
system
COP
Chiller
Operating
inefficiently
Corrective action
Revise
load
requirements and
consider
operating smaller,
loaded chiller
Investigate chiller
refrigerant charge
level, air bubbles
in sight glass,
repair leak and
charge
accordingly
Excessive energy is consumed
Soiled Condensor, Evaporator Clean
coils
to achieve operational set
coils
accordingly
point
Table 11: Refrigeration – Typical Operational Energy factors and corrective actions
Poor
performance
7
UK Carbon Trust
72
4.5. Compressed Air
Compressed air is used as a medium by many companies for doing mechanical work, but where
energy consumption is concerned it is one of the least effective conversion processes.
In the region of 90% of useful energy absorbed by an air compressor is given off as waste
heat. Some can be recovered and used.
Compressed Air, 4% Unrecoverable Heat, 8% Recoverable Heat, 90% Figure 31: Indication of breakdown of energy feed to an air compressor in terms of energy end dissapation
•
In some cases the waste heat from an air compressor can be used to provide a form of
heating for a building in the form of space heating via LPHW or for DHW requirements.
o
This requires some form of heat recovery mechanism and not all air compressors are
suited for this directly.
•
The energy used for compressed air generation in the commercial buildings sector varies
considerably from a simple stand alone compressor/receiver unit to a dedicated compressed
air generation and distribution network.
Compressed air is one of the most expensive conversion processes that companies can
operate. The reason is that typically only 10% of the power consumed in compressing air
results in useful energy whilst the remaining 90% is converted to waste heat.
73
Figure 32: Compressed air key maintenance locations (Simplified Overview)
To ensure that the compressed air system operates as efficiently as possible it’s important
that leaks are kept to a minimum and a regular maintenance regime is put in place.
4.5.1. Compressed Air Recommendations
To achieve the most efficient performance of the compressed air system, the following operational
and maintenance procedures are recommended
•
Operate the system at the lowest possible pressure
•
Keep main headers at the lowest practicable velocities: typically < 15m/s
•
Ensure a leak detection and repair program is in place
o
•
Check for leaks at a minimum six monthly basis initially
Have a lubrication regime including greasing, oil top-up and oil replacement, where
applicable.
•
Check and replace filters
•
Check the operation of valves
•
Check condensate traps and ensure that manually operated traps have not been left
open
•
Clean out dust/debris from the dryer cooler
•
Simple adjustments and improvements to compressor control can save on operational
costs.
o
•
Simply switching off an idling compressor can save 40% of its full load power.
Determine the minimum system head pressure and adjust the compressor accordingly.
o
Ask equipment and tool manufacturers to specify the minimum air pressure that
their equipment needs.
•
Consider installing an automatic pressure controller:
o
This will ensure you always have the most efficient air pressure setting.
74
•
It’s important to keep the system pressure drop below 0.2 barg if possible
o
Take a reading of the pressure at the compressor with a pressure gauge and then,
using the same gauge, take a measurement at the farthest point on the site. Large
pressure drops indicate that the air pipe is too small, which may require higher
operating pressure than necessary.
The table below indicates common issues, root causes, and recommendations to consider.
Energy Issue
Base load
Excessively
high
Description of Energy Wasted
The compressor is
consistently operating to
compensate for high base
loads
Common Cause for Occurrence
Corrective action
Compressed air leaks biggest
problem to contend with
Conduct periodic
leak surveys and
repair all leaks
Poor
Equipment
Control
Compressor has to
compensate for poor control
Compressing air creates
moisture, systems can become
waterlogged where
compressor hunts due to lack
of capacity in reservoir
Poor loading
capacity
Compressor excessively
operating for relatively small
load
Small air receiver capacity, or
poor distribution pipework
creating large pressure losses
Periodically blow
down receivers
and distribution
pipework, where
possible install
automatic blow
down traps.
Investigate
distribution pipe
capacities and
receiver capacity.
Table 12: Compressed Air – Typical Operational energy factors and corrective actions
4.5.2. Compressed Air Further reference guides
The following guides are available on the UK Carbon Trust web-site
www.carbontrust.co.uk
•
CTL050 Maintenance Checklist- Compressed Air
•
CTL051 How to recover heat from a compressed air system
•
CTL053 How to implement leak detection techniques in compressed air
•
CTV017 Compressed Air Technology Overview
•
GIL123 Energy Saving Fact Sheet Compressed Air
Sustainable Energy Authority Ireland (SEAI) under the energy agreements programme commissioned
an extensive study of industrial compressed air systems to identify opportunities for energy savings.
www.SEAI.ie/Your_Business/Energy_Agreements/Special_Working_Groups/compressed_air_SWG20
07/Compressed_Air_Technical_Guide.pdf
75
5.
Office Equipment
5.1. General Office equipment
It is estimated that energy costs for office equipment can be reduced by as much as 35%
by adopting energy efficiency measures (SEAI, Building Managers Energy Resource
Guide).
•
Office equipment typically includes computers, printers, photocopiers, fax machines and
vending machines.
o
It is considered that energy costs for these apparatus can be reduced by as much as
35% by adopting energy efficiency measures (SEAI, Building Managers Energy
Resource Guide).
•
The energy used by office equipment depends not only on equipment efficiency, but on the
number of employees working in the office, office occupancy, what equipment is being used
by each employee, and how they operate the equipment.
•
Simply educating office personnel on conservation measures can be the best tool for energy
management. For example, a general misconception is that screen savers also save energy.
o
Depending on the manufacturer, a screen save will save no energy at all, or in some
cases can actually increase consumption.
To ensure that office energy is conserved, the following considerations are recommended;
•
Turn off all desk top PC’s at end of business daily
o
A typical PC and monitor constantly on will cost €90 a year, adopting a switching
policy will reduce this cost to €20 a year.
•
Replace all cathode tube monitors with LCD screens
o
•
LCD screens use 50 to 70% less energy than cathode tube type
Turn equipment off as opposed to leaving in standby mode
o
Equipment in standby can consume as much as 20% of the energy consumed by the
equipment when in use.
•
Set the Power settings on your computer to automatically go into power save mode after 15
minutes or so of inactivity.
•
Use a laptop computer. They use less energy than desktops.
•
Use a power strip so you can automatically turn off all your computer accessories at once.
76
Figure 33: Average loads of Office Equipment with potential standby savings
5.2. Office Equipment (Computers)
Although computer manufacturers are developing their own range of products for improved energy
efficiency, the onus of conserving energy still rests with the individual user.
Leaving equipment in standby mode can result in up to 20% of the corresponding energy
used by the equipment when operational to be consumed.
Employees should be encouraged to turn off screens when they are absent from their
desks and to shut down the PC at the end of daily business.
Figure 34: Breakdown of Energy Consuming Equipment (Office Building)8
Depending on activity, a typical desktop PC can consume in the range of 60-250W
•
The biggest wastage affecting the sector is with inactive PC’s running when office areas are
unoccupied.
8
“Building Energy Managers Resource Guide” published by SEAI.
77
Idle PC’s can consume in the region of 95 W.
Table 13: PC - Energy factors
A good indication of how occupants affect energy use is to trend electrical consumption patterns of a
building against occupancy.
•
If it is seen that occupancy does not reflect power demands then it may be beneficial to put
an energy awareness program in place to inform individuals of the consequences of their
actions.
•
If energy awareness proves to be ineffective, automated means of isolating the power to
desktops automatically should be considered.
78
6.
Building Fabric
The term building fabric refers to the internal structure and external elements (roofs, walls and floors)
of the building. The quality of the building construction, particularly insulation levels and air leakage
rates, determine the heat loss rate and ultimately the energy required to maintain the building at a
comfortable working temperature.
The most appropriate method of addressing building fabric losses is at the initial design stage of the
construction process. Part L of building regulations indicates where improvements in the
construction process can be made to improve on building overall efficiency.
To assist established buildings to reduce energy demands we need to consider how companies can
address building fabric issues and ultimately minimise their energy costs.
It is recommended that the following measures be implemented, where feasible, to reduce
energy demands;
•
Reduction in air infiltration rates
o
Block all gaps in exterior fabric and internal ceilings.
•
Improvements to building insulation, where feasible improve on insulation levels.
•
Installation of double/triple glazing when window upgrades are required.
•
Improvement to draught-stripping, install draught proofing on all exterior openings, e.g.
doors and poorly constructed windows.
•
Installation of fast acting doors, thermal energy is required for maintaining internal spaces
at a comfortable temperature. Doors left open induce additional heating loads.
•
Installation of air curtains, air curtains should be installed on large exterior doors to
prevent external air entering the building during inclement weather conditions
•
Door closers
•
Draught lobbies, for large open foyers it would be beneficial for companies to investigate
the feasibility of constructing draught lobbies or review how efficient their lobby is in
preventing cold air entering into the building.
7.
Water Usage
Water consumption is often overlooked. Many sectors need to pay the cost of both purchased and
treated water discharge. Where possible, individuals should be encouraged to conserve water where
feasible. To assist companies the following water conservation measures are recommended;
•
Fit time activated or occupancy sensor solenoid valves to toilet urinals within men’s wash
rooms. In general toilets are unoccupied for prolonged periods during nights and weekends
where urinals continuously flush, thus wasting water.
•
Repair leaking/ dripping pipes and taps as soon as they occur.
79
•
Install water conservation devices like spray taps in wash facilities
•
Use water sparingly for washing facilities both in catering canteens and general domestic
cleaning.
80
8.
Operational and Maintenance Improvements
To quantify where both operational and maintenance savings can be achieved we need to discuss
the individual energy users where, if not maintained, how they can consume more energy. What
should be understood from the beginning is that with many of these energy users, one
malfunctioning process can have an adverse effect on another. For example, improving the efficiency
of an AHU could potentially provide operational savings with the HVAC chiller or LPHW boiler.
Although building commissioning is becoming more popular for new construction projects, many, if
not most buildings, have not undergone any type of systematic process to ensure they potentially
operate at best efficiency. Several studies have shown that existing commercial office buildings have
significant potential for increasing energy efficiency through low-cost O&M improvements.
O&M improvements can yield savings of 5 to 25% of a building’s annual utility bill. Simple
paybacks are generally less than 2 years
Understanding why building systems are operated and maintained the way they are,
where and what improvements are most beneficial and cost-effective, is the first step to
obtaining energy-efficient building performance. An O&M assessment provides a
systematic look at all aspects of the current O&M practices including the management
structure, policies, and user requirements that influence them.
An O&M assessment may include:
•
Interviews with management
•
O&M personnel
•
Service contractors
•
A review of equipment condition, building documentation and service contracts;
•
Spot tests of equipment and controls;
•
Trend or data logging of critical data points (temperatures, pressures, electrical, etc.) over
time.
•
The O&M assessment also checks schedules and control strategies to determine if the
building is operated optimally and develops a list of recommended improvements that
support energy-efficient operation.
•
It can provide a starting point or baseline from which to measure the effectiveness of
improvements and ongoing O&M activities.
81
•
Depending on the scope of work, an assessment may include recommendations for more
extensive improvements (such as air or water balancing) and capital improvements for the
owner to consider as well as motivational and behavioural issues that affect building
performance.
8.1. Operation & Maintenance Assessment
An O&M site assessment is a systematic method for identifying ways to optimize the
performance of an existing building.
•
It involves gathering, analysing, and presenting information based on the building owner or
manager’s requirements.
Owners generally perform an O&M assessment for the following reasons:
•
To identify low-cost O&M solutions for improving energy efficiency, comfort, and indoor air
quality (IAQ)
•
To reduce premature equipment failure
•
To insure optimal equipment performance
•
To obtain an understanding of current O&M and PM practices and O&M documentation
O&M assessments may be performed as follows:
•
As a stand-alone activity that results in a set of O&M recommendations
•
As part of retro-commissioning (a larger more holistic approach to improving existingbuilding performance).
The goal of the assessment is:
•
To gain an understanding of how building systems and equipment are currently operated
and maintained
•
Establish why these O&M strategies were chosen
•
Establish what the most significant problems are for building staff and occupants.
Implementing O&M changes without fully understanding the owner’s operational needs can
have disappointing and even disastrous effects.
82
•
Most projects require the development of a formal assessment instrument in order to obtain
all the necessary O&M information.
o
This instrument includes a detailed interview with the facility manager, building
operators and maintenance service contractors who are responsible for the
administration and implementation of the O&M program.
o
Depending on the scope of the project it may also include an in-depth site survey of
equipment condition and gathering of nameplate information.
o
An O&M assessment can take from a few days to several weeks to complete
depending on the objectives and scope of the project.
o
The assessment identifies the best opportunities for optimizing the energy-using
systems and improving O&M practices.
o
It provides the starting point for evaluating the present O&M program and a basis
for understanding which O&M improvements are most cost effective to implement.
8.2. Service Utility Agreements
Due to the development of the service provider sector, many companies are now outsourcing their
maintenance requirements to service provider companies. This is considered as a cost effective
means of implementing the required maintenance programmes, without hiring dedicated personnel.
In order to ensure that commercial sector companies achieve operational and maintenance savings,
their respective service provider companies, need to be made aware of the consequences of their
actions. A reduction in energy demands can be achieved through the manner in which they conduct
their works. If such companies do not actively implement measures for reducing energy
consumption, they should be made aware of the contents of this document, and encouraged to
implement same.
Furthermore a service company should not be solely assessed on their financial costs, but on their
ability and enthusiasm, in actively seeking and providing operational savings.
8.3. Maintenance Management
Proper operational and maintenance controls must be applied if an organisation is intent
on minimising energy consumption
Efficient maintenance encompasses a broad spectrum of applications.
•
In order to ensure that buildings operate as efficiently as possible a systematic approach to
operational and maintenance procedures should be adopted.
•
Traditionally, maintenance activities were likely to be considered as a necessary evil and
because of this attitude, too little time or effort was spent in trying to optimise the control of
83
operational and maintenance activities and costs. Maintenance departments may have
tended to receive little budgetary attention other than perhaps a nominal increase or
decrease from year to year because many organisations were predominantly trying to
increase profitability through streamlining operational costs.
•
Because operational and maintenance expenditures can account for a large percentage of
the overall cost structure of an organisation, increased attention is being turned to financial
accountability for the services.
•
If organisations were to audit their operational and maintenance expenses they would
probably find a sizable amount of revenue spent with little management control.
•
This is not to say that these costs are not scrutinised by individuals but that often accounts
departments, who authorize payments of utilities bills, do not realise how efficiently an
organisation is actually performing.
•
Proper operational and maintenance controls must be applied if an organisation is intent on
minimising energy consumption. To successfully control these costs, proper operational and
maintenance management policies and practices must be considered. Efficient operational
and maintenance management is a unique business process and requires an approach that
is typically different to other the core activities of an organisation. The purpose of the
following references is to assist organisations with consideration for efficient operational and
maintenance management activities. Although it will not provide a complete answer to
every management problem, it should at least provide a framework to allow decision makers
to select the most appropriate way to manage their own business.
8.4. Best Maintenance Practices
Best maintenance practices are methods, strategies, and actions that can make
maintenance operations more efficient and reduce maintenance and operating costs,
improve reliability, and increase profitability.
•
Best maintenance practices are methods, strategies, and actions that can make maintenance
operations more efficient and reduce maintenance and operating costs, improve reliability,
and increase profitability.
•
They can be defined in two categories: standards and methods.
o
Standards are the measurable performance levels of maintenance execution;
methods and strategies must be practiced in order to meet the standards. The
combination of standards with methods and strategies provides the elements of an
integrated planned maintenance system. Achievement of the best maintenance
practice standards (Maintenance Excellence) is accomplished through an interactive
and integrated series of links with an array of methods and strategies.
84
Two of the more common reasons that a plant does not follow best maintenance repair practices are:
o
Maintenance is totally reactive and does not follow the definition of maintenance
o
Maintenance workforce lacks the discipline to follow best maintenance repair
practices or management has not defined the standards for best maintenance
practices.
8.5. Proactive and Reactive Maintenance
Basic preventative maintenance, such as lubrication, cleaning and inspections can be perceived by
many organisations as a first step in a preventative maintenance program. These service steps can
take care of small problems before they cause equipment outages. Additionally, well serviced
equipment helps curtail unnecessary energy consumption. These inspections may reveal
deterioration which can be repaired through the normal planned and scheduled work order systems.
Organisations tend to perform their maintenance procedures to two distinct levels, proactive and
reactive maintenance. Reactive maintenance, commonly known as “fire fighting” is where an
organisation responds to a system anomaly once it has being highlighted that a system error has
occurred. Proactive maintenance is where organisations initiate a defined plan of action by
periodically inspect their equipment. This action is conducted with a view to eliminating the high
costs associated with breakdowns. Breakdowns can affect productivity and as such it is believed that
the cost associated with planned maintenance works is merited where an unacceptable loss occurs
due to equipment failure.
The proactive preventative maintenance (PM) program is the key to improving the maintenance
process. It reduces the amount of reactive maintenance, with associated call out charges, to a level
that allows other practices in the maintenance process to be effective. However to make the system
effective and focussed a means of automating the scheduling of the program is sometimes required.
It is seen that the where the PM program is ineffective that one of the main reasons was attributed to
a poor maintenance management system. To make the system effective it is seen that a well
maintained computerised system can assist greatly in curtailing both operational and maintenance
costs.
8.6. Purchasing of energy efficient equipment
The finance act of 2008 introduced a scheme where equipment in particular categories, meeting
particular energy efficiency requirements laid down by SEAI in conjunction with technical experts,
was approved for tax incentives in the form of allowing purchasers to write the asset off against tax in
an accelerate manner over the arrangement used for other purchased assets.
This register of equipment can be of great assistance to O&M managers in purchasing equipment as
it can reduce the requirement for the drawing up of detained technical specifications to ensure its
85
purchases are energy efficient. It is recommended that when purchasing equipment in categories
covered by the ACA (eg motors, VSD’s lighting refrigeration etc., that the O&M manager make one of
the assessment categories that the decision is based upon for purchase is whether the item is ACA
registered and where not a reason be determined as to why this is the case.
9.
Motors
The capital cost of a motor is typically expended in its first three months of operation
•
It is a well accepted fact that the capital cost of a motor is typically expended in its first three
months of operation
•
It is recommended that a formal policy be considered whereby all motors purchased or
installed on site are specifically chosen with reference to their energy efficiency rather than
just the purchase cost alone.
•
Unless there is a specific reason for doing not so, all motors should be Eff 1 or IE-3 rated.
Motors should never be rewound more than once, and where a motor is small and
inexpensive to purchase (<10 kW) consideration should be given to replacement rather
than rewind.
•
What should also be taken into account is that where a motor is rewound it is recognised
that it loses some of its original efficiency on each and every subsequent rewind.
•
Thus motors should never be rewound more than once, and where a motor is small and
inexpensive to purchase (<10 kW) consideration should be given to replacement.
It is suggested that a motor purchasing policy be put in place which considers the
maintenance requirements versus the energy efficiency criteria.
•
Indeed this theme carries across into the purchase of all energy using equipment
86
10. International Energy Policy9
International Energy Agency (IEA) analysis of energy efficiency identifies best practice, highlighting
the possibilities for improvements and policy approaches to realise the full potential of energy
efficiency for member countries. The IEA identified 25 energy-efficiency policy measures
10
which
cover all major energy end-uses and have the potential to reduce global energy demand by 20% by
2030, were all economies to adopt them.
At the 2008 G8 summit in Hokkaido, Japan, and G8 leaders committed themselves to maximising
their implementation of 25 energy-efficiency policy measures recommendations. The policy
measures suggested range across technology in buildings, appliances, transport and industry, as well
as end-use applications such as lighting and cross-sectoral policy measures.
11. Irish Policies 11
The Government of Ireland sets out in the 2007 Government White Paper: Delivering a
Sustainable Energy Future for Ireland, a target for a 20% improvement in energy efficiency across
the whole economy by 2020. The White Paper also states an ambition to surpass the EU target of 20%
with an indicative target of 30% energy efficiency by 2020. The public service is to take an exemplar
role in energy efficiency, with an energy savings target of 33% by 2020.
National Energy Efficiency Action Plan (NEEAP) was released in 2009. The plan details the current
package of energy-efficiency policies and measures that will contribute to both the national 20%
savings target for 2020, and the EU ESD 9% energy-savings target for 2016.
New building regulations (Technical Guidance Document L - Conservation of Fuel and Energy)
came into effect on the 1st July 2008. The goal of the new standards is to reduce energy requirements
by 40% in new dwellings, depending on the type and size of the dwelling. Since March 31st 2008,
when installing a replacement oil or gas boiler it is now a requirement that the boiler be condensing,
where practical (Section L3, Building Regulations Part L amendment – S.I. No. 847 of 2007).
The Government has assigned the public sector an exemplar role in improving energy efficiency due
to its significant size and its considerable purchasing power. The Public Sector Programme
promotes energy-efficient design, technologies and services in new and retrofit public-sector
9
Energy Efficiency in Ireland (2009 Report) SEAI Energy Policy Statistical Support Unit
International Energy Agency (IEA), 2008, 25 Energy Efficiency Recommendations by IEA to G8
11
Energy Efficiency in Ireland (2009 Report) SEAI Energy Policy Statistical Support Unit
10
87
projects. These projects are excellent examples of good practice and a demand leader for the services
and technologies involved.
The programme has three main elements:
•
A Design Study Support Scheme which provides support for professional expertise to
examine the technical and economic feasibility of design and technology solutions;
•
A Model Solutions Investment Support Scheme which supports energy management and
technology solutions in existing buildings and new build specifications;
•
An Energy Management Bureau which supports outsourced energy management services
to report on energy usage and identify energy-related projects.
11.1.
Energy Performance of Buildings
Building Regulations (Amendment) Regulations 2005 (S.I.873/2005) implement part of the Directive
2002/91/EC on the Energy Performance in Buildings.
The Building Regulations 1997 (S.I. 497/1997) have applied since 1 July 1998 and set out the
requirements applying to the design and construction of new buildings and the extension,
refurbishment and change of use of certain buildings.
Thermal Performance
The 2005 Regulations introduced a building energy performance assessment methodology for new
private homes and amended part of the Building Regulations 1997 to set higher thermal
performance and insulation standards for non-domestic buildings.
CO2 emissions
Under the 2005 Regulations, buildings must be designed so that the amount of energy required for
the operation of the building and the amount of CO2 emissions associated with the building are
minimised.
Heat Gain
In the case of buildings which are not dwellings, such as commercial buildings, buildings must be
designed so as to limit heat loss and, where appropriate, to maximise the heat gains through the
fabric of the building.
Space heating and Hot Water
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Energy efficient space and water heating services must be provided, and the building must be
designed to limit the need for air-conditioning.
What buildings do the Regulations apply to?
The Regulations generally apply to buildings whose construction commenced after 1 July 2006.
European Communities (Energy Performance of Buildings) Regulations 2005 (S.I.872/2005) and
European Communities (Energy Performance of Buildings) Regulations 2006 relate to Directive
2002/91/EC on the energy performance of buildings
The 2005 Regulations enabled the Minister for the Environment, Heritage and Local Government to
make Building Regulations implementing Directive 2002/91/EC. The 2006 Regulations implemented
elements of Directive 2002/91/EC dealing with Building Energy Ratings (BER) which are being
introduced across the
European Union. The BER system requires that BER Certificates, similar to the colour-coded energy
labels seen on many household appliances, be obtained for most buildings.
BER Certificates
The Regulations introduce a requirement that a BER Certificate and an Advisory Report be obtained
before a new dwelling can be occupied and before an existing building can be sold, leased or rented.
BER advisory report
After getting the assessment done on your property you will be issued with a BER Certificate and
advisory report. If you find that the rating hasn't reached the ideal required rating of B1 set by the
Building Regulations 2008 TGD L. There is no obligation for you to get work carried out on your
property to achieve the above rating, but what the advisory report gives you is a list of suggested
improvements for your property e.g. increases insulation, install low energy light fittings or even
upgrade your boiler if necessary. Once the suggested improvements have been completed the above
required rating would be achieved. Saving you money on your energy costs. Under Directive 2002/91,
common standards will be applied across the EU relating to the inspection and rating of buildings.
Alternative energy systems
The Regulations require that when any building with a useful floor area over 1000m2 is being
developed, due consideration must be given to the feasibility of installing alternative energy systems,
including:
•
Decentralised energy supply systems based on renewable energy;
•
Combined heat and power systems;
•
District or block heating or cooling, if available;
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•
Heat pumps.
Public bodies occupying large buildings must secure and display a BER certificate in a prescribed
form and display it in a prominent place clearly visible to the public.
Some buildings are excluded from the Regulations
The Regulations do not apply to a number of buildings, including:
•
Industrial buildings not intended for human occupancy over extended periods and where
the installed heating capacity does not exceed 10 W/m2;
•
Non-residential agricultural buildings where the installed heating capacity does not exceed
10 W/m2;
•
Stand alone buildings with a total useful floor area of less than 50m2.
•
Listed buildings
12. Safety Health and Welfare at Work
The sample legislation and guidance contents of this section of the guide are for reference only and
do not constitute legal or other advice. Professional advice should be sought in respect of the
applicability of any specific legislation or guidance.
The Safety, Health and Welfare at Work (General Application) Regulations 2007 (the 2007 Regulations)
which were introduced pursuant to the Safety, Health and Welfare at Work Act 2005 (the 2005 Act),
deal with the issue of workplace safety such as temperature , ventilation etc..
12.1.
Minimum Temperatures in the Workplace
Regulation 7 of the 2007 Regulations contains important provisions on minimum temperatures for
indoor sedentary work. It provides that an employer must ensure that during working hours, the
temperature in rooms containing workstations is appropriate for human beings, having regard to the
working methods being used and the physical demands on the employees.
In relation to sedentary office work, an employer must ensure that a minimum temperature of 17.5°C,
so far as is reasonably practicable, is achieved and maintained at every workstation after the first
hour's work. For other sedentary work, an employer must ensure that at every workstation where a
substantial proportion of the work is done sitting and does not involve serious physical effort, a
minimum temperature of 16°C is, so far as is reasonably practicable, achieved and maintained after
the first hour's work.
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Temperatures in rest areas, sanitary facilities, canteens and first-aid rooms must be appropriate to the
particular purpose of such areas. Workers are entitled to have some means readily available to them
to measure the temperature in any workplace inside a building. In practice, this means that if an
employee wants to measure the temperature there ought to be a thermometer readily available.
12.2.
Maximum Temperature in the Workplace
There is no maximum temperature specified in the 2007 Regulations. The HSA Guide notes that
although no maximum temperature is specified, this does not mean that any temperature is
acceptable. At high or uncomfortable temperatures, particularly when not caused by temporary
weather conditions, a means of cooling should be provided. Ventilation
In addition, Regulation 6 of the 2007 Regulations provides that each enclosed workspace must be
adequately ventilated. The HSA Guide states that in most cases the natural ventilation provided
through windows and doors will be adequate. However, in some cases mechanical ventilation may
be necessary, for example, where there are high dust levels or high temperatures or where the
workplace is isolated from the outside air.
13. Sustainable Energy Ireland Programmes12
Sustainable Energy Ireland also operates a number of key energy efficiency programmes for
businesses, including:
•
The Large Industry Energy Network (LIEN) for the largest industrial energy consumers in
Ireland. The LIEN is developing a set of role-model companies to demonstrate better energy
management:
•
The Energy Agreement programme for industry, based on the Irish energy management
standard IS 393 / EN16001
•
SEAI service for small and medium enterprises (SME), which offers energy advice,
assessment and monitoring, with the aim of cutting their energy use by 20%;
•
The Accelerated Capital Allowance (ACA) scheme introduced in the Finance Act 2008. This
scheme enables businesses to write off the entire cost of a specified set of energy efficient
motors, lighting and building energy management systems in the first year of purchase;
•
The Combined Heat and Power Deployment Scheme which provides grant support to
assist the deployment of small-scale (<1MWe) fossil fired CHP and biomass (anaerobic
digestion and wood residue) CHP systems.
12
Energy Efficiency in Ireland (2009 Report) SEAI Energy Policy Statistical Support Unit
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A complete list of all the existing and committed to measures that will contribute towards meeting
Ireland energy-efficiency targets is contained in the National Energy Efficiency Action Plan (NEEAP).
The complete list of Sustainable Energy Ireland’s energy-efficiency programmes is available on
the SEAI website www.seai.ie.
14. Energy Management – The benefits of a systematic approach
Companies seeking to effectively reduce energy use and improve energy efficiency are advised to
establish an energy management framework to ensure that their energy management program is as
effective as possible.
SEAI have published guides to assist companies in establishing energy management systems.
Details available on their web-site:
www.seai.ie/energymap
www.seai.ie/Your_Business/Energy_Agreements/IS393_Energy_Management_System/
The most current energy management standard in use is the European Energy Management
Standard IS EN 16001
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15. Guidance for analysis of a commercial buildings O&M aspects using this guide.
This section is written to give a users assessment on the practical usage of this guidance Document
that is an output of the 2009/10 special working group on commercial buildings.
15.1.
Recommended approach to usage.
In most cases an individual using the guidance document will be reasonably familiar with the
building under assessment but the following procedure is nonetheless recommended to be
undertaken to ensure that their judgment is not biased by an apparent knowledge of the building
that may blind them from opportunities that exist.
15.2.
Gathering of existing knowledge.
This stage starts initially with the gathering of such data such as the floor area of the building, hours
of occupancy, work carried out in each main area of the building, levels of service laid down as being
required, energy billing data, and lists of major energy using devices if appropriate. Energy billing
data should be got in the most detailed manner possible. Access to supplier 30 minute billing should
be made available for electricity and if there is natural gas on site on a daily metered basis, the daily
gas values should be provided.
15.3.
Assessment of current energy data.
This stage of the assessment is crucial as it allows the assessor the opportunity to review the energy
profile of the building over the past periods to assess the actual usage against that which he would
expect.
This will typically include the review of the electrical and gas data individually and
collectively against identified parameters such as weather, occupancy, production figures, bed
nights, floor area, etc. When assessing against weather a number of weather assessments will
normally be made for both cooling and heating degree days to see if the building profile is as
expected. For a typical commercial office building with no humidity control and forced ventilation
we would normally expect to see a reasonably strong correlation of electrical consumption to cooling
degree days (base 15.5) and natural gas consumption having a relatively strong correlation to heating
degree days (again base 15.5)
Carrying out this trial at a number of temperatures allows an assessment to be made as to whether
the building conforms to conventional norms or if there is a reason for any deviations observed.
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Assessing against a production or turnover figure also gives an indication as to whether the energy
usage is production or output driven.
Assessing against the day of week allows indications to any possible hidden energy impacts (eg we
may find that Wednesday has a large gas and electrical consumption which might be related to an
unnoticed or overlooked part of the process normally not focused upon from an energy perspective.
Assessing a standard weekend period to a naturally low intensive period such as Christmas day or
new years day can give an impression of what might it be possible to bring the load over weekends
down to, or indeed night load in some circumstances. This therefore gives a first impression of what
savings might be achievable.
15.4.
Assessment of areas of significant energy usage
At this point in time it should be reasonably apparent where the areas of significant use are, these
being the areas or loads that contribute greater to the overall load of the organisation. Identifying
the areas of significant energy use (significant energy users) and indeed why you have deemed these
to be so is a major key step in energy management as these are the areas upon which the major focus
is now to be placed moving forward.
Having identified the areas of significant energy use, the first step is to assess what the service
delivery level in place is, and how this compares to the actual requirements of the building or facility.
As an example we may have a requirement to have one floor of offices temperature conditioned
seventeen hours a day, and the remainder for eight hours per day, and what may be actually in place
is that all offices are conditioned for both temperature and humidity for twenty hours per day.
Next step is to assess the control that is seen to be active on the building management system/
system controller, and to see how this compares to the profile of usage as seen on the energy
consumption data. If we have a particular unit such as a chiller plant identified as a significant energy
user and it is taken out of service at 1900 hrs every day according to the BMS, do we seem this
reflected on the energy consumption data. If this does not appear to be the case it is possible that
the output of the unit is being turned off, but not the unit itself and that savings are being reduced.
Another worthwhile approach is to assess the output service of the equipment for impact, ie if the
chiller plant is turned off at 1900, do we see a temperature rise in areas that had been served by the
unit, or is there a reasonable explanation why this is not so.
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Having assessed the control, switching of the unit as currently configured and assessing service
against service requirements, it is now the appropriate time to assess the equipments operation
against best practice. Eg what is chiller set point, why is this required, does it float in winter/ load
dependant, are the time controls appropriate for the load timings both in summer and winter, who
operates the equipment, are any relevant logs or data held for the unit. Is there a fundamental
understanding in-house of the energy impacts of the various ways that the equipment may be
operated and shut down, left in standby etc. Are there any competing elements?
One useful step to undertake at this stage is to generate a list of all the all the various parameters that
might cause the unit to use more energy. If this step is done correctly and with enough attention, it
will trigger lots of thoughts that may never have previously considered with regard to energy.
Eg. Large split ACU’s in an open office area.
1.
hours of operation
2.
Whether they are switched on and off automatically or manually, timed or temperature
controlled
3.
How close the control band is attempting to maintain the space conditions
4.
Whether the control is temperature only or temperature and humidity
5.
Set point in place
6.
Number of people with access to change the set point
7.
Whether the unit is operated in cooling only mode, or heating and cooling
8.
constant heat gains in room (equipment etc)
9.
variable heat gains in room (people, some equipment, solar gain)
10
External weather conditions
11
people opening external windows
12
Leakage heat and cooling from adjacent areas / doors left open.
13.
interaction of adjacent units, eg one heating mode and the other cooling
14.
calibration/ tolerances of the various control elements
15
Position of temperature sensors
16.
People complaints
17
Type of work carried out within.
18
Filter blockage in the unit
19
Build up of dust on the unit coils
20
Location of condenser
21
Pressure settings in the refrigeration unit
In generating this list, which is not complete, the user will find it useful to consult the O&M guide.
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Having generated this list it is also useful to consider if there are any legal or other obligations that
you may need to take into consideration. Eg minimum and maximum workplace temperatures. This
may limit your opportunities for reduction.
In raising this list the user may find it useful to start generating a list of opportunities for energy
reduction in parallel as typically as you recognise a parameter that causes the energy demand of the
device to increase, you will recognise an opportunity to assist in prevention. It is good to capture
these as they arise.
15.5.
Assessment of maintenance practices
Having undertaken this assessment, looked at all the gaps between current and operational best
practice, and understanding better the general parameters that cause an increase in energy
consumption of the areas of significant energy use, now is an appropriate time to undertake an
assessment of the current maintenance practices.
In reviewing the maintenance regime in place, it is important to get an understanding of who will be
undertaking the particular maintenance, whether it is consistently the same person, and their own
familiarity with the equipment that they are maintaining. It is also important to know if there are any
factors in place that encourage that individual to consider energy efficiency or reliability etc. and their
level of training and experience with regard to energy.
It is worthwhile at this stage to review the maintenance regime, and indeed your operational
practices against the self generated list of factors affecting the significant energy use. At this point
you are trying to ensure that a combination of operational and maintenance practices are such as to
ensure that the energy usage of the significant energy users is minimised and controlled to a practical
extent. Of course the maintenance undertaken will need to be appropriate to the nature and scale of
the unit, the energy usage of it, the potential/ risk of excess energy usage and the importance of the
reliability of the service delivered. What is appropriate for a bank of cassette units in an office
operated continually where reliability is crucial may not be appropriate for a single office, used
intermittently, manually switched on with time delay off.
In deciding the maintenance routines now, consideration must be given to the level/ knowledge of
the individual undertaking the assessment, and how generic/ specific the routine is to the location.
For example where the routine is specific to a large area with multiple cassette units installed, there
may be a requirement to set specific condenser and evaporator pressures on a specific cooling load
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with a very restricted tolerance level allowable to balance controls, and major focus may be given to
assessment of the control system and possible calibration of temperature sensors, whereas for a
single office unit, this would not be appropriate.
Similarly it needs to be said that a single cassette unit with a cooling capacity of 50kW installed in an
area where the only cooling load likely to be encountered is approximately 20kW, will not need the
same configuration of set points as one that is likely to need to dissipate 50kW of heat. There is
therefore two essential approaches to take with the maintenance undertaken.
a.
Person undertaking the maintenance is not knowledgeable enough to make an assessment
of the appropriate configuration for the unit. Here the maintenance routine should specifically list
the appropriate configuration to be checked against, along with actual reading expected and
allowable tolerance and the individual undertaking maintenance does not have the authority to
make changes unless authorisation is received.
b.
Person undertaking maintenance is deemed to be of an appropriate competence to be able
to make the assessment of how the machine is best configured. Here the maintenance routine is less
specific, and the person making changes is required to specifically list any changes made during the
routine, along with the rationale behind this change and the potential energy effect that this will
have along with the basis for this assessment.
Having undertaken this assessment you should now be in a position to identify the correct
operational and maintenance practices appropriate to your organisation.
16. Setting an appropriate reduction target.
As you will have identified some areas where you believe energy savings might be made, it is
appropriate to set an reduction target against which the improvements may be assessed. If there is a
single large area of saving identified it may be possible to designate a quite scientifically calculated
target against this (eg if you have improved the COP of a chiller plant and know the previous
electrical loading of the chiller over the previous year.), otherwise it may be more practical to design a
target based on your own judgement of what you think is possible, taking into account also the
potential interactions of various opportunities.
17. Verification of improvements.
Whilst it is not always so important to verify the actual savings achieved by the implementation of an
energy savings opportunity, it is always important to verify that the opportunity implemented has
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worked and has actually saved energy. It is not unusual in practice to come across energy savings
opportunities implemented that have not operated correctly and the reasons are not always
apparent. For this reason it is important when assessing an opportunity for implementation, that
consideration be given as to how the opportunity when implemented is going to be verified, and this
should always be decided before the opportunity is implemented.
Verification methodologies may vary in scale from the most simple to more complex. Eg the
verification of the correct operation of an opportunity where an un-insulated water pipe has been
insulated would essentially be limited to a visual inspection, as it is quite obvious that once the
correct pipe has been insulated that savings will be achieved and whether it matches previous
assessments is not always that important.
In other cases quite simple opportunities to save energy may have unexpected effects and for this
reason it is important to assess the potential ways in which an opportunity when implemented may
not operate as planned. An example of this may be where an opportunity has been identified to
increase the chilled water set point of the water leaving a chiller plant by one degree, leading to an
expected saving of between 2 and 4%. On the face of it this might appear straight forward, but what
may actually occur in making this change, is that the chiller output capacity might not actually be
able to meet the load for all occasions with this set point, and a result may be that a second stage
may be called into operation intermittently that might not have previously have been required. It is
not unusual for mechanical equipment such as chiller plant to have minimum run times to prevent
mechanical failure due to short cycling and this may cause energy consumption to increase as
opposed to decrease from this opportunity. This type of opportunity may be verified in a number of
ways, for example assessing the number of hours on the various stages of the plant over time or
assessing the average chiller load over time. This however brings into focus the requirement for
baseline assessment against which the changes are to be verified. The baseline assessment is where
the operation of the equipment to be modified is assessed over a representative period to
understand its operation and then when the change is made it is possible to verify the saving to some
extent.
Where the savings expected are relatively large (15-20%) in relation to overall consumption, or in
some cases large in relation to the variability in overall consumption, savings in the order of 5-10%
may be verified using the overall energy consumption analysis, and the baseline assessment may
against previous utility bills.
It is always good where possible, especially with 30 minute billing (electricity) availability, or daily
metering (Natural Gas), to verify the savings against the energy profile as this can be seen as evidence
of the correct operation of the improvement. Understanding of the profile of a bill for a commercial
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premises cannot be underestimated. In short I would replace the old adage “you cannot manage
what you don’t measure” with a more appropriate one, “you cannot manage what you don’t
understand” and measurement is only one step along the way
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