Bosch Compress 3000 DW FO Specifications

This document is confidential and restricted to exclusive use by the official technical
assistance of Bosch in the countries of destination of this product.
1. INTRODUCTION ............................................................................................ 3 1.1 GENERAL DESCRIPTION ............................................................................................................ 4 1.2 PRODUCT PRESENTATION ......................................................................................................... 5 1.3 WORKING PRINCIPLE ................................................................................................................ 6 2. HEAT PUMP ELEMENTS .............................................................................. 7 2.1 ANODE PROTECTION ................................................................................................................ 8 2.2 ELECTRICAL RESISTANCE AND THERMOSTAT ........................................................................... 10 2.3 COIL FOR EXTERNAL SOURCE OF ENERGY ................................................................................ 12 3. MODULE ...................................................................................................... 12 3.1 COMPONENTS AND CHECKS IN THE REFRIGERATION UNIT ......................................................... 13 3.2 COMPONENTS SYSTEM ........................................................................................................... 14 3.3 MAIN COMPONENTS DATA ...................................................................................................... 17 3.4 ELECTRICAL MEASUREMENTS ................................................................................................. 19 4. COMPONENTS OVERVIEW ........................................................................ 23 4.1 COMPRESSOR ........................................................................................................................ 23 4.2 FILTERS AND DRIERS .............................................................................................................. 27 4.3 EXPANSION VALVE ................................................................................................................. 27 4.4 PRESSURE CONTROL BY NORMALLY CLOSED PRESSURE SWITCH ............................................... 28 4.5 EVAPORATOR ........................................................................................................................ 29 4.6 CONDENSER .......................................................................................................................... 30 5. HUMAN MACHINE INTERFACE – HMI ....................................................... 31 6. MAINTENANCE AND PREVENTIVE ACTIONS .......................................... 37 6.1 CORROSION........................................................................................................................... 37 6.2 WATER QUALITY .................................................................................................................... 37 6.3 TYPES OF SCALE .................................................................................................................... 39 6.4 MAINTENANCE ACTIVITIES FOR TECHNICIANS ............................................................................ 40 7. TROUBLESHOOTING .................................................................................. 47 7.1 FAILURES PREVENTION AND DETECTION ................................................................................... 50 7.2 EVAPORATOR UNDER PERFORMANCE ...................................................................................... 51 7.3 CONDENSER UNDER PERFORMANCE ........................................................................................ 52 7.4 OTHER RECOMMENDATIONS AND DEFINITIONS .......................................................................... 53 7.5 SERVICE NEEDS..................................................................................................................... 54 7.6 TERMINOLOGY ....................................................................................................................... 55 8. Page 2 from 63
APPENDIX.................................................................................................... 59 6720649497 SM HP270-1 2012/09 en
Domestic Hot Water Heat Pumps (DHW-HP), with or without air connections ducts, use the heat existing in the
surrounding air, or the waste heat from the indoor air, as energy source for DHW preparation.
These machines are commonly known as air-source hot water heat pump and they are energy-saving and
environmentally friendly equipment with a plug-and-play system structure and easy maintenance.
The heat pump has generally three operation modes:
normal mode – only heat pump operation;
combi mode– heat pump and electric resistance operation;
electric heater mode– only electric resistance operation;
The heat source can be the waste heat as referred, but also the potential energy of unheated rooms, or the air
discharged from rooms with high humidity such as bathrooms, toilets and laundry rooms.
Coil Commercial product name Product designation
7736500782 Bosch
7736500891 Bosch
7736500989 Bosch
Compress 3000 DWFI
Compress 3000 DWFI
Compress 3000 DWFO
HP 270-1E 1 FIV/S
HP 270-1E 0 FIV/S
HP 270-1E 1 FOV/S
7736500991 Bosch
Compress 3000 DWFO
HP 270-1E 0 FOV/S
7736500781 Buderus
Logatherm WPT 270 I-S
HP 270-1E 1 FIV/S
7736500890 Buderus
Logatherm WPT 270 I
HP 270-1E 0 FIV/S
7736501013 Buderus
Logatherm WPT 270 A-S
HP 270-1E 1 FOV/S
7736501014 Buderus
Logatherm WPT 270 A
HP 270-1E 0 FOV/S
7736500884 elm leblanc +5º/+35º
7736500885 elm leblanc +5º/+35º
7736501015 elm leblanc -10º/+35º
Ondea PAC 270 AI-S
Ondea PAC 270 AI
Ondea PAC 270 AE-S
HP 270-1E 1 FIV/S
HP 270-1E 0 FIV/S
HP 270-1E 1 FOV/S
7736501016 elm leblanc -10º/+35º
Ondea PAC 270 AE
HP 270-1E 0 FOV/S
7736500169 Junkers
SupraECO W SWI 270-1X
HP 270-1E 1 FIV/S
7736500883 Junkers
SupraECO W SWI 270-1
HP 270-1E 0 FIV/S
7736500988 Junkers
SupraECO W SWO 270-1X
HP 270-1E 1 FOV/S
7736500990 Junkers
SupraECO W SWO 270-1
HP 270-1E 0 FOV/S
7736501149 Vulcano
7736501236 Vulcano
AquaEco HP270-1 E S
AquaEco HP270-1 E C
HP 270-1E 1 FIV/S
HP 270-1E 0 FIV/S
Table 1: Appliances overview
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1.1 General description
This model of domestic hot water heat pump provides hot water for residential purposes, using a closed refrigerant
unit filled with a refrigerant gas (R134a). This ensures the energy production taking out the energy from a cold
source - air, and delivering this energy to a secondary circuit – water - where a simple circulation pump, ensures
water movement through a heat exchanger, heating the water stored in a tank.
Pict.1 (a) Refrigeration Unit and (b) Storage Tank (with coil)
The engine absorbs energy “Qc” from a cold source (heat absorbed from air) and expels energy “Qh” to a hot
destination (heat delivered to water) while Work “W” is done in the refrigerator circuit (electrical supply). The work
done is ensured by an electrical plug that supplies electricity to the compressor and the movement of the refrigerant
gas R134a ensures the transport of the energy from “Qc” to “Qh”.
Heat sink
Heat source
Pict.2 – Heat Pump close circuit representation
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1.2 Product presentation
Apart of the main function of the heat pump operation with the required mandatory components of an air/water heat
pump with electrical backup installed for any eventual need, the heat pump has, in some of the models, an internal
integrated coil for external energy source as integration with existent standing or wall hung boiler or even solar
energy installation.
Picture 3 shows the internal constitution and main components:
1) Fan and evaporator group
2) Compressor
3) Condenser (Plate Heat Exchanger)
4) Filter dryer and expansion valve
5) Water circulation pump
6) Storage tank
7) Electrical resistance for backup
8) Internal coil for external backup (eg. solar)
Pict.3 – Main Elements of the Heat Pump (model +5ºC / +35ºC)
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1.3 Working principle
The heat pump working principle is based on the transfer of the heat, and not on conversion of electrical energy
into heat. It removes energy from a low temperature source (ambient air) and transfers it into a high temperature
source (hot water tank).
Pict.4 – Energy and electrical input
Electricity is used to upgrade the comfort (temperature) of heat energy and not to generate heat energy. That is the
reason why COP (Coefficient Of Performance) of the heat pump is higher than 3 (which corresponds to an
efficiency of 300 %).
Pict. 5 – Generic overview of the 4 stages of gas
1. Liquid refrigerant R 134a boils at a low temperature in the evaporator. The output is a low temperature and low
pressure vapour.
2. Vapour pressure and temperature increase in the compressor. The electric motor is used to drive vapour
through the compressor and increase vapour temperature and pressure.
3. Heat exchange is done in the condenser. The refrigerant transfers heat to the water and cools up, condensing
and leaving energy there.
4. The liquid returns to the evaporator after passing through an expansion valve.
decreases and the liquid evaporate again.
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The refrigerant pressure
Heat Pump Elements
The top EPP cover must be carefully disassembled before any intervention on the module. Follow instructions from
picture 6, existent in the sticker on the back of the tank.
Pict.6 – Disassembling of top cover
In front of the appliance and protected by an EPP front panel (fixed to the tank with 4 magnets), it is possible to find
the magnesium anode and the electric resistance for backup.
Pict.7 – Front view of the heat pump
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2.1 Anode Protection
The anode, installed in the water heater tank, will slowly dissipate whilst protecting it. The life of the water heater
tank is ensured by the periodical inspection, done by an authorised person, replacing it when required.
The anode inspection period shall take in consideration that, for softened water supply or in areas of worse water
quality, it is recommended to inspect it more often and for some other critical different situations, a water treatment
is recommended.
The DIN 4753 determines that all magnesium anodes must be checked, at least each two years (considering
normal conditions), ensuring a visual control.
The acceptable water quality to the heat pump storage tank requires:
Water pH between 6,5 and 9,5
Hardness range ≥ 3.0 ºdH.
Depending on the appliance production date, the anodes can have a measured terminal, or not. Those which do
not have a measurements terminal need a direct visual inspection to ensure its efficient operation and consequent
life time of the tank. Anodes with measurement terminal must be connected to the HMI in order to ensure correct
(a) Anode without terminal (non isolated)
(b) Anode with terminal (isolated)
Pict.8 – Magnesium anode and measurement connections
Pict.9 – Magnesium anode with measurement terminal
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An anodic current meter can be used to measure the current and evaluate the anode time life. The measured value
shall be higher than 0,3 mA.
Attention: For a correct measurement, the tank must be full with water! The electrical connection must be ensured
after measurement.
Pict.10 – Anodic current measurement with an anode tester or a multimeter
Anyway, a visual inspection is strongly recommended every 2 year, in order to identify an eventual start of a crack
in a part of the anode, or eventually the calc deposition over the magnesium anode surface which will decrease the
anodic current as well, but will also disable the protection function of the anode.
The visual inspection should include a material surface, weight, diameter and length changing control.
Pict.11 – Example of used magnesium anodes
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2.2 Electrical Resistance and Thermostat
A thermostat control activates the electric resistance of 2kW immerged in the storage tank. This component has a
safety function set at 90ºC, limiting the temperature from an external source (solar, boiler, etc, …) to 80ºC.
Pict.12 – Electric Resistance (2 kW)
Pict.13 – Bipolar thermostat interfaces
Pict.14 – Check voltage supply o the thermostat
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Pict.15 – Check continuity between terminals
After any intervention in the anode and/or thermostat, ensure the correct assembly with correspondent washer and
assembly of the protection cover.
Pict.16 – Protection cover of the thermostat and electrical backup group
In the most recent production models, order to increase robustness of the tank in the models with coil, the electric
heater of the models HP 270-1E 1 (with coil), is from was isolated. Spare part will is available as isolated electric
heater for models, with and without coil.
a. Resistor (560Ω)
b. Dielectric insulation (tank / electric heater)
Picture 17 – Isolated electric heater
Attention: Resistor connection Picture 17.a is essential to ensure function and life time of the electric heater and,
consequently, of the product. In case of defected component, the complete electric heater must be replaced.
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2.3 Coil for external source of energy
The coil integrated in the storage tank of some of the models (see table 1), can be used to combine the heat pump
with a back up energy system like solar, boiler, etc. In case the coil will not be used, do not remove the caps from
the coil inlet and outlet connections. This will avoid thermal losses due to the contact of the air in the coil with the
surrounding hot water in the tank.
In order to control the temperature in the tank for the external heat source, a pocket for external sensor is available
and adapted to the available fixation systems of sensors in TT, ensuring the correct contact with the tank.
Pict.18 – Storage tank and example of external sensor fixation system to pocket
A routine maintenance agreement should be taken with a licensed service person or organisation. In addition, endusers should monitor their installation and call a service person immediately, in case any abnormal
operation/situation is found. The system should be serviced by a qualified person, every 12 months, depending on
use/installation conditions.
Junkers / ELM Leblanc
Bosch / Buderus / Vulcano
Pict.19 – Components overview
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Components checking procedure
Inspect all the elements in the installation place
Check the airflow clearances
Check the output temperature
Clean the evaporator coils as following:
– Clear the outside of the coil of debris
– Vacuum the coil fins using a soft bristle brush attachment – take care to avoid bending the fins
– Spray water from the inside to the outside of the coils to remove stuck debris using a hose and spray gun
– Vacuum or remove by hand any remaining debris in the unit
Check if coil fins are damage – if bent, straighten them using a proper tool
Lubricate fan bearings if required – sealed bearing units do not require any oiling
Inspect fan and repair, if required
Ensure that the condenser unit is secure and levelled in both directions. If necessary, adjust the levelling
feet on the appliance, or make level with timber/plastic shims. If the unit is seriously out of level, repair or
replace the base of the unit.
Check the operation of the air-on/air-off with a digital thermometer
Check pipe joints for refrigerant leakage, with a bubble solution
Check terminals and connections – clean and tight if necessary
Check the voltage and current
Service checklist
Provide the end-user with a filled service checklist after each service
Explain the importance of the thermal disinfection function (anti-legionella protection) for the water quality
inside the tank
3.1 Components and Checks in the Refrigeration Unit
The science of refrigeration is based on the fact that the liquid can be vaporized at any desired temperature by
changing its pressure. Taking in consideration the example of water, that under a normal atmospheric pressure of
1,01 bar boils at 100ºC, if in a closed vessel under a higher pressure, it boils at a higher temperature.
The technician for the refrigeration circuit must have specific material and tools to deal with these circuits and make
the measurements and controls in the correct way, respecting the existing standards.
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The list of available material (separate document) must be checked in order to choose the adequate material for
repairs in the refrigeration circuit.
3.2 Components System
Model + 5ºC to +35ºC
The refrigerant must enter in the evaporator, in the liquid state, and then, by vaporizing due to heat absorption from
the surrounded air, the refrigerant leaves the evaporator in the vapour state and during the refrigerant
condensation, there is a heat generation, which will be transferred, in this case, to the domestic water, that flows in
the condenser.
Pict.20 – General components overview in the module +5ºC / + 35ºC
As the temperature of the available water is always higher than the one from boiling refrigerant in the evaporator,
the refrigerant in the vapour state needs to be pressurized till its condensing temperature is above the temperature
of the water available for the condensing process – that is why a compressor is needed.
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The compressor and condenser are needed to enable the same refrigerant to be used several times. The cost of
compressing and condensing the vaporized refrigerant is far less than the cost of often renewing of the refrigerant.
To maintain the difference in pressure between the condenser and the evaporator caused by the compressor, an
expansion valve is needed. The expansion valve separates the high pressure from the low pressure side in the
system. Only a small amount of refrigerant liquid flows through the valve. In fact, the valve is adjusted so that the
liquid flow rate is the same as the evaporation rate.
The refrigerant boils in the evaporator at a constant low pressure and temperature. Heat is removed from the air,
cooling it. After leaving the evaporator, the vaporized refrigerant flows through the compressor, where the pressure
of the vaporized refrigerant is raised to a point at which it can be condensed by some relatively warm fluid (water at
normal conditions).
The compressor removes the refrigerant vapour and this creates such a low pressure in the evaporator that the
evaporation temperature is kept below the surrounding temperature. After being compressed, the vapour enters the
condenser and is condensed at constant pressure and temperature. Heat is transferred from the condensing
vapour through the walls of the condenser to the water in the tank.
The expansion valve has two functions: maintain the pressure difference between the condenser and the
evaporator, together with the compressor and regulate the volume of refrigerant going to the evaporator, in order to
ensure a correct evaporation and allow the absorption of energy by the gas.
Heat exchange
Heat exchange
Pict.21 – Schematic representation of heat pump principle
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Model - 10ºC to +35ºC
The working principle of this model is the same as for +5ºC to +35ºC, with exception of the defrosting process,
which is done through a solenoid valve, activated by the control unit, depending on the temperature measured by
the NTCs, assembled in the evaporator fins and sensing the air temperature which will be detailed further in this
Pict.22 – General components overview in the module -10ºC / + 35ºC
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3.3 Main Components Data
Suppliers: Behr, Mahle
Specification from supplier:
Cooling capacity of 1.4 kW
Specification from supplier:
Supplier: EBM PASPT
Centrifugal fan operation 230 V
Specification from supplier:
2 kW of heating capacity
(temperature limiter: opens at
(model KB 134 VFN),
160ºC, closes at 70ºC)
(model WHP01900BSV)
Specifications from supplier:
Supplier: Swep
Maximum pressure 50 bar
Specifications from supplier:
Supplier: Wilo ZRS12/2-3KV
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3 speed pump
maximum pressure 10 bar
Q flow = 0.2 m3/h
Specifications from supplier:
- Liquid line filter drier
Dry filter
- Drying agent in bulk
- Low pressure drop
Supplier: Honeywell
- Hermetic construction
(Series FF)
- Temperature range: TS = -40ºC / +80ºC
MOP at +15ºC - TEV with built in orifice of 2
mm, bulb Ø of 12 mm, internal equalization
Expansion valve
and fixed superheating setting.
Supplier: Honeywell
Specifications from supplier:
(Series TLK)
- Thermostatic expansion valve for serial
produced systems.
- Max. ambient temperature: 100ºC
Capillary tube length of 1 m
- Max. bulb temperature: 140ºC
- Evaporating temp.: - 15...+40ºC
- Inlet ODF: 3/8" / Outlet ODF: 1/2"
Pressure Switch
Low Pressure Switch (LPS)
PS = 45 bar
Supplier: Danfoss
TS = 30ºC – 85ºC
High Pressure Switch (HPS):
PS = 45 bar
TS = 30ºC – 85ºC
Table 1 – Module components overview
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3.4 Electrical Measurements
Scheme A
Scheme B
Pict.23 – Electrical diagram -10ºC / +35ºC
(Scheme Nr)
+5ºC / +35ºC
-10ºC / +35ºC
A5 / B1
A11 / B2
A13 / B3
R 10k = 25ºC = 10000 Ω
Hot Water NTC
R 10k = 25ºC = 10000 Ω
Cold Water NTC
R 10k = 25ºC = 10000 Ω
Fins NTC
R 8k = 25ºC = 8400 Ω
A19 / B15
A12 / B10
Pump Wilo
230 (196 – 253) Vac
50 (47,5 – 52,5) Hz
19 / 32 / 48 W (0,10 / 0,15 / 0,21 A)
“Swep” type
Filter Drier
PS = 11 – 43 bar
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(Scheme Nr)
+5ºC / +35ºC
-10ºC / +35ºC
A20 / B16
A1 / B11
Expansion valve
TLK 2.0 R134a / MOP + 15ºC
14 x 3 tubes
Solenoid Valve
230 V / 50 Hz
230 (196 - 253) Vac
50 (47,5 - 52,7) Hz
85 W
A3 / B7
230 (198 - 264) Vac
50 (47,5 - 52,5) Hz
520-565 W / 475-490W
(Mitsubishi / Highly)
Compressor Capacitor
17 μF / 15 μF
(Mitsubishi / Highly)
Compressor Protection
Bimetallic thermal switch
(open at 160ºC, close at 70ºC)
Supply Cable to control
230 V (+10% / -15%), 50 Hz
High Pressure Switch
Temp. = 60ºC
Opening pressure = 27 bar*
Closing pressure = 20 bar*
Low Pressure Switch
Temp. = 5ºC
Opening pressure = 0,7 bar*
Closing pressure = 2,4 bar*
A10 / B12
Electric resistance
230 V / 50 Hz (R=26,5Ω)
A10 / B13
Safety Thermostat
T sec = 90ºC
Control Unit
230 V (+10% / -15%), 50 Hz
* Relative pressures
Table 2 – Schemes A and B - components identification
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The NTC’s listed in the table above, are supplied in a common cable with the following configuration:
(A) model -10ºC / +35ºC
(B) model +5ºC / +35ºC
Pict.24 – NTC cables
The NTC sensors for air, cold and hot water are the same, but give different information to the software in the
electronic control. Following table indicates the measurable resistance value to check and identify each proper
These NTC sensors are a 10kΩ type. In case their minimum and maximum operation values are below or above
the expected temperature/resistance values, the display will present the correspondent error code.
The NTC sensor in the fins is 8kΩ with characteristic listed on table 3.
NTC Resistance (Ω)
NTC Resistance (Ω)
(10kΩ type)
(air + cold + hot)
Temperature (ºC)
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Table 3 – NTC characteristic
Pict.25 – Electrical cables connection on HMI
Electrical Supply
Pump Connection
Capacitor Connection
Fan Connection
Fan Capacitor
Pict.26 – Cable connections overview
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Components Overview
4.1 Compressor
The compressor is usually driven by an engine and this unit compresses or transports the refrigerant through the
system. The main principle is that the refrigerant is compressed as it is sucked into the compressor in a gaseous
form at a low temperature from the evaporator.
Pict.27 – Compressor
It is then forwarded in gaseous form at a high temperature and high pressure to the condenser. The dimensioning
of the compressor has to be adapted to the system size. The compressor is filled with special oil for lubrication
purposes this is an important checking point for servicing.
Almost all refrigerant compressors contain oil, which lubricates the compressor moving parts and forms seals
between these moving parts during the compression. The oil is important to achieve high efficiency in the
compressor, but it affects negatively the heat transfer in the system.
Compressors are lubricated (Oil content - 270ml) in order to:
reduce frictional wear on bearings and other moving parts
cool the refrigerant gas during compression
prevent refrigerant gas leakages
The lubrication type depends on the compressor and the manufacturer recommendations must be followed.
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Electric test to the compressor:
The compressor has some electrical connections and a temperature limiter thermostat that ensure its protection.
Using a multimeter, is possible to control its functionality, nevertheless the HMI will detect if compressor is running.
Cables and cover protection have clear identification of the different connections.
R – Main electro valve
S – Auxiliary electro valve
C – Common
Pict.28 – Compressor electrical connections and thermal protection
Checking Continuity and Resistance (Ω)
Between C – R > 0 Mitsubishi = 4.7 Ω / Highly = 5.84 Ω
Between C – S > 0 Mitsubishi = 8.2 Ω / Highly = 7.62 Ω
Between R – S > 0
Pict.29 – Testing compressor
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Electric test to compressor:
Check earth connection
C – chassis ≠ 0
S – chassis ≠ 0
R – chassis ≠ 0
Attention: In case of continuity the compressor is defected
Pict.30 – Testing of compressor
Thermal Protection
This function is ensured by a bimetallic temperature limiter which opens its contact when high temperature
(T=160ºC ±10ºC) is reached during operation.
Pict.31 – Testing of thermal protection limiter
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(a) Open contact
(b) Close contact
temperature activation – T≥160ºC
normal operation – T<70ºC
Pict.32 – Functional position
After any intervention, ensure correct cover protection assembly.
Pict.33 – Cover of electrical elements from compressor
Capacitor of Compressor
Pict.34 – Discharging capacitor
In case of check capacitor, discharge electric charge with a resistance of 20k and 2W
Not OK - ∞
OK - 0Ω
Pict.35 – Capacitor testing
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4.2 Filters and driers
Moisture or water vapour may cause problems in any type of refrigerant system, because moisture may freeze in
the orifice of the expansion valve, causing corrosion of metal parts and wet the motor of the compressor, damaging
it (motor burnout and oil sludge). On the other hand, foreign matter may contaminate the compressor oil and
become lodged in valve parts, making system inoperative.
The filter drier, positioned in the liquid line protects the expansion valve, absorbing potential humidity in the
refrigerant (R134a). The combination of humidity and high discharge gas temperatures will accelerate
decomposition of the oil and increase risk of compressor failure.
In case of need to access refrigerant circuit and in case of remove and charge of new gas when components are
replaced, it is mandatory the replacement of the filter the replacement is recommended because if a filter in the
liquid line becomes blocked, there will be a pressure drop refrigerant to boil and create flash gas, which will disrupt
the operation of the expansion valve.
Pict.36 – Filter Drier (cut model for internal view)
4.3 Expansion valve
The expansion valve has two main functions:
- Controlling the amount of refrigerant entering the evaporator:
- Maintaining the pressure difference between the condenser (high pressure) and the evaporator (low
The pressure difference created by the work of the compressor is kept by the expansion device.
As much of the evaporator surface as possible should be covered with liquid refrigerant without liquid being carried
over to the compressor. If the capacity of the evaporator increases, the expansion valve should allow a larger flow
of refrigerant (bulb detects high superheating) and vice versa.
A smaller refrigerant mass flow results in a higher level of superheating, because less surface area is required for
The expansion valve or orifice tube represents the point of separation between the high pressure and low pressure
sections in the refrigerant circuit and is installed before the evaporator. The liquid refrigerant is injected into the
evaporator through the expansion valve or orifice tube. The refrigerant expands, evaporates and thus releases
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evaporation cooling. In order to achieve optimum cooling capacity in the evaporator, the refrigerant flow is
controlled by the expansion valve or orifice tube.
The component achieves high durability thanks to welded stainless steel head and stainless steel diaphragm and
contains the gas charge for quick response time adapted to small evaporators.
In case of replacement, the component should be protected from the heat during soldering process.
Pict.37 – Expansion valve (cut view)
4.4 Pressure control by normally closed pressure switch
In this closed refrigerant circuit, is very important to be sure about the correct range of temperatures / pressures, in
order to have an efficient system.
Pressure gauges (accessible to the technicians), are permanently installed to allow monitoring compressor suction
(low pressure side) and discharging pressures (high pressure side).
These kinds of connections use throttle valves that prevent against gauge fluctuation when readings are to be
taken. In both sides high and low pressure, the high and low pressure switches will protect the system from
excessively low or high compressor temperatures.
If the pressure drops below a pre-set level, the compressor is stopped and the same valve will allow the system to
start (after reset) when pressure reaches again its safety value. In the other hand, the other pressure switch in the
compressor outlet, will measure the outlet pressure and, in case of excessively high pressures, the compressor is
stopped until the malfunction is solved and pressure decreased.
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Pict.38 – Pressure switch from Danfoss
Various shunt relays are triggered by the pressure switch in order to guarantee safe and effective use of the
refrigerant system under all conditions. Through this process, individual system components are switched on and
off according to the defined pressure points. The pressure switches can fail due to contacting problems or soiling.
Regular system servicing prevents failure.
Pict.39 – Pressure switch, filter drier and expansion valve group
4.5 Evaporator
The evaporator is used for the heat transfer between the air surrounding and the refrigerant in the system. The
refrigerant entering the evaporator under pressure expands, i.e. it converts from a liquid to a gaseous state, and
thus "evaporates" in the evaporator. The cooled air produced by this process is discharged to the environment via
the large surface of the evaporator.
Up to 50% less weight and up to 40% less volume for the same capacity - the striking features of Behr's disc
evaporators have advantages in comparison with traditional round-pipe evaporators: quicker draining of
condensation, lower air resistance, higher air flow and reduction of micro-organisms that cause annoying smell.
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Pict.40 – Fan and Evaporator
4.6 Condenser
Domestic Hot Water Side
(Secondary circuit)
Refrigeration side
(Primary circuit)
Pict.41 – Condenser
The condenser is required to cool down the refrigerant heated up by compression in the compressor. The hot
refrigerant gas flows into the compressor, thereby dissipating heat to the other side of the plate. As it cools, the
refrigerant pressure falls and the refrigerant state changes from gaseous to liquid.
Soldered flat pipe condensers have high capacity and less volume.
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Pict.42 – Plate heat exchanger condenser working principle
In case of hard water, the condenser shall be periodically cleaned in order to avoid obstruction.
Pict.43 – Plates of the heat exchanger and counter-flow representation
Human Machine Interface – HMI
User manual must be used to verify functions and active parameters. For the service mode, following instructions
should be considered. The control unit has a standby consumption of 3W.
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Display (LCD)
Selection Buttons
Pict.44 – HMI Panel
Entrance in the service mode:
Press “Menu” + “Ok” button during more than 5 sec
Pict.45 – Enter in service mode
Table 4 includes the meaning of each parameter visible on the service mode that can be used by technicians for
diagnostic and repair actions.
+5 / +35
-10 / +35
Set point temperature of hot water on
control unit
Temperature of Hot Water
(NTC in the top of the tank)
Temperature of cold water
(NTC between pump and condenser)
Active Symbol
Temperature of air in circulation
(NTC between air admission and
Temperature of the evaporator
(NTC in the fins)
Current Consumption
(Instantaneous electrical consumption of
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Number of air defrost procedures
Number of gas defrost procedures
last 10 failures with error code indication
1F until 10F
(If no error is memorized, display shows “-- --“)
cleaning of the historical memory of the last
10 failures
test display (all segments ON)
Exit Service Mode
(for FD<202, minimum press time of 3sec)
Table 4 – Service Mode Parameters
Working modes:
Error Mode
OFF Mode
Reset function by pressing OK
button for more than 3 sec
Anti-Freeze Protection function
active for tank and module
Stand-by Mode
Operation Mode
Diagnostic /
Adjustment Mode
Combi Mode*
HP Mode
Electrical Mode
Adjustment Mode
Service Mode
In case the air temperature is out of the specified range, the appliance automatically activates the electrical back
up (without leaving the Combi mode). One hour after the warning display (HOT or COLD) has appeared, the
appliance checks the air temperature again and, if it is within the range values, turns again to heat pump operation.
The control loop is done every hour, after electrical back up emergency operation.
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The working principle is based in the following considerations:
Switch OFF
No Reaction from system
Switch ON (main switch in the back of HP)
Error in memory?
Stand-by mode (1)
Error Mode
For Stand-by Mode
Stand-by mode
HMI actuation
LCD Backlight ON
LCD Backlight OFF (after 15
sec without any selection)
Active Operation Mode
Temperature of the Tank
Clock & Day Function
Temperature Selection
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Temperature Blinks until
confirmation with OK button
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Temperature remain previous one
after 10 sec without any selection
Conditions for operation:
The heat pump compressor is activated according the following conditions and according control unit settings
TTop ≤ T set – 3ºC
(and Tbottom < 60ºC)
Start Up
TTop ≥ T set
(or Tbottom ≥ 62ºC)
Conditions for anti-freeze protection (in HP or Standby mode):
Software version after HPAF0211 (-10ºC models) and HPAF0311 (+5ºC models):
TBottom < 4ºC
Module Anti-Freeze:
Water pump runs for 2 minute
Tank Anti-Freeze:
Water Pump ON
Electrical heater ON till
TTop ≤ 5ºC
Software version before versions HPAF0211 (-10ºC models) and HPAF0311 (+5ºC models):
TBottom < 2ºC
Module Anti-Freeze:
Water pump runs for 1 minute
TTop ≤ 20ºC and TBottom < 5ºC
Tank Anti-Freeze:
Water Pump ON
Electrical heater ON till
TTop>25ºC or TBottom > 10ºC
Conditions for legionela disinfection:
Water pump is always ON
(for both “Man” or “Aut” selection)
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Full mode until Ttop = 60ºC
Electric Heater mode until Ttop = 70ºC
Legionela stops when:
TTop≥70ºC or TBottom ≥ 60ºC
(or time in Legi > 24h)
Conditions for air-defrost sequence:
Air defrost sequence is activated in both +5ºC or -10ºC models when T air > 5ºC and < 10ºC for more than 60 min:
Tbottom < 20ºC (defrost every
90 min)
Tbottom < 35ºC (defrost every
150 min)
Tbottom < 60ºC (defrost every
240 min)
Fan ON
during 10 min
Water Pump
Conditions for gas-defrost sequence:
Gas Defrost sequence is activated only in -10ºC models when T
> -10ºC and < 5ºC for more than 15 min,
performed in 2 steps (Pre-gas defrost + Gas defrost), when Compressor ON for more than 180 min or Compressor
ON for more than 60 min and Tair-Tfins > 3.5ºC for more than 1 min.
1 step: Pre-Gas Defrost
2 step: Gas Defrost
Fan ON
Time for pre-gas defrost:
Tbottom < 25ºC / Time = 2 min
Tbottom > 25ºC and < 40ºC / Time = 1 min
Tbottom > 40ºC / Time = 0.5 min
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Gas Defrost sequence stops when
Tfins > 6ºC (for more than 30 min)
Maintenance and preventive actions
6.1 Corrosion
Corrosion is the term for a chemical or electrochemical reaction between a material, usually a metal, and its
environment, which produces a deterioration of the material and its properties.
A metal can be exposed to many different kinds of corrosion and below we can see some examples of the ones
applicable to this type of brazed plate heat exchangers.
Pitting and crevice corrosion
They are quite the same, or at least the phenomenon is more or less the same. Pitting may appear on exposed
surfaces, for example attacking the stainless steel if the layer is damaged (this natural layer can be formed when
steel is in contact with air). This kind of defect may cause leakages. Crevices may occur in welds that fail to
penetrate, in flange joints and under deposits on the steel surface.
General corrosion
This is a kind of deterioration, distributed more or less uniformly over a surface. This type of corrosion is more
predictable than pitting.
a) General copper corrosion
b) Pitting corrosion in stainless steel
Pict.46 – Examples of corrosion
Unfavourable environment, may lead to the increase of the risk of corrosion and picture 45 shows examples of
corrosion in either stainless steel or copper brazing.
This kind of heat exchangers are sensitive to high concentrations of chloride ions in an oxidizing environment,
because chlorides form a galvanic cell with oxygen and specially stainless steel is too sensitive to this kind of
attack, as well as higher temperatures make chlorides more aggressive.
6.2 Water quality
In order to prevent this kind of phenomena, it’s very important for the installer/technician, to evaluate the water
quality and, warn the end user and prepare the installation accordingly.
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The corrosive effect of natural water can vary considerably with its chemical composition. Water quality is of great
importance to avoid corrosion in the plate heat exchanger (condenser).
City Water
Normally is controlled and of good quality.
Well water
Is usually fairly cold and clean, which implies that it has a low biological content. However, the
concentration of scale forming salts (calcium and magnesium sulphates and carbonates) can sometimes
be very high. Pitting corrosion may be initiated due to salt deposits.
River and lake surface water
The concentration of scale forming salts is usually fairly low. However, there may be amounts of solids
ranging from salts and soil particles to leave. Some type of pre-treatment is necessary, particularly to
control biological activity
Sea water
Is not recommended because of the corrosive action of very high chloride concentrations
Check water quality and recommendation of use of the supplier of the condenser (SWEP), represented in table 5.
Water Content
Alkalinity (HCO3-)
Sulphate (SO4
HCO3- / SO4 2 -
Electrical Conductivity
Ammonia (NH3)
Chlorides (Cl )
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AISI 316
70 – 300
70 – 300
< 10 μS/cm
10 – 500 μS/cm
> 500 μS/cm
< 6.0
6.0 – 7.5
7.5 – 9.0
> 9.0
2 – 20
> 20
< 300
(mg/l or ppm)
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Free chlorine (Cl2)
Hydrogen Sulfide (H2S)
Free (aggressive) carbon
dioxide (CO2)
Total Hardness (ºdH)
Nitrate (NO3)
Iron (Fe)
Aluminium (Al)
Manganese (Mn)
> 300
< 0.05
> 0.05
5 – 20
> 20
4.0 – 8.5
< 100
> 100
< 0.2
> 0.2
< 0.2
> 0.2
< 0.1
> 0.1
Symbols explanation:
+ Good resistance under normal conditions
0 Corrosion problems possible, particularly when there are other factors rated 0
- Use is not recommended
Table 5 – Water composition parameters
Table 5, gives an idea of the resistance of AISI 316 stainless steel and pure copper (99,9%) in water to corrosion
by some important chemical factors. However corrosion is a very complex process influenced by many different
factors in combination, this table is a considerable simplification, which should be taken in consideration.
6.3 Types of scale
Calcium carbonate (CaCO3) can be formed when calcium or bicarbonate alkalinity is present. An increase in heat
and / or an increase in pH will cause precipitation of calcium carbonate.
Calcium Sulfate (CaSO4) is 50 times more soluble than calcium carbonate and will, therefore, precipitate only after
calcium carbonate is formed. This type of scale can exist in various forms, and its formation depends strongly on
the temperature. An increase in temperature decreases the solubility of this salt and increases the risk of scaling.
Water scaling tendency
In order to estimate the scaling tendency of natural water, several parameters must be analysed and determined:
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calcium content
ionic strength of the water (Is)
Please note:
For water analysis, mg/l is equivalent to ppm
The relation between calcium and calcium carbonate is 40g CA 2+ ≃ 100g CaCO3
TDS = salt content (mg/l) or possibly the conductivity x 0.63 (μS/cm)
If Is<0, the water has a tendency to be corrosive.
If Is>0, the water has a tendency to cause scaling.
Eliminating the scaling problems
There are several ways to eliminate the scaling problem. Usually a commercial product containing additives to
enhance the effect and / or prevent corrosion can be used; nevertheless a specialist should be consulted to
recommend the adequate procedure for the treatment. Chemical cleaning is the use of chemicals to dissolve or
loosen deposits from process equipment and piping. Removal is uniform and generally at a low cost.
Step 1: Chemical cleaning solutions
Using organic acids (are weaker than mineral acids but safer to material and handling). The organic acids can be
used in combination with other chemicals to remove the scale completely.
Acetic acid is used to clean calcium carbonate scale.
Step 2: Passivation
Passivation is a procedure to remove surface iron contamination from the equipments.
6.4 Maintenance activities for technicians
In terms of maintenance, it is strongly recommended a general control of the main components of the heat pump,
before the control of the refrigerant module circuit.
Electric measurement1) or visual inspection
Magnesium anode
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Depending on the version
Check position*, connection, continuity
* Ensure distance to copper pipes
Manual activation
Safety valve
Pre-charge verification (vessel without
Expansion vessel
water pressure)
Leakages, lack or defective insulation
Pipe work
Cleaning of calc deposition, inspection of
Heating element
Table 6 – Resume of main maintenance actions
The main connections are through thread connection with washer, however and for the connections of the flexible
hose with o’ring connection, the lubricant L 641 (part nr 8 709 918 413 - Water lubricant for water valve
connections) must be used.
Pict.47 – (a) O’ring lubricant in water connections (b) white conductivity thermal paste
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In the NTC sensor, in contact with the pipe of cold water from the bottom of the storage tank, and in the NTC
sensor, in the pocket of the hot water from the top of the tank, the thermal paste “Wacker” (part nr 8 719 918 658)
must be used to ensure an efficient contact and consequent efficient temperature sensing.
Condenser Maintenance - Descaling procedure
The process of descaling in the condenser of plate heat exchanger type can be done in the place, with no need of
removing the component. In cases where water flow from tank to the condenser plate heat exchanger is blocked
with debris, lime scale or other substances, it is strongly recommended the use of a pump, by the technical service.
Picture 47 shows one example of a recommended pump, from the supplier Sanit.
(Available models: KalkMax 500 or 800)
Pict.48 – Sanit Kalkmax pump
According to the supplier of the condenser (SWEP), with this type of components it can be used a liquid such as
This cleaning compound especially developed to dissolve and remove the internal deposition of scale forming salts
in water supplied systems is caustic, with a pH-value of 1,5 and it consists of 9% of Phosphorous acid, 35% of
citric acid and 1% of inhibitor with 55% of water. The waste of this cleaning liquid should be neutralized to PH7.
These acids are bio-degradable and non-toxic and remove all types of scale as well rust that can be accumulated
inside of heat exchangers obstructing water flow and reducing heat transfer. The inhibitor makes this product work
as a buffer and protects all the sensitive components you find in heat exchangers and in complete heating or
cooling systems.
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Pict.49 – Kaloxi descaling liquid to clean plate heat exchangers
Descaling process:
Close cold water inlet and open hot water tap to take out pressure from the top of the heat pump;
Remove connection in the top of the condenser plate heat exchanger to allow the outlet of the water
and then, remove the connection in the bottom;
Pict.50 – Unscrew water connections to the condenser plate heat exchanger
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Connect flexible connection of the pump already with the liquid
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Pict.51 – Flexible hose of descaling pump connection
- Put the pump in operation, taking in consideration that the flow must be, inside the heat exchanger, in the
opposite direction of the water. The direction can be defined in the pump on the correspondent lever, as
shown in picture 51.
Pict.52 – Flexible hose of descaling
Leave the pump in operation for some minutes to remove lime scale.
After cleaning process, make circulation with clean water to eliminate vestiges of the acid solution
In the models with manual air purge (depending on production date), ensure its correct purging position.
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Pict.53 – Example of a manual air purge
Evaporator Maintenance
The fins of the evaporator should be cleaned and aligned in order to allow an adequate air flow through the
complete surface, ensuring the correct function of the evaporator, and the consequent energy transfer to the
refrigerant gas.
Pict.54– Detail of the fins and 3 passages evaporator (cut model)
Pict.55 – Damaged fins in the evaporator
The alignment of the fins can be done with an adequate brush and the cleaning process, with a vacuum cleaner.
During maintenance, the surface of the evaporator can be sprayed with the same available solution in the market
as for air conditioning, which cleans and avoids deposition of dirtiness.
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Pict.56 – Example of cleaning and purifier spray for evaporators application
For the maintenance, diagnostic and performance analysis of the heat pump module and its refrigerant circuit,
following information must be taken in consideration. On chapter 7, additional information is described to help the
understanding of the operation of the circuit.
Value for
(+5ºC to +35ºC) and
(-10ºC to +35ºC)
Type of refrigerant
Gas charge
375 g
GWP = 1300 / ODP = 0,00
Ebullition temperature = - 26,1 ºC
3,5 bar / 10ºC
outlet of evaporator / inlet to
Discharge pressure /
8 bar / 50ºC
outlet of compressor / inlet to
Internal pressure /
3,5 bar / 4ºC
Inlet of evaporator / outlet of
expansion valve
Suction pressure /
Refrigerant pressure drop
on evaporator
0,3 bar
Super heat
3,8 K
Sub cooling
Table 7 - Design data of the heat pump for inlet water and inlet air at 15ºC
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Code E01 Lock Out error
Fault in the hot water NTC temperature sensor (in the top of the tank)
Sensor is disconnected
Check connection to control unit and cable
Sensor is in short circuit
Check cable, sensor and measure NTC value
NTC has values out of its borders
Measure NTC sensor value
Code E02 Lock Out Error
Fault in the cold water NTC temperature sensor (blue mark)
Sensor is disconnected
Check connection to control unit
Sensor is in short circuit
Check cable, sensor and measure NTC value
NTC has values out of its borders
Measure NTC sensor value
Code E03 Lock Out Error
Fault in the air NTC temperature sensor (yellow mark)
Sensor is disconnected
Check connection to control unit and cable
Sensor is in short circuit
Check cable, sensor and measure NTC value
NTC has values out of its borders
Measure NTC sensor value
Code E04 Warning Code (self reset error)
Temperature in storage tank higher than 80ºC (Detected by the hot water NTC in the top of the tank)
Heat Pump storage tank connected to a solar installation.
Reduce maximum temperature of storage tank
in the solar controller
Heat Pump storage tank connected to a boiler installation
Reduce the sanitary water set point in the boiler
Hot Water NTC sensing wrong temperature value
Measure NTC sensor value
(multimeter in Ω position)
Code E05 – ONLY in model -10ºC - Lock Out Error
Fault in the Fins Evaporator NTC temperature sensor (white cables)
Sensor is disconnected
Check connection to control unit and cable
Sensor is in short circuit
Check cable, sensor and measure NTC value
NTC has values out of expected range
Measure NTC sensor value
Code E06 Warning Code
Setting buttons hold down for longer than 30 seconds.
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Self Reset after release buttons
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Code E07 – Only for internal technical use
Code E08 – Only for internal technical use
ONLY FOR models,
produced till February 2012
Code E09 Lock Out Error
Failure in Compressor System
Condition: Appliance was turned on, is in standby and fault was displayed before operation
Contacts Open on safety elements - thermal protection
Check Continuity
Contacts Open on safety elements – high pressure switch
Check Continuity
Contacts Open on safety elements – low pressure switch
Check Continuity
High Pressure Switch Activation
Condition: After first start up of system, fault is displayed after HP start operation
Water pump operation is noisy
Circulation pump is not working
Check air presence in the sanitary side / pump
and purge it
Check pump connection and its operation Unblock the pump impeller through the front
Condition: Appliance blocks after some running time
Water flow through condenser is too low
Water shortage >12h
After a repair and / or R134 replacement
Check eventual calc or debris deposition in the
sanitary side of the condenser plate heat
exchanger and clean it.
Too much refrigerant inside circuit (max. 375 g).
Rework charging procedure.
Code E10 Lock Out Error
Fault in the electrical backup resistance (by current sensor in control unit)
Activation of the safety thermostat (over temperature)
In case of repetitive error, drain water and disassemble
Reset thermostat manually
(check adjusted temperature – must be at
maximum position “+” aprox. 80ºC)
In case of appliance with internal coil, check
water temperature from the backup system
(solar, boiler, …) – must be < 80ºC
Calc deposition over resistance surface avoids
thermal dissipation and consequent over
temperature detection.
Resistance malfunction.
produced from
March 2012 on
Code E11 Lock Out Error
Failure in Compressor System
Condition: Appliance was turned on, is in standby and fault was displayed before operation
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Contacts Open on safety elements - thermal protection
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Check Continuity
Contacts Open on safety elements – high pressure switch
Check Continuity
Contacts Open on safety elements – low pressure switch
Check Continuity
Fault in the low pressure side
High pressure loss in the air ducts
Check ducts and accessories equivalent length
Failure in fan operation
Check fan operation and connection
Leakage in the refrigeration circuit
Check with an leakage detector the origin of the
leakage, repair and refill circuit.
Over current limiter activation
Check compressor - blocked
Expansion valve does not leave correct amount of gas for
Check bulb position and insulation
Expansion valve is blocked or bulb has lost charge
Repair by replacing the complete expansion
Dry filter is saturated and block refrigerant flow
(filter outlet is much colder than inlet)
Replace filter
Code HOT Warning Code
Temperature of air admission higher than + 35ºC.
Self Reset error after normal temperature conditions are
Code COLD Warning Code
Temperature of air admission lower than + 5ºC or - 10ºC according model.
Self Reset error after normal temperature conditions are
Table 8 – Error codes identification
The technician for the repairs in the refrigeration unit of the heat pump, must have competences in
soldering, repairing and analysis of performance of the machine, to ensure safety and correct servicing of
the unit.
Only a certified technician, with adequate training from the respective entities in the country of destination, can give
the certificate of competence to the authorized persons to carry out service and maintenance in heat pump
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7.1 Failures prevention and detection
The design data supplied by Bosch must be known by authorized service partner’s technicians, in order to prevent
and avoid the following problems, nevertheless, the service partner is responsible to prepare technicians in such a
way that the following problems will never happen in the field with an end user.
Refrigerant leaks after repairs and / or components replacement;
Defective soldering or damaged components due to lack of knowledge in this area;
Maintenance operations without recovery of refrigerant gas and correspondent treatment according
country laws and directives;
The vacuum of the system can be done using the two available charging probes, and must be performed correctly
in order to guarantee no moisture inside of refrigeration system.
The filter dryer must be replaced every time that the refrigeration system is opened and serviced, in order to avoid
reading the saturation point.
The bulb position must be ensured, in the top position after the evaporator, to allow a correct reading and a proper
functionality of the expansion valve.
In case of HMI replacement, respect and assemble the NTCs in the correct position to avoid wrong temperature
For the analysis of common failures (even without error code), the following material is recommend in
order to ensure a better detection of the origin of the malfunction by the refrigerant circuit technician.
Pict.57 – Tools for working pressure measurement in both high and low pressure side
Table 9 indicates the design data of the heat pump, in order to allow the refrigerant technician to repair, make
vacuum and re-charge the R134a in the unit in case of malfunction detection in the refrigeration circuit.
Temperature (ºC)
Pressure (Bar)
Temperature (ºC)
Table 9 – Working pressures and temperatures
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Pressure (Bar)
7.2 Evaporator under performance
The evaporation process is sensitive and potentially unstable. Minor changes in performance have major effect on
the system performance (COP).
A one-degree change in the evaporation temperature changes the COP by approximately 3% and an unstable
process could also cause the evaporation temperature to fluctuate, with a potential risk of freezing in the
evaporator. The critical parameter for the system performance is the saturated pressure at the compressor inlet.
Check Points:
Check the installation
Check the evaporation temperature at the compressor inlet
Use compressor data to compare with cooling data
Check the evaporation pressure at the evaporator outlet
Compare the evaporation pressure at the outlet with the evaporating pressure at the compressor inlet. This
difference should be kept to a minimum to avoid unnecessary losses in cooling capacity. This should be
measured in the suction side of the compressor (pressure gauge available). By measuring the temperature
in the evaporator and knowing the calculated pressure drop, we can check actual pressure drop.
Check the amount of superheat
A high level of superheating could indicate that the expansion valve is not releasing enough floe to the
evaporator or vice-versa.
- Check the expansion valve and the positioning of the bulb
Make sure that the valve is able to regulate. If the bulb is too close to the evaporator, the evaporation
temperature may fluctuate. The bulb should never be placed on the bottom of the suction line, because refrigerant
droplets may evaporate at this point, affecting the regulation and causing punctual low temperatures.
- Check fins alignment and no dirtiness deposition, because it will cause an underperformance due to the
lack of heat exchange between air temperature (between +5 and + 35ºC or -10 and + 35ºC according to the
correspondent model) and the liquid gas inside of evaporator area.
Bulb capillary
Pict.58 – Expansion valve detail (cut model)
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Pict.59 – Position of the bulb and insulation
7.3 Condenser under performance
The condensing process is normally stable, and will not cause any major disturbances on the system performance.
The evaporator performance can have influence in the condenser performance, and the problems are usually
manifested as an increased pressure head.
Check Points:
Check the installation visually (refrigerant and water circuits are connected in counter-current mode
with the refrigerant inlet at the top.
Check the condenser for temperature variations on the outside
If gas is trapped, or water channels are obstructed, inside the condenser, there will be large surface
temperatures differences.
Check temperatures on the water side
Make sure that the entering and leaving water temperatures correspond to the design conditions. If the
temperature difference is higher than the design conditions, the water flow rate has been reduced.
Check the amount of sub-cooling
Too much sub-cooling will block the heat transfer surface from the condensing process and thus
increase the condensing pressure. This may indicate that the system has been overcharged. Release
refrigerant charge until a reasonable value (2k – 5k) is achieved.
Check the compressor
The condenser capacity is always set by the compressor. If this one is working improperly, the
condenser capacity will be affected.
Check the suction pressure at the compressor inlet
Use the compressor data to compare the capacity design data
Check the pressure drop over the secondary side of the condenser
Pressure drop is proportional to the flow rate squared.
Check the pressure drop in the discharge line
If the filter located after condenser and before expansion valve is saturated and the pressure drop is
too high, replace component.
Check the discharge temperature
Compare with design conditions supplied by Bosch.
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7.4 Other recommendations and definitions
Pict.60 – General refrigeration circuit representation
 Pre-assessment for technical partners (refrigerant circuit)
experience in training, installation, service, maintenance, commissioning, retrofitting, system
current experience in other refrigerant circuit appliances as air conditioning, other heat pumps
types, chillers, …
previous experience in refrigerant recovery, recycling, reclamation or charge in system
type of refrigerants already handled
level and training needs
Specific tools for R134a availability
Refrigerant circuit parameters
suction pressure (at evaporator outlet / compressor inlet – use pressure gauge connection available)
suction temperature
discharge pressure (at compressor outlet / condenser inlet – use pressure gauge available)
discharge temperature
Liquid temperature (at condenser outlet / expansion valve inlet)
For condenser heat exchanger check:
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temperature into the evaporator;
temperature out of the evaporator
temperature into the condenser
temperature out of the condenser
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7.5 Service Needs
Using pressure manometers and thermometer
The normal measuring equipment is a service pressure gauge and preferably some type of thermometer. Data is
collected using fixed gauges and connecting service gauge to the available connections to the service in the
Portable instruments as refrigerant analysers are also available and give already all data needed with possibility of
printing the report.
Pict.61 – Digital refrigeration analyser (example from Testo)
Nevertheless, service pressure gauges should be calibrated regularly and be of good quality. The data obtained
from the service will have some accuracy and will depend greatly on the “human factor”. They should therefore be
used with caution and compared with design data of the system to find and analyse discrepancies.
A thermometer with a sensor attached with heat transfer paste and insulation must be used to ensure accuracy in
the temperature readings. If possible fixed thermometers are preferable.
Sensor assembled with
thermal paste
Pict.62 – Example of fixation of contact thermometer
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During the process of repairs and manometer connections to the pressure gauges, check the eventual existence of
micro-leakages with an adequate equipment in order to avoid the lost of refrigerant gas to the atmosphere and
consequent malfunction in the appliance operation after your visit.
Pict.63 – Example of an electronic leakage detector from Testo
7.6 Terminology
Overheating of the refrigerant gas
In the fundamental process, the gas entering the compressor is assumed to be dry and saturated. In the reality the
gas is overheated. The overheating is the difference between the temperatures at the outlet of the evaporator.
It is a practical necessity to allow the refrigerant vapor to become superheated to prevent the carry-over of liquid
refrigerant into the compressor, where it may cause severe damage due to its incompressibility. It may also
contaminate the lubricants. The level of superheating should be kept to a minimum to minimize both the work to be
done by the compressor and the necessary heat transfer surface in the evaporator.
Sub-cooling of the refrigerant gas
In the fundamental process, the liquid leaving the condenser was just on the saturation line for liquids. The
pressure drop in pipes, filters, etc, before the expansion valve may cause problems and a small part of the liquid
can enter in vaporization. In order to avoid this, the condensed liquid is therefore sub-cooled to a temperature
below that of the saturation temperature corresponding to the condenser pressure, for two reasons:
The cooling capacity of the process is increased and the risk of gas bubbles in the fed to the expansion valve is
avoided (gas bubbles in the inlet flow to the expansion valve disrupt the regulation mechanism). The sub-cooling is
the difference between the temperatures at the end of the condenser.
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Efficiency Definition
The basic compressor-driven refrigeration cycle consists of one compressor, two heat exchangers (evaporator and
condenser) and a throttling device (expansion valve). These components form the circuit in which the refrigerant
circulates and the cycle operates between the two pressure levels P1 and P2, and the temperatures T1 and T2,
where T1 > T2.
Pict.64 – Diagram of enthalpy and pressure relation
The superheat is the difference between the evaporating temperature and the temperature of the gas coming from
the evaporator. The evaporating temperature is determined with a pressure gauge and the temperature of the gas
is measured with a digital thermometer
Takes place in the evaporator and indicates the gas temperature raise (superheat) after it has changed the
into gas state
Attention: The more refrigerant the expansions valve lets flow into the evaporator, the lower the superheat will be
achieved. Since there is more liquid refrigerant in the evaporator there will be less gas and the gas will then be less
Pressure part
Pict.645– Expansion valve representation
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The superheat describes how efficient is the evaporator for the vaporization
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In the ideal cooling circuit the superheat is 0°C. This means that the whole evaporator is being used for
vaporization, and the efficiency is as high as possible
We need a few degrees of superheat in order to establish the expansion valve operation and make sure
that no liquid is brought inside the suction side of the compressor
Attention: If liquid gets into the compression chamber of a piston compressor it will cause serious damage
High superheat; Frosting on the pipe after the expansion valve, poor efficiency, high hot gas temperature.
Low superheat; Ice and frosting on the suction line to the compressor, evaporating pressure and superheat is
Note: High and Low pressure switch in the refrigeration circuit will activate when pressures are out of range
Adjusting the superheat
In this type of appliances the adjustment of the superheat is made by opening or closing of the expansion valve.
Closing the expansion valve = superheat increase (Less refrigerant is let into the evaporator, causing a lower
evaporating pressure and higher superheat).
Opening the expansion valve = superheat decrease (More refrigerant is let into the evaporator, causing a higher
evaporating pressure and less superheat).
Expansion Valve actuation:
Suction line to compressor is too cold (too much liquid in evaporator to be boiled properly): decreased
pressure above diaphragm causes valve to close.
Feeler bulb senses enough heat in suction line – diaphragm makes valve open, allowing more R134a into
evaporator coil.
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Pict.66 – Expansion valve and bulb position
The sub cooling is the difference between the condensing temperature and the liquid line temperature. The
condensing temperature is determined with a pressure gauge and the liquid line temperature is measured with a
digital thermometer
Takes place in the condenser and indicates the liquid refrigerant cooling after it has changed into liquid
state. The sub cooling is created by adding so much refrigerant into the circuit that a level of refrigerant is
present in the bottom of the condenser.
The higher level the higher the sub cooling becomes. Theoretically we can sub cool the liquid down to the
temperature level of the incoming heat carrier. In practice this is not possible, when the level reaches a
certain level, the condensing pressure rises.
Adjusting the sub cooling:
First make sure that the superheat is properly adjusted
The adjustment of the sub cooling is made by filling or extracting refrigerant.
Adding refrigerant = the sub cooling increases (the level of refrigerant in the condenser is higher and the liquid
is then more sub cooled by the inlet heat carrier.)
Extracting refrigerant = the sub cooling decreases (the level of refrigerant in the condenser is lower and the
liquid will then be less sub cooled).
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8. Appendix
Guide with list of material for service partners
The following list is only a guideline with the main important elements to make repairs in the refrigeration circuits of
Heat Pumps. The material should be adequate for the proper use of refrigerant gas.
Depending on the type of machine, other tools can be needed and the list should be adapted to the available
equipment in the countries.
Material / Tool
Fire extinguisher
Bottle to be used for security
purposes in case of fire
Safety Equipment
Accessories for handling and
protection of the technician during
working process in refrigerant
Portable lights
To ensure correct working light
conditions in installation place
Inspection Mirror
Mirror for visual inspection of
brazing joints
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Soldering equipment
To soldering components in
repairs in the refrigeration circuit.
Thermal paste (protect heat
transmission to surrenders)
To avoid damages in the
components near of the soldering
Nitrogen Kit
For circulation inside of refrigerant
circuit during brazing process
Manometers group (R134a)
For the measurements of
refrigeration operation pressures
and temperatures, for the
purpose of refrigerant transfer
and for system evacuation, a
service gauge manifold is used.
Flexible hoses
To use always with the same gas
type and to be connected from
the manometers kit to the vacuum
pump or recovery station.
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1) Nitrogen cylinder
2) Nitrogen pressure
3) Nitrogen transfer hose
with 1/4” female flare SAE
1) Manifold body
2) Manifold body
3) Sight glass for refrigerant
4) Low pressure valve
5) Vacuum pump valve
6) High pressure valve
7) Valve connection for
charging cylinder or
recovery unit
8) Hose connection
1/4”male flare SAE
9) Vacuum hose connection
1/4” and 3/8”
1) Refrigerant standard
hose with 2 x 1/4” SAE
female flare connection
2) Adjustable and
replaceable core-depressor
(valve opener) ‘schematic’
Recovery Equipment
To use during phase out of the
gas to deliver to a recovery
cylinder used in the field to
recover, recycling, reclamation
and evacuation of refrigeration
1) Recovery unit ‘oil less’
for commercial
2) Condenser and ventilator
3) High and low pressure
4) Refrigerant inlet and
outlet valves
5) Inline filter-drier
Refrigerant recovery cylinder
To use after take out gas of the
refrigerant unit and used to
deliver in the adequate entities for
recycling process.
Vacuum pump
To make vacuum to the
refrigeration system after repairs
and parts replacement, preparing
the unit to a new charge of new
gas and ensuring the absence of
humidity in the interior
Refrigerant bottle
For the operations of new charge
of gas after repairs or
components replacement
Electronic balance
For the purposes of a new gas
charge, control the correct
amount of refrigerant to the
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1) Double stage vacuum
2) Solenoid valve
3) Handle with exhaust of
purged air
4) Vacuum gauge (relative)
5) Oil level sight glass
6) Oil mist filter
7) 3/8” hose connection
8) Vacuum pump 198 L/min
(7 CFM)
9) Vacuum pump oil
container (different sizes)
Brush / cleaning tools
1) steel brush
Inner and outer cleaning and
finishing works of soldering
Cleaning / protection sprays
sprays for disinfection: to
pulverize in the evaporator
fins, avoiding the deposition of
bacteria’s in the air flow way
spray to retire dirtiness, grass
and other elements from fins
Gas leakage detectors
Electronic leak detector for HC
Reversible ratchet handle
To remove magnesium
anode and replace it.
Anode Control Tester*
To measure anodic current.
Value must be > 0,3 mA
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Sensitivity less than 50 ppm
(Propane, Iso-Butane,
1) Flexible metal probe with
2) Keypad
only for measurable type anodes
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Testing equipment
- Electronic thermometer
- sensor probes to detect
temperatures in the circuit
1) Electronic thermometer
for up to two probes,
measuring range –50°C to
2) Electronic thermometer
equipped with three probes
3) Electronic hand
thermometer with one
probe, measuring range –
50°C to 150°C
Digital clamp on meter
Non contact ampere
measurement, voltage and
resistance measurement
LCD display and holding function
for easy reading
1) Ampere measuring
2) LCD display
3) Measurement selector 4)
Test leads
Digital multimeter
1) Measurement selector
2) Test leads
Tests batteries, capacitors and
resistors components, as well,
continuity’s in sensors, etc.
Anemometer and thermometer
Air velocity measurement for air
Sound level meter
Measuring of sound level on
refrigeration and AC equipment
Measuring range 40 to 140 dB
1) Vane sensor with
integrated thermometer
2) Measuring device for
temperature and air velocity
1) Sensor
2) Digital display
3) Key pad
Scaling liquid Kaloxi
Used to decaling purposes
in the condenser heat
TTNR: 8 709 918 413
Used to lubricate o’rings in
contact with water
Thermal paste
TTNR: 8 719 918 658
To use in NTC sensors of
contact type to improve
Table 10 – List of material for safety, handling and repairs
Bosch, Termotecnologia S.A
TT-DW/STI – International training and technical support - Aveiro Plant
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