CKV Design Guide
Design Guide 2
Improving Commercial Kitchen Ventilation System Performance
Optimizing Makeup Air
This design guide provides information
that will help achieve optimum performance and energy efficiency in
Introduction
commercial kitchen ventilation sys-
An effective commercial kitchen ventilation (CKV) system requires bal-
tems. The information presented is
applicable to new construction and, in
ance—air balance that is. And as the designer, installer or operator of the kitchen
many instances, retrofit construction.
ventilation system, you may be the first person called upon to perform your own
The audience for this guideline is
“balancing act” when the exhaust hood doesn’t work. Unlike a cooking appliance,
kitchen designers, mechanical engi-
which can be isolated for troubleshooting, the exhaust hood is only one component
neers, food service operators, property managers, and maintenance peo-
of the kitchen ventilation system. To further complicate things, the CKV system is a
ple. This guide is intended to augment
subsystem of the overall building heating, ventilating and air-conditioning (HVAC)
comprehensive design information
system. Fortunately, there is no “magic” to the relationship between an exhaust hood
published in the Kitchen Ventilation
and its requirement for replacement or makeup air (MUA). The physics are simple:
Chapter in the ASHRAE Handbook on
HVAC Applications as well as Design
air that exits the building (through exhaust hoods and fans) must be replaced with
Guide No. 1: Commercial Kitchen
outside air that enters the building (intentionally or otherwise). The essence of air
Ventilation – Selecting & Sizing Ex-
balance: “air in” = “air out!”
haust Hoods. Design Guide 2 was
previously published by the California
Energy Commission under the title
Improving Commercial Kitchen Venti-
Background
If the replacement air doesn’t come in, that means it doesn’t go out the exhaust hood and problems begin. Not only will the building pressure become too
lation Performance.
“negative,” the hood may not capture and contain (C&C) cooking effluents due to
reduced exhaust flow. We have all experienced the “can’t-open-the-door” syndrome
Introduction
1
because the exhaust fan is sucking too hard on the inside of the restaurant. The me-
Background
1
chanical design may call for 8000 cubic feet per minute (cfm) of air to be exhausted
Kitchen Ventilation Fundamentals
2
through the hood. But if only 6000 cfm of outdoor air is able to squeeze in through
Influence of Makeup Air
5
closed dampers on rooftop units and undesirable pathways in the building envelope,
MUA Recommendations
6
Influence of Other Factors
9
Energy Saving Considerations
6
then only 6000 cfm is available to be exhausted through the hood. The exhaust fan
creates more suction (negative pressure) in an unsuccessful attempt to pull more air
through the hood.
There is no piece of equipment that generates more controversy within the
Design Guide Summary
12
food service equipment supply and design community than the exhaust hood in all its
Case Study
13
styles and makeup air combinations. The idea that by not installing a dedicated
Improving Commercial Kitchen Ventilation System Performance
makeup air supply, the operator is going to save money (in both first cost and operating cost) is short sighted. It may be okay if, by design, all of the makeup air can be
provided through the rooftop HVAC units (this strategy has been adopted successfully by several leading quick-service restaurant chains). However, in full-service and
institutional kitchens with larger exhaust requirements, it may not be practical (or
energy efficient) to supply 100% of the replacement (makeup) air through the building HVAC system.
The solution is to specify an independent makeup air supply. But, once
dedicated MUA has been added to the system, the challenge becomes introducing
this air into the kitchen without disrupting the ability of the hood to capture and/or
without causing discomfort for the kitchen staff. Kitchens are not large and dumping 7000 cfm of MUA, for example, in front of a cook line does not go as smoothly
in practice as it does on the air balance schedule! Not only can makeup air velocities
impact the ability of the hood to capture and contain cooking effluent, locally supplied makeup air that is too cold or too hot can create an uncomfortable working
environment. This design guide presents strategies that can minimize the impact
that the makeup air introduction will have on hood performance and energy consumption.
Fundamentals of Kitchen Ventilation
Hot air rises! An exhaust fan in the ceiling could easily remove the heat
produced by cooking equipment. But mix in smoke, volatile organic compounds,
grease particles and vapor from cooking, a means to capture and contain the effluent is needed to avoid health and fire hazards. While an exhaust hood serves that
purpose, the key question is always: what is the appropriate exhaust rate? The answer always depends on the type (and use) of the cooking equipment under the
hood, the style and geometry of the hood itself, and how the makeup air (conditioned or otherwise) is introduced into the kitchen.
Cooking appliances are categorized as light-, medium-, heavy-, and extra
heavy-duty, depending on the strength of the thermal plume and the quantity of
grease and smoke produced. The strength of the thermal plume is a major factor in
determining the exhaust rate. By their nature, these thermal plumes are very turbulent and different cooking processes have different “surge” characteristics. For example, the plume from hamburger cooking is strongest when flipping the burgers.
Ovens and pressure fryers may have very little plume until they are opened to remove food product. Open flame, non-thermostatically controlled appliances, such
Design Guide 2 – Optimizing Makeup Air – Updated 03.15.04
2
Improving Commercial Kitchen Ventilation System Performance
as underfired broilers and open top ranges, exhibit strong steady plumes. Thermostatically controlled appliances, such as griddles and fryers have weaker plumes that
fluctuate in sequence with thermostat cycling (particularly gas-fired equipment). As
the plume rises by natural convection, it is captured by the hood and removed by
the suction of the exhaust fan. Air in the proximity of the appliances and hood
moves in to replace it. This replacement air, which originates as outside air, is referred to as makeup air.
The design exhaust rate also depends on the hood style and design features.
Island Canopy
Wall-mounted canopy hoods, island (single or double) canopy hoods, and proximity
(backshelf, pass-over, or eyebrow) hoods all have different capture areas and are
mounted at different heights relative to the cooking equipment (see Figure 1). Generally, a single-island canopy hood requires more exhaust than a wall-mounted hood,
and a wall-mounted hood requires more exhaust than a proximity hood. The performance of a double-island canopy tends to emulate the performance of two backto-back wall-canopy hoods, although the lack of a physical barrier between the two
hood sections makes the configuration more susceptible to cross drafts.
Double-Island Canopy
Lastly, the layout of the HVAC and MUA distribution points can affect
hood performance. These can be sources that disrupt thermal plumes and hinder
capture and containment. Location of delivery doors, service doors, pass-through
openings and drive-through windows can also be sources of cross drafts. Safety factors are typically applied to the design exhaust rate to compensate for the effect that
undesired air movement within the kitchen has on hood performance.
CKV System Performance Testing
Wall-Mounted Canopy
The phrase "hood capture and containment" is defined in ASTM F-1704
Standard Test Method for the Performance of Commercial Kitchen Ventilation Systems as "the
ability of the hood to capture and contain grease-laden cooking vapors, convective
heat and other products of cooking processes.” Hood capture refers to these products entering the hood reservoir from the area under the hood, while containment
refers to these products staying in the hood reservoir and not spilling out into the
adjacent space. The phrase "minimum capture and containment" is defined as "the
conditions of hood operation in which minimum exhaust flow rates are just suffi-
Proximity (Backshelf)
cient to capture and contain the products generated by the appliance in idle or
heavy-load cooking conditions, and at any intermediate prescribed load condition."
Figure 1. CKV Hood Types.
The abbreviation “C&C” refers to the “minimum capture and containment” flow
rate as defined in ASTM F-1704.
Design Guide 2 – Optimizing Makeup Air – Updated 03.15.04
3
Improving Commercial Kitchen Ventilation System Performance
Performance testing in accordance with ASTM F-1704 at the CKV Laboratory in Wood Dale, IL, incorporates a schlieren flow-visualization system to verify
capture and containment. This system is a major breakthrough for visualizing thermal and effluent plumes from cooking processes. “Schlieren” is derived from the
German word for “smear.” A schlieren system presents an amplified optical image
(see Figure 2) due to the different air densities, similar to the mirage effect we see
over hot pavement.
Hood
Hood
Capture and
Containment
at 220 cfm/lf
Spillage
of Plume
at 165cfm/lf
Figure 2. Schlieren images
at different exhaust rates
per linear foot (lf).
Range Top
Range Top
(side view)
(side view)
Replacement (Makeup) Air Distribution
Air that is removed from the kitchen through an exhaust hood must be replaced with an equal volume of makeup air through one or more of the following
pathways:
ν
Transfer air (e.g., from the dining room)
ν
Displacement diffusers (floor or wall mounted)
ν
Ceiling diffusers with louvers (2-way, 3-way, 4-way)
ν
Slot diffusers (ceiling)
ν
Ceiling diffusers with perforated face
ν
Integrated hood plenum (see Figure 3) including:
1. Short circuit (internal supply)
2. Air curtain supply
3. Front face supply
4. Perforated perimeter supply
5. Backwall supply (rear discharge)
6. Combinations of the above
Design Guide 2 – Optimizing Makeup Air – Updated 03.15.04
4
Improving Commercial Kitchen Ventilation System Performance
Influence of Makeup Air on Exhaust Hood Performance
Makeup air that is supplied through displacement ventilation diffusers remote from the hood, perforated diffusers located in the ceiling as far as possible
Short Circuit
(Internal Supply)
from the hood, or as transfer air from the dining room generally works well if air velocities approaching the hood are less than 75 feet per minute (fpm). Makeup air introduced in close proximity to an exhaust hood has the potential, however, to interfere with the hood’s ability to capture and contain. The chances of makeup air affecting hood performance increases as the percentage of the locally supplied MUA
(relative to the total exhaust) is increased. In fact, the 80% rule-of-thumb for sizing
Air Curtain
airflow through a MUA unit can be a recipe for trouble, particularly if the exhaust
flow rate has been over-specified to start with.
Temperature of the locally supplied makeup air can also impact hood performance as air density (buoyancy) impacts the dynamics of air movement around
the hood. Generally, hotter MUA temperatures (e.g., 90°F) will affect hood per-
Face-Discharge
formance more adversely than cooler air (e.g., 75°F). In most temperate climates,
such as many areas in California, evaporative cooling is an effective method of
maintaining MUA temperatures within a range that is comfortable for kitchen staff
and does not hamper hood performance. However, the maintenance requirements
of evaporative coolers must be factored into the equation.
The primary recommendation for minimizing the impact that locally sup-
Perforated Perimeter
Supply
plied MUA will have on hood performance is to minimize the velocity (fpm) of the
makeup air as it is introduced near the hood. This can be accomplished by minimizing the volume (cfm) of makeup air through any one pathway, by maximizing the
area of the grilles or diffusers through which the MUA is supplied, or by using a
combination of pathways.
The first step in reducing the MUA requirement is to minimize the design
exhaust rate. This can be accomplished by prudent selection and application of UL
Listed hoods and taking advantage of the “exhaust flow” recommendations from
hood suppliers for the cookline under consideration. Exhaust hood manufacturers’
sales and engineering departments have a lot of experience that CKV design consultants can tap to help minimize the “safety factor” applied to exhaust rates.
The second step in reducing MUA flow is to take credit for outside air that
Rear Discharge (Back Supply)
Figure 3. Types of MUA
Supply Integrated with the
hood.
must be supplied by the HVAC system to meet code requirements for ventilating
the dining room. Depending on the architectural layout between the kitchen and the
dining room, it may be practical to transfer most of this air from the dining room to
Design Guide 2 – Optimizing Makeup Air – Updated 03.15.04
5
Improving Commercial Kitchen Ventilation System Performance
the kitchen. For example, if 2400 cfm of outdoor air that is being supplied to a 160seat dining room can be transferred to the kitchen, the local makeup air requirement
can be reduced accordingly.
Rather than supplying 80 to 90% of the exhaust rate through one makeup
air strategy, designers should make an effort to keep this ratio below 60% (obviously, the other 40% of the replacement air must be derived from another source
such as transfer air, another local strategy, or HVAC supply). Although this may
contradict past practice, it will be effective! Not only will hood performance be superior, the kitchen environment will benefit from the cooling contribution of the
“recycled” dining room air. It is important to realize that the outdoor air required by
code is usually conditioned before it is introduced into the dining room. So… why
not use this outdoor air as a makeup air credit?
The third step in reducing MUA flow is to select a configuration for introducing this local makeup air into the kitchen that compliments the style and size of
hood. If transfer air is not an option, consider a combination of makeup air strategies (e.g., backwall supply and perforated ceiling diffusers). This reduces the velocity
of air being supplied through each local pathway, mitigating potential problems with
hood capture. Effective options (at 60% or less) include front face supply, backwall
supply, and perforated perimeter supply. Short-circuit supply is not recommended,
and air-curtains should be used with extreme caution. The pros and cons of the different configurations are discussed below. Note a frequent theme⎯ minimizing
MUA discharge velocity is key to avoiding detrimental impacts on hood capture and
containment.
Short-Circuit Supply (Internal Makeup Air)
The application of short-circuit makeup air hoods is a controversial topic.
These internal makeup air hoods were developed as a strategy to reduce the amount
of conditioned air required by an exhaust system. By introducing a portion of the
required makeup air in an untempered condition directly into the exhaust hood reservoir, the net amount of conditioned air exhausted from the kitchen is reduced.
Research has shown however, that in the cases tested, internal MUA cannot be introduced at a rate that is more than 15% of the threshold C&C exhaust rate without
causing spillage (despite what is shown on the air balance schedule or marketing literature). When short circuit hoods are operated at higher percentages of internal
MUA they fail to capture and contain the cooking effluent, often spilling at the back
of the hood (although front spillage is observed in Figure 5). Dilution of the cookDesign Guide 2 – Optimizing Makeup Air – Updated 03.15.04
6
Improving Commercial Kitchen Ventilation System Performance
ing effluent with the internal MUA makes it hard to visualize spillage (even using a
schlieren system), but a degraded kitchen environment is confirmation that hood
performance has been compromised. If the design exhaust rate is significantly
higher than the threshold for C&C(i.e., includes a large safety factor), the percentage
of short-circuit air can be increased accordingly, creating a condition of apparent
benefit.
Short-circuit hoods are simply not recommended. This recommendation is
endorsed by leading hood manufacturers, even though they may still include shortcircuit hoods in their catalogue.
Figure 5. Schlieren image
shows the thermal plume
being displaced by short
circuit supply causing hood
to spill.
Air Curtain Supply
Introducing MUA through an air curtain is a risky design option and most
hood manufacturers recommend limiting the percentage of MUA supplied through
an air-curtain to less than 20% of the hood’s exhaust flow. The negative impact of
an air curtain is clearly illustrated in Figure 6 by the schlieren flow visualization recorded during a test of a wall-mounted canopy hood operating over two underfired
broilers.
An air curtain (by itself, or in combination with another pathway) is not
recommended, unless velocities are kept to a minimum and the designer has access
to performance data on the actual air-curtain configuration being specified. It is too
easy for the as-installed system to oversupply, creating higher discharge velocities
Figure 6. Schlieren image
shows the thermal plume
being pulled outside the
hood by the air curtain.
that cause cooking effluent to spill into the kitchen.
Front Face Supply
Supplying air through the front face of the hood is a configuration that has
been recommended by many hood manufacturers. However, a front face discharge,
with louvers or perforated face, can perform poorly if its design does not consider
discharge air velocity and direction. Not all face discharge systems share the same
design; internal baffling and/or a double layer of perforated plates improve the uniformity of flow. Face discharge velocities should not exceed 150 fpm and should
exit the front face in a horizontal direction. Greater distance between the lower capture edge of the hood and the bottom of the face discharge area may decrease the
Figure 7. Schlieren image
shows the thermal plume
being pulled outside the
hood by a poorly engineered front face supply.
tendency of the MUA supply to interfere with hood capture and containment.
Figure 7 represents a poorly designed face supply, which can negatively affect hood
capture in the same fashion as an air-curtain or four-way diffuser.
Design Guide 2 – Optimizing Makeup Air – Updated 03.15.04
7
Improving Commercial Kitchen Ventilation System Performance
Backwall Supply (Rear Discharge)
Lab testing has shown that the backwall supply can be an effective strategy
for introducing MUA (see Figure 8). However, the discharge area of the backwall
supply should be at least 12 inches below the cooking surfaces of the appliances to
prevent the relative high velocity introduction of MUA from interfering with gas
burners and pilot lights. As with other local MUA strategies, the quantity of air introduced through the backwall supply should be no more than 60% of the hood’s
exhaust flow. Hoods with a deeper plenum or increased diffuser area have lower
discharge velocities, allowing higher supply airflows. The back supply plenum may
Figure 8. Schlieren image
shows the thermal plume
being pulled captured with
backwall supply.
offer the advantage of meeting a “clearance to combustibles” code requirement. It
may also be an option to convert a single island canopy into a more functional wallmounted canopy (without actually constructing the wall) as utility distribution can be
incorporated within the plenum. If the rear supply utilizes perforated diffusers, it is
important that cleanout access be provided (as with any supply diffuser).
Perforated Perimeter Supply
Perforated supply plenums (with perforated face diffuser) are similar to a
front face supply, but the air is directed downward as in Figure 9 toward the hood
capture area. This may be advantageous under some conditions, since the air is directed downward into the hood capture zone. Face discharge velocities should not
Figure 9. Schlieren image
shows effective plume capture with MUA supplied
through a 16-in wide perforated perimeter supply.
exceed 150 fpm from any section of the diffuser and the distance to lower edge of
the hood should be no less than 18 inches (or the system begins to act like an air
curtain). Widening the plenum will lower the discharge velocity for a given flow of
MUA and reduce the chance of the supply air affecting C&C. If the perforated supply plenum is extended along the sides of the hood as well as the front, the increased area will permit proportionally more MUA to be supplied.
Four-Way Ceiling Diffusers
Four-way diffusers located close to kitchen exhaust hoods (see Figure 10)
can have a detrimental affect on hood performance, particularly when the flow
through the diffuser approaches its design limit. Air from a diffuser within the vicinity of the hood should not be directed toward the hood. Discharge velocity at the
Figure 10. Schlieren image shows the thermal
plume being pulled outside the hood by the air
discharged from a 4-way
diffuser.
diffuser face should be set at a design value such that the terminal velocity does not
exceed 50 fpm at the edge of the hood capture area. It is recommended that only
perforated plate ceiling diffusers be used in the vicinity of the hood, and to reduce
air velocities from the diffusers at a given supply rate, the more diffusers the better!
Design Guide 2 – Optimizing Makeup Air – Updated 03.15.04
8
Improving Commercial Kitchen Ventilation System Performance
Displacement Diffusers
Supplying makeup air through displacement diffusers at a good distance
away from the hood as illustrated in Figure 11 is an effective strategy for introducing
replacement air. It is analogous to low-velocity “transfer air” from the dining room.
However, the diffusers require floor or wall space that is usually a premium in the
commercial kitchen. A couple of remote displacement diffusers (built into a corner)
could help diversify the introduction of makeup air into the kitchen when transfer
air is not viable.
Figure 11. Schlieren image
shows the plume being
effectively captured when
makeup air is supplied at
low velocity from displacement diffusers.
Influence of Other Factors on Hood Performance
Cross Drafts
Cross drafts have a detrimental affect on all hood/appliance combinations.
Cross-drafts adversely affect island canopy hoods more than wall mounted canopy
hoods. A fan in a kitchen, especially pointing at the cooking area, severely degrades
hood performance and may make capture impossible. Cross drafts can also be developed when the makeup air system is not working correctly, causing air to be
pulled from open drive-through or pass-through windows or doors.
Side Panels and Overhang
Side (or end) panels (as represented in Figure 12) permit a reduced exhaust
rate in most cases, as they direct the replacement airflow to the front of the equipment. They are a relatively inexpensive way to improve capture and containment
and reduce the total exhaust rate. In fact, one of the greatest benefits of end panels
is to mitigate the negative effect of cross drafts. It is important to know that partial
side panels can provide almost the same benefit as full panels. Although tending to
defy its definition as an “island” canopy, end panels can improve the performance
of a double-island or single-island canopy hood.
An increase in overhang should improve the ability of the hood to capture,
although for unlisted hoods this may mean an increase in the code-required exhaust
rate. Larger overhangs are recommended for appliances that create plume surges,
such as convection and combination ovens, steamers and pressure fryers.
Figure 12. Illustration of
partial and full side panels.
Safety Factor in Exhaust Rates
Diversity in appliance use, hood reservoir size, as well as the fact that
maximum effluent generation from cooking only occurs randomly during normal
kitchen operations, may mask the detrimental influence of local MUA sources on
Design Guide 2 – Optimizing Makeup Air – Updated 03.15.04
9
Improving Commercial Kitchen Ventilation System Performance
hood performance. Consequently, spillage may be infrequent or simply unobserved.
However, better MUA designs allow reduced exhaust rates and minimized energy
costs while maintaining a margin of safety with respect to C&C.
Design Considerations for Energy Savings
Hood Style
Wall-mounted canopy hoods function effectively with a lower exhaust flow
rate than the single-island hoods. Island canopy hoods are more sensitive to MUA
supply and cross drafts than wall mounted canopy hoods. Engineered proximity
hoods may exhibit the lowest capture and containment flow rates. In some cases, a
proximity hood performs the same job as a wall-mounted canopy hood at one-third
the exhaust rate.
Hood Geometry
Interior angles close to, or at, the capture edge of the hood improve C&C
performance, allowing reduced exhaust by directing effluent back towards the filters.
Hoods designed with these better geometric features require as much as 20% less
exhaust rate compared to hoods identical in size and shape without these features.
Capture and containment performance may also be enhanced with active “low-flow,
high-velocity air jets” along the perimeter of the hood.
Variable Speed Fans and Idle Conditions
Appliances idle much of the day. Using two-speed or variable exhaust flow
rates to allow reductions in exhaust (and makeup) while appliances are idling would
minimize operating costs. NFPA 96 (Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations) was recently amended to allow minimum exhaust duct velocity as low as 500 fpm (at the exhaust collar and ductwork).
Typical design values of 1500 to 1800 fpm at the exhaust collar are still recommended for normal cooking conditions. This code change will facilitate the application of variable speed systems.
Energy Perspective
The exhaust ventilation system can be a major energy user in a commercial
kitchen – but it doesn’t need to be in temperate climates like California. Mild climates, such as San Diego, may require no heating or cooling. Some facilities may
cool replacement air to improve kitchen comfort. Combined heating and cooling
Design Guide 2 – Optimizing Makeup Air – Updated 03.15.04
10
Improving Commercial Kitchen Ventilation System Performance
costs for MUA range from $0.00 to $0.60 per cfm in California climates, assuming
16 hours per day for 360 days per year. California climates are mild compared to
other areas in North America so heating and mechanical cooling of MUA often is
not necessary. Evaporative cooling can be very effective in desert climates.
Rule-of-thumb figures are useful, but how can designers calculate the costs
based on a specific kitchen design and operation? The Outdoor Airload Calculator
(OAC) software, freely available for download (www.archenergy.com/ckv/oac) , is
the best tool for quickly estimating the energy use for different CKV design and operating strategies. Figure 13 illustrates the OAC program interface and output.
Figure 13. Sample output
from Outdoor Airload Calculator screen.
Design Guide 2 – Optimizing Makeup Air – Updated 03.15.04
11
Improving Commercial Kitchen Ventilation System Performance
Design Guide Summary
The strategy used to introduce replacement (makeup) air can significantly
impact hood performance and should be a key factor in the design of kitchen ventilation systems. Makeup air introduced close to the hood’s capture zone may create
local air velocities and turbulence that result in periodic or sustained failures in
thermal plume capture and containment. Furthermore, the more makeup air supplied (expressed as a percentage of the total replacement air requirement), the more
dramatic the negative effect.
The following design suggestions can improve the energy efficiency and
performance of commercial kitchen ventilation systems:
Figure 14. Don’t use
short circuit hoods.
ν
Group appliances according to effluent production and associated ventilation
requirements. Specify different ventilation rates for hoods or hood sections over
the different duty classification of appliances. Where practical, place heavy-duty
appliances such as charbroilers in the center of a hood section, rather than at
the end.
ν
Use UL Listed proximity type hoods where applicable.
ν
Hood construction details (such as interior angles and flanges along the edge) or
high-velocity jets can promote capture and containment at lower exhaust rates.
ν
Install side and/or back panels on canopy hoods to increase effectiveness and
reduce heat gain.
ν
Integrate the kitchen ventilation with the building HVAC system (i.e., use dining room outdoor air as makeup air for the hood).
ν
Maximize transfer air/minimize direct makeup air.
ν
Do not use short-circuit hoods (Figure 14). Use caution with air-curtain designs.
ν
Avoid 4-way or slot ceiling diffusers in the kitchen, especially near hoods.
ν
Diversify makeup air pathways (use combination of backwall supply, perforated
perimeter supply, face supply, displacement diffusers, etc.).
ν
Minimize MUA velocity near the hood; it should be less than 75 fpm.
ν
Use direct-fired MUA heating if heating is necessary. In most temperate climates, including much of California, design for no MUA heating.
ν
Consider evaporative MUA cooling in dry climates such as California.
ν
Consider variable or 2-speed exhaust fan control for operations with high diversity of appliances and/or schedule of use.
ν
Provide air balance requirements to avoid over- or under-supply of MUA.
ν
Require building air balancing and system commissioning as part of the construction requirements.
Design Guide 2 – Optimizing Makeup Air – Updated 03.15.04
12
Improving Commercial Kitchen Ventilation System Performance
Case Study: Wall-Mounted Canopy Hood
Challenge: Improve hood C&C and reduce ventilation energy
Off-the-Shelf Approach
1
An un-listed wall mounted canopy hood (20-
Standard Design
ft by 4-ft) without side panels: total exhaust
8,000 cfm. Four-way ceiling diffusers supplying air from the kitchen HVAC and MUA unit
are located about 2 feet from front and sides
of the hood.
Makeup Air Sources:
8000 cfm
• 1000 cfm from dining and kitchen HVAC
7000 cfm
unit (25 Ton refrigeration capacity),
• 7000 cfm from independent MUA (heat-
1000 cfm
ing only, ductstat set to 65°F) supplied
through 4-way ceiling diffusers.
Annual CKV energy cost (including MUA
conditioning and exhaust and MUA fan energy) estimated at $6000 ($0.75 per cfm) for
Sacramento, CA location (using $0.15/kWh
and $0.60 per therm).
Engineered Approach
A “listed” hood (20-ft by 4.5-ft each) with par-
Optimized Design
tial side panels for a total exhaust of 6,000
cfm. Maximized use of transfer air. Perforated ceiling diffusers away from the hoods
for the MUA supply.
Makeup Air Sources:
• 1500 cfm from kitchen HVAC unit (15
Ton, 7000 cfm total supply)
• 1500 cfm from dining HVAC unit (10
Ton, 5000 cfm total supply)
3000 cfm
6000 cfm
3000 cfm
• 3000 cfm from independent MUA (no
heating with evaporative cooling)
Annual CKV energy cost estimated at $2000
($0.25 per cfm) for Sacramento, CA location,
for a $4000 saving over standard design.
1 Hoods designed to meet exhaust levels required by building codes, but not listed by a certified laboratory in accordance with a recognized test standard. For identical
cooking equipment unlisted hoods typically require higher exhaust flows than listed hoods.
Design Guide 2 – Optimizing Makeup Air – Updated 03.15.04
13
Improving Commercial Kitchen Ventilation System Performance
Notes and Acknowledgments
Funding
California Energy Commission
Pacific Gas and Electric Company
1516 Ninth Street, MS-29
P.O. Box 770000 MCN6G
Sacramento, CA 95814-5512
San Francisco, CA 94177
(916) 654-4287
(415) 973-0106
www.energy.ca.gov/pier/buildings
www.pge.com
Research Team
Architectural Energy Corporation
Fisher Nickel, inc.
2540 Frontier Ave, Suite 201
12949 Alcosta Boulevard, Suite 101
Boulder, CO 80301
San Ramon, CA 94583
(800) 450-4454
(925) 838-7561
www.archenergy.com
www.fishnick.com
Research Labs
Commercial Kitchen Ventilation Laboratory
Food Service Technology Center
955 North Lively Blvd.
12949 Alcosta Boulevard, Suite 101
Wood Dale, IL 60191
San Ramon, CA 94583
(630) 860-1439
(925) 866-2864
www.archenergy.com/ckv
www.pge.com/fstc
Legal Notice
This design guide was prepared as a result of work sponsored by the Commission. It does not necessarily represent the views
of the Commission, its employees, or the State of California. The Commission, the State of California, its employees, contractors, and subcontractors make no warranty, express or implied, and assume no legal liability for the information in this report;
nor does any party represent that the use of this information will not infringe upon privately owned rights. This guide has not
been approved or disapproved by the Commission nor has the Commission passed upon the accuracy or adequacy of this information in this guide.
Architectural Energy Corporation, Boulder, CO, and Fisher-Nickel, inc., San Ramon, CA, prepared this design guide. The first
edition of this design guide was included as an appendix in the final CEC report titled Makeup Air Effects on the Performance of
Kitchen Exhaust Systems (CEC contract # 500-98-031) published December 2002. Updated editions of this design guide may be
downloaded from www.fishnick.com or www.archenergy.com.
© 2002 by the California Energy Commission. Permission is granted to reproduce this document in its entirely provided that this
copyright notice is included.
Design Guide 2 – Optimizing Makeup Air – Updated 03.15.04
14
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement