ashrae illinois chapter · 2020. 6. 16. · ten of those years was spent at mcdonald’s helping to...
TRANSCRIPT
Kitchen Design, Ventilation and CxASHRAE Illinois Chapter
Jason Greenberg, P.E. and Frank Kohout, P.E.
June 9, 2020
Jason Greenberg, P.E.
Chief Mechanical Engineer at MGN, Inc. in Oakbrook Terrace, IL. He is a licensed professional engineer in
multiple states and has been designing restaurants for over 20 years. Ten of those years was spent at
McDonald’s helping to drive energy efficiency and sustainability in restaurants. Jason has been an active
member in ASHRAE Technical Committee 5.10 for 15 years including 2 years as committee chair. He is
also active in ASHRAE Standing Standard Project Committee 154 and a past contributing member to NFPA
96. When Jason is not designing buildings, you can find him in a bowling alley either bowling or coaching
kids or taking pictures for fun or at an event.
Frank Kohout, P.E., BCxA
Director of Special Projects at Cyclone Energy Group in Chicago, IL. 29 years of HVAC design and
commissioning experience. During a 16-year career at McDonald's, acted as engineer of record for over
800 restaurants as well as developing and maintaining their global HVAC standards. Has been a member
of ASHRAE TC 5.10 and SSPC 154 Kitchen Ventilation committees since 2004, and has served as the
committee's Handbook Subcommittee Chair from 2007-2019.
Poll Questions#1-4
Technical Committee 5.10
Technical Committee 5.10 – Research
• UL 710 – Standard for Exhaust Hoods for Commercial Cooking Equipment
• UL 1046 – Standard for Grease Filters for Exhaust Ducts
• Appliance heat gain published in ASHRAE Fundamentals Chapter 18
• ASHRAE Standard 55 does not apply to commercial kitchens
Technical Committee 5.10 – Works in Progress
• Research Project 1778 (RP-1778)
• Heat and Moisture Load from Commercial Dishroom Appliances and Equipment
• Dishroom Ventilation Design Guide
• Commercial Kitchen Ventilation Design Guide
• Now seeking co-authors
Get involved!
https://www.ashrae.org/technical-resources/technical-committees
Let’s Start Here
CKV Design
Flowchart
Construction:
• Test and Balance
• Commissioning
Kitchen Hoods
Let’s Start with the Hood
Why? Because everything else in a CKV system is based on the hood!!!
• Important Details:
• UL vs Design Airflows
• UL tests with the appliance (usually a griddle) at the furthest location from the exhaust collar, using 73% lean ground beef patties.
• Typically, hoods in a CKV system see different applications
Different Types of Exhaust Hoods
Let’s Start with the Hood
What is involved in the specification of a hood• Type of Hood
• Cooking Duty (Temperatures – list tables of temps and appliances)
• Overhangs of 6 inches minimum front and sides unless side panels are utilized.
• Demand Control Kitchen Ventilation (DCKV)
• THE HOOD SHOULD "CAPTURE AND CONTAIN" ALL THE COOKING EFFLUENT.
•Hooded vs Unhooded
• For Unhooded, heat gain must be accounted for, and grease emissions must be below 5mg/m3
Appliance Type By Duty and Typical Exhaust
As an example - Canopy Hoods:
Light Duty - 200°F: Ovens, Steamers
• 150 – 200 cfm/lf of hood length
Medium Duty - 400°F: Electric Ranges, Griddles, Fryers, Conveyor (Pizza) Ovens
• 200 – 300 cfm/lf of hood
Heavy Duty - 600°F: Gas Ranges, Charbroilers, Wok Ranges
• 200 – 400 cfm/lf of hood
Extra Heavy Duty - 700°F: Solid Fuel Cooking
• +350 cfm/lf of hood
(See Chapter 34 of Applications, Tables 4 & 5)
Different Duty Appliances Under Different Hoods
Exhaust Hood Submittal Information
Side panels reduce
exhaust air requirement
Examples of Appliance Hood Overhangs
Optimizing Hood Design
• Talk to the owner
• Get involved in hood selection
• Do not settle for canopy hoods
• Reduction in CFM = Energy Saved
• Simple changes can have substantial impact
Do NOT leave it up to the kitchen designers
Codes and Standards• NFPA 96 is a Standard for Fire Protection
• Clearances• Safety
• UL 710, UL 1046, and UL 300 for the hoods and fire suppression
• IMC• In addition to fire safety, and addresses the building and its occupants.
• ASHRAE Standards• 154 - Ventilation for Commercial Cooking Operations• 90.1 - Energy Requirements and DCKV• 189.1 - Hoods over 2,000 cfm• 62.1 - Sources of replacement air
• Duct velocity• 1500 fpm vs. 500 fpm: Why 500 fpm?• Where did this originate?
• What about velocity and DCKV?• Still need 500 FPM at lowest fan speed
Space Pressurization
• Managing the space pressurization is one of the critical elements of CKV design and operation.
• Typically, the dining area is maintained at a pressure so that air is transferred from the dining into the kitchen.
• If the dining area is connected to other spaces, the HVAC design should prevent the transfer of air from the dining area to the adjacent areas.
• If the CKV system is for a freestanding restaurant, then the overall building – including the kitchen – should be positively pressurized.
• Hospitals maybe an exception
Example of CKV Space Pressurization
DCKV (Demand Control Kitchen Ventilation)
• What is it?
• The amount of air exhausted by the hood is varied based on the current cooking demand. The system should also vary the amount of corresponding make-up air.
• How is it accomplished.
• Hood plenum/duct temperature
• Room-to-duct temperature difference
• Smoke sensing
• Cooking surface activity
• Cooking surface temperature
• Surface temperature drops when foods is placed on cooking surface.
DCKV System
DCKV at Full Load Cooking DCKV at Part of No-Load Cooking
Types of DCKV Control Systems
Replacement Air
Replacement Air Options
• Into the room (Best)
• E.g. displacement ventilation, ceiling supply
• Most useful since the air can provide cooling
• At the hood (Good)
• E.g. perforated supply plenum
• Requires separate supply air system
• Internal to the hood (Not recommended)
• Commonly referred to as a “short circuit” hood
• Replacement air is limited to 10% of exhaust
• If conditioned air is used, then there is no benefit
Replacement Air
International Mechanical Code
508.1.1 Makeup air temperature.
The temperature differential between makeup air and the air in the conditioned space shall not exceed 10°F (6°C) except where the added heating and cooling loads of the makeup air do not exceed the capacity of the HVAC system.
TRANSLATION: Replacement air is exempt from tempering so long as the comfort cooling/heating system(s) can compensate for that additional load.
Avoid using the exception. It is less problematic to temper at the source.
Hood Replacement Air Options
Front Supply with too
much air being supplied
causing spillage.
Internal Supply with too much
air being supplied (more than
10%) causing spillage. Also note
the air begin supplied provides
no benefit to the room.
Front Supply operating as
intended – no spillage.
Poll Question #5
Replacement Air at the Hood
Heated in winter or not
tempered in summer
• About 50% of the make-up
air goes back into the kitchen
• Needs to be included in heat
gain calculations
• What about thermal
comfort?
Front Face Supply
100% heat gain to space
Replacement Air at the Hood
Cooled in summer or not heated
enough in winter
• The cool air sinks to the floor
• The cold air can cause grease
and water to condense out
of the airstream
• Grease can accumulate on
the floor
Replacement Air at the Hood
Space neutral temperature
• Ensures proper capture and
containment
• Does not add heat to the
kitchen
• Keeps the workers
comfortable
Replacement Air in the Room
What’s wrong with this picture?
Replacement Air in the Room
Simple Rule
Do not place 4-way diffusers within 10 feet of any hood.
Recommended Rule
Do not use directional diffusers of any type in a commercial kitchen.
Replacement Air in the Room
Do not use directional diffusers in
the kitchen
Replacement Air in the Room
Perforated Return Diffuser with Side Entry Plenum
• Good for limited ceiling
space
• Do not use with top entry
• Requires shop fabrication
Replacement Air in the Room
Laminar Flow Diffuser
• Varying designs from
different manufacturers
• Top duct connection
• More likely to be
installed correctly
Replacement Air in the Room
Fabric Diffuser
• Probably the least
expensive option
• Has a top connection
• Easily cleanable
• Aesthetics are a concern
• May obstruct views
Replacement Air in the Room
Example Layout:
• 2x4 diffusers with 4 ft. in
between
• Proximity to hoods is of
little concern
• Provides consistent
comfort throughout the
space
• Maximum recommended
face velocity of 200 FPM
Appliance Heat Gain
Appliance Heat Gain
35.21%
2.65%
19.35%
7.89%
34.90%
COOLING - WHOLE BUILDING
Envelope Lighting Equipment People Ventilation
0.17% 0.90%
32.64%
2.63%
63.66%
COOLING - KITCHEN ONLY
Envelope Lighting Equipment People Ventilation
Appliance Heat Gain
Front Counter Back-of-house
Appliance Heat Gain
Summary:
• ~26,000 Btu/h (2.2 tons)
front counter heat gain
• ~43,500 Btu/h (3.6 tons)
back-of-house heat gain
Sources:
• Manufacturer data
• ASHRAE Handbook Ch. 18
Appliance Heat Gain
Front Counter
26,000 Btu/h
40 Btu/h per sf
Back-of-house
43,500 Btu/h
85 btu/h per sf
Poll Question #6
Appliance Heat GainFront Counter Back-of-House System Design
Previous Project 600 CFM 700 CFM One (1) VAV
New Project 2,400 CFM* 1,950 CFM*
One (1) fan-powered box
dedicated to each space
Supplemental 3-ton
system for the back-of-
house when building
ventilation is turned off
* Project had north and west exposures. Previous project was completely interior.
Test & BalanceCommissioning
CKC Testing and Balancing Hoods
• ALWAYS ensure that the balancer is following the hood supplier's stated procedures for measuring their hood's exhaust airflow
• Velocity Grid
• 4-inch rotating vane anemometer
• Factory installed Pitot tubes
• Duct traverse is not typically employed since it involves penetrating the fire rated exhaust duct
CKV Testing with Smoke
• Using smoke to test for hood capture is not recommend as an acceptable test.
• Smoke candles are good for visualizing air currents and drafts, but they do not simulate real cooking
• Smoke bombs cause too much smoke – they do not simulate real cooking conditions.
• The best method to test a hood for capture and containment is with actual cooking.
CKV Test and Balance
• Confirm differential pressures between zones and outside, at minimum and at maximum flow rates
• Don’t do it on a windy day!
• Assure all doors are closed while doing the tests.
• All building HVAC is running, all sources of transfer air are operational
• Replacement airflow rate should compensate synchronously with each increment of exhaust
• Check pressure balance at each increment of speed change
• Adjustments in controls or in damper linkage settings may be needed
• Use data loggers to assure correct control sequences
CKV Commissioning
Commissioning goals:
• Verify hood proper capture and containment• During full load cooking• At all minimum and maximum flow
rates
• Verify control sequences work properly.• Replacement air interlocks• DCKV system (if applicable)• HVAC/Fire Suppression system
interlocks• Appliance/Hood Fan interlocks
• Verify proper space pressurization is maintained during all operating conditions
References
• ASHRAE Handbook – Fundamentals
• Chapter 18 – Non-Residential Heating and Cooling Load Calculations
• ASHRAE Handbook – HVAC Applications
• Chapter 34 – Kitchen Ventilation
• ASHRAE Std. 154 – Ventilation for Commercial Cooking Operations
• NFPA 96 – Standard for Ventilation Control