Kitchen Design, Ventilation and CxASHRAE Illinois Chapter

Jason Greenberg, P.E. and Frank Kohout, P.E.

June 9, 2020

Jason Greenberg, P.E.

jgreenberg@mgnce.com

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

fkohout@cyclone.energy

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