Kitchen Ventilation Systems.pdf

KITCHEN VENTILATION SYSTEMS BY THOMAS E CARTER

KITCHEN VENTILATION SYSTEMS by Thomas E. Carter

Copyright © 1997 by Vent Master All rights reserved. The use of any or part of this publication reproduced, transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise stored in a retrieval system, without the written permission of the publisher is an infringement of copyright law. Canadian Cataloguing in Publication Data Vent Master A Division of Garland Commercial Ranges Limited ISBN 0-921501-32-3 I. Title. II. Series Written by: Editor: Consulting editor:

Thomas E. Carter A. W. Cockerill Charlotte Brewer, M.A. (Oxon.)

Vent Master 1021 Brevik Place Mississauga, ON L4W 3R7 Canada Tel: Fax: U.S.A. to Canada: Fax: U.S.A. to Canada: Publishing history First printed September 1995 Reprinted January 1996 Revised and reprinted 1997

905-624-0301 905-624-5547 1-800-565-2981 1-800-665-2438

Contents Page Foreword Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

Hoods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11

Grease Removal Devices . . . . . . . . . . . . . . . . . . . . . . . .

23

Ducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

29

Air Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

35

Auxiliary Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . .

45

Fire Protection Equipment . . . . . . . . . . . . . . . . . . . . . . .

55

Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

61

Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

75

Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

79

Codes and Equipment Specifications . . . . . . . . . . . . . . .

105

Trouble Shooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

133

Engineered Features . . . . . . . . . . . . . . . . . . . . . . . . . . . .

141

Metric Conversion Chart . . . . . . . . . . . . . . . . . . . . . . . .

149

Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

151

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

153

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

155

Foreward This book is for architects, engineers, kitchen designers, contractors, inspectors and others who install, inspect, operate, maintain or service commercial kitchen ventilation systems. Its purpose is to explain the elements of cooking equipment ventilation in plain English. It discusses four main topics: C

The factors that shape and define a ventilation system specified by the kitchen designer;

C

Circumstances that change the selection criteria;

C

Where one type of system ends and another begins; and

C

Building codes, fire and environmental regulations that govern ventilation systems.

Contractors and service personnel will find here a concise summary of installation requirements, operating, cleaning and maintenance procedure. The book makes frequent reference to the National Fire Prevention Association 96 (commonly known as NFPA96) Standard, which many jurisdictions use as a basis on which to inspect and approve kitchen installations. The influence of the NFPA 96 Standard on the layout and content of the book is readily acknowledged. Without the clear and concise treatment the Standard gives to kitchen ventilation technology, the task of writing the book would have been considerably more difficult than in fact it proved to be. The book will help users avoid the costly mistakes sometimes made in choosing a ventilation system. It should also answer many of the questions clients frequently ask architects and designers, including: C

How can I get the most efficient system at the least cost?

C

What are the available options?

C

Where can we get expert advice without making a contractual commitment?

C

Can we exhaust to the side of the building?

C

Will a single ventilation system satisfy a multi-restaurant site?

C

Is there a generic technical specification to cover everything we need to specify in a system?

C

What does “labelled product” mean and what’s important about it?

C

How stringently do building inspectors apply the NFPA96 Standard?

I sincerely hope that those who use the book will find sound, useful and practical advice in it to apply to their work in kitchen ventilation technology. I purposely intended to discuss ventilation technology in a generic sense although, admittedly with without apology, there is frequent reference to the products of Vent Master, one of the foremost leaders in the kitchen ventilation equipment field. Thomas E. Carter Maplewood, NJ

Introduction

More than 5000 years ago, the Egyptians built ventilation shafts into the pyramids to provide artisans working in the vaults and passageways with a constant supply of cool, fresh air. Visitors to the pyramids at Giza still benefit from the built-in ventilation system of the ancient builders when they are inside the massive structures. Without that cooling ventilation, the atmosphere in the dimly lit passageways and tunnels would soon become exceedingly stale and stifling. Good ventilation is important for the comfort of occupants in any enclosed space. In commercial kitchens with banks of ovens, grills and fryers, adequate ventilation is essential to deal with the effects of heat, smoke, odors, pollutants and numerous airborne contaminants. Without adequate ventilation, cooking operations in confined spaces would be impossible. The degree of ventilation a given kitchen space requires depends on various factors: the type of operation being conducted; the structure in which the kitchen operates; the type of equipment in use; the heating source; applicable regulations and ecology requirements. About this book A number of factors govern the efficiency and reliability of kitchen ventilation systems. They include installing the right equipment for the job, good operating practices and regular maintenance. Users will find this practical illustrated guide helpful whether they are dealing with kitchen design, the selection of equipment, its installation, operation or servicing. It tells you the `what' and the `why' of Vent Master equipment. Its primary purpose is to serve users as a source of reference that neither product literature nor codes can provide.

7

How the book is organized This book follows the pattern of chapters used in the NFPA 96 Standard regarding chapter headings and topics within chapters. There are two reasons for this. First, those familiar with NFPA 96 will find a logical sequence in the treatment given to the separate aspects and parts of ventilation systems. Secondly, for cross referencing purposes, users familiar with NFPA 96 will find the parallel treatment of chapters and topics easy to follow. Discussing the topics of kitchen ventilation in the same sequence as the NFPA 96 Standard changes the way in which we cover major items of ventilation equipment. For example, under Hoods we discuss the physical aspects of hoods - the backshelf hood, the canopy type - and calculations for sizing them. Airflow in and around hoods, however, is in the section dealing with Air Flow. Similarly, separate chapters cover installation, operating and maintenance procedures. The treatment by topics to conform with the NFPA 96 Standard chapters ends at the Design Section. In NFPA 96, Chapter 12 is a bibliography under the heading Reference Publications. In our Design Section we deal with kitchen design criteria not covered anywhere else in the book. This book also includes three appendices and an index, which the Standard omits. How to use it The best way to use this manual is to know where to look for the information you need. That is, for general information, consult the Contents page, which lists the subject: Hoods, for example. For more detailed information, refer to the Index, which lists topics and sub-topics in alphabetical order. Regarding the use of abbreviations, the first time an abbreviated term or phrase is used it is written in full, followed by the abbreviated letters given in brackets. For example, Vent Master is followed by (VM). Thereafter, VM is used and means Vent Master.

8

Three important words To use this book well, understand the meaning of WARNING, CAUTION and NOTE as used in VM shipping, unpacking, and installation procedure. They are written for your health and safety. A WARNING means that if you do not follow the instruction procedure you might injure yourself or anyone working with you. VM uses a warning notice only when there is risk to the safety of service personnel. A CAUTION means that if you do not follow the written procedure you might damage the equipment or component with which you are working. VM uses a CAUTION only when there is risk of damage to the equipment or a component. A NOTE gives information that is useful for you to know. A NOTE is not an instruction, but is offered to help you understand more about the equipment. The importance of ventilation Ventilation is the single most important factor in the design, construction and operation of commercial kitchens. Without adequate ventilation and an ample supply of clean air, no kitchen can operate efficiently. To ensure a kitchen is well ventilated, the designer must consider these factors: National, regional and local building codes are becoming increasingly more stringent. Environmental standards are being revised to require clean exhaust air. Rising costs drive the industry to find innovative ways of providing competitive installation, start-up and operating solutions.

9

The sites illustrated in the examples are typical of the ventilation problems with which kitchen designers, renovators and equipment suppliers can be faced. There is no single solution for all of these problems. We believe, however, that Vent Master has the equipment to provide the flexibility required to solve the problems found in the wide variety of kitchen sites. These are some of the kitchen ventilation problems this book seeks to revolve. A word in closing, however, on the kitchen equipment for which the designer must provide sufficient ventilation. Cooking equipment The type of cooking operation and the equipment used has a direct bearing on the ventilation system required. Some kitchens use more energy than others simply because of the type of cooking done. For example, kitchens in which grills, charbroilers and fryers are in use generate more heat than kitchens specializing in the preparation of light meals, snacks, soups and casseroles. Grills, fryers and charbroilers release high levels of pollutants. Ovens used for cooking pizzas release bursts of intense heat when their doors are opened. The hot air released by ovens, however, carries into the kitchen atmosphere considerably less particulate matter and grease than open-top cooking.

10

Hoods

Hoods

A hood is the primary device used to collect vapors, pollutants and airborne residues from cooking operations to funnel them into the ventilation system. The closer the hood is to the cooking surface, the griddle plate, oven top and broiler, the more efficiently it will collect the generated heat and particulate matter to channel into the ventilation system. From a practical viewpoint, however, a hood cannot be so close to the cooking surface that it hinders the kitchen staff in doing their work. Hood nomenclature Over the years, a common terminology has evolved in hood types and nomenclature. Common terms include the backshelf hood, the canopy hood, make-up air and the abbreviations CFM, SP and FPM, as shown in Figure 7.. Make-up air means the supply of air from an exterior source to replace the air ventilated from the kitchen. The hood is only one component of a kitchen ventilation system, but an important one whose size is determined by the size and capacity of the cooking equipment being used. The capacity of the system is expressed in cubic feet per minute (cfm). Three factors determine capacity: 1. The type of cooking appliances in use: fryers, ovens, broilers, steam kettles, etc. 2. The type of heating source: gas, steam, electricity, or a combination of these. 3. The barriers to air flow: building walls, fabricated enclosures. These factors define the velocity and rate of expansion of the air in the generated up-draft. For example, cooking appliances with large, open heated surfaces, such as grills and broilers, create stronger up-drafts than an 11

Ventilation Systems oven, which is built to contain the heat it uses. Gas and solid fuel-burning appliances lose most of the energy they produce. This waste heat generates stronger thermal currents than equipment heated electrically or with steam. Walls, fabricated enclosures and the type of hood used affects the volume of exhaust air needed. Hot air rising from the cooking equipment induces the surrounding air; i.e., the faster the hot air rises the more the surrounding air is drawn in to replace it. Therefore the more air is required on all open or exposed sides of the hood. Another feature of ventilation systems is that the more enclosed the cooking operation, the less the exhaust air needed to ventilate it. An appliance open on all sides requires a larger volume of exhaust air than when only one side is open. Although there are many variants of the backshelf and the canopy-type hoods, it is the cooking equipment that determines which type of hood best suits the application. Figure 8 shows a low cooking surface appliance for which the backshelf hood is well suited. The backshelf hood is sometimes called a ”low-profile wall” or ”up-draft hood”. A backshelf hood in close proximity to the cooking surface requires less exhaust air than is required by a canopy hood for the same application. This makes the backshelf hood an efficient choice for this service. The range of clearances from the cooking surface to the top of the hood and from the floor to the hood ducting is fairly restricted. The backshelf hood is not suitable for tall appliances or operations that produce large volumes of smoke or steam. For such applications a canopy hood (see Figure 9) is essential. A canopy hood requires a larger volume of exhaust air than a backshelf hood. Conversely, a canopy is suitable for ventilating any type of cooking operation, its main advantage being its flexibility. By flexibility is meant that, being open on all sides, the hood can be positioned anywhere in the cooking space that is not adjacent to a wall. The construction of a backshelf hood requires it to be positioned and fitted where it was designed to go. It cannot be repositioned without modification.

12

Hoods Exhaust air velocity An air velocity of 50 fpm is the minimum required to contain a rising thermal column and capture suspended particulate matter released by cooking operations. This minimum velocity is called the “capture velocity.” The capture velocity does more than arrest released cooking particulates. It provides a minimum flow of air across the cooking surface to ventilate the appliance. A velocity less than the capture velocity results in appliance overheating problems. Higher levels can remove too much heat and cause the cooking temperature of the appliance to fluctuate. Calculating exhaust volumes Once the cooking equipment layout, hood type, size and number of exposed sides of the hood are known, calculate the required exhaust volume by adding the lengths of the open sides, as shown in Figure 10. The three figures combined in Figure 11 overleaf show possible combinations of open and closed sides found in kitchen designs. Multiply the total length of the open sides by the distance from the cooking surface to the bottom of the hood (see Figure 12). The product in square feet is the captive area. Next, multiply the captive area in sq. ft. by 50 to get the captive velocity. Finally, referring to Table 1, shown overleaf, add or subtract the cfm correction factors according to the actual appliances in the cooking configuration. Sizing a hood There are three areas to consider when sizing a hood. C

The cooking equipment layout. It is necessary to measure the length and depth of the cooking bank. Most applications require a 6” overhang on each side of the open cooking surface. The exception is with charbroilers, for which a 12” overhang is used. Therefore, add 6” to each measurement obtained and, if the hood is for a charbroiler, add 12”.

13

Ventilation Systems

W1

W2

W

Length of open sides (LT) = L + W1 = W2

L

L Length of open sides (LT) =L+W

Type 1 - open sides and front

Type 2 - One side and front open CFM correction factors Equipment

+225

Fryers

+75

+50

Tilting skillets

+150 +150

+150 +150

Conv. broilers

+150

-

Live charcoal broilers

+350

-

Mesquite broiles

+350

-

Salamanders

Type 3 - Open front

Ovens

Figure 11 - Combination of open and Closed sides

C

Elect. Equip.

Broilers Griddles

L Length of open side (LT) = L

Gas Equip.

+150

+50 +300

-300

+300

-200

Note: There is no correction factor for kettles, steamers or burner ranges.

Table 1 - Correction factors

The wall locations. Determine the wall locations around the hood perimeter. For example, if the cooking equipment is against the back wall and in a corner, the hood would require a 6” overhang on the front of the cooking bank and a 6” overhang on one end of the bank only.

C

The structural height limitations. The ceiling clearance determines the height of the hood when tapers are required. For example, with a 24” high filter hood and mounting the hood 6'6” above the finished floor line, the top connection of the exhaust duct collar would be 8'9” above the finished floor. Adding a 10” duct and 3” minimum clearance between the duct and the underside of the building structure would give a required height of 9'10”. If the building structural height is only 9', the GLD hood section would require a 10” taper.

The points to remember when sizing hoods are: 1. Hood lengths are measured in increments of 6”. Therefore, if an 8'3” long hood is required to give a required 6” overhang, we recommend that the hood be built at 8'6”. An 8'3” long unit would cost the same as an 8'6” 2.

dimension. Hoods with odd dimensions can be and often are produced. For example, 14

Hoods end walls on both sides of a hood may give a dimension of 8'5”. A clearance of 1” should be allowed on either side to make sure the hood will 3.

fit into the space with ease. This would make the hood length 8'3”. The standard depth of a VM hood is 4'. The smallest available depth is 3'. If the cooking bank requires a 3'6” deep hood it is better to use a 4' deep hood as this will increase the capture area, give improved smoke control

5.

and will not change the cfm requirements for the cooking bank. All exhaust hoods can be tapered, but VM does not recommend a taper in excess of 12”. Always consult the factory if special tapers are required. When tapering an exhaust canopy, remember that it is usually mounted

6.

with the front lip 6'6” above the finished floor. There is no minimum height code requirement, although VM recommends a minimum height of 6'3” to provide adequate working clearance and head room. Always check the height of the cooking equipment below the hood when

4.

tapering any hood section. If a hood is tapered 12” and the hood front mounted 6'6” above the finished floor, the back of the hood will be 5'6” above the floor. This means that, as salamanders and cheese melters typically stand at a height of 5'10”, they cannot be accommodated under

7.

such a hood. Instead, they would need to be wall-mounted either lower over the cooking equipment or off to the side of the bank, requiring a 3' extension onto the hood length. When sizing island canopies, take into account the fact that cooking equipment mounted back to back requires service space or a service chase between the two banks. An example of hood sizing for an island cooking operation is this: a cooking bank arrangement with steam equipment on one side, heavy duty cooking on the other, and a 12” service chase in between might have a face-to-face dimension of between 7 and 8'. This requires a hood of 8 - 9' depth to give the required 6” overhang. If, however, the bank includes a charbroiler, an additional 6” is required to provide

8.

the specified 12” overhang. For the minimum requirements, note that a single hood section can be built to a maximum length of 16'. Beyond this length, VM banks hood sections side by side. With this, the length of the hood section is not limited. It could be 20' long or 100'. 15

Ventilation Systems 9.

The cooking equipment determines the dimensions of the hood. Once this is known, the hood can be banked, tapered or custom-built to suit the space.

Figure 13 is the section view of a kitchen ventilation system of an actual installation. This shows a back-to-back arrangement of cooking equipment for which one side requires an air flow capacity of 150 cfm/ft. and the other 300 cfm/ft.

Canopy-filter type hoods The canopy-filter type hood uses a UL listed grease filter to remove contaminants from the air as it exhausts through the canopy. The filter comprises a series of baffles that change the direction of the air flow. The centrifugal force acting on the particles in suspension causes them to collect on the stainless steel baffles and drop into a collection tray, as illustrated in Figure 14. The grease collection cups in the grease trays of filter hoods need to be emptied regularly so as not to pose a fire hazard.

16

Hoods

Terms and Conditions Pollution contaminates the environment and decreases the purity of air, land and water in various ways. This report is a commentary on the environmental condition of the atmosphere as it affects commercial kitchen operations. It explains filtration terms and conditions with which architects and kitchen designers need to be familiar when dealing with kitchen ventilation systems. In a healthy environmental atmosphere, the air we breathe is made up of 78% nitrogen and 21% oxygen. The remaining 1% consists of various gases and impurities. Figure 15 overleaf illustrates these proportions. The constituent elements of the 1% component consist of three groups: trace gases, variable gases, and atmospheric impurities. These are present in roughly equal proportions. Bi-product aerosols from commercial kitchen operations can raise the impurities present in the air above the nominal 1% value illustrated in Figure 16.

17

Ventilation Systems

The large circle of this illustration represents about 1 per cent of the air we breathe. Three constituents make up this 1 per cent: trace gases, variable gases, and atmospheric impurities For striking comparison, Figure 17 shows various sizes of aerosols in relation to a strand of human hair, which is about 150 microns in size. Aerosols of the smallest size (0.3 to 1 micron) such as tobacco smoke, cooking oil, and perfumes are easily detected by one's sense of smell. The smaller the size the higher the degree of filter or ventilation equipment efficiency needed to deal with the aerosol. An aerosol is a suspension of microscopic liquid or solid particles in the air. It is the function of any kitchen ventilation system to reduce the aerosols in a kitchen atmosphere to a minimum. Aerosols (or particles) are measured in microns. A micron is one millionth of a meter (1/25,400 inch). Under SI (System International) units of measure, micrometre is beginning to replace the word micron. In the U.S. filter industry, micron (abbreviated Fm) is the term in common usage. Figure 18 is a tabulation of particle size distribution in the atmosphere. Architects and kitchen designers will find the particulate size and element comparison chart shown in Figure 19 a useful source of reference for a variety of particulates. Some clients require technical specifications to cover various types and sizes of particulates.

18

Hoods

Average particle size (microns)

Per cent by weight

Per cent by particle count

Particle size (microns) 30

20

0.005

28 10

7.5

0.175

52

5 4

0.25

11

2

1.07

6

0.5

98.5

3

3 1 0.0

Source: NAFA "Guide to Air Filtration"

Figure 18 - Particle size distribution in atmosphere

0.01

0.1 2

3

4

5 6 7 89

1.0 2

3

4

5 6 7 89

10 2

3

4

5 6 7 89

100 2

Plant

3

1000

4

5 6 7 89

2

3

4

5 6 7 89

4

5 6 7 89

2

3

4

5 6 7 89

Pollen Mold Carbon black Bacteria

Animal

Asbestos

Mineral

Coal dust Textiles Cement dust Smoldering or flaming cooking oil

Combustion

Burning wood Auto emissions Air freshener

Home care

Humidifier Insecticide dusts Face powder Copier toner

2

0.01

3

4

5 6 7 89

2

0.1

3

4

5 6 7 89

2

3

1.0

4

5 6 7 89

2

3

10

100

1000 Source: ASHREA

Figure 19 - Particle size and element comparison chart

19

Ventilation Systems Some technical specifications specify a media velocity of something less than the face velocity. Figure 20 shows how a pleated panel filter achieves this reduced media velocity. Although more expensive, the pleated panel filter is more efficient and has a longer life than an equivalent panel filter because the media velocity can be reduced by as much as 50% of the face velocity. The four diagrams shown in Figure 21 illustrate various ways in which the filter media captures particles. They show the difference between impingement, interception, straining and diffusional effect.

20

Hoods Terms and Definitions Dust is dry particles of matter predominantly larger than colloidal size and capable of temporary gas suspension. Dust is generated from the reduction of larger, solid materials. The action of a jackhammer drilling rock creates dust; volcanic eruptions discharge lava dust (also called ash) into the air. Dust varies in size from 25 microns. Larger dust particles settle rapidly. Smaller particles stay in suspension longer and settle more slowly. Airborne dust under