KITCHEN
VENTILATION SYSTEMS
BY
VENTILATION SYSTEMS
byAll 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: Thomas E. Carter
Editor: A. W. Cockerill
Consulting editor: Charlotte Brewer, M.A. (Oxon.) Vent Master 1021 Brevik Place Mississauga, ON L4W 3R7 Canada Tel: 905-624-0301 Fax: 905-624-5547 U.S.A. to Canada: 1-800-565-2981
Fax: U.S.A. to Canada: 1-800-665-2438
Publishing history
First printed September 1995 Reprinted January 1996 Revised and reprinted 1997
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
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
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 equip-ment, 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.
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.
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 competi-tive installation, start-up and operating solutions.
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 equip-ment 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.
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
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.
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 configura-tion.
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”.
W1 W2 Length of open sides (LT)
= L + W1 = W2 L
W
L Length of open sides (LT)
= L + W
L
Length of open side (LT) = L
Figure 11 - Combination of open and Closed sides
Type 1 - open sides and front Type 2 - One side and front open
Type 3 - Open front
CFM correction factors +225 +75 +150 +150 +150 +350 +350 +50 +300 +300 +150 +50 +150 +150 --300 -200 Broilers Fryers Griddles Tilting skillets Conv. broilers Live charcoal broilers Mesquite broiles Salamanders Ovens
Note: There is no correction factor for kettles, steamers or burner ranges. Equipment Equip.Gas Equip.Elect.
Table 1 - Correction factors
C 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” dimension.
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 fit into the space with ease. This would make the hood length 8'3”. 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 and will not change the cfm requirements for the cooking bank.
4. 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. 5. When tapering an exhaust canopy, remember that it is usually mounted
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.
6. Always check the height of the cooking equipment below the hood when 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 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.
7. 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 the specified 12” overhang.
8. 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'.
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.
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
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.
Pollen 2 3 4 5 6 7 89 0.01 0.1 1.0 10 100 2 3 4 5 6 7 89 2 3 4 5 6 7 89 2 3 4 5 6 7 89 2 3 4 5 6 7 89 1000 Plant Animal Mineral Combustion Home care Mold Carbon black Bacteria Asbestos Coal dust Textiles Cement dust Smoldering or flaming cooking oil
Burning wood Auto emissions Air freshener Humidifier Insecticide dusts Face powder Copier toner 2 3 4 5 6 7 89 2 3 4 5 6 7 89 2 3 4 5 6 7 89 2 3 4 5 6 7 89 2 3 4 5 6 7 89 0.01 0.1 1.0 10 100 1000 Source: ASHREA
Figure 19 - Particle size and element comparison chart
Particle size (microns) 30 10 5 3 1 0.0 Per cent by weight 28 52 11 6 3 Per cent by particle count 0.005 0.175 0.25 1.07 98.5 Average particle 20 size (microns) 7.5 4 2 0.5
Figure 18- Particle size distribution in atmosphere
Source: NAFA "Guide to Air Filtration"
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.
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 <0.1 to >25 microns. Larger dust particles settle rapidly. Smaller particles stay in suspension longer and settle more slowly. Airborne dust under <0.1 behaves like a gas and has no rate of fall, but is affected by Brownian movement*. This is the random movement of particles caused by statistical pressure fluctuations over them.
Particles in the range of 0.1 to 1 micron have negligible settling velocities. Particles in the 1 to 10 micron range have a constant and appreciable settling rate, but are kept in suspension by air currents. Particles in excess of 10 microns settle out of the atmosphere.
Fumes are particulate matter consisting of the solid particles generated by
condensation from the gaseous state. Generally, this occurs after the volatization from melted substances, often accompanied by a chemical reaction such as oxidization. Arc welding fumes are typical of this chemical action. Heat from the electric arc vaporizes some of the rod and its coating.
Fog is the condensation of water vapor in the air in sufficient concentration
to reduce visibility. This is the same phenomenon that causes clouds to form.
Mist is similar to fog except that it is the formation of liquid droplets
suspended in or falling through a moving or stationary atmosphere.
Smoke is dispersion of liquid aerosols formed by the incomplete
combustion of organic material in a gaseous atmosphere.
Gas is a phase of matter in molecular form, characterized by relatively low
density, which expands readily to fill any containing vessel.
Vapor is a gas formed by the evaporation of a material in liquid or solid
form. It is a gas at a temperature below critical temperature, so that it can be liquified under pressure without lowering the temperature.
* Brownian movement is the continuous zig-zag motion of particles (aerosols) in
suspension. The motion is caused by the impact of the molecules of the fluid (air) upon the particles.
Grease Removal Devices
The control and removal of grease from hoods by means of grease filters, baffles and similar devices is a subject of sufficient concern to warrant a separate chapter in NFPA 96. The standard specifies the conditions of installation and minimum distances between the cooking surface and the grease removal device.
Grease Extraction Rates
The National Bureau of Standards is not equipped to test ventilators. Manufacturers test their own units according to NBS test procedure IR74-505. This is therefore the procedure VM uses to test its Cyclo-Wash 3, Cyclo-Maze and Cyclo-Vent units.
Although VM tested its own units to the specified NBS test procedure, it used the services of the Institute for Storm Research to verify the tests. Dr. J. C. Freeman, President of the Institute, has expertise in air movement, temperature, point and factors related to condensation extraction.
The grease extraction rates of VM units, expressed as a percentage by weight of grease removed, are on the basis of averages of a series of tests.
Filters (stainless steel baffle type GF Series)
Of the various devices available to collect and remove grease from hoods, steel filters were for many years the most common means. The main requirements for a filter are that it must be:
C of steel construction, tight fitting and firmly held in position; C easily accessible and easy to remove for cleaning;
C installed at an angle not less than 45o
from the horizontal;
C equipped with a drip tray pitched to drain into a container having a
Figure 23 - Air flow in Cyclo Maze dry unit
1 2 3 4 5 6 7 8 7
Some devices for removing grease also serve other functions, such as removal of combustion gases, heat and cooking odors. VM has pioneered a number of combination units, which this Section explains. For installation, operating and maintenance procedures, refer to the relevant sections and the appendices.
Filter Grease extractor chambers (Cyclo Maze series)
There are two types of Cyclo Maze ventilators. One is a dry type; the other is a water mist unit that uses a cold water mist to extract grease and airborne solids, and a hot water wash for cleaning. The principle of operation for both types is the same.
Baffles cause grease-laden air entering the plenum to move in a spinning motion. With cold water mist nozzles, the air passes through a curtain of cold water mist, which causes grease particles in suspension to solidify and fall into a drainage trough or to spin off and collect on the baffle surfaces.
The high velocity flow of the air stream through a further set of baffles removes the residual grease in suspension under the effect of centrifugal force. The larger volume of the upper section of the plenum greatly reduces the air velocity, causing even more grease to fall out of the air stream before it flows through the head exhaust collar into the exhaust duct, as shown in Figure 23.
The unit operates on the principle of high capture velocities and low exhaust volumes. These two features combine to provide economical grease extraction. Baffles cause air entering the plenum from the cooking surface to move in cyclonic motion. The centrifugal action of the air causes heavier particles of airborne matter to collect on the baffle surfaces and drop to the bottom surface of the plenum. Stages in the air flow through the Cyclo Maze unit (refer to the items shown in Figure 23 and Figure 24) are:
1 The inclined face plate directs the air into the lower baffle chamber. 2 Air entering the chamber is spun in cyclonic motion.
3 The air then splits into two separate streams.
Figure 24 - Air flow in Cyclo Maze cold water mist unit 1 2 3 4 5 6 7 8 7 9
5 Manually adjustable baffles allow for air balancing along the length
of the hood when more than one type of cooking appliance is installed. 6 The upper chamber reduces the air velocity before it exits the pod to further
drop out grease particulates.
7 The air stream passes the exhaust control dampers used to adjust air volumes and balance different hood sections.
8 In the final stage, the cleansed air column passes through the listed fire damper assembly.
9 The cold water mist grease extractors are fitted with cold water nozzles to supply a continuous stream of mist to the extractor chamber (see Figure
24). This reduces the temperature in the chamber and increases the
extraction of grease (CCM series).
Note
Three factors affect the removal of grease in exhaust hoods:
C Air velocity
C Change of direction and spinning thin air
C Lower exhaust air temperatures
An efficient design uses a combination of one or more of these factors throughout the path of travel of the exhaust air in the grease removal chamber.
A good design in an extraction chamber requires a low static pressure to operate efficiently; i.e., low internal chamber resistance allows for lower horsepower and energy consumption to achieve maximum grease removal efficiency.
Grease Extraction Unit as an Engine
If we recognize an engine as the energy source which makes an installation or equipment function, we realize that the engine of a restaurant is its kitchen. In turn, the cooking bank is the engine of the kitchen and the exhaust hood or ventilation system keeps the cooking bank engine running smoothly.
Exhaust hoods come in various shapes, capacities and styles. The grease extractor is the engine of the hood and the main feature on which the efficiency of the hood depends. This report is a summary of the characteristics and specifications of hoods and their grease extraction engines.
What makes a hood engine efficient?
C Changing the direction of air to spin out grease. C Changing the air velocity to drop out grease.
C Changing the air temperature with cold water mist to scrub and condense out grease.
What types of engines are there?
Automobiles with which engines are most frequently associated are equipped with four, six and eight cylinder engines, together with many features that make them different. The same is true of exhaust hood engines.
The power of the engine lies in its capacity to remove grease. The 4 cylinder engine (2” deep) is the smallest in the range and removes the least amount of grease. The 6 cylinder engine is larger (12” deep) and can be manually cleaned or self cleaning using a hot water wash. The 8 cylinder engine has a cold water mist scrubber added and, using the third grease removal principle, removes a lot more grease. The 12 cylinder unit is the largest engine (18” deep). It has 200% more cold water.
4 Cylinder S/S filter 6 Cylinder Dry extractor or removable cartridge 6 Cylinder Dry extractor with hot water wash
8 Cylinder cold water mist extractor with hot water wash HOOD SECTION
"Engine"
areaThe exhaust hood body is the same as a car body. Vent Master hoods accommodate all engines
Ducts
As part of an overall ventilation system, the ducting serves two important functions. One is to exhaust the kitchen air to the outside environment; the second, when replacement air is supplied through the ducting system, is to deliver outside air to the kitchen space.
This chapter discusses the use of ducting in any ventilation system and considerations designers, suppliers and owners need to take into account.
Here, in a general way, it is worth noting that ducting is to the system what piping is to the water supply in that it directs the air flow from and, in some designs, to the kitchen space. The shorter the duct run, the less power is needed to move the air stream. In single-story structures where air is exhausted through the roof, the size of the ducting is not critical. The run is short, the resistance to flow negligible. In multi-story structures where the duct run length is considerable, the designer must calculate the size of the run with accuracy. Ducting resistance to air flow and duct length also determines the size of the exhaust and inlet fans.
Space is the important criterion. A long, straight duct run with minimum turns to smooth the air flow are basic to good design. There are, however, other important factors to consider. Many codes and standards specify that ducts must not pass through fire walls or partitions; kitchen ventilation ducts must not be interconnected with any other ventilation ducting or exhaust system; and duct runs must not have dips or traps in which cooking residues can collect. Openings for access are also required, the openings clearly marked to prevent the placing of obstructions to access.
ventilation ducts, which make the ducting an important part of any system. The applicable codes (see the Codes and Equipment Specifications Section), provide specific detail and consultation of those considerations that apply. Here are other important topics worth noting.
Ducts & ventilation rates
To give some idea of the cfm capacity requirements of exhaust systems, Table
3 lists cfm values used for various typical kiosk food court installations and the
hood sizes installed for food court applications.
Using the values tabulated in Table 3 for the eight kiosks, there is an average cfm value of 17,800/8 = 2,225. It is therefore safe to work on an average value of 2,500 cfm per kiosk, but allow for individual kiosk sizing for cfm. (See also the Auxiliary Equipment Section.)
Openings
Access openings are required either at the sides or on the top of duct runs at every change in direction. Hoods with dampers in the exhaust or supply collar require an access opening for cleaning and inspection purposes. Similarly, cleaning and inspection openings are needed for exhaust fans having duct work connected to both sides, the opening or openings to be within 3 ft. of the fan.
Duct cleaning is such an important part of maintenance that openings must allow for cleaning the duct work along its entire length. This, in turn, means that the system designer must make sure inspection and cleaning openings satisfy this cleaning requirement. Kitchen ventilation is not the same as ordinary building air conditioning ducting. Venting odors and grease vapor material can pose fire hazards about which local and jurisdictional authority inspectors can be and are particular.
Ducting installation
The emphasis placed on fire safety and protection by all authorities with regard to ducting is reflected in the installation requirements of ducting seams, penetrations and connections.
Many codes specify that duct-to-hood collar connections must have a liquid-tight continuous external weld. NFPA 96 from which
Figure 27 is taken is specific in its requirements for connections at the hood
collar that are not continuously welded.
Duct installation clearances
10' 0" Discharge Exhaust fan Access panel Weather-protected 40" Access panel opening
Not less than 1-hr fire resistance for
Roof Access panel
building less than 4 stories in height Not less than 2-hr fire resistance for
building 4 stories or more in height Opening in enclosure
Second story Grease duct Fire-rated floor Non-fire-rated ceiling
Sealed around the duct at this point since fire-rated floor
Exhaust hood
Figure 28 - Typical section view for building with two stories or more with non-fire-rated ceiling and fire-rated floor
For SI units: 1in = 25.4 mm; 1 ft = 0.305 m
Source: NFPA 96, 1994 Edition
potential of cooking operations. Figure 28, taken from NFPA 96 Appendix A, shows detail to cover various types of installation requirements for a typical commercial cooking exhaust system. Figure 28 is followed by Table 4 (also courtesy NFPA 96 Standard) giving examples of types of construction assemblies containing noncombustible, limited combustible and combustible materials.
Exterior installation
Many codes, and NFPA 96 in particular, recommend that duct work be installed vertically and adequately secured to the building exterior. The fasteners - bolts, screws or rivets - used to secure the duct must not penetrate the duct walls.
Interior installation
As specified in NFPA 96, in buildings having more than one floor, but also in single-story buildings with a specified fire-rated roof-ceiling assembly, ducts have to be enclosed in a continuous enclosure to maintain the integrity of fire separations required by the applicable building codes. The enclosure must extend from the lowest fire-rated ceiling or floor above the hood through
any concealed spaces to or through the roof.
Further, if the building is less than four stories, the enclosure wall has to have a fire rating of not less than one hour. In buildings of more than four stories, the enclosure fire rating has to be two hours or more.
If fire does occur in a ducting system, inspection by a qualified inspector is necessary before further use to determine if the structural integrity of the duct and enclosure still meets requirements for fire protection purposes.
The whole point of duct design and installation for ventilation systems is the need to consult, and comply with, applicable code requirements.
Exhaust terminations
Codes are specific for exhaust system terminations for both rooftops and walls. For example, for rooftop terminations, NFPA 96 specifies minimum clearances between the exhaust outlet and property lines, adjacent buildings and air intakes as well as minimum height levels of the outlet above adjacent air intake devices.
The requirements for wall terminations are equally specific, particularly with respect to clearances from the outlet to adjacent buildings, power lines, air intakes, doors and windows, etc. At no time should grease from a commercial kitchen cooking exhaust be allowed to run down the wall of a building.
Note: Exhaust termination requirements are shown in codes as minimum
requirements. Consideration must still be given to make sure that grease build up will not occur through roof top air intakes or in surrounding structures.
Air Flow
Every commercial kitchen requires make-up air to compensate for the air ventilated from the kitchen space to remove heat, cooking odors and grease created by cooking operations. Ventilation is also essential to maintain a comfortable work environment. Make-up air can be taken from the building HVAC system of which the kitchen area is usually a part, as illustrated in Figure
29. While this is frequently done, it is an expensive and inefficient method of
replacing exhausted air.
Quite apart from the obvious need to replace air removed from a kitchen, inadequate make-up air will prevent the kitchen operating the way it should. Air will be drawn in from other areas through doors and passageways.
In keeping with new requirements in kitchen ventilation, VM has introduced a number of devices for ventilating kitchens, which include kiosk ventilation units, air cleaning systems, water wash filter hoods with make-up air packages, dampers for adjustable volume control and fire dampers.
The easiest situation in which to provide make-up air is in a free-standing building of one level construction, such as found in food courts or restaurants. The complexities of providing make-up air increase as the building in which the kitchen operates changes from the detached, single-purpose building to the multi-story tower structure (see the Design Section for further discussion of this subject).
Make-up air can come from the room HVAC system, either from outlets near to the hood or integrated into the hood. The use of cooled and heated make-up air is expensive. For example, utility bills can double and triple. (Every 200-400 cfm of air requires one ton of A-C system capacity, which is expensive.) Following is a summary of the devices and systems available to solve the
problem of providing make-up air.
Distributing air from the ceiling near the hood with low air velocity provides local cooling that is a necessity because of the strong radiant heat created by cooking appliances. Increased airflows did not raise metered indicators at the same ratio, which proves that good results in kitchen ventilation can be achieved with careful design and efficient equipment without excessive airflows.
The following are some basic principles of commercial kitchen ventilation: 1. Impurities and excess heat should be removed with efficient local
exhaust.
2. Supply air should be brought to the working area in such a way that it first refreshes workers and then replaces convective flows. 3. Where workers are subjected to large heat radiation, supply air should be introduced directly to the working space (local cooling).
Down discharge supply air designs
The advantage of using integrated make-up air is that in large measure it reduces the burden on the building HVAC systems. Make-up air is supplied by a down discharge duct and blower close to the cooking surfaces. Three disadvantages, however, outweigh this advantage.
1. The air velocity from the hood supply air opening is greater than that of heated air rising from the cooking surface, which results in spillage of contaminated air held within the hood. 2. The lower temperature of the make-up air combined with the
greater velocity causes the air to drop rapidly, pulling contaminant into the operator's face.
3. The direct down discharge can make it uncomfortable for kitchen staff, especially in cold climates. As a consequence, operators often shut off the make-up air system, thereby nullifying its usefulness.
Short cycle supply air
untempered outdoor air within the hood enclosure to reduce the amount of air the HVAC system must supply. This may seem to reduce the cost of using the HVAC system, but unless the velocity of the supply air is strictly controlled its velocity can exceed the velocity of the exhaust air and cause smoke emission from the hood cavity.
The difference between discharging make-up air into the kitchen space from the hood bottom front lip (Figure 30) and the short cycle method (Figure 31) lies in the air discharge exits of the two arrangements.
In addition to the chance of emitting smoke, safety problems can arise with short cycle hoods. In northern regions, for example, cold air can cause frost build-up on fire protection fusible links, which effectively prevents the links from detecting fire.
Front panel make-up air
The front panel type of make-up air (see Figure 32) is effective for virtually all applications and climates. A perforated stainless steel plate keeps the air flow velocity between 300 and 500 fpm. This permits the supply of a large volume of air at the hood, with little or no effect on the kitchen environment. The low velocity of make-up air means that it is felt only 3 to 4 feet from the hood face.
During winter months, it may be necessary to heat the air of front panel type make-up air (50o - 60oF is recommended). The need to cool the air during the summer period is, however, negligible because the incoming air provides evaporative cooling to kitchen staff working under the effect of radiant heat generated by the cooking operation. Special consideration for some cooling may be required in hot, humid climates.
Exhaust and make-up air limitations
If one site provides ample access for duct shafts to exhaust to the roof and provide outdoor make-up air back to the kitchen, there are others with restricted access. This poses problems. With no obvious solution to providing the required air changes or to providing exhaust to the roof, and with space limitations that make the installation of equipment difficult, the designer has many problems to
overcome. A number of options are, however, available.
These are by no means the only options available for situations in which a
conventional solution to providing make-up air is difficult. The options shown in Figure 33 illustrate that even in demanding circumstances there can be more than one answer. The option chosen will of course depend on the particular circumstances of each project.
Why ventilation systems are essential
Cooking produces heat, odors, smoke, vapors, airborne grease and other pollutants, which is true of all cooking operations regardless of the type of food preparation being done. When a ventilation system breaks down, the kitchen atmosphere soon becomes stifling and impossible to work in. Hence, a constant supply of fresh, clean air is essential.
The ventilation system must exhaust the heat produced and remove the odors and pollutants. A kitchen which specializes in producing light snacks, sandwiches and salads generates less heat and odors than kitchens producing heavier fare: steaks, hamburgers, and French fries.
Venting cooking equipment
Gas, electric and steam cooking equipment must be allowed to breathe. Proper air flow is required for combustion, to exhaust fumes and odors, and to prevent moisture and heat build-up in control cabinets. Too much exhaust can suck the heat out of an oven, preventing it from properly baking or roasting the product; too little exhaust can cause a control cabinet to overheat and burn out expensive equipment. Knowing what the cooking equipment requires for ventilation is critical to its performance and operating life. If the cooking equipment does not work properly, the kitchen will not remain in business long.
Maintaining negative pressure
The final reason why efficient ventilation is necessary is the need to maintain negative pressure in any kitchen area. Negative pressure means drawing air into the kitchen space atmosphere to contain the odors and pollutants that cooking operations generate.
Kitchens operating under positive pressure force cooking odors into spaces outside the kitchen envelope. This is unacceptable in most instances and certainly in places of shared space: food courts, hotels, office buildings, and even in large, stand-alone structures where the owner-operator wishes to maintain fresh air free from excessive cooking odors in large dining
areas.
Combination of equipment
The type and combination of kitchen equipment used affects the design and capacity of the ventilation system. Deep-fryers and open ranges produce more pollutants and continuous heat than closed ovens. When opened to remove roasts, pizzas and baked products, ovens release waves of intense heat with which the ventilation system must cope to maintain a stable atmosphere in the kitchen space. The type of equipment required is one factor; the use of kitchen space is another.
Regardless of the source of make-up air, it is necessary to calculate the make-up air required for a given kitchen operation. This will depend on the type of cooking being done, the equipment installed, and restrictions of the building configuration. Some considerations to take into account when calculating the make-up air and equipment required are:
C Keep make-up air velocities to a minimum.
C High velocity make-up air will disturb the capture of smoke by other equipment.
C Maintain a slight negative pressure in a kitchen to prevent odors and pollutants moving from the kitchen area to other parts of the building (a 20% negative pressure is recommended).
C Local regulations are an important consideration and no installation should be undertaken nor an existing operation changed without first checking local regulatory requirements.
CFM requirements of exhaust hoods
To calculate the required exhaust air for a hood, a number of factors must be known:
C The cooking equipment being used, to determine where the most smoke, grease and heat will be produced along the cooking bank.
C The type of cooking to be done: soup and sandwich preparation; burger and French fries cooking, fish and chip operation.
C The hood arrangement and wall locations around the cooking equipment, island operation, or a combination of island and wall locations.
C The kitchen layout, to determine if there is a combination of space restriction with a hot cooking operation.
A guide to use for estimating CFM requirements for wall-mounted hoods is:
C For light duty equipment such as steam and ovens, use 250 CFM per linear foot.
C For medium-duty equipment such as fryers, griddles and restaurant series ranges, use 300 CFM per linear foot.
C For heavy duty equipment, charbroilers and heavy-duty equipment, use 350 CFM per linear foot.
In the majority of instances, the CFM estimates given in the guide will provide ample air for the exhaust requirements. The guide serves for wall-mounted canopies only. It does not serve for island applications, single cooking bank arrangements or in cases where, say, the designer wants to know the absolute minimum requirements.
CFM calculations for hoods
The terms used to calculate CFM values are:
Minimum exhaust cfm = Capture area x capture velocity + equipment cfm
correction factors.
Capture area = all open sides of the hood x the height above the cooking
equipment (in feet).
Capture velocity = 50 fpm (minimum.)
Equipment cfm correction factors = see Table 5 in left hand column of this
page.
A sample CFM calculation based on the elements discussed in this section is shown in Figure 34.
18' 3.5' 3.5' 3.5' 16.5' Broiler Kettle Range Fryer Fryer Griddle
Min. exhaust cfm = (W1 + W2 + L) x H x 50 broiler + fryer + griddle = (3.5 + 3.5 + 18) x 3.5 x 50 + (225 + 75 + 75 + 150) = 4375 + 525
= 4900 cfm (min.)
Using a rule of thumb for medium duty cooking of 300 cfm/linear foot of hood, the total cfm is
= 300 x 18 = 5400 cfm Note:
Figure 34 - Sample cfm calculation
Velocity readings on Cyclo Maze-type hoods
To measure the average velocity on intake slots for ventilators use one of the following formulas:
1. The velocity in feet per minute (FPM), Vol = FPM or CFM = FPM
OPN sq.ft.area where OPN is the total area of intake throat in sq, ft. 2. To find the volume in CFM,
CFM = VEL x OPN
3. To calculate the velocity, divide the CFM by the total opening. The CFM or CFM/ft is information given on the U.L. label of the hood. The standard Cyclo Wash opening is 3.5” x the length of the throat. The total opening is 3.5” x the overall length of the intake throat. The average throat velocity on most VM Cyclo-Maze Wash and Cyclo Maze Dry is calculated by multiplying the design air flow rating (shown on the ventilator nameplate) in CFM per linear ft. by 3.5. The result is the velocity in FPM.
Example
The specification is for 2250 CFM on a 9' ventilator. OPN = 107” x 3.5” = 374.5 sq. in.
= 374.5 = 2.6 sq. ft. 144
VEL = 2250 = 865 FPM
2.6
For quick reference, use Table 7.
Measuring intake velocity
VM recommends the use of either an Alnor 6000 or Alnor Jr. to measure the air velocity through the slot of Cyclo Wash and Cyclo Maze ventilators.
To measure velocity at the throat using the Alnor 6000 (see Figure 35) position the tip of the velometer probe halfway between the inside rim and the face of the access panel at a plane perpendicular to the air stream. Do not put the probe too deeply into the intake throat or you will get erroneous readings. Make sure that the hoses are of reversed polarity (+ to - and - to +) when measuring the exhaust. Take a minimum of three readings, evenly spaced, at each access door, then average the readings to calculate the exhaust rate.
The Alnor Jr. (see Figure 36) has a dual scale range to 1600 FPM and is another convenient way of measuring the intake velocity. Position the velometer as shown in the figure and take multiple readings at various points across the length of the intake throat. Because the instrument is calibrated for use in an upright position, expect a slight error (to 5%) on the high side. If accurate readings are needed, use an Alnor 6000 velometer.
Auxiliary Equipment
Auxiliary equipment covers those items specified as such in NFPA 96 together with other devices or equipment not easily categorized under other references. Typically, VM's modular utility distribution systems (MDS) discussed here are in this category. Other devices and equipment include dampers, electrical equipment, fans and the VM Ecoloair system.
Dampers
A common problem in large kitchens is that of air balancing and control. The use of air volume control dampers helps. NFPA 96 does not, however, permit the inclusion of dampers in hoods or ducts unless they are specifically listed for such use.
Manually-operated dampers for volume control and balancing are normally mounted before a (hood) ventilator fire damper as shown in
Figure 37. All VM ventilators are equipped with UL/ULC listed dampers. The
volume control damper can be adjustable to close off up to 50% of the outlet duct collar area by means of locking fasteners.
Electrical equipment
Electrical equipment, wiring, and controls are for the most part governed by the National Electrical Code as well as local jurisdictions. Specific requirements regarding electrical devices and wiring systems in kitchen ventilation systems are summarized:
C It is not permissible to install wiring of any type in ducts.
path of exhaust air except where specifically approved for that use in grease ducts. For example, they are essential in fire control and protection devices such as fire doors.
C Steel-enclosed lighting units mounted on the outer shell of a hood and separated from the exhaust products by tightly fitting tempered glass and vapor-tight seals are acceptable, but cannot be placed in concealed spaces or cavities.
Fans
The selection of fans for ventilation systems, either to exhaust or to provide make-up air, is an important consideration. Many types and arrangements are available.
For typical roof top exhaust equipment and fan design improvement: 1. Check the location and setting of the exhaust air discharge in relation
to the fresh air intake as shown in Figure 38, A and B.
2. Check the location and setting of the exhaust air discharge in relation to the fresh air intake as shown in Figure 39, A and B.
3. Improve the vertical discharge velocity to disperse smoke and redirect exhaust air away from the roof line.
4. Simplify the fan access and duct access.
5. Remove the need for external wire connections and pitch pockets at the roof.
Fan location
Open area around entire fan to allow slow velocity charge & rain water inlet Light, aluminum construction
Roof pitch pocket to seal opening for wiring Exhaust air, smoke and grease, odors & access area
Disconnect switch and hood-up and external switch
Run waterproof wiring to fan Overflow drain plug
from fan
Greasebox and lid
Custom fabricated rated roof curb
Fire-rated enclosure for
roof opening as per NFPA 96 Grease duct to go up to top ofroof curb min. 18" above roof Wiring to runoutdoors to fan line as per NFPA 96
Figure 40 - Exhaust equipment design features
6. Stop the build-up of water in fans during heavy rain storms and when the fan is not in service.
7. Improve grease removal from fans during cleaning.
8. Stop the build-up of grease on the roof during rain storms by flushing grease out of fan collection boxes.
9. Simplify installation requirements and cut the cost of installing exhaust fans.
10. Provide improved access to fans for servicing.
11. Provide additional fire safety for exhaust discharge and the roof structural opening.
12. Prevent the build-up of grease on roof tops and the A/C unit. (See
Figure 40).
VM’s grease exhaust roof fans are heavy duty UL\ULC units listed for 3” clearance from combustible material. A discharge clearance of 40” above the roof line as required by NFPA 96 eliminates discharge duct work above the roof. This unit, shown front view in Figure 41, has removable access doors for servicing, a pivoted fan drive section to give access to the exhaust duct, and an average discharge velocity of 3,000 fpm as recommended by
environmental authorities.
Filtration systems
The ecology filtration system of an Ecoloair unit removes 95 per cent (and 99% as measured by ASHRAE Standard 52-68) of particulates over 0.03 microns. This virtually means the removal by filtering of all smoke and grease, which means that part of the odor-carrying material is removed from the exhaust. Molecules too small to be filtered out, however, convey most of the odor. This material is chemically treated by VM's Scentry liquid odor control solution, which reduces cooking odors to innocuous levels.
VM rates odors for cooking operations in three categories:
CC Light: cooking a general menu for a period of 8 to 10 hours a day; covers
the operations of a small to medium-sized restaurant.
CC Medium: Small to medium-sized restaurants cooking from 12 to 16 hours
a day, preparing fragrant or pungent foods and marinades, are in this category. If, however, the menu includes a high proportion of strong fragrance-producing foods the restaurant should be placed in the high odor-emission category. Similarly, restaurants that produce large volumes of even general menu foods with short, heavy peak periods are in a medium to high category.
C High: This category covers large volume restaurants, hotels and 24-hour
food preparation operations using large broilers and preparing fragrant foods for 16 hours a day or more.
Heat exchangers
Relative to make-up air systems, cooking operations require large amounts of energy. Up to 70 per cent of the heat energy needed for cooking is exhausted to atmosphere when drawing in make-up air and exhausting the used air. Recovering this otherwise lost energy by means of an air-to-air heat exchanger is possible and has obvious economical advantages in the right circumstances. It is part of the kitchen consultant's job to include this in any kitchen planning
study. This section will help clarify the main points.
Exhaust air temperatures in the order of 85oF to 95oF at 50% RH make the heat recovery option economic, when the air volume being considered is in excess of 5,000 cfm. For air volumes less than this level, the energy cost saving may not cover the cost of the equipment. These are general statements, but give some idea of the point at which heat recovery is worth considering. Nevertheless, since the make-up air is about 80% of the exhaust air there is more heat in the exhaust air stream to recover, which allows a higher temperature rise in the fresh supply air stream.
Kitchen heat recovery equipment usually handles exhaust air laden with airborne greases given off by the cooking equipment. As this can easily plug up the heat exchanger it is necessary to wash and clean the coil frequently. Depending on the application, a detergent spray wash system is fitted on the exhaust side of the unit. The frequency and duration of the spray is adjustable to suit the particular operation.
Note: Heat pipe systems are normally used for this application as air-to-air
plate type heat exchangers are difficult to clean and maintain in greasy cooking applications.
Another way of dealing with grease-laden air when using heat recovery equipment is to filter the exhaust air before it enters the heat exchanger. Again, the relative cost of this method as compared with a wash feature on the heat exchanger requires study.
A rule of thumb to calculate savings from the installation of a heat recovery system is $1 per cfm per year. A pay-back period of two to four years would be the second criterion to use. To use an example, if the supply air volume being handled is, say, 10,000 cfm, the saving in fuel costs would amount to $10,000 per year. Applying the pay back period of three years, a capital cost estimate of $30,000 for energy recovery equipment is an economic investment.
Figure 42 - Modular Distribution System Mechanical Gas Hot water Cold water Steam supply Steam return Chilled water Compressed air services available Access panel Bus bars or Isolated
Branch plumbing connections with optional quick disconnect fittings and color-coded hoses Power supply available
120V AC through 600V AC Single phase or 3-phase Safety shunt trip breakers
Isolated electrical panel box plumbing chase chase Example Location of branch circuit breaker Equipment bumper rail
Cords and plugs or sealtite conduit available
Modular distribution systems
An efficient and economical way of supplying utilities to commercial cooking equipment and distributing those same services is by means of a utility distribution unit. VM manufactures such a unit as a modular utility distribution system, abbreviated MDS.
A MDS unit can include the utilities of gas, electrical power and controls, hot, cold and chilled water, steam supply and condensate return, and compressed air.
These pre-assembled units eliminate the installation and coordination of all of the trades for piping, junction boxes conduit runs, and service wall construction. Installation of a MDS unit requires only limited preparatory work to bring incoming utility services for hook-up.
A big advantage of the unit is the ease with which cooking equipment can be re-arranged to suit changed cooking operations. Quick disconnect fittings for electrical and plumbing utilities mean that there is no need to rewire or change the plumbing. Figure 42 shows a cut-away view of a MDS unit and lists its main features.
Figure 42 and Figure 4.4 provide raceway and riser options of specific
Features of the MDS
Features of the modular distribution system (see also the Engineered Features Section) are:
C It provides the most cost-effective method to distribute utilities in commercial cooking operations.
C All piping and wiring is completely enclosed in an isolated stainless steel, 300 series chassis.
C Full function capabilities are available for gas, electric, hot water, cold water, steam, chilled water, and compressed air services.
C Flexibility is built into the system allowing for additions and changes.
There is safety, convenience, flexibility and efficiency in a UL/ULC factory-built utility wall.
Raceway Options MDS-GW Unit MDS-GWS Unit MDS-GW Unit View A-A MDS-GWS Unit View B-B A A B B 24" (Typ) 12" (Typ) 31" 24" 21.5" 8" 6" 1.5" 12" 28.5" 72" Space between electrical plates Typical electrical plates configuration 72" 24" (Typ) 12" (Typ) Typical electrical plates configuration 6" 12" 3/4" H.W. Insulated 3/4" C.W. Insulated 2" Gas Bumper strip 1.5" Steam insulated 1" Condensate return insulated Receptacle Breaker
Cord & plug
3/4" H.W. Insulated 3/4" C.W. Insulated 1.5" Gas Note: Raceways can be wall mounted
Riser Options
for MDS-GW & MDS-GWS Units
MDS-GW-EL/PR MDS-GW-EPR MDS-GWS-EPL/PR MDS-GWS-EPL/EPR (Recommended) Pedestal Electrical & plumbing (Typical) (Special) Electrical Electrical & plumbing Plumbing Plumbing Electrical & plumbing Electrical & plumbing (Recommended) 72" 72" 72" 72"
Kiosk Ventilation System
The Kiosk Ventilation System (KVS) is a recirculating air unit that was developed for kiosk-type food court operations and non-traditional sites where NFPA 96 duct work either cannot be installed or would be difficult to install. The KVS unit can be a right hand (RH), left hand (LH), Back (B) or remote mount (REM). The size of a unit depends on the CFM delivered and ranges from 1100 cfm to 2250 cfm.
To select a particular size of KVS unit, the designer needs to know the type of cooking equipment installed in a given kitchen and its size. Types of cooking equipment are summarized in Table 8 following.
Note 1: There are three VM KVS models available. These are the KVS-5,
the KVS-6 and KVS-8. Referring to the table of cooking equipment, a KVS-5 can satisfy a cooking load for a maximum of 2 appliance; a KVS-6 for 3 appliances; and a KVS-8 for 4 appliances. See also the Codes and Specifications Section.
Note 2: A recirculating hood system must meet the requirements of NFPA
96, Chapter 10 and be tested and listed as per U.L. 197-1994 for integral recirculating systems for commercial electric cooking appliances. A clean air EPA 202 test must also be passed using the specific cooking equipment being used with the system.
Fire Protection Equipment
Fire protection and control is an integral part of any kitchen ventilation system. The subject is specifically addressed in the NFPA Standard, which requires fire extinguishing equipment for the protection of grease extraction devices and cooking equipment. NFPA 96, however, is not the only standard local regulatory authorities apply to commercial kitchen systems.
Automatic fire extinguishing systems are an increasingly common feature of modern kitchen ventilation systems. Indeed, most codes require that automatic fire protection systems form part of the ventilation system. This system must not only provide fire protection, but also automatic disconnection of the fuel supply to the cooking equipment if a fire occurs.
The three primary types of fire protection systems are dry chemical, wet chemical and water sprinkler, which are summarized here.
Dry chemical systems
The chemical most often used in a dry system is a sodium bicarbonate based material. In this type of system, the chemical suppresses the flame and reacts with the grease to form a foam, which prevents the grease and vapors from escaping to the atmosphere. The dry chemical system is being replaced by the more efficient and cost effective wet chemical system and will soon be removed from the field for new installations.
Wet chemical systems
In contrast, wet chemical systems most commonly use a potassium carbonate, potassium acetate, or CO2 based formulation. The wet chemical is similar to the
action of dry chemical in suppressing the flame and preventing or retarding the escape of grease vapors to the atmosphere.
Both wet and dry chemicals are effective fire extinguishing agents, but both have several disadvantages. The most obvious is that, following
