Kitchen Application KVS/001-116

Kitchen Application KVS/001-116
Kitchen Application
®
KVS/001-116
A technical bulletin for engineers, contractors and students in the air movement and control industry.
The Right Test Standard For Pollution Control Units
The following information is intended as a guide
to understanding pollution control units and the
importance of why UL 1978 Standard for Grease
Ducts should be used when specifying a pollution
control unit. Read on to learn more.
The engineers and food service consultants who
select and specify kitchen systems carry a great deal
of responsibility. That’s why it’s important to specify
certified products designed for optimal performance,
reliability and safety.
kitchen space through a Type I kitchen hood. Initial
filtration of the grease laden air ideally occurs at the
kitchen hood. The PCU is connected to the kitchen
hood by a fully-welded or listed grease duct running
from the hood to the PCU. The air is pulled through
the duct and PCU by an exhaust fan at the PCU
outlet. Secondly, as the air is pulled through the PCU,
multiple stages of increasingly efficient filtration
remove grease particulate from the exhaust airstream.
About Pollution Control Units
Pollution Control Units (PCU), also
known as Air Purification Units or
Exhaust Filtration Systems, have been
in use in commercial kitchen exhaust
systems for many years. However, due to
new requirements of many municipalities
and local Authorities Having Jurisdiction
(AHJ), they are quickly becoming an increasingly
integral part of commercial kitchen exhaust systems.
Using PCUs help reduce the release of grease
particulate and smoke odor from cooking operations
into the surrounding space and atmosphere. They are
useful in multi-purpose buildings where the kitchen
exhaust can be routed horizontally through a side wall
near street level rather than needing to install long
runs of vertical ductwork to reach a rooftop exhaust
fan. In addition, eliminating grease and odor from
the exhaust air is desirable to the occupants of nearby
buildings as it prevents the buildup of grease on roofs,
walls, sidewalks, and cars.
A PCU serves three main purposes. Its first purpose
is to exhaust grease laden air from the commercial
Pollution Control Unit
Lastly, the air passes through a media that neutralizes
the cooking odor.
PCUs as They Relate to Codes and Standards
The International Mechanical Code (IMC) requires
that a Type I hood be used where the appliances
produce grease or smoke. The hood is then connected
to the duct by liquid-tight welded or brazed joints.
The duct run from the hood collar to the exhaust fan
is also to be constructed such that all joints and seams
are of a continuous liquid-tight weld or braze, unless
the duct is a factory-built grease duct that is listed
in accordance with UL 1978 – Standard for Grease
Ducts. It then follows that if grease laden air is to be
exhausted through a PCU to an exhaust fan, that the
PCU should actually be part of the grease duct. As
P.O. Box 410 • Schofield, WI 54476 • 715.359.6171 • Fax 715.355.2399
Copyright © 2016 Greenheck Fan Corp.
Greenheck Product Application Guide
such, PCUs should also be required to
have fully welded or brazed joints, or be
listed in accordance with UL 1978.
UL vs. ETL — Evaluation and
Listing of PCUs
When PCUs were first developed, there
was not a specific standard to which
the products could be evaluated (and at
the time of this writing there still is not
a standard for PCUs). This leaves the
determination of what tests are required for listing to
independent third parties such as UL and ETL.
Underwriters’ Laboratories viewed PCUs as a grease
duct and determined that evaluating PCUs to the
heat related tests from UL 1978 – Standard for Grease
Ducts were the proper tests to obtain an UL Listing
for PCUs. (Page 3)
ETL determined that evaluating PCUs to the heat
related tests from UL 710 - Standard for Exhaust
Hoods for Commercial Cooking Equipment, listed
of page 3, were adequate to obtain an ETL Listing for
PCUs.
There are stark differences between the tests required
to obtain listings to each of the standards. Reviewing
the comparison on page 3, it becomes apparent that
the tests for UL 1978 are more rigorous and better
suited to evaluate grease duct, whereas UL 710 was
Pollution Control Unit with Progressive
Filtration Modules Shown
developed for listing exhaust hoods. Grease duct is to
function as an air tight and liquid tight conduit for
grease laden kitchen exhaust air. As such, it should
have sound structural integrity, prevent the leakage
of any grease or smoke to the exterior of the duct, as
well as contain any fire within the duct, even when
subjected to the extreme temperatures associated with
grease fires.
Summary
Knowing that PCUs are, in fact, an extension of the
grease duct, it follows that UL 1978 is clearly the
correct standard to use for the safety evaluation of
PCUs.
There are several manufacturers of PCUs. The
specifications for most PCU manufacturers state that
the unit is listed to UL 710 – Standard for Exhaust
Hoods for Commercial Cooking Equipment. Only a
few manufacturers specify that their PCUs are listed
to UL 1978 – Standard for Grease Ducts. Based on
the increased rigor of UL 1978 for fire safety, we
recommend that all PCUs be tested and evaluated
to UL 1978. Specify with confidence, choose a UL
1978 PCU.
Abnormal Temperature Test
PCU must completely contain all smoke and flame to pass UL 1978 test
standard. Greenheck unit passed all UL 1978 est criteria.
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Kitchen Application KVS/001-16
Greenheck Product Application Guide
UL 1978
UL 710
Temperature Test 500°F
Temperature Test
1. A flue gas generator injects heat into the duct/PCU 1. An appliance is set below the hood/duct and adjusted
to the desired surface temperature (varies depending
system to be tested.
on appliance).
2. The energy input is substantial enough (925 Btu/hr.)
to produce an airstream temperature of approximately 2.
500°F.
3.
3. This temperature is then held until equilibrium is
reached (usually approximately 1.5 hours).
The appliance is brought to equilibrium (fairly quickly).
The hood/duct components cannot rise by more than
a maximum of 480°F for galvanized steel and 1310°F
for 430 stainless steel.
4. The maximum temperature rise on any part of the duct
cannot exceed 480°F for galvanized steel and 1310°F
for 430 stainless steel.
Abnormal Temperature Test — 2000°F
Cooking Smoke and Flare Up Test
1. Immediately following the Temperature Test, the
heat input from the flue gas generator is increased
such that the airstream temperature is approximately
2000°F.
1. No evidence of smoke or flame escaping from the
hood/duct is allowed.
2. There is an enclosure surrounding the duct at
which the surface temperature cannot exceed 175°
above the ambient air temperature. This is used to
determine clearance to combustible surfaces.
3. The appliance is brought to equilibrium and food
product containing fat is cooked.
2. The air exhaust rate is set to the minimum amount
desired by the equipment manufacturer.
4. This is commonly known as a Capture and
Containment Test.
3. The energy input and 2000°F airstream temperature is
5. It is used for determining acceptable minimum
maintained for 30 minutes.
exhaust rates for kitchen hoods — not for grease
4. During the test and after 30 minutes, the duct/PCU
ducts.
cannot leak any smoke, air, grease, or flame.
5. The structural integrity of the assembly must remain
intact.
Leakage Test
Abnormal Flare Up Test
1. The entire interior of the grease duct/PCU is to be 1.
coated with animal lard (0.3 lbs./sq. ft.).
2.
2. Two lbs of pork lard are to be melted, ignited, and left
to burn out under the inlet to the duct/PCU.
3.
The desired hood exhaust rate is to be established.
One pint of vegetable oil is brought to ignition on top
of an appliance and below the test hood.
The vegetable oil is left to burn out completely.
3. No leakage of grease, oil, smoke, or flame is allowed 4. The exhaust airstream cannot exceed 375°F and
at any of the joints or access doors of the duct/PCU.
flames cannot enter the hood exhaust collar.
5. Hood parts shall not be damaged such that they
present an electrical or fire risk.
Gasket Text
Fan Failure Test
1. All gaskets/seals used on joints and access doors are
subjected to tensile strength, ultimate elongation and
volume change tests.
1. This test is the same as the Abnormal Flare Up Test,
except the exhaust fan is not operational.
2. Representative samples are “aged” or immersed in
vegetable oil.
2. One pint of vegetable oil is brought to ignition on top
of an appliance and below the test hood.
3. The vegetable oil is left to burn out completely.
3. “Virgin” and “aged” samples are subjected to the
tests above.
4. The exhaust airstream cannot exceed 375°F and
flames cannot enter the hood exhaust collar.
4. Elongation of “aged” samples cannot decrease by
more than 50% from “virgin” samples.
5. Hood parts shall not be damaged such that they
present an electrical or fire risk.
5. Tensile strength of “aged” samples cannot decrease
by more than 50% from “virgin” samples.
6. Volume change of “aged” samples shall be from -1%
to 50% of the volume of the “virgin’ samples.
Kitchen Application KVS/001-16
3
Greenheck Product Application Guide
4
Fan Application FA/113-01
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