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Why are hoods with combination sashes offered as open bypass by special request only?

The face area for a hood with a combination sash is based on the opening through the horizontal siding panels. It has roughly one half the face area of the same size hood with a vertical sash. Therefore, the hood with a combination sash requires a smaller (restricted) bypass even if it is to be used for constant volume operation. In fact, having an open bypass provides no operational benefits and increases the exhaust requirement for the hood as air must be drawn through the bypass into the hood. The only time an open bypass is required is if the exhaust volume is based on the sash raised vertically rather the opening through he horizontal panels.

Why doesn't the fan switch work?

The fan switch requires the installation of a Square D Thermal unit to function. The thermal unit is not supplied with the switch as it must be selected based on the full load amperage of the fan motor.

Motor Full-Load Current AmperesThermal Unit NumberMotor Full-Load Current AmperesThermal Unit NumberMotor Full-Load Current AmperesThermal Unit Number
0.41 – 0.44A .491.57 – 1.65A 1.865.36 – 5.85A 7.65
0.45 – 0.49A .541.66 – 1.79A 1.995.86 – 6.41A 8.38
0.50 – 0.53A .591.80 – 1.95A 2.156.42 – 6.79A 9.25
0.54 – 0.58A.651.96 – 2.15A 2.316.80 – 7.57A 9.85
0.59 – 0.65A.712.16 – 2.38A 2.577.58 – 8.15A 11.0
0.66 – 0.71A .782.39 – 2.75A 2.818.16 – 8.98A 11.9
0.72 – 0.78A .862.76 – 2.84A 3.618.99 – 9.67A 13.2
0.79 – 0.85A .952.85 – 3.06A 3.959.68 – 9.95A 14.1
0.86 – 0.96A 1.023.07 – 3.45A 4.329.96 – 10.8A 14.8
0.97 – 1.04A 1.163.46 – 3.70A 4.7910.9 – 12.1A 16.2
1.05 – 1.16A 1.253.71 – 4.07A 5.3012.2 – 13.1A 17.9
1.17 – 1.29A 1.394.08 – 4.32A 5.7813.2 – 13.9A 19.8
1.30 – 1.37A 1.544.33 – 4.90A 6.2014.0 – 15.0A 21.3
1.38 – 1.47A 1.634.91 – 5.35A 6.9915.1 – 16.0A 25.2
1.48 – 1.56A 1.75
Kewaunee Fan115 Volts230 Volts
Model NumberHorse Power RatingFull Load Current AmperesSquare D Thermal Unit NumberFull Load Current AmperesSquare D Thermal Unit Number
HFS-09021/4 HP5.0A 6.992.5A 2.81
HFS-09031/3 HP6.0A 8.383A 3.95
HFS-09051/2 HP7.4A 9.853.7A 5.30
HFS-10073/4 HP8.2A 11.94.1A 5.78
HFS-13101 HP12.8A 17.96.4A 9.25
HFS-13151-1/2 HPn/a*n/a*n/a*n/a*
HFS-14202 HPn/a*n/a*n/a*n/a*

* Fan switch on Kewaunee fume hoods is rated for 1 HP motors or less

Why doesn't the indented portion of the worktop extend closer to the face of the hood?

The indented portion of the work top defines the safe working area of the hood where contaminants can be generated without exposing the hood user. This safe working area starts 6″ behind the sash opening. The hood user is likely to be exposed to any contaminants generated in front of this safe working area due to the eddies in front of the use’s body.

Where are the model and serial numbers located on the hood?

They are located on the right vertical facia behind the top front panel.
See diagram

At what sash height should I measure the hood face velocity?

Normally the hood face velocity is measured with the sash fully open. However, if the hood has a gravity sash stop (Option 8) or a sash label (F-4803-00) to indicate the safe sash height, the face velocity should be measured with the sash at the stop or label.

Does an open bypass hoods have a constant face velocity?

No, the face velocity on an open bypass hood will increase as the sash is closed. The bypass limits the increase in face velocity to no more than three and a half times the velocity with the sash closed. This allows the hood to maintain a constant exhaust volume flow rate.

Are fume hoods required to have explosion proof electrical fixtures?

No, according to NFPA 45 Fire Protection for Laboratories Using Chemicals, laboratories and hoods are unclassified electrically with respect to Article 500 of the National Electrical Code. Where there is an extraordinary hazard, the user may wish to use explosion-proof electrical fixtures for added safety.

What standards exist for testing fume hoods?

The most widely used standard for testing hoods is the ASHRAE 110 Method of Testing Performance of Laboratory Fume Hoods. This standard has sections for visualization of flow patterns, measuring face velocity, and measuring containment using a tracer gas. In addition the SEFA 1.1 Laboratory Fume Hoods Recommended Practices has sections on visualizatio n of flow patterns and measuring face velocity.

What are the OSHA fume hood face velocity requirements?

OSHA does not have specific requirements for fume hood face velocity. The most widely accepted references on this subject ANSI/AIHA Z9.5 American National Standard for Laboratory Ventilation and the National Research Council’s Prudent Practices in the Laboratory recommend face velocities of 80 to 120 feet per minute (FPM).

How do I wire my hood?

Usually the hood is connected to a single 120 volt, 20 amp circuit. 12 gage THHN solid strand wires in flexible metallic conduit is generally acceptable.

For a typical wiring diagram for a hood:
Click here

If I have a fan switch on my hood, should I connect the Air alert alarm through the fan switch?

Yes, in most instances it is preferable to have the alarm deactivated when the hood exhaust fan is off. If the hood fan is off and the alarm is powered, the air currents created by people walking past the hood may cause the alarm to momentarily go to “NORM”. When the air current subsides the audible alarm will activate again. Many people find this annoying.

Where is the hood exhaust fan located?

The fan should be remote from the hood, either on the roof or a penthouse. In facilities with many hoods, several hoods may be connected to a one exhaust fan.

What type of exhaust duct should be used?

The most often used material for exhaust ducting is stainless steel. It has good chemical resistance and is noncombustible. For highly corrosive applications PVC is often used. PVC is combustible and should be used in such a manner that it does not compromise the fire protection of the lab. For noncorrosive applications, galvanized steel may be used.

Are Kewaunee hoods UL approved?

Kewaunee hoods that are wired at the factory and contain only the following devices are listed under the UL 61010A-1 standard. These devices are: 120 volt, 20 amp GFCI receptacles, 240 volt, 20 amp duplex receptacles, light switches, fan switches and the Kewaunee Air Alert Alarm. Hoods that contain other devices or hoods that are not wired at the factory are not UL listed. All devices provided on Kewaunee hoods are UL listed.
In addition, fume hoods with Kemglass or Stainless Steel liners are listed under the UL 1805 standard.

What is the exhaust volume for an acid storage cabinet?

An acid storage cabinet vented through the hood work top will have an exhaust flow rate of approximately five to ten cubic feet per minute (CFM).

Should flammable storage cabinets be vented?

As a general rule, no. The NFPA 30 Flammable and Combustible Liquids Code discourages the venting of flammable storage cabinets. The purpose of the cabinet is to protect the contents of the cabinet from a fire in the lab. It is difficult to vent a cabinet without compromising its fire protection.

For More Information

For more information consult one of the following publications or organizations.

“Prudent Practices in the Laboratory: Handling and Disposal of Chemicals”
ISBN 0-309-05229-7
National Academy Press
2101 Constitution Avenue, N.W.
Washington, D.C. 20418
PH: 800-624-6242

ANSI/AIHA Z9.5 “Standards for Laboratory Ventilation”
Stock # 143-EQ-93
American Industrial Hygiene Association
2700 Prosperity Avenue, Suite 250
Fairfax, VA 22301
PH: 703-849-8888

American Society for Heating Refrigerating and Air Conditioning Engineers
1791 Tullie Circle, N.E.
Atlanta, GA 30329
PH: 800-527-4723

NFPA 30, 45, and 70
National Fire Protection Association
11 Tracy Drive
Avon, MA 02322-9908
PH: 800-344-3555

SEFA 1.1
Scientific Equipment and Furniture Association
7 Wildbird Lane
Hilton Head Island, SC 29926
PH: 843-689-6878

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