Library » FAQs » Kitchen Ventilation Systems
FAQs - Kitchen Ventilation Systems
Q: When do I use a Relay Box instead of a KFCC?
A: The relay box is much less expensive and you would use it instead of a KFCC if:
- Only one supply and one exhaust
- Single phase only
- Fans must have thermal overloads.
Q: Does Greenheck comply with International Mechanical Code (IMC) 507.2.1.1?
A: Yes, Greenheck has a heat sensing temperature interlock option that satisfies the IMC code.
Q: Who is the Greenheck representative in my area?
A: You can find your Greenheck representative by selecting the "Find My Rep" section on the homepage of Greenheck.com.
Q: What causes smoke and grease laden air to move horizontally and spill out from under a kitchen hood?
A: There can be many different reasons for this condition to occur. Consider the following:
- Not enough exhaust air for the cooking load.
- The kitchen hood is undersized for the application.
- Cross drafts in the kitchen.
- Excessive velocities from the face and/or air curtain registers.
- Not enough supply air brought back into the kitchen.
Q: When is it necessary to provide make-up air to a system?
A: Always. Codes like NFPA 96 require the following: "Replacement air quantity shall be adequate to prevent negative pressures in the commercial cooking area(s) from exceeding 0.02 in. water column (4.98 kPa)."
Q: What are typical applications for a Type I and Type II kitchen hood(s)?
A: According to the International Mechanical Code: "A Type I hood shall be installed at or above all commercial food heat-processing equipment that produces grease vapors or smoke. A Type I or Type II hood shall be installed at or above all commercial food heat-processing equipment that produces fumes, steam, odor or heat."
Q: What are the minimum and maximum allowable airflow velocities at the exhaust duct collar of a Greenheck hood?
A: Minimum = 1500 feet per minute. Maximum = 2100 feet per minute. (Except when used in a Variable Volume System, Minimum = 500 feet per minute)
Q: According to the National Codes what are the minimum allowable clearances for a kitchen hood?
A: Hoods, grease removal devices, exhaust fans and ductwork must have a clearance of at least 18 inches to combustible surfaces, 3 inches to limited-combustible surfaces and 0 inches to non-combustible surfaces.
Q: Are round duct collars available on U. L. Listed kitchen hoods?
A: Duct collars are available as square, rectangular and round configurations on U. L. Listed without fire damper type kitchen hoods. The maximum allowable size is dependent on the style of hood.
Round duct collars are not available on U. L. Listed with fire Damper type kitchen hoods.
Q: Can Greenheck provide an exhaust duct collar mounted on the rear or back of the hood?
A: Exhaust duct collars can be mounted on the rear of baffle filter style hoods at no additional charge. However, there is a limitation to this alternate location. The rear of the hood limits the maximum height of the exhaust collar to be 12" for canopy style and 10" for proximity style. Rear mounted exhaust collars are not available on Water Wash Style kitchen hoods.
Q: Can the exhaust duct collar be moved to the right or left of the standard centered position?
A: The U. L. Listing allows the exhaust duct to be located within 48" from the center of the hood to the center of the collar. However, construction limitations prevent the exhaust collars being placed within eight inches of the hood end panels.
Q: Can the exhaust duct collar be moved forward on the hood to give a greater clearance behind the duct?
A: The UL Listing allows the exhaust duct to be moved forward from the standard location. The maximum distance from the back of the hood the collar can be moved is based on the style of hood and the width of the collar. The farther forward the collar is placed the narrower the collar must be.
Q: Can a flexible duct connector be used to attach an exhaust duct to a utility set exhaust fan?
A: NFPA 96 2008 states the following: 8.1.3.4 The fan shall be connected to the exhaust duct by flanges securely bolted…..or by a system specifically listed for such use. 8.1.3.5 Flexible connectors shall not be used.
