Common Exhaust Fan Systems
The two most common types of fans are impeller fans and blower fans.
Impeller fans move air with blades similar to airplane propellers.
Blower fans look like hamster wheels - they are often called squirrel cage fans - and generally are more efficient than impeller fans.
- Most commercial kitchen exhaust systems have an exhaust fan, ducting and a hood. Some buildings have a central exhaust system, which is one or more fans, drawing air from the entire building (or parts of it) using a network of ducts.
A Heat Recovery Ventilator (HRV) also exhausts moisture and odors. An HRV is a self-contained ventilation system that provides balanced air intake and exhaust. Like a central exhaust fan, it can be connected to several rooms by ducting.
How good is your commercial kitchen exhaust fan: Is your fan...
not powerful enough?
not energy efficient?
a fire hazard?
How Do I Choose the Best Restaurant Kitchen Exhaust Fan System?
Choose the quietest, most energy-efficient exhaust fan or blower in the size range required. Most exhaust fan and blower labels have ratings so you can compare noise and energy efficiency. Look for a fan with replaceable parts and permanent lubrication. A fan suitable for continuous use is preferable. Be prepared to pay more for a quality fan.
Select low-resistance (smooth) exhaust ducting. Seal the joints and insulate sections that run through unheated spaces.
Place the exhaust hood where it will not cause moisture damage on exterior surfaces.
If you have heating appliances with chimneys, make sure that fans won't cause the appliances to backdraft.
Install the proper controls.
Things to Consider when Choosing a Commercial Kitchen Exhaust Fan or Blower:
Look for fans labeled 'low noise' or 'quiet,' and check for the HVI or db (decibel) rating. If it is not rated, there is a good chance that it will be noisy. Noisy fans are usually of lower quality, use more electricity and deteriorate until they cease to function. Older noisy fans can also be a fire hazard. Anti-vibration pads or foam tape can insulate the fan housing from wood joists and drywall.
Fan Power Requirements and Airflows
There is more to energy efficiency than selecting an energy-efficient fan. Ducting can affect fan performance. Un-insulated, undersized, or droopy flex ducting, ineffective or dirty backdraft dampers and exhaust louvers can cut rated airflow by more than 50 percent!
Fans create static electricity which attracts dirt like a magnet to the fan and housing. The dirt can encourage mold growth and restrict air movement. Clean fans, housings, back draft dampers and exterior flaps seasonally.
Weather Hoods, Grills And Backdraft Dampers
Even when fans are off, stack effects and wind loads may cause outside air to enter or inside air to exhaust through fan ducting. Check the flaps from time to time to make sure they are clean and working. The exterior exhaust flap or louvers should be clean and in good repair to maintain unobstructed airflow and reduce air infiltration. Most exhaust ducts are fitted with a single flap exhaust hood or triple louver aluminum or plastic exhaust grill. Use weather hoods that lie flat on the wall in driveways and other places where hood-type units could be damaged. Clean exhaust hoods of lint and nesting materials seasonally to ensure that the flap or louvers are not blocked or stuck open.
High Capacity Systems
High capacity, industrial or oversized exhaust fans, and range-top barbecue fans can cause chimney backdraft. Backdrafting occurs when air is drawn down chimneys, bringing dangerous combustion exhaust gases into the house. Avoid this by selecting sealed combustion heating appliances. If you have appliances with chimneys in your house, and you wish to install high capacity exhaust fans, you will need a matching supply air fan to balance house pressures.
Many ventilation contractors or salespeople are unaware of the effects of large exhaust fans on other house appliances. Make sure that your system is properly installed with supply air and that you have smoke alarms and carbon monoxide detectors to warn you if you have severe chimney back drafting.