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Troubleshooting
Problem: Exhaust fan is not operating or is not operating at design levels.
Is the fan receiving power?
Is the belt loose or broken?
Is the fan rotating in correct direction?
Is the make-up air operating?
Does the airflow need to be increased?
Does the fan vibrate?
Problem: Hood is full of smoke. There is smoke coming out of the edges of the hood.
Is the fan operating at design levels?
Is the fan correctly sized?
Are the filters in good condition?
Is there sufficient make-up air?
(Kitchen should be in a slight negative
but not excessive. Check to see if there
is a strong draft through an open door).
Does the current cooking equipment match
the original design?
Are there multiple hoods on one fan?
Are there closed dampers in the duct?
Is the ductwork complex or to small?
Is the ductwork obstructed?
Is this a short circuit hood?
Problem: Smoke blows away before reaching the bottom of the hood.
Are there cooling fans directed at the hood
or cooking equipment?
Are there ceiling diffusers directing air at
the hood?
Are there open windows or doors?
Are there cross drafts or other drafts in the
kitchen?
Is the hood near a main walkway?
Are there pass-thru windows near
the hood?
Is this an air curtain hood?
Is the make-up air part of the hood
or an attached plenum?
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Replace fuses, reset circuit breakers, check disconnect.
Replace or tighten belt.
Have the electrician correctly wire the fan.
Problems with make-up air may interfere with the exhaust fan - check the
manufacturer's installation manual.
Adjust or replace pulleys to increase fan RPM, install a larger motor.
Clean the fan wheel/blade, replace fan wheel if damaged, check for loose bolts,
check for broken or damaged components, check for rags and other foreign
objects.
See exhaust fan troubleshooting section.
Refer to test and balance report, design specifications and fan curves; have an
electrician check the motor amperage; try removing the filter temporarily to see
if capture improves. (Make sure to replace filter to prevent risk of fire!); switch to
different filters with lower static pressure.
Clean filters, replace damaged filters, properly position filters.
Check make-up air unit, increase make-up air, make-up air should be evenly
distributed throughout the kitchen.
Adjust or replace fan to match the cooking equipment load.
One hood may be over exhausting and the other hood not drawing enough.
Restrict second hood to help problem hood.
Open dampers.
Change to a higher static fan, modify the ductwork.
Clear obstruction.
Turn off or reduce the amount of air supplied to short circuit.
Turn off or redirect fans.
Move diffusers to more neutral area or replace with a diffuser that directs air away
from the hood.
Close windows and doors.
Find source of the draft and eliminate, add side skirts to hood (test with
cardboard; use stainless for permanent side skirts); increase the amount of
overhang on the spillage side; add a 6 in. (152.4 mm) lip around the base of the
hood (test with cardboard; use stainless for permanent side skirts); make-up air
should be spread out evenly through the kitchen.
Add side skirts to hood (test with cardboard first); increase the amount of
overhang on spillage side.
Adjust amount and locations of make-up air to eliminate drafts through the pass-
thru windows.
Turn off or reduce the amount of make-up air.
Try turning off or reducing the amount of make-up air; block off portions of the
supply to direct air away from the problem area (test with cardboard).
Kitchen Hoods • Type I and Type II
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