Greenheck Fan Make-Up Air Unit VSU - Manual (Page 16)

16 Model VSU Make-Up Air
® ® ® ® ®
Heater Does Not Operate
Attempts to light, but no pilot (visible spark)
Troubleshooting
Gas pressure between the
minimum and maximum shown
on the direct gas label?
Check inlet gas pressure.
(Direct Gas Start-Up Step #1)
Air in the gas line?
Purge gas line
(Verify gas at the pilot)
Check for proper pilot pressure
(Direct Gas Start-Up Step #2)
Pilot pressure correct?
Crossed flame and spark wires
(Uncross wires and reconnect)
Incorrect spark plug gap
(Set spark plug gap to 0.062 in.)
Defective spark plug
(Replace spark plug)
Proper spark?
Adjust burner baffles
(Reference Direct Gas Start-Up – Step #3)
Adjust the pilot pressure
(Reference Direct Gas Start-Up – Step #2)
Pressure drop across the burner
between 0.625 and 0.675 in. wc?
Check for proper airflow
(Direct Gas Start-Up Step #3)
Note: The airflow may satisfy the airflow switch,
but may make lighting the pilot difficult. Adjust the
pressure drop across the burner between 0.625 and
0.675 in. wc shown in Direct Gas Start-Up – Step #3
No
No
Yes
Yes
Yes
No
Yes
Yes
No
With proper airflow, gas pressure and spark,
the unit should light.
If problems remain, consult the factory
Note: A high pilot pressure will make lighting more
difficult. Lower the pilot pressure in increments
until the unit lights. Then set the pilot per the
instruction in Direct Gas Start-Up – Step. #2
No
Note: The minimum and maximum gas pressures
for your unit are shown on the direct gas label.
(Reference Direct Gas Start-Up – Step #1)
Correct gas pressure
(Reference Direct Gas Start-Up – Step #1)
No
Yes