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Troubleshooting
Heater Does Not Operate
Attempts to light, but no pilot (visible spark)
Check inlet gas pressure.
(Direct Gas Start-Up Step #1)
Yes
Gas pressure between the
minimum and maximum shown
on the direct gas label?
Air in the gas line?
No
Check for proper airflow
(Direct Gas Start-Up Step #3)
Yes
Pressure drop across the burner
between 0.625 and 0.675 in. wc?
Yes
Proper spark?
Yes
Check for proper pilot pressure
(Direct Gas Start-Up Step #2)
No
Pilot pressure correct?
Yes
16
Model VSU Make-Up Air
Note: The minimum and maximum gas pressures
for your unit are shown on the direct gas label.
(Reference Direct Gas Start-Up – Step #1)
No
(Reference Direct Gas Start-Up – Step #1)
Yes
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
(Reference Direct Gas Start-Up – Step #3)
No
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
(Reference Direct Gas Start-Up – Step #2)
With proper airflow, gas pressure and spark,
If problems remain, consult the factory
Correct gas pressure
Purge gas line
(Verify gas at the pilot)
Adjust burner baffles
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)
Adjust the pilot pressure
the unit should light.
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