Greenheck VSU Installation, Operation And Maintenance Manual page 27

Troubleshooting
Heater Does Not Operate (Pilot Ignition)
Attempts to light, but no pilot (visible spark)
Check inlet gas pressure.
Reference: Start-Up - Direct Gas,
Check the Supply Gas Pressure, pg. 27
Yes
Gas pressure between the
minimum and maximum shown
on the direct gas label?
Air in the gas line?
No
Check for proper airflow.
Reference: Start-Up - Direct Gas,
Set the Burner Air Pressure Differential, pg. 16
Yes
Pressure drop across the burner
between 0.625 and 0.675 in. WC?
Yes
Proper spark?
Yes
Check for proper pilot pressure.
Reference: Start-Up - Direct Gas,
Check the Pilot Gas Pressure, pg. 15
No
Pilot pressure correct?
Yes
®
Note: The minimum and maximum gas pressures
for your unit are shown on the direct gas label.
Reference: Start-Up - Direct Gas, Check the Supply Gas Pressure, pg. 27
No
Reference: Start-Up - Direct Gas, Check the Supply Gas Pressure, pg. 27
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
Set the Burner Air Pressure Differential, pg. 16
No
Set the Burner Air Pressure Differential, pg. 16
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.
Reference: Start-Up - Direct Gas, Check the Pilot Gas Pressure, pg. 15
No
Reference: Start-Up - Direct Gas, Check the Pilot Gas Pressure, pg. 15
With proper airflow, gas pressure and spark,
Correct gas pressure.
Purge gas line.
Verify gas at the pilot.
Reference: Start-Up - Direct Gas,
Adjust burner baffles.
Reference: Start-Up - Direct Gas,
Crossed flame and spark wires.
Uncross wires and reconnect.
Incorrect spark plug gap.
Set spark plug gap to 0.062 inches.
Defective spark plug.
Replace spark plug.
Adjust the pilot pressure.
the unit should light.
If problems remain, consult the factory.
Model VSU Make-Up Air 27