Greenheck DG / DGX with Pilot Ignition (463555 IOM) (Pre-2008) - Manual (Page 37)

Troubleshooting
Does the flame signal remain
constant?
Measure the flame signal when
there is a visible pilot Note: The flame signal should be steady and above 1.25 Vdc
with a visible pilot.
Reference Direct Gas Start-Up Step #9
Flame signal greater than
1.25 Vdc?
Unit is not grounded
(Properly ground unit)
Flame rod is grounding out
(Adjust the flame rod to avoid contact with the burner or the unit)
Cracked porcelain on flame rod
(Replace flame rod)
Is the minimum firing rate set
correctly?
Adjust the minimum firing rate
(Reference Direct Gas Start-Up Step #6)
Check the minimum firing rate?
(Direct Gas Start-Up Step #6)
Note: Burners greater than 36 in. in length use an interrupted pilot. The
pilot is turned off 10 seconds after lighting the main burner and the flame
safeguard monitors the main flame instead of the pilot flame. If the
minimum fire is set to low, the flame safeguard may not be able to sense it.
Pressure drop across the burner
between 0.625 and 0.675 in. wc?
Note: When the pressure is low or marginal and the unit begins heating
the air density will change, this can cause the pressure to drop below the
minimum setting. Also, low air flow can cause the flame to walk out of
the burner and away from the flame sensor causing the unit to recycle.
Check for proper airflow
(Direct Gas Start-Up Step #4)
Adjust burner baffles
(Reference Direct Gas Start-Up Step #4)
No
No
No
Yes
Yes
If the signal slowly drops off, typically the air flow is too low
(Reference Blower Start-Up Step #6)
If it suddenly drops to zero, the flame rod is grounding out.
(Adjust the flame rod to avoid contact with the burner or the unit)
Yes
Yes
Heater Does Not Operate
Visible pilot
No
If the flame signal is above 1.25 Vdc and constant the main
gas valves will remain open until the call for heat is
interrupted, or the unit is shut down.
Troubleshooting
37