Troubleshooting

Heater Does Not Operate

Visible pilot

Measure the flame signal when there is a visible pilot

 

 

 

 

 

 

Flame signal greater

No

 

 

 

 

than 1.25 VDC

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Yes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Check for proper airflow

 

 

 

 

(Direct Gas Start-Up Step #3)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pressure drop across the burner

No

 

 

between 0.625 and 0.675 in. wc?

 

 

 

 

 

 

 

 

 

 

 

Yes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Check the minimum firing rate

 

 

 

 

(Direct Gas Start-Up Step #4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Is the minimum firing rate

No

 

 

 

 

set correctly?

 

 

 

 

 

 

 

 

 

 

 

Yes

 

 

 

 

 

 

 

 

 

 

Does the flame signal

No

 

 

 

 

remain constant?

 

 

 

 

 

 

 

 

 

 

 

Yes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Note: The flame signal should be steady and above 1.25 VDC with a visible pilot.

(Reference Direct Gas Start-Up – Step #7)

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)

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 airflow can cause the flame to walk out of the burner and away from the flame sensor, causing the unit to recycle.

Adjust burner baffles

(Reference Direct Gas Start-Up – Step #3)

Adjust the minimum firing rate

(Reference Direct Gas Start-Up – Step #4)

If the signal slowly drops off, typically the airflow is too low

(Reference Blower Start-Up – Step #4)

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)

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.

Model VSU Make-Up Air 17

®

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Greenheck Fan VSU manual Visible pilot
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