Troubleshooting
Heater Does Not Operate
Visible pilot
Measure the flame signal when there is a visible pilot
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Flame signal greater | No |
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than 1.25 VDC |
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| Yes |
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Check for proper airflow |
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(Direct Gas |
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Pressure drop across the burner | No |
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between 0.625 and 0.675 in. wc? |
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| Yes |
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Check the minimum firing rate |
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(Direct Gas |
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Is the minimum firing rate | No |
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set correctly? |
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| Yes |
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Does the flame signal | No |
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remain constant? |
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| Yes |
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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
®
