Control Supplement — Standing Pilot Boilers
Troubleshooting continued
Chart 2: Boiler will not fire — water boilers with tankless
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| Is damper harness securely plugged in at both ends? | ||||
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| Secure connections. |
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| No |
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| Check for loose wire connections or bad combination |
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| Is 24VAC present across combination control terminals V2 | ||||||||||
| control. |
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| & Z? |
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| No |
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Check for open thermostat, LWCO, high limit, spill switch or |
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rollout thermal fuse element contacts or check for loose |
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| Is 24VAC present across transformer terminal V2 and | |||||||||||
wire connections. |
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| yellow wire on vent damper connector? | |||||||||
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| If LWCO, spill switch or rollout thermal fuse |
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| No |
| Yes | ||||||
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| element contacts are open, determine cause |
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| and correct condition. Failure to do so will |
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| cause severe personal injury, death or |
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| Is vent damper rotated open? | |||||||
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| substantial property damage. |
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| No |
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Check/repair out of round stack section. Does vent damper |
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| Is 24VAC present across gas valve terminals? | |||||||||||
rotate open? |
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| No |
| Yes |
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| No |
| Yes | ||||||
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| Replace actuator. |
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| Retest. |
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| Is main flame on now? | ||||
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| No |
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Open thermostat contacts for 30 seconds. Vent damper will |
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rotate to closed position. Close thermostat contacts. Vent |
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| Retest | ||||||||||||
damper will rotate to open position. Is 24VAC present |
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across gas valve terminals? |
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| Is gas valve cock turned to ON position? | ||||||||||
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| No |
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| No |
| Yes | ||||||||||
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Check continuity of each wire in damper harness. Does continuity exist for each wire? See Table below.
No | Yes | |
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Turn gas valve cock to ON position. Retest.
Replace gas valve. Retest
Replace damper wiring harness. Retest.
Remove damper harness from damper harness plug. TEMPORARILY install jumper between terminal 2 and terminal 5 on damper plug in boiler wiring harness. See figure, right. Does boiler fire?
No | Yes | ||
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Replace gas valve. |
| Replace damper |
Retest. |
| actuator. Retest. |
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Part Number | 15 |