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Part Number 550-110-031/0605
Control Supplement — Standing Pilot Boilers
Troubleshooting continued
Is 24VAC present across combination control terminals V
2
& Z?
Is damper harness securely plugged in at both ends?
Secure connections.
Check for open thermostat, LWCO, high limit, spill switch or
rollout thermal fuse element contacts or check for loose
wire connections.
If LWCO, spill switch or rollout thermal fuse
element contacts are open, determine cause
and correct condition. Failure to do so will
cause severe personal injury, death or
substantial property damage.
Check/repair out of round stack section. Does vent damper
rotate open?
Is 24VAC present across transformer terminal V
2
and
yellow wire on vent damper connector?
Is 24VAC present across gas valve terminals?
Open thermostat contacts for 30 seconds. Vent damper will
rotate to closed position. Close thermostat contacts. Vent
damper will rotate to open position. Is 24VAC present
across gas valve terminals?
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
No Yes
Chart 2: Boiler will not fire — water boilers with tankless
Check for loose wire connections or bad combination
control.
No Yes
Is vent damper rotated open?
No
Yes
No Yes
Replace actuator.
Retest.
Check continuity of each wire in damper harness. Does
continuity exist for each wire? See Table below.
Replace damper
wiring harness.
Retest.
Replace gas valve.
Retest.
Is main flame on now?
No Yes
Retest
No Yes
No
Yes
No
Yes
No Yes
Replace damper
actuator. Retest.
Turn gas valve cock to
ON position. Retest.
Replace gas valve.
Retest
Is gas valve cock turned to ON position?
No
Yes