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Part number 550-142-054/0411
GV90+ gas-fired water boiler — Boiler Manual
86
Troubleshooting (continued)
CHART 6
TSTAT CIRC light flashing and POWER light on steady
Electrical shock hazard — Wherever you see TURN OFF POWER, follow the instructions. Failure to follow
instructions could result in severe personal injury, death or substantial property damage.
• Attach sensor to pipe with clamp
provided.
• If problem persists, replace return
water temperature sensor.
• Retest.
• This is normal operation for
water less than 40 °F at boiler
internal return pipe.
• Condition should change after
a call for heat, when the boiler
will heat up the water.
• Reconnect circulator harness to the IBC.
• Attempt to get the circulator started by giving it a sharp rap on the
end of the circulator motor (to release a possibly locked impeller).
• If the circulator begins to operate, allow it to operate for a few
minutes to see if the problem clears.
• If problem persists, replace the bypass circulator.
• Retest.
• Replace the IBC (IBC).
• Retest.
• Replace circulator harness.
• Retest.
• Boiler is not heating.
• Troubleshoot boiler using
CHART 8, page 88.
• Boiler should now operate normally.
• Verify correct sequence of operation (Figure 75, page 65).
Is return water temperature sensor clamped securely to the return pipe in the boiler?
No Yes
• Remove CIRCULATORS plug (Figure 93, page 78, Item 4)
from plug receptacle of IBC.
• Place voltmeter leads across the 120 VAC N
and 120 VAC H pins of the CIRCULATORS receptacle on
the side corresponding to the circulator not operating.
Does the voltmeter indicate 120 VAC?
No Yes
Are both boiler internal circulators operating?
No Yes
Is there a call for heat?
• Verify by removing thermostat wirings at boiler and check-
ing continuity across external wires.
No Yes
• Test wire continuity of
circulator wire harness.
Is harness ok?
No Yes
• Wait 10 minutes to allow
heat from the boiler to
raise the water tempera-
ture.
Does LIMIT light quit flashing
(and pipes begin to heat up)?
No Yes
• This is NOT a lockout mode.
• The IBC is signaling that the return water temperature sen-
sor is detecting a temperature less than 40 °F.
• While the temperature at the boiler return water temperature
sensor is less than 40 °F, both of the internal boiler circula-
tors will run continuously, even if there is no call for heat
(though the boiler will not fire until the thermostat calls for
heat). This operation is intended to reduce chances of freez-
ing during system down times by keeping water flowing.