Boiler Manual - Weil-McLain

GV90+ gas-fired water boiler — Boiler ManualTroubleshooting (continued)CHART 6TSTAT CIRC light flashing and POWER light on steadyElectrical shock hazard — Wherever you see TURN OFF POWER, follow the instructions. Failure to followinstructions could result in severe personal injury, death or substantial property damage.• This is NOT a lockout mode.• The IBC is signaling that the return water temperature sensoris detecting a temperature less than 40 °F.• While the temperature at the boiler return water temperaturesensor is less than 40 °F, both of the internal boiler circulatorswill run continuously, even if there is no call for heat(though the boiler will not fire until the thermostat calls forheat). This operation is intended to reduce chances of freezingduring system down times by keeping water flowing.• Attach sensor to pipe with clampprovided.• If problem persists, replace returnwater temperature sensor.• Retest.Is return water temperature sensor clampedsecurely to the return pipe in the boiler?NoYesAre both boiler internal circulators operating?• Remove CIRCULATORS plug (Figure 93, page 78, Item 4)from plug receptacle of IBC.• Place voltmeter leads across the 120 VAC Nand120 VAC H pins of the CIRCULATORS receptacle onthe side corresponding to the circulator not operating.Does the voltmeter indicate 120 VAC?NoYesNoYesIs there a call for heat?• Verify by removing thermostat wirings at boiler and checkingcontinuity across external wires.NoYes• Replace the IBC (IBC).• Retest.• Replace circulator harness.• Retest.• Test wire continuity ofcirculator wire harness.Is harness ok?NoYes• This is normal operation forwater less than 40 °F at boilerinternal return pipe.• Condition should change aftera call for heat, when the boilerwill heat up the water.• Wait 10 minutes to allowheat from the boiler toraise the water temperature.Does LIMIT light quit flashing(and pipes begin to heat up)?NoYes• Reconnect circulator harness to the IBC.• Attempt to get the circulator started by giving it a sharp rap on theend of the circulator motor (to release a possibly locked impeller).• If the circulator begins to operate, allow it to operate for a fewminutes to see if the problem clears.• If problem persists, replace the bypass circulator.• Retest.• Boiler is not heating.• Troubleshoot boiler usingCHART 8, page 88.• Boiler should now operate normally.• Verify correct sequence of operation (Figure 75, page 65).86Part number 550-142-054/1211