Boiler Manual - Weil-McLain

GV90+ gas-fired water boiler — Boiler ManualTroubleshooting (continued)CHART 2TSTAT CIRC & POWER lights flashingElectrical 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.Is return water temperature sensor clampedsecurely to the return pipe in the boiler?YesNo• Attach sensor to pipe with clamp provided.• Follow return temperature sensor checking procedureon page 76. Replace sensor if necessary.• Retest.• Check for stray voltage on the incoming thermostat wires.Disconnect the two external wires connected to the boilerthermostat wires.• Connect a voltmeter across the two incoming wires. Close eachthermostat, zone valve and relay in the external circuit one at atime and check the voltmeter reading across the wires. Thereshould NEVER be a voltage reading. If a voltage does occurunder any condition, check and correct the external wiring. (Thisis a common problem when using 3-wire zone valves.)• Once the external thermostat circuit wiring is checked andcorrected if necessary, reconnect the external thermostatcircuit wires to the boiler thermostat wires and allow the boilerto cycle.Did you find and correct a voltage across the two external thermostat circuit wires?YesNo• Boiler should now operate per the normal sequence of operation(Figure 75, page 65) if wiring was corrected.• Remove CIRCULATORS plug (Figure 93, page 78, Item 4)from plug receptacle of IBC.• Place voltmeter leads across the right-side 120 VAC N and120 VAC H pins of the CIRCULATORS receptacle.Does the voltmeter indicate 120 VAC?No• Replace IBC (IBC).• Retest.• Replace circulator harness.• Retest.Yes• Test wire continuity ofcirculator wire harness.Is harness ok?NoYesIs boiler internal Bypass circulator operating?NoYes• Check the boiler internal return pipe where it enters theboiler sections. The TSTAT CIRC and POWER lightswill flash as long as the return water temperature is lessthan 130 °F.• Wait up to 20 minutes to give the boiler and system achance to respond.Does problem persist?No• Boiler may now be operating normally.Verify against normal sequence ofoperation (Figure 75, page 65).Yes• Reconnect circulator harness to IBC.• Attempt to get the circulator started by giving it a sharp rapon the end of the circulator motor (to release a possiblylocked impeller).• If the circulator begins to operate, allow it to operate for afew minutes to see if the problem clears.• If problem persists, replace the Bypass circulator.• Retest.• If boiler appears not to be heating, troubleshoot boilerper CHART 8, page 88. If problem cannot be resolved,replace water temperature sensor and retest. Then replaceIBC (IBC) if sensor does not correct the problem.• If boiler is heating, but the temperature at the returnpipe does not increase above 130 °F, there may be anincorrectly-piped external circulator forcing water throughthe boiler. Check external piping and correct.82Part number 550-142-054/1211