Boiler Manual - Weil-McLain

GV90+ gas-fired water boiler — Boiler ManualTroubleshooting (continued)c. Immediately disconnect the return temperature sensor plug fromthe IBC.d. Measure the resistance of the sensor. Write down the result.e. Let the sensor cool to room temperature and measure the resistanceagain. Write down the result.f. Compare the sensor resistances at both temperatures to the closesttemperatures in Figure 91.g. If the measured values are within 10% of the values listed, the sensoris good. If not, replace the sensor. See Replacement parts forthe part number.3. Fixed resistor methoda. With the boiler power OFF, disconnect the return temperaturesensor plug at the IBC.b. Insert a 2500-ohm resistor into the IBC sensor plug.c. Restart the boiler.d. If the boiler operates with the resistor, but not with the sensor, tryreplacing the sensor. See Replacement parts for the part number.Figure 91 Return temperature sensor resistanceTemperature°FResistanceOhmsTemperature°FResistanceOhms60 15300 140 248070 11900 160 168080 9310 180 1160100 5840 200 810120 3760 212 674Figure 92 GV90+ Integrated Boiler Control (IBC)IBC (integrated boiler control)Make sure ground wiring is installed per wiring diagram. Good groundingis extremely important for proper operation.Solder or water splatter between plugs and circuit boardcan cause improper operation of IBC. Place a shield over theboiler internal controls and components during installation.Failure to comply could result in severe personal injury, deathor substantial property damage.IBC indicator lights — lockout modes• See Charts 1 through 8 in this section for detailed trouble-shootingprocedures.• To reset control after a lockout, turn off power at the 120 VAC serviceswitch or turn down all thermostats. Wait 45 seconds. Then restorepower and call for heat.• After an over-temperature lockout (POWER and LIMIT lights flashing),the control will only reset after interruption of 120 VAC for 45seconds. (And temperature at return water temperature sensor mustbe below 240°F.)POWER light flashing alone• Usually indicates reversed polarity of 120 VAC power wires.POWER and TSTAT CIRC lights flashing• Usually indicates stray voltage on external thermostat circuit wiresor return water temperature entering boiler sections has not reached140°F within 20 minutes.POWER and LIMIT light flashing alternately• Usually indicates that limit circuit failed to cut off boiler at high temperature— return water temperature sensor has sensed water over235°F.POWER and PRESS SWITCH lights flashing• Usually indicates pressure switch is closed when it should not be, orpressure switch failed to close within 5 minutes of blower starting.POWER and FLAME lights flashing• Usually indicates control has had three unsuccessfulignition attempts or sensed flame when it shouldn’tbe there. Boiler may not be properly grounded.IBC indicator lights —non-lockout modesTSTAT CIRC light flashing alone• Usually indicates return water temperature sensordetects water at boiler return pipe less than 40°F.Both internal circulators will run continuously,even with no call for heat, until temperature rises.LIMIT light flashing alone• Usually indicates an open or shorted return watertemperature sensor.Troubleshooting the IBC• See Figure 93, page 78 for location of harness plugreceptacles and plugs on the IBC.Part number 550-142-054/1211 77