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Wiring Indirect Water Heater Thermostat to Taco SR501 Zone Control --- 24V??

Hi, have new indirect well mclain aqua plus. Thermostat appears wired incorrectly to Taco SR501 zone control.

Did not change wiring from old unit, connected to thermostat but something not right.

When heater is up to temp. Red zone light never shuts off, control makes buzzing sound, but no circulator or boiler fires. I think has to do w/ 24V connection?

Just joined forum and found this post which seems like my issue but need clarification if correct and if so, how to get the 24v power and what to do with it.

Called oil provider and he thought maybe zone needed to bled but I did that to all zones and don't think that is issue, something with the wiring.

Please see screenshots of thermostat and taco control for hot water zone.

Would appreciate any feedback and help. Thank you so much.

Did post topic here but don't know if anyone will see from older thread, sorry to post twice.



  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,844
    edited December 2020
    @Nikos10 This is your wiring diagram.

    Three conductor wire from the water heater thermostat to the switching relay. You need a jumper wire to connect the red wire from R on the Taco SR relay on 2 terminals of the water tank thermostat

    a third wire for the common or return path to operate the LED and onboard microprocessor of the water heater thermostat.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics