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Adding a 3rd call for Boiler ignition through an SR502

bhilton Member Posts: 51

I have an SR502 setup with zone 1 being my infloor heat (relay turns on the Grundfos for infloor heat) and zone 2 is my LifeBreath furnace that also has a Grundfos pump.

Everything is working as planned.

I've recently poured a new floor with infloor heat in my detached garage.

I have an SR501 left over that I want to use with a t-stat in the garage to engage the new Grundfos pump in the garage.

Is there a terminal on my SR502 I can use to connect a wire from the garage to simply tell the boiler to fire up?

Pic of my SR502 (before I wired it for the aforementioned zone 1 and zone 2).


Alan (California Radiant) Forbes


    HVACNUT Member Posts: 3,807
    On the SR501, jump 1 and 3, use N.O. 4 for the circulator. Run low volt from C 5 and N.O. 6 to the isolated end switch (XX) on the SR502.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 1,823
    Can you get a low voltage thermostat wire from the detached garage to the boiler? Then I would get the SR501 and do what @HVACNUT says above.
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • bhilton
    bhilton Member Posts: 51
    yeah I have a full tstat wire bundle going from garage into boiler room in the house.

    No issues connecting to Isolated end switch in the house, even though I already have a wire from the two zones in the house connected to those end switch terminals?

    Below is a pic of my SR501. It appears I already have a jumper in place, look good to you?

    I'll use N/O 4 for the power to the circulator.

    I'll run a low volt connection from bottom right N/O 6 and COM 5 to the end switch on the SR502?

  • Perfect. 

    On a call for heat, the pump will be energized and the dry contact (5 and 6) will close, telling the boiler to come on via the isolated end switch on the SR502. 
    Often wrong, never in doubt.
  • bhilton
    bhilton Member Posts: 51
    edited September 2020
    Thanks for all your help, I was able to take the N/O 6 and 5 COM from this SR501 in my garage into the house and on to the SR502 End Switch terminals. Worked like a charm. The garage in floor heat is ready for winter. :)
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