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Connecting boiler to existing thermostat

Folks, I need to attach the R&W wires from my boiler into the thermostat that currently controls my SpacePak A/C, which has four wires already attached, including a R wire as shown.

That existing red wire concerns me. Do I just put the R from my boiler into the same R terminal where the existing R wire is?


DIY'er ... ripped out a perfectly good forced-air furnace and replaced it with hot water & radiators.

Comments

  • Zman
    Zman Member Posts: 7,569
    Do you have wiring diagram for the t-stat?
    You want to be careful not to combine the power from spacepac with the boiler power. You could end up with 48 volts (and associated smoke).
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • newagedawn
    newagedawn Member Posts: 586
    to r or rc and w
    "The bitter taste of a poor install lasts far longer than the JOY of the lowest price"
  • HVACNUT
    HVACNUT Member Posts: 5,831
    edited September 2017
    Remove the jumper between R and RC.
    Put the red from your A/C to RC.
    Red from the boiler to R.
    White to W.
  • Boon
    Boon Member Posts: 260
    Zman I found the wiring diagram. I deserve a kick in the butt for not looking there first. It confirms what hvacnut says. Thanks all.
    DIY'er ... ripped out a perfectly good forced-air furnace and replaced it with hot water & radiators.