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Taco SR504-EXP-4 Need Help Hooking Nest E To C Wire.

Hello, I had the Argo AR861 Switching Relay and I noticed it did not have a c wire so I couldn't connect the nest thermostat for the c wire. So I purchased the Taco SR504-EXP-4 to get the c wire to work for 2 thermostats. I am confused on what I need now to power the thermostats. Do I need external transformer or do I need a rib-u1c relay to power it? Is the internal transformer enough to power 2 or just 1 thermostat? I have the 3 zones.


  • SteveSan
    SteveSan Member Posts: 102
    Good morning mirsomali, you should be ok with 2 Nest connected to the Taco relay. In the future if you are going to add a third zone you will need an external transformer. Please give us a call anytime Mon-Fri 8am-5pm EST. 401-942-8000
    Erin Holohan Haskellethicalpaul