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Question on T-stat wiring on a Weil McLain Steam Boiler

Chris_108 Member Posts: 22
edited November 2021 in Thermostats and Controls
Hi guys,

I am a bit confused on my basic 2 wire steam heat T-stat wiring.... At the T-stat I have 2 wires: 1 going to R terminal and 2nd wire going to R/RC (jumper between R & RC)

so at the transformer on my Weil McLain Peg steam boiler the wires connect to terminals other then W & R. The W wire connects to Y terminal and the R wire connects to the G terminal. I always thought they should correspond the the same terminals at both ends? Am I mistaken?

Reason I am asking is I would like to replace my basic honeywell basic programable T-stat with a Ecobee 3 lite that I bought over a year ago but never hooked it up.

I realize Ideally I need a common wire which I don't think I have so I will need to look at the various options available but before I start to mess with this I want to make sure my existing wiring is ok and to be clear everything currently works as it should but was just surprised to not see the W and R terminal utilized on the transformer...

Any help is greatly appreciated...

thx in advance,


    HVACNUT Member Posts: 5,258
    Can you post some pics of what you have, and the wiring diagram?
    Should be R and W at the thermostat, and R and G at the fan center control but Y could also be used in the circuit.