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Wifi Thermostat with Burnham Independence steam boiler?

Dan_F Member Posts: 2
I would like to hook a Honeywell Wifi thermostat to my one-year-old Burnham Independence steam boiler. Until recently, I had only two wires (cloth!) to the thermostat, so during a recent renovation I had the electricians fish a new 5-wire line to the boiler. The electricians simply joined the red and white wires to the existing line in the basement. (When we had the boiler put in last year, the installer joined the new 2-wire from the boiler to the old wire from the other end).

My question is where to add a C wire in the existing wiring at the boiler. The system is basic: one zone, no cooling system. The boiler has a junction box, so I can’t simply connect the new wire to a terminal. I have posted a wiring diagram from the manual (.pdf)7, though, and some pics of the current setup. Can anyone point out where I can put a c-wire?

I’d really appreciate any advice that may have, too.


  • JStar
    JStar Member Posts: 2,752

    Do yourself a favor and install a switching relay. We use the Honeywell R8845U, as it has a defined common terminal and a control fuse (incredibly valuable little fuse!). Otherwise, we always have problems trying to hook the t-stat to the boiler's transformer common.
  • Dan_F
    Dan_F Member Posts: 2
    Good idea.

    Thanks for your reply. You mean install the relay in place of the junction box? Will that make things clearer, and can any contractor do it (or any homeowner)?
  • JStar
    JStar Member Posts: 2,752

    Keep all of the existing wiring, and install the relay separately. Any competent heating or HVAC technician should be able to install it. If you'd like to try it, ask yourself if you are 100% comfortable with it before actually doing it. If you are 99% or less, just don't.