Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

thermostat, like-for-like nothing fancy, but no go

Hello everyone. Thank you in advance for any pointers.
Steam boiler (Weil Mc EG-50), no cooling.
Old thermostat (White Rogers, 1F80-51) started to get wonky (e.g., partial display, temp not reliable). So I got a new version of the same (I believe) thermostat: Emerson 1F80-361.
Old had two wires running from boiler ("Y" on boiler's transformer to W thermostat; "G" on transformer to RH thermostat). Installed new, hooked up wires the same. Set to Slow Heating cycle. Thermostat display on, batteries good. Tap ^ to call for heat. But nothing.


  • Steve44
    Steve44 Member Posts: 5
    PS - to troubleshoot: if I unwire the new and re-wire in the Old thermostat, call for heat, then the boiler will fire and be happy.
  • fentonc
    fentonc Member Posts: 235
    Is the system switch set to “heat” mode?
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,590
    edited November 2022
    The new version of the thermostat is a programmable (has a clock feature for set back at the same time each day). The wiring diagram for heat only calls for a connection to the common wire on the boiler control transformer. The diagram from the new thermostat

    The old thermostat does not require a common wire as shown in this diagram. This is the diagram from the old thermostat

    Other than the need for a common wire and the clock setback feature, the thermostats are similar. According to the instructions, the new thermostat can work your system without a common wire. as listed here:

    Have you connected the 2 thermostat wires to W and RH on the new thermostat and is the Rc and the Rh jumper still in place?
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • Steve44
    Steve44 Member Posts: 5
    edited November 2022
    Thank you Fentonc and Ed - yes, in Heat mode, :] I have only wired the two wires, from Y boiler to W thermostat and G boiler to RH on thermostat (i.e., no C wire). I have tried both with jumper (RH-RC) and without jumper.
    I can try it again with jumper again and double-check Heat mode.
    Regarding C wire, there is a spare wire in bundle the wall (from basement to thermostat hole), so I could connect C (to have the dual-power option). Question: on boiler side, C-wire would connect to what terminal on the transformer? Transformer has Y, W, G, R, C. (With C connecting to green-covered wires, one of these to the metal junction box, so seems C here is grounding.)
    But even without C, the batteries (check and are full strength) should do it.
    thank you much.
    UPDATE: I tried with jumper RH-RC and checked Heat mode (on). No go still.
  • pecmsg
    pecmsg Member Posts: 4,696
    Does that transformer look like this?

  • Steve44
    Steve44 Member Posts: 5
    edited November 2022
    Hi Pecmsg - I can't see the photo you posted well enough. Here are two transformer photos of what I have. (Having the dual-power option would be nice but not a must-have.) On the board, I can see: Y, W, G (in the middle), C and R.
    and .

  • Steve44
    Steve44 Member Posts: 5
    Hi everybody - update, mid-morning Monday: I called White-Rogers/Emerson tech support and the fellow there thinks the new thermostat is bad & should return to store for a replacement, since it is not producing a soft click when I increase the set temperature higher than room temp or vice versa.

    If you all have an answer for where to connect the C wire, that'd be a bonus.

    Thank you again everybody. This HeatingHelp discussion board is one of the absolute best I've ever come across (for any topic). I have Dan H's book from when we moved into our house with it's steam and learned a lot from both the book and The Wall back then too. Thanks. Steve