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

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Steve44
Steve44 Member Posts: 5
in Thermostats and Controls
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.

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  • Steve44
    Steve44 Member Posts: 5
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    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: 237
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    Is the system switch set to “heat” mode?
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,852
    edited November 2022
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    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?
    Never Use The Parts Cannon.jpg

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    MikeAmann
  • Steve44
    Steve44 Member Posts: 5
    edited November 2022
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    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: 4,861
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    Does that transformer look like this?

  • Steve44
    Steve44 Member Posts: 5
    edited November 2022
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    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
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    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
    MikeAmann

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