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Line voltage at thermostat

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Comments

  • FPDaFish_18
    FPDaFish_18 Member Posts: 14
    https://forum.heatinghelp.com/discussion/comment/1870841#Comment_1870841

    Thanks Ed. I'll take a look at all this tonight and see if I can explain what's going on in those photos. Thanks so much sir.

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 11,313

    The wires may go to something that looks like this.

    Screenshot 2025-11-04 at 2.22.47 PM.png

    You need a high limit to measure the boiler temperature and shut off the burner if the boiler water temperature gets too high.

    Edward Young Retired

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

    FPDaFish_18mattmia2
  • 109A_5
    109A_5 Member Posts: 3,080
    edited 4:05AM

    My guess from here is the wires at the Yellow circles controls the burner. Does the line voltage thermostat shut off the burner and the circulator ? Do the the Fuel bills seem abnormally high ? What is the mess at the Orange arrow all about ?

    image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • FPDaFish_18
    FPDaFish_18 Member Posts: 14

    I'm attaching a pic of the inside of the boiler. Ok so the 5 and 6 terminals on both R845A relays go into the boiler and get spliced together and feed whatever these controls inside the boiler are. The TT terminals on the bottom relay are the low voltage wire that goes to the basement nest thermostat. Hopefully the attached pic of the inside of the boiler is good because that's the best angle I could get. I'm in NY so yeah all my bills are unusually high. 🙃 Not sure if it's something out of the ordinary.

    PXL_20251105_021728990.jpg
  • 109A_5
    109A_5 Member Posts: 3,080

    " Do the the Fuel bills seem abnormally high ? "

    What I mean by this, is looking at the wiring I wonder if the boiler is running way more than it needs to be to heat the house since the T-T on the upper relay is just jumpered. With the only thing that shuts off the burner is the high limit switch (inside the boiler). However the system maybe wired so the line voltage thermostat simply shuts it all down, although I would think that would disable the other zone also.

    The wiring seems odd.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • FPDaFish_18
    FPDaFish_18 Member Posts: 14
    https://forum.heatinghelp.com/discussion/comment/1870943#Comment_1870943

    When I have tested both thermostats, the heat would kick on when I turned it up, and kick off when I turn it down. I think I'm gonna bite the bullet and get a heating guy to rewire it properly. If it was a simple run a new line thing I'd give it a go but I have a feeling I'm gonna have to go into the relays and boiler and disturb things that haven't been disturbed in as long time. Plus whenever I mess with wiring I sleep with one eye open for a month and I'm getting too old to deal. Thanks for all the advice. 👍

    hot_rod
  • 109A_5
    109A_5 Member Posts: 3,080

    OK, do what your are comfortable with, just make sure your heating guy has a real good understanding of these control systems and does not get confused and want to sell you a new boiler.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    FPDaFish_18

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