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No power to wall thermostat controller

Dominoser
Dominoser Member Posts: 4
in THE MAIN WALL

I have a Buderus BG142 with an AM10 controller. I tried to restart my unit by switching the breaker on. The circulating pump is working, the furnace has power as both the furnace controller and the AM10 show values.

My problem is that the furnace won't ignite as the central wall thermostat has no power. I guess the furnace is waiting for the temperature set point from that thermostat. I believe the power to that thermostat comes from the AM10 unit which seems to have power.

I looked at all the connections and everything seems fine.

Comments

  • HVACNUT
    HVACNUT Member Posts: 6,101

    The AM10 is a modulating reset control. Is it set up properly? What type of thermostat? Can you jump the wires at the thermostat?

  • Dominoser
    Dominoser Member Posts: 4

    I doubt it is a setup problem as it's been working without problems for 8 years. In the past, when I switched the breaker to the furnace, the thermostat went on. Now it's non-responsive.

    As for jumping the wires at the thermostat I haven't tried, what will that do? My understanding was that the thermostat was sending the ambiant temperature set point to the boiler. What would be the set point if i jump the wire?

  • Jamie Hall
    Jamie Hall Member Posts: 24,242

    What thermostat is in use here? Most thermostats (not all) send only an "on" or "off" signal, indicating the temperature is below or above a setpoint. In such cases, jumpering the thermostat wires at the control simulates an "on" signal — and if that turns on the boiler, either the wires are compromised or the thermostat itself.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • HVACNUT
    HVACNUT Member Posts: 6,101
    https://forum.heatinghelp.com/discussion/comment/1813517#Comment_1813517

    Is it a thermostat or a Buderus controller?

  • Dominoser
    Dominoser Member Posts: 4

    So i jumped the wire on the wall thermostat and the furnace started firing. So why is it that when the thermostat is properly installed there is no power going through it. It is not the thermostat itself that is at fault because I switched it with a working one and the same thing happens.

    Boiler.jpg
    jump.jpg
    Thermostat.jpg

  • HVACNUT
    HVACNUT Member Posts: 6,101
    edited October 10

    You switched it with a NEW thermostat? What thermostat?

  • Dominoser
    Dominoser Member Posts: 4

    Maybe i'm using the wrong term. What i consider the thermostat is the wall controller on which I program the set temperature. the last picture on the previous post.

    With a functional one. The appartment upstairs has the same set up. Same Buderus furnace, AM10 and same thermostat and it's functionnal. So I tried the upstairs thermostat on my wall connection and it does not light up. No power.

  • Jamie Hall
    Jamie Hall Member Posts: 24,242

    "So i jumped the wire on the wall thermostat and the furnace started firing. So why is it that when the thermostat is properly installed there is no power going through it. "

    I presume you jumped the R and W terminals? And the furnace fired up? That is the twisted pair of wires I see in one of the photos?

    Good. That means the wires are good. I think that that thermostat is a power stealing thermostat — which means, among other things, that it makes a difference which wire is connected to which terminal. Try switching the two around (take the one you had on R and put it on W and vice versa).

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • HVACNUT
    HVACNUT Member Posts: 6,101
    https://forum.heatinghelp.com/discussion/comment/1813654#Comment_1813654

    Ok. Wall controller. Thermostat. Tomato, Tomaddo.

    You swapped the thermostat, but you did not swap the sub base. As @Jamie Hall said, when the boiler started after you touched the wires together, it rules out a wiring or boiler issue. That test passed. You swapped thermostats. What's left?

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