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Boiler won’t fire

rbow85 Member Posts: 1
I replaced a old thermostat in zone 1 with a nest. It wouldn’t fire boiler. Zone 2 fires just fine with old thermostat. I removed nest and put the white and red wires together. Still wouldn’t fire zone 1. Checked voltage and I’m getting up to 28 volts to thermostat in zone 1. It’s an old burn ham boiler. Can anyone help me troubleshoot this.


  • rbow85
    rbow85 Member Posts: 1
    Also it is a two wire system just red and white.
  • rbow85
    rbow85 Member Posts: 1
    Here are some pictures
  • Jamie Hall
    Jamie Hall Member Posts: 23,276
    Well, first place the Nest won't work with just two wires, despite what their literature implies. So forget the Nest for the time being.

    Now. The boiler should fire when asked two by connecting the red and white wires together at the thermostat. If it does not, you need to find the other end of those two wires and try jumpering the terminals to which they are connected at that end (assuming, that is, that no one has altered that end of the wiring in any way). No joy? Well, what are those two wires connected to? A relay? A zone valve? Direct to the burner control? At this point a wiring diagram will help us a lot. On the other hand, if the burner works as it used to when you jumper the terminals as above, there is something amiss with the wires.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • bucksnort
    bucksnort Member Posts: 167
    Like above. When you were messing with the therm wires hooking up the Nest you could've broken a wire inside the insulation.
  • rbow85
    rbow85 Member Posts: 1
    Figured it out. Thanks. The zone 1 thermostat was only connected to the zone valve and zone two is connected to boiler.