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Furnace seems like it's always running

Eric Masson
Eric Masson Member Posts: 4
I've got a hot water system with an oil burner. The hot water for the house comes via tankless coil in the boiler. There are two thermal zones and two thermostats. It seems like every 40 minutes or so, some part of the furnace comes on. Most of the time it's not the boiler, but maybe one or more of the circulators. I've disconnected both thermostats as a test, but it still comes on. I'm not using any hot water, and there are no leaky faucets. I just bleed both zones, so there's not a whole lot of air in the lines. Why would this be happening?


  • Brad White_9
    Brad White_9 Member Posts: 2,440
    Better go catch it.... :)

    Might be an internal aquastat or an outdoor reset aquastat independent of space-calling or DHW load controls. The occassional operation seems to coincide with passive loss rates which is what has me thinking this.

    If you kill the power to the entire unit and it still runs, call Father Sweeney at Our Lady of Perpetual Hot Water, then the Enquirer.
  • Steamhead (in transit)
    Steamhead (in transit) Member Posts: 6,688
    This is typical

    of boilers with coils in them. They have to maintain temperature all the time, which is quite wasteful. If you switch to an indirect tank or aquabooster, the burner will run less and you'll get more hot water. These units aren't cheap but will pay for themselves.

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