Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Oil boiler runs automatically when no call for heat


Our oil boiler was supplying our indirect water tank but we had this removed and replaced with a heat pump water heater. The zone was closed and the lines capped off.

The two remaining zones are for our baseboard heat but the thermostats are set to low/off.

I read around and it sounds like there's an internal temperature that the oil boiler may be trying to maintain? If so, is it safe to just turn it off for the season? Seems wasteful that it kicks on like every 2 hours for a couple of minutes for no reason.


    HVACNUT Member Posts: 5,887

    What brand and model aquastat on the boiler?

    What relays are used for the heat zones? IOW, where do the thermostat wires connect at the boiler? What control(s)?

    If there are 2 temperature dials (Hi and Lo), it's either a dual, or triple aquastat. A triple will also have B1,B2,ZR,ZC,C1,C2. If it's a triple, are there wires connected to ZR,ZC?

    The existing controls and how it's wired will dictate whether or not converting to cold start is simple, or not so much, but doable.