Boiler Circulator Pump Always Running

Discussion in 'Boiler Forum' started by jdbs3, Nov 29, 2011.

  1. jdbs3

    jdbs3 New Member

    Jan 24, 2008
    Not sure how long this has been doing this, but I just noticed that the Taco circulator pump on my home oil boiler is constantly running even though *none* of the 4 zones (3 heating and 1 domestic hot water tank) are calling for heat.

    The boiler was just cleaned last week, but I can't say it has been running since then, or if this started prior to the cleaning.

    Either way, I would expect the circulator pump would stop running if no heat is being called for, and the water tank is not calling for heat.

    Any thoughts on what the problem might be, or is this normal behavior?

  2. Dana

    Dana In the trades

    Jan 14, 2009
    It's not normal to run a circulator without a call for heat. What's powering the circulator? (Zone controller relay? The boiler's internal controls?)
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  4. jdbs3

    jdbs3 New Member

    Jan 24, 2008
    RE: What's powering the circulator? (Zone controller relay? The boiler's internal controls?)

    On the side of the boiler, there is a service switch box with an on/off switch that has 4 cable pigtails off of it, one each to the water heater, the boiler burner, a Honeywell aquastat and the circulator. The thermostat wires come into the Honeywell aquastat. Disconnecting either of the 2 thermostat wires in the aquastat stopped the circulator pump from running.

    The tech when he cleaned the boiler had placed a pencil at times behind a switch in the aquastat to force the furnace to run.

    Does this help answer your question?

    Thoughts? Comments?
  5. jdbs3

    jdbs3 New Member

    Jan 24, 2008
    Someone else I talked to said one of your zone valves may be sticking open or the relay for the circulator may be stuck closed.

    A zone valve was sticking. When the tech was here, he pulled down the lever on one of the zone valves to force the water to flow automatically through the system. He then placed the lever in the proper position before leaving.

    When I just touched this lever lightly, the circulator pump immediately went off. I retested the system (thermostat on, furnace run, thermostat off); the circulator pump stayed on again. Arg!

    I took another look at the zone valve and noticed it was not seated properly, possibly off its proper position by ~5 degrees. When I just touched the zone valve (not the lever this time), the circulator pump again went off immediately.

    I reseated the zone valve correctly and retested the system. This time when I turned down the thermostat to this zone, the circulator pump stopped immediately. Problem resolved.

    My guess is that the tech nudged the zone valve off its proper seat when he reached up to pull the zone valve lever down, or when he placed it back in the proper position.

    Regardless, problem resolved and service call cancelled.
  6. BadgerBoilerMN

    BadgerBoilerMN Hydronic Heating Designer

    Mar 4, 2011
    hydronic heating designer/contractor
    Many of my hydronic heating designs include the use of a full time circulator but one of the zones should be open. Without a call for heat, the main boiler relay should not call the pump on. It is possible that the technician caused the problem. I would call him back to diagnose it. jd may have it but it depends on the zone valve in question.
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