Circulator pump leak at mounting flange (C) Daniel FriedmanCirculating Pump Never Stops
Diagnose & fix circulator pumpsthat just won't stop running

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Heating zone circulator pump wont' stop running: this article explains how to diagnose & fix a heating circulator pump that runs even when we are not asking for heat.

We explain that in some heating system designs, as long as the boiler has power the zone circulator is wired to run constantly - which can give some advantages in comfort and freeze proofing. But in areas where the heating system is not normally installed with an always-on circulator, if the circulator won't shut off something's wrong and we want it fixed. Here we discuss troubleshooting and fixing forever-on circulator pumps.

This article series describes how to diagnose & fix circulator pump problems on hot water or hydronic heating systems.

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Heating Zone Circulator Won't Stop Running

Question: un-wanted heat: why do zones get hot when we're not calling for heat?

(Mar 2, 2014) Jared said:

Why does heat come out of zones where thermostats are not calling for heat?


Jared, usually the problem you describe is traced to a check valve malfunction at the heating boiler or at the circulator pump (depending on what equipment is installed). Hot water can circulate by natural convection (warm water rises in pipes, cold water falls) even when the circulator is off.

Really?  in some heating areas including in Canadian homes, standard practice is to wire heating zone circulator pumps to run continuously during the heating season.

In these buildings the heating thermostat simply turns the heating boiler's burner or heat source on and off.

The effects of an always-on circulator assembly installation are more even heat and in some cases perhaps improved freeze-resistance for the heating system piping.

So depending on where you live and how your heating system is designed and controlled, it may be normal for the circulator pump(s) to run continuously.

We say more about this approach to heating water circulation in the reader Q&A just below.

Reader Question: circulator pump won't stop: the circulator pump stays on all the time

(Oct 23, 2011) Mary said:

Is it normal for a pump to stay on all the time? We have a new system installed and the pump wont go off at all. Thermostat set to 70 and burning smokeless egss.

(June 5, 2012) Greg said:

Didn't see anything listed above for this but it seems our hear came on last night and went off, but apparently the circulator was still running 2 hours later. So, we decided to turn it off at the switch. Any ideas what could cause this to happen? Before I left for work, i turned the switch back on, i heard the vent open on the pipe leading to the chimney then the furnace kicked on. In less than 5 minutes the furnace turned off but the circulator kept running.

4/23/2014 Chris said:

When the day's are warm and I turn off the heat do I shut the circulator pump off also?


Chris, when you turn off the heating system at its power switch your circulator pump should shut off on its own. If it does not then there is a wiring or control SNAFU that we need to discuss.

Normally you shouldn't have to do even that. If house temperatures are above the thermostat set temperature the thermostat will not call for heat and the heating system as well as its circulator should not run. If you are seeing something else happening let's figure that out. Tell me.

Reader follow-up:

4/21/2014 Dan, the heat was turned off this past Saturday. The circulator pump would still turn on though the heat was switched off on the thermostat. My centralized air and heat are on the one thermostat so I need to turn off heat to power on the central air unit.


Chris, you don't say where you are located; in some areas including much of Canada the hydronic heating system practice is to run the circulators continuously and allow the thermostat to simply turn the boiler on and off - an approach that tends to give more even heat and reduces the risk of heating line freeze-up in a colder climate. In the U.S. installers usually wire the thermostat to turn on the circulator and allow the boiler temperature to turn the burner on and off.

When you switch from HEAT to COOL mode on your system it would make sense for the circulator to turn off as well as your boiler. If it's not doing that we need to look at how your thermostat and circulator are wired and controlled. If you're one of the Canadian type installations you will want to find the power switch to the circulator pump and just flip that off as well, remembering that in the fall you'll need to turn it back on.

Part of the answer to this question depends on what heating system installation practices are common in your area. In the U.S. some areas a hydronic heating system is wired so that the thermostat simply turns the circulator pump on - ostensibly to move hot water from the boiler to the heated area.

In turn it's the temperature of the water in the system that, monitored by the boilers aquastat, turns the burner on and off.

If a problem at the heating boiler prevents its operation (such as no oil, or off on safety reset), the circulator may just keep spinnining away but no heat arrives in the heated area.

Take a look at the boiler to see why it's not running, starting

Reader follow-up:

Dan, I live in Hudsonville,Michigan.


Chris it's possible that the circulator relay on your boiler's aquastat or primary control (or circulator relay if you have multiple circulators) is stuck "on" and needs repair or replacement. Meanwhile just flip off power to the boiler - that should turn off the circulator. If it doesn't then look for an additional electrical switch.

Reader follow-up:

Dan, my furnance is a Burnham Holiday. It's natural gas. It's an old unit. There is one circulating pump with five Honeywell zone valves and five Honeywell thermostats. These thermostats are the old round types.


Chris in a single circulator system the circulator is usually turned on via a relay that is found inside the primary control or aquastat.

If your thermostat is not calling for heat the circulator ought not be running.

It might run if the thermostat wires are shorted together on any of the circulators controlling any of the zones.

The circulator might also run if any of the zone valves has a failed end-switch. When the thermostat calls for heat it activates a small motor in the zone valve that causes the valve to open. Once the valve reaches its full-open position, the valve closes an "end switch" that in turn activates the circulator pump itself.

Temporarily you can turn off the circulator by turning off power to the boiler - that should turn off the boiler motor and primary control and circulator pump.

To debug the problem I would check that all of our five thermostats (controlling each of the five zone valves) is OFF - NOT calling for heat (room temp is above thermostat set temp - or the thermostat is simply disconnected)

As needed I'd disconnect thermostat wires at the zone valve, and I'd check the primary control relay condition.

Keep me posted

Reader follow-up:

Dan, I'm curious as to why the the furnance and pump are even operating. I have the five thermostats set at sixty-four and the room temperature on every thermostat reads at seventy. Right now as I write the pump is working and the furnance is on but the burners are firing. The room temps on every thermostat still read seventy. Only one of the thermostats has a on,off switch.


Chris I have said too much and thus not been clear.

Let's diagnose just what's wrong by disconnecting things, one at a time.

  1. Go to the boiler (it's a boiler not a furnace, a furnace is a hot air system)
  2. Find each pair of thermostat wires coming from the various thermostats.
  3. Disconnect them one at a time - labeling if needed to avoid confusion. The reason for doing this at the boiler or circulator rather than at the thermostat is to rule out the chance that somewhere in their run the circulator wires are shorted together (thus calling for heat).

I suspect a bad relay, bad zone valve control, or thermostat wires shorted together somewhere. Shorting TT wires together is the same as a thermostat calling for heat.

Watch out: one can also be fooled, especially on hot water heating systems that use very quiet circulators such as some Taco brand units: the circulator may not be running at all. Hot water could be circulating by convection, thus also causing the boiler to run as cooler water returns to the boiler by convection.

It's easy to check this. Turn off power to the circulator pump (but not the boiler). If baseboards or radiators still are getyting hot AND the thermostat is not calling for heat (or has been disconnected entirely) then

Keep me posted


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