Multiple heating zones with individual circulators (C) Daniel Friedman Circulating Pump Won't Run
Diagnose & fix circulator pumps that won't start & run in response to a call for heat

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Heating zone circulator pump won't start or seems stuck: how to diagnose & fix a heating zone circulator that will not run when it should.

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

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Diagnose Stuck or "Dead" Zone Circulators on Hot Water Heating Systems

Reader question: My heating zone circulator won't start-up

(Oct 29, 2011) Mark said:

I have a Weil-McLain furnace/boiler model no. CGM-5-PI. I just turned on the heat system two days ago and I noticed the circulator pump is not spinning its motor. I bleed all the valves on all the radiators.

The two upper levels get heat on the radiators, but the one on the entrance level is not getting heat. Is this caused by the pump not working? Is there any danger/risk of running the heat with the circulatory pump not working?

How much would it cost to replace the circulatory pump? Any information would be helpful. Thanks.

(Nov 24, 2012) annonymous said:

circulator pump goes on when heat called, runs thru cycle, but doesn't come again.....burners come on,but not circulator which in turn system goes off


Mark if the circulator pump won't start when the boiler temperature is sufficently high that it should, you would check:

1. the thermostat is calling for heat and the room temperature is below the thermostat set temperature

2. the boiler temperature is above the circulator cut-in temperature controlled by the aquastat

3. the circulator pump has power

4. the circulator relay has power and is switched "in" or callling for the circulator to run

5. the circulator pump itself is not damaged, jammed, frozen

In answer to your cost question, Grundfoss & Bell & Gossett heating zone circulator pumps are typically in the range of $100. to $300. depending on the pump model.

Question: should the circulator pump come on right away?

(Oct 27, 2011) Steve said:

My daughter bought a house with hot water heat. I bled the radiators, oiled the circulator pump and turned up the thermastat in order to check the operation. The circulator pump did not start to opereate until the boiler temp read 150 degrees.

The pump is hooked up to an aquastat (the thermastat located against the pipe exiting the boiler) which is set at 140 degrees. The radiators do heat up. Shouldn't the pump come on right away?


Steve, on a very common hot water heating system installation the aquastat is a combination control that includes a HI LO and DIFF setting - the LO and DIFF settings control the boiler when no heat is being called for and maintain heat in the boiler to provide domestic hot water through a tankless coil - that might not even be present or not in use on some installations.

If that general control and approach are in use on your system and if your system is hooked up in the manner typically used in the U.S. (not in Canada) the circulator won't turn on until the temperature is sufficiently high in the boiler.


Continue reading at CIRCULATOR OPERATION CHECKS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


If you are not getting any heat at all out of a cold baseboard or radiator,

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