FAQs on heating zone circulator pump won't start or seems stuck.

This article series explains how to diagnose & fix a heating zone circulator that will not run when it should.

Q&A on how to diagnose Stuck or "Dead" Heating Zone Circulators

These questions & answers about a hot water (hydronic) heating circulator pump that won't start or won't run were posted originally at CIRCULATOR PUMP WON'T START - please be sure to check out the diagnosis and repair advice given there.

On 2018-12-19 by George

Hot water circulating Pump running but no water being displaced whi

On 2018-02-17 by (mod) -

No JR

As long as the water in the hydronic heating system is hot, when the zone circulator runs the zone should get heat.

When water temperature drops the boiler should turn on.

On 2018-02-17 7 by JR

Does the zone where the circulator pump only get heat if the main boiler is running

On 2018-01-19 by (mod) - six Bell & Gossett motor/pumps on our boiler.

Larry

Look at (and attach a photo of using the picture frame next to the Comment button) the location of your circulator pumps.

Usually circulators are placed on the RETURN side of the boiler where their operation will be a little cooler and their life a little longer.

IN that location the circulator is pumping FROM the house and INTO the boiler on its return side.

And vice versa: if a circulator is (rarely) on the boiler outlet side it will be piping away from the boiler and into the house.

Follow the pipes.

In case it's not obvious, hot water leaves the boiler from a pipe high on or on the top of the boiler; returning, cooler heating water returns to the boiler from a pipe that feeds into the boiler at a lower location, typically near the boiler bottom.

On 2018-01-19 by Larry B.

I have six Bell & Gossett motor/pumps on our boiler. There is a pump for each zone mounted above where all of the motor/pumps join into a manifold.

My question is which direction should the pump pump? Toward the manifold (where all the pipes come together) or should the flow go opposite the manifold?

On 2017-12-04 04:27:48.996434 by (mod) -

Eric,

Set the thermostat the controls the Zone heated by the circulator in question all the way up so that we're sure it's calling for heat.

That interns should cause the circulator relay to close which should send power to the circulator pump itself. At that point if the wires to the pump are not seeing 120 volts then the problem is most likely not the circulator but instead the circulator relay control.

If you follow the circulator wires back you will find them connecting to the circulator relay.

On 2017-12-04 04:15:20.079854 by Eric Bettinger

Hopefully an easy question- My boiler turns on and heats water that extends up the outbound pipe about three feet, but my Grundfos circulator pump isn't turning on and circulating the water. The pump doesn't appear to be a fossilized relic due to fail, and it doesn't have a screw behind the nameplate to turn and ensure it isn't seized.

I actually purchased a replacement pump, but before I put it in, I'd like to check the system providing commands/power to the pump, and check any other possible reason the pump doesn't turn on.

( a secondary concern is that the new pump has three wire contacts (hot, neutral, ground) , and my old one just has two white wires running from the electrical control box to the pump, connected to the white and black pump wires with no obvious ground).

On 2017-02-04 16:52:30.440887 by Dori carter

I have radiant floor heating with five zones and my heater never shuts off what could be the problem I was thinking it could be the circle pump on one of them

On 2016-12-14 19:57:01.175104 by William Bertscha

Two zones baseboard hot water.Pipe hot coming out of one pump cold on the other.

On 2016-12-09 15:51:29.051444 by (mod) -

Hey Chip,

This indeed sounds like the boiler is reaching its cut-off temp without the circulator ever running. If the circ ran the boiler would be cooled by returning water and would run longer.

So check for a bad circulator relay.

On 2016-12-09 12:11:23.484449 by Chip

My furnace runs to temperature.

It will not circulate (pumpd does not turn on) then the furnace shuts off. When the water cools down in the furnace , the furnace will restart and run fine until it hits temp again and shuts off. No circulation why? Pump bad?

On 2016-04-04 by (mod) -

If the thermostat works and the circulator runs the system is calling for heat.

If the burner runs in response to one thermostat but not the other, and if both thermostats are able to turn on their respective circulators, I figure that the cold zone that's not lighting the boiler has no water circulating. (It's water temp that turns on the boiler in most system wiring setups in most countries) .

I suspect that your zone is airbound (or the circulator impeller is broken).

Search InspectApedia for AIRBOUND HEATING SYSTEMS to read the details.

On 2016-04-04 by Sheila

We have a gas hot water heating system with a with two circulators, one for the basement heat where there is a separate thermostat (#2.

When basement thermostat(#2)is turned up, the circulator turns on, but the boiler does not light and radiators are cool.

Kept(#2)high; and turning upstairs thermostat(#1) up,boiler starts,downstairs circulator continued to run, basement radiators got warm.

Why doesn't(#2)turn on oiler?

On 2015-11-02 by (mod) -

John

In the U.S. (if that's where you are) usually when you set the thermostat above room temp that turns on the circulator right away. If the circ doesn't run the common reasons are in the article above.

On 2015-10-31 6 by John

I have a Hydrotherm Mod.# 2HWS gas boiler with a Taco 110 circulating pump
I notice the pump is not going on.

In the past I always noticed the shaft spinning.
At what Temp. of the boiler should the pump start its cycle. What could be checked ? Thank You John

On 2015-10-13 by Dylan

Hello, I have an issue with my ciculator pump. It never turns on. There is never a power signal to the pump. I have a Honeywell aquastat, where it should get its power from. The burner also gets its power from the aquastat and that is working perfect. Any suggestions or ideas?

Thank yoy

On 2014-11-23 by (mod) -

Tim

The Taco has a field replaceable motor - that may be what's needed. Check first for a bad start/run capacitor.

On 2014-11-23 by Tim

My Taco series 110 circulator is not running at all. I can spin the impeller with my fingers.

It has oil in all three ports. It appears to be an always on pump as only on two wire runs to it from a switch. When I turn it off then on again it turns a few rotations then stops. The pump is fairly old as is the boiler (oil fired residential 1200sq ft home in Baltimore).

...

Continue reading at CIRCULATOR OPERATION CHECKS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• CIRCULATOR PUMP BASICS
• WHAT GOES WRONG WITH HEATING CIRCULATORS?
• CIRCULATOR DIAGNOSTICS
  • BYPASS a BAD CIRCULATOR
  • CIRCULATOR COSTS
  • CIRCULATOR NOISES
  • CIRCULATOR OPERATION CHECKS
  • CIRCULATOR PUMP LEAKS
  • CIRCULATOR PUMP MANUALS
  • CIRCULATOR PUMP MOTOR or BEARING FAILURE
  • CIRCULATOR PUMP MOUNT LOCATIONS
  • CIRCULATOR PUMP MOUNT POSITION
  • CIRCULATOR PUMP RELAYS & OTHER CONTROLS
• CIRCULATOR PUMPS vs ZONE VALVES

Suggested citation for this web page

CIRCULATOR PUMP WON'T START FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING BOILERS

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