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Circulator pump sources, circulator pump installation & repair manuals

Hot water heating circulators or circulator pumps: install, troubleshoot, repair advice: this article series discusses Circulator Pumps: how to find, inspect, diagnose, and repair problems with Hot Water Heating System Circulator Pumps or circulator pump relay switches and controls.

This article series answers most questions about Heating System Boiler Controls on central heating systems to aid in troubleshooting, inspection, diagnosis, and repairs.

Circulator pump relay switches & controls on heating systems: Troubleshooting & Repair Guide, How to tell if a heating circulator pump is working, Why do some heating zones work and others not, why does heat come out of zones where thermostats are not calling for heat?

How to fix an air-bound heating system and blocked circulator pump,

How to cure circulator pump noises, Where should a circulator pump be installed on a heating boiler? On the inlet or on the outlet side of the boiler? Use of air exit tanks and circulator pumps on heating boilers.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Install, Dagnose & Fix Heating Circulator Pumps

B&G Red Circulator Pump (C) Daniel FriedmanHeating circulator pumps or "zone circulators" are used to force hot water from the heating boiler through radianting devices such as hot water baseboards or radiators. The circulator is switched on as needed or in some designs may be wired to run continuously.

Our photo at left of a red B&G heating circulator pump shows equipment more than twenty years old and still spinning along nicely.

Proper installation, protection from leaks, and lubrication at annual service can give a long circulator life. Poor maintenance or improper installation can give less happy results.

[Click to enlarge any image]

After a brief introduction we describe what goes wrong (or how to get things to go right with heating zone circulator pumps.

We also link to related articles for circulator choices, installation, troubleshooting, repair or replacement.

Also see Checks for Circulator Operation.

How Hot Water Heating Circulators Work: One vs Multiple Circulators

Multiple heating zones with individual circulators (C) Daniel Friedman

Hot water may be circulated throughout multiple zones using a single circulator pump and individual zone flow control valves, or each heating zone may be built with its own individual circulator pump.

Either approach to individual heating zone control can work just fine - using zone valves or using individual circulators.

Our photo above shows a single circulator system (no zone valves are in the photo - this may be a single-zone heat system) while at left our photograph shows a three-zone heating system with three B&G circulators in a home in Two Harbors, MN.

You'll notice that one of the circulators has been replaced with a newer Bell & Gossett Circulator SLC-30.

See MULTIPLE HEATING ZONE CONTROL for as much argument as you can stand about multiple circulator pumps versus multiple zone valves for heating zone control.

What goes wrong with hot water heating circulator pumps and circulator switches?

Leaky circulator pump (C) Daniel Friedman

The heating system circulator pump, such as the trio of pumps shown at the top of this page, is used to move hot water from the heating boiler out through one or more loops of piping in a building, through heating devices such as radiators, heating baseboards, or convector units, then through return piping back to the heating boiler.

When the water temperature drops to a pre-set level the heating boiler will re-heat the water.

[Click to enlarge any image]

The circulator relay is an electrical switch which, in response to a request for heat from a thermostat, turns on the circulator pump.

See RELAY CONTROL SWITCHES for details about how the circulator pump relay operates.

Single Circulator Heating Systems, One or Multiple Heating Zones

Some heating systems use a single circulator to move hot water through the building's heating devices (convectors, radiators or baseboards).

In a one-circulator system, the building may still divide its heat into various zones or sub-areas of individual heat control, by using either individual radiators in rooms or perhaps by using electrically controlled zone valves which open and close flow of hot water through sub-loops in the building heating piping.

Also see ZONE VALVES, HEATING - home.

Even a single zone heating system might use two circulator pumps. In this case the second circulator is being used to control a separate indirect-fired water heating system to provide domestic hot water for washing and bathing.

See INDIRECT FIRED WATER HEATERS.

Multiple Circulator Heating Systems, Multiple Heating Zones

Some heating systems use multiple circulators to provide heat to individual building areas or "zones".

In this case each heating zone will have its own thermostat which, acting as a low-voltage "heat on-off switch" will turn on individual circulator pumps when heat is desired in that zone.

Details are

at CIRCULATOR PUMP RELAYS & OTHER CONTROLS.

Also see RELAY CONTROL SWITCHES for details about how circulator relay controls work.

Mixed Multiple Circulator Heating Systems Plus Zone Valves

Less common are mixed heating zone systems in which multiple circulators are used but one or more of the circulators feeds a heating water pipe which is subsequently divided into additional sub-zones of heat control, each sub-zone being controlled by a zone valve.

We often see this arrangement when the building owner/manager wants to sub-divide an existing heating zone into multiple zones of control.

Circulator pump leak at mounting flange (C) Daniel Friedman

Before assuming the heating system is not working when the thermostat is calling for heat, feel the radiators or baseboards to see if they are getting hot.

On a call for heat at the thermostat, if the heating boiler is already hot (above the lower limit or cut-in temperature) then the circulator should turn on and move hot water to the baseboards or radiators.

Click to enlarge any image]

Only after the boiler temperature drops below the cut-in temperature will the heating boiler turn on to re-heat the water. The connection between the thermostat and the heating boiler turning on or off is indirect.

On most heating systems the thermostat turns the circulator pump on or off and the temperature of the heating water turns the heating boiler on or off.

Our photo (above left) shows leaks at the circulator pump mounting flanges. Notice those rust stains on the bottom circulator mounting flange.

See CIRCULATOR PUMP LEAKS

Circulator pump mount (C) Daniel Friedman


If the boiler runs but the heating baseboard or radiators in an area do not get hot, the problem could be

Honeywell room thermostat

If the heating boiler itself if does not turn on in a response to a call for heat 

see NO HEAT - BOILER.

Circulator Pump Failure or Noise Diagnostic Checklist

Ambrol BoilerMate WH-7P circulator pump issues (C) InspectApedia.com Randall SmithQuestion: repeated failure of circulator pump on tankless water heater

2019/01/23 Randall Smith said:

We had a circulator on our indirect HW heater die (loud noises) and replaced. This had initial problems due to air in the pipes, but once fixed there was little/no hot water and within a day the new circulator died as well.

Plumber suggested a control value that is supposed to control flow was broken and opened it fully, noting this would make the hot water very hot (adults only in house) and would need to be fixed properly soon.

Now, however, we are hearing the new circulator struggle with loud humming noises. Any ideas? Many thanks!

This Q&A appeared originally at INDIRECT FIRED WATER HEATER FAQs

Reply: some diagnostic checkpoints for noisy or failed circulator pumps: Causes & Effects

Randall

Thanks for an interesting and also of course troubling question. One can but suspect that we have not gotten down to the root cause of the problem.

It would be helpful to have

It's not clear to me how an anti-scald valve (I think that's the device your plumber calls a control valve) would cause circulator pump failure. Hydronic heating circulator pumps are designed to handle boiler water at the temperatures that occur normally in the heating system - up to close to 200 degF.

Obvious & Subtle Causes of Heating or Hot Water Circulator Pump Failure

 

Circulator pump company contact information & installation & repair manuals

 




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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2020-11-05 - by (mod) -

If I understand the wiring question properly this quote from a typical Lochinvar manual may be useful:

The sidewall fan/powered vent cap MUST be interlocked with the units control system to start the fan on a call for heat and prove fan operation before the boiler fires.

Watch out: However rather than speculate and with the apology that I just don't know enough about the system you're discussing to have a confident opinion that it is safe or unsafe, why don't you give the boiler manufacturer a call and ask them directly. That would be the most authoritative source.

See the contact information as well as a list of boiler manuals found

at LOCHINVAR HEATING BOILERS or call their Technical support: 800-722-2101

On 2020-11-05 by Anonymous

Because the son-in-law thinks credentials carry more weight. It must be fine if the tech said so.

To me it's insanity to leave the ignition interlock disconnected, but it's not my call. I just want to be sure it's not dangerous.

On 2020-11-04 - by (mod) - Lochinvar CBN-135M9 boiler system also has the flow switch wired to the outdoor temp sensor input

Zap

I don't know for sure.

Why not ask the tech to return and restore the wiring to the manufacturer's specs?

On 2020-11-03 by zapster

My daughter and son-in-law have a Lochinvar CBN-135M9 boiler system with 4 zone controls. It also has the flow switch wired to the outdoor temp sensor input. According to the installation manual it should be wired to an ignition delay circuit to keep it from firing if the circulator isn't running.

It was apparently installed that way initially (2014) and has been heating since then, tho one upstairs circuit is very difficult to bleed the air out of. They had an HVAC guy come out to clean and inspect, and he left the wiring as-is. This strikes me as possibly dangerous--the ignition lockout is disabled, and the temp sensor is seeing a dead short across it.

Should we be worried about this weird arrangement?

Could the short across the temp inputs be holding the pressure down to account for the bleed difficulty?

On 2020-10-30 - by (mod) -

Jim

If you remove the thermostat wires and then jumper the two thermostat terminals right on the zone valve does it open? And when it opens does the circulator start? Does this zone have its own separate circulator?

If so, because Taco circulators are so quiet, you may need simply to feel pipes to see if the outlet side of the circ gets hot when calling for heat;

Keep in mind that the heating zone could simply be airbound (search the ARTICLE INDEX for AIRBOUND HEATING SYSTEMS to see what to do) or your hydronic water-to-air unit itself could be blocked, air-bound, or have a fan that's not working.

On 2020-10-30 by Jim

1 zone is not working. Heat or ac. Hydronic air with circulator pumps. Heat works fine in other zone. Hot water zone works as well. System is 8 years old. Everything has always worked. Batteries in thermostats replaced. I even swapped out each thermostat. Same zone still doesn't work. I swapped out cubes in taco switch relay with other zone

. Still doesn't work. Fuse is good. All thermostat wires are tight. I'm thinking its circulator pump grunfos 3 speed. One thing to not when thermostat clicks for heat the red light does not come on for that zone. (Would light still come even if circulator pump is bad.

On 2020-10-24 2 by Victoria Lazier

We had a radiant underfloor hydronic system installed 4 years ago. We have already had 3 pumps fail. Is this to be expected or is it due to underlying issues that at be related to poor installation.
Thank you

On 2020-04-30 0 - by (mod) -

Let me know if that works for you

On 2020-04-30 - by (mod) -

Yes there will be a separate circulator switch. Follow the wires

On 2020-04-29 by Anonymous

thank you so much for your response, I guess I was not very clear, I am in Canada, I have turned the fuse for the heater off but every once in a while (not constantly) the circulator will come on,

so if I understand you correctly there is a separate switch for the circulator? I am a widow whose husband looked after all this and I am sorry to sound so ignorant.

On 2020-04-29 - by (mod) -

Anon:

Depending on where you live, your heating system may have been set up so that the circulator runs continuously, with the room thermostat's turning the boiler on and off as needed on a call for heat. That's how hot water (hydronic) heating systems are usually installed in Canada.

In the U.S., more-often the thermostat turns the circulator on and off and the water temperature turns the boiler's burner on and off as needed.

So if yours is an "always-on" installation then you'll want to find the separate electrical power switch for the circulator(s) and flip it off - taking care to remember to turn in back on at the start of heating season.

If yours is NOT a "circulator always-on" system, then I would look for shorted thermostat wires or a stuck circulator relay that needs repair or replacement.

Thanks for asking a helpful question. Let me know what your service tech finds.

On 2020-04-29 by Anonymous

I have infloor heat and in May turn the heat off but often I hear the circulator going . It is eaten by electric

On 2020-03-08 - by (mod) - short hot water circulator life on an indirect-fired water heater system

KT

This is certainly a troublesome problem report: short hot water circulator life on an indirect-fired water heater system.

I agree that steam heat boilers often produce a lot of scale as well as rust and crud - which is why the steam controls like the boiler Low Water Cutoff need to be flushed monthly.

So we're circulating silty steam boiler water from the steam boiler's water reservoir through the heat exchanger in the indirect water heater. And you report that's killing the circulator pumps.

I would discuss with your service tech

1. do we need to go through a more-aggressive cleanout flush of the steam boiler?

2. do we need to use a water conditioner or treatment additive in the steam boiler to reduce the rust and scale problem?

(those are good for the boiler and heating system as well)

3. should we install a large particle filter in the indirect water heater line from the boiler ahead of the circulator pump?

4. Should we be installing a scale-tolerant circulator pump? Grundfos, Taco, Liang and Watts all make circulator pumps that can tolerate some scale in the heating water.

On 2020-03-07 by KT

12 yr. old Amtrol indirect-fired water heater's 3d circulation pump is failing, extremely noisy and struggling.

Tank is still fine, apparently-- way past warranty of course.
Amazing actually that any pump could survive, handling that rusty sludge from cast-iron steam pipes! Anybody know if its longevity is typical? About to have it replaced--

On 2019-01-23 by Randall Smith - new B&G Ecocirc 19-16 CCFXYZ

Thanks for the help! I've attached one image (can't seem to figure out how to do multiples) that shows the circulator, the water heater, and the pipes connecting them.

The new circulator is a B&G Ecocirc 19-16 CCFXYZ. The other (older) circulators for the house heat are by Taco, model 007-F4.

The water heater, if it matters, is an Amtrol 'Boiler Mate' WH-7P (41 gallons).

The operating temperature at the boiler is set at 190 now, had been 220. When doing the initial repair the plumber felt the ~200F+ & ~20psi was too high and reduced it to 190F max and 15psi. Not sure if this is related to our current problems.

On 2019-01-23 by (mod) - troubleshooting indirect water heater circulator pump failures

Amtrol WH-series indirect water heater piping details (Recommended) with separate circulator, adapted from Amtrol BoilerMate(TM) IO Manual cited in detail at InspectApedia.com (C) IAP 2019Yep, Clark Van Oyen's comments box code only permits one image per comment, but of course one can post multiple comments (and images at one per).

220F is too hot for a normal boiler and risks dumping at the TP Relief valve.

The best aquastat settings would be HI 200, LO 20 or more below the HI,

I might keep the DIFF circuit working and set DIFF to the max or 25. to keep heat in the boiler to speed response when the indirect heater ("zone") wants help from the boiler.

The indirect water heater runs as what looks to the boiler and aquastat as simply another heating zone.

Amtrol warns against scalding hazards and recommends a tempering valve.

If you give us the brand and model of your tempering valve we can be sure we've found the installation instructions and proper positioning information.

The sketch above is adapted from the Amtrol BoilerMate™ WH-series INSTALLATION MANUAL [PDF] (2012) AMTROL, 1400 Division Road, West Warwick, RI 02893 T: 401.884.6300 F: 401.885.2567 www.amtrol.com

Reader Question: radiator exploded after circulator pump repair

(Jan 30, 2014) Heather said:

I have a boiler for heat in my home with two circulator pumps that supply two different zones (upstairs and downstairs).

My circulator pump for the first floor went bad and was replaced, fixing the problem. The boiler itself had no issues.

An hour later, a radiator upstairs (different zone supplied by the other circulator pump) exploded and a 6 inch piece of metal was cast from the radiator causing water to flood the house.

This happened in a different zone connected to the other pump from the same boiler.

Could the exploded radiator in the other zone have been affected by the replacement of the circulator pump to the other zone?

I cant understand how this coincidentally happened when there seemed to be no problems with the supply to the zone on the second floor where it happened. Any feedback is appreciated.

This question was originally posted at HEATING SYSTEMS

Reply:

Heather,

This sounds horrible - and peculiar. Forensic investigators start by disbelieving coincidences.

But it's not clear why a radiator would explode under any circumstances. Really "explode" ? We're talking about hot water heat, at normal pressures under 30 PSI.

Watch out: if your heating system pressures were abnormally high (over 30 psi) then either your system was missing a critical safety device - a Temperature/pressure relief valve at the boiler - or the valve was installed but was jammed, or subverted, or not working.

IF that is is the case this is a VERY DANGEROUS condition as an exploding boiler can cause a BLEVE explosion of tremendous force. (Search InspectAPedia for Bleve explosion to read Details).

In short, a normal hot water heating circulator pump does not have great pumping power; if there was an overpressure problem in the system it seems more likely it came from another component. Naturally everbody involved in working on your system will be scared to admit fault. Focus on a thorough inspection of the heating boiler starting with

- the location, type and condition of pressure/temperature relief valve
- the normal operating pressure and temperature of the boiler

If on your own, before the heating company shows up, if you see high pressure readings on the boiler gauge (30 psi or above) or if you see water spilling out of a relief valve I would SHUT OFF THE SYSTEM immediately and would get the heck out of there.

Follow-up:

The PSI was not high before the repair. It was around 12. After the repair and the flooding upstairs, it is running around 18 psi now. I did look at the system this morning.

The only problem I see is that a pressure reducing valve has a slow drip from the bottom. The valve for the intake had been turned off last night to stem the flooding and then turned back on after the flow to that radiator was capped so I don't know if that affected the valve since it is about 10 inches away from the cutoff.

Reply:

12 PSI cold is normal for a typical 2 story home.

BTW I would not want to confuse an air bound system with one that is at too low pressure.

On 2014-11-06- by (mod) -

Mary depending on brand and model a new hydronic heating system (hot water) circulating pump costs between about $140. and $350. U.S. plus labor - the labor can vary depending on how much trouble it is to get to the equipment, and on details such as whether or not service valves are already installed on either side of the circulator since if there are none the technician will probably have to drain and refill the heating sytstem - adding time and cost.

On 2014-11-05 by Mary

How much should it cost to replace a circulator pump in a single family rowhome? I have a 9 yr old Bryant boiler. Not sure of the make or BTU. Thanks

On 2014-10-27 by Steve M

Have a new Crown Bimini 90,000 BTU heater installed. cut supply lines on first floor to separate upstairs and downstairs to two zones. Both have a common return though. When i turn either zone on, the supply line of the zone not on stays cold but all the radiators get hot. The zone that is not on takes longer to get hot but still does eventually.

Thinking there still may be some air in the lines but cant think of anything else that would be causing this.

FYI..boiler was ran with a boiler loop. Both zone supply lines have a circulator attached with a common 3rd circulator on the return near the boiler.

Thanks in advance

On 2014-10-23 by Teresa

A WATTS Model 500800 circulation pump delivered hot water within about 5 seconds to the house main shower (vs. 1 minute before its installation)and to other faucets throughout the house.

BUT when house was recently retrofitted for entire replacement of 75 year-old plumping pipes, the shower water runs and runs cold before getting even somewhat warm.

However, other faucets in the house are delivering hot water even better than before. The plumber is puzzled since he did not touch the plumbing for the shower (he did some adjustments with shower handle). It surely cannot be coincidental that non-delivery of hot shower water coincides with pipe replacement and installation of a new water heater.

Any ideas what might be causing the problem? Air in a pipe? A missing hook-up somewhere?

On 2014-08-18- by (mod) -

I'd start by looking for vibration, e.g. from a circulator, transmitted via piping or buliding framing.

On 2014-08-18- by (mod) -

Re-posting

8/17/14 AUTHOR:Anonymous (no email)

COMMENT:We had a tankless water heater put in a few years ago and everything was fine. A few months ago we redid a downstairs bathroom and had a circulator put in at the same time. Ever since then whenever the downstairs bathroom shower is being used there is a drone/humming noise upstais. Any ideas? Thanks

On 2011-10-21 by construction

good tutorial

Question: circulator pump cost

See CIRCULATOR PUMP REPAIR FAQs

Question: circulator mounting position vs system pressure

See CIRCULATOR PUMP REPAIR FAQs

How to Hook Up Multiple Circulators or Zones

We moved this discussion to a new article: please see MULTIPLE HEATING ZONE CONTROL

Question: circulator pump won't start

We moved this discussion to a new article: please see CIRCULATOR WONT RUN

Question: circulator pump runs intermittently

We moved this discussion to a new article: please see CIRCULATOR PUMP RUNS INTERMITTENTLY

Weak Heat Questions

We have moved this discussion to a new article: please see WEAK HEAT, WEAK CIRCULATOR, TOO COOL

Question: Circulator Pump Noises, heating system noises

We have moved this discussion to a new article: please see CIRCULATOR NOISES.

Also see HEATING SYSTEM NOISE DIAGNOSIS for a more broad range of heating noise diagnosis & repair procedures.

Question: circulator pump runs even when we are not asking for heat

See CIRCULATOR PUMP REPAIR FAQs

 


...

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

Or see CIRCULATOR PUMP REPAIR FAQs - questions & answers posted originally on this page - for diagnostic questions & answers about heating circulator pumps & circulator relays

Or see these

Recommended Articles

Suggested citation for this web page

CIRCULATOR PUMPS & RELAYS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING BOILERS

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