Heating zone circulator pump bypass: how to circulate hot water in a hydronic heating system if the circulator or zone valve is not operable: bypassing the heating circulator pump or latching the zone valve open can get heat into the building even if the circulator pump itself is not working - maybe.

Our page top photo shows that a heating circulator pump motor has been removed completely while waiting for replacement. How can we get heat to flow in this building?

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

Bypass the Circulator: Question: OK to run the boiler if the circulator is not working right?

(Feb 8, 2012) Kelly said:

Can you continue to run the boiler if the circulating pump is not working properly?

The house is heating but I'm concerned about how safe this is.

The pump tries to turn on but is not and i believe it may be the coupler and will have someone out to fix it but in the meantime;

i just don't want to cause any more damage by keeping the heat on.. it's only 25 deg's today so i'm hoping it's not dangerous.
Thank you
Kelly

Reply:

In general (which means we don't know a thing about your heating system so this may be wrong for you), heating boilers are controlled by one or more temperature-sensing devices - aquastats - as well as other safety controls.

If a circulator pump is not working but the boiler is heating up, the boiler should not get hotter than the upper safety limit set by its HI LIMIT control.

Hot water will still circulate in some heating systems that use circulator pumps or even zone valves, even if the circulator pump is not working. Hot water will rise out of the boiler by convection and cooler water will return to the boiler's return side by the same process

In some heating systems one can over-ride a check valve at the boiler by manually turning a lever, and similarly one can manually open some heating zone valves.

In my photo at above left, push the metal lever all the way to the left then down to latch it in the "OPEN" Position.

See ZONE VALVES, HEATING for more details about diagnosing & fixing or replacing a bad zone valve.

The heating boiler flow control valves (photo at left) designed to prevent hot water circulating by convection when the circulator is not operating can also be manually placed in an OPEN Position.

See CHECK VALVES, HEATING SYSTEM for details.

The result is that heat will be delivered to the building by convection - more slowly than if the circulator were running - but still effectively.

In fact more than once I found this situation in homes that had hot water heat but no working circulator. The home would heat to a satisfactory temperature, but more slowly than occupants might have preferred.

This is also a stop-gap or backup method of keeping a building heated while waiting to replace or repair the circulator or circulator relay.

Watch out: in many but not all hot water heating systems that use a circulator pump, flow-control or flow-check valves and zone valves, you can get hot water to circulate by natural convection using the steps above. The thermostat calls for heat and provided that the boiler temperature is below the CUT IN setting on the boiler primaruy control or aquastat the boiler will cut-on, heating its water. Heated water will then rise in the heating distribution piping above the boiler and into the building.

• Heat delivered by these methods will arrive more slowly than if a working circulator pump were in operation
• It may be necessary to manually open the flow-control valve or check valve (shown above) in for hot water to flow.
• If a zone valve lacks a manual open feature OR if the zone valve head has jammed and won't operate then a heating system with zone valves won't circulate heat through that zone.

...

---

---

ADVERTISEMENT

---

---

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2018-10-26 - by (mod) -

Sure, Robert,

Each individual circulator pump in a hydronic heating system will be controlled by an individual relay and thermostat for that heating Zone that the circulator serves.

You should be able to Simply turn the zone or room thermostat temperature setting all the way down in that zone associated with the circulator that you want to turn off.

Thanks for asking.

On 2018-10-26 by Robert

Question - I have 4 heat circulator pumps. I want to turn one off because it interferes with the radiant heat system. Is it possible to turn off a honeywell circulator pump?

On 2018-01-07 - by (mod) -

Frank

I'm confused by this situation; if you don't have heat upstairs and you are closing a valve in the zone piping that alone would explain the trouble, right?

You can Use the on-page search box at the top or bottom of this page to look for TEST FOR CIRCULATOR PUMP OPERATION to find our article on how to figure out if the circulator is running or not.

On 2018-01-03 by Frank

i have a peerless model # MMR-85-WC boiler. I have heat at my downstairs radiators, however i dont think circulator pump is operating becaused i dont have heat to upstairs radiators. Can the boiler supply heat to radiators even though i dont hear circulator pump. i normally dont have gate valve open for upstairs heat, gets too hot at night.

On 2016-12-19 - by (mod) -

Todd,

If your system is a heat pump, and if the air conditioning future was turned off previously, then I suspect that the heat pump feature is also not going to run. This means that your home will be using backup heat.

On 2016-12-19 by Todd

I have a heat pump at my apt complex. The outside fan doesn't turn on when the heat turns on. I do know maintenance by passed my ac this past summer for some reason. is my system running properly when the outside unit doesn't turn on?

On 2016-06-06 - by (mod) -

Sal if you search InspectApedia for BOILER EXPANSION TANKS or HOW TO FIND THE EXPANSION TANK you'll see photos of ceilign-mounted tanks that may be what you've got. Follow the pipes.

Don't remove and replace anything before it's correctly identified. I've done that and I was sorry later.

On 2016-06-06 by sal

just purchase an old home that has hydronic heat I notice a large steel drum at ceiling level I assume its for an air separater I like to replace this with a new air separated is this OK ? does the steel drum have a bladder in it ?

On 2015-10-16 - by (mod) -

Jim,

If the furnace has electrical power but is not running simply leaving it turned on and having the thermostat call for heat will turn on the circulator pump; that should be all you need to do.

On 2015-10-16 by Jim

If my furnace stops working is there a way to put power to the circulator pump so that my pipes don't freeze. I would open a zone valve and do what?

...

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

• COLD HEATING RADIATOR REPAIR (hot water / hydronic heat) - If you are not getting any heat at all out of a cold baseboard or radiator
• CIRCULATOR PUMPS & RELAYS - home
• CIRCULATOR PUMP BASICS
• WHAT GOES WRONG WITH HEATING CIRCULATORS?


• CIRCULATOR DIAGNOSTICS
• CIRCULATOR PUMPS & RELAYS - home
• CIRCULATOR PUMP BASICS
• WHAT GOES WRONG WITH HEATING CIRCULATORS?


• CIRCULATOR DIAGNOSTICS
• BYPASS a BAD CIRCULATOR
• CIRCULATOR COSTS
• CIRCULATOR NOISES


• CIRCULATOR OPERATION CHECKS
• CIRCULATOR OPERATION CHECK FAQs
• SINGLE ZONE SINGLE CIRCULATOR TESTS
• MULTIPLE ZONE SINGLE CIRCULATOR TESTS
• MULTIPLE ZONE MULTIPLE CIRCULATOR TESTS
• INDIVIDUAL HEAT ZONE CIRCULATOR TESTS


• 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 PUMP RELAY FAQs
• CIRCULATOR PUMP WON'T START
• CIRCULATOR PUMP WON'T START FAQs
• CIRCULATOR PUMP WON'T STOP RUNNING
• CIRCULATOR PUMP RUNS INTERMITTENTLY
• CIRCULATOR PUMP SPEED SELECTION & ADJUSTMENT
• CIRCULATORS VARIABLE SPEED
• MULTIPLE CIRCULATORS HOW TO HOOK UP
• MULTIPLE HEATING ZONE CONTROL
• RELAY CONTROL SWITCHES
• RELAY CONTROL SWITCH FAQs
• WEAK HEAT, WEAK CIRCULATOR, TOO COOL
• CIRCULATOR PUMP REPAIR FAQs
• CIRCULATOR PUMP REPAIR FAQs-2
• CIRCULATOR PUMPS vs ZONE VALVES
• BYPASS a BAD CIRCULATOR
• CIRCULATOR COSTS
• CIRCULATOR NOISES


• CIRCULATOR OPERATION CHECKS
• SINGLE ZONE SINGLE CIRCULATOR TESTS
• MULTIPLE ZONE SINGLE CIRCULATOR TESTS
• MULTIPLE ZONE MULTIPLE CIRCULATOR TESTS
• INDIVIDUAL HEAT ZONE CIRCULATOR TESTS


• 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 PUMP WON'T START
• CIRCULATOR PUMP WON'T STOP RUNNING
• CIRCULATOR PUMP RUNS INTERMITTENTLY
• CIRCULATOR PUMP SPEED SELECTION & ADJUSTMENT
• CIRCULATORS VARIABLE SPEED
• MULTIPLE CIRCULATORS HOW TO HOOK UP
• MULTIPLE HEATING ZONE CONTROL
• RELAY CONTROL SWITCHES
• RELAY CONTROL SWITCH FAQs
• WEAK HEAT, WEAK CIRCULATOR, TOO COOL
• CIRCULATOR PUMPS vs ZONE VALVES

Suggested citation for this web page

BYPASS a BAD CIRCULATOR 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

Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia

Ask a Question or Search InspectApedia

Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Note: appearance of your Comment below may be delayed: if your comment contains an image, photograph, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Apologies for the delay.

Only one image can be added per comment but you can post as many comments, and therefore images, as you like.
You will not receive a notification when a response to your question has been posted.
Please bookmark this page to make it easy for you to check back for our response.
Our Comment Box is provided by Countable Web Productions countable.ca

Citations & References

In addition to any citations in the article above, a full list is available on request.

---

ADVERTISEMENT

---