Circulating Pump Never Stops

How do we deliberately keep a heating circulator pump running?

If you want your circulator pump to run continuously all that's needed is to wire it with electrical power directly, controlled by a manual on-off switch. Then the room thermostat, connected to the heating boiler aquastat will simply turn the heating boiler on and off in response to a call for heat.

If your heating system uses zone valves, then you'll want to either jumper its control thermostat wires together OR if the valve is a model like the one shown here, latch the valve into the continuous on position with its operating lever.

As we explain at ZONE VALVES, HEATING, in our photo above, that notch at the left end of the zone valve control lever will "lock" the valve in the open position.

In normal, not-locked-open operation, the lever will move from left to right in the horizontal slot as the zone valve motor opens (lever to left) or closes (lever to right) the valve.

Instruction manuals for the Honeywell zone valve shown above and that explain its wiring and the use of the "always on" position of that latch are cataloged at

HONEYWELL /RESIDEO HVAC CONTROLS & MANUALS

And you can see a catalog of major zone valves at

HONEYWELL WHITE RODGERS & JOHNSON CONTROLS ZONE_VALVES_PARTS [PDF] Honeywell, White Rodgers, & Johnson Controls Zone Valves and Parts

How do we fix a circulator pump that won't stop when it should?

What to do if circulator pump won't stop: the circulator pump stays on all the time when it shouldn't

Here are examples of a question asked by many of our readers:

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. (Mary Oct 23, 2011)

Our heat 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. (Greg June 5, 2012)

5 Reasons a heating zone circulator never stops running

1. The thermostat is not satisfied
   
   building heat loss rate is greater than the delivery of heat to the area
2. The thermostat wires are shorted together
   
   anywhere between thermostat and circulator relay or zone valve, so the call for heat remains "on"
3. The circulator relay is damaged -
   
   or the circulator relay control board is damaged
4. The heating zone is air-bound
   
   so heat doesn't reach the thermostat for that zone: the thermostat calls for heat and is never satisfied and the circulator runs continuously
5. The circulator is not actually running, but heat is cycling through heating pipes
   
   by convection even when the thermostat is not calling for heat because of a defective check valve or a zone valve latched "open"
6. The circulator was deliberately-wired or switched to run continuously,
   
   as is the custom in some heating zones such as much of Canada.
   
   This is done to reduce the risk of frozen heating pipes and to keep heat distribution more-even in the building.
   
   In these systems the circulator runs all during the heating season and the thermostat simply turns the heating boiler on or off.

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

Why does heat come out of zones where thermostats are not calling for heat? (Mar 2, 2014) Jared

Reply:

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.

• A flow control valve, a key heating boiler check valve that is intended to prevent circulating hot water by convection may have been left manually open or may be stuck.
  
  See CHECK VALVES, HEATING SYSTEM for a discussion of check valves or flow-control valves on heating boilers.
• A zone valve may be in the manually open position or may be stuck or jammed "open".
  
  See ZONE VALVES, HEATING for an explanation of how zone valves work and how they are diagnosed & repaired


• The heating system may have been installed without a check valve or zone valve.

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.

DO I need to Turn off the Circulator when I Turn off our Heating Boiler?

When the day's are warm and I turn off the heat do I shut the circulator pump off also? - Chris 4/23/2014

Answer by Moderator:

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.

Follow-up from Chris: circulator runs even though heat is off at the thermostat

Tthe 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.

Reply: in some installations it's normal for the circulator to be "always on"

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

at DIAGNOSE & FIX HEATING PROBLEMS-BOILER

Reader follow-up: My circulator should not be always-on

Dan, I live in Hudsonville,Michigan.

Reply: Check for a stuck relay or aquastat failure & turn off the circulator power

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: Heating system is a Burnham Holiday gas boiler with one circulator and 5 zones

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.

Reply: Shorted thermostat wires or a stuck zone control can also cause the circulator to run continuously

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: why does my furnace run if I'm not callling for heat?

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.

Reply: Here's a summary of how to diagnose a "heat stuck on" problem

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

1. Rule out a thermostat problem

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.

Detailed step by step diagnosis and repair you need are

at HEAT WON'T TURN OFF

2. Rule out a Circulator Stuck "on"

How to see if a "quiet" heat zone circulator is running: check for convection circulation

Watch out: one can also be fooled, especially on hot water heating systems that use very quiet circulators such as some Taco brand circulator pumps.

Turn off electrical power to the zone circulator(s) and see if the heat stops being delivered. (It should).

3. Rule out a Failed Check Valve

The circulator could be "off" (Turn off power to the circulator to test this) but hot water could be circulating by convection, thus also causing the boiler to run (under control of its aquastat) as cooler water returns to the boiler by convection, dropping the temperature in the boiler itself until the temperature falls to the CUT IN or CUT ON temperature on the aquastat.

It's easy to check this. Turn off power to the circulator pump (but not the boiler).

If baseboards or radiators still are getting hot AND the thermostat is NOT calling for heat (or has been disconnected entirely) then

see CHECK VALVES, HEATING SYSTEM to rule out a boiler check valve that is stuck open, allowing hot water to circulate out of the boiler even when there is no call for heat.

Circulator Pump & Zone Valve Guides, Sources, Help

• CIRCULATOR PUMP MANUALS
• "Instruction Manual, Bell & Gossett Series LR Circulators" P86101D, Mayu 2012, Xylem Inc. 8200 N. Austin Avenue Morton Grove, Illinois 60053 Phone: (847) 966-3700 Fax: (847) 965-8379 www.xyleminc.com/brands/bellgossett
• "Installation and Operation Instructions, Raytherm Residential Boilers," courtesy of Raypak®, and technical advisor Wayne Hoffman, personal communication 5/11/2009.
  
  Mr. Hoffman is a technical advisor with more than 30 years experience in the heating field. Raypak is a Rheem company that provides hydronic heating boilers for residential, pool, and commercial use. Raypak can be contacted at 866-583-0664 for technical support or for assistance in selecting the proper heating equipment for a specific application.
  
  Rheem Corporation is a manufacturer of water heaters and heating equipment including Ruud heating and cooling products.
• "Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
• ZONE VALVE MANUALS & WIRING INDEX