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Intermittent on-off heating zone operation:
Heating zone circulator pump seems to run just intermittently - it starts and stops. What's wrong, how do I fix it? We start addressing this question by asking whether or not anything is wrong in the first place.
When should the heating zone circulator be running? Then if it seems to be acting oddly, why & how do we fix it?
This article series describes how to diagnose & fix circulator pump problems on hot water or hydronic heating systems.
My furnace's circulator pump has been running in short bursts only lately, as opposed to full length cycles.
It's a gas-fired hydronic system, a high efficient one w/ a Peerless Pinacle furnace.
never experienced this before.Do you have any ideas? - mark4man 12/5/2012
(Dec 29, 2011) Richard VanMetter said:
When my thermostat calls for heat the gas comes on and the internal temperature of the furnace increases (approaching 250 degrees) but the circulator pump only runs intermittently (5 seconds on 30 seconds or more off). Shouldn't it run constantly once the internal temperature of the furnace is adequate?
(Nov 11, 2012) Anonymous said:
Hi i have an open fire with back boiler the pump is beside the back boiler and the thermostat is on
the boiler. my problem is the pump only comes on for about 30 seconds and thats it and it does nothing for the rads the pipe that the stat is on goes cold so i reckon the stat is on the wrong pipe,
please help. cheers
My circulator pump turns on then shuts off in 3-4 sec. could this be a switch?
First I would check all of the electrical connections involved since a loose connector or a corroded connector such as a spade connector on a heater control can cause intermittent operation.
... the furnace draft fan began to pulse several times upon starting. After making sure the control module showed a steady green, ... I wiggled all the spade connectors to be sure there was good contact between the copper and aluminum. ... there only needs to be a little corrosion to cause problems. That seems to have done the trick. - M.F. 12/24/2014
Next I'd check for a bad circulator control relay or possibly a thermostat wire that is intermittently shorting together. Occasionally a bad thermostat can also cause intermittent on-off calls for heat that can lead to odd circulator behavior.
A second set of possibilities might be a circulator pump that is binding or failing.
A short on-off circulator cycle such as you describe sounds to me like a wiring (damaged wire), thermostat, or circulator relay problem.
Phil, I wonder if there is a bad relay in the circulator control, or an intermittent short of the thermostat wires. Try disconnecting the thermostat entirely to rule out that source. Then connect the red and white heat wires (or equivalent if yours are different) that calls for heat. Connected = heat on. Disconnected = heat off.
Watch out: other readers note: other reasons that a heating zone circulator may not run continuously include
Normal operation: in some areas circulator pumps are wired to run continuously if the boiler has electrical power but in others the circulator only runs in response to a call for heat. In the latter case the boiler temperature turns the burner on and off.
Shorting thermostat wires: a room thermostat whose wires are shorted or intermittently shorting together may turn the circulator on and off
Poor thermostat settings: on some systems an improperly set heat anticipator may cause the circulator to stutter on and off; this problem may also show up as "contact bounce" in the thermostat
Damaged circulator pump relay: in the primary control or in additional circulator pump control relays a failing switching relay can casuse funny circulator pump on-off operation.
Tankless coil snafu: if your heating boiler does not make use of a tankless coil to produce domestic hot water but the aquastat was installed with its factory settings that control may make the heating boiler run for no apparent reason - though usually only briefly. Some may confuse boiler-burner-on with circulator-on operation. If the thermostat is not calling for heat the circulator won't run (unless it's wired for "always on" operation).
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"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.
Bell & Gossett Air Separators and other heating system components, 8200 N. Austin Ave., Morton Grove IL 60053, USA - Tel 847 966-3700 Fax 847 965-8379 . Air separators are discussed by B&G at http://www.bellgossett.com/homeowners/BG-airseparator.asp
Taco air scoops and other heating system components & controls: Taco Inc., 1160 Cranston Street, Cranston, RI 02920 / (401) 942-8000 / Fax (401) 942-2360 Taco (Canada) Ltd., 6180 Ordan Drive, Mississauga, Ontario L5T 2B3 / (905) 564-9422 / Fax (905) 564-9436 www.taco-hvac.com
Taco also has some helpful FAQs that are useful in diagnosing circulator problems - see http://www.taco-hvac.com/en/faq.html#
Sparco air purgers, air scoops, and other heating system components & controls:
"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
Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
Installation Guide for Residential Hydronic Heating Systems
Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
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