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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.
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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
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.
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.
and see THERMOSTATS, HEATING / COOLING for details.
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
Continue reading at CIRCULATOR OPERATION CHECKS or select a topic from the More Reading links shown below.
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