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Reset Switch - Heater Primary Control
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SOLAR HEATING SYSTEM DESIGNS
SOOT on OIL FIRED HEATING EQUIPMENT
STEAM HEATING SYSTEMS
THERMOSTATS, HEATING / COOLING
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WOOD, COAL STOVES & FIREPLACES
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ZONE VALVES, HEATING
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.
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Heating 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.
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.
Arguing whether multiple circulators or multiple zone valves is better is like arguing religion. Some heating contractors prefer using individual circulator pumps, one per zone, perhaps because they recall the history of unreliable zone valves which tended to clog or jam in some models by some manufacturers.
The "zone valve" gang retort that modern heating zone valves are as reliable or more reliable than [some models of] heating circulator pumps and that a zone valve costs a lot less. And adding zone control to an existing heating system may be less costly by adding a zone valve than by adding a circulator pump.
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.
Some heating systems use a single circulator to move hot water through the building's heating devices. 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.
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.
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.
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.
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.
If the boiler runs but the heating baseboard or radiators in an area do not get hot, the problem could be
If the heating boiler itself if does not turn on in a response to a call for heat see NO HEAT - BOILER.
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Frequently Asked Questions (FAQs) about hot water heating circulator pumps & relays: installation, troubleshooting, repair
Question: circulator pump runs in short bursts
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
First 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.
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