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AIR CONDITIONING & HEAT PUMP SYSTEMS
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BANGING HEATING PIPES RADIATORS
BLOWER FAN OPERATION & TESTING
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BTU USAGE MONITORS
CARBON MONOXIDE - CO
CIRCULATOR PUMPS & RELAYS
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DIRECT VENTS / SIDE WALL VENTS
DRAFT REGULATORS, DAMPERS, BOOSTERS
DUCT SYSTEM & DUCT DEFECTS
ELECTRIC MOTOR DIAGNOSTIC GUIDE
FAN, AIR HANDLER BLOWER UNIT
FLOODED HEATING EQUIPMENT REPAIR
FLUE SIZE SPECIFICATIONS
GAS BURNER Flame & Noise Defects
GAS PIPING, VALVES, CONTROLS
GEOTHERMAL HEATING SYSTEMS
HEAT PUMPS, DIAGNOSIS, REPAIR
HEATING COST SAVINGS METHODS
HEATING OIL PIPING TROUBLES
HEATING OIL TANKS
HEATING SYSTEM NOISES
HEATING SYSTEM TYPES
GAS LP & NATURAL GAS SAFETY HAZARDS
MANUALS & PARTS GUIDES - HVAC
MIXING / ANTI-SCALD VALVES
MOTOR OVERLOAD RESET SWITCH
NOISE, HEATING SYSTEMS
ODORS FROM HEATING SYSTEMS
OIL FILTERS on HEATING EQUIPMENT
OIL FILL PIPE LEAKS
OIL SPILL CLEANUP / PREVENTION
PLASTIC Plexvent / Ultravent RECALL
PUFFBACKS, OIL BURNER
RELIEF VALVE LEAKS
Reset Switch - Heater Primary Control
RESET SWITCH - ELECTRIC MOTOR
Reset Switch - Stack Relays
SAFETY, HEATING INSPECTION
SAFETY RECALLS CHIMNEYS VENTS HEATERS
SOLAR HEATING SYSTEM DESIGNS
SOOT on OIL FIRED HEATING EQUIPMENT
STEAM HEATING SYSTEMS
THERMOSTATS, HEATING / COOLING
VIDEO GUIDES: Heating System Videos
WINTERIZE A BUILDING
WOOD, COAL STOVES & FIREPLACES
WOOD STOVE SAFETY
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: how are circulators used to control heating zones & how do we Diagnose & Fix Circulator Pump Troubles?
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.
See MULTIPLE HEATING ZONE CONTROL for as much argument as you can stand about multiple circulator pumps versus multiple zone valves for heating zone control.
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.
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.
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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.
Reader Question: radiator exploded after circulator pump repair
(Jan 30, 2014) Heather said:
I have a boiler for heat in my home with two circulator pumps that supply two different zones (upstairs and downstairs). My circulator pump for the first floor went bad and was replaced, fixing the problem. The boiler itself had no issues.
An hour later, a radiator upstairs (different zone supplied by the other circulator pump) exploded and a 6 inch piece of metal was cast from the radiator causing water to flood the house. This happened in a different zone connected to the other pump from the same boiler.
Could the exploded radiator in the other zone have been affected by the replacement of the circulator pump to the other zone? I cant understand how this coincidentally happened when there seemed to be no problems with the supply to the zone on the second floor where it happened. Any feedback is appreciated.
This question was originally posted at HEATING SYSTEMS
This sounds horrible - and peculiar. Forensic investigators start by disbelieving coincidences.
But it's not clear why a radiator would explode under any circumstances. Really "explode" ? We're talking about hot water heat, at normal pressures under 30 PSI.
Watch out: if your heating system pressures were abnormally high (over 30 psi) then either your system was missing a critical safety device - a Temperature/pressure relief valve at the boiler - or the valve was installed but was jammed, or subverted, or not working.
IF that is is the case this is a VERY DANGEROUS condition as an exploding boiler can cause a BLEVE explosion of tremendous force. (Search InspectAPedia for Bleve explosion to read Details).
In short, a normal hot water heating circulator pump does not have great pumping power; if there was an overpressure problem in the system it seems more likely it came from another component. Naturally everbody involved in working on your system will be scared to admit fault. Focus on a thorough inspection of the heating boiler starting with
- the location, type and condition of pressure/temperature relief valve
If on your own, before the heating company shows up, if you see high pressure readings on the boiler gauge (30 psi or above) or if you see water spilling out of a relief valve I would SHUT OFF THE SYSTEM immediately and would get the heck out of there.
The PSI was not high before the repair. It was around 12. After the repair and the flooding upstairs, it is running around 18 psi now. I did look at the system this morning. The only problem I see is that a pressure reducing valve has a slow drip from the bottom. The valve for the intake had been turned off last night to stem the flooding and then turned back on after the flow to that radiator was capped so I don't know if that affected the valve since it is about 10 inches away from the cutoff.
12 PSI cold is normal for a typical 2 story home.
BTW I would not want to confuse an air bound system with one that is at too low pressure.
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.
(Dec 28, 2012) Mary Tilma said:
What is the average price of a circulator pump?
Mary, Grundfoss & Bell & Gossett heating zone circulator pumps are typically in the range of $100. to $300. depending on the pump model.
Those heating zone circulator prices do not include the costs of additional relays, wiring, plumbing, or other installation needs. In other words we're giving you the heating circulator assembly cost, not the installed-cost. Installed costs for heating system components varies quite a bit by country and geographic area within country.
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