Heating System Circulator Pump Location, Mounting, Wiring

Where to Locate the Circulator Pump

We often receive the question "Where should the heating boiler circulator pump be mounted: on the supply or boiler outlet side (the hot side) or on the return or boiler inlet side (the cool side) of the heating piping loop?"

Read the instructions:

The short answer is, mount the circulator and arrange all other piping and controls according to the boiler manufacturer's installation and operating instructions and you won't go wrong.

A sample boiler installation and operation manual that is particularly clear and easy to follow is provided by Raypac® but of course you should obtain and follow the instructions from the maker of your particular boiler maker.

Download a free PDF copy of your circulator pump's IO manual

at CIRCULATOR PUMP MANUALS

Locating the Circulator Pump on the Boiler Return or "cold" or "inlet" side

On the boiler return or inlet side:

most but not all residential heating boilers and probably most commercial heating boilers mount the circulator pump on the return or inlet side of the heating boiler.

This location is a traditional one preferred by some old-school boiler installers and service people, dating from a time when a boiler came from the manufacturer without the circulator pre-installed on piping attached to the unit.

Some heating service technicians (including the web publisher) opine that the cooler heating water temperature on the return side of the boiler means that the circulator pump and its bearings may have a longer life than if installed on the hot side.

Typically heating water returning to a boiler after circulating through a building is about 20 °F. cooler than water leaving the boiler.

The heating boiler piping diagram at page top, courtesy of Raypak® shows the heating system circulator pump assembly (red in our sketch) on the return or inlet side of the heating boiler.

By piping convention the triangle (which we surrounded in red for emphasis) points down, showing the direction of water flow.

Locating the Circulator Pump on the Boiler Supply or "hot" or "outlet" side

On the boiler supply or outlet side:

as we explain just below at Air Exit Tanks, in some heating boiler installations that use an air exit tank to combine the EXPANSION TANK function

with the AIR BLEEDER VALVE or air purge valve function on a heating system, the air exit tank is mounted on the header piping on the supply side of the boiler and the installer may prefer to place the circulator pump below that tank to improve the air purge function of the system.

Air exit tanks are not common on residential heating systems, but the can occur, often accompanied also by water leaks. .

It does not matter which side of the boiler gets the circulator pump?

Ultimately, from a functional viewpoint, it does not matter one bit which side of the heating boiler has the circulator pump mounted, supply side or return side.

That is, the pump will work in either location and will move water through the heating piping loop(s).

That is because in a hydronic heating system the circulator is pushing water around a closed loop: the boiler and boiler piping are filled with water and there is (or should be) no air in the system. (If a hot water system piping or boiler contains more than a few bubbles of air the system is likely to

become AIR BOUND and heat will be lost or missing in all or part of the building.

Watch out: from a service-life viewpoint, however, traditional best practice puts the circulator on the cooler side of the boiler's heating loop where many technicians opine the lower heat gives longer equipment life. We say more about circulator pump location below.

But at least some manufacturers say it doesn't matter. Here is Taco's position on circulator pump position:

All of the "00" pumps can be used on the supply side or the return. It is preferable to put a circulator on the output of a boiler, but the expansion tank should be between the boiler and the pump section. Most of our "00" iron pumps have a max water temperature of 230ºF.

The max for the bronze is 220ºF. 160ºF is cold. No matter what the water temperature is, the motor housing will be hot. There will be no change in performance or life. - Taco FAQ

Also see these CIRCULATOR PUMP LOCATION FAQS

Circulator Pump Mount Position

Circulator Pump Mount Position - keep the shaft horizontal and observe flow direction arrows & wiring locations

Circulator pump position:

Watch out:  as we explain at our home page for this topic be sure that the circulator pump is installed as the manufacturer describes. While most circulator pumps can pump heating water in just about any position, there are some positional constraints. For example, quoting from B&G:

The Series LR Circulator can be installed to discharge up or down, horizontally, left or right, but the motor shaft must remain in the horizontal position, the arrow on the body must point in the direction of the flow, the conduit box must be positioned on the top or to the side of the motor housing. - "Instruction Manual, Bell & Gossett Series LR Circulators" [see References]

This article series discusses hot water heating system circulator pumps: how to find, inspect, diagnose, and repair problems with Hot Water Heating System Circulator Pumps or circulator pump relay switches and controls.

See circulator mount position and location recommendations in the installation details at CIRCULATOR PUMPS & RELAYS - home

Also see these CIRCULATOR PUMP MOUNT POSITION FAQs

Heating Circulator Pump Wiring

Tip: see the wiring diagrams in the IO manual for your circulator pump; if you don't have the manual, download a free PDF copy

at CIRCULATOR PUMP MANUALS.

See also CIRCULATOR PUMP RELAYS & OTHER CONTROLS  for wiring diagrams for the circulator relay used to turn the pump on or off.

Does the TACO circulator for baseboard heat require an electrical ground ?

Our reader asked:

Does the TACO baseboard heater system require a 'ground' & where would that be found?

Can the system generate static electricity if the 'ground' is not functioning normally. I'm concerned about excess static electricity & 'hot' de-humidified heat which is very uncomfortably drying to skin.

This system is connected to another heating system (I think) controlled by a wall thermostat.

Temperatures set do not seem to synchronize with thermostat set temperature or temperature output at Honey Well temperature which does not synchronize with actual room temperature, or outside temperature as stimulus for running baseboard at a high temperature.

Do you think there is a major problem? The TACO begins to heat at the 'activator' at very high outer thermostat settings.

(Big white outer ring thermostat around a small HoneyWell supposed room temperature thermostat which is almost always 69-70 degrees.) On 2022-01-11 by Mary

by Inspectapedia Com Moderator - Electrical grounding requirements for heating zone circulators

@Mary,

Apologies but I'm confused by your question.

Hot water heating circualtor pumps like those made by Taco do not generate static electricity nor would electrical grounding be included in a circulator pump wiring just to address static electricity.

Watch out: however, as proper electrical grounding of the electrical circuit powering the Taco circulator pump is absolutely required. Here's a quote from an example Taco zone circulator pump that I'll cite below:

[Electrical] Grounding connection is essential for safety and should be connected first. System piping should be grounded separately.

Typically a green ground wire is connected to a green grounding terminal screw in the circulator pump and in the electrical box where it's also connected to the electrical circuit grounding conductor.

The basics of electrical grounding might help you understand what's happening.

See ELECTRICAL GROUND DEFINITIONS 

The room thermostat is essentially a call for heat that turns on a circulator pump in what I take to be your case.

Other temperature controls such as on the boiler or at a compensator for outdoor temp control when the boiler runs.

Instructions for your TACO circulator that powers your hot water baseboard heating system can be found at

TACO DIAGRAMS, MANUALS, PARTS, CONTACT

Here is a typical manual (we don't know which Taco circulator you have installed).

• TACO 1900E ECM HIGH EFFICIENCY CIRCULATOR MANUAL [PDF] including the Taco 1915E circulator pump

See also these

CIRCULATOR PUMP WIRING FAQs

Other heating system controls for hot water circulator pumps - three ways to control hot water heat circulation

• Individual High Limit and Low Limit relay switches on heating boilers: these may be provided on older heating boilers. See LIMIT CONTROL, SINGLE
• Zone valves on heating boilers - heating water piping in a building, particularly where hot water baseboard heat is used, may be divided into separate heating zones (different floors, or different areas on a single floor) to permit more detailed control of heat distribution in a building.
  
  The control of heating water through these different heating zones may be accomplished by use of zone valves (one per heating zone or area or "loop" of heating piping) which in turn are connected to individual thermostats. When the thermostat calls for heat in a particular building area, the thermostat switch causes the zone valve to open, to permit hot water to flow through that zone.
  
  When the zone valve is fully open, an "end switch" inside the valve tells the heating system's circulator to begin operating, causing hot water to flow through the zone. Typically heating systems using zone valves will have two or more zone valves (usually but not always located close to the heating boiler) and a single circulator pump (usually located on the return end of the hot water piping close to the heating boiler).
  
  See ZONE VALVES, HEATING for details.
• Circulator relays on heating boilers - an older and by some heating service technicians, a preferred method to control the distribution of heat to individual building areas uses a individual circulator pump to force heating water through each individual heating zone piping. This system too is usually found on hot water baseboard heating systems.
  
  Two or more circulator relay switches, one relay for each circulator pump, will be installed to turn on and off each heating water circulator if more than one heating circulator is installed. Individual low-voltage thermostats located in the living area will respond to a call for heat by switching on the circulator relay which in turns on the (120V) circulator pump.