Heating System Circulator Pumps & Circulator Relay FAQs

Index to Hot water heat circulator pump & relay diagnostic questions & answers

Hot water heating zone circulator piping FAQs

Hot Water Heat Zone Sub-Loop Options

Options for splitting up an existing hot water or hydronic heating zone into individually-controlled sub-zones.

Above: Illustration of a direct return hot water heating system from Bell & Gossett, adapted with minor edits by InspectApedia to show a heating zone sub-loop. In this instance B&G is using a secondary zone circulator pump rather than a zone valve to control the flow of hot heating water through secondary zone #3.

- Source: Bell & Gossett, HYDRONIC SYSTEM TYPES [PDF] (at Xylem website) Technical Manual TEH-471A, local copy saved as Hydronic-System-Types-BnG.pdf

Can I add sub-loops and more zone valves to a hot water heating zone?

I have a boiler with 4 Bell and Gosset series 100 Zone pumps.

I would like to take one zone pump and add two sub loops with zone valves.

Can I use a neat packged relay box like the ones Bell and Gosset or Taco provide or do i need to just wire the new thermostats to the relay for the zone in question. On 2016-12-10 by Chaz

by (mod) - You can split one heating zone into sub zones using zone valves + additional piping

Chaz

The typical solution for the case you describe is to add a zone valve at the point where you were splitting off the separate sub loop or new heating zone.

Remember that you will need additional piping tees and connections so that the hot water in your heating system can flow through each sub loop or zone.

Above, excerpting from Bell & Gossett's technical manual that I cite below, you see just one of quite a few possible piping arrangements. Where B&G is showing secondary circulator zone pumps on those "sub loops" for hydronic heating, you can typically use individual zone valves instead - at least on a smaller residential building.

On larger and commercial buildings, you might be asking too much of a single circulator pump and additional pumps may give better performance.

Each zone valve controlling a sub zone served by that one circulator is controlled by its own thermostat.

For help choosing additional thermostasts you might want to see

THERMOSTATS, HEATING / COOLING

When the thermostat for the new zone calls for heat it opens the zone valve. When the zone valve is fully opened and end switch will turn on the 30 circulator.

The two circulator brands you mention, B&G or Taco both produce zone valves that would be suitable as well as other companies such as Honeywell (now Resideo) .

See details at

MULTIPLE HEATING ZONE CONTROL - where we describe the difference between using multiple zone circulator pumps vs multiple zone valves.

ZONE VALVES, HEATING - home

You might also want review

ZONE VALVE SIZE vs GPM where we explain the effect of zone valve pipe diameter on heat delivery

Is it OK to install 2 circulator pumps on both the supply and return lines of a hydronic heating system ?

Is it reasonable to install 2 circulator pumps on both the supply and return lines of a hydronic heating system ? (Jan 28, 2016) Allen

Reply:

Allen I'm aware of no reason whatsoever to install two circulator pumps on individual zone lines.

One pump, properly sized and working should be sufficient.

Tried to drain water from zone pipes, no water came out - where did it go?

I have a strange issue. I have a 3 zone system (basement, 1st, and 2nd floor). I had heat in all zone all winter.

When trying to replace a 2nd floor baseboard heater I first shutoff the water into the boiler.

Then I isolated the 2nd floor return from the system (shutoff) and opened the drain. No water drained. There are no leaks in the system (main shows no water draw - spinning arrow still, no piping is below grade, and no water stains/leaks, or mold is present).

If Taco was stuck open where did the water go? Im lost here. Any thoughts would be appreciated. (June 19, 2016) Steve

Reply:

Good question; possibly the zone was already air-bound - see AIR-BOUND HEATING SYSTEMS to read more about that.

If a boiler lost water from a leak anywhere or by having been partly drained at a boiler drain valve, water from upper levels of piping might indeed run back into the boiler.

Or also, it can be difficult to drain water out of a closed system when you open just one valve, varying depending on where that valve is located. For example a closed zone valve will prevent water from draining past that valve.

To try to drain the second floor baseboards again,

- manually latch "OPEN" the zone valve for that zone

- open the drain on that zone, presumably below or close to the zone valve

- open an air bleeder located anywhere on the baseboards upstairs on that second floor

Steve said:
Just a followup to closeout this problem. The Taco Zone valve for the 2nd floor was a model 552-3D install dated 3/95. This zone valve had no auto/manual lever to operate and had a circular base.

I had to cut and drain the 2nd floor supply-side anyway so I could ensure no water was in the line to install a baseboard heater. When hooking up the shop vac to clear the line I did get suction from the hose on the drain side so it had to have been air-bound.

Finally, should the 571-2 vast valve body be disassembled prior to soldering? This is unclear but I believe so, especially if the cast body has any rubber in it. Thanks!

(mod) said:
Thank you for the helpful follow-up;

Typically the zone operating motor is detached, the zone valve is put into the fully-open position, and the valve body is otherwise left assembled during soldering in place. Some plumbers wrap a wet strip of cloth around the valve side of the solder job to minimize heat transfer into the valve body.

Don't push more solder into the joint than needed.

Here's an excerpt from a Taco EBV operation instruction sheet

WARNING: Operator must be removed from the valve body before soldering. Ball valve must be in the full open position before soldering. Valve shipped in the closed position.

The valve you are installing is widely used and sports a twist-off head and a manual open lever.

Older instructions say the valve can be installed without disassembling but warn about using 50:50 or 40:60 solder and a fine pointed torch flame;

Watch out: if youre using low lead or no lead high silver solder that requires a hotter temperature you should absolutely disassemble the valve.

...

After turning off water to the house the circulator won't work

My husband and I turned the main water supply off to the entire house while we repaired a shower valve.

When we turned the water back on, our circulator pump no longer works. What could have caused this? Who should we call to have it looked at? (Feb 19, 2015) Janet

Reply:

Janet I can't posit an obvious connection between a hot water heating system zone circulator pump operation and the main building water supply being shut off unless your boiler lost water and also includes a low-water-cutoff safety control and also didn't accept make-up water when water pressure to the building was restored.

Circulator Pump Wiring FAQs

Tip: See installation details at CIRCULATOR PUMP WIRING

Also see CIRCULATOR PUMP RELAYS & OTHER CONTROLS

I think I mis-wired the heating zone controls - one thermostat but 3 zones?

A friend asked me to look at his heating system. It's a hot water system that has been changed a number of times. It was originally a three zone system with three thermostats.

It was changed to a three zone , one thermostat system. This caused huge temperature variances from room to room. He wants it back to the way it used to be.

The box has three thermostats, four relays, 120V power, 120V/24V transformer, and the two wire 120v leads to the pump.

I wired 120v power to the relays, 24v thru the relays to the thermostats and from the relays to the pump with 120v.

Problem: when I tested without the pump, all worked fine. When I connected the pump, all three zone valves turned on. I'm obviously getting feedback power.

I tried two or three different wiring ideas with the same problem . I'm baffled . I either need a different wiring idea and suggestion ,or, perhaps a fool proof solid state controller. Any suggestions would be great On 2016-10-11 by Don

Repy by mod: thermostat and circulator pump wiring details

Don:

I'm unclear how we can have 3 zones and only one thermostat. If only one thermostat calls for heat, and as it can physically be only in one location in the building, when that thermostat calls for heat, by your description, all 3 circulators run or zone valves open - so really it's a one-zone heating system with 3 loops.

I don't know what sort of box has 3 thermostats. Thermostats are located in the area of the building whose heat is to be controlled as a zone and should turn on heat for that zone. I don't know how one would put them all in one box.

Watch out: for hazard of death: there are live 120V connections = shock hazards in the control. So if you're not comfy fooling with it it's far safer to call for a repair service tech.

For circulator pump electrical wiring details, it's best to start with the wiring diagrams found in the IO manual for your specific circulator pump.

You can find and download a free PDF copy of your circulator pump's IO manual

at CIRCULATOR PUMP MANUALS

No power to the circulator pump

I have no power going to the circulator pump. I have rigged a manual power supply to it for now. What would stop power to the pump? (Feb 16, 2015) Anonymous

Reply:

Causes of loss of electrical power to your circulator pump include:

• A thermostat not calling for heat,
• broken thermostat wires,
• open circulator power switch,
• a failed circuilator relay,
• power off to the boiler or circulator electrical circuit,
• bad circulator control on a primary control board.

One zone heats but the other won't

My pump will circulate water when first floor calls for heat but does not circulate when second floor calls for heat, what could the issue be? (Dec 4, 2015) Daniel

Reply:

Check for

improper thermostat settings or switch positions

a bad thermostat wire

a bad thermostat

a bad circulator relay or zone valve

See NO HEAT - BOILER for diagnostic steps.

Do circulator pumps have a reset button?

Is there a reset button on circulator pump? On 2017-11-17 by Andy

by (mod) -

Generally not, Andy.

Other electric motors on heating systems such as an oil burner DO have their own reset button.

Circulator Pump Mount Position FAQs

Tip: See CIRCULATOR PUMP MOUNT POSITION - keep it horizontal?

Circulator mounting position vs system pressure

I'm seeing pictures of products installed incorrectly with no mention that they are wrong. (Mar 2, 2012) Ken

Reply:

Thanks Ken, Please check out these articles where we address circulator pump mounting in detail. Further comments are of course quite welcome, especially if you can add citations to manufacturers or other sources for clarification of your view.

• CIRCULATOR PUMP MOUNT POSITION
• CIRCULATOR PUMP MOUNT LOCATIONS
• ELECTRIC MOTOR RUN DIRECTION

Circulator Mount Position: Should both circulates arrow be pointed up?

Should both circulates arrow be pointed up On 2017-12-31 by Tom

Reply by (mod) -

Tom,

The circulator arrows must point in the direction of intended hot water flow.

If the circulator is on the return side of the boiler the arrow should point TO the boiler.

If the circulator is on the supply side of the boiler the arrow should point TO the building's heating baseboards or radiators or convectors.

Circulator Pump Location FAQs

Tip: See details at CIRCULATOR PUMP LOCATION - where to put it or where to find it

Where is the Taco circulator relay found?

I have a one zone baseboard heating system. When I set my wall thermasat to 70 degrees the boiler goes on.

The outlet pipe gets hot, you cannot touch it, it has a temp/press. gauge on the outlet pipe on the boiler plus an other gauge set at 180 degrees.

The return pipe going into the circulating pump does not get hot until the boiler shuts off. The Temp. of the boiler is 200 degrees @ 15 psi. But I noticed the pump does not go on. When should the pump go on? It is a Taco 110-20 770.

Where is the relay located? The pump electrical supply is connected to a box on the boiler. Is the relay in that box? Oct.27,2015 John 27 Oct 2015 Anonymous

Reply:

The taco relay is in the little box atop the Taco circulator pump;

If the circulator rusn but baseboards don't get hot I suspect the system is air-bound. Search InspectApedia for "air bound heating baseboards" to read details.

Where to find the circulator pump

Where is the circulator located on a single line hot water boiler furnace? (Nov 22, 2015) Mindy said:

Reply:

It could be anywhere but usally close to the boiler on the return side of the hot water heat piping loop right at or close to the boiler.

The circulator would work anywhere in the hot water heating loop, but usually it's located close to the heating boiler. Best location is on the return side of the loop close to the boiler where the cooler water temps give longer circulator life.

Buying a Circulator Pump FAQs

Question: circulator pump cost

What is the average price of a circulator pump? (Dec 28, 2012) Mary Tilma

Reply:

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.

How to choose a circulator pump for hot water heat

How do you choose the proper circulating pump for a baseboard hot water system? (Nov 21, 2015) George

Reply:

Good question, George.
Technical selection of a circulator pump for a hydronic (hot water) heating system considers the following:

1. do we want a single speed or variable speed pump; variable speed gives finer control over heat delivery but is usually not required for a standard residential installation

2. What is the design flow in gallons per minute of the hot water heating system

3. Minimum efficiency of the pump

4. We can also specify the water operating temperature range, motor RPM choices and other details.

Cirulator pump manufacturers like B&G and Taco offer and online pump sizing table or calculator; others offer a printed or PDF file of pump size choices.

Typical residential circulator pumps range from about 0.5 hp to 1.5 hp.

What this last line (above) means to some of us is that while an HVAC engineer can, should, and will perform calculations or use a circulator sizing tool following the well-established procedures and rules of the manufacturers and industry, life is simpler for us little guys.

Talk with your plumbing or HVAC supplier about the height of your home, the number of feet of baseboard, and the heat loss rate of the building, and choose a pump from among the models in the 0.5 to 1.5 hp.

Put another way, using electrical panel sizing as an example: we can and code instructs how to calculate the required electrical service ampacity for a residential building, when we stop by the local electrical supplier we'll see that there is a range of panel (and ampacity sizes) typically with a minimum of 100A (all are 240V) and a maximum for typical residential of 200A, with choices of 125A and 150A in the middle, and a range of choices of number of circuits the panels hold. Given modest price differences I'll put in 150A or 200A. That's that.

Should I insulate the circulator pump?

I have in floor radiant heat and I have spent a bunch of effort to insulate all the hot water pipes that are exposed to conserve heat loss and make it as efficient as possible.

My question is: I notice the circulation pump is very hot, ergo probably losing heat through convection the same as un-insulated water pipes, should I wrap the pump or will that cause it to be too hot internally and possibly damage it?

I can't imagine it would hurt it but thought I should ask. On 2019-01-04 by Chris

by (mod) - no don't try insulating the heating zone circulator

Chris

I would not insulate the circulator pump for just the reason you give: it may overheat, shortening motor life.

A clue that's worth looking into is just where the circulator pump is installed.

While it can work pretty much anywhere in the piping loop, old timers like me prefer to see the circulator installed on the return side of the heat piping loop - water there is a bit cooler, which the pump then enjoys and which can give it a longer life.