Hot water heating circulator pump quick and easy diagnotic test FAQs.

This article series gives simple procedures for determining whether the circulator pump is working on a heating system.

How to tell if the circulator pump is working - some circulators are quiet - which pipes to feel

These questions & answers about making simple checks to see if a hot water heating zone circulator is working right were posted originally

at CIRCULATOR OPERATION CHECKS - be sure to see the diagnostic steps given there.

On 2018-02-06 by (mod) - circulator pump stays on no matter what

WS

See the repair procedures

at CIRCULATOR PUMP WON'T STOP RUNNING

and let me know what questions remain

On 2018-02-04 by W.Sharpe

Circulator Pump Will Not Shut Off

Three Taco zone valves on one Taco circulator pump. All getting proper voltage and confirmed working. Boiler hi-lo set& working properly.

Regardless of zone demand for heat or satisfied & regardless of boiler temp, and confirmed 110V across C1 & C2 terminals, C1 ( Honeywell L7224) indicator & pump stay on!

This is a new behavior, and was not the case before.

Even when I power down the system, wait 30 seconds or even 2hrs, when reenergized, 10 seconds of silence, C1 indicator light goes on, followed by a relay click, and circulator turns on. This is with no TT demand and BT above limit.

Absolutely frustrating as to why the Aquastat is now turning on the relay/circulator for no need or reason.

The MAJOR CONCERN is, the pump is on the return side, in-between closed zone valves and boiler. A total distance of <2'. not much room for relief to the impeller, sucking away like someone trying to suck a just served wendy's shake through a straw! the motor is very hot.

then i've seen on a couple of discussion sites, "no harm will come to the circulator". sounds like b.s. from a taco sales rep to me.

question is, what happened? why is the circulator suddenly running non-stop? is there a fix? btw, it is rather cold, 15 - 20 outside, & no, this doesn't have an outside sensor, and we've had colder days.

for now i'm running heat, and when up to temp, manually turning off boiler power at top of stairs, sleeping in recliner for 2hrs, waking up to turn on the heat for another warming. lather, rinse and repeat.

your valued advise?

On 2018-01-14 by (mod) - no heat after burst pipe

Gilbert,

I don't have enough information to make a useful guess: I don't know if this is a hot water or a steam boiler, nor what ball you are asking about.

If your boiler has an automatic water feeder (such as used on steam boilers) or a pressure/reducer/water-feed valve (used on hot water heating boilers) that valve could be debris-clogged or stuck and need repair or replacement.

On 2018-01-14 by Gilbert

I had a pipe burst and my water doesn't go into the boiler it looks like it's not opening that ball to allow water to go in

On 2018-01-01 by (mod) - no heat after changing circulator pump

JB

Check the simple circulator diagnostics at CIRCULATOR OPERATION CHECKS

Then

see CIRCULATOR PUMPS & RELAYS

If the circulator is running the system may be air-bound

see AIR-BOUND HEATING SYSTEMS - diagnostics

On 2018-01-01 by JB

Just bought an apartment with radiant heat - there are two thermostats for the bedroom and main living room.

When we moved in, the heat from the living room wasn't working. The pump was apparently toast. It was changed out and the heat started working fine.

About 6 weeks later the heat isn't working again. No problems with the thermostat in the other room. Any ideas?

On 2017-12-28 by (mod) - new circulator pump won't turn on

Eric,

When the circulator won't run I'd start with the procedures

at CIRCULATOR PUMP WON'T START

On 2017-12-28 by Eric B

My Utica boiler was hot, but the Grundfos pump wasn't coming on to circulate the water.

I changed the Grundfos pump, but it still doesn't come on. What is my procedure to check power to the pump, and to check the control/commands to the pump to come on?

On 2017-12-16 by (mod) - heating zone no longer works

Brad

Thinking in print in hopes this will help you diagnose the problem:

When something has worked OK for a time then is failing the most-useful thing to ask is "What has changed?"

- water pressure

- connections

- controls

- pump motor

- someone closed a valve

- air has accumulated in the system

etc.

When a zone works but only intermittently I usually suspect a loose wire, bad connection, or a failing circulator relay.

But when the circulator is running, that tells me that the zone valve opened (it's the end switch on the zone valve that turns on the circulator; that switch doesn't close until the zone valve has opened) and that the circulator motor operates.

I might suspect a bad impeller or damaged internal pump parts in the circulator but you tell me your Taco zone circulator is brand new, so that seems unlikely.

When you say the circulator is running but not circulating I assume you're determining that by feeling that the inlet pipe to the circulator is hot, observing that the motor is spinning (or humming), and by feeling that downstream on the circulator outlet side the piping or baseboards remain cold.

So we're left thinking of other reasons that hot water wouldn't circulate:

- the incoming water pressure is too low. Circulator pumps have little lift capacity and depend on the heating system's water pressure to give enough lift to get water up to the highest point in the circulating loop. That's a reason for the 12 psi (when boiler is cold) lower limit on boiler pressure in a residential hydronic heating system.

At CIRCULATOR PUMPS & RELAYS we describe the problem when "Circulator pump is not capable of pumping against the head pressure of water in the heating system:" and discuss solutions (boosting water pressure or adding a 2nd circulator) - but 14 ft. lift is not that much so I suspect the next issue is more-likely.

Still, if you want to check this, Typically the cold starting pressure in a heating system is 12 psi, provided by the Water Feeder Valve on the boiler.
On tall buildings higher pressures are needed - we provide a chart of pressure reducer/water feeder valve settings

at WATER FEEDER VALVES, HYDRONIC BOILER - in this article we note that 12 psi (cold) water pressure in the hydronic heating system should be able to lift water a bit under 28 feet.

If your lift requirement were more than that, the pressure could be the problem. But your lift is just 14 feet!

More Likely Explanation:

- The zone piping or baseboard or radiator is air-bound (a circulator can't push water through a zone if part of its piping, baseboards, or radiators have a bolus of air)

- see AIR-BOUND HEATING SYSTEMSfor the diagnosis and cure of this problem

Less likely:

- The zone piping is blocked by some other defect such as a manual valve that's shut or debris-blocked, or perhaps a check valve on the zone piping that is sticking closed

Let us know what you find as that will help other readers too.

On 2017-12-16 by Brad

Heating system working for years. " I'm purplexed"
Zone 3 of 5 zones only works part of the time.

1. Bled zone (removed air)

2. Replaced taco zone pump

3. bled system

4. Pump energised and working

5. Hot zone and working but only for a day.

6. Checked stat. Set at 10 degrees above normal at 85

Stat indicates power to zone which I confirmed at zone pump

7. Pump running not circulating.

Note: feeds two stories up approximately 14 feet vertical. Zone 4 at same level working fine.

On 2017-08-19 by (mod) - if you're circulating water full time - as I infer from your note - and the water's not hot,

Michael,

It isn't likely that you've wasted your money - but if you're circulating water full time - as I infer from your note - and the water's not hot, the problem will be

- uninsulated hot water lines losing a lot of heat

- water heater not set to proper temperature

- a water heater control that's not working

- a burned-out electric heater element

On 2017-08-19 by Michael

Had a Grundfos circulation and new hot water tank installed at same time.

Prior to this, had to Run faucet for hot water at Kitchen long time, would say about 2 to 3 gallons before the water was even getting close to being warn, or hot.

Now that this pump is installed, now have to run cold faucet for long time to get cold water, its very warm water coming out of the cold faucet, I would say 2 to 3 gallons again before its close to cold.
I'm beginning to think I've wasted money, that truthfully didn't chance anything except from hot to cold.

On 2016-12-06 by Rob

Worcester Heatslave 20/25 oil combi boiler. 6 rads downstairs and 6 rads upstairs. Some downstairs rads suddenly stopped working.

No changes had been made to the system. Upstairs ones were hot. Let system cool down for 5 hours, then checked the pressure. It's set to just over 1 bar. Bled ALL radiators and pump, no air found at all.

Pump body is too hot to touch when boiler is on. I removed pump bleed screw and could turn the shaft inside it easily. It was suggested pump was faulty, so the Grundfos 15-60 pump head was replaced with a Grundfos PS2. No difference found. Pump body still gets hot. I have fully opened all TRVs upstairs and shut the lockshield valves to them.

One rad upstairs is always open and has no TRV. Then started the boiler and opened them about 1/2 turn until each rad got hot. Checked downstairs rads but they were still cold, even though TRVs opened and lockshield valves opened fully.

Warm/Hot water can be felt in the pipe up to the TRV but not in the rad. Shut all TRVs upstairs, and downstairs rads then got hot. Turned 1 rad on at a time upstairs and 4 of them got hot but after turning on the 5th upstairs, the downstairs ones lost heat and cooled down. The boiler makes a low 'rattling' noise when the burner isn't firing, as though air is going through.

I have bled the system several times and kept pressure constant but at no time is air emitted from the rads or pump. I've bled 3 other valves that I found on top of the boiler with no air being found.

The pump speed has been varied between 1 and 3 but to no avail, the indicator light on the pump changes to the different pump settings, so there is some power getting to the pump. How do I tell if the pump is actually moving water around, instead of the hot water just naturally rising through the system. You can't hear the pump when the boilerr is firing. What item in the boiler passes the electrical signal to the pump for it to start.

Could that be faulty? Or is it just the system out of balance, even though the original problem just started without any changes to the system?

On 2016-10-23 by (mod) - consumer fuses confuses

Sorry, Nick, I don't know what "consumer fuses" you mean.

On 2016-10-23 by Nick

When the pump of a boiler does not work or circulate, does it affect any of the consumer fuses

Question: circulator pump not heating first floor but higher floors get heat

(Feb 16, 2015) Mirso Dragovic said:
I have a 2-1/2 story building with 1 hot water baseboard system feeding both the first floor and second floor apartments.

1 circulator pump with no zoning valves. The problem I'm having is the first floor is about 10 to 15 degrees warmer than the second floor.

I have the high limit temp set to 200 degrees and the water pressure set to 25lbs. I'm wondering if the circulator pump is working correctly, or should I be looking at something different. I have bled the radiators on the second floor and are getting hot.

Thank You in advance

Not sure if I should have left my email: mirsodragovic@gmail.com

Reply:

Miso,

Since in a 2 story 1 zone home warm air wants to rise upstairs by convection usually we have the opposite trouble, too Mapuche heat upstairs.

Often the plumbers install manually adjustable flow balancing valves on each heating piping loop to permit adjusting the flow rate of hot heating water to these different areas.

Ask your heating service tech to find and adjust these to get more heat where you want it, or to install them if needed.

Also take a look at the thermostat location, as that could be part of the problem.

...

Continue reading at CIRCULATOR OPERATION CHECKS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

If you are not getting any heat at all out of a cold baseboard or radiator, see COLD HEATING RADIATOR REPAIR (hot water / hydronic heat) .

Or see these

Hot Water (Hydronic) Heating Boiler Circulator Articles

• CIRCULATOR PUMPS & RELAYS
  • CIRCULATOR PUMP BASICS
  • WHAT GOES WRONG WITH HEATING CIRCULATORS?
  • CIRCULATOR DIAGNOSTICS
• CIRCULATOR PUMPS vs ZONE VALVES

Suggested citation for this web page

CIRCULATOR OPERATION CHECK FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING BOILERS

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