Q&A on How to Check Circulator Pump & Circulator Relay Operation

Circulator Pump vs No-Heat FAQs

No Heat in Some Zones after Noisy Circulator Pump Repaired

My housemates and I are renting a house and we've been having furnace troubles, in October a man came in and bled the pipes but most of the radiators still didn't work fully, with two not working at all,

Eventually the Circulator pump started to make a grinding noise so a man came in and oiled the seal, after this the noise became much worse and the man came back and replaced the entire pump, he bled the lines again and told us that they should be working better.

The radiators which had only been half working now began to work better, but two in the extension part of the house have been ice cold the entire time.

I've been watching the furnace and it seems to start the boiler every 20 minutes, once the temperature reaches 150 it starts the circulator pump which runs on average for 45 seconds before shutting off.

Is this normal and if so what could be a possible issue as my landlord has been unresponsive to the issue. for context the Thermostat is set to 21c and the outside temperature is on average -10c.

It's also a consensus that for the most part the house is not being kept at 21c despite the thermostat being set there. (Feb 12, 2016) Grant C. R.

Reply:

Grant it sounds as if the circulator pump motor or pump unit failed and was replaced. But doing that repair, involving changing out the whole circulator pump assembly, lets air into the heating pipes. That air will prevent hot water from circulating or may reduce its circulation volume - the air has not been sufficiently bled from the system. See

• AIR-BOUND HEATING SYSTEMS - home
  • AIR BOUND RADIANT HEAT
  • AIR BOUND HEAT SYSTEM REPAIR by PUMP
  • AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE

Tell me how to prime or purge the circulator pump to get the radiant heat back on

The water to my house was turned off for a sewer line repair. I'm supposed to 'prime/purge' the circulator pump before turning the radiant heat back on - don't know how. the system is open and the heat source is a tank water heater. (May 27, 2016) sid

Reply: how to bleed air from the radiant heat piping system

See these procedures to remove the air

• AIR-BOUND HEATING SYSTEMS - home
  • AIR BOUND RADIANT HEAT
  • AIR BOUND HEAT SYSTEM REPAIR by PUMP
  • AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE

When to Replace a Heating Circulator Pump FAQs

How do I fix a circulating pump that seized and burned the seals

I have an old boiler that was once oil fired, but converted to gas sometime in the past.

The circulating pump seized and burned the seals. Under this circumstance, can I even think to repair this pump, or should I replace it.

Please respond to chrisshipton@q.com (Mar 28, 2016) Chris

Reply: replace the circulator pump

Converting the fuel source on a hydronic boiler would not itself have anything to do with the circulator pump operation, though a snafu in restoring the boiler to service such as airbound heat piping, wiring errors, or poor maintenance could certainly cause circulator troubles.

I would replace the circulator pump assembly entirely. A seized motor that burned the pump seals is likely to be at or close to total failure even if you got the motor going again. I'd prefer not to have to repair the circulator twice.

Intermittent Circulator Pump Failure FAQs

How to diagnose one heating zone that fails intermittently

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 2017-12-16 by Brad

by (mod) - diagnostic checklist for a heating zone that 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.

Circulator on Domestic Hot Water Supply FAQs

Takes too long for sink hot water to get hot

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 2017-08-19 by Michael

by (mod) - if you're circulating water full time and the water's not hot, check these items:

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

Some Heating Zones Don't Get Hot: Circulator Failure?

Some of our heating radiators suddenly stopped working: we think it's the circulator

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 2016-12-06 by Rob

Answer by mod: test the cirulator pump motor

Rob, while it's normal for a circulator pump body and motor to get pretty hot when the system is running (circulating hot water at over 180 degF), if it's scalding hot I suspect that the circulator pump motor itself has seized. Replacing the pump impeller assembly (which is what I think you did) won't fix a burnt out circulator pump motor.

Ask your heating service tech to test the motor itself, and to replace it if its bad.

Daniel Friedman

Heating circulator pump not heating first floor but higher floors get heat

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 (Feb 16, 2015) Mirso Dragovic

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.