Circulator pump running almost constantly


  #1  
Old 11-27-23, 09:24 AM
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Circulator pump running almost constantly

Hello -

I have a 4 zone hot water system with Honeywell zone valves, a taco circulator pump and a Honeywell aquastat. Recently the circulator pump has been running almost constantly for extended periods of time - although it does shut off intermittently. It is running even if there is no call for heat and all the zones are closed. It does turn off if I cut the power to the boiler.

Everything else is functioning as it always has. If there is a call for heat, the process initiates with the flue opening, boiler firing and heating the water to temperature and shutting down. At this point the pump always continued to run for a few minutes but now it seems to be going for at least an hour maybe more. The boiler only re-fires if triggered by a zone end switch. All zones are receiving heat properly.

From researching this issue I have come across mention of a stuck relay possibly being the culprit. Although it seems if that was the case the pump would never turn off? How would I go about troubleshooting this?

Thoughts?

Thanks in advance!

Mike







 
  #2  
Old 11-27-23, 01:24 PM
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You have 4 Honeywell zone valves.
Are they the type with 2 red and 2 yellow wires ?
The 2 red wires should all be connected together and two conductors sent to the TT terminals on the aquastat. When the red wires are closed.... the relay closes...the circulator starts and then the burner. It's possible the relay is sticking but not likely.

In the picture looks like a high heat safety control. Problem won't be there.
There should be a gray box on the boiler where the circulator connects.
Take the cover off and you should see the two wires from the zone valves on TT terminals at the top. Remove one wire and see if the relay opens and the circulator stops.

If yes.... you need to go to your zone valves.... break the red wire connections and either use a meter to check for a closed end switch or reconnect one at a time. One problem switch in one valve can keep the system running.

 
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Old 11-27-23, 04:47 PM
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Thanks for the response. Okay after further investigation is seems like zone 4 (4th floor) is the culprit. Zones 1-3, when isolated, all operate as intended. The boiler fires, reaches temperature and the pump runs for a few minutes.
The return pipes all get very hot to the touch.

The # 4 zone fires the boiler, reaches temperature but then the pump runs for an extended period of time, The return pipe and radiators get warm but not as hot as zones 1-3.

Could there be air in that line or not enough water? Would the pump sense this and keep running?





 
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Old 11-27-23, 04:54 PM
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The only other gray box on the boiler other than the previous one is this:



 
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Old 11-27-23, 06:05 PM
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Sounds like there is not a problem other than you are not getting flow to the third floor. The valve is calling and keeping the pump on.
What is your water pressure? It should be about 18 psi for third floor heat.
The return should be as hot as the the other two when the third floor thermostat is demanding heat.
 
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Old 11-27-23, 06:21 PM
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Old 11-30-23, 11:54 AM
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Turns out it was only air in that zone. Purged it and is now working fine. Thanks again!
 
 

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