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All Zone Thermostats Off But Boiler Still Working

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Docfletcher
Docfletcher Member Posts: 487
edited November 2018 in Gas Heating
I noticed the living room zone was not working, stone cold baseboard. But 3 other zones were calling for heat and working, nice warm baseboard. The 3 other zone rooms were too hot, I turned down the thermostats but the boiler kept working. I turned all the thermostats off and the boiler still kept working. I turned off the boiler. My thought was some sort of Taco zone valve issue so I twisted each power head off and back on one by one. Powered on the boiler and it seemed like normal standby mode. no circulators running. Turned on living room thermostat, boiler started and baseboard stayed cold. Other zones worked as before when turned on but boiler would not shut down even if I turned the thermostats off. Went back to the boiler and after much tinkering I found that when either of two power heads were removed and the boiler powered on the boiler would start working, even with thermostats off. Here is a photo of the power heads. Why would removing either of them cause the boiler to start working. Maybe shorted internally? Living room zone maybe power head Open?


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  • Docfletcher
    Docfletcher Member Posts: 487
    edited November 2018
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    Well it's 2:15 in the morning and everything is working as it should now. So I don't know what the issue was. I went to the boiler to temporarily disconnect power to the two power heads in the photo. But decided to try running it one more time and found everything working normally again. Now I'll need to wait to see if the problem comes back. It's the old could not duplicate bug syndrome.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
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    It's possible the end switch for the LR zone valve was making, to fire the boiler, but the actuator wasn't opening.
    Or you have a pesky short somewhere in the end switch wires from zone valve to aquastat. I'd assume with 4 zones, 2's & 3's are are ganged together, wire nutted, and one set heading to the aquastat.

    There was an error rendering this rich post.

  • Docfletcher
    Docfletcher Member Posts: 487
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    Yes 2's and 3's are ganged together etc. As for the aquastat I assume your speaking of the boiler high/low limit and not the indirect aquastat. There is a pair directly from the system control panel that connects to the control board connector that says limit on it. Thanks for the information, I'll keep under my hat.
  • Docfletcher
    Docfletcher Member Posts: 487
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    Boiler running like a zone constantly calling for heat. The issue seems to come and go. This is happening even when I turn all thermostats off. I spent several hours dinking around with the problem. Finally I was able to force the problem to happen. When I manually open the zone valve marked 2nd BR in the photo and have the living area thermostat call for heat both the living room zone and the 2nd BR zones heat. When the living room zone stops calling for heat the 2nd BR zone valve still thinks there is a call for heat and keeps the boiler running. Even if the all the thermostats are off this happens. Is the 2nd BR zone valve head bad?
  • Docfletcher
    Docfletcher Member Posts: 487
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    So, tonight I changed the zone valve power head and the problem is resolved. It's not the kind of problem your likely to come across. Everything works as normal including the zone that the bad power head handles, that is till you happen to open the bad power head manually. Then you will know because the boiler and cilculator pump will keep going as though the thermostat for any of your zones is calling for heat. Even if you turn off all the thermostats the system keeps working. For me the 1st clue was the the two zones I was combining became way to warm. Just a little information to put under hat.

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