Heat randomly stays on in one zone

Old 03-31-15, 09:40 AM
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Heat randomly stays on in one zone

Hi all,

I have a 3 zone hot water baseboard heating system and for the past year, the heat in the top floor would sometimes stay on. Once this happened, I usually could get it to turn off by manually turning the heat up past the current temp and then turning it off again. This happened about once a week so it didn't seem to be a big deal.

Yesterday, the heat was on again so I tried turning it on+off but nothing happened after I did it several times. I finally went down and purged the zone and things seemed to be okay. Then at 5am this morning I woke up to a boiling bedroom and tried turning it on+off several times and nothing happened. In frustration at having been woken up I shook the thermostat and hit it with my palm and tried turning it on+off again and lo and behold that did the trick and the baseboards cooled down.

I have replaced the thermostat two weeks ago so it's not the thermostat. I do hear a click at the thermostat whenever it calls for and turns off the heat. I have circulator pumps so I don't think a zone valve is getting stuck. Now I suspect the wiring as it's the only thing that makes sense after it 'worked' when I jiggled and slapped the thermostat.

What could be going on and what can I do to fix it? Thanks!
Old 03-31-15, 10:21 AM
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There's a number of things that could be going on ... to fix it you will need to understand how it works so you can test and come to logical conclusion.

Tell us the make/model of the boiler.

Tell us what is controlling the pumps... for example, thermostat goes to ________________ , pump is wired to __________________.

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