Heat Won't Shut Off


Hello all,
I have an older boiler and both downstairs and upstairs thermostats are set to 60. However, the thermostat reads just a tick under 80. The pipes/radiators feel very warm. Is there anything I can do to correct this, short of turning off the boiler? I would like to get this working properly myself, but do I need to call a professional?
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Could be a few things. Thermostat, stuck relay, stuck contacts.
You can eliminate the thermostats by simply disconnecting them. Just remove one wire. The thermostat operates a relay that pulls in the 120 volts to get the heater running. If the contacts stick, that will do it also. I'd want to be assured they are working properly if you do release them from sticking. You don't want to leave the house for the day and have it stick again. Sometimes you need a pro.
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The heat will stop upstairs if I turn the knob at the bottom of the cast iron radiater towards "CLOSE". However, this seems to stop heating the entire upstairs. In addition, when I slightly "OPEN" this knob, the heat seems to get uncontrollably warm again, to approximately 80 degrees.
Edwin Pawlowski wrote:

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OK, you have a water circulation problem.
Possibilities:
The circulator is stuck running. You may have one for each zone, you may have one for the entire system and zone valves. Could be a stuck zone valve
In the system, there is a valve that is supposed to stop water from circulating from gravity. It may be defective or not adjusted properly.
If you cannot easily find and correct these things, call a plumber. Just the loss in fuel since you posed the original question is probably enough to cover the cost of a pro making a service call and fixing it right.
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Beyond the electrical possibilities that Ed described, it could be plumbing. If you have a coil in the boiler for hot water, and two circulator pumps for the heat zones, you'll also have flow check valves which can leak hot water through the line. You may have zone valves in the system, which can stick in the open position and cause hot water to leak through

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If the "boiler" has a domestic coil for hot water, it will maintain tank temperature via an aquastat in the water jacket

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