Heater keeps heating room and thermostat is not calling for heat

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Old 11-12-11, 03:48 PM
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Cool Heater keeps heating room and thermostat is not calling for heat

My oil heater keeps heating one of my zones when the thermostat is not registering needing heat. We replaced the thermostat and that didn't help. We have 4 zones in the house and the heater also heats the hot water. (not a tank). (No central air and baseboard heat).
 
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Old 11-12-11, 04:57 PM
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You probably have a "hot" boiler. This is when the boiler is set up to keep the water hot all the time.

When a thermostat calls for heat in one zone, a zone valve opens and allows the hot water to flow to that part of the building. Any number of zone valves can be on at one time as needed.

Sometimes there will be separate pumps that are switched on for each zone, but usually it's electrically operated zone valves.

You can probably identify the zone valves in the boiler room by switching various zone valves on and off with thge thermostats.

Identify each one and observe them opening and closing. This should allow you to identify the one that isn't working properly, probably sticking in the open position. You may be able to free that up by moving it by hand.
 
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Old 11-12-11, 05:56 PM
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Thank you for the quick reply and information. We've had 4 zone valves and over the past couple years all of them have been replaced and still have the same problem. All the thermostats have also been replaced previously. Example we set thermostat at 64, it keeps calling for heat even though the thermostat will read 71 degrees. It also just seems to happen periodically though they day and sometimes it actually works.
 
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Old 11-12-11, 09:51 PM
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I'd measure the voltage being applied to the zone valves by the wires coming from the thermostat. They could be shorted together somewhere along the length of the wire, causing the zone valve to stay open despite the fact that the thermostat is not calling for heat.

It shouldn't be that tough to check out. Is the zone valve open when there is no voltage present to open it? If so, you have another defective zone valve. If there is no voltage to it, it should be closed!

If there is voltage to the zone valve, is the thermostat calling for heat? If not, you probably have defective wiring that should be replaced. Rats gnawing on wiring are a good source of a problem.

If I found that condition, I'd probably abandon the existing wiring and run new wire to the thermostat.
 
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Old 11-13-11, 02:47 PM
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Thanks for all of your wisdom. I'm going to contact me brother in law who will help me.
 
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