Blower fan won't shut off, heating more than called for


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Old 04-28-14, 05:46 PM
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Blower fan won't shut off, heating more than called for

We have a wood boiler outside that runs hot water into coils in our forced air furnace inside the house. The last few days, the furnace blower doesn't shut off and will keep running despite heating past the called for heat or shutting off the thermostat. We have to shut the power off to the furnace to get the blower to shut off. Once restarted it will run fine for a couple of days, then do it again. We have the thermostat set at 72* and have woken up to an 82* house!

We have 2 thermostats, one to control the furnace for the wood boiler (I am assuming it just controls the fan). A second thermostat is for back up propane heat and the central A/C unit (which is not currently on/set to off for both heat and cool).

I am not sure what additional information is needed, so ask and I'll see what I can provide.
 
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Old 04-28-14, 06:02 PM
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Welcome to the forums.

A make and model number of the unit that won't shut off would be helpful.
Usually if you have a hot water coil in it ..... it would just be an air handler..... not a furnace since it doesn't have a burner.
 
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Old 04-29-14, 06:35 AM
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It is actually a furnace retrofit with the water coils. If the boiler part is shut off, you can still run propane heat through it. It is a Lenox Elite Series with model number C33-24B-2F.
 
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Old 04-29-14, 06:55 AM
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These are a few photos. The thermostat in the photo is the one that controls the boiler. It is a 2-wire honeywell.
 
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Old 04-29-14, 07:53 AM
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The thermostat in the photo is the one that controls the boiler. It is a 2-wire honeywell.
I see that. So that thermostat just controls the boiler. Not the blower.

You can't set the other t'stat to heat or the propane part will come on.
How do you turn the blower fan on ?
 
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Old 04-29-14, 09:14 AM
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Sorry, to be more clear: The thermostat pictured controls the blower in the furnace pictured. It calls for the blower to come on when heat is needed. The boiler is outside, heating water with wood fire. The hot water from the outdoor boiler comes inside and runs through coils in the furnace pictured. The thermostat pictured just turns the blower on in the furnace pictured so that air travels through the heated water coils and throughout the home.
And yes, the other thermostat is strictly for the propane heat and would control the furnace traditionally (lighting a pilot light, heating air, forcing it through ducts).
 
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Old 04-29-14, 09:25 AM
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Here is the set up.
 
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Old 04-29-14, 09:30 AM
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Do you have a wiring diagram of how the thermostat is controlling only the blower?

Is there another relay somewhere?

If the blower is running continuously, there is a 'stuck' control someplace...
 
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Old 04-29-14, 12:01 PM
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The best place to start is to go to your furnace and temporarily remove the two wires that go to that thermostat. You'll probably find them on the G and R terminals.

Actually.... just remove any wires that are on G and see if blower stops. If it does... you have a thermostat or wiring problem. If it continues to run then it is an internal problem with the furnace..... possibly the control board.
 
 

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