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[banjoman]

I need a little help with a problem I am having with the fan on my oil furnace since I installed the Hx in the plenum for my OWB.  As long as I keep the temp on my OWB around 145 deg. everything works fine. If I increase the temp above 150 the furnace fan won't turn off. It continues to blow heat even if I turn the thermostat off. I have to turn off the breaker to the furnace and let it cool down before it operates properly. I am sure it is the high limit seeing a higher than normal temperature causing it to run.

This is what I have found so far, the fan motor has lead designations "H,MH,ML,L,C". I have wires connected to "H,MH, and C". (red-orange-white). I have currently disconnected the orange wire (or MH) and it seems to work fine. The orange wire goes to the fan limit switch.

I really don't want to disable the fan limit switch or increase the temp setting if there is another solution as it is a safety device for the oil furnace. Anyone have a suggestion??  I do have a schematic for the furnace and can post it if needed.

[MattyNH]

I need a little help with a problem I am having with the fan on my oil furnace since I installed the Hx in the plenum for my OWB.  As long as I keep the temp on my OWB around 145 deg. everything works fine. If I increase the temp above 150 the furnace fan won't turn off. It continues to blow heat even if I turn the thermostat off. I have to turn off the breaker to the furnace and let it cool down before it operates properly. I am sure it is the high limit seeing a higher than normal temperature causing it to run.

This is what I have found so far, the fan motor has lead designations "H,MH,ML,L,C". I have wires connected to "H,MH, and C". (red-orange-white). I have currently disconnected the orange wire (or MH) and it seems to work fine. The orange wire goes to the fan limit switch.

I really don't want to disable the fan limit switch or increase the temp setting if there is another solution as it is a safety device for the oil furnace. Anyone have a suggestion??  I do have a schematic for the furnace and can post it if needed.

Well I got a kick-space heater under my kitchen sink cabinet..The fan comes on at a certain temperature and then shuts off at a certain temperature..I can turn the heat off 100%..That kick-space heater fan still will run until the water in the space heater is at a certain temp..Maybe your oil furnace is the same way???