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-   -   House fan started running on its own! (http://www.diychatroom.com/f18/house-fan-started-running-its-own-72572/)

Kamishki 06-01-2010 02:27 PM

House fan started running on its own!
 
Hi folks,

I have a little problem in the attic at the moment.
I have both a house fan and an attic fan.

The house fan is a two speed (like 36") belt driven fan with an on/off and High/low switch (All with three wires) and the Attic Fan is thermostatically controlled and it has a regular switch mounted next to the thermostat that will turn off power to the attic fan. It is single speed and fed with just a hot and neutral.

The system is all fed from a single junction box with the hot going into a fire stat.

The power for the attic fan comes out of the same box and if my memory serves me....the attic fan will shut down if the house fan is on.


So...here is the deal. All of a sudden the house fan turned on..and did so by itself and seems to be running in the low position (possible slower than low - it doesn't sound quite right!)

If I turn house fan switch on and have it set for low nothing changes. If I turn it to high....it sounds very bad like the motor is getting heavily loaded.

If I Kill the attic fan with the kill switch or otherwise disconnect it, the House fan will work normally.

I have a call out to friend who is an electrician and I plan to get up there tonight to try to create a schematic...but can anyone give me a tip.

Thanks
Keith

Wildie 06-01-2010 10:17 PM

Quote:

Originally Posted by Kamishki (Post 449685)
Hi folks,

I have a little problem in the attic at the moment.
I have both a house fan and an attic fan.

The house fan is a two speed (like 36") belt driven fan with an on/off and High/low switch (All with three wires) and the Attic Fan is thermostatically controlled and it has a regular switch mounted next to the thermostat that will turn off power to the attic fan. It is single speed and fed with just a hot and neutral.

The system is all fed from a single junction box with the hot going into a fire stat.

The power for the attic fan comes out of the same box and if my memory serves me....the attic fan will shut down if the house fan is on.


So...here is the deal. All of a sudden the house fan turned on..and did so by itself and seems to be running in the low position (possible slower than low - it doesn't sound quite right!)

If I turn house fan switch on and have it set for low nothing changes. If I turn it to high....it sounds very bad like the motor is getting heavily loaded.

If I Kill the attic fan with the kill switch or otherwise disconnect it, the House fan will work normally.

I have a call out to friend who is an electrician and I plan to get up there tonight to try to create a schematic...but can anyone give me a tip.

Thanks
Keith

My first hunch would be that it may be a problem with the neutral.
At least that's what I would look at first.

brric 06-01-2010 10:57 PM

Quote:

Originally Posted by Wildie (Post 449955)
My first hunch would be that it may be a problem with the neutral.
At least that's what I would look at first.

On what basis would you decide this?

Wildie 06-01-2010 11:13 PM

Quote:

Originally Posted by brric (Post 449986)
On what basis would you decide this?

A hunch!

andrew79 06-02-2010 06:44 PM

sounds more like the motors not getting the required voltage to me. sounds like it's trying to run but the juice just isn't there. throw a test on the power at each fan with the switches on and see what you get. There's obviously some sort of interlock between the two fans if one shuts down when the other is running. start with the attic fan and it's controls...seems to be the most likely culprit.


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