Attic Fan - Testing


Old 06-28-10, 08:46 AM
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Attic Fan - Testing

I have an attic fan that was supposedly replaced prior to purchasing our house. It hasn't run this summer and I suspect there is an issue.

I got a new thermostat (Master Flow for fan/thermostat, sorry don't have model number at work). After installing it, I tried setting the temperature very low to get the fan to kick on and it didn't.

The wire is good, tested with voltmeter.

Before I assume the fan itself is broken, I want to test, but wasn't sure how.

If I direct wire the fan to the power source, bypassing the thermostat, the fan should kick on when the breaker is turned on, correct? If that doesn't work, I can assume the fan itself has a problem. I haven't been able to find and answer, and I want to confirm it's a problem with the fan and not the thermostat.

any thoughts would help.
Old 06-28-10, 10:02 AM
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Yes...what you propose should work for testing. The 'stat is just functioning as another switch in the circuit.

Just in case...many attic fans have lifetime warranties on the motor...IF you can find a manufacturer label.
Old 06-29-10, 06:00 AM
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Had another thought this morning, can't find the answer online.

The thermostat was mounted at an angle on one of the roof beams. Does it need to be level to operate correctly? It's a masterflow thermostat.
Old 06-29-10, 10:12 AM
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That thermostat is probably bi metal and can be mounted at any angle. Look at it and see if it has a small glass vial with two wires coming from the vial. If it does, what and see if the mercury in the vial runs from one end to the other when you dial the t'stat up and down.

Again, I don't think you will find a vial. Take a thermometer up in the attic and see if it is hot enough to kick the t'stat on. Some don't come on at lower temps. The minimum on temp should be marked on the stat. Yes, you can bypass the stat. As Gunguy45 said, the t'stat is just a switch.

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