Whole House Fan running slow

Old 06-01-13, 05:44 PM
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Whole House Fan running slow

We have a "Dayton 48 Belt-Drive Exhaust Fan - Model: 3C148", 42" blade diameter.

It is powered ON by a rotary timer switch in the hallway, that can go from 1hr to 12hrs.
There is some sort of junction box on the wall besides the fan in the attic, which seemed to have speed or other controls, but whatever was there has been removed and 2 wires have been "directly" connected to the fan.
A burnt Honeywell R8168-A "cooling fan relay" was originally found in the attic - not sure if it used to be for this fan or another smaller attic fan that is also present in the roof.

In any case, the fan came with the house, so we do not know anything about it. It seemed to run fine last year. We had to manually open the louvers in the hallway ceiling; and the fins on the outside of the house appeared to open almost fully when the fan was going. The hallway louvers needed to be kept open manually (piece of wood), since the fan was never able to open them just by moving the air.

Last year, the fan worked fine and seemed to be running at good speed ("full speed" as far as we know, since there is no speed control) and kept the house cool. The operating speed seemed OK, since it was circulating the air and we could feel the air move when standing in the hallway.
However, this year, the fan is running very slow, nowhere near what it used to spin. The outside fins open just partially.

I'd like to know if there is anything we can do to service it as much as we can, call an electrician to look at it, or if the fan is just gone and we should look to getting it replaced.

Old 06-01-13, 06:29 PM
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I'd start with cleaning the louvers and fan itself, some have oil cups that you can add some oil to.
I'd also be checking the belt. Belts can go bad, used or not.
Old 06-02-13, 05:07 AM
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Belt tension will affect fan speed.
Old 06-02-13, 07:50 PM
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My guess is the relay was in place to prevent the fan from running if the air conditioning was running. As for poor fan operation, check the belt for tension and condition. It should give around an inch of deflection when pressed midspan by your thumb. Do you have enough windows open in the house? Starving the fan for air will cause this problem. Check the motor and fan bearings for lubrication fittings. If the motor has oil holes, given them some SAE20 oil, or whatever the tag says. The fan bearings may or may not have grease fittings. If so, give them a shot of lithium grease.
You have a FAR better fan than the ones available nowdays. I wouldn't replace it.
Let us know if you have any questions.
Old 07-15-13, 02:02 PM
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Thanks Andy, Hvactech and Joe,

You were right about the belt tension. I moved the motor down a fraction today and tried to tune the tension on both sides of the "V". It worked and the fan is humming along nicely!

You are absolutely correct about this being such a good fan, would love to service and keep it maintained. I will go back and check for oil holes - any guidance on servicing or service manuals etc. will be greatly appreciated.
Old 07-15-13, 05:50 PM
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Keep the blades clean, change the belt when it shows sign of wear, lubricate the fan bearings if any type oiling hole is available. That's about it.

My Chelsea whole house fan is over 40 years old and still going strong.

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