whole house fans II

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Old 07-22-03, 11:44 AM
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whole house fans II

I know I asked this before but I could not find it...

Put in a whole house fan summer before last. Worked great. Pulled so much air thru the house we had to use doorstops to keep the doors from slamming shut. This winter I added an attic fan with auto thermo to come on @ 90. All seemed good.

But right when it started to get real hot and the evening whole house fan ritual was to begin, I noticed less air being pulled by the fan. Used to be you could open one windon in the kitchen and the breeze inward would be so strong as to know down the flame on the gas stovetop. Now, you can barely feel a breeze at all.

I checked for gable blockage, and nothing other than the material they use to screen them from pests. I did notice the attic fan (attached to the gable) was not on and it was well over 90 up there. Found it was shorted out. Electrician coming today to fix that.

But that leaves me with a whole house fan that appears to be working ok, sounds good, nothing visible...I did check and it's not a belt drive....so that can't be it.....but the bugger just isn't pulling. As a matter of fact, when it comes on it usually pulls the louvers up quickly and completely, not now....they come up slowly and one side didn't flip up all the way.
Help? Is my fan shot after two summers?
thanks
mw
 
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Old 07-22-03, 11:56 AM
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Sounds like it's taking the path of least resistance and maybe pulling air backward through the attic fan. Is there dampers on the attic fan preventing backdraft?
 
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Old 07-22-03, 12:08 PM
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the attic fan itself is bolted to the gable in the attic.....right now, it's not working due to the short...
we used the whole house fan one full summer before we added the attic fan and it worked great, meaning it pulled lots of air thru the windows and thru the house.
I didn't answer your question directly because I guess I don't know the answer...I did see the attic fan off shile I was up there and the whole house fan was on, but it was static, blades not moving on the attic fan at all. Whole house fan "sounds" like it's going full speed....but not much air moving.
 
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Old 07-22-03, 07:52 PM
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MW,
Something has changed in your house. Here are my 3 suspects: You have an obstruction in the free exhaust area in your attic, or you have not enough intake (not enough windows open), or the ceiling louvers are not operating smoothly (being obstructed so they don't open all the way). Since the only thing that has changed is the addition of the attic fan, I would suspect option 1. Try holding the gable attic fan's louvers open (unless they are fixed open louvers), and see if that improves the whole-house fan performance. It's also possible that the new attic fan is creating enough of an obstruction in front of the louver that is holding back airflow.
Let us know what you discover!
 
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Old 07-24-03, 03:43 PM
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We have now checked to see if there is any obstruction in the attic on or around the gables....it appears to be open and free. There is that material on the inside of the gable that keeps birds out....the attic fan had a short and was not working....now it is...no change in the pulling of the whole house fan. We "dusted" the whole house fan and louvers....no change. I did notice the fan was not pulling enough to open the louvers all the way, I checked, they were not obstructed.

Looks like motor is not pulling the air...my question is this (based on what I'm hearing now) Could me whole house fan's performance be diminished if it ran once with no windows open? In other words, could we have "burnt" it out? And if so, can I go buy a replacement motor and not buy a whole new fan?
thanks for the help guys....
mw
 
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Old 07-25-03, 05:08 AM
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Is the whole house fan in the attic with the attic fan? Or is it mounted to the floor of the attic pulling directly from the house. I ask this because I've seen where the whole house fan was put up in the attic on one end of the wall with gravity dampers on the floor of the attic. On the other end was the attic fan. When they ran together the whole house fan was of course larger than the attic fan and pulled air backward through the attic fan putting a heavy load on it eventually burning it out. Fix was to install backdrafrt dampers on both and interlocks so they didn't run together.

Running the whole house fan with no windows open shouldn't kill it right away. Restricting the air across a fan actually drops the load across it in turn the amp draw drops down.
 
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Old 07-25-03, 09:52 AM
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the whole house fan is mounted on the floor of the attic....the hallway roof of the house. It is placed about center of the house to pull from both "ends"....the attic fan is of course in the attic mounted to one of two large gables....it is not the same diameter of the gables...smaller...so it is now bolted to a 2x4 frame about 3 inches from touching the actual gable.
Can the whole house motor (for whatever reason) now be pulling less amps on every use regardless if how many windows are open? Keep in mind, it used to pull the doors shut with almost all the windows in the house open, now you can barely feel any air coming in when only a few are open. The fan looks and sounds like its still moving as fast.....it's a two speed and neither speed is noticably slower, yet the air being pulled is obviously less.
I really appreciate you guys sticking with me on this one....I just want to get this solved.....also, can you just "slap" a replacement motor on this thing or is that a job for a professional?
MW
 
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Old 07-25-03, 05:30 PM
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"Restricting the air across a fan actually drops the load across it in turn the amp
draw drops down."

This statement is true IF the fan is a centrifugal (squirrel cage) fan. If the fan is an axial fan (normal bladed fan), amp draw will go up as static pressure increases, and can definately overload the motor.
 
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Old 07-25-03, 05:47 PM
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latest

So I called Lowes and talked to the guys at the contractor desk....really nice and helpful. They gave me the fan company's service number. I called, got another really nice woman. She asked what the fan was doing, asked a few more questions, then took my name and address. They are sending me a new motor. Free. She did suggest that since I'm such a lame-o that I get an eletrician to put the new motor on. But based on what I told her, she said the motor was not working to capacity. I guess it's all solved, but I'd sure like to know why it went bad....was it me or just the luck of the draw?
Oh well. thanks everyone, any advice as to whether I should try to replace the motor.....I can do simple tasks????
thanks again
mw
 
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Old 07-25-03, 06:01 PM
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If this is a belt-driven fan, there should not be a problem replacing the motor. Just put the new one in the same as the old one.
 
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Old 07-25-03, 06:25 PM
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amp it

one test to do, is amp the motor against it's rated load RLA or FLA printed on the side of the motor while under load. The other thing to check, is if the set screw is secure...make sure the motor isn't spinning/slipping about the motor shaft. It should have a flat. Your may end up with trouble, removing the blade. Hit it now with penetrating oil, too soak in. This will save you a big head ache later, when your in a rush to get it in. I found if I had too many places for the air to pull from, the air flow was diminished...
 
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Old 07-26-03, 12:40 AM
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Originally posted by Andrew
"Restricting the air across a fan actually drops the load across it in turn the amp
draw drops down."

This statement is true IF the fan is a centrifugal (squirrel cage) fan. If the fan is an axial fan (normal bladed fan), amp draw will go up as static pressure increases, and can definately overload the motor.
Take a box fan and block the airflow and check amps the whole time. They will drop. A variable pitch vane axial fan or a fan that loads up with a static pressure controller will load up but not a fixed. The air is the load. Take away the load and the fan don't work as hard.
 
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Old 07-26-03, 08:51 AM
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thanks and one more question

hvac wrote

"The other thing to check, is if the set screw is secure...make sure the motor isn't spinning/slipping about the motor shaft. It should have a flat. "

where would i find this set screw? THAT actually sounds like a real possibility.
BTW, I too found that if I open ALL the windows it pulls ( or seems to) less....but I remembered that and just opened one window, the one that pulled the flame on the stove flat and closed two doors.....and it now only barely moves the flame and the doors dont even budge.....BUT that screw may be something. Where is it?
Thanks again everyone, I really needed the help.
mw
 
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Old 07-26-03, 11:28 AM
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The set screw would likely be on the pulley mounted to the shaft of the motor. There may also be one on the pulley mounted on the shaft to the fan blade itself. The set screw puts pressure on the flat place ground into the shaft to keep the pulley from slipping around the shaft when the belt pulls the pulley.

It may have an allen head set screw.

HTH
 
 

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