Whole house fan: direct drive vs belt

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Old 10-08-15, 05:38 PM
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Whole house fan: direct drive vs belt

Summer is over and I am planning for the next Summer.


Is it better to get a Directive or a Belt driven Whole House Fan?
 
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Old 10-08-15, 06:56 PM
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I had a belt drive with a two speed motor years ago. I think that the belt drive blades can turn slower, with a deeper pitch, than a direct drive. That pulls more air with less fan noise.
 
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Old 10-08-15, 07:53 PM
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I have a 40" belt drive...... an old Chelsea fan. Moves a lot of air and is very quiet.
The belt drives are definitely quieter.
 
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Old 10-09-15, 04:06 PM
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How often do you have to change the belt? Overall: does a whole house fan make a huge difference? Compared to a gable fan, possibly?

I am thinking of doing belt for my house since I can climb up the attic.

But for my mom's house, I may have a contractor install a directive since it is more tricky to climb up the attic. In other words, I am afraid of, possible, rat encounters in her attic. Hahaha!

Originally Posted by goldstar
i had a belt drive
you said that you had. What happened to it? Did you move or did it break down?
 
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Old 10-09-15, 04:17 PM
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I have a split level house with a large end gable that is at the opposite end of the house from the bedrooms. That's where my fan is. I would not want it installed in my upstairs hallway as many people have.

I also have a thermostatic roof mounted exhaust fan in the attic directly above the bedrooms. I have adequate attic air flow for that exhaust fan.

When I run the whole house fan I need to leave the door to the attic hatchway ajar to draw air in from the house. I also need to have at least five windows open or the hot water heater pilot will be extinguished by the suction.

I've changed the belt twice in 40 years. Changed the motor at 35 years.
 
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Old 10-09-15, 04:37 PM
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Thanks for the information Pete!

Directive drive are louder but I think that will be the way to go for my mom's house, basing on the information that you shared.

Also, may I ask how much did it cost for you to change just the motor? As well as the belt? I know you are very handy but to the average person, what is the level of difficulty?
 
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Old 10-09-15, 04:44 PM
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The belt was around $8 and the motor I bought off of Amazon was around $45.

Both easy to change. The four motor bolts get removed to replace the motor and just loosened to slide the motor to adjust the belt tension.
 
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Old 10-09-15, 04:56 PM
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Thank you Pete!

Twenty-five character limit.
 
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Old 10-09-15, 05:06 PM
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Directive drive are louder but I think that will be the way to go for my mom's house, basing on the information that you shared.
First, direct drive, not directive.

What information makes you think a direct drive is better suited to your mother's house? That PJ has to open a minimum of five windows, that he has to open his attic hatch or that he has had to replace a belt twice and a motor over a forty year period?

You MUST open windows to replace the air being discharged by the whole house fan. If you don't then all the fan does is make noise and waste electricity. It is the changing of the hot inside air with cooler outside air that does the cooling. If PJ had the proper sized motorized damper installed, one that would open before the fan started and close after the fan stopped he wouldn't need to open the attic hatch. He would STILL need to open the windows as I previously explained.

Maintenance is required with anything mechanical and I think that two belts and one motor over forty years is really minimal maintenance. More likely as not a direct drive fan would require more maintenance, not less.

Whole house fans, because they bring in massive amounts of air from outside also tend to bring in massive amounts of dust if you live in a dusty environment. If you have air conditioning that you use during the day that will lower the inside relative humidity but as soon as you start that whole house fan and bring in the humid night air you will again raise the inside RH to the same levels as outside. Then the next day the A/C has to work first to remove that humidity before it really starts to cool the inside air.

Whole house fans really only make sense in climates that already have low humidity, like deserts. Multi speed motors make more sense than single speed units.

If you want to make a little test to see if a whole house fan might work you need to place a box fan, about a 20 inch model as a minimum, in a window and close off any opening around the fan with some cardboard. Open a window or two at the other end of the house and then start the fan in the window. If a two-story home then an upper window for the fan with the lower windows open. Try different fan speeds and note the noise levels as well as the "wind" throughout the house.

Years ago I would do this with my house, usually placing the out-blowing fan in the kitchen window and then opening the bedroom window as well as a window in my back room and it would definitely cool off my house BUT if the RH outside was high, generally in the early spring or in the fall, the whole house would get so muggy that I almost had to wear SCUBA gear to breathe. (Slight exaggeration.) It would also bring in enough dirt and dust (plus smells, often from forest fires) that it just wasn't a practical solution. I also needed to keep all the interior doors open to any room where I had opened a window.
 
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Old 10-09-15, 05:54 PM
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Originally Posted by Furd
First, direct drive, not directive.
Yes, you are right. I started off in my post title with Direct and not sure why I started to use Directive.


Originally Posted by Furd
What information makes you think a direct drive is better suited to your mother's house? That PJ has to open a minimum of five windows, that he has to open his attic hatch or that he has had to replace a belt twice and a motor over a forty year period?
PJ changed the motor after 35 years and I don't want to go up to her attic. By then, I am already in my mid 80s and she is well...


Originally Posted by Furd
You MUST open windows to replace the air being discharged by the whole house fan.
Yes, agree. I saw this video before I even posted: Quiet Whole House Fan | Comfort Cool Fans


I also have read about the disadvantages of a Whole House Fan when it comes to pollen and humidity. So, I agree with what you shared.


I appreciate your example of a box fan. Two things popped into mind: First, the box fan in a regular window may not mimic to the exact science since a Whole House Fan's purpose is to push hot air out of the attic. Since there is still hot air in attic, could that be the reason that caused the muggy heat in your house? Second, I think you brought up a very good point about the polluted air (smell from the forest) coming in. Since I live in the city and about a hundred feet from a main street, I don't want to bring carbon monoxide and exhuast into my house. So this is a very good reminder and this may sway my decision for both houses. Thanks
 
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Old 10-09-15, 06:03 PM
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When it comes to humidity, we have only about (collectively) two months of humidity. Best time for a Whole House Fan for us would be in March, April, May, June and October. August and September can get pretty humid.

But again, with your event (forest smell) and PJ event (pilot light extinguished), I am convinced that this may not be the best solution for me, from the possible air pollution and my allergies.
 
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Old 10-09-15, 06:35 PM
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Two things popped into mind: First, the box fan in a regular window may not mimic to the exact science since a Whole House Fan's purpose is to push hot air out of the attic.
No. The purpose of the whole house fan is to exhaust the hot air from the living spaces to the great outdoors and in the process bring in cooler outside air. The exhausting of hot air from the attic, and how much of that occurs, is related to the manner in which the whole house fan is installed. Most whole house fans are internally mounted and they blow the house air into the attic space where it leaves via large passive vents from the attic to the outside. Some whole house fans are mounted in an outside wall, sometimes in a common area (hallway) in the living area and blow directly outside. Sometimes, as in Pj's installation, the fan is located in an outer wall of the attic space and can serve as both an attic ventilator and a whole house fan.
Since there is still hot air in attic, could that be the reason that caused the muggy heat in your house?
No. The attic is naturally ventilated and it is also sealed (more or less) from the living spaces. The insulation in the attic floor retards the passage of heat into the rooms below.

PJ changed the motor after 35 years and I don't want to go up to her attic. By then, I am already in my mid 80s and she is well...
And you may need to change the motor on a direct drive in less than five years. Mechanical things need maintenance, there is no getting around that fact.

Quite honestly, whole house fans were in vogue many years before air conditioning was common in personal residences. It was a fairly inexpensive method of cooling homes using cooler nighttime air. It had (still has) a lot of faults and those faults are often sufficient to rule out its usage, even in climates where it would otherwise work fairly well. You still need to have the house fairly well insulated as well as some means to shade east and south facing windows to reduce the solar gain during the day. The open windows are contrary to home security and the humidity factor is often the final nail in the coffin.
 
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Old 10-09-15, 08:12 PM
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True..... Furd brings up a lot of good points. Yes... I should have put a motorized damper in the hall years ago. Due to the setup of the hip roof there is very little room to put in a damper.

I have mine on a digital timer. I will usually open the windows when I go to bed and set the timer for two hours. If it's on much past 3:00am it brings in a lot of damp air. I would say I use the fan about 45 days a year..... mostly in the spring and fall. Now is a good time of year for it.
 
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Old 10-10-15, 03:10 PM
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Belt drive is the way to go. As others have said, much quieter, and maintenance isn't really much of an issue. Here in Wisconsin, they are awesome in the spring and fall, with the warm days & cool evenings. We use ours a LOT during these seasons, but I agree with Furd regarding humidity. They're NOT a replacement for air conditioning if you are in a humid climate.
Andy
 
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Old 10-11-15, 05:39 AM
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Directive drive are louder but I think that will be the way to go for my mom's house, basing on the information that you shared.
A well balanced direct drive is far quieter than belt.

It's balance (or lack of balance actually) which causes most of the noise. It's incredibly hard to balance a belt and pulley system

Personally I would skip psc motors and look into direct drive ecm. It's more expensive but lasts longer, quieter, and offers better control.
 
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