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Old 11-02-2002, 03:40 PM   #1
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Larger Fan Blades in top Vent

I looked thru this section and saw reports on the Fantastic fan which I know is great from others comments. I wonder if any of you have just replaced the 'fan blades' on their original fans that A/S supplies. The blades are only 6-1/2" diameter, yet the opening could easily take a 9" dia blade. This coupled with a SPDT switch and a resister could easliy make a two speed more efficient fan with only small modifications.

It would be much quieter on low and avoid the expense and time to replace with Fantastic ( which I may do later at some point).

Who has tried this?

Also I DID replace the bathroom vent fan blade. It had become brittle and lost couple fins making it off balance. New one is fine on the old motor.

Steve in Sav'h
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Old 11-16-2002, 01:43 PM   #2
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Changing Fan Blades

Thought I'd refresh this post.

Any recommendations on where to buy some replacement fan blades for the top vents?

Steve in Sav'h GA
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Old 07-09-2003, 03:27 PM   #3
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Job nearly done

A much later update....

I did replace the 6" fan blades in both top vents of the A/S.

The Thorgren blades were small and the Grainger 9" blades surely pull a lot more air thru the top vents.

One minor modification was to replace the aluminum straps holding the motor with two longer ones that I could bend down at both ends to create a 'drop' of about 7/8" on the motor. That allowed sufficient clearance when the top vent was cranked down. I simply put them in a vise and bent two angles at both ends.

Next is to add one or two slower speeds. Pahaska (John) used 2 - 15 ohm resistors to reduce the voltage down slightly for a slower speed.

My question based on Internet search was to maybe use silicon diodes to reduce the voltage down perhaps more efficiently.

However my Radio Shack stores are not of much help in this reguard. Any electricians on board?

Steve in Sav'h
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Old 07-09-2003, 05:56 PM   #4
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Re: Job nearly done

Quote:
Originally posted by Sav'h Steve
A much later update....

I did replace the 6" fan blades in both top vents of the A/S.


Next is to add one or two slower speeds. Pahaska (John) used 2 - 15 ohm resistors to reduce the voltage down slightly for a slower speed.

My question based on Internet search was to maybe use silicon diodes to reduce the voltage down perhaps more efficiently.

Steve in Sav'h
That was 10 ohm resistors that I used, rather than 15 ohm. They come in packs of two at Radio Shack. Radio Shack only had 10 ohm ceramics if I remember correctly.

Not sure what you would do with diodes. A silicon diode has a small forward drop, but you would have to series a whole string of them to get an appreciable slowing of the fan.
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Old 07-09-2003, 06:25 PM   #5
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"A silicon diode has a small forward drop, but you would have to series a whole string of them to get an appreciable slowing of the fan."

John,

I did not know this. I was thinking of the heat the resistors may build up. I guess that one could use 2 - 10 ohms for the 1st speed (voltage) reduction, and then 3-4 of them for the second slower speed for a low noise, low speed fan.

Do you see any problems with this idea. I think only one speed reduction on the stove vent fan is all that is needed.

TIA,
Steve
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Old 07-09-2003, 06:35 PM   #6
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Resistors

Try it with one pack of 2 10 ohm ceramic resistors. One in series for a medium speed and two in series for a slower speed.

You will find that they don't get very hot. Ten ohms with the fan motor in series is going to drop less than a watt. A 10 ohm, 2 watt resistor would do just fine. I used the 10 watt because it was available and barely gets warm.
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