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petri dish (Petri)
Senior Member
Username: Petri

Post Number: 225
Registered: 07-2003
Posted on Monday, October 25, 2004 - 02:28 am:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

I was wondering if a 120v furnace blower can overpower a flow hood? I can get them fairly cheap and I was wondering if they weren't too much. Is there a simple way to gauge the cfm output of a fan that doesn't say? If I could gauge the output I could wire it accordingly. I was also wondering how to find cfm at inches of static pressure. i.e., does a regular 500 cfm blower drop to 300 cfm at one inch of pressure? How would I figure that?
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rodger rabbit (Skyypilot)
Moderator
Username: Skyypilot

Post Number: 4195
Registered: 02-2003
Posted on Monday, October 25, 2004 - 07:18 am:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

You can always restrict the intake of the furnace blower to cut down on the flow. A good low tek way to get the flow right is to hold a cigarette lighter a few inches from the face of the filter. The flame should bend over, but not blow out.
"Whatever it is, that girl put a spell on me". . .jimi hendrix
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petri dish (Petri)
Senior Member
Username: Petri

Post Number: 226
Registered: 07-2003
Posted on Tuesday, October 26, 2004 - 01:00 am:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

Skyypilot, thanks a LOT!! I was hoping you would stop in and enlighten me. My fans have several wires for different speeds, and one of these is liable to work, but in my dreams, I hook the white and black wire to a ??? that has a knob on it that I can turn to adjust fan speed. Do you know what that thing would be? Thanks again.
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rodger rabbit (Skyypilot)
Moderator
Username: Skyypilot

Post Number: 4204
Registered: 02-2003
Posted on Tuesday, October 26, 2004 - 01:22 am:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

Take a clear picture of the motor data plate and post it. I'll be able to tell you then.
"Whatever it is, that girl put a spell on me". . .jimi hendrix
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petri dish (Petri)
Senior Member
Username: Petri

Post Number: 227
Registered: 07-2003
Posted on Tuesday, October 26, 2004 - 03:22 am:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

This is the first motor I have ever seen without a data plate. I can briefly describe the wires. There are a white and brown going from the starter cap into the motor. There is another white coming off of the cap. There are black, blue and red coming out of the motor. There is a smaller green coming off of the motor which appears to be a ground. When you hook the white from 120v cord to the white coming off of the cap and hook the black from 120v cord to the black coming out of the motor you get high speed. Leaving the whites alone, if you hook the 120v black to the motor blue, you get medium speed. If you hook the 120v black to the motor red you get low speed. I can read some markings on the capacitor, but I didn't think that would be to helpful. I wish I could post a helpful pic, but I can't find a data plate.
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rodger rabbit (Skyypilot)
Moderator
Username: Skyypilot

Post Number: 4209
Registered: 02-2003
Posted on Tuesday, October 26, 2004 - 03:29 am:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

I'll bet if you turn it upside down you'll find the data plate. Perhaps it's kind of hidden by the squirrel cage. It's a violation of the National Electrical Code to sell a motor in the US without a proper data plate.

Sounds like you have it figured out though. White is the neutral, and will connect to the white of your power cord. The green is indeed a ground. It will connect from the chassis of your motor to the green wire on your power cord. Select the speed you want and connect that color wire to your black on the power cord. Go buy a high efficiency air filter and tape it to the air intake. This will pre-filter the air coming in and make your HEPA filter last much longer.


(Message edited by skyypilot on October 26, 2004)
"Whatever it is, that girl put a spell on me". . .jimi hendrix
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rodger rabbit (Skyypilot)
Moderator
Username: Skyypilot

Post Number: 4210
Registered: 02-2003
Posted on Tuesday, October 26, 2004 - 03:31 am:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

Oh yea....Be sure to insulate the unused wires so they won't short out.
"Whatever it is, that girl put a spell on me". . .jimi hendrix
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petri dish (Petri)
Senior Member
Username: Petri

Post Number: 228
Registered: 07-2003
Posted on Tuesday, October 26, 2004 - 03:38 am:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

Thanks again. I bet that plate is on the shaft side of the motor inside the blower housing. If I hook up for max blower speed is there a device I can wire in there that will allow me to adjust fan speed by turning a knob? Am I thinking of a rheostat?
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rodger rabbit (Skyypilot)
Moderator
Username: Skyypilot

Post Number: 4212
Registered: 02-2003
Posted on Tuesday, October 26, 2004 - 03:44 am:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

A rheostat will only control speed on a DC motor. For an AC motor you need one of these.
"Whatever it is, that girl put a spell on me". . .jimi hendrix
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petri dish (Petri)
Senior Member
Username: Petri

Post Number: 230
Registered: 07-2003
Posted on Tuesday, October 26, 2004 - 04:22 am:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

Who would have thunk it, for an AC fan I need an ac fan speed control. I appreciate your patience. Is there a good home for this with flow hoods in the archive? Just a thought. I don't know how many people out there would go through all the trouble, I am a cheap ass. I looked forever for a good deal on the right CFM fan for my first hood, and now I can make a big easy to find fan fit my purpose.
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HF (Highflyer)
Moderator
Username: Highflyer

Post Number: 2643
Registered: 12-2002
Posted on Tuesday, October 26, 2004 - 06:23 am:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

There is alot of good information in this thread...so...Archive Material.

A direct answer to the original question is yes, too large of a blower can eventually blow a hole in the filter.
"I hold it to be the inalienable right of anybody to go to hell in his own way." - Robert Frost