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Old 10-29-2009, 09:28 PM   #1
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2 speed Attic fan switch


Hi there,
I have an attic fan (whole house) that I got and it has a 2 speed motor on it.
It has the pull chain switch to turn it on high, low, and off.
I want to replace this pull chain switch with a switch on the wall.
I thought this would be a pretty simple thing to do, but I'm having some trouble with it.

I bought a SPDT Toggle switch (ON-OFF-ON), and hooked it up with the common going to the center, the high (black) to one side, and the low (red) to the other side, and the nuetral (white to nuetral).
When I turn it on to either side, the fan turns on but always to high, no matter which side I toggle to.

I got the volt meter out and each side has 120V coming out going to the fan.
I have the original pull chain hooked up also, so I tested the volt meter out on it, and found that when high is on, the black wire is putting out 170V and the red wire puts out 120V. When the the low is on, the red wire puts out 76V and the black 120V.

So that tells me that the toggle switch idea I was using is not going to work, as it appears the motor expects different voltages to run the different speeds.

My question now is what type of switch do I need?
Will something like this work?
http://www.grainger.com/1/1/82183-ai...ll-switch.html

How do I know that it will output the appropriate voltages to the motor?

Second question would be is it ok to use a dimmer switch? Typically I think its a bad idea to use a dimmer on a fan because it could cause damage to the motor, but since this motor is expecting different voltages anyway, I thought it may be ok.

Any help or advice is appreciated.
Thanks!

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Old 10-30-2009, 03:45 AM   #2
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2 speed Attic fan switch


You said "white to neutral" in your sentence describing how you wired the new switch. Is the white wire connected in any way to the new switch?

Did you remove the pull-chain switch when relocating the control of the motor to the new switch, and connect the colors as described?

What is the make/model of the new switch? Can you post a picture of the motor/old switch setup?

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Old 10-30-2009, 06:55 AM   #3
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2 speed Attic fan switch


The pull chain switch is probably not a simple single pole double throw switch. You need to analyze it to find out how the various wires attached to it connect together in the high and low positions.

Example only: Applying power to both red and black (white connected to neutral) gives you high, applying power to red only gives you low. Do not make any connections you are not sure of.

You need to find a wall switch that duplicates the connections the pull chain switch makes.

Then you need to run three (or possibly four) conductors from the fan down to the switch box on the wall.

I don't see how you got 170 volts from a fan connected to a 120 volt circuit. When measuring voltages, measure from a hot conductor to neutral, not across two wires going to a switch.
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Last edited by AllanJ; 10-30-2009 at 06:58 AM.
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Old 10-30-2009, 07:23 AM   #4
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2 speed Attic fan switch


The 76v could be Phantom Voltage. As for the switch, when you run in high, it will only contact with one wire. With low, same way. If you where getting 220, then the readings are off.
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Old 10-30-2009, 10:38 PM   #5
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2 speed Attic fan switch


Lot of questions, i'll try to explain more.

There are 3 wires coming out of the motor. 1 black, 1 red, 1 white.
There is a 2 speed pull chain swith with 3 wires connected to it. There is the black power line coming into the switch labled "L", the black wire labeled "1" going out to the motor, and the red wire labeled "2" going out to the motor. The white from the motor is connected to the white wire from the power.

I hook up one side of the voltmeter to the white power line, and one to the "1" black line going to the motor. I pull the chain and it turns on high. The "1" black line reads 120V. The "2" red line reads 170V. I pull the chain again and it goes to low. the "1" black line reads 76V and the "2" red line reads 120V.

All is good.

Now, I bring in this SPDT toggle switch (ON-OFF-ON). I hook the black power line to the center. I hook the black wire from the motor that was labeled "1" on the pull chain to one side of the switch and I hook the red line that was labeled "2" on the pull chain to the other side of the switch. White from the motor stays wired to the white from the power.

I turn the toggle to one side, and the fan turns on high. 120V reads out of both the black and red wires going to the motor. I switch it to the other side, and 120V reads on both lines and still runs in high.

I doesn't make sense to me that with the pull switch hooked up, I get the 170V and the 76V. It seems to me that the pull switch is doing something different than the toggle switch.
But I have the toggle switch wired with the black "1" and red "2" getting power seperately.

It seems the motor is causing the 170V and 76V lines, but not sure why. Guess it might be a phantom voltage or something.

Anyway, let me know if that helps out.
Thanks.
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Old 10-31-2009, 10:46 AM   #6
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2 speed Attic fan switch


I am guessing that connecting the fan white (neutral) and black only (high speed) activates half of the coil and gives high speed and the far end of the other half of the coil attached to the red but not to any external live power behaves like an autotransformer measuring 170 volts to neutral.

And connecting the fan white and red only (low speed) activates the whole coil and the black not attached to any external live power acts as a center tap measuring 76 volts to neutral.

Do not simply connect up the fan based on my assumptions. First make a table of continuity (ohms approximately zero versus ohms approximately infinite) by disconnecting the switch completely and measuring across all combinations of its terminals two at a time. Repeat for each pull chain switch sequence position. This information is needed to prove where power can be safely applied to the fan.

Make another table of continuity measurements for your toggle switch, for all three positions. I am suspicious that your toggle switch is not acting like a single pole double throw switch.

Never measure with an ohmmeter or continuity meter or multimeter in the ohms position with the power on.

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Last edited by AllanJ; 10-31-2009 at 11:05 AM.
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