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  1. #1
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    Aug 2013
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    Default Broan attic fan wiring

    I am trying to help my mom out. My dad who is now in a nursing home installed a Broam attic fan and the motor has stopped working. I turned off the breaker and went on the roof and took out the motor cutting the black, white, green wires. I now have a new motor to install, my dad told me many years ago he had a 2 speed motor so he used a 3 way switch in the hallway. The switch when in the middle is off, up is fast speed, down is slow speed. Well the motor I removed only had the black, white, green wires (no red wire) so I guess he had replaced the motor in the past to a 1 speed motor.

    When I go into the attic I see the Broam thermostat that has the wires from the switch in the hallway. The hallway switch has a black, white, ground, and a red which has me confused. I understand the black from the hallway switch goes into the input tab of the thermostat which has a BLUE quick connect then the black from the fan motor goes to the output tab on the thermostat with a quick connect. The white from the motor goes to the white from the switch in the hall. What do I do with the red wire??? The breaker does supply power to some other switches in the house also.

    I thought possibly my dad wired it so the black from the hallway switch goes into the blue quick connect that is going into the input on the thermostat in the attic, and the black from the motor goes to the output side of the thermostat and so does the red with a wire nut. The white from the switch and the white from the motor wire nut together and the 2 grounds are grounded. In the spring when the fan motor worked I could turn the switch up or down and the fan would come on but the motor only had a black, white, green wires no red. If he did it this way when the switch is up the power would go to the motor from the black wire, the switch down the power would go to the motor by the red wire that is nutted to the output side of the thermostat with the black, and the black from the motor. This would make it possible to bypass the attic thermostat and turn on the fan any time.

    I have looked at the Broam wiring diagram but am still confused because the switch works the 1 speed fan when up or down.
    Last edited by six13; 08-04-2013 at 09:12 PM.

  2. #2
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    Jun 2007
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    Default Re: Broan attic fan wiring

    If you only had a black a white and a green wire on the motor it was a single speed. He may have replaced the motor or it may have been wired so one line went to the thermostat and the other was connected to the output of the thermostat and the black from the motor. That way with the switch in one position the thermostat controlled the fan and in the other it bypassed the thermostat. I know of no thermostats that have 2 through puts so for a 2 speed fan you would need a second thermostat.

    Jack
    Last edited by JLMCDANIEL; 08-04-2013 at 11:38 PM.
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  3. #3
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    Aug 2013
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    Default Re: Broan attic fan wiring

    yes that is the way I think it needs to be wired...black from switch to input of thermostat then black from motor to output of the thermostat, white from switch and white from motor together and the 2 grounds grounded. This way the thermostat controls the on off when the switch is set to the on position.

    The problem is with the red wire, I have 3 maretts that were originally used.....no I didn't make notes when I took the maretts off....I have learned my lesson. The 3 position switch would turn the fan on up or down. The motor was a 1 speed as it only had the black, white, ground wires.

  4. #4
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    Default Re: Broan attic fan wiring

    Quote Originally Posted by JLMCDANIEL View Post
    If you only had a black a white and a green wire on the motor it was a single speed. He may have replaced the motor or it may have been wired so one line went to the thermostat and the other was connected to the output of the thermostat and the black from the motor. That way with the switch in one position the thermostat controlled the fan and in the other it bypassed the thermostat. I know of no thermostats that have 2 through puts so for a 2 speed fan you would need a second thermostat.

    Jack
    thank you for the help

    yes the motor was replaced was 1 speed the new one I have is a 1 speed also (green, white, black). You are saying on the output of the thermostat in the attic to wire nut the black, red and black from motor together? Can I combine 2 hot wires together? Since there is a 3 way switch does that mean when the switch is in the up position the black wire has the power sending to the input of the thermostat in the attic, then the output from the thermostat to the black from the motor, and the red is wire nutted with it so (3 wires under the nut red, black from output of thermostat and black from motor) would this then mean when the switch is down the red would send power to the 3 wires nutted together and since the 3 way switch is down the red, not black is energized so the motor will run any time as the thermostat is bypassed? I looked at the 3 way switch and the red wire is connected to the bottom right when looking at it when screwed back into the box.

  5. #5
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    Default Re: Broan attic fan wiring

    Bottom right means nothing to me. On a 3 way switch you have a common (on never units it is a black screw) and two travelers. The common supplies power to the switch and the travelers are energized one at a time depending on the position of the switch. With the black from the switch connected to the input of the thermostat when the switch is in the on position for the black wire it supplies power through the thermostat, with the red wire connected to the output of the thermostat along with the black from the motor the thermostat is bypassed and power is supplied to the motor via the red wire.

    jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  6. #6
    Join Date
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    Default Re: Broan attic fan wiring

    If the new motor is single-speed, the smart thing to do is wire it normally (proper colors with hot going through the thermostat) and put in a new switch accordingly. Cap any now-unused wires in the switchbox and on the end in the attic. What you should get is:

    Black from SW out to Tstat then to black at fan.
    White from inside the SWbox to White at fan
    Green from inside the SWbox to Green at fan
    Unused wires all capped.

    Whatever feeds hot to the switch now should still be OK as long as it is the same sized motor. While you're up there it would be a wise idea to wire in a remote smoke detector in case there is ever a problem with the fan. More than a few homes are lost to fires that start in the attic every year and by the time smoke reaches the indoor detectors it's usually too late to save the house. If you don't have a loop-wired alarm system, just get two detectors that can be tied together and replace the nearest one inside with a new one so that the attic detector will be heard inside the house. The wiring directions will come with the detector.

    Whole house fans and attic fans like this aren't seen as much these days but are a very economical way to help keep houses cool in the summer- another 'old tech' idea that got lost with 'new tech' AC becoming common.

    Phil

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