Wiring to add exhaust fan in bathroom

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  #1  
Old 10-31-05, 09:39 AM
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Wiring to add exhaust fan in bathroom

I want to add a exhaust fan/light combo in my bathroom. There is one wall switch that connects to a light fixture on the side wall over the sink.
The electrical is old knob/tube and there is only 2 wires going to the switch, very thick wires insulated in a cloth type material.

Can I tap into the switch for power, I have attic access and could probably locate where the wires drop down to the switch.

Thanks.
 
  #2  
Old 10-31-05, 10:13 AM
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No, you cannot tap into the switch for power. You need to tap power at the light fixture.

Let us know how you want to control this new fixture. Will the existing switch control it? Will you add one switch that will control both fan and light? Will you add two switches so that you can control them separately?

Then let us know all the wiring and connections at the existing light fixture.
 
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Old 10-31-05, 10:30 AM
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Whaever is the least difficult of these two options:


1) Control existing light, control fan/light combo independently - 2 control switch.

2) Control fan, control light, control existing light independent of others - 3 control switch.
 
  #4  
Old 10-31-05, 12:21 PM
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Fewer switches are easier than more switches, but both are possible. So you need at least one new switch. You have these options:
  • Replace the single switch with a duplex switch and keep it in the same single-gang box.
  • Expand the box to a double-gang box and install two single switches, or perhaps one single switch and a duplex switch.
  • Expand the box to a triple-gang box and install three single switches.
  • Install a triplex switch in the single-gang box (although this makes getting all the wires in the box very difficult).
As far as cabling, you will need to do one of the following:
  • Replace the two wires between the existing light fixture and the switch box with a 3-wire cable. Then run a two-wire cable (for two switches) or a 3-wire cable (for three switches) from the switch box to the new fan/light combo.
  • Add a two-wire cable from the existing light to the new fan/light combo. Then run a two-wire cable (for two switches) or a 3-wire cable (for three switches) from the new fan/light to the switches.
None of this stuff is all that hard, but all require some uncomfortable time in the attic. You need to be in the attic anyway to install the ducting for the exhaust fan. Make sure the ducting extends all the way to the outside (through the roof or out the eave). Under no circumstances should you just end the duct in the attic.
 
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Old 10-31-05, 03:35 PM
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Ok. This is the option I will install:

Replace the single switch with a duplex switch and keep it in the same single-gang box.


If I do this are these the correct steps?


Replace the two wires between the existing light fixture and the switch box with a 3-wire cable. Then run a two-wire cable (for two switches) from the switch box to the new fan/light combo.

Add a two-wire cable from the existing light to the new fan/light combo. Then run a two-wire cable from the new fan/light to the switches.
 
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Old 11-01-05, 07:34 AM
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That's too much. Do either one, not both.
 
  #7  
Old 11-01-05, 09:24 AM
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Thanks, I'm going to give it a shot this weekend. I'll let you know how it turns out.
 
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Old 11-01-05, 10:20 AM
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We haven't gone over the connections yet, so post back with the connections you see now once you get it all opened up. For heavens sake, don't just disconnect everything without recording it and then come ask how to put it back together.
 
  #9  
Old 11-01-05, 05:33 PM
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OK. I plan to take digital photos just in case.
 
 

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