Wiring attic exhaust fan

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  #1  
Old 08-26-09, 12:56 PM
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Wiring attic exhaust fan

Hi all, new to the forums.

I just had my roof re-shingled and in doing it they installed an exhaust fan and left the thermostat hanging. I need to wire it.

Here's my setup in the attic:

--a large white sheathed wire running up the rafter to an outlet with two receptacles. These receptacles are always hot.

--Coming off the side of that outlet is a single wire going to a light bulb and it is controlled by a switch on the wall in my living space.


The span from the outlet to the thermostat of the fan is about 20 feet.


Here are my questions:

1) What sized wire should I use?

2) How do I tap into the outlet and use that power source without eliminating my light?


I have minor electrical experience but can get the job done if the process is explained to me clearly enough. Don't necessarily assume I know the jargon or implied shortcuts or else I will go 'huh?' .


Thanks,
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  #2  
Old 08-26-09, 01:05 PM
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1) What sized wire should I use?
#14 if 15a breaker. #12 if 20 amp breaker.
2) How do I tap into the outlet and use that power source without eliminating my light?
Assuming the receptacle box is large enough for extra wires, and it probably is, Determine which cable to the receptacle is power in. Disconnect this cable from the receptacle. Connect the black and white of this cable to the fan cable. plus a pigtail at each wire connection. Connect the pigtails to the receptacle.
 
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Old 08-26-09, 01:05 PM
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Originally Posted by newarcher View Post
1) What sized wire should I use?
The same as the cable on the existing circuit. It will be either 12/2 or 14/2, and it's usually printed on the outer jacket of the cable. If you really can't tell, then 12/2 is the safe bet for a 20A circuit or 14/2 for a 15A circuit.

2) How do I tap into the outlet and use that power source without eliminating my light?
Should be quite simple -- black to brass, white to silver, bare to ground. You may need some wirenuts, perhaps a ground screw, probably some cable staples matched to the wire size, perhaps a box connector. I can't say for sure without seeing exactly what you have.

It would help if you could snap a photo of the inside of the receptacle box so we can see what wires you have, the type of box, etc. You can upload the photo to a sharing site like photobucket or flickr and post a link here.
 
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Old 08-26-09, 01:08 PM
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Welcome to the forum.

The wire size will depend on the size of the breaker protecting that circuit. A fifteen amp circuit will need #14 ga wire, a 20 amp circuit would need #12.

The easiest way to get power may be from the receptacle. Can you tell us the connections behind the fixture in the attic?
 
  #5  
Old 08-27-09, 05:18 AM
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Revisiting this after being away yesterday.

I will get the pictures for you this afternoon, thank you guys and gals for the help.

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  #6  
Old 08-27-09, 01:08 PM
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Sorry fellahs, not intentionally dragging my feet on this. I dragged my big butt up into the scorching attic and found out I was all wrong. I turned the camera on and the stupid thing immediately went to "Change Batteries" and turned off....no warning.

Anyway, I was wrong on the setup.....here is what I have:

First, I have 14/2 wire.

The primary wire runs up to the light fixture, not the outlet....which explains why the light can be turned off from the switch in the house.

From the light, runs a 14/2 wire to the two plug outlet. I checked the wiring inside that outlet and found that the wiring must be attached on the back of the outlet. The two bronze, two silver attachment points, & ground on the side of the outlet are not used.

This leaves me really confused as to how I can control the light from the switch in the house without also controlling the outlet receptacles. The outlets both stay hot even with the light off.

So as I understand it, I should be able to bring the wire in from the wired fan and then just attach the black wire to the bronze, the white wire to the silver, and the ground to the ground (all on the side)....right? [edited to add: I haven't used the outlet yet in 5 years of living here so I guess that I could just eliminate the outlet all together and replace the wire running to the outlet with the wire running to the fan. Given that I don't need the outlet, it would simply things a lot].

I will get some pics up as soon as my batteries charge.


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Last edited by newarcher; 08-27-09 at 01:34 PM.
  #7  
Old 08-27-09, 01:51 PM
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So as I understand it, I should be able to bring the wire in from the wired fan and then just attach the black wire to the bronze, the white wire to the silver,
Yes.
and the ground to the ground (all on the side)....right?
Actually they all need to be twisted together and a pigtail added that goes to the screw on the receptacle. If the box is metal a second pigtail goes to the box.
[edited to add: I haven't used the outlet yet in 5 years of living here so I guess that I could just eliminate the outlet all together and replace the wire running to the outlet with the wire running to the fan.
No. It is good to have a receptacle and local code may require it. NEC requires it if you have HVAC equipment in the attic.
I checked the wiring inside that outlet and found that the wiring must be attached on the back of the outlet.
Backstabbs should be moved to the screws. They are less reliable and you just know if it fails it will be on the hottest day of the year.
 
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Old 08-27-09, 02:04 PM
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Originally Posted by newarcher View Post
Sorry fellahs, not intentionally dragging my feet on this. I dragged my big butt up into the scorching attic and found out I was all wrong. I turned the camera on and the stupid thing immediately went to "Change Batteries" and turned off....no warning.

Anyway, I was wrong on the setup.....here is what I have:

First, I have 14/2 wire.

The primary wire runs up to the light fixture, not the outlet....which explains why the light can be turned off from the switch in the house.

From the light, runs a 14/2 wire to the two plug outlet. I checked the wiring inside that outlet and found that the wiring must be attached on the back of the outlet. The two bronze, two silver attachment points, & ground on the side of the outlet are not used.

This leaves me really confused as to how I can control the light from the switch in the house without also controlling the outlet receptacles. The outlets both stay hot even with the light off.

So as I understand it, I should be able to bring the wire in from the wired fan and then just attach the black wire to the bronze, the white wire to the silver, and the ground to the ground (all on the side)....right? [edited to add: I haven't used the outlet yet in 5 years of living here so I guess that I could just eliminate the outlet all together and replace the wire running to the outlet with the wire running to the fan. Given that I don't need the outlet, it would simply things a lot].

I will get some pics up as soon as my batteries charge.


New
Your wiring if I'm understanding correctly is like this diagram. If you want you can add a switch to turn the fan on and off for any quick maintenance. This will allow you to still have control of the light. I don't believe you mentioned a switch other than the thermostat.

 
  #9  
Old 08-27-09, 02:06 PM
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All right, humor me while I translate your instructions into idiot speak (my idiocy that is)....sorry, I am VERY literal:

Steps I need to do:

1) Wire up to the thermostat on the fan
2) Staple the new wire to the rafters back to the outlet box.
3) Kill the power to the whole house (extra safety)
4) Pull the outlet out of the box and undo the backstabbing
5) (from the wire coming off the light to the outlet box), attach the black wire to the bronze screw, white to the silver screw, and leave the ground hanging for step 7.
6) Bring the wire from the fan into the outlet box....attach the black to the other bronze screw, white to the other silver screw, and leave the ground hanging for step 7.

7) merge both ground wires together with a third ground wire and attach all three to the side of the outlet. Take the tag end of the extra ground wire and attach it to the metal outlet box.


Sound right?


Thanks again!

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  #10  
Old 08-27-09, 02:10 PM
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Originally Posted by Bruto View Post
Your wiring if I'm understanding correctly is like this diagram. If you want you can add a switch to turn the fan on and off for any quick maintenance. This will allow you to still have control of the light. I don't believe you mentioned a switch other than the thermostat.


I BELIEVE this is correct.....I never thought of the power source and the switch being separate entities. I assumed the power came through the switch completely.

If I wanted to add a switch, what's that process? Just putting the switch in the middle of the line running to the fan?

I usually kill the power to the entire house when I work on anything electric....learned the hard way after running into an attic switch that turned off the furnace...not the attic fan (my old house). After getting up off my knees I changed my methods going forward!

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  #11  
Old 08-27-09, 02:21 PM
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If your going to mess with the wiring of the fan then turn the circuit breaker off to the branch circuit not the whole house. If your just wanting to take a look at the fan and do a little maintenance then the switch should be fine to isolate the fan. And you will be able to see cause you still have the light. After all it is under your control and would not likely be energized by someone else turning on the switch. The breaker would more likely be energized since you can't control who turns it on without a lockout on it.
 
  #12  
Old 08-27-09, 02:23 PM
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If I wanted to add a switch, what's that process? Just putting the switch in the middle of the line running to the fan?
Yep that's what you would do
 
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