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Old 07-15-2009, 01:26 PM   #1
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How many wires permitted in a 4 gang box?


Hello

My code book only shows up to a 3 gang. I have a 3 x 4 x 2.5" deep box that will hold 4 light switchs. How many wires and nuts a I allowed?
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Old 07-15-2009, 01:29 PM   #2
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Metal or plastic?
What size wire, #12 or #14?
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Old 07-15-2009, 01:32 PM   #3
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Quote:
Originally Posted by ryanh View Post
Hello

My code book only shows up to a 3 gang. I have a 3 x 4 x 2.5" deep box that will hold 4 light switchs. How many wires and nuts a I allowed?
How many cubic inches is the box marked as? It is 30 cubic inches by just doing the math, but it may be listed differently.

2.00 cu. in. per #14.
2.25 cu. in. per #12
2.5 cu. in. per #10

All the grounds count only once. Switches and receptacles count as two conductors each, and wire nuts count as one each (in Canada only).
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Old 07-15-2009, 03:15 PM   #4
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Quote:
Originally Posted by ryanh View Post
I have a 3 x 4 x 2.5" deep box that will hold 4 light switchs
Are you sure on the dimensions? A 3x4 box wouldn't be a 4 gang...

What is the mfg/model of the box?
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Old 07-15-2009, 04:35 PM   #5
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On the side of the box there will be a capacity in ml. Count your wires you have, the ground and any wire that starts and ends in the box(pigtails) do not count. For each pair of marretts you count one wire(i.e 4 marretts=2 conductors, 6 marrettes=3, etc,. Each device counts as 2 wires. Divide the box ML by the wire ML and see how many your allowed to use and always round down and not up with your final answer(12.75 conductors=12 conductors)

With a 4 gang box you will have lots of room for wires, unless your planning on putting a ton of wire in there you won't have to worry about box fill.
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Old 07-15-2009, 05:23 PM   #6
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Originally Posted by darren View Post
On the side of the box there will be a capacity in ml. Count your wires you have, the ground and any wire that starts and ends in the box(pigtails) do not count. For each pair of marretts you count one wire(i.e 4 marretts=2 conductors, 6 marrettes=3, etc,. Each device counts as 2 wires. Divide the box ML by the wire ML and see how many your allowed to use and always round down and not up with your final answer(12.75 conductors=12 conductors)

With a 4 gang box you will have lots of room for wires, unless your planning on putting a ton of wire in there you won't have to worry about box fill.
Oh, so it's two wire nuts to a count. Sorry, I posted wrong.
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Old 07-15-2009, 05:47 PM   #7
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Just to add #14 take up 24.6ml, if you are useing #12(which is a waste since your lighting has to be on a 15A) your looking at 28.7ml
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Old 07-15-2009, 10:18 PM   #8
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Its a Iberville(Metal) 2 1/2 deep says 50 cu. inch

I got 6 blacks, 6 whites, 3 reds. Can't have more than 5 wires in a red marrett so i have to slip my whites and blacks and then pigtail them? So that would be 15 wires + 1 ground and 4 marretts? 18 x 2 So 36cu inch i will be using space wise?
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Old 07-16-2009, 12:44 PM   #9
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Quote:
Originally Posted by ryanh View Post
Its a Iberville(Metal) 2 1/2 deep says 50 cu. inch

I got 6 blacks, 6 whites, 3 reds. Can't have more than 5 wires in a red marrett so i have to slip my whites and blacks and then pigtail them? So that would be 15 wires + 1 ground and 4 marretts? 18 x 2 So 36cu inch i will be using space wise?
I calculated 36cu. in that is with #14 wire and no devices. Each switch counts as an addtional 2 wires (one switch would be 4cu. in). With 4 switches and the number of wires you have, you'd be right at 52cu. in; which is obviously more than the rated capacity of the box. I'd reccomend instead of pigtailing additonal wires to connect your white wires and grounds to use bigger wirenuts. If you can reduce the wirenuts to just 2 you'd be ok.

15 wires = 30cu. in
4 wire nuts/marretts = 4cu. in
All Ground wires = 2cu. in
4 switches = 16cu. in
Total = 52cu. in

Also, I just noticed this is a metal box; the wire clamps used for the wires also count as part of your box fill. I don't remember if its 1 count for all the connectors or 1 count for each connector, someone else can provide that information here (pretty sure its just like the ground wires, 1 count for all).
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Old 07-16-2009, 02:11 PM   #10
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Quote:
Originally Posted by theatretch85 View Post
I calculated 36cu. in that is with #14 wire and no devices. Each switch counts as an addtional 2 wires (one switch would be 4cu. in). With 4 switches and the number of wires you have, you'd be right at 52cu. in; which is obviously more than the rated capacity of the box. I'd reccomend instead of pigtailing additonal wires to connect your white wires and grounds to use bigger wirenuts. If you can reduce the wirenuts to just 2 you'd be ok.

15 wires = 30cu. in
4 wire nuts/marretts = 4cu. in
All Ground wires = 2cu. in
4 switches = 16cu. in
Total = 52cu. in

Also, I just noticed this is a metal box; the wire clamps used for the wires also count as part of your box fill. I don't remember if its 1 count for all the connectors or 1 count for each connector, someone else can provide that information here (pretty sure its just like the ground wires, 1 count for all).
It is one count for all the clamps, but it is only for internal clamps. External clamps (i.e. romex connectors) don't count.
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Old 07-16-2009, 04:41 PM   #11
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Going by the canadian electrical code you would take 50cubicinches/.061=819ml Take 819ml/24.6ml=33 #14 in your box

Wire-15 Conductors
Devices-8 COnductors
Marrettes-2 Conductors

This gives you a total of 25 conductors so you should be good. I would second the notion to get bigger marretts for your whites and blacks, they are called bcaps or #35 which you can find at Home Depot or Rona.
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Old 07-16-2009, 05:06 PM   #12
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So, Darren, the Canadian Code assigns less volume to a #14? I thought they were the same for both codes. Guess not. 24.6 mL is only 1.5 cubic inches. I guess they have to do something to allow room for the counted wire nuts!

And, the volume you guys have for #12 is less than the volume we use for #14!

Last edited by InPhase277; 07-16-2009 at 05:09 PM.
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Old 07-16-2009, 05:35 PM   #13
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Thats what the people who sit in the nice cushy chairs who write the code book tell us to use. You would think that they would be the same size, the wire is probably all made in the same factory except ours gets a CSA stamp on it.
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Old 07-16-2009, 11:49 PM   #14
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So in Canada its 1.5cu inch and 2.0cu inch in the US for #14 wire? Wierd

Im really pushing this box. So 3 way dimmer and a single pole switch all still count as 1 device?

Last edited by ryanh; 07-16-2009 at 11:54 PM.
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Old 07-19-2009, 07:26 PM   #15
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No in Canada it is 24(whatever that number was in my previous post)ml. Were canadian and are suppose to use metric but you show me a electrician who uses metric on a daily basis and i will buy you a beer(J/K). But converted over it is 1.5".

A device is a device, doesn't matter how big it is.
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