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01-10-2011, 09:19 PM   #1
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## one or two sources?

Hi. On a recent electrical project I successfully installed three way switches for a a ceiling light in a walk through closet with one switch at each entrance, and I felt secure in understanding the logic of the configuration. And the project after that I successfully wired a double gangbox with one source for two single switches which included a through source to another independently
operated light and switch and I understood the logic of this configuration.

However, I'm still new at this and I need someone to point me in the correct direction on this next project: Light at bottom of stairs, light at top of stairs; both will be operated independently and each will have a set of three way switches, one at the bottom and one at the top of the stairs. The three way switches will be housed in pairs together in double gangboxes at top and bottom of stairs. Because of limited depth, I'll be working with 25 cubic inch boxes (11/12). I'll be working with 12/2 and of course 12/3 wire.

QUESTION: Can I power these two independently operating sets of three way switches with one in source wire, or do I need, even if from same circuit line, two different source wires, one for each independent 3-way switch configuration.

Just telling me that it is possible to use the one source wire will give me the impetus to maybe figure it out; but any further advice on the configuration would be gladly gleaned!

Gee, afterthought here: Surely it can be powered by one source.......do I just do an extra pigtail at the first entrance of source to feed the two different three way switch circuits?

Thanks,
James

Last edited by DiegoJames; 01-10-2011 at 09:29 PM. Reason: realized more about the question

01-10-2011, 09:31 PM   #2
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Yes it can be done rather easily.

 01-10-2011, 09:33 PM #3 Electrical Supplier   Join Date: Jun 2010 Location: Dayton, OH Posts: 205 Rewards Points: 150 First off 14 ga is more than adequate for lighting and much easier to wire (if you are on a 15a branch circuit that is). Put that aside and ill answer your question. A three way works like such: Line (power in)-------switch 1=======switch 2-------Load (light) Got the concept of a three way? If so you just put the load end at one box and the line at the other and go out from there to your light. Just wire nut the incoming line wire to pigtails off of the two switches common screws. Just remember to keep the other switches commons apart and tied to their respective light. Dont forget to carry your neutrals with your 3way circuit at all times! This means you will have to make 2 runs of 3 wire w/ground between the boxes and one 2 wire w/ground for each light. (it makes it easier for any future expansion and makes it code compliant) __________________ "Do it right the first time and avoid duplication of effort" Your AHJ/Inspectors ALWAYS have the final say on ANY electrical code issue. If in doubt, contact a licensed, experienced, reputable electrician to perform the work.
 The Following User Says Thank You to LyonsElecSupply For This Useful Post: DiegoJames (01-10-2011)

 01-10-2011, 09:47 PM #4 Master Electrician   Join Date: Mar 2010 Location: Indiana Posts: 3,747 Rewards Points: 3,750 Off the top of my head there are at least four different ways to do 3 way configurations.
01-10-2011, 09:53 PM   #5
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## Thanks

(Yeah, is a 20 amp breaker and I'm using 12 wire.)

Yes! now I'm seeing the light. And I understand having to do the separate runs of 3-wire for each of the independent lights and 3-way switch sets. (I'm excited! - but always moving with a studied approach and making sure I understand function and follow through of hot, neutral, and ground.)

Thanks.

01-10-2011, 09:57 PM   #6
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Quote:
 Originally Posted by brric Off the top of my head there are at least four different ways to do 3 way configurations.
I know of 3 and one of which is Illegal per NEC.

California and Standard are the two usually used, but California is not common and will confuse most people.
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"Do it right the first time and avoid duplication of effort"

Your AHJ/Inspectors ALWAYS have the final say on ANY electrical code issue.
If in doubt, contact a licensed, experienced, reputable electrician to perform the work.

01-11-2011, 01:38 AM   #7
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Quote:
 Originally Posted by LyonsElecSupply I know of 3 and one of which is Illegal per NEC. California and Standard are the two usually used, but California is not common and will confuse most people.
I know allready know 6 diffrent way but the latter two I will not mention in here due the safety issue on shell socket. { common with K&T era }

Merci,
Marc
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The answer will be based on NEC ( National Electrical code ) or CEC ( Cananda Electrical code ) or ECF ( Electrique Code France )

 01-11-2011, 06:14 AM #8 A "Handy Husband"     Join Date: Feb 2007 Location: South Carolina Low Country Posts: 7,292 Rewards Points: 4,142 Using a 25 cu in box, you will exceed the fill limits for the box.. Each switch box will have (2)12-3 cables (6 wires) plus 1 supply 12-2 cable (2 wires) or 2 load cables 2-2 (4 wires) plus a ground(1 wire) plus 2 devices (4 wires). (You will also have to add another conductor if the box has internal clamps.) That's 6+4+1+4 = 15 x 2.25 = 33.75 cu in (for the box with the 2 load cables. 1 less conductor (2.25 cu in) for the box with 1 supply cable). Here is an easy to understand reference: http://ecmweb.com/nec/code-basics/el..._calculations/ Use a 3 gang box with a 2 gang plaster ring. __________________ Location: Coastal South Carolina
 01-11-2011, 08:35 AM #9 Member     Join Date: Mar 2005 Location: Welland, Ontario Posts: 12,599 Rewards Points: 11,990 Blog Entries: 11 One power source will be fine for both circuits. Wire each light as a completely indepenent three way circuit. Without seeing the actual lay out I think I would wire the top light out of the top switch box and the lower light out of the lower switch box. Put the power into whichever switch is closest to the feed.
01-11-2011, 09:40 AM   #10
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The neutral (to the white wire coming out of the light fixture or to the lamp socket) must not go through a switch. This immediately invalidates some concoctions of 3 way switch setups including what was called the "California" method to me.

In all correct versions, the best way is to run a 3 wire cable non-stop between the two switches in a 3 way setup. (If there are two 3 way switches in the same box for two lights, each one needs its own 3 wire cable to its mate.)

Usually you have better results with the feed (supply) cable to one switch location and the light connected to the other because this puts fewer wires into any given box and you might not have to change out a smaller box for a larger one.

Normally, one source wire can power all the switches in a multi gang box but it is permissible for more than one source wire to come into the box. When separate sources power 3 way switches in one location and all of their mates are in one other location, separate n eutrals must go to the second location and not be combined there. Each neutral must go to all of and only the lights that the corresponding hot wire went to..

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Last edited by AllanJ; 01-11-2011 at 09:54 AM.

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