Splitting power source for multiple switches

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  #1  
Old 04-11-07, 07:26 AM
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Splitting power source for multiple switches

Quick question regarding if this is permissable.

I currently have a double switch box with two different power sources for two different lights. I want to swap the double out for a triple and have one power source feed 2 lines. I know that the load can easily accomodate 100W on either line, so is it permissable to power two switches by using pigtails?

What I would do is take the black/ hot from the power source, add 2 pigtails, and then have the pigtails feed the switches. I would just then cap all of the white lines together.. but I was slightly concerned over overcrowding in the box.

I was going to use a metal triple switch box which seems roomy enough.. but just want to get some experts to see if that's OK...

Thanks
 
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Old 04-11-07, 07:54 AM
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If you are going from a double gang box to a triple gang box and adding one switch and one cable you should be okay. However, to be safe, you need to do a box fill calculation. What size are the cables? What size is the box ? How many cables and what makeup are they?

Now just to be safe, what do these circuits presently serve? Not just what these two switches control, but what else is on the circuits? And what do you plan to power with this new switch?

And one final comment. The statement, "I would just then cap all of the white lines together" needs clarification. The white neutral wires need to remain isolated for each circuit. However, the ground wires all get connected together, regardless of the circuit they originate from.
 
  #3  
Old 04-11-07, 08:34 AM
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Thanks for the reply Bob.

I haven't opened the existing box yet, so I'm making some assumptions, but I feel 99% confident that this is how it's currently set up.

My existing double box has 2 power sources and 2 lines going to the following: 1 controls the light right inside the back door. The other controls the outside lights on my porch. Both are different circuits - confirmed because they were on two different circuit breakers in the panel.

The one that controls the light inside the back door has several other lights, ie, kitchen, hallway, etc... given my calcs, another 60-100W light would not be too much... but I prefer to use the other because it does not have very many items at all. The second circuit controls 2 - 200 watt halogen exterior lights and 3 duplex outlets. All lines at use 14/2 wiring.

Per my calcs, I would have 2 cables in and 2 out for each switch now - not counting the ground - it would be 8 in total... what the new calc would be is beying me... do I count a pigtail? The new box is 3 X 2 X 3 1/2 - so I'm not just how many are allowed.

With regards to my statement about capping all whites - forgive me - I should be more careful to make sure that I really explain things like this better. I know not to combine separate circuit neutrals.... what I meant was that I would take the white/neutrals from the lines going out from the two new switches to the white/neutral from the power source - thus, it's all the same circuit.
 
  #4  
Old 04-11-07, 08:58 AM
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You do not count the pigtails. You also count all the ground wires as one wire. So if you really do have two cables entering the box bringing power in, and then three leaving you will have 11 wires to count, plus three switches. You will be fine with your three gang box.

However, before you get ahead of yourself, open the box and look at it. If both of the existing switches are wired as switch loops, then you do not have power at the box and you cannot add a switch and run to a new light from it.

If one of the circuits is wired as a switch loop and the other not, then the non-switch loop would have to be used. If both are not wires ad switch loops then either can be used.

As for the existing circuits. Where are those receptacles on the one circuit? Depending on where they are you will not be able to use that circuit for a new light.

The new box is NOT 3 X 2 X 3 1/2, at least not if it is a triple gang box. One of those numbers is wrong.
 
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