questions on switch box splices

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Old 10-25-09, 08:03 PM
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questions on switch box splices

As I am starting my splices to get ready for rough in, several questions came up. I never wired 3 or 4 gang switch boxes with 3 way switches and multiple circuits. So, here are some diagrams:

1. 3 gang with three 3-way switches supplied by two different circuits.


circuit 1--cable 1 comes from panel to 3 way and then exits to another 3 way via cable 2.

circuit 2--cable 3 comes from panel and in box is split to supply two 3-way switches as well as continuing unswitched to another box (cable 4). each of these 3-ways have wires going to other 3 ways in other boxes (cables 5,6)

so when connecting grounds: I would think that ALL the grounds get connected together even though they are on different circuits as I think you want everything at same potential?

when connecting neutrals:the cable 1 and 2 should be connected together, and cable 3,4,5,6 should be connected together. But cable 1,2 should NOT be connected to the rest since they are on different circuit.

case2
a four gang supplied from single circuit.


I won't go through the detail as before I think the drawing probably speaks for itself. once again, all the grounds should be connected together and due to the large number (8 cables and then 4 switches) I will have to put about 4 in nut and connect to another nut containing the other 4+pigtail the switches. Is that best way to handle it since can't get a nut over everything.

now for neutrals- should it be
cable 1 to cable 2
cable 3 to cable 4
cable 5,6,7,8 together


OR

since all on same circuit should all the neutrals be together just like the grounds?

thanks guys
 
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Old 10-26-09, 04:27 AM
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The grounds are at the same potential and tied in common. The neutrals are also at the same potential. If all are tied together,the only concern is that if in the future one circuit has a break somewhere in its neutral, its current will return via another circuit's neutral. If this added current does not amount to an overload, there's no problem. Not sure what the code says on this subject, but I've seen it done before.
 
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Old 10-26-09, 05:10 AM
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Yes all the grounds get tied together, even if on different circuits.

Only connect the neutrals together if they are on the same circuit. To do overwise could lead to overloading the neutral. This could lead to a fire as the breakers would not see the combined load on the neutral.
 
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Old 10-26-09, 06:49 AM
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Yes PC boss, that is what I was thinking about tying neutrals together from different circuits-possible overloading. I thought about 3 wire circuits. I guess if the two circuits were on different legs and both circuits were same size breaker that you wouldn't overload, but it still didn't seem like good idea.

so in my 2nd example, ALL the neutrals should be connected together just like the grounds? That is really the area I was't sure about-whether to do them 1 to 2, 3 to 4, and 5,6,7,8 together (I guess keeping the switch legs together with wire supplying the switch) OR 1,2,3,4,5,6,7,8 ALL together. does code require all together if on same circuit?
 
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Old 10-26-09, 07:08 AM
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Without tying all the neutrals together you will not have a complete circuit. For example in Case 2, splicing C1-W to C2-W does not give you the neutral path you need until it is tied to C5-w.
 
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Old 10-26-09, 11:19 AM
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confused now. C1 and C5 neutrals would be tied together at a junction box preceding this one. I tried to make a more complete diagram of the circuit. The 4 gang in upper left is the same one as the other drawing with the same numbered labels. So the neutral from C1 would go back to the 3 gang box in upper right where it would be tied (dotted line) to the neutral on other side of the switch where it then goes back to the double gang at bottom where it would be tied to the 14/2 that comes from panel. All the dotted lines I put in could be considered the neutral path. essentially the neutral is split wherever the hot is, so I would have a path back. I could see how what you say could occur maybe if using conduit and not carrying a separate neutral with each hot. But with NM I can't see how you would have to tie C1 to C5 for the circuit to function. I can see that if you somehow lost a neutral say between the one of the bottom 3 ways and the upper right 4 way (the neutral in the 14/3 wire), if you had ALL the neutrals connected as mentioned then I suppose the current would still have a path down lets say the other 14/3 wire.

Now if you say they all the neutrals have to be connected together by CODE, that is another story. I just don't see that they would need to be that way to have proper, safe functioning. the redundancy may help in the event of losing a neutral cause everything would still function since the neutral current would be flowing down one of the other cables neutral wires. But then you would have a cable with a hot wire and no neutral (since it is non-functional), which isn't allowed by code correct? and you would never know cause the current would be flowing down a different neutral and everything would still be functioning. Seems that If you wired it the way I was thinking, you would know right away if you lost a neutral and you would know exactly in what run the problem was located. Now if that occured, how you would go about using that info depends on how anal you are. you could just connect the neutrals like you say and everything would work. Or if you are anal like me, you probably try to find exact location and then repair it.

sorry pc boss, don't mean to ramble on and question you, but being meticulous and trying to fully understand things kinda goes with my profession. Don't like to just do something without understanding the concepts. Although I guess sometimes the NEC doesn't have logic which makes it a little complicated at times! I do appreciate all the help you and everyone on this board has given me.
 
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Old 10-26-09, 11:22 AM
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sorry, forgot to add the diagram. didn't know how to edit it to last post so here it is.
 
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Old 10-26-09, 11:48 AM
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I am getting confused. In the 3 gang box you say it is feed by 2 circuits. In your last diagram I only see one circuit. This same circuit appears to also feed the 4 gang box.

Could you please clarify? A box fed by 2 circuits is fed from 2 breakers, not just a continuation of feed in and feed out.

If it helps just diagram everything as a single gang box. Just use pigtails to feed power to the individual switches.
 
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Old 10-26-09, 01:56 PM
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sorry. The 3 gang box from my original post is NOT in the last diagram. That is completely separate box and NOT part of the circuit that we are now discussing. It is NOT the 3 gang that is in my last diagram. All the boxes in last diagram are fed from 1 circuit. But, The 4 gang box in last diagram is the same box from my original post and that is why I labeled it with the same numbers. hopefully that clears it up.
 
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Old 10-30-09, 06:57 PM
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pc boss, you there? do you understand now? maybe I can simplify to get to my question. suppose you had a circuit only supplying step lights and the chandilier in the steps with all the lights being controlled from the bottom and top of steps.



if you feed the first double gang box at bottom of steps with 14/2 to and then pigtailed the hot to connect to the common on each of the two three ways switches. you would also pigtail the neutral to the two 14/3 wires going to the second double gang box at top of steps. now at the top of steps you have two 14/3 cables connecting to two 3-way switches and one switch would have 14/2 going to the chandilier and the other would have 14/2 going to the first step light. so you connect up the black and reds at the two 3-way switches as usual. you are now left with 4 neutral wires(1. from 14/3 cable coming from other junction box for chandilier 2. 14/2 wire going to chandilier 3. from 14/3 wire coming from other junction box for step lights and 4. 14/2 wire going to step lights. Now the question:

I would think that you could connect the neutral 1 to 2, and 3 to 4. Or you could connect 1,2,3,4 all together. either way would work just the same. but the first option seems like a better way and here's why: lets say you lose neutral #3. if connect the first way, the step lights stop working alerting you to a problem and you can troubleshoot it-whatever caused the neutral to go out could also cause problem in hot and could be dangerous. if connect the second way, the neutral current just flows down wire #1 so everything still works and you don't ever know you lost neutral #3. so cable 3 has a hot (either red or black) but no neutral. I thought I read somewhere (reading another post about wiring a bath combo heater/light/fan unit) that is not allowed to have a hot wire within a NM cable without having a neutral also. I know that It is different in that the discussion concerning the combo heater/light/fan it was mentioned about using the neutral and relabeling it to carry a hot-but that was not allowed. this situation would simply be a broken neutral not carrying current.

So, which way is the best way to wire this situation?
 
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Old 10-30-09, 07:29 PM
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I would just splice the white of 1&2 and 3&4 at the first switch box.
 
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Old 10-30-09, 09:14 PM
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you mean at the second box? those wires are not at the first box. are you saying you would do it just like I have drawn and would NOT combine all 4 of them together?
 
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Old 10-31-09, 09:07 AM
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Splice the wires as drawn.
 
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