Number of wires allowed in Junction Box


Old 08-31-06, 06:03 PM
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Cool Number of wires allowed in Junction Box

ok...i hate to bring this up again but I am confused with my current wiring that the builder has done. I thought it was mentioned about a certain number of wires into a junction box. I'm re-wiring some new circuits in my basement and have found junction boxes with 4 14-2 wires connected and even one box that has 5 14-2 wires connected. They all appear to be the standard 18cu boxes.

I have several things already to question on how my house passed inspection in the first place and now this adds another question.

Can someone shed some more/new light on this topic for me?

thx as always.
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Old 08-31-06, 06:30 PM
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If these are just junction boxes and no devices then 18 would accept 4...14/2 G cables but the box would be maxed. You would have 8 conductors plus ground which would give you 9x2 = 18 cu. in. any more and you would technically be over the allowance. However if an extension ring has been used the the added volume would have to be taken into consideration. Also if any receptacles or switches are installed these have to be considered. Also any internal clamps need to be counted. So if you have 14/2 G cable and four of them enter the box you would not be allowed anything else in a 18 box volume. Here is a good article explaining the will have to copy and paste.....

Old 08-31-06, 06:35 PM
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A #14 counts as 2cu/in.

Each device in a box counts as two conductors.
ALL the grounds together cout as one.
Any and all internal cable clamps together cout as one.

So while being full at four cables, adding a device would make it overfull.
Three would be max.

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