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Sneaky double lug


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I've seen this quite a few times recently on new houses. They have two circuits (ie, two different strands of Romex) with the hots tied together at a wire nut with another wire which then goes to the breaker. This could still lead to overloading. I've seen this on older houses where the nut is melted and black. This is not some newly allowed technique under certain conditions is it?

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I've seen this quite a few times recently on new houses. They have two circuits (ie, two different strands of Romex) with the hots tied together at a wire nut with another wire which then goes to the breaker. This could still lead to overloading. I've seen this on older houses where the nut is melted and black. This is not some newly allowed technique under certain conditions is it?

It's allowed. Always has been.

Are you thinking that wire nuts are not an appropriate splicing method? Why would a wire nut in a service panel enclosure be any worse than a wire nut in a J-box 16" away?

If you see a wire nut that's melted and black, it's because the wire nut was installed incorrectly.

- Jim in Oregon

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If you see a wire nut that's melted and black, it's because the wire nut was installed incorrectly.

What's the weakest point in a typical circuit? Meaning, if there is a jacked up breaker, and something's gonna give, what would give the most often?

A connection point. Maybe a wire nut connection, certainly a stab-back connection. Maybe a lug connection where the installer nicked the wire with his knife while stripping insulation off of it. Certainly any loose connection.

There'd have to be one heck of an overload to cause a properly installed wire nut to blacken. On the other hand, a poorly installed wire nut might reach the blackened stage with even a modest overload.

- Jim in Oregon

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The number or wires on a circuit does not cause it to be overloaded, it is what is being used on all those wires [at the same time] which determines if the circuit is overloaded or not.

For example a house may have 4 outside outlets (front, back, and each side). And 4 wires from these outlets connected to the same circuit. And you only use these for an electric lawnmower. But you only use one outlet at a time and move from outlet to outlet as you mow around the house. So the circuit is never overloaded.

Now if a family moved in which owned 4 electric lawnmowers and tried using them all at the same time, then this would exceed the capacity of the circuit (overload it), BUT the breaker would trip! So no problem so far as safety goes. That is the job of a circuit breaker, to turn off power if the amount of electricity being used exceeds the capacity of the wiring on the circuit.

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Please remind me again why double tapping at the breaker is not allowed? Is it because it could come loose?

This deals with the testing and listing requirements for the breaker. Some are listed for use with more than one conductor, others are not and can only have 1 conductor.

There are certain conditions like being the same size and material for this to be allowed.

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312.8 Enclosures for Switches or Overcurrent Devices.

Enclosures for switches or overcurrent devices shall not be

used as junction boxes, auxiliary gutters, or raceways for conductors

feeding through or tapping off to other switches or

overcurrent devices, unless adequate space for this purpose is

provided. The conductors shall not fill the wiring space at any

cross section to more than 40 percent of the cross-sectional

area of the space, and the conductors, splices, and taps shall

not fill the wiring space at any cross section to more than

75 percent of the cross-sectional area of that space.

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Hi Joe,

That's fine but it takes a whole lot of wiring and splices to fill a box to 75% of the cross sectional area of the space and I don't think that adding a splice or two, so a couple of circuits can be doubled up on a single breaker, is going to be that big a deal. If it were, I think all splices would be prohibited in panels.

ONE TEAM - ONE FIGHT!!!

Mike

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312.8 Enclosures for Switches or Overcurrent Devices.

Enclosures for switches or overcurrent devices shall not be

used as junction boxes, auxiliary gutters, or raceways for conductors

feeding through or tapping off to other switches or

overcurrent devices, unless adequate space for this purpose is

provided. The conductors shall not fill the wiring space at any

cross section to more than 40 percent of the cross-sectional

area of the space, and the conductors, splices, and taps shall

not fill the wiring space at any cross section to more than

75 percent of the cross-sectional area of that space.

Thanks for posting that, Joe, but I don't see how it relates to this particular discussion. We've discussed 312.8 many times here in the past, but it's been a while since the last time.

312.8 has nothing whatsoever to do with the original post in this thread. In that post, the conductors come into the panel, are spliced, and go to a breaker. 312.8 only addresses conductors that don't land on a switch or breaker in the panel enclosure. 312.8 deals with conductors that feed through a panel enclosure and go somewhere else.

It's perfectly acceptable to splice a wire (or wires) to make it (them) long enough to reach a breaker. If anyone wishes to argue this point, please find the appropriate NEC prohibition and post it here.

- Jim in Oregon

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