ECN Forum Forums Code Related Discussion NEC & other Code issues Length of free conductors at outlets

I think he is talking about the BX before the bonding strip.

I did do a grounding study on an old WWII era building to see how well it held up and the ECOS tester said the cable armor ground was <1 ohm under a load for every circuit I tested. I am not sure what the rise time would be tho and I think that is what the bond strip is for.

I've caom accross some different 'varities' of BX/AC over the years, specially in the 'inner city' areas of Newark, East Orange, etc.

One that sticks out in my mind was the thickest armour, tightly wound interlocked, and it was a bugger to cut back.

The bonding strip was famous around here as a 'red head holder'. I'm curious as to the amperage on a fault that the bonding strip could handle.

The bonding strip was supposed to eliminate the inductive effect of the spiral armor. It shunts it out so the current path is very short from wrap to wrap.
I understood that it was really just the leading edge of the fault that they were dealing with

The stuff we see here in the southwest never has the bonding strip (at least I have never seen any with it). It is mostly from the 30's to the 40's. We almost always remove or abandon it, since the rubber inside is brittle and it is in horrible shape especially at the fixtures. I was under the impression this type is not listed for grounding and I always wondered about installing grounding type receptacles on it. We are just finishing up a house now that was full of it. All the outside walls had it channeled into the brick an plastered over.

I have a few old NEC books 1962 states under 300-14 you need 6" of free wire at each outlet and switch.

1957 NEC book Article 300, sec3006 also requires 6" of wire.

1947 NEC also Art. 300 sec 3006 wants 6" of free wire.

1933 NEC Article 5 section 512 still requires 6" of free wire.

Those are the oldest books that I have. I do have one put out by the city of Elizabeth here in NJ that is from 1922.

John,

That old BX you were talking about. Was it 2 separate pieces of curled sheathing intertwined around the conductors.
I remember seeing something like that around here and it was tough to cut. It was very thick steel and springy because there were 2 strips wrapped around each other and around the conductors. If I ever see a piece of that again,
I will try to get and save a piece of it.

Harold:

Yes, that sounds like what I remember!!

Something's wrong here.

I have seen far too many professional installations where not only was there virtually NO free conductor, there simply isn't room in the boxes for it.

I'm thinking of the old boxes with the 'clipped' corners, and the wires are soldered together in the back of the box. You have the barely enough room for the wires and an old device- and a GFCI completely fills the box (or just barely doesn't even fit in). There's not even room for you to use wire nuts.

There must have been a change- perhaps not requiring the wires coming into the box to have the free length, or considering the pigtails as the free length.

Reno:
I've been there over the years.

A solution we used was a 'Wiremold' extension box to make it do-able and somewhat compliant to retrofit a 'new' device (think GFI)

As to the old days with the solder and friction tape, I for one say thankfully that practice is long gone.

Someone with a library of old NECs may find IF there was a change.

I appreciate Harold's efforts in checking older editions, but something is missing. He cites several editions that were current at the very time the short / absent free conductors were the standard practice.

Perhaps the remaining pigtails were considered as meeting the requirement?

It's not a matter of 'if' there was a change; rather, it's a question of identifying what that change was.

Again, I infer this from the simple fact that the boxes used at the time simply are not large enough. You simply cannot fit both wire and device into them.