Does anyone happen to know when the code started requiring a certain length of wire at j-boxes? I'm dealing with existing cloth bx and changing fixtures/devices and trying to apply a practical approach.
Oldest NEC I have in the office is 1975.
300.14 is in there with 6"
Someone else here has older NECs in their archives & they may have some input.
In old work, from a practical sense, it is what it is.
Talk to your AHJ to see what remediation they like there.
Typically you can splice on the additional conductor necessary to make the box usable but that is not defined in the code.
Ditto to what Greg said above as to splicing on extension pieces.
An issue that pops up with replacement fixtures is the temp rating of the 'old' conductors. There is an available sleeve that goes over single conductors that is acceptable to some AHJs.
In this case I am the AHJ. And yes the temp rating is a highly correlated concern. Any links to those sleeves?
I do not have a link; hopefully someone does. The sleeves come with a few different fixtures that I have seen.
One that sticks to memory is Ruud Lighting, with the wallpack HID fixtures. You may find it thru McMaster Carr.
http://www.3m.com/market/industrial/ceramics/materials/braided_sleevings.htmlI use this in the industrial dryers I work on. Most well stocked electronic stores carry it as well as some HVAC suppy stores
West:
Thanks for that link. Based on the temp ratings...it looks $$$$
Not to change directions here but are you allowing grounding type receptacles? I have often wondered about this, as the BX provides a grounding path, although questionable and not actually listed for grounding. What do you do?
BigB:
Best answer I can offer is:
"320.108 Equipment Grounding Conductor. Type AC cable
shall provide an adequate path for fault current as required
by 250.4(A)(5) or (B)(4) to act as an equipment grounding
conductor."
From the '11 NEC
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.
Reno:
Perhaps the interpertation at the time was that the pigtails satisfied the 6", as it allows the device to be removed & replaced. As I said earlier, I have been there with the old boxes, clipped corners, and also the pancake fixture boxes with multiple BX within. All were neatly arranged, some soldered & friction taped. The fixture canopies back then were IMHO large. Touch those neat conductors, and you were sorry!!
IMHO, it takes a talented electrician to touch/work on any of the 'old' wiring. Quite a few of the 'young' guys have never seen the things that us 'seasoned' sparkies have. We should be thankful that the 'old' ways (for some part) are no longer commonplace.
One of the courses at the vo-tech is 'Basic Wiring' and box fill, jacket length, free conductor length is taught. The instructor uses metal device boxes 3-1/2" deep, and NM. I am amazed at the difficulty some of the students have with these basic trade practices, and code compliance.
John,
You are correct about the large over sized canopies that they used to use around here. Some years ago, I sent in pictures of those old boxes, rosettes, and crow foot boxes. Those old timers would lay that wire down real neat, solder and tape, then cover the whole thing with those huge canopies. Just because the code box said that you should have 6" of free conductors, doesn't always mean that it was there.