1940 house wired BX cable, romex

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zappy

zappy

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CA.
Fixing up code violations from another electrician. He ran romex to a BX cable box. I was going to remove the romex, and run MC cable to the box.

Will MC cable land in a BX cable box correctly? Do they make BX cable any more?

Was it allowed at one time to bury j-boxes inside the wall? I found one and it looks like it's been there a while. I'm thinkin the answer is no.

Thank you for your help.
 
zappy said:
Fixing up code violations from another electrician. He ran romex to a BX cable box. I was going to remove the romex, and run MC cable to the box.

Will MC cable land in a BX cable box correctly?
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Yes. If you happen to come across a set-screw connector, remember that it cannot be used for aluminum sheaths.
Do they make BX cable any more?
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Yes, both steel and aluminum sheaths. The 1940's AC/BX had a lower quality grounding sheath that 1959 and after, generally, so be aware of that.
Was it allowed at one time to bury j-boxes inside the wall? I found one and it looks like it's been there a while. I'm thinkin the answer is no.

Thank you for your help.
Click to expand...

You're right. Also, the older conductors were fatter so 12/3 BX, for instance, may not fit in a connector that will accomodate a newer 12/3.
 
zappy said:
Fixing up code violations from another electrician. He ran romex to a BX cable box. I was going to remove the romex, and run MC cable to the box.

Will MC cable land in a BX cable box correctly? Do they make BX cable any more?.
Click to expand...
Most new boxes such as Raco 518 are rated for MC/BX. If your box is the same age as the house it would not have a MC rating. The problem you normally have with older boxes is that they not have the cu.in. capacity required by today's Code. If it is a single entry MC with one device the old box may be adequate.
zappy said:
Was it allowed at one time to bury j-boxes inside the wall? I found one and it looks like it's been there a while. I'm thinkin the answer is no.

Thank you for your help.
Click to expand...
I can't recall that the Code permitted covered boxes at any time.
 
LarryFine said:
Why is the NM summarily a violation?
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Well, I don't know, but my guess is that a BX exists in an internal clamp, and someone brought a NM cable through the second opening, so to make it right, either the fished-in NM goes, or the stapled-in-wall BX is replaced.
zappy said:
Fixing up code violations from another electrician. He ran romex to a BX cable box...
Click to expand...

Augie had a good point, though. The original box is probably 2-1/2 in deep or so, so any added cable will exceed the cu in allowance. When that cable has a wire-type EGC, even more so.

Best to replace the box, or add a beautiful Wiremold extension :roll:.
 
Replacing is not the only option, as others have said. If the box is not deep enough then replace the box. 3 1/2" boxes usually have a ko for a regular connector. Replacing the nm with MC is unnecessary and not cost effective.
 
Volta said:
Yes. If you happen to come across a set-screw connector, remember that it cannot be used for aluminum sheaths.

Could you please elaborate on this point? I am always confused by the different types of AC and MC connectors. There are connectors that are combo MC/NM, saddle type, set screw type and maybe others. Are there issues to consider when using these connectors?
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Greg1707 said:
Could you please elaborate on this point? I am always confused by the different types of AC and MC connectors. There are connectors that are combo MC/NM, saddle type, set screw type and maybe others. Are there issues to consider when using these connectors?
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Can't locate the text quickly, maybe it is a manufacturer's instruction, but it comes from the fact that a set-screw would likely penetrate the aluminum sheath rather than press on it.
 
This is one style of set screwcable connector not for use with aluminum jacketed cable.

Set-Screw%20Connectors.jpg


http://www.arlcatalog.com/Flex/Set-Screw Connectors2.htm


Here is another style

Set-Screw%20Connectors%20Steel.jpg


http://www.arlcatalog.com/Flex/Set-Screw Connectors.htm
 
I often find that the old BX steel cable has conductors in worse shape than knob/tube and for sure worse than NM. I wonder if the steel somehow reacted with the insulation or if it heated up too much in the wrap. Most BX I attempt to rework tries to crack right where I score and break the steel. It's nearly impossible to cut with a rotosplitter. I score it or cut 1 spiral with a hacksaw, similar to greenfield and gently twist/bend it to snap. That little bit usually disturbs the conductors. I replace BX as much as possible.

I'd heard you could order steel wrap MC or AC. Haven't seen any around that I'm aware of. Anyone here using it out and around?

Boxes: Gotta respect the old time electricians who mostly had octagon boxes, had to solder and tape splices. I've seen 4 BX's into a 3 1/2 octagon box. 8 conductors with bulky taped splices and they still managed to get a cover on it all. I guess code allowed that many wires back in the day. I see it enough in the kind of places I'm sure people didn't jackleg their work.
 
jmellc said:
I often find that the old BX steel cable has conductors in worse shape than knob/tube and for sure worse than NM. I wonder if the steel somehow reacted with the insulation or if it heated up too much in the wrap. Most BX I attempt to rework tries to crack right where I score and break the steel. It's nearly impossible to cut with a rotosplitter. I score it or cut 1 spiral with a hacksaw, similar to greenfield and gently twist/bend it to snap. That little bit usually disturbs the conductors. I replace BX as much as possible.
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Yeah, it's pretty delicate these days. But I do find that the undisturbed section are in good shape. The exposed wires after 60 years behind overlamped fixtures, well that's another story :roll:.
I'd heard you could order steel wrap MC or AC. Haven't seen any around that I'm aware of. Anyone here using it out and around?
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Here is a link. I haven't been using any, though.
Boxes: Gotta respect the old time electricians who mostly had octagon boxes, had to solder and tape splices. I've seen 4 BX's into a 3 1/2 octagon box. 8 conductors with bulky taped splices and they still managed to get a cover on it all. I guess code allowed that many wires back in the day. I see it enough in the kind of places I'm sure people didn't jackleg their work.
Click to expand...

Yup, I carry extensions for those little octagons, they sure could cram some wire in there!
 
Volta said:
Well, I don't know, but my guess is that a BX exists in an internal clamp, and someone brought a NM cable through the second opening, so to make it right, either the fished-in NM goes, or the stapled-in-wall BX is replaced.


Augie had a good point, though. The original box is probably 2-1/2 in deep or so, so any added cable will exceed the cu in allowance. When that cable has a wire-type EGC, even more so.

Best to replace the box, or add a beautiful Wiremold extension :roll:.
Click to expand...

Yep. There's BX under existing clamps. The inspector said there's no bushing for the NM in the box.
 
Why would someone need to use steel MC or AC cable? More protection? Whats the difference between AC and MC and BX cable?
 
zappy said:
Why would someone need to use steel MC or AC cable? More protection? Whats the difference between AC and MC and BX cable?
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I could see using it where subject to mild physical damage. Don't recall code on it, don't have book handy. But I've hammered on pieces of BX and barely dented it. Aluminum sheath is easily mashed and pulled apart.

AC carries a bonding wire constant contact with the sheath. Cut it to 2 or 3 inches and wrap back around the sheath before putting on a connector. That is the grounding. MC carries standard green ground wire.
 
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