Old BX Cable

[Ravenvalor]

Hello,

To what extent can one handle the old BX cable (1930's) era? I have to change some panels out and am worried about disturbing the cable. I have seen the insulation fall right off of the conductors before.

Thank You,

 

[Sahib]

Such old wiring with brittle insulation may show good insulation resistance. But still it is a serious fire hazard. Because a little vibration could make the insulation leave the conductors making them exposed. It is high time such cables were changed.

 

[petersonra]

Any 80+ YO wiring is in a class of things best changed out as opposed to trying to reuse it if you are forced to mess with it.

I realize that the end user may not wish to spend the money to replace the panels and the wiring, but I am not sure you are improving things by leaving that old BX in place. Wiring of that age is likely to be damaged in the process of replacing the panels.

You may well end up with a worse situation on your hands afterward than what is there now.

besides that, is the AHJ going to allow you to just change out the panels and not do something about the BX?

wiring of that era is just not up to snuff.

 

[Ravenvalor]

Thanks for the replies. I have to admit that your sentiments have been my policies for years now. 75% of the time I tell the customer that the only way that I will touch it is if I am removing it.

 

[Dennis Alwon]

If the wire has been at a light fixture it usually is brittle but otherwise it is not so bad. It is always a bit tricky working with it-- good luck. I have taken a piece of thhn insulation off of a piece of wire and slid it over the affected areas on the bx conductors.

 

[jumper]

This thread reminds me I have been partly blessed, always got replace any wiring predating 1971 NEC and I have never even touched K and T.

 

[dhalleron]

I've seen it both ways. Sometimes the insulation was only dried out and brittle at light fixtures that had high wattage lamps in them over the years. Usually insulation was fine at junction boxes and panels. Sometimes the wax was still on the insulation and it was flexible.

Other times, every place I looked at the insulation, it was dried out and brittle.

Most of the time it was only bad at the fixture boxes.

 

[jumper]

I've seen it both ways. Sometimes the insulation was only dried out and brittle at light fixtures that had high wattage lamps in them over the years. Usually insulation was fine at junction boxes and panels. Sometimes the wax was still on the insulation and it was flexible.

Other times, every place I looked at the insulation, it was dried out and brittle.

Most of the time it was only bad at the fixture boxes.

You are like me, still forget that new fangled luminaire term.:thumbsup:

I give up on even trying.

 

[GoldDigger]

I've seen it both ways. Sometimes the insulation was only dried out and brittle at light fixtures that had high wattage lamps in them over the years. Usually insulation was fine at junction boxes and panels. Sometimes the wax was still on the insulation and it was flexible.

Other times, every place I looked at the insulation, it was dried out and brittle.

Most of the time it was only bad at the fixture boxes.

Just out of curiosity and hypothetically, if you did not have to disturb it and it was properly installed in the first place, would you consider the old BX or K&T to be more dangerous?

 

[jumper]

Just out of curiosity and hypothetically, if you did not have to disturb it and it was properly installed in the first place, would you consider the old BX or K&T to be more dangerous?

Strange enough I would probably like properly installed K and T myself.

Better craftsmen probably and not a false sense of a good EGC.

 

[GoldDigger]

Strange enough I would probably like properly installed K and T myself.

Better craftsmen probably and not a false sense of a good EGC.

I would also add positive separation between the wires, rather than depending on insulation inside a vibrating tube.
I might worry about K&T if I had a water leak above it though. If they really used the Tube part, even that would not be too bad.

 

[jumper]

I would also add positive separation between the wires, rather than depending on insulation inside a vibrating tube.
I might worry about K&T if I had a water leak above it though. If they really used the Tube part, even that would not be too bad.

Pretty sure the tube is a hole through the porcelain insulator/knob to secure the conductor, no insulation is removed.

 

[GoldDigger]

Pretty sure the tube is a hole through the porcelain insulator/knob to secure the conductor, no insulation is removed.

I was referring to two things:
1. In BX, the insulated wires are installed packed tightly inside a metal tube.
2. In K & T each wire should be run separately through a porcelain tube wherever it goes through a hole in wood members, so that if the wood gets wet there will not be any fault current even if the insulation is compromised over time. It is not securing it so much as it is insulating it. The knob, on the other hand, is a standoff insulator that may be nailed or screwed to the surface of a framing member and very definitely holds the wire in place too.

The situation is different for the two methods if you expect the wire insulation to eventually fail.

 

[jumper]

I was referring to two things:
1. In BX, the insulated wires are installed packed tightly inside a metal tube.
2. In K & T each wire should be run separately through a porcelain tube wherever it goes through a hole in wood members, so that if the wood gets wet there will not be any fault current even if the insulation is compromised over time. It is not securing it so much as it is insulating it. The knob, on the other hand, is a standoff insulator that may be nailed or screwed to the surface of a framing member and very definitely holds the wire in place too.

The situation is different for the two methods if you expect the wire insulation to eventually fail.

Oh, that tube!!:slaphead:

 

[petersonra]

just remember, even if the wiring is old and decrepit, if you touch it you pretty much own it.

 

[PetrosA]

Rubber insulated wires in BX will generally only be brittle where they were exposed to air - so boxes and panels, although sometimes high temperatures or humidity can affect them as well (attics, basements). It's likely they will be nice and flexible further in where they didn't get as much oxygen. If that's the case and the customer really can't afford to rewire the whole place, you could shorten them and land them in a JB or trough above/below the new panels and run new wiring to them. It's not always an easy call to make, though. The last customer I had with a Craftsman home wired in BX was a few months ago. My "cost effective" suggestion was to install GFCI breakers on all those circuits with BX. This would allow the jacket to perform a draining function for things like computers and UPSs while the GFCI breaker would be protecting the wire in case of a ground fault.

 

[petersonra]

This would allow the jacket to perform a draining function for things like computers and UPSs while the GFCI breaker would be protecting the wire in case of a ground fault.

what the heck is a "draining function"?

 

[dhalleron]

You are like me, still forget that new fangled luminaire term.:thumbsup:

I give up on even trying.

Who in their right mind sat on a code panel and decided to call light fixtures luminaires? Anyone in the field ever call it that before it was in the code?

I also sometimes say plugs instead of receptacles. And I am not about to learn the metric sizes of conduit.

 

[GoldDigger]

what the heck is a "draining function"?

I think it is a wimpy bonding function good only for draining of static charge.

 

[GoldDigger]

I also sometimes say plugs instead of receptacles.

Just so you don't call them outlets. (Which they also are. Unless they are connector bodies.):roll: