What Kind Of Cable Was This?

[kwired]

Many get bent out of shape about it but from personal experience it will trip a circuit breaker if you get a fault. Do you really think the dinky aluminum strip does much?

That aluminum strip is not the EGC, it supplements the spiral type sheath by shorting between turns. It doesn't even need to be terminated, it's only purpose is to sit outside any fillers within the cable and to be in contact with the sheath to assist in lowering resistance of the sheath.

Take a one foot piece of cable sheath and unwind it. It will be much longer than one foot, now imagine how much longer a 100 foot run is if you unwind the sheath of it. That is what you potentially can have for a return path if not many of each turn doesn't have incidental contact to shorten the path. Is not that an overcurrent device won't trip at all, is about having as low of impedance path as possible. There has been cases or signs of this old AC cable heating up when subject to fault current.

 

[Eddie702]

@kwired
Agree 100%. My point is this old wiring method was allowed and so was K & T and other old, outdated wiring methods. Then they were not allowed to be installed any longer, but I have never seen a case where you were forced to remove an old wiring method that was still in service. And I have never seen proof that the older BX was not allowed as an equipment ground even though we all know it is an inferior one.

As far as the aluminum strip I fold it back over the red head to hold the RH in place and wrap it around the armor before installing the connector.

But as you mentioned this is not required and it can be simply cut off.

 

[kwired]

@kwired
Agree 100%. My point is this old wiring method was allowed and so was K & T and other old, outdated wiring methods. Then they were not allowed to be installed any longer, but I have never seen a case where you were forced to remove an old wiring method that was still in service. And I have never seen proof that the older BX was not allowed as an equipment ground even though we all know it is an inferior one.

As far as the aluminum strip I fold it back over the red head to hold the RH in place and wrap it around the armor before installing the connector.

But as you mentioned this is not required and it can be simply cut off.

The older AC cable with no bonding strip, as I believe was mentioned earlier in this thread, was used at a time when installing EGC's wasn't a common thing. The bonding strip was added around the time when GEC's were being required for everything. Again existing equipment has generally been allowed to remain as is if it was code compliant at the time of install.

I wouldn't be against GFCI protection on old AC cable, it will trip at low fault current level, certainly this armor can carry a few milliamps of fault current and likely trip faster than if there were significant enough resistance to lengthen trip time of a standard breaker. I think it should be a design decision and not necessarily code requirement though.

 

[hbiss]

The older AC cable with no bonding strip, as I believe was mentioned earlier in this thread, was used at a time when installing EGC's wasn't a common thing.

Correct. I don't think grounding receptacles were even invented yet because there was nothing that had a grounding plug on it that would use it. About the only things you had to worry about was metal wall plates and fixtures possibly becoming energized which the grounded armor would take care of by blowing the fuse.

At around the late 50's I believe the first appliances that had grounding plugs were washing machines that extended the EGC to the utilization equipment. That made those grounding adapters infamous, or they just cut the ground pin off.

-Hal

 

[hbiss]

Thinking some more about those washing machines of back then- I remember cold water washing machine hoses having a grounding conductor built into them. They were marked to only be used on the cold.

-Hal

 

[Jraef]

The NEC began requiring EGC wires in NM cable back in 1974, and at the same time required a ground bonding strip IN the armor in AC (Armored Cable) OR a ground wire, which became MC.

The term AC for Armored Cable goes all the way back to the beginning, existing alongside K&T, but being more expensive, was uncommon in residential. The first BRAND of AC was released in the first decade of the 1900s, called “Greenfield” cable, a name that is still used in some circles today. Sprague Electric of New York, the mfr, was bought by GE in the 20s and GE experimented with different ways of manufacturing Greenfield. They settled on two types, AX and BX, and yes, the “X” stood for experimental. BX won out in market popularity (I don’t know the differences). But technically, BX is still a brand name (like Romex), it was/is still called AC if it has a ground bonding strip embedded in the metal corrugations, and MC if there is a separate ground WIRE in it. I believe you can buy “BX” brand both ways, so it no longer denotes which TYPE of cable it is.

 

[Eddie702]

The NEC began requiring EGC wires in NM cable back in 1974, and at the same time required a ground bonding strip IN the armor in AC (Armored Cable) OR a ground wire, which became MC.

The term AC for Armored Cable goes all the way back to the beginning, existing alongside K&T, but being more expensive, was uncommon in residential. The first BRAND of AC was released in the first decade of the 1900s, called “Greenfield” cable, a name that is still used in some circles today. Sprague Electric of New York, the mfr, was bought by GE in the 20s and GE experimented with different ways of manufacturing Greenfield. They settled on two types, AX and BX, and yes, the “X” stood for experimental. BX won out in market popularity (I don’t know the differences). But technically, BX is still a brand name (like Romex), it was/is still called AC if it has a ground bonding strip embedded in the metal corrugations, and MC if there is a separate ground WIRE in it. I believe you can buy “BX” brand both ways, so it no longer denotes which TYPE of cable it is.

I don't know but I had read that the bonding strip in the BX started around 1959 when grounded receptacles where required. As far as NM goes I saw undersized grounds in the 60. I assume grounds in NM was required at the same time as BX

 

[VirutalElectrician]

NM cable from 60's through 80's had a tougher sheath as a general rule than many the cables made since ~2000. Today's cable you have to be careful pulling across the floor or over top of the bottom chord of a truss rafter during installations, if you rub against some metal object it may tear the sheath much easier than it would have most those older cables.

When I take stuff to the dump, I like to go dig through the copper scrap that people drop off. Last week I found some nice examples of Essex and Etcoflex. The house my dad built in 74 was all wired with Etcoflex, so I was happy to see that. It was about 10' of 12/3. The paper and PVC sheeth are so much heavier. It almost looks like 8/3 wire of today.