Old type Armored cable

[monkey]

When upgrading a service on an old home wired with the old armored cable (no internal bonding strip) I usually cut the AC in the attic right where it goes down to the old fuse panel so I can move the old circuits to the new service panel outside. This requires a j-box in the attic to continue on to the new panel with NM. I normally ground the j-box with the grounding wire from the romex, but this creates another problem. There is continuity thru the armor to the metal j-box then on to the panel via the romex. Does this violate 333-19 & 250-2(d)(99 NEC)? Should I cut the grounding conductor off the romex to break the path? I have heard of fires being started during a ground fault due to the high resistance path on the unbonded armor not allowing enough current to reach the OCPD. It?s hard to determine which is the lesser of 2 evils. Also the armor was continuous to the old fusebox for many years before. I am curious how others deal with this. Thanks for any help on this.

Brian

 

[david]

Re: Old type Armored cable

370-4. Metal Boxes
All metal boxes shall be grounded in accordance with the provisions of Article 250.

The old style BX dose not have a sheath that is an effective equipment ground and cannot be relied upon as an effective fault clearing path. The metal box that you used at the junction point between the new NM cable and the old BX wiring method is required to be grounded. So you cannot simply cut the equipment ground you must use it to ground the junction box.

I am adding that you also need to use box connectors that are approved for the cable you are securing to the junction box.

[ February 29, 2004, 09:42 PM: Message edited by: david ]

 

[monkey]

Re: Old type Armored cable

Well I guess I should have done a search before posting. I found a good 4 page thread on the subject. As a result I have decided to keep the grounding path intact and use GFCI breakers on these circuits. I will, of course still welcome any more input.
Thanks, Brian

 

[ron]

Re: Old type Armored cable

Again keep the grounding path intact, as mentioned.
If you will offer protection for the circuit at the circuit breaker, purchased with your "dime", then consider AFCI instead of GFCI. Most if not all AFCI also give GFCI protection.

 

[hurk27]

Re: Old type Armored cable

Monkey
For one 333-19 is for AC type cable. What you have is older BX cable. Lighting circuits are not required to be grounded in existing systems but if you replace the receptacles with a grounding type then you would have to use the required methods in the "2002" 406.3(D) 1-3
"Or in the 1999" 210-7(D)

I agree the AFCI's would be a better choice but if there are multi-wire circuits you will have to get the two-pole type. But as you can see in 406.3 The NEC will require GFCI'S on the receptacles as the BX can not be concidered as a ground. So putting a AFCI will still require a GFCI or a combo unit AFCI/GFCI.

 

[caosesvida]

Re: Old type Armored cable

Is bx "older style" which I guess is in lots of older pre 60's installations, considered as not having a grounding path? It is a two wire system and the armor is only for protection.

 

[tonyi]

Re: Old type Armored cable

BX won't always have low enough resistance to clear a fault if someone used the armor for gnd. It would show up as continuity on a simple tester though and that probably fakes some people out.

IMO, the only safe way to deal with this stuff (short of ripping it out) is AF or GF protection. Then the armor will won't have enough current on it to heat up and start a fire if something faults to the armor - the device trips first