Wish they would just stop making type AC ( BX ) cable. Way too.many times have came across old BX that was installed in damp basements, unheated damp buildings etc where the steel jacket was rusted creating holes in jacket. I never had any faith with the flimsy bare #18 gauge wire providing a dependable!e ground. Never got to unwind one foot of armored #14 or 12 jacket from BX but guessing it would be over 6' in length so a 100' run of BX might consist of 600' of steel jacket. Would be nice to measure the ground resistance of 100' of steel jacket BX & MC cable and compare the difference.
Correct way to extend BX cable
- Thread starter Rob2025
- Start date
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
The thin wire is only there to provide a turn-to-turn shunt, not an end-to-end pathway.
Its purpose is to minimize the effects of exactly what you're describing.
Eddy_Current
Member
- Location
- Canada
We cannot get MC here. Our AC90 has an aluminum sheath, bare copper bond conductor, insulated circuit conductors and paper. No little metal strip. The paper isn’t around each insulated conductor like the images in post #19, rather it is loosely wrapped around all the conductors separating them from the sheath.
I only see MC if it comes attached to equipment that is purchased from the US.
Eddie702
Licensed Electrician
- Location
- Western Massachusetts
- Occupation
- Electrician
People complain about AC cable and the ground path it does or doesn't provide. It's been around since the 20s. Not the most popular or used wiring method now but it seems to work.
pipe_bender
Senior Member
- Location
- Boston
- Occupation
- Electrician
I was working on a hospital a few years back and we had to use this special MC cable that had the AC cable 'bonding strip' and a Green EGC.
As you probably know hospitals and medical buildings require a redundant EGC, OK but that means the MC sheath is not considered a EGC like EMT or AC cable it, so why only add the bonding strip back to Hospital MC ?
When I asked was told if you nick it just right the armor on regular MC will just glow red hot. It made me wonder why they don't always put the bonding strip in MC as I imagine they think the armor is just unlikely to become energized. But if it does it seems it wont clear a fault, the fault would need to travel back thru the spiral armor to the last metal box.
OldBroadcastTech
Senior Member
- Location
- Western IL
- Occupation
- Retired Broadcast Technician
It's a Great White North thing. Kinda like Colour-coding wires, eh ?
jmellc
Senior Member
- Location
- Durham, NC
- Occupation
- Facility Maintenance Tech. Licensed Electrician
I've seen a few existing ones here & there. Seemed to hold OK. Never saw any new ones on shelf.
hbiss
EC, New York NEC: 2017
- Location
- Little Falls, New York NEC: 2017
- Occupation
- EC
HFC (Health Facilities Cable) is not MC. It's AC and that's why it uses the armor as a redundant EGC. Under no circumstances is the armor of MC cable allowed to be used as an EGC.
When you asked??
All you have to do is nick it?? I just answered your question above as to why there is no bonding strip in MC . Because the armor does not carry any fault current. The green EGC is for that.Then there is MCAP which does have a full size bare EGC under the armor because there is no green ground. It is like AC in that the armor is the EGC.
-Hal