Bx Cable (AC)

I just had a call where a fire alarm guy said he felt a tingle working on the fire alarms when he touched some bx in the ceiling and some EMT, safety team got involved, long story I traced it to the occupancy sensors (many on each floor of a multistory) the sensor device was in the old tiny metal switchboxes (no neutral present) and was trying to use that armor as the return path to trigger the sensor. They always had problems with the sensors failing. So I had to blank off the wall plate and put ceiling type sensors in the drop ceiling where I could get a proper neutral.
 
I would like to know what the resistance is of 100 ft of the steel armor stretched out. Then take a foot of cable and unravel it to see how much is used per foot. That would give you the worst-case scenario.

-Hal
 
Dennis Alwon said:
If you come across 12/2 BX cable that doesn't have that steel wire then we know it cannot be used as a ground. However, it is inherently already grounded and can carry a fault. The code will not allow us to use the cable as a grounding conductor. If I install a gfci and then install receptacles with a ground then am I not, inherently, using the ground?

The ground on the receptacle is connected thru the screws that attach the receptacle to the box and then to the cable. Indirectly are we creating a hazard by allowing 3 wire receptacles on a BX cable without the inner steel wire?
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I feel like this should be allowed to not have the sticker saying no equipment ground. It's the same as having old cloth reduced ground size with a gfi. The gfi will prevent a fault and the poor equipment ground will function on a surge protector and will provide some bonding throughout the system.
 
The house I'm in now was built in 1989. It's a modular. It's wired with NM and while looking inside the panel it looks like at least a couple of 14/2 home runs have a #16 EGC, don't remember ever seeing that before. I thought that went away with the old cloth stuff. So, was 14 NM ever made with a reduced EGC?

-Hal
 
hbiss said:
The house I'm in now was built in 1989. It's a modular. It's wired with NM and while looking inside the panel it looks like at least a couple of 14/2 home runs have a #16 EGC, don't remember ever seeing that before. I thought that went away with the old cloth stuff. So, was 14 NM ever made with a reduced EGC?

-Hal
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Yes in Canada it might not be American romex
 
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