"BX" Armored cable shield as Equipment Ground Conductor for recept. replacement ?

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"BX" Armored cable shield as Equipment Ground Conductor for recept. replacement ?

Hi all,

i recently purchased a home and an inspector indicated that there are several receptacle in violation of the NEC, because the 3 prong receptacles with ground have an open ground. After looking, they are right, there is no receptacle equip. ground connected. The problem is that there is no "green" equipment ground conductor and the cable is the old old (1950 era) BX and I assume it does not have a bonded strip like the new AC cables. It is fasted to metal outlet boxes and is fastened to the service panel which is bonded to the grounding system of the house.

After digging through the NEC it appears that I could use this BX shield as a EGC but wanted to see if I am missing something.

NEC 250.118 Lists the AC as and EGC

AC requirements then refer back to like 250.4 that states the grounding conductor has to be of low enough impedance to allow the enough fault current to trip the breaker at the panel. How can I verify or how do inspectors verify this code requirement is met?

If nothing else, I will replace the outlets with tamper resistant GFCI outlets, to satisfy receptacle replacement without proper ground.
 

Dennis Alwon

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Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
The ac cable is good for an egc if it has the bonding strip. Without that bonding strip shorts have been know to make the cable glow because of the impedance of the cable.
 
Is that code or just good practice? I have heard that as well, but am wondering if that is just due to poor/loose fittings at the panel and outlet boxes that would not allow for a complete path back to the grounding system.
 

Dennis Alwon

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Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I believe the older generation BX was not approved for a ground but I am not certain. Article 250.4(A)(5) requires the wiring to create a low impedance path so IMO the old ac/bx cable is not compliant when used an an EGC.

Maybe someone else has more info
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
Thats one of the problems with type AC cable, because you are dependant on the armor or even the bond strip, a loose locknut or a fitting not tightened properly causes loss of continuity, so you may have continuity on the first half of the circuit then loose it due to a faulty connection. If the entire house was originally wired in AC, and you only have a few receptacles that are showing no ground, that is probably your problem. You could check the locknuts for tightness, or the clamps if that type was used. Also sometimes the circuit was changed to NM cable, and the bond was not carried through.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Thats one of the problems with type AC cable, because you are dependant on the armor or even the bond strip, a loose locknut or a fitting not tightened properly causes loss of continuity, so you may have continuity on the first half of the circuit then loose it due to a faulty connection. If the entire house was originally wired in AC, and you only have a few receptacles that are showing no ground, that is probably your problem. You could check the locknuts for tightness, or the clamps if that type was used. Also sometimes the circuit was changed to NM cable, and the bond was not carried through.

Since the OP is not an electrician we do not want to get into a how to as this is not allow. Let's stick solely to the use of ac without the bonding strip as a compliant egc.
 
I understand and agree with what you guys are saying, I just wanted clarification on what "low impedance path" means. It is BX all the way from the panel to the metal outlet box and there are no grounds attached to receptacle lug as of now. I did add a ground at one receptacle to the outlet box and my little 3 prong tester shows correct, but my concern is that the inspector will say it is not to code. At this point I only want to pass inspection, if I replace the wiring at this point I have to also install AFCI protection, right? thats $$$$. I hope to replace the wiring in near future though. I'll probably just go the route of GFCI replacements at this point, I agree the BX without bonding strip is probably not a good EGC.

Maybe I should ask, how do you check if there is a bonding strip? Is that visible to the naked eye, or does it have to be listed on the shield?

Also, is there any type of test tool that can create a temporary fault form the phase to EGC at the outlet on the branch to see if the branch breaker in the panel operates?
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
The strip should be visible inside the box but we are getting to close to DIY here... I hope you have gotten enough info. as I think I need to close the thread
 
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