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Joined: Mar 2001
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Originally posted by electure:
Tom is 100% right, my thoughts were 100% wrong. AFC is about a mile from my house, so I stopped by and asked why they include the bushings in MC. The tech said that they are included as an "added measure of protection", and although not required at all, (the mylar is considered adequate), their use in encouraged. The AC cable, on the other hand, has the paper more or less as a filler to keep the ground in contact with the armor, and the paper is not deemed as a proper insulator at the termination of the armor. This leads me to wonder about the original purpose of the anti-shorts. I assumed that they protected the insulation from being punctured by crudely cut armor, something the mylar doesnt seem capable of. However, if their purpose was to prevent ground faults to the armor due to someone damaging the insulation during cutting and removing the armor,(this was more common prior to the roto-split, when hacksaws, or dikes were used) the plastic(mylar) may be adequate.
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Joined: Aug 2001
Posts: 142
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Originally posted by Redsy:
Just an opinion poll---
Why would one specify MC cable over AC(BX) cable. Since the interlocking armor of MC is not a sufficient EGC in and of itself, you must utilize the internal ground wire. AC seems easier to install due the grounding capability of the armor in conjunction with the bonding strip. It also costs less. So, why spec. MC? (I have seen the armor come loose from the (box)connector in old residential applications, so this is one good reason. Any one else).
[This message has been edited by Redsy (edited 06-08-2001).] MC is ok IMO, but i agree with you I like BX,AC cable, in fact I went to get some the other day and my supplier says, " They dont make it anymore", and I said, I will bet thats news to "AFC", so I had to take the MC instead. Later on he said he checked and said yeah they still make it. But the only kind my supplier carries is the HCF whhich is fine, but a little more expensive.
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Joined: Aug 2001
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Originally posted by electure:
Tom mentioned that MC cable doesn't have a requirement for bushings, but the 250' coils of MC I buy all come with a bag of anti-shorts. I had an inspector make me remove existing MC that was run without bushings from the connectors and install them. Isn't this covered in 110-3(b)? Tom is right, and dont ja just love AHJ, first they say your suppose to follow the manufactureers instructions, and they clearly state the 'red-head' is optional for MC because of the plastic that already exists in it.
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Anonymous
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>Is this longer return path in a fault, or leak to ground a consideration?
No.
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Joined: Jun 2001
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here in both omaha and lincoln ne you have to get written special permission to use either mc or ac. too many so called maintence types electricians (ha ) would add a circuit by using the green wire sometimes they would put a piece of black tape on it but not always. after a few shocking and smoking incidents the AHJ said no more of that stuff. To get that permission is extreamly difficult.
ed
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Anonymous
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And if they started using the bare wire in NM for a phase conductor, would the AHJ ban NM?
Why not instead require that cables have 3, 6, or 9 conductors plus the green?
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Joined: Aug 2001
Posts: 151
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Most of the EE's here that design hospital remodels/additions allow AC-ACH or ACHCI(?) to be used instead of MC with it's insulated ground. Both provide an insulated green ground as well as the jacket. They like it for the isolated ground it provides as well as the EGC (the jacket & bonding strip).
By the way, I noticed that someone attached the bonding strip from AC directly to the ground terminal bar. Here, that will get you a red tag. The bonding strip is supposed to be wrapped back against the jacket so that the clamp tightens it against the jacket. Most guys use it to also help hold the anti-short in place with a wrap across the bushing first.
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Joined: Aug 2001
Posts: 142
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Originally posted by Bill Addiss:
Tom, Electure,
Interesting,
I would always include a Bushing anyway, but it is good to know that in a pinch it can do without one.
Thanks,
Tom,
I've seen type AC cable used for Isolated grounding circuits where the red conductor was re-identified (taped green) for use as the Isolated grounding conductor. Is this kosher?
Bill AFC makes a special cable just for insulated/isolated called HCF-90, and already comes with a green grounding conductor, and with the metal sheath, there should not be any reason to remark another conductor, and I dont think remarking a red conducctor would be approved at least not in my area,but again that would be up to AHJ. The reasoning behind that, from what I have found out, is the same as conduit you cannot remark/re-identify a conducctor in conduit as you can in romex/NM, ie switch-leg. Remarking anything violates the no.6 and smaller rule.
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