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Anyone use AC anymore? #1924 06/08/01 12:15 PM
Joined: Mar 2001
Posts: 2,056
R
Redsy Offline OP
Member
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).]

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Re: Anyone use AC anymore? #1925 06/08/01 07:54 PM
Joined: Jan 2001
Posts: 1,044
Tom Offline
Member
I'm a big fan of equipment grounding conductors other than the raceway or cable armor. You have already pointed out the major drawback, the connector may be loose & you lose the equipment ground.

As for other advantages, all you have to do is compare "uses permitted" 333-3 & 334-3.

The only additional advantages I can think of are that MC doesn't require the use of bushings, & AC, to the best of my knowledge, is not available with an aluminum jacket. A roll of steel jacketed AC is really heavy.

Tom

[This message has been edited by Tom (edited 06-08-2001).]


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Re: Anyone use AC anymore? #1926 06/08/01 08:50 PM
Joined: Oct 2000
Posts: 5,389
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sparky Offline
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If you unravel the outer jacket, it may be 5 times the length of the interior conductors. Is this longer return path in a fault, or leak to ground a consideration?

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Re: Anyone use AC anymore? #1927 06/08/01 09:29 PM
Joined: Oct 2000
Posts: 3,961
Bill Addiss Offline
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Tom,

AC cable is readily available in "Lite" versions. See:
http://www.afcweb.com/table2.html

For Places of Assembly I've only used MC cable but I notice that AC would be permitted if an insulated Grounding wire was included in the cable. Do they mean a Green wire? Or could you reidentify one wire (such as the red) with green tape?

Bill


Bill
Re: Anyone use AC anymore? #1928 06/09/01 09:49 PM
Joined: Dec 2000
Posts: 4,283
electure Offline
Member
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)?

Re: Anyone use AC anymore? #1929 06/10/01 09:08 AM
Joined: Jan 2001
Posts: 1,044
Tom Offline
Member
Electure,

Your inspector dropped the ball. There is no requirement in Article 334 regarding the use of bushings. 110-3(b) does not apply because there are no written instructions attached to the roll of cable requireing installing the bushings and there is nothing in the listing of MC cable that requires their use either. You should consider sending that inspector a invoice for your time.

Bill, the insulated equipment ground you mentioned would have to meet the marking standard in 250-119, taping a conductor #6 & smaller would be prohibited. Unless, of course, the installation complied with 250-119(b), which would not apply in most cases. AC lite may be available, but I still like the insulated equipment ground in MC.


Tom


Few things are harder to put up with than the annoyance of a good example.
Re: Anyone use AC anymore? #1930 06/12/01 08:03 AM
Joined: Dec 2000
Posts: 4,283
electure Offline
Member
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.

Re: Anyone use AC anymore? #1931 06/12/01 08:48 AM
Joined: Oct 2000
Posts: 3,961
Bill Addiss Offline
Member
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


Bill
Re: Anyone use AC anymore? #1932 06/12/01 05:05 PM
Joined: Jan 2001
Posts: 1,044
Tom Offline
Member
Bill,

I've seen this done plenty of times myself.
If it is #6 & smaller, it technically does not meet the marking requirements. I think this would be fairly low on the hazard scale, but you never know.

Tom


Few things are harder to put up with than the annoyance of a good example.
Re: Anyone use AC anymore? #1933 06/12/01 06:41 PM
Joined: Oct 2000
Posts: 3,961
Bill Addiss Offline
Member
Tom,

Agreed, not a priority #1 hazard. I try to be as correct as possible to avoid as many infractions as I can.

Thanks,

Bill


Bill
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