MC cable with aluminum ground ?

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growler

growler

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Atlanta,GA
I found some older (what appears to be MC cable) that has two copper conductors and a bare full sized #12 aluminum ground.

Anyone familiar with this sort of thing and have any idea what years it may have been installed?
 
How old? Modern MC-ap has #12 conductors with a bare #10 aluminum bonding wire.
 
Got this kind at the supply house once and took it back and told them I wanted "normal" mc. Idk, seems cheesy to me. Just my opinion. Maybe it has its purpose somewhere. Wonder where? The MC I am used to says MC-Al on the package. Aluminum sheathing with copper conductors.
 
Dr Duke said:
Got this kind at the supply house once and took it back and told them I wanted "normal" mc. Idk, seems cheesy to me. Just my opinion. Maybe it has its purpose somewhere. Wonder where? The MC I am used to says MC-Al on the package. Aluminum sheathing with copper conductors.
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That is aluminum jacketed MC cable. We're talking about an entirely different type of MC cable called MC-Ap that does not have a green insulated ground wire. It has a bare aluminum bonding conductor that is used in conjunction with the armor to form the equipment ground path in the cable.
 
infinity said:
How old? Modern MC-ap has #12 conductors with a bare #10 aluminum bonding wire.
Click to expand...

I guess that's it then I noticed the ground wire was a bit larger but thought it must be #12 to match the conductors which were #12.

They had the grounds made up with a copper bonding jumper to the box and were just useing wire nuts. It seemed wrong to be mixing copper and aluminum like that.


Tanks. I had just never seen this before. Must not be used much in this area.
 
Dr Duke said:
Got this kind at the supply house once and took it back and told them I wanted "normal" mc. Idk, seems cheesy to me. Just my opinion. Maybe it has its purpose somewhere. Wonder where? The MC I am used to says MC-Al on the package. Aluminum sheathing with copper conductors.
Click to expand...


Darn right it looks cheesy and that's what made me think it must be older even though the jacket didn't look old. I'm not sure what the purpose of this stuff is. I'll do some reading and try to find out.
 
growler said:
Darn right it looks cheesy and that's what made me think it must be older even though the jacket didn't look old. I'm not sure what the purpose of this stuff is. I'll do some reading and try to find out.
Click to expand...

Look on Southwire's web site for your research. MC-AP is used in conjunction with listed connectors (including 4s boxes with listed straps that both Raco and Steel City have. which means less make up time. Think about a dormitory or hotel....

Using listed boxes with MCAP straps and self grounding receptacles and switches. Strip the cable cut the ground off flush with the end of the sheath, push on to connector and tighten. Make up and pig out only white and black, No ground pigs, bonding the boxes, fighting with the green wire when trying to trim the receptacle.

Southwire's research shows that the ability to carry fault current is better than normal MC for what that is worth.
 
growler said:
I guess that's it then I noticed the ground wire was a bit larger but thought it must be #12 to match the conductors which were #12.

They had the grounds made up with a copper bonding jumper to the box and were just useing wire nuts. It seemed wrong to be mixing copper and aluminum like that.


Tanks. I had just never seen this before. Must not be used much in this area.
Click to expand...


It is wrong, and the installer didn't install it properly. As Strathead said, the aluminum wire is supposed to be cut off, not made up. It's just there to ensure the continuity of the jacket as the EGC.
 
Sample of this on the desk at the supply house. Appears that the aluminum is in contact with the outer sheathing and also outside the inner plastic sheath. Not sure if a special box like this is required or not.


IMG_1159.jpg
IMG_1160.jpg
 
Dr Duke said:
Sample of this on the desk at the supply house. Appears that the aluminum is in contact with the outer sheathing and also outside the inner plastic sheath. Not sure if a special box like this is required or not.
Click to expand...

It requires fittings and boxes that are listed for use with MC-Ap. So nothing special in that many boxes with MC clamps and MC cable fittings are listed for use with regular and Ap cable, but you must always check first.
 
MNSparky said:
It is wrong, and the installer didn't install it properly. As Strathead said, the aluminum wire is supposed to be cut off, not made up. It's just there to ensure the continuity of the jacket as the EGC.
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Exactly, the aluminum runner simply shunts the sheathing coils and makes the sheathing itself an approved EGC the same as AC.

Roger
 
MNSparky said:
It is wrong, and the installer didn't install it properly. As Strathead said, the aluminum wire is supposed to be cut off, not made up. It's just there to ensure the continuity of the jacket as the EGC.
Click to expand...


It's no different than the small bond wire in old AC cable. It serves the same purpose. I always cut that bond wire off, but I often see it wrapped back around the cable.
 
peter d said:
It's no different than the small bond wire in old AC cable. It serves the same purpose. I always cut that bond wire off, but I often see it wrapped back around the cable.
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Exactly. I have seen that made up like an EGC as well. :slaphead:
 
growler said:
They had the grounds made up with a copper bonding jumper to the box and were just useing wire nuts. It seemed wrong to be mixing copper and aluminum like that.
Click to expand...

If, in fact, what you saw was MC-AP (all purpose), that making up of the aluminum bonding conductor is completely wrong. When one uses an MC connector that is listed for grounding and bonding, the manufacturer's instructions say to simply cut off the Al bonding conductor where it emerges from the sheath.

The value is in a labor savings in the make up of the EGC.
 
Yea I don't know. I'm sure they just threw it together behind the desk to show options for materials and their procurement. I don't ever deal with it in my area. Just thought I'd share some photos.
 
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