Alum ground on branch ckt

[Matt Fellman]

I haven't seen this before.... the building is a new (2007) hi-rise residential building. The grounds in the panel are aluminum and the hot/neutrals are copper.

The "cable" appears to be metallic sheathed so I'm thinking the only actual aluminum ground "wires" are from the panel entry point to the bus?

The gromets are particularly fascinating and not like anything I've ever seen. They look to me to be a type of clamp that accept the ground wire and the metallic cable but without being able to see most of it I'm really just speculating.

Anyhow, I thought I'd share and see if anyone has run across this setup before?

[paul hardy]

You acually have a product simular to this the aluminum wire is designed to be cut at the cable connector.


http://www.afcweb.com/pdf/afc_1001_mc_q_Installation.pdf

[Roger Frazee]

What you have there is MCap cable (all purpose). It has a aluminum grounding conductor bonded to the outer metal sheath so that the outer sheath will comply with NEC 250.118 10(a) as a grounding path for fault current. this allows you to not have to take the time to terminate an equipment ground wire to a terminal bus. Since it is an aluminum equipment ground wire it will be one size larger than the copper conductors.

It is designated all purpose because it will comply with any installation/application where you would be allowed to use AC cable.

What is a little strange is you normally do not extend the al ground to the grounding terminal bus as you are showing in the picture.... but it isn't doing any harm installing it like that. And it may be the contractor had specs.that required him to do so. It would be a little more or step above what would be required. The idea is to save time and money by cutting off the ground at the fitting so you do not have to take the time to terminate it on the grounding bus. It is all about money savings which I generally have to chuckle a bit as it really makes little difference. I suppose if you terminated several panels in a days time you might save 30 minutes or so.

The fitting you see I think is a raco 2800 (not real sure) but these fittings must be listed for MCap and the box they come in and the fitting will be marked MCia and ul listed. They attach to the cable sheath with a screw then snap into the knockout hole. As you can see they also have a plastic bushing. The conductors are wrapped in a nylon sheath if I remember correctly and the aluminum ground is outside that sheath.

If you go to the Southwire website they should have lots of information on the technical support link for this type MCap cable and usually they will have videos on installation and discussions on the NEC compliances with code references.

[John Arnold]

You acually have a product simular to this the aluminum wire is designed to be cut at the cable connector.


http://www.afcweb.com/pdf/afc_1001_mc_q_Installation.pdf

Good info, Paul. Thanks!

[Matt Fellman]

Thanks everyone... great info