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I need to run a new service cable from the house to the garage. I have a 200amp panel in the house and I am going to use the old 100amp panel from the house in the garage. I will be putting the full 100amps out there feeding from a 100amp breaker in the main panel. I will be using aluminum wire and if I remember correctly the guy that helped me with the wires in the house said I should be using 2-2-2-4 for it.

I am not that worried about what the code/local laws are, but I need things to be safe. I have read where the ground and neutrals should be separated in the sub panel(buss bars physically separated) , but I am not seeing how feeding a sub panel would be any different than if you were just running a 220v outlet off of the main panel. The garage is metallicly connected to the house with a copper water line if it makes a difference since I have read some things mentioning it. Any help would be appreciated.

The difference is this.... the "ground" has to be at same voltage potential as the ground.. the 4 gauge wire that ties the ground at the sub panel to the ground at the main panel is not supposed to carry any current. The "neutral" wire (one of the 2 guage wires) between the subpanel and the main panel may be carring current... perhaps even as much as 100 amps on 100 amp subpanel. Any wire that carries current has a voltage drop from one end to the other. The voltage drop of a 2 guage wire with 100amps current flowing through it is a little over a half a volt per foot. So, If the sub panel is 100' from the main panel, than their might be a 5 volt difference between the "ground" and the "neutral".

The copper water line will be at the same ground voltage as the ground or neutral at the main panel... If no separate ground wire were used for the sub panel, than their would be a 5 volt difference between the copper water line and the "ground" at the sub panel (because it is tied to the neutral)....

First things first, some of this might be over my head so questions I ask are only for information not arguing and some info may need to be repeated . In the panel at the house the grounds and neutrals are all connected to the same busses. 2 hot legs and one bare wire run down from the meter base, bare wire goes to the ground/neutral buss. I then have a separate ground wire that runs from the ground/netural buss to my water main that comes into the house. From what I see the grounds and neutrals are not separated from, each other.

Now to the sub panel. Are you saying that the grounds and neutrals do indeed need to be on separate busses in that panel and then running back to the main panel? What is the difference when they get to the main panel and essentially go to the same thing or do each of those wires not get hooked up to the ground/neutral buss that is in there? Also does the water line I have running out to the garage make any sort of difference or not? Thanks.

I am no electrician by any means as to houses, but I seem to remember that more than a few mobile home fires were attributed to aluminum wiring being lesser in load carrying ability. I would think if a specification were set, the actual wire type shouldn't matter as long as the spec were met.

Yes/No??

I would think the circuit loading/over loading would cause the problems, but a correctly designed/rated breaker should have stopped the power if load exceeded spec limits.

Yes/No??

I remember hearing stories about aluminum wiring loading causing the wires inside those structures that were not secured to the framing causing a vibrating sound form their over loading.

Possible/Not possible??

Dave, aluminum wiring is not the problem, but corrosion in the joints where aluminum meets other metals is. There are special procedures and anti-corrosion materials and compounds needed to avoid trouble, and they're specified in the National Electric Code.

Keep the return separate from the ground on all panels except the entrance panel. There are tons of reasons for doing this, and not all are obvious, but the NEC is good to follow, even if you don't plan to get the work inspected. In general, the ground wire is there as an independent safety wire, and if you fail to keep it separate, its safety contribution is lost.

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If it surges, that's normal, upshift.

2-2-2-4 is rated for 100 amps for a service entrance but only 90 amps for a branch circuit/sub panel and a number of inspectors will require a 90 amp breaker. But it reads like there will be no inspection. What Jim says in above post is correct. Be sure all connection points are rated for copper and aluminum connectors and use an anti corrosion for aluminum connectors and you will be safe.

Voltage drop due to the conductor length in the branch also needs to be considered.

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1973 RD350, 1979 RD400F, 1984 RZ350, 2014 Suzuki Vstrom 1000
CHRIS AND JEFF ARE THE MEN

I thought aluminum wire was outlawed here in the states years ago, is that true?

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Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........

It violates code in much if not all of Canada now...but as Jim said, it's the connections that are the problem, not the actual wire. I assume that' why this job is not being inspected? It is scary not to have the work approved as you will not have valid insurance.

Thanks, Jim, makes percent sense on the connections and corrosion. I do think I heard that aluminum wiring was disallowed in new mobile home manufacturing a few years ago, though.

My copy of the NEC is the 1996 version, and I know it's changed a little, but I think you can still use aluminum wiring in U.S. homes for single application circuits rated for 30 amps or more. This would apply to things like electric ranges and clothes dryers. Mobile homes can have their own special rules, so I would expect you could be right about that.

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If it surges, that's normal, upshift.