So, we're buying a home with original aluminum wiring (minus the kitchen, which was remodeled). The service panels are a mess - service entrance directly through exterior wall and into detached garage main panel board, then 150 amp feed to sub panel in the attached garage, which supplies the house. The panels are old, rickety, have no cable clamps or protectors at the knock-outs, and the circuits are overloaded, including 12 ga Al wire on 20 amp breakers.

We've completed a 500 sq ft basement finish in our current house (selling), including all the electrical, under permit and to code. I will likely sub out some of the electrical, especially pulling new copper NM throughout the house and adding some circuits. I already contacted the AHJ and clarified they are using NEC 2008 and as the homeowner, I can complete the work as long as I pull a permit. I'm considering wiring everything in both garages and replacing the service panel and sub. I'm not sure about the exact size of the cable currently feeding the sub, but I do know that the ground wire isn't connected in either panel, but it is there and it's BIG.

One of my big questions is to clarify what size cable I should be using to feed the 200 amp sub from the 200 amp main. I plan to use Siemens PL panels with copper buss and a 200 amp QNH breaker to feed the sub. I plan to use SER rather than running wire through conduit because some of the run goes up to and around the attic, then back down the wall and underground. I think trying to lay conduit for all of that will be a nightmare.

Also, if I replace the service entrance cable (and the meter socket) from the meter (it has a lateral feed, so not touching that), what size does that need to be.

Thanks in advance

 

Ampacity Charts

Looks like 3/0 will handle 200A, but I'd recommend 4/0 just to be safe.

 

From what I have read, it looks like aluminum SER 3-wire 4/0 with a 2/0 ground for the feeder and 4/0 SE to connect the meter socket to the main panel. Anyone agree or have other recommendations? On the ampacity charts, which temperature rating am I supposed to be referencing? Is it the same for the service entrance as for the feeder to the sub?

I'm hesitant to move in before replacing all the Al wiring, but maybe I'm being a little crazy. After all, it's been in the house for 40+ years and not caused a major problem (yet). Would anyone else move in with plans to re-wire in the first few weeks, or wait to re-wire first? I pulled some switch plate covers - some of the boxes appear overstuffed and none have Alumicon connectors or the like. Oh, and none of the ground wires are connected to anything, just floating around in the boxes.

 

4/0 is what is in the NEC

 

Also note that SER is not to go underground.

You should pick your electrician and pay for some consulting time because you have a lot of issues to deal with.

 

You need the help of a licensed electrician not a do it yerself forum.

As for your question above...... moving is stressful enough, I couldn't see how its even possible to embark on such an undertaking in addition to that. I wish you luck brother.

 

For 200 amp dwelling service use either 4/0 aluminum or 2/0 copper. Read 310.15(B)(6) in the NEC and the accompanying table.

I wouldn't move in till all the old aluminum wiring has been properly replaced. From the description of the electrical system you have provided, it's a wonder that house is still standing.

 

It will be easier to rewire without needing to work around furniture etc.