Wiring new service from off-grid solar system

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Old 10-30-15, 09:59 AM
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Wiring new service from off-grid solar system

Biggest picture: I am consulting periodically w/an electrician on the wiring of my house, but want to have a better plan before my next meeting w/him.

Project big picture: I am in NY state. My solar panels will be on the roof of my garage with the remaining components on the garage interior (combiner boxes, prewired system w/inverter and charge controllers, and batteries). I will be powering my off-grid house from this.

My tentative plan: To have a 100A main breaker panel in the garage, w/an added 100A breaker from which I wire a sub panel in the house. I initially used 4/0-4/0-2/0 AL URD w/ an additional 4awg copper THHN in 2" PVC from garage to house, but have now discovered the URD cable is too big to fit into the 100A breaker panel I bought for the house. Yes, I am a complete idiot and did not check before buying.

So: My NEW tentative plan is to change out the cable to 2-2-2-4 AL SER cable between house and garage in the same conduit (rather than using split bolts to downsize the cables on each end to fit into the 100A breaker boxes).

An additional problem: My house ground is a 4awg bar copper wire attached to the rebar in my footer...but I don't have this at the garage. Will I need to add ground rod(s?) at the garage, too? Alternately I could have the main breaker at the house, and then send a wire back to the garage to power the garage...but this seems sloppier (TWO sets of wires between house and garage).

If anyone is willing, I would love feedback on my tentative plan(s), of any kind. Thank you very much!
 
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Old 10-30-15, 11:56 AM
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SER cannot be used if buried, even if in conduit.

Use lug reducers on the 4/0.

Can you post a sketch of the proposed layout?
 
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Old 10-30-15, 12:14 PM
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The garage will need a grounding electrode system, which can be two ground rods, set at least 6' apart, and bonded to the garage panel ground bus with #6 copper wire.

Agreed that you should swap the lugs instead of the cable. You already bought a better cable -- leave it there.
 
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Old 10-30-15, 07:21 PM
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Thank you for your feedback!

You both agree on not replacing the cable...and I'm glad to learn SER can't be buried. I'll try to get a diagram drawn up and re-post.

Thank you again!!!
 
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Old 11-01-15, 08:37 AM
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Here is a link to a sketch of the layout:

https://docs.google.com/presentation...it?usp=sharing

Also, my in-house circuit breaker box is in the living room (our house doesn't have a basement, and I don't have a better spot for it). The outside PVC will be coming up next to the front door. How do I use three lug reducers without the three sets of wires touching each other? Will I need to have a large additional box mounted on the outside of the house, under the LB?

Thank you so much for any ideas.
 
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Old 11-02-15, 05:21 AM
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Your link does not work.

I use an RV "off grid" with a generator and solar and curious to know your "overall picture".

Are you building in an area with no available mains power?
Will power ever be available?
What battery capacity are you planning?
Does a generator fit into your plan?
 
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Old 11-02-15, 08:19 AM
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Have you considered mounting the house main panel on the exterior? It doesn't have to open in to the house if you don't have a good location for it.
 
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Old 11-02-15, 12:04 PM
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Reposting the link

https://docs.google.com/presentation...it?usp=sharing

Trying the link again...it seems to work if you hover on it for a few seconds (the full link then pops up on the bottom of the screen, if you're using my computer. )
 

Last edited by algstewart; 11-02-15 at 12:53 PM.
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Old 11-02-15, 12:22 PM
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Maybe you can put a disconnect box on the outside of the house and make the wire type change there, with a short run into the house. Just make sure the breakers are sized for the smaller wire.
 
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Old 11-02-15, 03:00 PM
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Would I need an additional disconnect where I use wire reducers?

I'm hoping to find a reducer that can reduce 3 wires next to each other, and then to put that (rubber and electrically taped) into an exterior box, or into the LB if that would work. ? Thank you for your help.
 
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Old 11-02-15, 03:05 PM
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We could connect to the grid, but it would cost a lot to do so and would also be a legal hassle (our deed has a right-of-way but not specifically for utilities...). We're at the end of a road, so the utility isn't required to connect us and it would be on our dime (more than a dime). We're doing solar as an alternative the making a multi-thousand dollar investment to connect to the grid.

Batteries: We're planning to start with about 400 AH in batteries, which we may expand, and we may also add a generator but are not starting with one unless we have to.
 
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Old 11-02-15, 03:23 PM
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You could use three Polaris connectors in an exterior box. The LB would be a bit too small to make those connections.
 
 

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