electrical sanity check

[va72mlibu]

I've been poring over posts and research and I think I've got all my bases covered for installing the electrical run from my main panel to my new detached garage. I wanted to post my plans and get a sanity check from the group before I purchased anything. Plan thus far:
125A breaker in my 200A main panel. 1/0 CU THWN in conduit from the main panel through the basement ceiling running 25' across the house and exiting ~6' above grade. 2" PVC LB exiting the brick exterior into Sch 80 PVC down into a 24" trench. 90 degree sweep into ~175' of schedule 40 PVC across my entire yard in a 24" trench. Enters the garage via a 90 degree sweep that's fully grouted into the garage foundation. 125A main breaker panel in the garage. Anyone see any potential red flags?

 

[MrSurly]

Red flag #1. 125 amps? Why so much? You could save on wire a bit by installing 100 or even 90A equipment. What sort of actual loading do you anticipate?

 

[va72mlibu]

I'm trying to future proof, expecting within the next 10 years to have 2 electric vehicles. Additionally, I can get a screaming deal on 1/0 CU THWN ($1.46/ft).

 

[pattenp]

Conduit only needs 18" of cover, not 24".
Aluminum is alot cheaper.

 

[va72mlibu]

Conduit only needs 18" of cover, not 24".

OK, I misread that part of the code. I will have to rent a trencher either way. Is there any downside to going down 24". Is the caution tape mandatory?

 

[va72mlibu]

Aluminum is alot cheaper.

For that length (even for 100A service), my calculations work out to needing 2/0 Aluminum. I've read that can be tough to pull and then a bear to bend into the main panel. Not the case?

 

[Bert_]

For that length (even for 100A service), my calculations work out to needing 2/0 Aluminum. I've read that can be tough to pull and then a bear to bend into the main panel. Not the case?

2/0 will pull just as easy. Aluminum is lighter and easier to bend than copper, even though you need a bigger wire.

Plus 2/0 XHHW is 65¢ /foot.

24" is a good depth. No sense doing the minimum unless your digging by hand. I usually trench 2-3 feet deep if I'm going across a wide open area.

When you put the 125A breaker in the main panel make sure you don't put it across from another large breaker. To much load on one part of the buss tends to build up heat.

 

[Jim greengo]

Conduit only needs 18" of cover, not 24".
Aluminum is alot cheaper.

Yeah you might start out 24" deep,but it doesnt take much for it to become 18" really fast grading out a yard with a teactor.

 

[va72mlibu]

When you put the 125A breaker in the main panel make sure you don't put it across from another large breaker. To much load on one part of the buss tends to build up heat.

Good to know.

So assuming I did go with 2/0 AL, I would need 4 conductors: 2 x 2/0, 1 x 1/0 and 1 x 2AWG, correct? That will pull through 2" PVC?

 

[pattenp]

Personally I would not use a reduced neutral even though it would probably be okay. The equipment ground only needs to be #4 Al. I'd go with XHHW-2 in sizes of 2/0-2/0-2/0-4. 2" conduit will be fine, just use some lube to make the pull easier.

 

[larry4406]

While trenching think about extra conduit for communication. Also maybe a water yard hydrant at the detached shop (water line below frost line).

 

[pattenp]

While trenching think about extra conduit for communication. Also maybe a water yard hydrant at the detached shop (water line below frost line).

Be aware that a yard hydrant may be required to be on a backflow device in your locality. It's required where I live because of the Virginia Clean Water Act. The anti siphon valve on the bib doesn't cut it.

 

[jimindm]

If you really want to future proof, put in an extra conduit run. You never know what the future is.

My garage is 25 years old. I put in an extra run, but at the time it only needed a cable tv wire, and a phone. A few years ago the cable wire was acting up and the company suggested upgrading it. I thought at the time why not run some internet wire.

I wanted hardwire internet. Just that extra wire, was to much for the conduit I had buried. There is a thread here somewhere that I asked about getting a jammed wire, with the end of the fish tape out. In the end I just ran a much larger conduit. I think it is about 1.5 or so. I know just the communication wire running through it, it has a lot of open space.

 

[sberry]

It might need 2 ground at that distance. 1/0 will fit in all the panel lugs and 100 breaker.

 

[Bretny]

Personaly i wouldnt bother putting it in conduit. Your alreaty way bigger than you need. Short of a trencher running throught your electrical run not much happens to direct burrial wire. How ever i have seen conduit colapse , break and fill with water.