2/0-2/0-2/0-#1 OK for 200 amp service?

[-dirt-]

Hi all:

I'd like to run 200 amp service to a subpanel 150' from my meter. This will serve a detached guest house/bonus room. This subpanel will also provide power to my workshop.

The guest house will have a elec. water heater, oven, window A/C, septic ejector pump, fridge, and upright freezer. Shed will see normal tool stuff. Max draw would be 120v compressor and 30 amp welder. The guest/bonus room will be intermittent use initially but could transition to a full-time apartment later. The workshop is just hobby, so it is intermittent use.

I realize I might could get away with lesser service size (150 amp maybe) but would rather future-proof while I'm trenching and spending $$.

Can someone please double check my calculations that 2/0-2/0-2/0-#1 URD aluminum is OK for 200 amps direct bury at 150 ft?

(Disclaimer: I realize that this may present issues with my current drop service to house, but I will deal with upgrading to 320 amp or 400 amp service later if needed. Also I would rather not get a new drop service to the guest house.)

Any constructive input/suggestions are welcome!

Thanks so much!

 

[pattenp]

2/0 Aluminum is rated at 135A. For 200A you need to use at least 250mil Al. I don't know how you got 2/0 Al is ok for 200A.

 

[Terry D]

I don't want to start a argument here or any big discussion, but here we are allowed to use 4/0 aluminum for service and subpanel feeders for dwelling units, and they consider that detached garage part of the dwelling. And I understand there are a lot of jurisdictions that don't allow using the dwelling table to size dwelling feeders, but there are some that do. But that's not figuring in any voltage drop. I would suggest to check with your local codes. But as already said, you cannot use 2/0 aluminum for 200 amp

 

[mike93lx]

Besides gauge, URD can't go inside. You'll need to transition to something else before entering the building, if you are doing that.

Mobile home feeder can be run indoors (in conduit) plus direct bury

4/0 is good when it is feeding an entire primary structure, IIRC. In this case, it needs to be stepped up because it is going to a sub

 

[Samh]

2/0 Aluminum is rated at 135A. For 200A you need to use at least 250mil Al. I don't know how you got 2/0 Al is ok for 200A.

Maybe he saw 2/0 CU, but I think that is even a little small for 200A. I just got 3/0 CU for my 200A

 

[-dirt-]

The specs here listed 225 amps when direct bury for this cable:

https://www.wireandcableyourway.com/2-0-2-0-2-0-1-syracuse-underground-secondary-distribution-cable.html

Also, if I plugged the numbers in right, the Southwire Voltage Drop calc gave a 1/0 as acceptable for this scenario:

https://www.southwire.com/calculator-vdrop

I see where 2/0 is rated at 135 amps, but that's for one conductor, right? This has 2 plus the neutral and ground... Am I looking at this wrong?

https://images.homedepot-static.com/catalog/pdfImages/d2/d2013d0b-a2a0-4cc5-ba6d-d81edc5c9a50.pdf

Also, yes I'm aware URD needs to stay outside and that is no problem, as both panels (home and guest house) are exterior mounted. Will most likely stub up into a large junction box at the house and split bolt to smaller diameter copper for easier feeding into main breaker box.

Thanks for the help!

 

[pattenp]

You can't go by what's listed on some resellers website, you need to follow the NEC. Also one conductor vs multiple conductors doesn't factor into the allowable ampacity. The max allowable amperage on a #2/0 Al conductor is 135A. You can pull 135A on one #2/0Al conductor @ 120V or 135A @ 240V on two #2/0Al conductors. With 240V the two conductors are 180deg apart so the amperage is switching between the two conductors.

 

[mike93lx]

Patten, you should correct that from #2 to 2/0

 

[-dirt-]

You can't go by what's listed on some resellers website, you need to follow the NEC. Also one conductor vs multiple conductors doesn't factor into the allowable ampacity. The max allowable amperage on a #2 Al conductor is 135A. You can pull 135A on one #2Al conductor @ 120V or 135A @ 240V on two #2Al conductors. With 240V the two conductors are 180deg apart so the amperage is switching between the two conductors.

Thanks for setting me straight! Straight forward responses with the reasoning behind them is why I really like this forum.

 

[pattenp]

Patten, you should correct that from #2 to 2/0

I was testing to see who was paying attention.

 

[-dirt-]

If I go with individual conductors in conduit, is #6 copper ok for the ground between the panels? That looks right per Table 250.122...

 

[mike93lx]

I was testing to see who was paying attention.

I win!

 

[pattenp]

If I go with individual conductors in conduit, is #6 copper ok for the ground between the panels? That looks right per Table 250.122...

Yes. Check with your local inspector to see if 4/0 Al is acceptablefor 200A, if so, then 4/0 MHF maybe your best option.

 

[SSStang]

What did you need up using for wire?

 

[wyliesdiesels]

I don't want to start a argument here or any big discussion, but here we are allowed to use 4/0 aluminum for service and subpanel feeders for dwelling units, and they consider that detached garage part of the dwelling. And I understand there are a lot of jurisdictions that don't allow using the dwelling table to size dwelling feeders, but there are some that do. But that's not figuring in any voltage drop. I would suggest to check with your local codes. But as already said, you cannot use 2/0 aluminum for 200 amp

we can do that here too but ONLY when it is supplying the entire dwelling and nothing else.

he is also powering a shop with it.

 

[Norcal]

If the calculated load was 180A or less, 4/0 AL could be used for 200A.