Question about feeding a sub panel

[mcmuria]

I recently upgraded the electrical service at my home. My electric co-op replaced the existing 100 amp feed with a 200 amp supply. The upgrade included new wire from the transformer to the power pole pole. I have 100 amps going into my house. (approx. 25 feet from the pole) I am putting a 100 amp panel in my new garage. The garage is also the same distance from the pole. I will have a welder, air compressor, table saw and 2 garage door openers along with a lighting circuit and 2 dedicated outlets at the work bench.
What size of wire do I need to feed the new sub panel?
The wire that runs to the house is #4 copper. Is it the right size?
Thank you in advance.
mcmuria

 

[CNGsaves]

Above doesn't make sense if you upgraded to 200A service, why do you still just have 100A at the house ??

You currently have some sort of subfeed to garage with #4 . . . or are you asking if #4 copper would be adequate for 100A subpanel ??

What country are you in ?? Best advice from GJ sparkies come with ALL information so Update GJ Profile with City / State / Country.

Likely you don't absolutely "need" 100A at the garage and could get by with 90A. If so the most affordable solution is MHF (mobile home feeder) aluminum wire which is 2-2-2-4 and around $1.50/ft. Bury in 2" sch 40 conduit between the two buildings and continue in sch 80 conduit above grade into building, and conduit all the way to subpanel. 100A subpanel in garage but 90A breaker in house.

 

[Norcal]

The 4 AWG copper is fine for the house, but will not be OK for 100A for a garage, as suggested above use aluminum 2-2-2-4 MHF combined w/ a 90A breaker that is a economical solution, if copper is used 4 AWG THWN is rated at 85A, so it would also have to be a 90A breaker maximum, the code allows the conductor size to be reduced from what is normally required on conductors supplying the entire load of a residence, which is why the 4 AWG CU to the house is fine, but that would not apply to a feed to a outbuilding.

 

[wyliesdiesels]

OP- do u want full 100a to garage?

If so then u need #3 CU or #1 AL.

The feed to the garage needs to be 4-wire IF there is a disconnect at the pole.

The neutral bar needs to be isolated in the garage subpanel as well.

Dont forget 2 ground rods...

 

[theoldwizard1]

I recently upgraded the electrical service at my home. My electric co-op replaced the existing 100 amp feed with a 200 amp supply. The upgrade included new wire from the transformer to the power pole pole. I have 100 amps going into my house.

And no one upgraded the wire from the pole to the meter to the new 200A panel ?

 

[theoldwizard1]

I will have a welder, air compressor, table saw and 2 garage door openers along with a lighting circuit and 2 dedicated outlets at the work bench.

If you are a one man operation (i.e. one major power tool operating at any time), your could easily get by with 60A service. You would even have enough capacity to run a mini-split heat pump.

Down sizing would save a lot on the wire cost (which is why Wylie asked his first question).

 

[wyliesdiesels]

And no one upgraded the wire from the pole to the meter to the new 200A panel ?

Thats a good question i didnt think to ask.

I wonder if the service entrance wire(in the riser) and the disconnect or main service panel was replaced...

 

[theoldwizard1]

Thats a good question i didnt think to ask.

Neighbor is a sparky. I saw him running a new drop from the pole to the back of his detached garage a few weeks ago. 400A service ! 200A for the garage, 200A for the house. The back of his garage looks the back of a small industrial building. That's the only reason I thought about it.

Big garage, swimming pool, lathe, mill. Likely going to have heat and A/C in the long run. He gets his supplies at wholesale and the labor is free, so why not !