Sizing My Detached Garage Sub Panel Wiring

[bamava05]

Looking for input from the experienced electricians on this one.
Will be supplying the power to my detached garage (new construction) 100 amp sub panel from a 100 amp double pole breaker in my existing 200 amp house panel.
There is 2" electrical conduit existing underground from a previous building that was site cleared which now leads to the detached garage. The run will be 30 feet one direction. Would like to know the exact size and wire types i will need to feed through the conduit that supplies this sub panel. forgot to mention. I will have two 220 drops, one for air compressor and one for a mini split system
Any help is appreciated.

 

[wyliesdiesels]

theres numerous threads on here with your situation.

Do you really need 100a? if not go with #2 al MHF on a 90a breaker

If you must have 100a, then you need #1 al- 3 #1 al wires and 1 #6 for ground...

make sure to isolate neutral in subpanel. you will also need 2 ground rods...

 

[bamava05]

I dont really need 100 amp.. what is the advantage of going with 90amp versus 100 amp?

 

[Norcal]

I dont really need 100 amp.. what is the advantage of going with 90amp versus 100 amp?

Cheaper. The breaker will be the same but the wire will cost less.

 

[xyster101]

I ran the famous Mobile Home Wire. It was really cheap. I put in in pipe the whole way out, but you can direct bury it. It slides nice through 2" pipe with some lube. I had three 90 elbows on a 25 ft run and it was not a problem.
If you want the extra amps, check to make sure the wire will fit inside the pipe with some extra wiggle room.

 

[bamava05]

im going to throw another twist on this question.
Maybe this is a better route.
I currently have a two pole 60 amp breaker that was feeding the small building we site cleared. I believe 60 amps will be plenty. I can leave that breaker in place.. If i do that, I already have the 100 amp panel in the detached garage. How do I go about using the 100 amp panel, do I need to change the main breaker in it, and what wire would i use inside the conduit to the detached garage.

 

[pattenp]

The main breaker in the subpanel serves no more than a disconnect. The 60A feeding breaker protects the feeder wire. You can still use #2 MHF to give you some expansion room and it will fit in a 60A breakers lugs. Recommend 2" conduit for the #2 MHF.

Edit: If you don't want more than 60A you can use three #4 Al XHHW-2 and one #8 Al XHHW-2. This will fit in 1" conduit. The #8 will need to be purchased in green. #8 may not be available in XHHW-2, so #6 in green.


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[dave*99]

The main breaker in the subpanel serves no more than a disconnect. The 60A feeding breaker protects the feeder wire. You can still use #2 MHF to give you some expansion room and it will fit in a 60A breakers lugs. Recommend 2" conduit for the #2 MHF.

Edit: If you don't want more than 60A you can use three #4 Al XHHW-2 and one #8 Al XHHW-2. This will fit in 1" conduit. The #8 will need to be purchased in green. #8 may not be available in XHHW-2, so #6 in green.


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I'm not doubting your advice - but perhaps the OP in his recent "twist" question, if considering keeping the existing wire in the existing 2" conduit with the existing 60A breaker in the main panel. He is asking if the 100A breaker in the sub panel is OK - and it is.

 

[pattenp]

I'm not doubting your advice - but perhaps the OP in his recent "twist" question, if considering keeping the existing wire in the existing 2" conduit with the existing 60A breaker in the main panel. He is asking if the 100A breaker in the sub panel is OK - and it is.

I was answering the twist question. I said the main breaker in the subpanel was okay as it serves only as a disconnect. And I'm not seeing any reference to existing wire as the OP was asking what wire size to use. The only thing existing he was saying he was going to use was the 2" conduit and perhaps the 60A breaker. I was providing some additional info for a lessor size wire and minimum conduit size for that wire. Sorry if you didn't like my response.

 

[dave*99]

I was answering the twist question. I said the main breaker in the subpanel was okay as it serves only as a disconnect. And I'm not seeing any reference to existing wire as the OP was asking what wire size to use. The only thing existing he was saying he was going to use was the 2" conduit and perhaps the 60A breaker. I was providing some additional info for a lessor size wire and minimum conduit size for that wire. Sorry if you didn't like my response.

I didn't disagree with your response - I was looking to see if the OP's twist question was answered in full. BUT - My bad, after reading it a third time I see no mention of existing wire.

 

[bamava05]

Thanks for all the help..
One last question, they are asking me if I want stranded wire or solid wire for the feed that runs from my main panel to the sub panel in detached garage. It will be going through existing 2" conduit for about 30 feet or so.

Thanks

 

[alfredeneuman]

Who are "they"?
Any wire that is large enough to power a subpanel is going to be stranded.
Solid wire (besides bare) is only made in size 10 and smaller.
There's also a Code prohibition against using #8 solid and larger in conduit.
EDIT: The Code prohibition does not apply to Grounding Electrode Conductors

 

[wyliesdiesels]

Must be a newbie.

Good luck finding solid #2 al...

 

[Norcal]

Must be a newbie.

Good luck finding solid #2 al...

Any conductor over 10AWG must be stranded that is to be pulled in a conduit, have seen 4 AWG solid but it was used between a fusible switch & a mag starter in a old combo starter, so not really a good example. I don't see anyone getting solid insulated conductors 8 or larger it is not going to be easy because of low demand.

 

[mwc13]

I know this thread is old, but in case someone wanted to know, growing up on family farm, and now moving back, there is still some overhead individual solid #1 "Solid" wire to out building in use still. So yeah is that big. And is getting all replaced with bigger triplex for larger capacity, but there is/was bigger solid wire. Also only want stranded in conduit, just practical any gauge, and other than branch circuits sub panel feeds and larger than 10 should be stranded. Can use either AL or CU for feeding sub panels, dryer/ranges, I prefer to use copper for all but service entrance and sub panel feeds then I use the SEU/SER service entrance cable those. and for all sub feeds four conductor to sub panels keeping neutrals and grounds separated, only should be tied first entrance point into primary source, usually main panel thereafter keep separated. remember, panel rating are maximum can use, can use lower amperage, so from main panel can have a 60A breaker feeding a sub panel rated for 100A, the upstream breaker (main panel) will be sized to wire used, etc.if needing 100A then wire size and upstream breaker rated as such, if more than six branch circuits in sub panel then a main breaker required in that sun panel as well, can be lower then upstream but not higher. six circuits or fewer in a panel does not require a main breaker. If location is never expected to use more than six circuits as such, but panel can handle more, I use a main lug convertible panel reserve the slots where may need to mount a main kit later if needed to expand number of circuits. but of course can go ahead and use a panel with main regardless in that case.