Wire Size help

[deerhunter88]

What wire size will i need to run a 100 amp breaker to my shop. Will be pulling from my breaker panel in my house roughly 100' away. 30' will run through my attic, the rest will run through conduit underground.

Also if you know of any sources to buy the wire from that may save a little $ please let me know.
Thanks

 

[Stuff]

To save money figure out if you can survive with less than 100 amps.

3 gauge copper or 1 gauge aluminum THWN for 100 amps figuring no correction for voltage drop is needed. Lots of times you can reduce the neutral conductor.

8 gauge copper or 6 gauge aluminum for the grounding conductor.

 

[pattenp]

Be aware you may be looking at two different types of wire for inside and outside. Example you can use SER for the inside which doesn't need to be in conduit and switch to individual wires rated for underground which may or may not need to be in conduit. Or you can use individual wires of types THWN or RHW or XHHW in conduit for the whole run. If buying direct bury type cable just understand if it's URD with just a USE rating it cannot be installed inside. One common type of cable used is Mobile Home Feeder (MHF) which is direct bury cable but can be installed inside and has to be in conduit where above ground.
Here's a good online source .. https://wireandcables.com/

Edit: You need to figure your potential loads to see if you do need a full 100A. If doing 100A and not knowing your exact setup I think 1-1-1-3 AL SER for the inside run switching VIA a junction box to three #1's of XHHW-2 and one #4 of XHHW-2 for the ground is a good option. Use a minimum of 1.5" conduit, 2" will be better for the run to the shop. I assume you will do conduit to the panel in the shop.

 

[wyliesdiesels]

List your loads.

 

[deerhunter88]

Shop will mainly be used for storage and tinkering around with some toys. Small air compressor, general power tools(rarely), maybe oneday a small welder. Nothing serious. Shop will also have a small bathroom built inside it. 100 amps will prlly be overkill but i dont want to sell my future short!

 

[theoldwizard1]

Shop will mainly be used for storage and tinkering around with some toys. Small air compressor, general power tools(rarely), maybe oneday a small welder. Nothing serious. Shop will also have a small bathroom built inside it. 100 amps will prlly be overkill but i dont want to sell my future short!

And that overkill will cost you a lot of $$$ ! 60A is considered more than adequate for any 1 man shop.

Probably the simplest thing to do is use SER or NM-B inside and then install a junction box at the wall before it heads outside (in a conduit) using MHF. Use MUST use the correct splice blocks to join AL to Cu.


If you limit yourself to 60A, you should be able to use #6 UFB continuous.

Measure carefully ! Some online places give a discount it you but "made up" coils of 125'

 

[dave89iroc]

2-2-2-4 MHF will supply 90A at that distance IIRC

 

[Orionrising]

Go with wiring for 90. Unless you a running a big Ac and compressor and welder etc at the same time you won't even need that. I wire sized for 90 but put a 60 amp muuuuchhh cheaper breaker on the feed. If I ever blow it I can spend the bucks to upgrade. Doubt I ever will

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