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Inactive, Master Electrician
Category: Electrical
Satisfied Customers: 4772
Experience:  Electrical Contractor
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What size wire do I need to supply an 80 amp sub panel

Resolved Question:

What size wire do I need to supply an 80 amp sub panel?
Submitted: 8 years ago.
Category: Electrical
Expert:  Inactive replied 8 years ago.
Can you tell me how far away from the main service it will be? Also is the building where it will be located attached or detatched to the main building?
Customer: replied 8 years ago.
This is in a detached garage with a total run of 40 feet.
Expert:  Inactive replied 8 years ago.
Ok - you have two ways you can do this.

Option1) you can install conduit from the house panel to the garage panel. The size you want to use for that distance would be 2". (trust me the pull will be much easier) Then you will run #4 thhn copper for 3 of the conductors (2 hots 1 neutral) then you will use a #6 for the grounding wire. You will bury this 2' into the ground. Then at the garage panel you will need to install a grounding bar kit to isolate your grounding bar from the neutral bar. Next you will install 2 grounding rods spaced at least 6' apart and bond them to the grounding bar in the panel using a solid #6 grounding wire.

Option 2) you can purchase #2 direct bury Quadraplex. This is an aluminum direct bury service cable and again - you will bury it 2' deep. Now the advantage of doing it this way is that the wire is cheaper and comes as a complete cable. You will need to use conduit on the end runs where the cable exits the ground and goes into the home to the panel. Then at the garage panel you will need to install a grounding bar kit to isolate your grounding bar from the neutral bar. Next you will install 2 grounding rods spaced at least 6' apart and bond them to the grounding bar in the panel using a solid #6 grounding wire.

Now here is a pictoral diagram of how to set this up - now even though it does not show it - you need to be sure you have a main breaker in the subpanel.
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