I have a detached workshop 100 feet from my house that I want to run power to. I need help determining if an existing 30a circuit will work, and what gauge wiring to use for the 100 foot run.
Details
The previous owner of my house had a large air compressor on the corner of the house outside. To power this he had a double slot 30a breaker and 10/2 wire run to a cutoff box outside the house. This location is ideal for running power to my workshop 100 feet away, only one minor 35 degree turn is needed a few feet from the workshop.
In the workshop I think i want two circuits, one 20a to power three outlets for saws and various items on my workbench. The second circuit could be only 10a, i plan on using it to run two exterior LED lights, and an interior LED flood light over my workbench. LEDs are pretty efficient, so I think 10a is enough.
I plan on running 3/4" underground conduit in an 18 inch deep trench (code in my area) and installing an 8 slot 125a sub panel in the workshop to house the 10a and 20a circuits.
My questions are:
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Can i use the existing 30a double circuit with 10/2 wiring, and extend off that to run to my workshop?
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Is 10/2 wiring the proper gauge to run about 106' from the cutoff to my new sub panel?
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The existing 30a circuit uses a 10/2 wire, (1 hot, 1 neutral, 1 ground). Can that be run to a sub panel? Other subpanel install i have seen look like they use a line with 2 hot wires, 1 neutral, 1 ground.
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Does the subpanel need a grounding rod? If so what gauge copper line is needed?
My goal is to do the majority if not all of this work myself, especially the conduit and running the wire. I use extension cords today and it's getting a little old. Especially tired of my chop saw not getting up to full power and speed.
Best Answer
You can put in a sub you need 4 wires ground , neutral and your 2 Hots. Since the shop is detached you will need to have a ground rod and #6 wire is normal for you his , I would consider running a larger feeder wire than #10 but if only running 1 saw and your lighting #10 could work. Even though you have the wiring protected at the main panel with a 30 amp breaker your sub can have a total of more than 30 amps if you add the breakers. For example if all single pole breakers you may have 80 amps if you total all the breaker values. The total load is the important thing here as we usually have a safety factor and only use 80% of the circuit capacity. In fact most homes that I check are running at 25% of their main breaker or less. So yes you can but I would go bigger, I have never been asked to reduce the size of a panel but many times I have gone back and upsized the service. At a minimum put in larger conduit so you can upsize later. Added I was realizing that you did say 2 with ground as I earlier mentioned you will need 4 wire to the sub since you will need to add a neutral if in conduit back to the panel this or a new 4 wire run at the largest size you can afford, for example I just put a sub in for a small heat pump it needed a 20 amp circuit , I put in #6 and a small sub, now I have plenty of power to add lighting to my round pen and even a hot tub over there or whatever I might need hope the additional info helps.