Help with 100 amp sub box wiring


Old 08-17-04, 06:44 AM
Visiting Guest
Posts: n/a
Question Help with 100 amp sub box wiring


I would like to run 100 amp service to my shop (approx 130 ft from house box to shop box). I plan on being able to run various woodworking tools - 220v and 110v, lights, compresser (220v), welder, and an additional 15 amp run from shop to chicken coop / shed (lights only), another 120 ft. I have 400 amp service to my all electric house going to 2 - 200 amp cutter hammer boxes) The plan is as follows:

1. tap least loaded house box using 100 amp CH breaker
2. use 2-2-2-4 service wire from house box to 100 amp CH shop sub box (130 ft run)
3. wire shop for 220v and 110v using #12 wire as needed with 20 amp breakers. 50 amp for welder with #6 wire.
4. wire from shop sub box to chicken coop / shed with 20 amp using #10 wire (approx 120 ft) - lights only with light duty outlet in shed.

GFI used as needed.

I figure the max. pull I will ever have is using my ARC welder with the lights on (approx 50 amps max). So I should have a spare 50. I may also at some time wire a well pump to the shop sub box. But would not used the welder and pump at same time.

Did I leave out anything? Does this seem like a sound plan?

Thanks for the assist,
Sponsored Links
Old 08-17-04, 07:24 AM
Join Date: Sep 2000
Location: United States
Posts: 18,497
Sounds like a good plan.

Bury the cable at least 24" deep.
Isolate the neutral and ground in the subpanel.
Use a grounding rod at the shop.
All 120-volt receptacles need GFCI protection.
Your 2-2-2-4 is copper, right? Direct burial, right?
Old 08-17-04, 07:50 AM
Visiting Guest
Posts: n/a
thanks john,

cable to be buried at least 24".

the box hook ups I'm a little fuzzy on.

I know 2 -#2s to 100 amp breaker, 3rd #2 to neutral, ground to ground (where rest of grounds connect, right?)

now for the shop box connection - not sure here - I was hoping panel would have directions for this side. guidance?
2 - #2s from house to ?
1 - #2 (neutral) to ?
1 - ground to ?

grounding rod at shop? from shop box to rod? off where in shop box?

2-2-2-4 I was looking at at home depot was alum. (3#2 wires, with additional ground wire - direct burial wire)

thanks again for the help!!!
Old 08-17-04, 08:48 AM
Join Date: Sep 2000
Location: United States
Posts: 18,497
Check with your inspector to see if he allows 2-2-2-4 aluminum to be used for a buried 100-amp feeder to a detached building. Some do, some don't.

Yes, the connections in the main panel is exactly like a 120/240 branch circuit.

The connections in the subpanel are black and red to the main lugs, white to the neutral bar, and ground to the grounding bar. If the panel you buy doesn't come with separate neutral and grounding bars, buy an add-on grounding bar kit. The grounding electrode conductor connects the grounding bar to the grounding rod. Throw away the green bonding screw that comes with the panel.

If you have more than six circuits off the subpanel, you will need a main disconnect in the subpanel.
Old 08-17-04, 09:10 AM
Join Date: Feb 2002
Location: port chester n y
Posts: 2,117
I would be inclined to install a PVC conduit raceway between the 2 structures. This presumes you can excavate a smooth, level trench.

In addition, consider a PVC conduit raceway for communication cables.

Good Luck & Enjoy the Experience!!!!
Old 08-17-04, 09:28 AM
Visiting Guest
Posts: n/a
good point!! I had thought about that some time ago, but had forgot about the phone / cable line.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Display Modes