Need Subpanel Help


Old 12-20-05, 10:47 AM
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Thumbs up Need Subpanel Help

Hello all,

I am really impressed by how helpful thre regular posters are in this forumn, and I think I am going to have to put your good will to test.

I am an electrical rookie. Done my fair share of circuit wiring, but I have to tackle the install of a subpanel in one of my outbuildings.

Here is the situation. I have a 60 ft quonset with the original panel at one end, and a shop area at the other. I have wired a bunch of circuits at the other end, and want to install a subpanel instead of a bunch of long runs (obviously).

Here is what I have:

1. Original Panel is at least 20 yrs old. Not much on it.
its 100 amp load center - square D and says cat #8 on it.

It is grounded into the ground with a wire and rod.

There is no draw hardly off this panel. It has one outlet, and a switch
and light circuit.

It was probably only used to plug in a tractor.

2. At the other end, I have a new Siemens subpanel eql 8100D - 100 amp.
It has 8 1" slots in it.

For circuits, I have.
3 circuits with lights, and general outlets
1 dedicated single outlet circuit (table saw/mig welder)
1 dedicated 240 outlet (stick welder) - its wired with 6/3 wire.

3. What I would like to do.

A. I would like to add a 70 amp breaker to the main box (?)

is 70 amps normal, can you get a breaker in that size ?
should I use a 100 amp breaker instead ?
any other advise ?

B. Run 60 ft of wire to the new subpanel (in conduit)

What kind of wire, and how many conductors ?
Exactly how do I wire it at both ends the old and new locations
I literally need to be told what color to what part of the panel (sorry)
how do I handle grounding. The main panel has a ground installed.

C. Energize new panel without killing myself.
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Old 12-20-05, 11:06 AM
Join Date: Sep 2003
Location: Central New York State
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Originally Posted by sbacresdad
Exactly how do I wire it at both ends the old and new locations
I literally need to be told what color to what part of the panel (sorry)
how do I handle grounding.
No, you don;t need to be told what to do. You either need to pay someone to do the job for you, or you need to read up on this subject and learn what it right. Then you can post your proposal and we will comment on it.

having us tell you what to do for each step is NOT the way to do a job like this. Electricity can kill, and you need to know a lot more about it than you do to do a job like this.
Old 12-20-05, 11:36 AM
Join Date: Sep 2000
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Although Bob's bluntness can be a bit shocking, he is essentially correct. Q&A is really not the best way to learn a skill from scratch. Whole books have been written on this subject, and we can't really write a book in this forum, nor do we need to since such books are readily available.

I suggest you get several books. First get one with a lot of colorful pictures. These books describes terms, show you common procedures, and contain a lot of important safety and technique information. Black and Decker, among others, publishes a variety of such books. Then I suggest you get a book that is a bit more technical and provides more code information. My favorite is a $6 green paperback, Wiring Simplified.

Then you're going to need an advanced book. Most home wiring books don't go so far as telling you how to put in a subpanel, because that's a pretty advanced topic, and beginners are usually better off letting a pro do that. That's not to say that you can't learn, but it'll take you a lot of study. Subpanels are a very common topic on this forum, so if you search this forum for that topic, you'll find plenty of reading. Just make sure you understand whether you're reading about subpanels in attached or detached structures, as the procedures are quite different.

The plan you presented is generally good, but there's a lot of details left out. Start by telling us the input power requirements of your welder. That will say a lot about how much power you need at your subpanel. If the welder is small, you can probably use a 60-amp double-pole breaker and 6/3 UF-B cable buried at least 24" deep. You'll need a grounding rod at your outbuilding, and you'll need to isolate the grounds and neutrals.

Most important of all is a permit. Get a permit from your city or county. Your best protection is to have the city inspector check everything out before you energize it. If the inspector is willing, make an appointment to go over your plans with him before you start. But don't irritate the inspector by expecting him to educate you. That's not his job. You're expected to know how to do the job before you talk to him. He just provides a double-check.
Old 12-20-05, 03:15 PM
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Thanks for your professional, and courteous help. Neil and Bob's remarks above left me thinking that moderation was lacking here, but you restored my confidence, and I can certainly see why you have a successful forum here.

I actually have a more basic knowledge of wiring than I let on in my post, but was initially afraid that coming in like a know it all would anger some of the regulars (appears as though it had the opposite effect on one person).

I will take your advice, and have already gotten some helpful advice from other sources on the internet, and people I know in the construction industry, and will definitely let you know how it goes in the end.

Thanks again.

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