Wire size for subpanel?

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  #1  
Old 12-18-13, 12:26 PM
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Question Wire size for subpanel?

Guys - I'm trying to post a new post, but can't find a "button" anywhere that lets me start a new thread. I KNOW I'm stupid! Somebody point out where the "start a new thread" button is, please!

Here's what I'm trying to find out, JUST in case someone reads this:

I live on a ranch and have underground electrical to my 100 amp panel on my well house. I am setting up a wood-working shop in a separate building that is 220 feet away. I want to put a 100 amp subpanel in the shop, to give me 110v and 220v for my power tools. It's only me, so i won't be running anything more than one tool and a dust collector at a time (at least that's what I think!).

I plan to run 2" PVC Electrical (gray) conduit underground (2 ft deep?) from the well house to the shop, and run 4 wires (2 hots, a neutral and a ground) to the sub panel. What wire size (copper and aluminum) should I use? And should I "upsize" the wire to handle a 200 amp panel in case I ever want to increase the capacity in the future? I read a lot of posts, but still wasn't sure. If possible, "dumb down" the answer for me - I am definitely NOT an electrician, but plan to hire a retired electrician to do the work.
THANKS for any help anyone can provide!!!
 

Last edited by Nashkat1; 12-18-13 at 05:52 PM.
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Old 12-18-13, 12:57 PM
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to give me 110v and 220v
Actually it will give you 120 and 240 volts.

I plan to run 2" PVC Electrical (gray) conduit underground (2 ft deep?)
2 feet is fine but it can be as shallow as 18".

It sounds like you only need a 60 amp panel but if you want to go to 100 amps you can. Even with the distance given your load for a 100 amp feed three #2 and one #8 copper or three #1 aluminum. and one #6 should be enough. If you went with a 60 amp feed three #4 copper and one #10 should be enough. Cost wise you may want to consider mobile home quadplex.
 
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Old 12-18-13, 01:08 PM
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DUH! Yep, 120 and 240 ... I knew that! Thanks a LOT for the info! And it sounds like if I run for 100 amps I'll be fine, and don't need to worry about any "upsizing" in the future!
 
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Old 12-18-13, 01:28 PM
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I'm trying to post a new post, but can't find a "button" anywhere that lets me start a new thread. I KNOW I'm stupid! Somebody point out where the "start a new thread" button is, please!
That's OK, you've got a new thread now. The button to start a new thread is at the top of the page where the thread titles are listed, in the same place the "Reply to Thread" button is on this page. For this forum, that's Electrical - AC & DC.

To your question,
I live on a ranch and have underground electrical to my 100 amp panel on my well house. I am setting up a wood-working shop in a separate building that is 220 feet away. I want to put a 100 amp subpanel in the shop, to give me 110v and 220v for my power tools. It's only me, so i won't be running anything more than one tool and a dust collector at a time (at least that's what I think!).
Is the panel at your well house your main panel, or is it a subpanel fed from a main panel at your house? Do you have a 100A electrical service or something larger? Where is your meter?

Sorry, but you can't get 110V or 220V. You have a 120/240V service, so you can only get 120V and 240V. That's OK, because that's what your tools and lights need anyway.

I plan to run 2" PVC Electrical (gray) conduit underground (2 ft deep?) from the well house to the shop, and run 4 wires (2 hots, a neutral and a ground) to the sub panel.
18" deep unless covered by a concrete slab.

What wire size (copper and aluminum) should I use?
From what you've listed, you won't need anywhere close to 100A in your shop. 60A is probably overkill, but let's figure for that. To feed a full 60A on a 220' run and keep the voltage drop to less than 3%, you need to pull #3AWG copper conductors or #1AWG aluminum. Tell us the actual load you'll be feeding and that may lead to a solution that can use thinner wire.

And should I "upsize" the wire to handle a 200 amp panel, in case I ever want to increase the capacity in the future?
Do you have a 200A service?

.
 
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Old 12-18-13, 05:29 PM
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with a 60 amp feed three #4 copper and one #10 should be enough.
When you upsize conductors for voltage drop, you must also upsize the ground. I'd use a #8 ground along with the #4 conductors.

with the distance given your load for a 100 amp feed three #2 and one #8 copper
The same holds true here, upsize the conductors to #2 and I'd upsize the ground to a #6
 
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Old 12-18-13, 05:56 PM
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Wire size for subpanel

As just mentioned by Nashkat1 your actual load will make a big difference in the voltage drop. If your only using 30amps of your 60amp circuit at any given time then #4-CU would get you under 3% drop, at 60amps you would be at about 3.4% drop. The price of copper is high so using aluminum may save you some money.
 
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Old 12-18-13, 07:12 PM
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GREAT feedback guys!!! Here's more info, based on what several of you asked:
1. My 100 amp service at the well house is the main panel. We don't have a home on the property yet.
2. We brought in underground service to a BIG 440v 3 phase transformer that sits about 50 feet from the wellhouse. Even though I'm not using 3 phase right now, I was advised to bring it in (if available, which it was) so i could have "cheaper" electricity later, if we set up a vineyard, wine making facility, etc.
3. The county only approved me for a 100 amp service to my well. At some point I'll have to go back, pay the thieves more money for more permits, to get 200 amp service from the transformer sitting next to my well house!
4. I have NO idea of the load right now. Would I be "safe" to plan on something like 80 or 90 amps and size the wire based on that?
5. I like the idea of saving money by running aluminum from the panel to the sub panel.
6. If I do go with aluminum, can the ground wire be aluminum as well?
Thanks again - this forum is GREAT!
 
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Old 12-18-13, 07:16 PM
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Thanks CasualJoe. I've consolidated all the requests into a single reply that I just submitted.
 
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Old 12-18-13, 07:41 PM
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Wire size for subpanel

You mention a 440V transformer, I assume it is really 480V. Is that a utility transformer or is that your transformer. Since it would appear you have much bigger plans for this property I would think about running 480V to your shop and installing a transformer there. Conductors will be much smaller at 480V and transformers have adjustable taps for voltage variation if needed. In answer to your question, yes the ground wire can be aluminum.
 
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Old 12-18-13, 07:45 PM
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The ground (GEC) wire cannot be in contact with the earth if aluminum.
 
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Old 12-18-13, 08:05 PM
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Lesly, I've merged your two threads into one to avoid confusion. Only one thread per topic please.

1. My 100 amp service at the well house is the main panel. We don't have a home on the property yet.
2. We brought in underground service to a BIG 440v 3 phase transformer that sits about 50 feet from the wellhouse. Even though I'm not using 3 phase right now, I was advised to bring it in (if available, which it was) so i could have "cheaper" electricity later, if we set up a vineyard, wine making facility, etc.
So you presently have one 100A service with the ability to add more.

3. The county only approved me for a 100 amp service to my well. At some point I'll have to go back, pay the thieves more money for more permits, to get 200 amp service from the transformer sitting next to my well house!
I assume you're referring to the dedicated and knowledgeable public servants who are employed by the jurisdiction having authority over electrical installations where your property is located. If so, remember that the fees they collect pay for the cost of inspecting all work to make sure that it is done safely and in compliance with the codes which the jurisdiction has adopted. They also pay for keeping the staff abreast of the latest changes.

That brings up an interesting point, which is that "all codes is local." Your jurisdiction and its inspectors have the final say on the way things need to be done where you are. We base our advise on the National Electrical Code, which is a model code. It has no relevance to the work you're doing until and unless it is adopted, in whole or in part by your jurisdiction. They may adopt it as it is, adopt something else entirely, or adopt the NEC with additions and amendments.

The bottom line is that you must meet what's adopted there. Our advice is totally secondary to their requirements.

As a corollary, your local inspectors are your best source of information and advice on what will work. Ask them.

4. I have NO idea of the load right now. Would I be "safe" to plan on something like 80 or 90 amps and size the wire based on that?
Sure you do.
It's only me, so i won't be running anything more than one tool and a dust collector at a time (at least that's what I think!).
Just add the loads of all of the equipment you might be running at one time.
5. I like the idea of saving money by running aluminum from the panel to the sub panel.
6. If I do go with aluminum, can the ground wire be aluminum as well?
Yes.
 
  #12  
Old 12-18-13, 08:56 PM
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Thanks everyone. That is a BIG help! And I apologize for starting two threads. I couldn't figure out how to start a thread at first, so I leapfrogged (via a reply) onto a very old thread.

I'm sure my transformer is 480V and not 440v as I stated. It is whatever size that the local electrical company put in so that I wouldn't have to worry in the future about having more power brought onto the property, which is a very expensive proposition.

And yes, local government inspectors are "here to help," but you should live in California and see all the rules and regulations (and permits!) as compared to many other states that I'm sure are just as safety conscious.
 
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Old 12-18-13, 09:36 PM
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I've worked there. I didn't notice any significant difference between the regulations there and elsewhere. The most significant difference I've noticed is between conduit-requiring areas such as Chicago, New York and yes, Los Angeles, and non-conduit-requiring areas.

Your local inspectors - the inspectors for your local jurisdiction - serve all of us. Every time they help prevent a loss, my coverage goes down too. More importantly, they're the ones who know the code in your area. They are your best instructors and advisers, and the only people who can approve your work.

I'm friends with every inspector in the seven jurisdictions where I've worked recently. Not because i butter them up, but because I respect them. I've learned a lot by talking with them. It's part of my continuing education, and adds to everything else I've learned over the years.
 
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Old 12-18-13, 09:57 PM
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Well put! You've given me a different - and actually better - perspective! Thanks.
 
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Old 12-19-13, 06:27 AM
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2. We brought in underground service to a BIG 440v 3 phase transformer that sits about 50 feet from the wellhouse. Even though I'm not using 3 phase right now,
What is the voltage and phase of your service? I had assumed you had a typical single phase 120/240 volt service, but you cannot get that from a 480 volt transformer.
 
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