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Old 04-28-2009, 01:12 PM   #1
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Another Outbuilding/Sub-Panel Question


I have 200 Amp service in main house. Outbuilding is 150 feet away and will have small workshop loads (table saw, band saw, belt sander), maybe 6-8 more outlets and some average lighting needs. Will only be using one tool at a time. Was planning on a 100 amp 12 space (24 circuit) sub panel with 60 amp circuit breaker at main panel in house. I know I need to ground the sub-panel and disconnect grounding and neutral bar. What I need is some opinion on wire or cable sizes. I know this is asked a lot, and I apologize in advance. Do I need to pull 4 wires? Sizes? The wiring will be within 2" dia PVC pipe buried 42" below grade with large curves at each end. Unfortunately, the end of the conduit (installed by previous owner) is outside the house perimeter (but inside the outbuilding) so I assume I need to use outdoor rated wire? Can anybody help with wire sizing for "typical residential workshop" needs? Any other comments/tips? Thanks in advance!

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Old 04-28-2009, 03:36 PM   #2
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Another Outbuilding/Sub-Panel Question


Hi tpagel:

Seems U know alot already; that's commendable. As a speculation on my part though, I don't think U got ur smarts frm the NEC book. Cause if ya did, you'd know how to read the tables for wire sizing and insulation types.

But hey; that's wut this chat is all about, right? OK, first of all you only need to run three wires. Running a ground wire frm ur main to use in the out building will cause a potential shock hazard. The ground rod for the main is for the main. (grnd rod should be outside, up against the house where the panel is located inside yur house)
** Drive another grnd rod outside where the new pnl is to B located.
------------Next--
Wire size- I yur going to use a 60A brkr 4 the new pnl, then use wire rated at 60A. Ahh, but no; you need to de-rate the wire because of the 150 ft. run. (hold on while I gt my Code Book).

OK, here it is. To put it in the simplest way, U should run #4 copper (according to code) for the de-ration factor. Ur not doing this because of temperature, but because of length- voltage drop.

I think you already know this, but U can use #6 for 60A. But, because of the resistance in the wire for 150 feet, you need to up yur size to the nxt lrgr. Oh, and use a #8 copper grnd wire.

Now, if you want to go with aluminum wire, that's another story.

Use #2 AL and #6 AL grnd wire. Now, U R probably going to run into the cost vs. ease of pull problem. Your wire sizes will stay the same, but the better "jacket" on your cable is going to cost more.

The best jacket for pulling long distances is thermoplastic, like THHN and THWN. But no matter what U decide 2 use, make sure you use wire-pulling lubricant- yule be sorry if U don't. Ideal makes some real good stuff- it's bin awile. but I think it's "Yellow 77".
Just sum advice: U should hav two men pushing (feeding) the cable into the conduit and two on the other end pulling- and you better have 2-way communication.
a link you may find useful is: http://www.electrician2.com/calculat...cpd_ver_1.html

ps: I looked up a job I did in 2002, similar to yours. I did it on the "absolute cheap" and used aluminum SEU cable (which I don't suggest) and the cable then was 87 cents/ft. That gave me two separate hotlegs and the aluminum mesh for the neutral- under one jacket. If go with this, get lots of lube (and be very liberable with it) and be careful, it stains clothes.


Last edited by Stixx; 04-28-2009 at 03:51 PM. Reason: added a ps:
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Old 04-28-2009, 09:46 PM   #3
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Another Outbuilding/Sub-Panel Question


Quote:
Originally Posted by Stixx View Post
OK, first of all you only need to run three wires.

....Oh, and use a #8 copper grnd wire.
Sorry for the dumb follow up (I only know what I read here on the forum, so I am trying to do the grunt work and then let an electrician handle the actual hook up to the power), but I need to pull two #4 copper wires and a #8 copper ground?
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Old 04-28-2009, 09:48 PM   #4
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Another Outbuilding/Sub-Panel Question


I didn't know Prince read this forum. And that he was an electrician too.
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Old 04-28-2009, 09:49 PM   #5
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Another Outbuilding/Sub-Panel Question


Quote:
Originally Posted by tpagel View Post
I am trying to do the grunt work and then let an electrician handle the actual hook up to the power)
Make sure you clear it with them first, some of them don't like to do this.
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Old 04-29-2009, 04:26 AM   #6
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Another Outbuilding/Sub-Panel Question


Quote:
Originally Posted by Stixx View Post
Hi tpagel:

Seems U know alot already; that's commendable. As a speculation on my part though, I don't think U got ur smarts frm the NEC book. Cause if ya did, you'd know how to read the tables for wire sizing and insulation types.

But hey; that's wut this chat is all about, right? OK, first of all you only need to run three wires. Running a ground wire frm ur main to use in the out building will cause a potential shock hazard. The ground rod for the main is for the main. (grnd rod should be outside, up against the house where the panel is located inside yur house)
** Drive another grnd rod outside where the new pnl is to B located.
------------Next--
Wire size- I yur going to use a 60A brkr 4 the new pnl, then use wire rated at 60A. Ahh, but no; you need to de-rate the wire because of the 150 ft. run. (hold on while I gt my Code Book).

OK, here it is. To put it in the simplest way, U should run #4 copper (according to code) for the de-ration factor. Ur not doing this because of temperature, but because of length- voltage drop.

I think you already know this, but U can use #6 for 60A. But, because of the resistance in the wire for 150 feet, you need to up yur size to the nxt lrgr. Oh, and use a #8 copper grnd wire.

Now, if you want to go with aluminum wire, that's another story.

Use #2 AL and #6 AL grnd wire. Now, U R probably going to run into the cost vs. ease of pull problem. Your wire sizes will stay the same, but the better "jacket" on your cable is going to cost more.

The best jacket for pulling long distances is thermoplastic, like THHN and THWN. But no matter what U decide 2 use, make sure you use wire-pulling lubricant- yule be sorry if U don't. Ideal makes some real good stuff- it's bin awile. but I think it's "Yellow 77".
Just sum advice: U should hav two men pushing (feeding) the cable into the conduit and two on the other end pulling- and you better have 2-way communication.
a link you may find useful is: http://www.electrician2.com/calculat...cpd_ver_1.html

ps: I looked up a job I did in 2002, similar to yours. I did it on the "absolute cheap" and used aluminum SEU cable (which I don't suggest) and the cable then was 87 cents/ft. That gave me two separate hotlegs and the aluminum mesh for the neutral- under one jacket. If go with this, get lots of lube (and be very liberable with it) and be careful, it stains clothes.
tpagel,
Ignore this post. Inaccurate information. Do a search on subpanels/workshop/garages on this forum. This topic has been covered many times and you should be able to find what you're looking for.

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