# Wire gauge size and type for a 100 Amp sub panel



## Arrow3030 (Apr 19, 2015)

1/0 AL is definitely large enough. #4 AL for an grounding conductor is also large enough. If you're using conduit I don't recommend a cable but rather single conductor. 
You seem to be over sizing the conductors BTW.


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## Smokeshow (Dec 20, 2015)

If you want to use conduit, I would recommend pulling 3 #1 and a #4 XHHW in through an 1-1/2" PVC conduit. I might even consider 2" if you're going to have 4 90's like you show in the picture.


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## Kernel (Sep 18, 2015)

I'm surprised by how much the difference in cost of aluminum vs copper. At Wire and Cable To Go website, 1/0-1/0-1/0-2 Nortre Dame URD aluminum cable is $1.72/ft; at 90 feet, that's $154.80. Contrast that to #1 XHHW copper at $1.58/ft; at 90 feet x 3 conductors, that's $426.6. Almost 3X the cost and not accounting for a bare copper #4 wire for ground! 

The general consensus I glean from reading the discussions is for copper, a better conductor with less expansion, corrosion, oxidation issues vs. aluminum. 

What do you think?


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## Know A Little (Sep 29, 2013)

Kernel said:


> The general consensus I glean from reading the discussions is for copper, a better conductor with less expansion, corrosion, oxidation issues vs. aluminum.
> 
> What do you think?


There is NO ISSUE with aluminum when properly installed. The utility companies use it extensively, your house is more than likely fed with Aluminum.


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## Plumbvoltage (Dec 2, 2008)

I have 2 - 200 amp services on my property and both are fed with aluminum. Both have a 100 amp subpanel fed with aluminum also. No issues with either one.


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## Smokeshow (Dec 20, 2015)

Kernel said:


> I'm surprised by how much the difference in cost of aluminum vs copper. At Wire and Cable To Go website, 1/0-1/0-1/0-2 Nortre Dame URD aluminum cable is $1.72/ft; at 90 feet, that's $154.80. Contrast that to #1 XHHW copper at $1.58/ft; at 90 feet x 3 conductors, that's $426.6. Almost 3X the cost and not accounting for a bare copper #4 wire for ground!
> 
> The general consensus I glean from reading the discussions is for copper, a better conductor with less expansion, corrosion, oxidation issues vs. aluminum.
> 
> What do you think?



Sorry, I meant XHHW Aluminum #1. Although Aluminum THWN is just as good too. I just find XHHW pulls much nicer in the dead of winter up here.


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## Kernel (Sep 18, 2015)

Thank you everyone. I plan to use 1 1/4 pvc for the copper OR 1 1/2 for the aluminum. Because of the 4 90-degree turns, I plan to put the wires into the conduit sections, dry fit all of them, and then glue up with the wires already inside. 

I did this once with a run of ~150' of Romex 12-2 (+ground) for a backyard GCFI circuit/outlet. I worked out well. 

I am leaning copper on this job, though more expensive. Smaller wires, less obtrusive conduit, etc. Maybe I am crazy. No?


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## rjniles (Feb 5, 2007)

Kernel said:


> Thank you everyone. I plan to use 1 1/4 pvc for the copper OR 1 1/2 for the aluminum. Because of the 4 90-degree turns, I plan to put the wires into the conduit sections, dry fit all of them, and then glue up with the wires already inside.
> 
> I did this once with a run of ~150' of Romex 12-2 (+ground) for a backyard GCFI circuit/outlet. I worked out well.
> 
> I am leaning copper on this job, though more expensive. Smaller wires, less obtrusive conduit, etc. Maybe I am crazy. No?


Assembling the conduit with the wire in place is a code violation. Assemble it all and pull in the wire. Reason, glue can eat the insulation.


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## Oso954 (Jun 23, 2012)

> Thank you everyone. I plan to use 1 1/4 pvc for the copper OR 1 1/2 for the aluminum.


You are generating a lot of extra work for yourself. Use 2 inch with long radius 90's, not the short radius ones found at the big boxes. It will cost a bit more, but save you a lot of sweat and trouble.


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## Kernel (Sep 18, 2015)

rjniles said:


> Assembling the conduit with the wire in place is a code violation. Assemble it all and pull in the wire. Reason, glue can eat the insulation.


Ah! I've wondered about this for a while. Thanks for letting me know. There goes my plan to make it a bit easier. 

What do you recommend to use as a pull rope? I think metal fish tape isn't prefered by some of the electricians on this board.



Oso954 said:


> You are generating a lot of extra work for yourself. Use 2 inch with long radius 90's, not the short radius ones found at the big boxes. It will cost a bit more, but save you a lot of sweat and trouble.


Oso954, I presume you are referring to the "long radius" 90-degree elbows like this one at the local orange box? They are long and large.


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## rjniles (Feb 5, 2007)

http://d2pbmlo3fglvvr.cloudfront.net/product/large/Z11N0wfo5oy.JPG


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## Know A Little (Sep 29, 2013)

Kernel said:


> Ah! I've wondered about this for a while. Thanks for letting me know. There goes my plan to make it a bit easier.


It is not easier, it would be a royal PIA 



> What do you recommend to use as a pull rope? I think metal fish tape isn't prefered by some of the electricians on this board.


Fish tape to pull in a rope, plenty of wire ease and properly laid out conductors that are not twisted.


2" PVC should be a snap.


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## Plumbvoltage (Dec 2, 2008)

Kernel said:


> What do you recommend to use as a pull rope? I think metal fish tape isn't prefered by some of the electricians on this board.



Put it together and then get yourself a ziploc baggy and a some heavy fishing line. Stuff the ziploc in the end with the line attached and use a shop vac to suck the baggy through to the other end. Hook a heavier line to the fish line and pull that through. Now you have your pull rope for the wire. Worked on mine great and it was about 75ft.


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## Know A Little (Sep 29, 2013)

And remember it is not about pulling the conductors it is about a coordinated effort of feeding the conductors and pulling, and cannot stress enough to lay the conductors out and have the person feeding the wire keep them straight.

Two people can do this but 4 would make the job easy


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## carmusic (Oct 11, 2011)

too bad teck or acwu is not popular in US, it would be a lot easier, that armored cable can directly buried


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## rjniles (Feb 5, 2007)

carmusic said:


> too bad teck or acwu is not popular in US, it would be a lot easier, that armored cable can directly buried


A lot of us don't like direct bury. With conduit, if you have a problem you can replace it without a shovel. Or if you decide you need more capacity, pull in bigger.


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## Kernel (Sep 18, 2015)

I went to a local electrical supply house to see what is available. I were told by one of the staff members that THHN is OK for underground application in conduit. I asked about XHHW and said that I plan to run it underground, outside, in conduit (i.e. underground, wet), but the person insisted that THHN is OK. I am a bit confused. I thought this is not allowed per the NEC?


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## Oso954 (Jun 23, 2012)

Most if not all, THHN sold today will also carry a THWN rating. You can read the printed info on the wire or on the mfg spec sheet.

It is perfectly acceptable for your project.


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## rjniles (Feb 5, 2007)

Today's THHN is dual rated as THWN


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## Kernel (Sep 18, 2015)

So, I will go with #1 XHHW copper for the three conductors. For #4 bare copper as grounding wire (for both the pull and grounding of the subpanel to 2 ground rods), do you recommend solid or stranded? Does it make a difference?


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## rjniles (Feb 5, 2007)

Those conductors only come stranded. And be thankful as you would never be able to pull them if they were solid.


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## Oso954 (Jun 23, 2012)

> For #4 bare copper as grounding wire (for both the pull and grounding of the subpanel to 2 ground rods), do you recommend solid or stranded?


For the ground rods I would use solid bare. For the pull I would use insulated (not bare) stranded.


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## Syberia (Jan 24, 2014)

rjniles said:


> Assembling the conduit with the wire in place is a code violation. Assemble it all and pull in the wire. Reason, glue can eat the insulation.


You also can't use Romex underground, to address the other part of his post.



Kernel said:


> Ah! I've wondered about this for a while. Thanks for letting me know. There goes my plan to make it a bit easier.
> 
> What do you recommend to use as a pull rope? I think metal fish tape isn't prefered by some of the electricians on this board.


That's what I used to think too, before I knew any better. Having done it both ways, assembling the conduit and then pulling the wire is actually much easier, since you're not futzing around with feeding the wire through piece by piece while you're trying to glue everything together. What I do is assemble the conduit with nothing in it, use a shop vac to suck a piece of string through (with a single square of toilet paper tied to the end to give it something to suck on), and if it's just small wire like #12, I'll just tie/tape it directly to the string and pull it through, otherwise I'll use the string to pull a larger rope (1/4"-ish) through, and then attach my wire to that. Just make sure to extend the tape out past the front of the wires so it makes a soft squishy "head" that won't get caught on any of the transitions, have one person pushing while another pulls, and it requires surprisingly little effort.


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## Kernel (Sep 18, 2015)

Thanks everyone! #1 THHN/THWN and #4 bare copper in 1 1/2" conduit it is. I can't wait to get adequate power into this garage!


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## Syberia (Jan 24, 2014)

I don't actually know the answer to this, but can you have a bare EGC in conduit? I've always used insulated, no idea if I have to or if it just seemed like a good idea, though.


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