what size wire for 100 amp subpanel?

[Matthew Curtis]

What size wire should I use for 100 amp panel about 70 feet from main panel.?

[Anthony Whitesell]

The current-carrying conductors would need to be 1/0 if aluminum, so you'd be looking at 1/0-1/0-1/0-2 aluminum SER.

[Matthew Curtis]

When getting a subpannel, do I need anything special for using the Aluminum? I was looking at this panel:

http://www.lowes.com/pd_41289-1318-G...ntity_sold%7C1

[Anthony Whitesell]

Read through this thread:

http://www.sawmillcreek.org/showthread.php?t=151569

They mention an non-oxidation gel and breakers that are compatible with aluminum wire.

[Matthew Curtis]

why do I see the wire size differ so much? I see anything from 2 gauge to 2/0

[Rod Sheridan]

What size wire should I use for 100 amp panel about 70 feet from main panel.?

Not enough info to provide an answer that's correct.

How are you running it, in conduit, or are you using cable?

Does it go underground, does it go through very hot areas such as an attic?

Regards, Rod.

[Anthony Whitesell]

Copper versus Aluminum and 60 Amp versus 100 Amp.

[Matthew Curtis]

underground through conduit. no attic.

[Rob Russell]

underground through conduit. no attic.

Is this for a detached shop or is it just easiest to run the supply from you rmain panel to the shop outside rather than inside?

[David Hostetler]

Aluminum?!

I thought that stuff was banned...

[eugene thomas]

i would call the local building inspector. when i installed power on my land the guy told me all needed to know about grounding and all. made the inspection so much easier/.

[Matthew Curtis]

detached shop

[Jarrett Vibert]

Your best course of action would be to call your local electrical inspector.

There's far more to correctly running electrical underground then getting the awg correct. I'll have to assume you haven't ran the conduit yet, seeing as you haven't sized the conductors, so direct burial may be a better option for example.

Depending on your location, you may need to consider getting under the frost line.

If there's heavy traffic crossing over your buried line. The inspector will most likely request you to get the lines/pipe deeper in that area.

I've been out of contracting end of the trade for a while now, but anytime we had an installation where anything may be left up to the inspector's discretion and/or personal preference. We simply called him/her in to tell us how they wanted it done.

It's the best way to handle it. Trust me

[Rob Russell]

Well, an underground installation to an outbuilding does complicate things.

You have a couple of choices.

1) Run 2/0-2/0-2/0-2 USER cable which is direct burial. You need to protect it from damage above ground by sleeving it in something like schedule 80 PVC above ground. If you're running across your yard to the shop, you need to bury the cable 24" deep.

2) Run conduit and pull individual conductors, although you're probably stuck with copper THHN/THWN if you go that route - higher cost. The appropriate metal conduit would need to be buried 6", non-metallic needs 18".

You need to check with your AHJ (Authority Having Jurisdiction - aka the Building Inspector) to see if they want ground rods driven out at your shop. This is definitely one where varying locales have different rules.

The reason that you get differing conductor size answers from different folks is that there are a lot of folks who try to apply an NEC table for "Dwelling Services and Feeders" to subpanel feeders. That table allows you to use smaller conductors than Table 310.16 which is the general conductor ampacity table. The NEC specifically states that Table 310.15(B)(6) is for "the feeder(s) between the main disconnect and the lighting and appliance branchcircuit panelboards(s)". You're not running anything from your main disconnect - you're running a large branch circuit from a panelboard so Table 310.15(B)(6) doesn't apply. Now - there are a lot of places that allow people to use that table - erroneously I'd argue.

[Jarrett Vibert]

If you're running across your yard to the shop, you need to bury the cable 24" deep.

2)The appropriate metal conduit would need to be buried 6", non-metallic needs 18".

The above is exactly why I suggest contacting your inspection authority before following advice from those you will not be siging off on your installation.

In my neck of the woods a 36" depth is a minimum. "Appropriate" could mean one of many different things. IMHO, short of ridgid Aluminum conduit, metal should not be considered for burial. Although if you live in a very arid climate, you may get away with something that would normally rot.