Using 2/0 Wire for a 60 Amp Sub Feed
lindenboy
| Posted in Construction Techniques on
Trying to help my dad save some money for his pool house: They want a 60 amp sub-panel at the pool house, about 80′ from the house. I have 280′ of 2/0 copper wire.
We decided to have a go, and then I started looking into it today. Clearly the 2/0 will hold the 60 A capacity. But it’s possible, even likely, that the 2/0 won’t fit into a 60 breaker lug. Any way to work around this issue without spending more time and energy than just buying the appropriate #6 3G wire?
TIA.
“It depends on the situation…”
EDIT: Planning on 3-wires + some spare #6 solid copper for a ground.
Edited 8/10/2009 4:30 pm ET by lindenboy
Replies
280' of 2/O copper handy, nice situation to be in. I assume you have TTHN/THWN wire and you are going to run in conduit.
As far as wire size, it depends on what version of the code your area is using (2005 vz 2008). If your area is using 2005, you can use a much smaller (thinner) wire than you would have to if your area adopted the 2008 code.
FWIW, the wire designation is:
E51583 S (UL) 600V AWG 2 CU TYPE MTW or THWN-2 or THHN or GASOLINE AND OIL RESISTANT II VW-1 SUNLIGHT RESISTANT.
Thanks for the comments. Sounds like the best solution has nothing to do with snipping the wires to fit the lug (while it would clearly works, it does feel "wrong" and I'd rather uphold my values to maintain a higher standard that the typical hillbilly : )
As a DIYer primarily (I AM an architect, but that doesn't equate to much in the field), I hesitate to work on electrical to leave it in a condition that would confuse the next guy a few years down the road. It finally dawned on me that he needed 3-wire anyway, and all in all it would require MORE work to retrofit this wire the RIGHT way than to just buy 80' of 3G #6.
I will also suggest the option of trading my 2/0 wire in for the wire and maybe even the sub-panel and some breakers -- I've had the 2/0 on a spool for sale for 1 1/2 years now ($200) but haven't unloaded it yet. This situation sounded like a win-win until I dove into the details.
Thanks, y'all."It depends on the situation..."
L,
Your wire is #2, not the even larger 2/0.
Given that, you may not need splices to downsized wire to fit breakers and lugs. A 60A breaker may very well accept #2 wire. (I'm looking at a Square D 70A that will). And that 70A breaker costs about the same as a 60A, so you could use a 70A breaker in the main panel and an 100A subpanel. Watch the size of the grounding conductor.
But trading the wire for the smaller, proper size is probably still the best solution.
Jim x 3
Oops! Thanks for that clarification."It depends on the situation..."
What you want to do sounds legal ... sort of.
The solid is not really legal in pipe. I doubt anyone will bust your chops for it but itt will be harder to pull. The #6 is OK for your EGC even when you recognize you up sized the ungrounded conductors (OK for 200a).
You can get straight through lugs that will allow you to reduce this to a #4 or so to get in the breaker.
I have seen people simply trim off enough strands so it will fit but that is wrong.
I'm not an electrician, so take that for what it's worth. Maybe Bill or CAP or the rest will come by to set us both straight!
I'd look into a wire splice and splice the large (2/0) into the smaller (#6) at a j-box near the sub panel. Assuming that the #6 is sized appropriately, there's no problem running oversized on the majority of the run.
By the way, If the pool house isn't physically connected to the main house, I'm pretty sure you need to drive separate ground rods for the new subpanel, even though you also need the ground connected from the sub back to the main as well.
-t
Of course another alternative is to take the 2/0 to a supply house and offer to trade it for some #6 -- see what kind of deal you can make.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
The simplicity and elegance of your suggestion remind me that it is easy to overcomplicate things.
"It depends on the situation..."
He can make the splice in the sub panel cabinet.
You could have a junction box outside the panel where you use an approved splice then reduce to a short stub of #6 that runs into the panel.
The other way (if your inspector approves) is to snip a few strands from the 2/0 so that it fits in the lug. You'd still need to provide a proper connecting/bonding method to the panel.
...or you could just give me the 2/0 stuff and I'll trade you for 280 ft. of #6 NMD ;)
Scott.
Edited 8/10/2009 7:51 pm by Scott