I have a goodly supply of #2 in the form of USE-2 RHH/RHW2. That is nasty-stiff, 7-strand Cu good-for-just-about-anywhere cable. I will have 1" conduit, the run from the subpanel will be 5' -LB- 20' -LB- 18' -LB- 5'. The questions I can come up with include:
*Am I going to rather burn my house down than fight trying to manhandle those cables, and should I be better off purchasing a less-fractious wire?
NEC 338.12(B)(1) states that USE cable, because it's not flame-retardant, may not be used for interior wiring. Type SE can, but not USE. 338.24 requires that bending radius be more than 5 times cable diameter, which is difficult to work with.
*Am I going to be able to stuff those 7 strands into not only the 100A breaker, but also Tesla's lugs?
Any lug rated for the size you're using should be able to use it. You have to make sure torque is right for less strands, though...
*Is THHN easier, marginally easier, no different, or more difficult?
My opinion is that it's slightly more flexible to get it through tight openings, but working with terminations is roughly the same.
*AND...does NEC and/or good practice permit snipping one...two...strands at the lug in order to thin down an uncooperative cable????
No, no, no, no, no!! Snipping a strand reduces surface area by a considerable amount, especially on service-entrance cables!
On edit: my electricians (the Solar City crew doing the PV install right now!) cringed at the sight of the USE-2. I think we'll go something a bit more cooperative....they're also thinking wide-sweep 90ºs will be less onerous than LBs. And using TWO conduits (maybe even 3/4" rather than 1") will be best of all.
Good idea.
Although I will say that I made an LB work with a bit of finagling for THHN #2.
- - - Updated - - -
Right - I'd read your comments on the "pic" thread - thanks, Cottonwood. After writing that I also learned that using two conduits (e.g., L1 + neut. in one; L2 & grd in the second) is a no-no. I can't understand why, but we'll run a single 1 1/4" conduit instead. When I've been faced with one of those REALLY tight lugs in the past, I've snipped some of the strands until I can just persuade the wire to where it belongs.
Bad idea on the snipping strands... I could go through the surface area calculations for you, but you'll find that you lose current carrying capacity (especially on those wires that have only 7 strands or so).
As for conduits, it's primarily for safety, knowing where the conductors are running. All conductors for a branch circuit must be co-located together, including ungrounded (hot) conductors, grounded conductors (neutral), and grounding conductors (ground).
Don't worry, I was able to fit #2 into the lugs fairly easily. It's a bit snug but they will fit.
- - - Updated - - -
Well, #3 should be fine for a 100A breaker, right? I think it's good up to 110A. Even #4 would technically be up to code for 100A (I think), but probably better to use #3 or #2 if you can.
#3 is fine for 100A breaker. While the NEC allows it to carry up to 110A at 90 degree ratings, every termination must be rated at 90 degrees for this. The HPWC lugs and almost every residential/commercial breaker on the market today are rated only at 75 deg C, so the limit is 100A rating (80A continuous load).
There are a good number of electricians who only carry #2 or #4 - the difference is rather negligible in terms of cost and it means another set of spools you don't have to maintain.
