I have rarely used Smurf, or ENT. I have a job coming up where it would really come in handy to get a couple of dozen circuits thru a very low attic crawlspace. Looks like I can fit up to 13 #12 AWG THHN's in a 3/4". This would mean 3 runs, 8 circuits apiece (using shared neutrals & 1 grounding conductor). After de rating I would still be good for 21 amps. Question is, anyone here ever put 13 (stranded) 12's in a 3/4" Smurf? The runs will be straight and about 75 feet.
I don't think I have ever tried that many but I have done quite a few. Here in the land of 3:12 attics with a foot of "blow in", smurf is pretty handy stuff. The Carlon guy gave us a pitch on Smurf a while ago and he says you have your best luck if you strap it down straight and tight and strap all curves to hold the shape (not "belly"). Then you tape a "bullet" on the end and push the wires through.
BigB, To be honest, I do not like smurf tubing. We had around 200 feet of 1/2" laying around in the shop. It was never outside, just old from sitting in the shop. It would crack and was very brittle. When you would swing it lightly, it would crack in half. Otherwise, I think you are fine as long as you apply the derating factor in there.
I am surprised at that. Maybe it is a "cold" thing. I have a piece of 3/4" sleeving the steering cable on my boat and it has been in the sun and salt water for 10 years. I have it on the trailer now and it still seems to be doing OK
He calculated fine, assuming that this is a three-phase installation. That would allow one neutral for up to three circuits. Thus for 8 ccts. : 3 ungrounded conductors 1 neutral 3 more ungrounded conductors 1 more neutral 2 final ungrounded conductors 1 final neutral 1 bonding conductor --------------------- 12 total conductors in conduit
Even single phase comes up with 13 (2 hots and a neutral times 4 plus EGC) and that is the max in table 9 for #12 THHN in 3/4 ENT. If this is really a straight shot and the ENT is pulled tight enough not to belly it should go in OK.
Yes it is single phase, 2 hots to a neutral, one grounding conductor, comes to 13 conductors, 8 of them counted as current carrying.
Ran 4 runs today by myself, took me 6 hours (told you it was tight up there). Got them nice and straight, no "bellys". came out to 60 feet each.
My helper and I will pull in the conductors tomorrow then I'll report back.
Brian Gibbons, thst stuff must have been REALLY old or defective. The stuff I got is tough as can be. I have a roll of 1/2 inch thats 5 years old, still tough. I wouldn't be afraid to use it for a tow rope!