LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I can zip tie uf wire to the beams? Good to know. Never ran across this situation before. Use to wiring houses with general crawls and slabsBeam clamps and zip ties are your friend next time.
There are two separate issues one is fill based on the size of the conductor and the raceway the other is derating due to more than 3 CCC's in the raceway. They really have nothing to do with each other.Oh but I see your point. So technically it's not heat even though they say it is? So confusing
Because its underneath a trailer that has a steel bottom. nothing to staple to.
I still dont understand the 3 CCC you keep mentioning. are you saying the ground is a current carrying conductor?There are two separate issues one is fill based on the size of the conductor and the raceway the other is derating due to more than 3 CCC's in the raceway. They really have nothing to do with each other.
He is not saying that you have 3 CCC, he is saying that derating starts at 4 CCC. And the EGC is not a CCC at all. The neutral in an MWBC typically is a CCC, but under specific circumstances (e.g. full boat) it is still not counted for derating purposes.I still dont understand the 3 CCC you keep mentioning. are you saying the ground is a current carrying conductor?
Oh but I see your point. So technically it's not heat even though they say it is? So confusing
What do you mean by breathable?I could. I have 2 junctions in the crawl at fs boxes If i put 4 in (2 on each box) that would make every end breathable. Would that work?
How far of a gap should I leave between each pipe and the fs box? Enough to get a strap within 8 inches?It is heat related. The number impacts the way the way the conductors twist and turn around each other in the conduit. After 3 conductors it becomes likely that 1 conductor may always find itself stuck below the other conductors and therefore not be able to dissipate heat as well.
As far as using the widest part of the elliptical cable, as infinity said, it is about the cable being free to turn and twist as it is pulled through the conduit without being damaged.
Can you replace at least 1 TA with a cable clamp, so you have a bunch of glued together physical protection items rather than a conduit run?
I thought the point of having a cable clamp was to help dissipate heat since it would be enclosed. I'm confused. I'm trying to reply to so many different post lolWhat do you mean by breathable?
Yep, both heat and chafing are accounted for.Right here:
300.17 Number and Size of Conductors in Raceway. The number and size of conductors in any raceway shall not be
more than will permit dissipation of the heat and ready installation or withdrawal of the conductors without damage to the
conductors or to their insulation.
As far as derating for more than 3 CCC's in a raceway the NEC doesn't care if it's ½" or 6" conduit, you get no credit for the additional air in a larger raceway.
I am not sure it's a mixup. There is no pratical application where you'll have say 25 CCC's and the conduit radius is so large that they all lay flat in the conduit. The common scenario is that some CCC's will be surrounded by others thereby creating a heat "issue", hence derating. Why the # 3, I dunno.Code mixes everything up into a 'simplified' set of rules to follow. If you look for corner cases you will break the physics of things and just get confused.
For example, code requires you to 'derate' if you have too many conductors in a single raceway. But there is no allowance made for the size of the raceway. You could have ten #12 conductors in a 1" EMT or a 6" GRC and code would have the exact same derating requirements.
-Jon
And they're two completely different requirements that have nothing to do with each other.Yep, both heat and chafing are accounted for.
sounds good.Enough to get a strap within 8 inches?
That's what is mentioned a few times. Two separate issues wrapped up into the same "fill rules". And at least from my perspective, they do have something to do with each other, at least within that NEC version, because the fill rules tell the reader s/he must run some math on two things when sticking wires and cables in a raceway/conduit.And they're two completely different requirements that have nothing to do with each other.