metallic conduit used as physical protection

[electrofelon]

I can't find the references for the following, can someone help me out?

Say I have a cable assembly or PV wire that I am protecting a 6 foot section of from physical damage with, say, IMC.
1) does derating apply?
2) does the IMC need to be bonded?
3) does conduit fill apply?

Thanks

 

[Carultch]

I can't find the references for the following, can someone help me out?

Say I have a cable assembly or PV wire that I am protecting a 6 foot section of from physical damage with, say, IMC.
1) does derating apply?
2) does the IMC need to be bonded?
3) does conduit fill apply?

Thanks

1. Yes. Exceed two feet in length, and derating applies.

2. Yes. All conductive materials that do not intentionally carry current need to be bonded.

3. Yes. Gotta model the wire fitting inside the conduit somehow. And this is the best way. Exceed 2 ft in length, and 53%/31%/40% fill limits apply. ~75% diametral fill. Less than 2 ft in length, and you can fill up to 60% fill (except for two wires), which is about a 90% diametral fill.

 

[Smart $]

1. Yes. Exceed two feet in length, and derating applies.

2. Yes. All conductive materials that do not intentionally carry current need to be bonded.

3. Yes. Gotta model the wire fitting inside the conduit somehow. And this is the best way. Exceed 2 ft in length, and 53%/31%/40% fill limits apply. ~75% diametral fill. Less than 2 ft in length, and you can fill up to 60% fill (except for two wires), which is about a 90% diametral fill.

So if I use plumbing pipe for physical protection, do I have to comply with fill and bonding requirements?

FWIW on #2, I point you to 250.86 Exception #2 regarding other than service conductors.

 

[infinity]

I agree with Smart on #2 no bonding required for short sections of raceway that are used for physical protection.

250.86Exception No. 2: Short sections of metal enclosures or
raceways used to provide support or protection of cable
assemblies from physical damage shall not be required to
be connected to the equipment grounding conductor.

 

[electrofelon]

I agree with Smart on #2 no bonding required for short sections of raceway that are used for physical protection.

thanks infinity and Smart$, that was one of the ones I was looking for but couldnt find. Ok so how about a section of metalic raceway protecting PV wire, do I have to bond or not? I guess it comes down to if PV wire is a cable assembly or a conductor?

3. Yes. Gotta model the wire fitting inside the conduit somehow. And this is the best way. Exceed 2 ft in length, and 53%/31%/40% fill limits apply. ~75% diametral fill. Less than 2 ft in length, and you can fill up to 60% fill (except for two wires), which is about a 90% diametral fill.

What about the note 2 in chapter 9?

 

[Smart $]

...

What about the note 2 in chapter 9?

Pretty much irrefutable that conduit fill rules do not apply.

 

[Carultch]

So if I use plumbing pipe for physical protection, do I have to comply with fill and bonding requirements?

I don't see why that would allow you to do anything less than what the NEC permits for dimensionally-equivalent listed conduit. If anything, I would be more conservative in fill and bonding requirements, in the unlikely event that I ever have to get away with using plumbing/fence pipe/fittings in a pinch.

Plumbing pipe is still metal, and thus still needs to be bonded if part of an electrical system. And it's not going to be any easier to pull that wire through it, since plumbing pipe interiors do not have the same finishes as listed conduit.

 

[Carultch]

I agree with Smart on #2 no bonding required for short sections of raceway that are used for physical protection.

How many inches is "short"? 24 inches or less?

 

[ActionDave]

How many inches is "short"? 24 inches or less?

Short is short, it's not something you can put a number on. I think the wording in 250.86 is left vague for a reason.

 

[kwired]

I don't see why that would allow you to do anything less than what the NEC permits for dimensionally-equivalent listed conduit. If anything, I would be more conservative in fill and bonding requirements, in the unlikely event that I ever have to get away with using plumbing/fence pipe/fittings in a pinch.

Plumbing pipe is still metal, and thus still needs to be bonded if part of an electrical system. And it's not going to be any easier to pull that wire through it, since plumbing pipe interiors do not have the same finishes as listed conduit.

The whole key here is this is a sleeve for physical protection, not a complete raceway system - and because it isn't a racewaqy it is just a metal tubing - general raceway rules do not apply to it. Water pipe used for cable sleeve is no longer water pipe either - it is now a sleeve for wiring protection.

Because it is not a raceway system conductors installed in it need to be part of a cable assembly or other conductors that are not required to be installed in raceway methods.

The fact they are all effectively "bundled" where run in the sleeve means they likley will be subject to ampacity adjustments just like bundled cables run through bored holes in framing members are.

Conduit fill doesn't apply to a sleeve- but if that sleeve is long it may not be a bad idea to take it into consideration just to make the pull easier and avoid conductor/cable damage.

Bonding the sleeve isn't required but doesn't hurt anything either.

 

[iwire]

Plumbing pipe is still metal, and thus still needs to be bonded if part of an electrical system.

Plumbing pipe cannot be part of an conduit system, plumbing pipe is just a long hole you might put wire through.

What are the fill requirements for putting cables through a hole in a stud?

Well those same rules apply to a pipe used as a sleeve.

 

[infinity]

Plumbing pipe cannot be part of an conduit system, plumbing pipe is just a long hole you might put wire through.

What are the fill requirements for putting cables through a hole in a stud?

Well those same rules apply to a pipe used as a sleeve.

I agree, there is a difference between a conduit system and a sleeve. The NEC is silent on the defintion of a sleeve but has guidelines as to what constitutes a conduit system. I don't see where in the NEC that it states that the rules for a conduit system apply to a sleeve.

 

[Carultch]

Plumbing pipe cannot be part of an conduit system, plumbing pipe is just a long hole you might put wire through.

What are the fill requirements for putting cables through a hole in a stud?

Well those same rules apply to a pipe used as a sleeve.

I would use the "nipple rule", and fill up to 60%. It represents about 90% of the diameter fill, if you were to attempt to jam the wires wall-to-wall.

I'd probably do that anyhow, without even making a calculation.

 

[Carultch]

I don't see where in the NEC that it states that the rules for a conduit system apply to a sleeve.

Other than the potential for your AHJ to see the sleeve as a conduit system, even though you see it as a protective sleeve. It is easier to defend it, if you've built it according to conduit construction rules.

 

[iwire]

Other than the potential for your AHJ to see the sleeve as a conduit system,

The AHJ cannot see a sleeve as a conduit system.

A conduit system is required by the NEC to be mechanically continuous between enclosures and use electrically listed components.

A sleeve is neither of those things.