MV Cable Support

[augie47]

Is there any requirement for multiconductor MV Cable to be secured to Cable Tray on horizontal runs ?

 

[pete m.]

I don't see a requirement for securement in horizontal runs. The only other thing I can think of to look for would be a requirement from the cable manufacturer.

Pete

 

[weressl]

Is there any requirement for multiconductor MV Cable to be secured to Cable Tray on horizontal runs ?

Short circuit bracing, so at fault the won't dance around and jump out of the tray and damaging them in the process.

 

[augie47]

Short circuit bracing, so at fault the won't dance around and jump out of the tray and damaging them in the process.

I agree and am thinking they should be secured but can no documentation requiring at what distances.

 

[weressl]

I agree and am thinking they should be secured but can no documentation requiring at what distances.

That would require calculations and general guidelines can be developed based on that. The MVA withstand rating of the gear it supposed to feed maybe a starting point.

A while ago we had a post about a 1200A fused disconnect(?) that had specific roping/bracing instructions for the incoming/outgoing cables. Bus bracing design that a gear manufacturers design department maybe willing to share with you may offer some starting numbers.

 

[ZZDoug]

There are parts of the code that lead you to believe there is no requirement, and manufacturer documentation will tell you fastening on horizontal runs is only required in seismic or high vibration areas. But if you look under 392.6 it clearly states;

"The system shall provide for the support of the cables in accordance with their corresponding articles."

And in the NEC handbook, the fine print note says;

"Of course, the cables installed within cable tray systems must always be supported to the minimum requirements of
the applicable article."

So you better have a liberally minded inspector to not be tagged if you dont support em. If I recall, most MV cable is also rated as MC, so you are probably talking 6 feet.

 

[weressl]

There are parts of the code that lead you to believe there is no requirement, and manufacturer documentation will tell you fastening on horizontal runs is only required in seismic or high vibration areas. But if you look under 392.6 it clearly states;

"The system shall provide for the support of the cables in accordance with their corresponding articles."

And in the NEC handbook, the fine print note says;

"Of course, the cables installed within cable tray systems must always be supported to the minimum requirements of
the applicable article."

So you better have a liberally minded inspector to not be tagged if you dont support em. If I recall, most MV cable is also rated as MC, so you are probably talking 6 feet.

Cable tray itself provides the required support. FPN is not enforceable. The OP question was about fastening or securing the cable within the tray. The Code appears to be silent on that issue, however other requirements, such as manufacturers installation instructions or engineering requirements may require it.

 

[markstg]

NEMA VE2 is the standard for installing cable tray, and therein it describes strapping cables to cable tray rungs in horizontal runs and the spacing of the straps. Not a code requirement though, just a good practice.

 

[weressl]

NEMA VE2 is the standard for installing cable tray, and therein it describes strapping cables to cable tray rungs in horizontal runs and the spacing of the straps. Not a code requirement though, just a good practice.

The Code requires you to follow manufacturers instructions. Tray manufacturers routinely refer to the VE2 as installation instructions. Thus following VE2 is required by the Code when the Manufacturer identifies that document as the installation instructions.

 

[markstg]

The Code requires you to follow manufacturers instructions. Tray manufacturers routinely refer to the VE2 as installation instructions. Thus following VE2 is required by the Code when the Manufacturer identifies that document as the installation instructions.

Since the wording uses "can" and "should" seems it is not a requirement of VE2.

 

[ZZDoug]

FPN is not enforceable.

Everybody knows this, technically. But, the fine print notes are there to clarify the intent of the code, and in gray areas such as this inspectors cant help but be influenced in their decisions by what the FPNs say. Thats just reality.

When it says "The system shall provide for the support of the cables in accordance with their corresponding articles", you could argue what the word "support" means. You can say its supported by the rungs when its just lying there. But article 300 tells us that cables (and practically everything else) must be "securely fastened in place". On the other hand, when you run romex through a hole in a stud its considered supported, even though its not actually fastened and is essentially just lying there. So I can see both sides of this.

But if I was the inspector, you would be tying them down.

 

[ZZDoug]

NEMA VE2 is the standard for installing cable tray ... it describes strapping cables to cable tray rungs in horizontal runs ... Not a code requirement though

Hey Mark, the document you are talking about only refers to single conductor cables in regards to horizontal runs. And it is clearly wrong when it says fastening (for them) is not a code requirement, single conductors (for AC circuits) must be fastened, see 392.8(D). Its the part right before that, 392.8(B), that talks about multi conductor cables. It says "In OTHER THAN HORIZONTAL RUNS, the cables shall be fastened securely" so it certainly does sound like horizontal runs dont need "fastening" and that maybe just lying there is considered adequate support.

In any event, like you say, it ought to be done anyway.

 

[markstg]

Hey Mark, the document you are talking about only refers to single conductor cables in regards to horizontal runs. And it is clearly wrong when it says fastening (for them) is not a code requirement, single conductors (for AC circuits) must be fastened, see 392.8(D). Its the part right before that, 392.8(B), that talks about multi conductor cables. It says "In OTHER THAN HORIZONTAL RUNS, the cables shall be fastened securely" so it certainly does sound like horizontal runs dont need "fastening" and that maybe just lying there is considered adequate support.

In any event, like you say, it ought to be done anyway.

Yea, I see what your saying. Anyway, I've seen feeder cable that was shorted end up "out of the tray". Fastening the cables also gets the installers to train the cables better, less interweaving, getting better tray fill. But that's just me, and all the electrician's I work with at the plant.

 

[weressl]

Everybody knows this, technically. But, the fine print notes are there to clarify the intent of the code, and in gray areas such as this inspectors cant help but be influenced in their decisions by what the FPNs say. Thats just reality.

When it says "The system shall provide for the support of the cables in accordance with their corresponding articles", you could argue what the word "support" means. You can say its supported by the rungs when its just lying there. But article 300 tells us that cables (and practically everything else) must be "securely fastened in place". On the other hand, when you run romex through a hole in a stud its considered supported, even though its not actually fastened and is essentially just lying there. So I can see both sides of this.

But if I was the inspector, you would be tying them down.

..and I would be asking you:

1. at what distance intervals?
2. by what approved means?
3. how 'secure' should it be?
4. do you have a specification that answers ANY of the above questions?
5. Any of your answers should be supported by an approved documentation.

Don't misunderstand me, I firmly believe that the cables should be tied down. But there is no way to determine what the requirements are in any quanitive or qualitive way.

 

[ZZDoug]

Laszlo, I think the phrase "in accordance with their corresponding articles" answers all of your questions.

It seems we all agree that a case can certainly be made that they dont have to be fastened, but that they should be regardless.

 

[markstg]

..and I would be asking you:

1. at what distance intervals?
2. by what approved means?
3. how 'secure' should it be?
4. do you have a specification that answers ANY of the above questions?
5. Any of your answers should be supported by an approved documentation.

Don't misunderstand me, I firmly believe that the cables should be tied down. But there is no way to determine what the requirements are in any quanitive or qualitive way.

And if you asked me those questions I would say:
1. read the facility specifications and standard detail drawings that were issued to you as part of the Issued for Construction package.
2. same as one.
3. same as one.
4. Yes.
5. I agree

I agree with your last statement, which is why design specs and drawings must be produced, to direct how it is to be done. Otherwise, don't expect it to be done without a change order.