Cable tray fill jurisdiction

[phankins1]

Does the NEC have jurisdiction over cable tray fill where all conductors are 48Volts and below?

 

[hbiss]

Yes. Read through Article 725.

-Hal

 

[dereckbc]

I will take a different spin. If these 48 VDC conductors are part of a 48 VDC plant like those used in a telephone office the answer is NO because it is not premises wiring. We lace them in tight side-by-side and eight deep.

 

[don_resqcapt19]

Dereck,

If these 48 VDC conductors are part of a 48 VDC plant like those used in a telephone office the answer is NO because it is not premises wiring.

How is that not premises wiring?

Premises Wiring (System). That interior and exterior wiring, including power, lighting, control, and signal circuit wiring together with all their associated hardware, fittings, and wiring devices, both permanently and temporarily installed, that extends from the service point or source of power, such as a battery, a solar photovoltaic system, or a generator, transformer, or converter windings, to the outlet(s). Such wiring does not include wiring internal to appliances, luminaires (fixtures), motors, controllers, motor control centers, and similar equipment.

It appears that everything other than wiring that is internal to equipment is premises wiring.
Don

 

[dereckbc]

Don, The DC plants derive from the ac/dc rectifier units which should comply with NEC requirements for the ac input. They are utilization equipment at a point of ac supply (branch circuit) that typically utilize fixed wiring methods. The NEC and DC historically go back to street lighting and dc generation - not DC premises wiring. The NEC does cover some DC on the industrial side.

 

[don_resqcapt19]

Dereck,
While I understand how the NEC rules are typically applied, it still appears to me that all wiring that is not an internal part of the equipment is premises wiring and covered by the code. In your application the output of the rectifier is a source just like a transformer. I see nothing in the code that says it doesn't apply...unless you are the telephone utility and then you are outside of the scope of the NEC per 90.2(B)(4).
I think this is just another unworkable part of the NEC that is for the most part ignored.
Don

 

[dereckbc]

Dereck,
I think this is just another unworkable part of the NEC that is for the most part ignored. Don

You are right about that Don; the industry is fighting hard to keep the NEC out of it, and for good reason.

Here is the hurdle; In a large scale DC plant like 4000 to 10,000 amp range the primary distribution cabling from the battery distribution board ( AC equivalent main panel and feeders) going to the secondary distribution battery breaker bays (AC equivalent of breaker panels for branch loads) can number up to 144 750-MCM cable contained on a single 36-inch cable rack. That comes out to 20 cables wide stacked 7 deep packed like sardines.

So you can imagine the conflicts that causes with article 310. I have only been challenged twice in my career and won the debate by using engineering supervision exception. There are other areas of conflict with respect to cable concentrations. A good example is in switching equipment like Line Concentration Equipment where a single 12-foot long equipment line-up can contain well over 1000 analog or digital cables to be transported from the equipment line-up to the distribution frames.

I don?t have all the answers for the conflicts but what I do know it would be impossible for a Telco to fully comply with NEC requirements from the massive amount of cable involved.