Low voltage cable - exposed on roof

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We have a customer insisting that we can install UL Listed and NEC rated low voltage cabling (i.e. RG59 and 18/2 - CCTV application) exposed on a flat roof. They want us to just lay the cable on the roof. I am thinking of several things in the code that would prevent this: (1) support/securing the cable (2) physical damage to the cable. Is there anything else in the code that you are aware of that I can bring to the customers attention?
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
I agree with Larry and Bob...remember this would be a Chapter 8 installation and the rules in chapters 1-7 do not apply.
 

Rover88

Member
You might want to consider the roof itself: if this is a Firestone or Carlisle membrane you can void the roofing warranty by laying cable directly on the membrane

Either use inspection mats or support the cable(s) with a block of wood (like the plumbers do the gas lines)
 

tom baker

First Chief Moderator
Staff member
The NEC is concerned with fire and shock. Your low voltage cable, as it is low voltage, has neither of those potentials. But the NEC does not care if it doesn't work. The cable would have to be wet location rated if on the roof or in conduit on the roof.
Also as mentioned, the UV resistance of the cable must be looked at.
 

mxslick

Senior Member
Location
SE Idaho
When I worked for RCA Service, our CCTV outdoor runs were exposed on roofs and we had no particular issues. I believe the Belden RG-59 we used was UV rated. I know that the cable rarely caused any problems, but the splices and terminations did, despite our best efforts at weatherproofing.

At one plant we had as an account, one camera was on the very top of a storage tank (I hate heights) and another was mounted over a driveway out on a pole spanning two buildings....five stories up. The only way to get to that camera was to shimmy out on that pole in a harness.

On one memorable call, that camera and two others were out..I was not looking forward to having to go out on that pole..but I got lucky. The cameras were out because the power was out in a large portion of the building. Why?

Acid washdown on the fourth floor got into a very large MCC on the floor below..the resulting explosions killed one worker, seriously burned two others and shut down production for a few weeks. I saw the carnage in person, it was amazing how much damage was done.
 
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