Elevated Water Tank

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wirestu

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We are presently wiring an elevated water tank. Our contract calls for us to install two obstruction lights on the top of the elevated water tank. The lights flash white during the day and red at night.

There are control panels mounted in the base of the tank. We have installed conduit from the base to the top of the tank. On the top of the tank there is a 25' diameter circular handrail. The obstruction lights are mounted to flanges on the top of the handrail.

The obstruction lights have an 18/8 shielded cable between the controller and the fixture. It is UV resistant Black PVC. The 8 conductors carry DC voltages up to 200 VDC.

Our question is can this cable be supported to the handrail brackets with Mae Wests since the area is accessible to only authorized personnel? If we install non metallic liquid tight flexible metal conduit around the handrail, would a 25' length be acceptable if it is supported every three feet?

Thanks in advance for your assistance.
 
ron said:
Like these kind of elevated water tanks?
Click to expand...

I believe the FAA dictates warning lights on tall objects. Most of the tanks in ron's picture don't have lights-- they're surrounded by taller objects less than a certain distance away.

Also notice-- several of the buildings are more modern than others-- both cold and hot water tanks! :roll:
 
wirestu said:
We are presently wiring an elevated water tank. Our contract calls for us to install two obstruction lights on the top of the elevated water tank. The lights flash white during the day and red at night.

There are control panels mounted in the base of the tank. We have installed conduit from the base to the top of the tank. On the top of the tank there is a 25' diameter circular handrail. The obstruction lights are mounted to flanges on the top of the handrail.

The obstruction lights have an 18/8 shielded cable between the controller and the fixture. It is UV resistant Black PVC. The 8 conductors carry DC voltages up to 200 VDC.

Our question is can this cable be supported to the handrail brackets with Mae Wests since the area is accessible to only authorized personnel? If we install non metallic liquid tight flexible metal conduit around the handrail, would a 25' length be acceptable if it is supported every three feet?

Thanks in advance for your assistance.
Click to expand...

I believe you'll need 78-1/2 feet of cable to ring the tower. Fewer if you can get to the lights without going the long way 'round.
 
Image result for composite water tank


The tank is similar to above.

Concrete pedestal and steel tank on top.
 
What is the outside diameter of the cable? Does it run from one light to the other or are there two runs?

I don't think you are going to find "Mae West" clamps small enough. For something like this I would be looking at cell or transmitting tower methods and hardware to attach your cable to the handrail.

-Hal
 
The cable has a diameter of .45". We were going to install a plastic click on 1-1/2" strap on the handrail and bolt a 1/2" click on strap with a bolt to the other click on strap. If it is a code issue having the cable exposed, we would use 1/2" LTFNMC in the click on straps.

Here is a link to the straps http://www.aimedia.co/media/spec-sheets/QUICKLATCH.pdf

We are concerned about using the LTFNMC as a conduit system as its length will be over 35' long.
 
I have used the click it straps and worked on many elevated water towers. What ever you install will need to last 50 + years, to all weather conditions. Will the cable jacket last 50 years? Same with the ltnmfc. Some ltnm connectors are nylon (t&b) and may last longer. Clic its are ok, but dont hold the conduit very securely.
And use ss hardware.
 
wirestu said:
If it is a code issue having the cable exposed...
Click to expand...

That's another question. What does the jacket and manufacturer say about running the cable exposed? I have a feeling that it's like a traffic signal cable and not covered by the NEC. But I'm not sure it has to be. I also have a feeling that it will be OK to run without conduit.

But this is NYC, yes? They have their own rules.

-Hal
 
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