Low Voltage Bridge Lighting

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Michael53

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North Texas
The organization I work for is installing precast concrete panels on an existing bridge structure. The 4" thick panels are to contain lighting equally spaced across the face of the bridge. (Not a part of the contract) There will be a 3" void between the precast panels and the bridge rail, (flat concrete surface). I've been tasked with installing the lighting system for the bridge.

The problem is, the precast company is not willing to guarantee the spacings close enough to allow me to install conduit and junction boxes on the face of the rail before the panels are placed. Once the panels are in place, there will be no way to manipulate a conduit system behind them, and seal-tight would not have a junction box to terminate in.

So I've decided to use low voltage fixtures and a 277v primary (voltage of existing circuit) Q-Tran transformer, thinking I could use 2 conductor flexible cord to connect the lights on the secondary side, (including using simple plastic connectors) not unlike Malibu Lighting from a box store.

The B-K fixtures require a 2 1/2" leave out, and the hole would be large enough to fish the flexible cord and connect it through the openings. The fixtures come with a 5' flexible cord attached to them.

I know the correct size low voltage conductors to use, the right transformer and voltage taps... unfortunately I don't know if the cord installation is NEC legal. Maybe I'm over thinking it, or just not willing to accept the fact the cord may need to be in a conduit system, (that's exactly what I'm trying to avoid), but any ideas, alternative suggestions or positive comments would be appreciated. The fixture is a B-K "Core Drill" "Step Star" item.

Questions:
1. Is the flexible cord installation code legal?
2. If the installation is legal... can anyone please recommend a good flexible cord? (I find it hard to believe that Home Depot landscape lighting cord is the correct wire to use.)
 
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Thanks for the reply Larry,

The span is 115' and will be cast in four sections. I couldn't think of a good way to tie the conduit runs togther at each end of the sections. (and include expansion couplings) Additionally, the way the panels will attach to the ends of the rail won't allow a conduit from where the first j box would have to be placed back to the transformer/supply. There's only a 1" gap between the panels. I also thought about drilling through the back side of the rail through the "leave outs" and running the conduit exposed on the outside of the structure... but because of aesthetics abandoned the idea.

I know all this may be simple to some but I'm use to running conduit and hardwire. The need for low voltage flexible wiring (without a raceway) has me baffled.
 
This kind of project should not be designed on the fly by the electrical contractor. It should be engineered and the fabricator should be given specifications that will ensure that the parts can be wired per the specificaiton and by the method called out on the drawings.
 
You are in for a lot of work.
Take a look at 250.20(A)(1).
Since your supply is over 150v you have to ground the secondary of each transformer.
And then 250.30 states a grounding electrode conductor, minimum size 8 AWG to a grounding electrode.
Are you sure you want to use 277 volt primary?
You can't use the cord either.
 
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