Canopy lighting

[champion]

I am providing 120vAC power to a 30ft x 30ft canopy located about 200 feet from the front of a car dealership building. The Canopy will have 12 400w metal halide lamp fixtures designed for wet locations. (Huntington series HT2 surface mount units). Each fixture will be 120v AC operated but comes with a ballast quad tap option (120,208,240,277,480). The service is 120/208v 3ph and am unsure about some code requirements for this application.
I have options to provide the power I need and I am undecided as to which would be the best option for safety and design.
Since the lighting load is continuous,I was thinking of providing a 50amp single pole 120v brkr at the main power panel and tapping all lights to this ckt.(400w x 12 x 1.25 / 120 = 50amp overcurrent protection.
---or--- provide a 208v 3ph 4w ckt and connect 4 lignts on each phase lead with a 3 pole 25 or 30amp overcurrent device at the main power panel. 400w x 12 x 1.25 / 208 x 1.732).
Any suggestions would be very much appriciated.
Article 600, sign lighting requires external disconnects located within sight of a sign but this canopy is not really a sign.
Will this ckt require a disconnect located near the canopy?

 

[steve66]

Re: Canopy lighting

I don't think you need a disconnect at the canopy.

Per 210.23 (B), 30A branch circuits can only be used with fixtures haveing a "heavy - duty lampholder". Could someone please tell me how I know if a fixture has a "heavy duty lampholder". I have never seen a shop drawing that states "heavy duty lampholder".

I would think the three phase option would be best. Place each fixture on 208V line to line (4 on A to C; 4 on A to B; and 4 on B to C). 400 * 12 * 1.25 = 6000Watts. 6000/(208*sqrt(3)) = 17 amps. You could use a 20A breaker and #12 wire.

I notice 25amp circuits aren't listed in 210.23. Does that mean you can't have 25A branch circuits for lighting?

Steve

 

[jim dungar]

Re: Canopy lighting

Just a word of warning. 400W fixtures draw more than 400W. Use the ballast input amps for your calculations.

For example, 400W MH @ 120V:
Constant wattage autotransformer - 4A
Pulse start - 3.8A

All mogul base sockets are "heavy duty lampholders".

 

[jerryb]

Re: Canopy lighting

Steve, you might check you math. Also you can't put more than 16 amps on a 20 amp branch circuit with a continuous load.

 

[steve66]

Re: Canopy lighting

I have checked my math. If I am missing something please fill me in.

It wouldn't have more than 16A per branch (I multiplied the load by 1.25).

But also see Jim's post. If PF is less than about 0.85, then you'll need a 4th circuit to stay below the 16A per phase.

Yes, but what is a Mogul base? Can HID or fluorescent fixtures have a mogul base, or does it apply only to incandescant?

Steve

 

[jerryb]

Re: Canopy lighting

Steve, my mistake on the math. I was leaving out the 125%. Jim is right about the actual load on each fixture. I would normally allow 465 watts for each 400 watt luminaire.

465 x 12 = 5580 watts = 15.48 amps @ 208v, 3-phase (if all three phase are equally balanced). 15.48 x 125% = 19.36 amps for a minimum branch circuit size.

Sorry for the confusion.

Power factor on a typical "good" quality HID or fluorescent fixture should be .9 or better.

Mogal base lamps are typical for 250 watt HID luminaires or larger. These are larger diameter bases to accommodates the larger lamps. These are all consider heavy duty.

 

[champion]

Re: Canopy lighting

Thank you all for your input.
It will all for your input.
At this stage of the job I am working on the preliminaries and only had the wattage of the lamp that the customer is wanting to use.
Just as soon as I get the information on the ballast I will use the amp rating on the ballast. Thanks again.
I was computing at 480watt just for safe pre-engineering.
480 x 12 lamps at 208v 3ph.
What I did was compute 16amps max on the 20amp 3ph ckt due to continuous ltg load.
16 x (208 x 1.732)= 5764w.
5764/12 = 480w.
5764/(208 x 1.732)=15.9 amp load continuous x 1.25 = 19.9amp.
Hope my math is ok.