Lighting a parking lot - W/sq.ft rule of thumb?

[itsails]

I need to light a 200' x 400' parking lot with 150W HPS lamps on 30ft aluminum poles, .5 footcandels average maintained, .75 maintenance factor.

1. Is there a W/sq.ft number I could use to determine the approximate load? Want to find out if the existing distribution panel handel the additional load.

2. Is there inrush current associated with the HPS ballasts?

3. I'm running a ground wire with the power, but would a GND rod at each pole be a good addition?

4. I can use 480V or 120V but I seem to remember a post stating that maintenance expect to see 120V for lighting and for safety I should give up the voltage drop benifit of the 480 - what do you think?

I've got the question poised to the lighting rep

 

[fishon]

Some interesting questions with numerous possible answers based upon the given criteria.
1. A .5fc average is pretty common, however the total quantity of pole mounted fixtures to achieve this varies greatly based upon optics, lamp orentation, pole location, etc. A very rough rule of thumb to achieve this is approximately .015 - .02W/sq. ft., which gives approximately 10 poles. A 150W HPS fixture draws around 180VA/Ea. so that will allow for any inrush. Running a ground wire in the underground conduit is a Code requirement and is sufficiant, but if you are in a area which is lightning prone, the added ground rod at each pole is common for added safety. Personally I always opt for the higher voltage due to voltage drop and final installed cost, 120V is just not a good utillization voltage for exterion site lighting unless there is nothing else available. Maintenance people for this kind of equipment should be fully quallified Electricians. Finally a Lighting Rep is nice to have around, but don't let them perform lighting layouts and calculations for you, there job is, after all to sell light fixtures, and it is to easy to fidge input data in a Lighting Program to achieve the desired results. There are numerous Programs out there, many free from the major manufacturers. You should always do your own layouts, and with many of these programs, doing budget quantities only takes a couple of minutes.

 

[itsails]

Thanks for the reply. If VA is anything close to 10x180 VA will have plenty of capacity on the existing panel.

I've looked up some ballasts that make use of capacitors and they spec a start-current of less than steady-state current - inrush may not be a problem.

Any recommendations points to some free lighting software?

 

[fishon]

Lithonia Lighting

http://www.lithonia.com

publishes Visual lighting design software, there Basic edition is free and is very fast to use for budgets, there Professional edition is around $100.00, although if you deal with a Lithonia rep they will generally get it for ou for free. Cooper Lighting also has a program called Luxicon, again the thing to do is deal with the rep, if you want it for free. Any of these programs will do a good job of lighting layouts based upon your criteria, giving W/sq. ft.& Average fc as well as min/max ratios.

 

[hbendillo]

A 150 watt light fixture on a 30' pole is not very efficient. You would do much better using a 400 watt fixture on each pole. Less fixtures, less poles, less pole bases, conduit, connections, etc. Usually something as small as 150 watts is used for small street lanters on 12' to 14' poles.

 

[borntodeal]

Fishon, some very helpful tips and the website was very helpful. I'm looking to light a parking lot at my motel property and it is roughly a 180' square. The one thing we are trying to figure out is how many of these lights we will need and their placement. Perhaps you might have some thoughts if I were to fax you the diagram of the building from a recent property survey?

 

[Senselessticker]

I use Visual from Lithonia often, but for more complicated lighting calcs (free) I use Luxicon by Copper Lighting. Just call your local sales rep and he/she will be glad to send you a copy. I have heard however, that Luxicon does not work well with Windows XP if that is your OS.

Regards,

Sense

 

[fishon]

I had the same problem with Luxicon, it just doesn't work on XP. I actually use AGI32 for detailed lighting calculations, but it's not cheap, I find the free ones from Lithonia and Cooper to be fine for a quick calculation to obtain quantities, but not for anything else. Over the years I have found that the programs furnished by Lighting Manufacturers tend to skew the results slightly in favor of their products (imagine that), it's not always significant, but it's there, and when your Lighting Calculations on a project are a part of the Record Documents, they better be accurate, you might have to defend them in Court.

 

[fishon]

Cooper Lighting has just released a Patch for Luxicon, and it now works on Windows XP