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





RE: Lighting a parking lot - W/sq.ft rule of thumb?
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.
RE: Lighting a parking lot - W/sq.ft rule of thumb?
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?
RE: Lighting a parking lot - W/sq.ft rule of thumb?
RE: Lighting a parking lot - W/sq.ft rule of thumb?
RE: Lighting a parking lot - W/sq.ft rule of thumb?
RE: Lighting a parking lot - W/sq.ft rule of thumb?
Regards,
Sense
RE: Lighting a parking lot - W/sq.ft rule of thumb?
RE: Lighting a parking lot - W/sq.ft rule of thumb?