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Parking lot lights. #130810
02/20/07 02:59 PM
02/20/07 02:59 PM
aldav53  Offline OP
Joined: Aug 2001
Posts: 545
Chandler, AZ USA
Will be installing 5 parking lot lights at a church parking lot. The City requires 24" deep, PVC ok. The Lights are 120 volt probably High Pressure Sodium 400 watt. Just wondering how many circuits to run for the 5 lights with the transformer draw in there too. I believe they boost the voltage and frequency up on those lights. Correct?

The Golden Rule - "The man with the gold makes the rule"
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Re: Parking lot lights. #130811
02/20/07 03:59 PM
02/20/07 03:59 PM
ghost307  Offline
Joined: May 2005
Posts: 934
Chicago Illinois USA
I'd run (3) circuits out there.
(2) for the lights and (1) for the 120V load that they forgot to tell me about.
Remember to run a ground wire to the lights (in addition to any ground rod you have).

Re: Parking lot lights. #130812
02/20/07 07:37 PM
02/20/07 07:37 PM
Scott35  Offline

Broom Pusher and
Joined: Oct 2000
Posts: 2,708
Anaheim, CA. USA

I can offer suggestions which might be considered, but since there are quite a few possibilities, the details would be astronomical.

So, here is something basic and simple:

Typically, the total Line VA for most High Power Factor HIDs in the 400 Watt HPS line would be 480 VA.
At 120VAC, this equates to 4.0 Amps per Luminaire (Ballast + Lamp total package draw).

The commonly used Ballast configuration for the 400 Watt HPS - and the 400 Watt MH too, is the CWA (Constant Wattage Autotransformer).

These Ballasts are able to tolerate +/- 10% Voltage Variations, with about 5% Lamp output variations.
Beyond the 10% input variations, Lamp regulation begins to suffer dramatically, so Voltage Drop is an issue to consider first and foremost.

Many CWA Ballasts are the "Quadri-Volt" types, which have input Voltage taps for:

If the Lighting is to be controlled by multi-pole Lighting Contactors, consider using L-L Voltage for the Fixtures, across different Circuits.


Two - 20 Amp, 2 Pole Circuits from Panelboard.
3 Fixtures on one 2 Pole Circuit,
Remaining 2 Fixtures on the other 2 Pole Circuit.
#10 THHN cu. to first Pole for each 2 Pole Circuit.

If 120VAC is a non-negotiable thing, then break up fixtures across at least 3 Circuits, using no smaller than #10 cu. - unless the fixtures are so close, there will be no Voltage Drop issues.

Good luck.


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Re: Parking lot lights. #130813
02/20/07 11:01 PM
02/20/07 11:01 PM
aldav53  Offline OP
Joined: Aug 2001
Posts: 545
Chandler, AZ USA
2 lights per 20 amp circuit sounds good, with the # 10 wire.

The Golden Rule - "The man with the gold makes the rule"


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