While the higher Voltages are desired in Lighting Circuitry designing - primarily due to the fact that Lighting Circuits are LOOOOOOONNNNGGGG Distances and lengths,
There are a few things to consider first:
<OL TYPE=1>
[*] Lamp Screwshells having Voltage to Ground,
[*] Running Lighting Loads directly from Photocells.
</OL>
Typically, when driving Lamps &,or Ballasts from L-L Circuitry, the Lamps' Screwshell will have the System's Voltage to Ground -
unless:
* The System is a Corner Grounded Delta, and the Grounded Conductor is used as "Common" to the Lighting Fixtures,
or
* The System is an Ungrounded Delta (then the Voltage to Ground on either side of the Circuit is anyone's guess!!!)
These issues are more along the lines of "Typical Design Issues", but nevertheless are something to ponder.
< Opening Can O' Worms Controversy Per MWBC >
A typical Design strategy I apply when dealing with Parking / Exterior Lighting, and the Project has a 120/240V 1Ø 3 Wire System available, is to design these loads across 3 wire circuits - with the loads as balanced as possible.
Example:
Light Standards (Poles) contain Two Luminaires - each being 250W MH.
2 Circuits to each Pole.
The Voltage Drop on these Circuits will be applied as if the Luminaires are driven at 240 Volts, so it really helps out on long circuit runs.
Each L-N Circuit is designed to carry a maximum of 50% Capacity at 100%, or 1200 VA without LCL (10 Amps).
With an LCL adder, the maximum load values would be 12.5 Amps, or 1500 VA.
The Voltage Drop would "Naturally" be figured at 240 Volts, as long as the loads remain balanced.
So, as a suggestion, you might consider going the Multi Wire Branch Circuit (MWBC) route on these Fixtures.
< Closing Can O' Worms Controversy Per MWBC >
Adding more things to think of!
Scott35
