What is the advantage of using 240v single phase lighting vs. 120v lighting. The wattage is still the same if you use P=IE. On the 240v circuit, the voltage is higher and the current is lower. But, you are still limited to 2000 watts on a 20 amp breaker and 1500 watts on a 15 amp breaker. So you really haven't gained anything. Is there any advantage that I am missing? I am involved in a job where 10 400 watt metal halide lights are going to be hung and we are trying to decide on what voltage to use. Thanks!

On the 240v circuit, the voltage is higher and the current is lower. But, you are still limited to 2000 watts on a 20 amp breaker and 1500 watts on a 15 amp breaker.

Wait a minute.

240 x 20 = 4800 watts

120 x 20 = 2400 watts

Hit it with the 80% for continuous load and your looking at 3840 or 1920 watts.

Bob Badger Construction & Maintenance Electrician Massachusetts

Plus, if you're doing parking lot lights where the distance of the wire comes into pay, you'll need to consider voltage drop. One way to combat this is by using a higher voltage.

And I MUST say, Ron, you were in class, and paid attention. Good man!!!

10-400 watt MH, with avg ballast loss is approx. 4600 watts. kind of tough to get it on 1 circuit. It's over a tad at 277, would be good at 480, but based on Ky's post he has 120-240 only

You taught us well, John. I impressed a customer of mine the other day by showing him how much he was paying for the lights I installed in his back yard using the technique you taught me. It goes without saying (but I will anyway) that the customer was impressed.

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

Scott " 35 " Thompson Just Say NO To Green Eggs And Ham!