ECN Forum Forums General Topics of the Trade General Discussion Area 120vs240 lighting

iwire, thanks for catching the math error. I was only thinking single pole breaker. But with the 20 amp double pole breaker you can run up to 3840 watts. So all of these replies have helped me determine that using the higher voltage will decrease line losses, increase efficiency, keep voltage drop to a minimun and allow more of the light fixtures on one circuit. Can I run #10 copper and install a 30 amp double pole breaker and put them all one one circuit? Thanks for all the replies!

Off topic a little but why put them all one one circuit??? If that circuit faults out and trips the breaker, you are in total darkness..... Just something to think about...

A.D

^^
I agree. Do at least 2 circuits in case one is having a problem. That's a great design idea.

In any case, if this run to any of the MH lights is over 200' I would suggest using #10 THWN on a 20A circuit breaker. Just because 240 volts is twice the voltage of 120 doesn't necessarily mean that there'll be less voltage drop. It's all dependant upon the size and length of the conductor and there is more resistance in a #12 wire than a #10.

The drop in volts will be the same for the same load and wire size.

The drop as a percentage of the whole will be half as much with 240.

Thanks iwire!


So using a higher voltage is more effecient.

The higher voltage will certainly be the better option for metal halides.

Also put the circuit at least over two or more section fuses, mcb's in case of a cable fault, so at least you can keep half or part of the lights going.

Now these days when streetlights or parking lights are not working, people and councils make a big issue about it because of safety, tagging, unlawfull damage etc.

If you use incandescent lights usually a lower voltage (110 or 24) is better because filament lamps tend to have thicker filaments and last longer. ( for streetlights this is rarely used now these days ).

If the load (in watts) is the same, the current at 240V will be only half that at 120V. So if the size and length (and hence the resistance) of the wire is the same in each case, the voltage drop must be lower, not only as proportion of the supply voltage but also in absolute terms.

Paul you are right and I agree.

That is why I said "will be the same for the same load"

In other words if the wire size and current remain unchanged the the amount of volts lost will be the same at either voltage but as a percentage it will be less.

But, on a single-phase service, using 240 volts for any load will keep it balanced. I have never confirmed this, but I was told by an old-timer (a former boss) that typical electric meters register the load on higher-usage leg as what's billable, even if the other leg has less load. If what he said is true, then wiring as many 240 volt circuits as possible will be the most efficient.

He always said "using a neutral is throwing money into the ground". Wonder if he might have been right?

No meters do not bill both legs based on the usage of one leg.

You pay for what you use be it 120 or 240.

But the balancing is of course better with 240 loads.