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Re: 120vs240 lighting #73922 01/06/07 09:48 AM
Joined: Aug 2005
Posts: 64
K
kyelectric Offline OP
Member
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!

Work Gear for Electricians and the Trades
Re: 120vs240 lighting #73923 01/06/07 10:15 AM
Joined: Jan 2006
Posts: 558
R
Rewired Offline
Member
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

Re: 120vs240 lighting #73924 01/06/07 04:20 PM
Joined: Jun 2005
Posts: 821
S
ShockMe77 Offline
Member
^^
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.

Re: 120vs240 lighting #73925 01/06/07 08:13 PM
Joined: Jan 2003
Posts: 4,391
I
iwire Offline
Moderator
Quote
Just because 240 volts is twice the voltage of 120 doesn't necessarily mean that there'll be less voltage drop.

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.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: 120vs240 lighting #73926 01/06/07 10:19 PM
Joined: Jun 2005
Posts: 821
S
ShockMe77 Offline
Member
Thanks iwire!


So using a higher voltage is more effecient.

Re: 120vs240 lighting #73927 01/07/07 12:53 AM
Joined: Dec 2005
Posts: 860
R
RODALCO Offline
Member
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 ).


The product of rotation, excitation and flux produces electricty.
Re: 120vs240 lighting #73928 01/07/07 01:14 PM
Joined: Aug 2001
Posts: 7,520
P
pauluk Offline
Member
Quote
Just because 240 volts is twice the voltage of 120 doesn't necessarily mean that there'll be less voltage drop.

Quote
The drop in volts will be the same for the same load and wire size.
[Linked Image]

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.

Re: 120vs240 lighting #73929 01/07/07 01:20 PM
Joined: Jan 2003
Posts: 4,391
I
iwire Offline
Moderator
Paul you are right and I agree. [Linked Image]

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.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: 120vs240 lighting #73930 01/08/07 01:07 AM
Joined: Oct 2006
Posts: 745
E
EV607797 Offline
Member
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?


---Ed---

"But the guy at Home Depot said it would work."
Re: 120vs240 lighting #73931 01/08/07 06:08 AM
Joined: Jan 2003
Posts: 4,391
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iwire Offline
Moderator
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.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
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