Landscape Lights and Voltage Drop

[IntegrityOutdoorLighting]

Hi Guys im new here and look forward to learning more as well as helping when I can.

1st off a 500' loop is a no no. You gotta break that up into multiple runs. Your load on your secondary breakers would be way to high as most pro line and contractor transformers have a limit of 25a on the output commons.

720 w for me would probably be at least 5 runs. You can probably actually save wire by not doing the loop, get more even lamp output as well as be more effeciant and not to mention extend lamp life.

Optimum voltage at the fixture would be 10.6 to 11.5 and its important to check it at the fixture under load.

Another good method of wiring no one mentioned is the Hub method. Run your 10ga or 12ga lead from the transformer to a "hub" then group 4-6 fixtures together and bring em to the hub and make 1 splice. Some high end low voltage fixtures come with or are avalible with 25" of 16ga lead wire.

THe T method is also handy where you bring your main from the trans in around the middle of the run and place 3 lamps on each side of your main line (3 lamps is a generic number its gonna vary depending on lenght and wattages)

Dont daisy chain unless its just a few lights or a short loop.

Hope this helps some

Billy
www.integrityoutdoorlighting.com

 

[IntegrityOutdoorLighting]

620.12?



If you have no bulbs installed there will be no voltage drop at all.

.

Wire itself does have its own resistance therefore will offer its own voltage drop. Just the wire alone if a long run will cause you to have to up to a higher tap.

Example a 60w lamp load run at 180 ft of 10ga wire will require a 14v tap. 1.94 voltage drop)

The same 60w lamp load run at 40 ft would only require the 12v tap. only .43 voltage drop there. THe wire CAN play a roll in the overall voltage drop so do not try and calculate your drops on your lamp load alone.

Its much more extreme with smaller wire.

Good rule of thumb for low voltage wire is run 12ga for anything under 100ft or 100w. it will run up to a max of 192w or 16a but your wasting yout transformers power

10ga for over 100w or 100ft to be effiecient. up to 288w or 24a MAX but we generally wont go over 150w on it.

Over that 8ga is expensive. Cheaper to run 2 strands of 10 or double up other wires.

While the recomendations are not even close to the max capacities it allows for expansion of the system easily later and also creates an energy effecient system (good selling points!)

 

[iwire]

Wire itself does have its own resistance therefore will offer its own voltage drop.

There will be no voltage drop if there is no load.

The amount of voltage drop is as related to conductor size as it is to the load carried by the conductor.

Voltage Drop = Current x Resistance, usually written as VD = I*R

Using that formula see how much voltage drop you get with 0 current.

 

[iwire]

Over that 8ga is expensive. Cheaper to run 2 strands of 10 or double up other wires.

'Doubling up' wires this small is an NEC violation.

 

[IntegrityOutdoorLighting]

ok maybe im missing something and forgive me if i posted false info. I just took a 12v tap from a trans and connected it to a 500 ft roll of 10ga wire. I measured the voltage at the tap... 12v... measure voltage at the other end of the wire. 11.2 nearly .8 drop in voltage... am i missing something or is this not a drop in voltage due to the resistance of the wire ? I could be wrong... I am here to learn.

On the issue of doubeling up... This is the first time I have heard that its a violation in low voltage lighting and would love to know where I could find the proper code so I could bring it to other well know low voltage installers who reccomend this and use this method regularly.

Maybe I just worded it wrong? A long run in CONJUNCTION with X amount of load may require you to use a higher tap in low voltage lighting. wire does indeed have its own resistance. My example above with the same loads but different lenght runs shows it. maybe voltage drop is the wrong term but resistance certainly does increase.

 

[JohnJ0906]

NEC 310.4 Conductors

 

[LarryFine]

If you have no bulbs installed there will be no voltage drop at all.

So if you where to connect the bulb-less circuit to a 15 volt tap you will read 15 volts anywhere on the circuit.

Once you start installing lamps the the voltage will drop.

Wire itself does have its own resistance therefore will offer its own voltage drop. Just the wire alone if a long run will cause you to have to up to a higher tap.

There will be no voltage drop if there is no load.

The amount of voltage drop is as related to conductor size as it is to the load carried by the conductor.

Voltage Drop = Current x Resistance, usually written as VD = I*R

Using that formula see how much voltage drop you get with 0 current.

ok maybe im missing something and forgive me if i posted false info. I just took a 12v tap from a trans and connected it to a 500 ft roll of 10ga wire. I measured the voltage at the tap... 12v... measure voltage at the other end of the wire. 11.2 nearly .8 drop in voltage... am i missing something or is this not a drop in voltage due to the resistance of the wire ?

But, in your experiment, you do have a load: the meter itself.

You will learn something about this forum: when it comes to theory, we're a tough bunch.

 

[IntegrityOutdoorLighting]

Yes im learning that quickly and as I said Im here to learn too.. I want to better myself and the low voltage industry as a whole through doing things the right way. I do understand now what your saying about my meter being a load.

The longer runs of wire will in fact make your voltage drop under any given LOAD requiring the possible use of a higher tap. Back to the original post he planned to do something dangerous and a waste of time as it would not work at all.

Can someone please cut and paste the actual code 310.4 so i can pass this info on to thoes who have told me to use multiple stands ?

Thanks for pointing out all my mistakes instead of the good info I provided Other than my few tidbits of poorly worded info I would like to think I do haveplenty of good info especially on design and installation.