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Old 07-17-2014, 10:25 PM
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voltage drop question

Hey guys,

Supposing you have a 600 ft. run. And supposing you have borderline voltage using 12 gauge cable on the 15 volt tap. And supposing you don't want the expense of going to 10 gauge for the total 600 ft. Does it make any sense to start the run with 10 gauge and then at some point splicing in 12 gauge for the remaining distance?

I'm asking this question for my friend.
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Old 07-18-2014, 08:53 AM
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Yes, that's an acceptable practice. That would reduce the voltage loss. Just be careful not to overload the #12/2.
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Old 07-18-2014, 09:16 AM
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LEDs adding up to less than 50 watts on that entire 600 ft. run.
"My friend" has never dealt with a run that long. Thanks.
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Old 07-18-2014, 10:08 AM
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Hey Phil, You could also mention to "your friend" that you could start with a higher output transformer kicking out 22 volts down that line. That would also help. A word of caution if doing this though, just make sure you know what the top end, input voltage range is on the LEDs your using so you don't exceed it. (It varies slightly from manufacturer to manufacturer) As long as you are not over the top end of the input voltage load of your LEDs, your good to go. You'll have to test the first light on the run with all the LEDs on the run wired up to know, (under full load) to make sure you are in the window. You can also "roughly"calculate it via traditional voltage drop calculations. Tip: When using high output transformers that exceed 15 volts, start testing with lower taps first, (ie. 14v and 15v) and work your way higher as you need to: starting too high and testing could have an adverse effect on your LED if it spikes way over recommended top end input. Better safe than sorry.

Have a great day- Tell "your friend" hello.
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Old 07-18-2014, 10:31 AM
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Tim,
I preferred using the transformer with the maximum 15-volt tap.
I had calculated about a 5.6 volt drop for that run with the LEDs so starting at 15 volts, I would have been borderline by calculation. Of course, the actual voltage drop may have been somewhat different after wiring up everything. Who knows? But I didn't want to be wrong after installing a lot of wire. And yes I considered the possible over-volting of the the LEDs. After a couple sleepless nights, I came up with the idea to combine cable sizes to control the voltage drop. Like I said, the drop was so borderline that even resistance from the number of connections could affect it. We'll see what happens when I do the project.
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Old 07-19-2014, 11:59 AM
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Quote:
Originally Posted by starry night View Post
Tim,
I preferred using the transformer with the maximum 15-volt tap.
I had calculated about a 5.6 volt drop for that run with the LEDs so starting at 15 volts, I would have been borderline by calculation. Of course, the actual voltage drop may have been somewhat different after wiring up everything. Who knows? But I didn't want to be wrong after installing a lot of wire. And yes I considered the possible over-volting of the the LEDs. After a couple sleepless nights, I came up with the idea to combine cable sizes to control the voltage drop. Like I said, the drop was so borderline that even resistance from the number of connections could affect it. We'll see what happens when I do the project.
"borderline", you answered your own question. Put down the 10ga and do it right, why risk it. Sleep well at night.
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