Repair/Modify LED strings

[rlilly]

I came across an informative write up on LED strings that will make a great how to. :
http://www.ciphersbyritter.com/RADELECT/LITES/LEDLITES.HTM

[kostyun]

It is a good site, but, does lack some information in regards to sealed LEDs, and also full wave LED sets.

[rlilly]

It was helpful to me as I've been repairing some LED strings lately, some of which were in 4 & 5 lamp sections. In approaching the repair with an incandenscent mine set, I'd completely forgotten about the LED polarity. So with the jog to the mind set and polarity adjusted, voila!

It was also interesting to read the discussion about the 3 amp fuses you find in the LED strings that come from their incandenscent predecessors. He calculates that 25 LED strings can be daisey-chained as opposed to the 3 string incandescent limit and stay within fuse ratings.

[kmc123]

Oh how nice that sounds!!! 25 in a series!!!
I may switch earlier than I thought :)

[ben]

Oh how nice that sounds!!! 25 in a series!!!
I may switch earlier than I thought :)

Thats what I was thinking!! I am going to see if I can go in with 2 other buddies since one of them wants almost a full sea container full!

Ben

[Macrosill]

......

It was also interesting to read the discussion about the 3 amp fuses you find in the LED strings that come from their incandenscent predecessors. He calculates that 25 LED strings can be daisey-chained as opposed to the 3 string incandescent limit and stay within fuse ratings.

The load of the LEDs may be within the current rating of the fuses but lets not forget about voltage drop. The smaller the wire the greater the resistance. The greater the resistance the higher the voltage drop over distances. With 25 sets connected end to end the length would be about 400 feet, assuming a 16 foot length per set. To keep things simple I will simply state the calculated voltage drop based on a 2 amp load using 20 awg conductors. Without taking anything else in account, such as ambient temperature or extension cords, the voltage drop would be 16.12 volts. That means a supply voltage of 103 if starting with a 120v supply. The NEC allows a 3v drop maximum. That would require 12 awg conductors.

What does all that mean? It means a heck of a lot for inductive loads, such as motors. It does not mean much for lighting other than the lights would be dimmer than ones with shorter feed lengths.

[ErnieHorning]

I’m all for keeping things simple, but realize that only the very first string would be carrying the full 2 amps. Because the strings are in parallel, each successive string would carry 80 mA less then the previous one.