How do you calculate total run length in a parallel led puck light circuit?

Natrix66

Joined Apr 16, 2021
2
I've been hearing two different answers to this and thought I would ask the experts. Do you total up the entire length of wire including all the T-offs in order to get your total run length? Or do you just add the distance from your power source(fusebox) to the furthest Light in the run, with the distance form said light to the grounding point? I'm running six .25 amp(1.5 amp total) led puck lights in parallel on a 24v system. I would like to include a couple '2-way' light switches but I'm concerned the extra wire required would put me over my run length limit with the 16 gauge stranded wire I have installed.

sghioto

Joined Dec 31, 2017
2,395
Do you total up the entire length of wire including all the T-offs in order to get your total run length?
I would.
100 ft of #16 two conductor cable has a total resistance of less then 1 ohm. I don't see a problem unless the runs are extremely long.

geekoftheweek

Joined Oct 6, 2013
692
I would think only the longest run from power to light would be the length to be concerned with for the most part. Think of it more as separate wires to each light than tees. You add all the lights for the total current, but after you start to tee off there will be less total current through the wire after each tee.

MisterBill2

Joined Jan 23, 2018
9,305
To get the wire length measure the distance to the farthest light, and tha actual circuit length is twice that. But with using #16 wire voltage drop in the wire will not be a problem.

Natrix66

Joined Apr 16, 2021
2
To get the wire length measure the distance to the farthest light, and tha actual circuit length is twice that. But with using #16 wire voltage drop in the wire will not be a problem.
Thankyou for the reply MisterBill. Another question if you don't mind. When I install the switches, do I need to put the break in the circuit before the lights? Or can I put the break anywhere on the main power(or even ground) run?

BobTPH

Joined Jun 5, 2013
3,690
Not related to your question, but, is you driver a constant current type? If it is, putting lights in parallel is a no-no.

Bob

MisterBill2

Joined Jan 23, 2018
9,305
Thankyou for the reply MisterBill. Another question if you don't mind. When I install the switches, do I need to put the break in the circuit before the lights? Or can I put the break anywhere on the main power(or even ground) run?
Interesting question about which side to switch. The system is a 24 volt system which means that the rules for mains connected systems do not apply.
There are some considerations that do apply, though. If one side of the 24 volt source is connected to a physical ground, then often it would be best to switch the other side. But there is also the consideration of overcurrent protection, usually fuses. Most often the fuse protected side would be the switched side.
The one suggestion that I will make is to be consistent with which side is switched, to avoid confusion when you or somebody else works on the system in a few years.

Tonyr1084

Joined Sep 24, 2015
6,269
I would like to include a couple '2-way' light switches but I'm concerned the extra wire required would put me over my run length limit with the 16 gauge stranded wire I have installed.
By "two way" do you mean switches that can turn the string on or off from either switch? If so, that's commonly referred to as a 3 way switch setup. If this is the case, the extra wire will not change the results. Only the active line will be active (makes sense) the other wire is just sitting there doing nothing until it is switched over to.

I'm planning a rewire of my garage. There used to be one switch by the main door controlling two of the four lights and another switch by the service door controlling the other two. Always a pain in the neck to have to go to both sets of switches to turn lights on or off. So instead I'm planning a FOUR WAY set of switches. One switch by the service door with two more switches by either side of the main door. That's so you don't have to cross the garage to turn the lights on or off.

In either case, only the active line needs to be factored into the equation.