Powering large LED installation

Question

I'm building a circuit to feed about 200 feet (non-linear) of LED lighting. These are 24V LEDs, with each 16 foot roll consuming 72 watts DC. I want to size my power supply to handle the entire installation at full brightness, which is about 38 amps. In reality, the installation would only be running at about half brightness.

I have two 20A and two 15A feeds available at the panel. In my mind, the most logical (and safest) option would be to halve the installation and use two power supplies and the 20A feeds to power each half.

I was told I could use one power supply and balance the current over the two 20A feeds (assuming both circuits were on the same leg), however I don't believe that's safe.

Any suggestions?

Edit: I've included additional information about the setup.

Below is a simple schematic of what I'm looking to achieve. Note that I left out data signal wiring to simplify the schematic, as I'm just interested in powering the LEDs for now:

For power, I'd was looking at something like a Mean Well 600W 24V 25A AC/DC Switching Power Supply

Answer 1

Is there any reason you think you need supplies from two 20A breakers?

It could be because you want dual-redundancy, so if one breaker trips, you still have half the lighting.

But is shouldn't be that you need it for the current draw. Doing the maths, it looks like you have 200/16 x 72 = 900W of lighting. That's 37.5A at 24V. If you could get perfect power supplies, that would be 24/120 x 37.5 = 7.5A total at 120V. But perfect power supplies don't exist. If we assume 85% efficiency, that would give 7.5/0.85 = 8.8A. Still easily low enough to put on a single 15A or 20A breaker.

Answer 2

If the 200ft is linear, you'll need very thick wires to carry the high current from the power supply all the way to each strip. If wires are too thin you'll get voltage drop and uneven brightness. You can calculate voltage drop knowing current and wire resistance.

Using several lower current power supplies could end up costing less, it depends on how the strips are installed, and thus wire length.

You also have to decide if you want to use PWM dimmers, or a dimming power supply. Note the latter usually won't dim to 0%, which is inconvenient, and you only get one zone per power supply.

Once this is done, you can think about mains wiring, but in this case it's "only" 900W so one circuit will be enough. Note mains wiring gauge should match the breaker rating to avoid fire hazard.

Answer 3

With the power supply you noted, its 600W output means you will need two of them, and the data sheet says it draws 12A on a 120V input so one 15A or 20A circuit is inadequate. You need two circuits. I suggest you use two 20A circuits with #12 cable, exactly as in your diagram, because the data sheet also says the startup current is 30A. And you should test whether your full, 100 foot load won't pop the 20A breaker on startup and plan accordingly.

Note, the same company makes a 1500W 24V unit with 17A input that would fit on one 20A circuit. IDK if that would be better for you, it may even be worse eg if some of the 24V feeders were then twice as long.

You should also calculate whether #18 wire will suffice. With 40ft I think you'll get a 1 or 2 V drop, which ought to be ok but if you're buying all that wire and all those LEDs you should make sure! Test it.