I am hoping to get my LED rope lights wired up in the near future, anyway. I have a controller that handles 3 strips of the LED lights. I've heard that you can try to daisy chain some of the strips together, but you run the risk that by the time you get to the end of the connected pieces, their may be power or color changing signal loss. So....

I am connecting the 3 long strips to their own set of 4-wire "ports" on the controller.

Now for the question:
If the normal wire used is 18 gauge for each (4-wire per "port"), can a person use two 24 gauge wires (IE: a single pair from Cat5 wire) for each of the 18 gauge runs?

Cat5 wire for those that don't know consists of 4 pairs (8 runs) of 24 gauge wire.

*) 18 gauge wire is 1.024mm thick

*) 24 gauge wire is 0.511mm thick

*) two 24 gauge wires is the same amount of copper as a single 1.022mm thick wire.

I have a spool of Cat5 wire at home were I could, for example, take the white/blue and blue/white pair, strip the ends, twist the ends together and use that, however I don't want to run the risk of messing anything up. I doubt that heat will be an issue since this is pretty low voltage stuff (12 volts total into the controller, 5 amps out total, that is split among 3 strips).

Would it work safely?

I have no idea.

But I can't wait to again learn from your experience.

Remember - Pictures.

i think that double or half the current capacity is a difference of 3 gauge numbers: from 18 to 21 is half, and vice versa.
the reason is we can't use the wire diameter, it's the surface area of the wire ends that counts.
doubling the wire diameter is 4 times the surface area and 4 times the current capacity.
two 24 gauge wires in parallel is equivalant to one 21 gauge wire.

I don't think that's right. Don't you have to calculate the volume of the cylinder (wire)?

Which is - I think - what JB said.

Edit: So, based on JB, you'd need 4 24's to equal 1 18.

Yeah, that does make more sense. Guess I will be buying some wire...

I'd be surprised if CAT5 couldn't handle the power of these LEDs, unless you have a crap load of them. When you say 5 amps is that just what the power supply is rated for or what the combined LED's actually draw?

The specs are as follows:
Input Voltage:12 Volts DC
Output Voltage:12 Volts DC
Power (Watts):60 W
Current (Amps) Output:5 A

IR Music Controller 60 Watt 3 Ports With Remote for Color Changing LEDs,3322RGB

Although looking at my Amazon order history, I bought 3 of these and I was using one of those included 4 amp power supplies when I tested it a couple of months ago.:
16.4 Ft RGB Color Changing Kit with LED ...rs, 2034rgb Kit

They were an all in one package by themselves, but testing them, even with the IR sensors close to each other, they responded with slightly different delays to commands, plus sometimes one wouldn't receive the remote command. Hooking them up to the IR Music Controller meant a single IR "eye" to aim at, and then all were controlled exactly at the same time.

Those specs appear to be just what the power supply is capable of. Would need to figure out what the LEDs actually draw to know for sure. I'm just making an educated guess when I say the CAT5 would work.

In theory, I'm sure that CAT5 might work but the problem would be if there's a fire. I'm pretty sure it's not fire rated and probably not to code. If insurance gets involved, it's possible they can deny a claim because of a code violation.

This is why I disconnected some of the lighting in my house when I purchased it 2007, after finding ceiling lights wired with 12 ga speaker wire. Granted it was for standard AC lights that are usually Romex, not the low voltage for your case. But I didn't want to risk it.

I decided that I am just going to use a bunch of 14gauge wire I have on a spool. If the crown molding is large enough, I will run two sets of wire for each strip of LED lights as they currently exist. By that, I mean that the wiring is rated for in-wall applications too, so it has a protective outer sheathing. If it is too bulky, then I will take the outer sheathing off and just run the pairs that way.