24V RGB LED Setup - Cable & PSU Question

[dancematic66]

Dear all,

I work for an exhibition company and manage the technical side of things there.

As a new feature for a booth concept we need to setup some 24V RGB LEDs to backlight some stretched fabric.

The PSU that I am using is ACDC 24V 13A.

The RGB controller unit that I am using allows 3x3A circuits before having to use a repeater coupled with another ACDC PSU of suitable rating.

The RGB ribbon uses 14.4W per meter, 5m = 72W/24V = 3A per 5m roll (We intended on using the full capacity of the controller).

Basically I am trying to source suitable 4 core cable online however most data cable rating is a low amperage and the draw on our setup will be around 10A.

On TLC I have found 1.5mm 4 core flex 16A used for central heating systems etc.. They also have a 1.0mm version but is only rated at 10A.

I'm worried about using the 1.0mm just incase anything went wrong in the circuit, the cable would be 3A under the PSU rating (Even though the PSU should only be sending out 9A to the controller)

Am I right in thinking that even though it is only 24V the potential draw from the LED ribbon through the controller will be 9A max +/- 5% from the PSU that can allow a total of 13A +/- 5%.

Should I go with the 1.5mm cable so the wiring is rated slightly higher than everything else?

Should I just go with the higher rated ACDC 24V 13A PSU for tolerance or should I just use the ACDC 24V 10A PSU and use the 10A Cable?

Thanks for your help (Sorry if this does't make sense.. )

 

[telectrix]

use the 13A PSU so as to be certain of not overloading. then you need cable that's rated in excess of the actual current, as you have 3 x 3A circuits, each cable run only needs to be 5A cable.

 

[dancematic66]

Hi Telectrix,

Thanks for the advice!

What about the 4core which will run from the controller to a repeater as in this attached .pdf

The repeater will have another 13A PSU attached to it, will the 5A cable from the controller to the repeater get overloaded? (Or not because the second set of 3x3A circuits will run their current from the PSU attached to the repeater)

Thanks for helping!

View attachment productattachments-files-r-g-rgb-rp_specification_pled.pdf

Also I'm thinking that 4x 4 core cable probably won't fit into the output terminals of the controller. If this is the case should I just use a short section of 4 core cable rated above 13A with a terminal connection on one end which is big enough to receive the bunches of cable running to the LEDs/repeater?

 

[telectrix]

it's too small to make out clearly, but as i see it the 1st psu is powering 3 strips, each 3A and signalling the repeater/s which itself has a mains fed psu , again supplying 3 strips at 24V, 3A. so each cable to the strips is only 3A. as you have more than 1 feed in a multicore cable, that reduces the capacity somewhat, so to be safe 1mm 4 core is more than adequate .

 

[dancematic66]

Hi Telectrix,

again thanks for the advice, I will use a 1mm 4 core.

I don't understand this though:

'as you have more than 1 feed in a multicore cable, that reduces the capacity somewhat, so to be safe 1mm 4 core is more than adequate.'

And I would like to

 

[telectrix]

it's because you have more than 1 current carrying cable in close proximity to each other. both circuits will produce a certain amount of heat, so cable cooling is less than for a single circuit. there are correction factors for this in the regs., but in your situation, as the 1.0mm is more than adequate to carry the design current, it need not worry you. a simile is 2 or 3 hot water pipes close together. they will stay warmer for longer than a single pipe with lower ambient temp.

 

[dancematic66]

Ahhh, so if the cable I used was only rated at 3A and there were 2/3/4 of them close together. The heat build up would reduce the cable to a certain degree?

But because the 1mm is way over a 3A pulled by each 5m strip the degradation caused by any heat need not be worried about?

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What I am uncertain of is what current will be pulled between the controller and the repeater? Will this be low current signals telling the repeater what the controller is doing?

 

[telectrix]

as far as i can tell, the connections feeding the repeaters are just signalling. each repeater has a mains powered PSU to handle the load of the strips.

 

[dancematic66]

That's what I thought, thank you for confirming!