LED Wiring Calcs

[TCH]

I'm planning to install some RGBW +WW around the ceiling of a small bathroom room.
Data is:
Length 10M in total
24V
10W/M

By my calcs that's 8.33A so I'll need a min of 10A rated cable.
I'd like to use a single multicore flex such as YY 7 core 1.5mm to keep things neat and well within the cable rating - I may split the run into two to reduce the load and use 1.0mm.

My questions are:
1) Is flex OK to use from the controller/driver? Flex length no more the 5M.
2) YY 7 core only seems to come in earth plus black numbered cores. Is this OK to use?

This is what I'm considering using:
http://www.expert-electrical.co.uk/...-6-core-earth-lapp-olflex-numbered-cores.html

Cheers,

Tim

 

[SimonH2]

For something like this, the limiting factor may be volt drop.
AT 240V, if you lose (say) 0.6V in a circuit then that's only 1/4 of a % of the voltage. But with a 12V circuit, it's more like 5%, and for LEDs which don't "light up" until about 7V, that's potentially about 10% reduction in light output ! That's why, on low voltage halogen installations, you'll can see some apparently very oversized cables if the transformer isn't right next to the fittings.

So you should really, really try and get your drivers as close as is practical to the lights.

Now you need to look up the volt drop for the cable you are looking at and the current involved to see if it's a factor.

 

[TCH]

Thanks Simon,

Great tip. I'll split the load and can probably get the run down below 2 metres.

Cheers.

 

[bernardgreen]

There is a complication. If the driver is a constant current driver then the current in the cable between driver and LED elements will be set by the driver and will not affected by cable size and length. With constant current drivers the voltage drop along the cable is not critical unless it is greater than the maximum voltage the driver can produce.

 

[SimonH2]

True, and I'd forgotten about those. But then he's not using CC LEDs - sounds like "sticky tape" LEDs on a roll fed with CV (Constant Voltage) and each group of LEDs has a current limiting resistor.

 

[TCH]

True, and I'd forgotten about those. But then he's not using CC LEDs - sounds like "sticky tape" LEDs on a roll fed with CV (Constant Voltage) and each group of LEDs has a current limiting resistor.

Yep, using sticky tape stuff.

 

[ban-all-sheds]

In a bathroom.

Shall we organise a sweepstake for how long it lasts before it starts to peel away?

 

[SimonH2]

Actually there are some really good adhesives these days. As long as the surface is properly clean and dry, I see no reason it won't stick like brown stuff on a blanket.

 

[TCH]

In a bathroom.

Shall we organise a sweepstake for how long it lasts before it starts to peel away?

Your "concern" is noted.

It'll be in an ali conduit with clearish strip so it'll stay up there

 

[bernardgreen]

A common failure in those strip is when the solder joints between the LED elements and the copper tracks break or corrode. Overheating and /or condensation accelerate these breaks.

 

[TCH]

Thanks for the top advice guys.