12v cable lengh/csa

[chrisreid186]

when installing 12v lights how do you calulate the csa/cable length ?

i know that a 50w lamp would pull 4.16a @ 12volts so cable sizes have to be larger,
but how would you calcuate the maximum length of that cable? assuming your using twin and earth clipped direct ?

thanks in advance

 

[chrisreid186]

but you have less volts to play with, if it makes no differance then why would the 12v cable have to be 2.5 minimum? 1mm can handle 4.16 amps but not the volt drop

 

[Adam W]

Yeah 0.3something volts is going to make more difference if you're supplying at 12v than at 230v.
A driver regulates either the voltage or the current for LED lamps, as opposed to a transformer which steps down (or up) the voltage in relation to what it was supplied at in the first place.
You don't need a driver for halogen lamps.

And yes it would make it a lot easier if they described the cable types in plain English. I've written them in myself.

 

[telectrix]

it's the volt drop you have to worry about. try calculating it for 1.0mm.

 

[chrisreid186]

sorry got the wrong end of the stick thought you were saying volt drop wont make any differance, any ideas what the volt drop limit for 12v is if its not 3 percent?

 

[Adam W]

It's still 3%, which at 12v is 0.36v.
At 230v, 0.36v is more like 0.1%, which is near enough insignificant - you can have up to 3.6v drop, which would make a big difference to a 12v lamp.

 

[Adam W]

We sometimes come across these lamps shinin like smoke ends in the dark novus.
Had an install today with elvs cuttin out.....3 wired into one silly little tranny causin thermal cutout plus scorchin at the terminations.........

Yeah like I said in post #2 they're more conventionally wired one lamp to a locally sited transformer, then you don't have to worry too much about overloading (provided you get the right transformer), or volt drop.

 

[Adam W]

That's a good argument for using 230v halogens rather than 12v ones.