volt drop on elv LED wiring

[Gunnspark]

Hi. I'm new to LED wiring and am wondering how to work out volt drop when using 24 volt drivers and 2mm elv cable. The length of run is about 20 metres. I've read that the 4% stays the same as 230v but what would be the maximum length of cable that could be used?

 

[Marvo]

when using 24 volt drivers and 2mm elv cable.

I haven't heard of 2mm cable in any variety. Did you convert to millimeters from an AWG, SWG or BWG size?

 

[Gunnspark]

Definiteley 2mm black elv cable. Just wondered if their is a formula to work out volt drop and maximum cable length?

 

[Marvo]

There is a formula and there are reference tables however 2mm is not in any of my references. Is 2mm the outside diameter of the wire or the cross-sectional area of the conductor?

 

[Gunnspark]

Hi Marvo. I think its csa but cable drum is on site and im at home. Where would i find the formula? Cheers

 

[Marvo]

Vdrop = IR. If it is a 2mm CSA wire you'll need to go to the manufacturers website to get the resistance per meter.

*Edit* For apporximate reference purposes 2mm CSA is pretty close to 14AWG size.

 

[Gunnspark]

your mistaken IxR = volts, not volt drop???????????????????????????????????????????????????????

 

[Marvo]

Oh, okay, in that case use E=IZ for AC

 

[Gunnspark]

Whats E? I'm looking for volt drop in elv circuit. How could you possibly get that from amps (I) x impedence (z)?????????????? I really think your just taking the micky

 

[ipf]

Know all beginners, lol.

 

[Marvo]

Maybe we should go back to the start. You want to work out the volt drop across the wiring (2mmCSA) between an ELV (24v) LED driver and the load ie the LED lamps? Is that correct?

 

[Gunnspark]

correct

 

[Marvo]

Is the output of the LED driver 24VAC or 24VDC?

 

[Gunnspark]

can anyone help or does no one actually know

 

[yellowvanman]

Hi. I'm new to LED wiring and am wondering how to work out volt drop when using 24 volt drivers and 2mm elv cable. The length of run is about 20 metres. I've read that the 4% stays the same as 230v but what would be the maximum length of cable that could be used?

If the driver is a constant current type then volt drop doesn't really matter as long as the LED gets the right current.

 

[Gunnspark]

its vdc Marvo

 

[Marvo]

Okay, so you have a circuit with an LED lamp as the load but the circuit actually consists of three resistances in series. First you have the resistance of the positive wire, then the load resistance then the resistance of the negative wire.


You can find the voltdrop across any of these resistances if you know the current flowing in the circuit in Amps and the value of the resistance in Ohms. This brings us back to the first formula I gave you Vdrop = IR

 

[Marvo]

So, if you can find the datasheet for the 2mm CSA wire you're using you can get the resistance per meter. Then, as Yellowvanman says the driver may be constant current output so you'll need to find the manufacturers datasheet for that as well to establish the output. Once you know the resistance of the wire and the current in the circuit it's easy to work out the voltdrop per meter of wiring.

 

[Guitarist]

You've done brilliantly to keep giving advice Marvo, after some of those comments.

 

[Chris sparky]

I'm sorry, but when you come on here asking for advice, and someone actually takes the time to give you a solution. If you dont get/understand what they're saying you shouldn't then talk to them like they are the idiot.

Fair play to you marvo.

 

[Marvo]

I missed a couple of his posts whilst I was typing, probably a good thing. Not sure what his problem was.