Voltage and current flow theory. Led lights

[Mr S Parks]

Voltage and current flow theory.

It's a beautiful day today South of Edinburgh but I know it's all Gona change soon......

Anyway, I'm installing 12v led strip lighting(for a pretty effect) in renovated buildings. At the first fix stage just now.

The led strip lights can be supplied with single insulated 2 core flex from wholesalers but I'm running twin an earth from a central location within each flat.

The plan is for the 12v led transformers to be located in a central location with the cables radiating out to the light switches and led strips.

Wrt step up/step down transformer theory etc is there any problem with eg 12v and 10A flowing from transformer to said led tape/strip light via 1.0mm twin an earth?

I assume current carrying capacity tables based on 230v. All cables run withing thermal insulation.

Hope above makes sense and any learned help much appreciated.

 

[Geoff1946]

Only you know what length/type and hence current consumption of LED strip you are installing, or how far away you are putting the drivers, BUT beware!

There is obviously no problem from the point of view of cable heating, but volt drop will have a major effect on the brightness of the LEDs, so consider resistance.

Just think, a couple of volts dropped from a 230 volt supply is around a (negligible) 1%, whilst lost from a 12 volt supply it's around 20%.

You need to do the arithmetic for your scheme! 

 

[binky]

OK, well there's a requirment ofr a CPC in the supply cable regardless. A 6A MCB will supply roughly 1.5kW, so size you FTE according to installation method and de-rating fcators. The LED driver may output 10A but isn't drawing 10A in the first place ( I suspect more like 50W ie roughly 0.2A) .

 

[Geoff1946]

If I've understood correctly the OP is using his 1mm T+E on the low voltage side. i.e between the driver and the LED strip.

At a quick estimate I reckon if there is, (EG) 10 metres of 1mm twin cable, and a 10 amp load there will only be about 8 volts left at the load end.  In practice, of course , the theoretical current of the LEDs will drop too, but so will their light output.

It may be possible to use drivers with remote sensing, but by the time you've added that in you may as well run a heavier cable in the first place, or more likely move the driver close to the strip.

 

[binky]

it's not a 10Amp load,  it's a driver that outputs 10 Amps at 12v.

 

[Bruspark]

Voltage and current flow theory.

It's a beautiful day today South of Edinburgh but I know it's all Gona change soon......

Anyway, I'm installing 12v led strip lighting(for a pretty effect) in renovated buildings. At the first fix stage just now.

The led strip lights can be supplied with single insulated 2 core flex from wholesalers but I'm running twin an earth from a central location within each flat.

The plan is for the 12v led transformers to be located in a central location with the cables radiating out to the light switches and led strips.

Wrt step up/step down transformer theory etc is there any problem with eg 12v and 10A flowing from transformer to said led tape/strip light via 1.0mm twin an earth?

I assume current carrying capacity tables based on 230v. All cables run withing thermal insulation.

Hope above makes sense and any learned help much appreciated.

There can be an isssue with this arrangement as the transformer still has to supply the required power (you give 12v at 10A as an example which is 120 watts) over the cable to the actual LEDs.

120W is a heck of a lot of LEDs but going with that example, whatever the voltage, you need ‘10A in insulation’ rated cable and even then the voltage drop may also be a problem

Before running a load of expensive copper around I’d say re-think your plan, run 1.5mm T&E to the transformer at each LED location and only step down to 12V once you’re there

 

[Andy™]

There can be an isssue with this arrangement as the transformer still has to supply the required power (you give 12v at 10A as an example which is 120 watts) over the cable to the actual LEDs.

120W is a heck of a lot of LEDs but going with that example, whatever the voltage, you need ‘10A in insulation’ rated cable and even then the voltage drop may also be a problem

Before running a load of expensive copper around I’d say re-think your plan, run 1.5mm T&E to the transformer at each LED location and only step down to 12V once you’re there

think the job is probably already done by now...

 

[Bruspark]

You are surely right .

How TH did that come up in new posts ?????

 

[Admin 7]

I don't know why it would be in new posts, but I have locked it from further replies.