Down Lights

[Ziggy]

Gatiep,

Could you expand your example further for me and tell me the load the lighting circuit will see (at 240 Volts), or is it the same as the light - being 2 Amps. If thats the case our average lighting circuit is 16-20 Amps meaning I could only install 8 to 10 down lights per circuit?

Thanks,

Zig

[Ben from Vic.]

Thanks for your help Gatiep, I have some more difficult questions.

Presuming we are talking about a 12 volt 50 watt downlight, what is the draw on the system in 240 volts (When you convert the power usage from 12 volts to 240 volts)?.

Or, put simply, how many could you plug into a power point before you overload it (not what I plan to do)?.

I'm led to believe that they use less that 10 watts at 240 volts (or about 0.045 of an amp (i think))

Ben

[gatiep]

Ziggy & Ben

Unfortunately one cannot do a straight conversion as there is a transformer involved, changing the voltage from 240 Volt to 12 Volts. That is the case with the 12 Volt downlights, there is a factor involved depending on the efficiency of the transformer.

The formula involved for calculating the current ( amps ) drawn is:
Volts x amps = watts or Watts/Volts = Amps

In the case af a 12V x 50 Watt downlight the amps drawn will be
4.167

((( I am looking at a 12 Volt 50 wat downlight with its own transformer and the input is 240 volts ( no amperage given) the output is 11.4 Volts and the current that it delivers is 3.95 Amps. So if we look at the Formula Volts X Amps = Watts ( 11.4 x 3.95= 45.03 Watts. This makes me doubt the "Chinese" Specs of 50W. )))

To keep calculations simple lets stay with the example of the 12 Volt 24 Watt lamp drawing 2 Amps.

If we have a load of 24 Watts and the Voltage is 240 then the amps ( current) drawn will be 24/240 = 0,1 Amps.

This is correct if we have a 100 % efficient transformer. Therefore if we increase the volts 20 times ( from 12 Volt to 240 Volt) then we devide the Amps by the same factor, ie 20 , giving us 2/20 = 0.1 amps

The transformers used are not 100% effective, probably only 75%.

Therefore the amps drawn at 240 Volt side of the 12 volt transformer will be higher and probably in the region of 0.133' Amps.

Sorry for the longwinded post, but I don't know how to put it any other way.

I hope this answers your questions


Have fun................................keep turning

[Ben from Vic.]

Gatiep

No need to appologise, the post was quite helpfull.
Given, as you say, that it all hinges on the efficiency of the transformer, I guess that the only way to find the actual drawer would be to put a muiltimeter onto it, and even then it would likely be different depending on the price you paid for the transformer.

And to answer Ziggy's question assuming a 0.15 amp drawer, a 20 amp circut could power up to 130 low voltage downlights

Ben

[Ziggy]

Thanks guys, does clarify things a little