Voltage drop in garden lights
General Technical Stuff October 7th, 2011Hi,
We inherited a 12 volt transformer set up in our garden and I’ve recently
had it OK’d for use by a sparky so I’m looking to buy some spotlights – my
question is how do I know what size cable to order for our garden lights?
Thanking you
Paula Turner
October 7th, 2011 at 10:19 am
Hi There
If the run is short you can use a smaller diameter cable.
If it a long distance from the transformer then you need to use larger cable
In the cable specifications you will notice voltage drop per metre. You need to multiply this by the metres distance the last light would be from transformer. This gives you the voltage loss in volts. eg on our middle of the range 6mm garden light cable here http://lighting-store.com.au/lightshop/product_info.php?products_id=952 it mentions voltage drop of 0.0062 V/M that means the voltage will drop 0.0062 volts every metre of cable length from the transformer. If the light was 20 metres away 20 x 0.0062 = 0.124 volt which is fine.
If the voltage drops too much then the garden lights will be very dim. Assuming you are starting with 12 volts then subtract the loss from 12. If you are 11.5 volts and above you should be fine. Any less the globes will be very dim towards the end
I hope this makes sense
Anything else please let me know
Kind regards
Daniel Purser
Lighting Pro Australia
http://www.lightingpro.com.au/catalog
http://www.lighting-store.com.au/lightshop