100 meter cable for 240 watt lights. Requirements and suggestions?

dougsfarm · Jan 27, 2015

I have a large chicken house about 100 meters (100 yards) from my house. I need to run an electrical cable for lights (4 60-watt bulbs). As the house is mobile (I would typically move it 20 meters in one direction or another), the cable will not be fixed in place.

Knowing virtually nothing about electrics and electrical cables, I was wondering if it would be OK to just use an ordinary extension cable or just buy 100m of ordinary cable? I have heard that using a thicker cable will reduce resistance and consequently the amount of energy consumed by the cable itself. However, no idea of how much power the cable would use, and whether for a 240-watt load if the energy saving of a better cable justifies the higher cost of the cable. The lights would be running an average of 4 hours per day, so total energy consumption would be about 1 KW per day.

Any advice or suggestions would be appreciated.

Marvo · Jan 27, 2015

Hi Doug.

For circuit design purposes we don't worry too much about the energy consumed by the cable, we worry more about the voltage dropped across the cable which results in a lower voltage at the far end. The two would however go hand in hand but they also kinda cancel each other out because with an undersized cable the reduced voltage at the load means it consumes less energy. With a load of only 240 watts even a 1.5mm SWA cable 100m long will have less than 2% which is more than adequate. SWA cable is armoured which would be better for using on the surface, extension leads and normal installation cables aren't UV stabilised and will easily get damaged.