Low Voltage Track Lighting question

I have four low voltage track lighting systems. Each 12v with 140w of light.(7 mr16 20w bulbs.) How many of these can I put on one 20A circuit breaker?

 

A 20-amp circuit provides 20x120=2400 watts of power. Each of your fixtures consumes 140 watts. 2400/140=17. So unless your inspector judges these lights to be continuous (and most inspectors would not), then you can have 17 of them on a circuit. I probably wouldn't cut it that close, however, especially since there is a small amount of power loss in the transformers. I'd probably limit myself to about 12.

Make sure you don't overload the transformers.

Note that the fact that the lights are low voltage does not enter into the calculation. A watt is a watt, independent of voltage.