Article 1-3 Electrical Safety in Grow rooms

One of the commonly asked questions regarding electrical and gardening with High Intensity Discharge (HiD) lighting is "how many 1000 watt lights can run on this set?" Generally an outlet on your bedroom or basement wall is part of a 15 amp circuit. There are up to 12 lights and or plugs on that circuit. A 1000w HPS or Metal Halide light takes 9 amps at 120 volts so you can only run one on a wall outlet circuit. A standard dryer outlet is 220 volts and 30 amps so you can power up to six 1000 watt lights on that circuit. A range outlet is typically 40 amps on an older house and 50 amps on a new house. Therefore you could run up to eight lights and 10 lights respectively. The important thing to check first is the breaker size for the circuit you want to use. The breaker is sized to protect the wire and then anything plugged into the circuit. Below is a table used to size wire for whatever load you have.

You must note that for safety, the Canadian Electrical Code states that you can only load circuits up to 80% of their recommended capability.

Another common question is "Should I run my lights on 110 volts or 220 volts?" The answer is that it makes no difference - a 1000 watt ballast uses nine amps at 110 volts or 4.5 amps at 220 volts go on a typical dryer outlet. You can run six lights at 4.5 amps, 220 volts for a total of 27 amps, 220 volts or six lights at 9 amps 110 volts (three lights each side of the 220 volt circuit) for 27 amps at 110 volts and 27 amps on the other 110 volts.

Note:
A 220 volt circuit is a three wire circuit with two hotwires and a shared neutral (white) wire so that there would be 27 amps on each hot wire for a total of 27 amps at 220 volts. If you are still in doubt about what you can do, there are lots of good books on the subject at your local library or ask your local gardening store specialist.