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Old 07-14-2016, 02:32 PM
Machine Elf Machine Elf is offline
Join Date: Feb 2007
Location: Challenger Deep
Posts: 10,561
Originally Posted by carnivorousplant View Post
Perhaps he was thinking of fluorescent lights, which use a lot more current to start than to run. They use about twenty minutes cost of electricity to start.
A common claim, and I'm calling bullshit on it. If you can point to a cite, I'll have trouble trusting that source in the future.

twenty minutes is 1200 seconds. A slow-starting fluorescent lamp might take 3 seconds to start up. An 80-watt fluorescent lamp troffer draws about 0.66 amps during normal operation. Your claim means that during that three-second startup, an 80-watt fluorescent lamp troffer draws .66*1200/3 = 264 amps. I'm pretty sure that would blow a typical 15-amp breaker. Heck, you could replace the 15-amp breaker with a block of solid copper, and then you would blow the main breaker on a typical house (usually rated for about 150 amps). If it didn't, it's unclear whether the 14-gauge wire feeding the lamp would survive three seconds of delivering 264 amps. According to the rated resistance of 14-gauge wire, you'd be dissipating 176 watts of heat into each foot of the line feeding the troffer (and another 176 watts per foot into the neutral). Things would get pretty hot.

Rapid-start fluorescent systems have an even shorter startup period, implying higher currents. Cut the start period down to 1 second, and this implies 3X the current, and 9X the ohmic heating in the house wiring. Is it getting warm in here? Do you smell smoke?