Ok.. Its become pretty apparent that I need to upgrade the wiring in the basement to handle the number of games. Can anyone offer advice for making sure I only have to do this once? How many amps does an avg game draw?
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12/2 20A lines are definitely the way to go.
Without getting into anything technical you can almost always put 5 or 6 games on a 15A circuit or 7 or 8 games on a 20A circuit. Pinballs draw a bit more so say 3 or 4 on a 15A circuit and 4 or 5 on a 20A circuit.
Do yourself a favor, only run 20A circuits(using 12 gauge Romex). For the slight cost increase, it gives you a better piece of mind.
And if you want to get anal and measure everything, grab a Kill-A-Watt meter. Search around the 'net since these things are almost always on sale somewhere.
Good luck,
Jeff
p.s. I'm sure there will be loads of technical answers I just tried to give you a common sense, plain English one...