P ptonsparky Senior Member Location NE (9.06 miles @5.9 Degrees from Winged Horses) Occupation Electrical Contractor Dec 15, 2010 #21 220/221 said: The same reason men have nipples. It makes more sense to have one basic design and tweak it with a few simple changes to create different models. Click to expand... I like 220s anwer best. If we have to put a ground screw on a switch why not a 2 wire recept?