The amperage on the 18 ga. fixture wire is limited by the wattage of the lamp. The switch wire on the other hand willl be loaded with the amperage of all the fixtures connected to it. Therefore, if you have twenty (120v) fixtures with a 100w lamp in each your circuit will be loaded to 16.7 amps and that will be the load on the 14/2 switch leg.
[This message has been edited by SteveMc (edited 04-04-2004).]
