Ok, I think things are starting to make sense now... I found the installation manual for the humidifier and it says:
"With factory settings, the Model 800 draws 11 .5 amps +/- 10% . Use a minimum 20 amp dedicated circuit when installing to operate at 11.5 amps. When set to 16 amps, use a minimum 25 amp dedicated circuit"
So it looks like it is meant to be a "dedicated circuit". But why then did the electrician add the junction boxes on the way to the humidifier? Is this part of the electrical code? I've heard that 120v outlets inside the house have to be every so many feet... is it the same for this 240v line (even though it's "dedicated" to something already)???