Hi, I am about to fit an extractor fan, but notice on the box it states 12v. Am I still ok to simply connect it straight to the mains supply, or do I have to have a transformer of some kind. I intend to come from the mains supply (a spur already exists) to a double pole lightswitch, then to a FCU and finally the fan. Like I said, on the box it state 4 inch 12v extractor fan, but there is nothing in the manual about a transformer. Thanks!