If yo have a hand held remote than it definately uses a battery. Some wall mounted switches i have seen also use battery and some are milivolt run. In 30 years of hooking up these things in different houses, i swear it seems like no 2 are alike,. It really drives one nuts.
In addition the hand held could also have a thermostat, which could cause other problems like the heat setting too low.
cheers...Coffeeman