goose62075,
What you kind-a have to realize is, those block heaters draw a fair amount of amps. On our coach, an '04 Itasca Horizon 36GD with the C-7 330HP CAT, the info center in the center of the coach, shows between 7 and 10 amps when that block heater is on. So, if you've got an array of other things on and being used that may bring you to the tip-top of amperage draw for that particular breaker, then adding the block heater may put you over the top and trip it.
So, unless you're in some fairly substantial "cold" country, I'd maybe look for a switch or, at the very least, un plug it from its 110V source. Just some thoughts here. Good luck.
Scott