New owner of a 27HFS here and first post too.
I have the same question. Except my unknown switch is by the stove against the wall for the refrigerator. When we did the walk through with the dealer, he didn't know what the switch was for either.
I don't believe I have heated tanks though. How do you tell if you do? I have several wires going to each of my tanks. I was figuring those are for grounding though because of static electric build up on the plastic.
Any help would be greatly appreciated.