Gee Dave, I must have been sleep since Nov. 9th because I never saw your post.
Sorry about that...
On our coach there are ducts from the rear gas furnace, we have two furnaces, that go to the basement where the tanks are to keep them from freezing.
I guess you have the basement heat pump, is this correct?
Do you also have a gas furnace? I would think that the gas furnace would have a duct going to the tank compartment, but I wouldn't think the heat pump would since the air conditioning would also be going to the compartment when it is used, but that is my opinion.
You might want to sent an email to Scott Pullin at GSC and ask the question to him, I am sure that he can tell you or at least have someone tell you how they are heated. He has been a great help to me in the past.
Provide your model and serial number so they can look the information up.