Heated underbelly on a 32BHDS

I'm curious how the ub is heated? Here in NW Fla we have had record cold temps and I don't know if I had the heater on correctly. The tank monitor panel has a switch for a heater and I assumed it was for the entire ub. Is this correct? Or is it just for the tanks? I could not find info in my owners packet but I did not look thoroughly in the trailer for more paperwork. This is our first TT and our first time having to deal with how temps this cold would affect it. It is stored at home in the driveway. I drained all the water lines but did not do anything further. There is a small amount of water in all three tanks. Two with holding tank additives but no antifreeze I'm aware of. Fresh water tank is just water. The WH is turned off. When I turned the heater switch on the tank panel on the WH came on using propane. I switched that off too as I did not have any water in the WH (I think). Is the ub heated with water from the WH? Or is it heated electrically using heating tape or similar. Or was the WH coming on to use hot water for the tanks and the ub is heated automatically using other methods? If I drained the water from all drain points under the unit and did nothing else, am I likely ok? Or should I do something before I take things back to normal status? Temps in our area were as low as 19-20F for several hours over a period of 4-5 days. Oh yeah, the ub is completely sealed and filled with foam. Thanks for any and all help, and I hope everyone is having a great New Year and getting ready for camping! Rick.

Pensadawg, there is not any switches that I know of that direct heat into the UB. The switch you are refering to is for the water heater only. Now if you ordered the your TT with heated tanks then there has to be a switch somewhere. A standard HL coach without heated tanks has a 2" duct that is hooked to the heater plenum and blows hot air into the UB. Thats all. Never run your WH without water in it, whether it be on propane or electric(110). If you remove the outside heater cover and remove the anode plug, that will drain the WH tank. Best I can tell you at this point. Bob

Thanks for replying Bob. The switch is only labeled HEATER. I've used the WH all summer with the switch off so I don't think it is for the WH to operate just for hot water in the plumbing. I failed to mention in first post that the electric and gas rockers were turned off at the exterior WH panel but the propane element came on anyway. Thats why I wondered if the switch at the tank panel operated the WH for tank water heating or ? Also, there is a lighted switch in the bathroom that turns the WH off and on and the afore mentioned switches in the exterior WH panel. I hope this has less confusticated things . I am going to call the factory tomorrow to see if they can help. Thanks again, Rick.

lighted switch in bathroom is

110 for HW
the rocker switch on panel is for propane for HW

Yes to what Irvin said. The only way you are going to get hot water is the switch on the tank monitor panel or the "red" switch. Other than tank heaters...you will only get heat in the UB when the heater is on. Bob