T@Bs are small trailers, so full-sized home appliances, or even full-sized RV appliances are usually too big and waste too much precious storage space in the T@B. The LP furnace that is an optional accessory for the T@B is one such "space-waster". In the clamshell or L models, the furnace takes up minimal space because it's a straight shot from the external air supply/vent to the front of the unit. But on the queen bed model T@Bs, the front of the furnace is actually beneath one of the rear seats, so the factory must install extra vent tubes to route the air and exhaust out properly. These tubes take up most of one side of the under-seat rear storage, and even 1/3rd of the other rear seat storage as well. That's a ton of storage space to give up!
My first T@B didn't come with an LP furnace, so I was forced to improvise. What I discovered was that I actually liked the alternatives better than the real thing! And, I certainly liked having all that rear seat storage fully available.
When I am at a campground with electric hook-ups, I use a $30 oscillating ceramic heater that I purchased from Home Depot. It's small, lightweight, quiet, and heats the T@B very quickly. It also has a built-in thermostat and adjustable fan speeds. A great deal!
When I'm away from electric and dry camping ("boondocking"), I use an Olympian Wave 3 catalytic heater. It runs off of LP gas, is TOTALLY silent, and unlike the LP furnace, does not require any battery power to run. It's also very small and lightweight and uses less LP gas than the furnace.
In my first T@B, I installed a brass T-connector on the gas line outside coming from the LP tank and then ran an LP hose up through the front window to connect to the Olympian heater (which sat on the front kitchen countertop). While this required no major modifications to the T@B, it required that the heater be placed at a higher level than was best (heat rises). So, in the new T@B, I had my dealer install the T connector underneath the stove on the inside of the T@B. I also got a quick connect fitting so that I would not need to use wrenches to attach and disconnect the hose to the heater each time.
When not in use, the hose and quick connect wraps nicely into the under-stove cabinet.
When I want to hook up the Olympian, I just unwrap the hose and connect it. I can place the heater on the floor if I keep the couch in "couch mode", or else place it on a table or on top of the stove itself if I extend the bed out fully.