Truma Combi furnace/water heater

[HoosierB]

Mine has the same rear ducting as Astrodokk's. It's not flexible hose ducting but a metal oval, manifold-like duct behind the wall and stove/fridge/gen. It makes a turn around the gen, under the closet floor/shelf and exits with a round vent like the others below the closet door. I'm surprised it works rather well for heating that area.

[Astrodokk]

I didn't know how it was routed so thanks HoosierB for that information.
All I do know is that when it's on, it does indeed warm that rear area nicely and even warms the bath due to the open grill in the bath door that allows the warm air to get in there when the fan lid is closed all the way.