Maybe instead of "gravity feed" you mean "convection," a wall furnace without an included blower fan to force the air through it? I had saved one out of a scrapped office trailer for a while, thinking I would have a use for it some day. But I scrapped it when "some day" never arrived.
I have lived in a 3-room apartment with a natural gas wall furnace and blower on a central wall, and it kept it warm enough in Northeast winters.
Or maybe you mean "fuel oil" aka diesel? There are oil heaters that work on a drip of #2 fuel.
Originally Posted by jazty
Can you find an example of one online? "Gravity fed"+"propane" doesn't really make sense.. Propane is pressurized...
Most propane appliances run on vapor boiled off taken from the top of the tank, but a few run on the liquid fuel drawn from the bottom of the tank. Maybe someone thinks drawing liquid from the bottom forced down by the vapor equals gravity feed?