Stovetop Heater

One of my ongoing projects is building our own travel trailer from scratch. We call it the Gypsy Wagon because it is shaped kind of like a traditional one. It is 16 feet long and 6 feet wide on the inside which is not a lot of room. I wanted to have heat in it but there really isn’t room for a space heater or a wood stove. The typical option for RV’s is a furnace. This could be installed underneath the bed platform and the heat could be delivered to the cabin by a duct and a fan. If you read my previous post about why I don’t like forced air furnaces you will understand why I decided not to do this on the gypsy wagon.

Instead I made an air-to-air heat exchanger unit that sits on top of one of the burners on the cooking stove. They say to not use your stove as a heater and I agree somewhat. It is an open flame and puts its exhaust gases right into your living space. This is not much of a problem if you have a large well-ventilated space but this is a small tight space so it needs a vent. If you have a vent you need some way to keep all the heat from going up the chimney. The solution is a heat exchanger.

 

A heat exchanger takes the heat of the exhaust gases and transfers some of it to fresh air that is circulated. Metal conducts heat well so I made the heat exchanger out of steel. The heat exchange elements are 1” diameter steel tubes.  They are welded into a section of 6" diameter steel tubing that sits on top of one of the burners on a gas or propane stove. To transfer heat efficiently you need to expose as much surface area as you can to the hot gases so there are seven tubes in my little device. The more tubes the better. Just be sure to provide space around each one so the exhaust gases can get all the way to the chimney vent.

You should either make short legs for the bottom or cut scallops out of the 6" tubing so that combustion air can easily get the the flame on the stove burner.

looking down vent at heat exchange tubes

I bought a small humidifier unit at a thrift store and took off the fan part of it to circulate fresh air through the heat exchange tubes. This fan only uses maybe 15 or 20 watts so that’s not much of a power load. You could use a computer cooling fan, too. They don’t use much power. I mounted the fan so it would blow air through the heat exchange tubes which are heated by the gas flame from the stove.

For the vent, I bought some stock components that allow me to connect a flexible 3” diameter aluminum duct to the top of the unit. Dryer vent will work as will any non-combustible flexible duct. I can stick it out of a window or make a separate, closeable, vent hole in the roof of the trailer. The vent tube needs to have at least 2 feet of vertical rise to vent properly. The gases from the stove burner will not get out if the vent goes down. The will simply escape from under the heat exchanger unit and into your living space,

It works quite well. It doesn’t take much heat to warm up the small space in the gypsy wagon. It is only 96 sq feet of floor space. When you don’t need heat you can take the unit off of the stove and store it away. Just remember that this thing will get hot and you will want to wait for it to cool down before moving it.