How to Build an Inexpensive Forced Air Wood Burning Heater, by Marc S.

Thursday, Jan 22, 2009

How to Build an Inexpensive Outdoor Forced Air Wood Burning Heater

If wood is available but you are unable to safely utilize it as a heat source due to the fact that your permanent or temporary shelter happens to be a recreational vehicle (RV), mobile home or travel trailer, then this idea may be helpful. On the other hand, it may also have appeal to those who live in a home where a wood burning heater could be safely used but for those who do not want the mess associated with constantly transporting wood and ash. Those with large homes and greater winter heating requirements should regard the heater as a possible method of reducing heating costs and not as a substitute for your current system. Two additional benefits of the forced air outdoor barrel stove heater are very low initial cost and portability. I built mine for less than $150 last year and can verify that it has been working splendidly since then.

For the first time in my life I have not been faced with expensive monthly propane or heating oil bills. Granted, my residence is tiny but the winters here are quite long and brutal. It is nice also to know that in the event that I move I can easily disassemble the heater and take it with me.

These images pretty much tell the story:

Back

Duct Detail

Front

I have excluded drawings of the blower and the flexible aluminum tubing that connects to the horizontal air pipe ends with large hose clamps. Keep in mind that each four foot section of flexible aluminum tubing will stretch to up to eight feet in length. Run the tubing into your residence either through a window opening that has been partially covered with plywood or through a small port cut through the side of your residence. A small blower connects to either one of the two tubing sections just inside the window opening or wall port. Except for the barrels and a small electric blower, all of the hardware required can probably be found or ordered at your local hardware store. Ace Hardware is a particularly good source for wood burning supplies, however, and most of their stores also carry the Vogelzang Barrel Stove Kit. In the event that you can't find a small used blower locally, try Dayton Blower. They offer a number of reasonably priced small blowers that would work just fine. If you are limited to twelve volt electric power you might consider finding a used automobile heating and/or air conditioning system blower. Should the nearest auto salvage supply company require you to go through the long drudgery of pulling the part yourself then give the U Need A Part (UNAP) locating service a try. I should warn you, however, that auto parts dealers can sometimes become irritated when one is unable to provide an exact part description. If you can connect to someone via e-mail try saying something like "virtually any heating-air conditioning system blower - the more powerful the better" and see what happens.

If there is someone in your area that owns a plasma cutter I would recommend hiring him to make the barrel cuts. It will save a lot of time, effort and metal cutting saw blades. Insulating the heater is an optional step but it can obviously improve efficiency. I wrapped the sides (but not the ends) of my heater with R-11 insulation. Make sure, however, that the paper backing is removed beforehand. Although fiberglass insulation is fireproof, the paper backing is not. If you should decide to use insulation it must be covered with sheet metal to protect it from wind and rain. I used some aluminum roofing material that had conveniently blown off the roof of a nearby derelict barn erected 1913. Fortunately, the owner had no interest in having the material returned since he was planning to have the barn demolished soon anyway. I snipped a few pieces of the roofing material to size and fastened them together with sheet metal screws. Note that I created a drip edge on top made cutouts for both the barrel legs and chimney pipe. The cover laces tightly together at the bottom with steel wire. I had briefly considered using ample quantities of heavy duty aluminum foil for the job but decided against the idea because it not only punctures and tears too easily but could also blow off in strong winds. I would not be surprised, however, if there is some sort of more easily cut metallic wrap available from Menards or Home Depot, for example, that would be far more convenient to use than sheet metal. At the present time I don't use a thermostat. If I did I would try to find one that could also turn the blower off should inside air temperature fall below a certain level due to fuel exhaustion which unfortunately turns the heater into an air chiller. If anyone can suggest how to do that, then please e-mail the details to the SurvivalBlog Editor.

The parts list is as follows:
Two clean 55 gallon steel drums
One small electric ("hamster wheel") blower
One Vogelzang Standard Airtite Barrel Stove Kit # BK100E. [Barrel stove kits are available from Lehman's. Search for Item # 17120106 ]
Three 4' sections of 4" diameter steel stove pipe. One section will need to be cut to length. Avoid using aluminum chimney pipe or elbows
Two 4" diameter steel stove pipe 90-degree elbows.
One or two 4' sections of 6" diameter steel stove pipe for the chimney. A rain cap is optional, but recommended
Two or more 4' sections of 4" diameter flexible aluminum [clothes dryer type] duct tubing. The number of sections needed will vary according to the distance that heater is located from your residence and how you decide to route the tubing after it enters your home. Keep in mind that when expanded each section can stretch to 8'.
Approximately six large [stainless steel Aero-Seal type] hose clamps for the air duct tubing
Two dozen short sheet metal screws
Duct tape and silicone sealant

Optional items would include a thermostatic fan cut-off switch and enough fiberglass insulation to wrap the sides and thin sheet metal to cover the insulation.

JWR Adds: I strongly recommend that the bottom of the main (firebox) barrel be lined with firebrick. Without it, the service life of a barrel stove could be as short as two years with regular use. A rain cap for the chimney is also a must, in my opinion. Without it, rainwater coming down the chimney will cause a barrel stove to rust out with alarming rapidity.

Take appropriate safety precautions in routing the chimney, to avoid fires,and to avoid the introduction of smoke indoors. Inspect the chimney and air ducts frequently, to make certain that carbon monoxide from the chimney does not co-mingle with the air passing through the ducts! The use of a carbon monoxide alarm is a must whenever using any sort of wood-fired heater.


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