Outdoor Wood Burner
. . . Progress

I will Show and Tell you how I'm progressing . . .

Under the guise of R&D, this Do-It-Yourself design has
undergone many turns and U-turns since its inception.

Feb. 19, 2003

I soldered the first 80' length of  3/4" copper that will take hot water from the Wood Furnace outside my Shop, to my Greenhouse Radiator (which is the large copper heater core from a Bus).


Feb. 19, 2003

The Fan(s) that blow air through the Heater Core are dual window fans which mount in a bedroom window. I have the option of using one or both fans, which will turn on and off automatically with the Circulator which is controlled by a Thermostat that senses air temperature in the Greenhouse.

The fans are mounted in a Northern stud cavity under the Workbench. There is an air space behind them to allow free air flow. A wall switch will determine if one or both fans run automatically with the Circulator.

The water line shown in the center is the domestic supply to the Misters and Emitters. Visible on the right is the Electric Backup Heater that will turn on if the Hot Water Heat fails. It is operated by its own thermostat which is set somewhat lower than the Hot Water Thermostat.


Feb. 20, 2003

This is the back side of the Heater Core showing the inlet and outlet. Rubber Heater Hoses will be used to connect the Core into the system to provide a degree of flexibility and easy disconnection for repairs.

In the event that this Heater Core fails to provide adequate heat, it would be a simple matter to replace it with the larger Radiator of a junked car, bus, or truck. In that case it would be necessary to bush the inlet and outlet down to match the 3/4" copper lines used in the system. Optionally, additional Heater Cores could be used in series or parrallel.

Unseen is an air bleeder screw on the top of the Core. In the absence of such a bleeder, it would be necessary to fabricate one. Air which accumulates above the water decreases the efficiency of the radiation. Small automatic air vents are available for home heating systems.

Here the Heater Core is mounted in front of the fans. The circulator will be connected to the Core. Then it will go underground to the insulated 4" plastic pipe which is the umbilical cord between Furnace and Radiators.

Feb. 21, 2003

Here the 3-speed Circulator is connected to the Heater Core on the left by a radiator hose. The Circulator will pump cooled anti-freeze back to the Furnace through the 3/4" copper return line. Note that the hot supply line is tilted up slightly to prevent an air pocket.

You may notice that I moved the Core to the left to allow more elbow room to fabricate the components. This may also provide better air circulation, since the Core is more centralized and may allow more of a figure "8" airflow, rather than the previous circular pattern.

Feb. 22, 2003

NOTE: I used Thermo King Sleeves as shown and ended up with a sticky Mess. Luckily it was still above ground.  I received a sleeve refund.
Today I made the 20+ wooden inserts that support  the 3/4" copper lines every five feet inside the 4" plastic underground pipe. The copper lines will be insulated by closed-cell polystyrene Foam Sleeves like the one shown on the left. A dab of expanding foam insulation will keep everything in position.

The wooden discs were cut from 1/2" plywood using a 4" hole saw in a drill press. Then a line was drawn through the center of the disc so the pipes could be positioned opposite each other. A jig was used to ensure that the 1" pipe holes were uniform. Underground Pipe Insulation NOTE

Feb. 24, 2003
Today I soldered the return line between the Furnace and the Greenhouse, and made the connections through the wall into the radiator. This would be going much faster, but it's been cold enough to keep snow on the ground since christmas.

Now it's time to hook up the lines to the furnace. Since I expect to have the greenhouse heated by March 01, the external radiators/collectors may have to be postponed. I also need to get an insulated enclosure built.


Mar 01, 2003
There's not much to tell, but today I pressure tested my lines from the furnace, to and including the Bus Heater Core radiation in my greenhouse. I tested it for 30 pounds, which it held (after I tightened the circulator flanges and a plug). I plan to test it at 50 after the whole system is connected.
Wish me luck!


Mar 02, 2003
Comment on this brain storm:

A 40 gallon or bigger? hot water tank inside a plastic 55-gallon drum also filled with water, which together should act as a heat exchanger for my outdoor Hot Tub building. The uninsulated assembly should give off enough heat to warm the 8' X 8' building.

Mar 04, 2003

The pipes are run and insulated. When the ground thaws, they get buried below the frost line. The greenhouse is in the distance (80'). The gauge pointing straight up indicates 30 pounds and holding. This gauge also shows water temperature.

The rubber hose at the bottom of the stack is a test gizmo that has an air gauge and an air valve to pressurize the sytem to see if it leaks. It will be replaced by a fitting that allows a funnel to fill the system with anti-freeze.

This whole plumbing assembly will be moved to the front of the furnace when the pipes are buried underground. But now it's time to plant greenhouse seeds here in central Pennsylvania.

The stainless stack was made from a commercial refrigerator door like the one behind it. Q: What;s the best way to drill this tough stainless? It laughs at a new carbide drill bit. E-mail me

I "formed" it with a length of I-beam and a rubber hammer:

I'm wondering if a smaller (Red area) pipe suspended inside the stack would heat the air and improve overall chimney draft, with the outgoing air being heated by three surfaces instead of one.

Nov 22, 2003
It finally quit raining so I could clean out the trench which had rain water or mud in it most of the summer, and bury the copper heating pipes. I'm still mowing grass in Pennsylvania; VERY unusual weather here!

                                  Click these individual photos for a larger view . . . with detailed captions.
Stay tuned . . . more coming !

Send your comments

Comments page