An externally located wood boiler, built using cost effective DIY techniques can save an average home significant amounts of money on heating bills and fuel purchase prices. Renewable wood can be obtained relatively cheaply, burns cleanly and efficiently in the right system and can power a boiler and radiator system, as well as feeding heat into underfloor pipework. Add to this the reduced cost of building your own wood boiler, rather than purchasing an expensive, ready-made version, and you could be saving your family a lot of money.
- Skill level:
Things you need
- Tape measure
- Cheap wood
- Cement powder
- Large tub
- Spirit level
- 3/16-inch thick mild steel
- Safety goggles
- Protective gloves
- Metal bolts
- 1/8-inch thick mild steel
- 6-inch thick fibreglass
- 12-inch thick fibreglass
- 80,000 BTU heat exchanger
- Steam vent
- Copper piping
- Temperature gauge
- Green metal sheeting
- Dry, seasoned wood
Choose a suitable location for your boiler. Select dry, levelled soil. Pour a layer of gravel over wetter soil, if you are limited in your location. Measure a square 50-inches by 50-inches to accommodate the boiler using a tape measure. Build a shallow wooden frame from cheap wood into which you can pour concrete. Ensure it is at least 4-inches deep, according to Northland Distributing and Manufacturing, a leading manufacturer and distributor of Crown Royal stoves, boilers and heating systems particularly for cold climates.
Mix cement powder, sand and gravel in a 6 to 1 to 1 ratio with water in a large tub. Stop mixing once the cement powder disappears and the resulting mixture reaches a firm but malleable consistency. Pour the concrete out into the wooden frame. Use a spade to flatten the concrete. Check it is flat using a spirit level. Allow to dry for 24 hours.
Build a mild steel plate firebox approximately 35-inches tall, 20-inches wide and 40-inches deep to heat an average home, according to The Garden Grapevine, a resource written by qualified welders and expert boiler builders. Position it in the centre of the concrete base. Wear safety goggles and protective gloves. Weld three sides, the base and the top together using a welder, metal bolts and brackets. Leave one side so it can be removed easily (when cool) to load wood inside.
Construct heat resistant base skids out of 2 pieces of 6-inch I-beam, a type of steel girder used to support heavy structures. Weld it into place along the bottom of the firebox using the welder. Check that the base of the firebox is now 6-inches above the base of the boiler, which it should be if the I-beam girders are lifting it by 6-inches.
Create a boiler casing from 1/8-inch thick mild steel that stands approximately 55-inches tall, 25-inches wide and 45-inches deep, giving an approximate overall capacity of 150-gallons. Fit the boiler casing around the firebox so it rests on the concrete base structure. Insulate the inner walls of the boiler using 6-inch thick fibreglass and the top using 12-inch fibreglass. Fill with water.
Purchase and install a 80,000 BTU (British Thermal Units, a measure of heat output) heat exchanger. Add a baffle to improve efficiency of circulation and an externally located steam vent to allow excess gas to escape from the internally-located heat exchanger. Connect the components using copper piping. Fit a temperature gauge to the outside to adjust the heating requirements and regulate the system.
Build a green coloured metal frame from metal sheeting around the whole boiler to enclose it and improve its attractiveness. Load the boiler with dry, seasoned wood from a renewable source. Your own supply of trees is ideal because you can replant and harvest as you need more fuel, and maintain an environmentally sustainable system.
Tips and warnings
- If you build sustainably and with consideration for your environment, you may be eligible for a grant, or similar financial assistance, depending on where you live. Contact your local authority to find out if extra funding is available.
- For purely DIY projects it is recommended that you do not attempt to pressurise any part of your system as this can cause an explosion. Keep children away from large fires and furnaces as they can suffer serious burns. Welding equipment is dangerous if used improperly and can result in serious eye injuries or skin burns. Wear goggles and gloves during use.
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