Fire has been an important part of human life for thousands of years. Controlling fire – and its energy output – has always been a goal of humans since we rubbed two sticks together. Wood furnaces – a box able to control the fire, smoke and heat – were designed for efficiency and over time they have continued to improve.
Wood furnaces or wood boilers – the terms are often interchangeable – is a technology that has been around for more than 180 years. These first wood furnaces were the workhorse standard for turning wood into energy. Unfortunately, standard-efficiency furnaces burn just the wood to heat the water, resulting in lots of wood being burned and lots of smoke going into the air.
The Era of the High-Efficiency Wood Boilers
Enter the next generation of outdoor wood boilers. Self-contained, weather-tight and insulated, outdoor wood furnaces offer the potential to dramatically reduce heating costs – and wood consumption – while supplying hot water to your home, garage, pole building, spa, pool, etc.
The newest wood furnaces will burn a variety of wood types in the coldest weather while heating your home for a fraction of the cost of other fuel sources.
How it Works
These high efficient wood furnaces rely on a process called ‘gasification’. In typical wood boilers or stoves gases (think smoke) rich in unburned fuel are lost up the chimney.
But what if you could burn that smoke? If you could you would add 30% to 50% more heat from the same amount of wood.
Fire is simply a chemical reaction. For gasification to happen in an outdoor wood boiler the process requires a balancing of these three elements:
The primary combustion of the wood is done by adding heat but depleting oxygen causing smoke. The fuel – in this case, wood smoke – is drawn into a second combustion chamber where oxygen is added. This burns the smoke and gases at high temperatures creating a clean, complete burn that heats the water jacket.
There are three designs common in wood gasification: updraft, downdraft, and crossdraft. Heatmasterss G Series works on a downdraft model that has many advantages.
Using a Downdraft Gasification Furnace
- Combustion in a downdraft wood furnace is a four-step process:
- Wood is “baked” in the upper firebox to create smoke.
- The smoke and gases are then pushed downward into the refractory.
- The gases are mixed with the right amount of air between the upper and lower chambers.
- A clean and efficient burn is achieved in the lower chamber.
- Heat is then transferred to the water in the water jacket through a heat exchanger.
With downdraft gasification the air and fuel flow in the same direction which tends to lower the tar content keeping the build-up of creosote to a minimum.
Combustion with the right amount of oxygen, means less ash, soot, and creosote to clean and higher BTUs (British Thermal Units). It all comes down to the right amount of oxygen in the process.
Getting the Best Furnace BTUs
Wood contains energy in the form of BTUs. One of the biggest reasons your wood might not burn efficiently is that it hasn’t been seasoned properly.
Wood contains water and if moisture content is too high then you are using your energy to burn moisture out of your wood and not using it to heat your home. If your furnace is producing excessive smoke you may be burning wet wood which equals lost heat.
The other reason you may not be getting the highest efficiency out of your wood furnace is the improper application of oxygen. If it isn’t at the right time and the right place the smoke and gases will either:
- Not combust completely and your energy will be wasted up the chimney
- Combust at a rate that is too high for the furnace’s ability to transfer heat to the water.
Either way BTUs will be wasted. An infrared thermometer can easily tell you if heat is being lost out the chimney. Temperatures above 300 degrees typically indicate wasted energy.
Wood Boiler Damper Control
Knowing how crucial controlling oxygen is to creating a highly efficient outdoor wood boiler we designed a modulating damper system. This system continually adjusts the air intake to make sure the air-to-fuel mixture is optimum.
A furnace is typically sized to meet the maximum heat load (BTU’s) during the coldest part of the heating season. The Heatmasterss G Series can adjust its BTU output by fine-tuning oxygen levels. This allows BTUs to be reduced during periods of low demand while maintaining efficiency and reducing emissions.
We are committed to the details. We know there are many variables that affect how a wood furnace will perform in real world conditions. Our team is always working to produce worry free products that are easy to use year-round in almost all situations.
Our dealers are Heatmasterss wood furnace owners who are ready to answer your questions from real life experience.
Contact one of our Heatmasterss dealers near you today to learn more about the very best outdoor furnaces for your home or business.Back to all posts