Description

Core Components

Firebox / Combustion Chamber: The heavy-duty steel or cast-iron chamber where firewood is loaded and burned.

Water Jacket: An insulated reservoir surrounding the combustion chamber or firetubes, where thermal energy transfers directly to the surrounding water.

Flue / Chimney Pipe: Runs through or above the unit to safely exhaust smoke while aiding heat exchange with the water jacket.

Aquastat & Draft Control: Regulates air intake dampers based on water temperature to maintain a consistent heating rate and control the combustion rate.

Ash Pan & Grate: Collects spent ash below the firebox for straightforward disposal.

How It Works

Combustion: Firewood is loaded into the firebox and ignited. Air dampers supply oxygen to maintain the burn.

Heat Transfer: Radiant heat and hot flue gases pass against the inner walls of the water jacket, rapidly raising the temperature of the water.

Circulation: Heated water flows through home plumbing or a closed-loop hydronic heating circuit, either via thermal siphoning (gravity) or a powered circulator pump.

Thermostatic Regulation: As the water reaches the set temperature, an automated mechanical or electrical damper reduces airflow to slow down the fire.

Common Applications & Types

Indoor Direct Water Heaters: Compact vertical metal cylinders (often installed in utility rooms or outdoors) used primarily for domestic bath and kitchen water.

Outdoor Wood Boilers (OWBs): Weatherproof units housed in a separate shed or outdoors. They pipe hot water underground into the main building, keeping smoke, dirt, and fire hazards away from living areas.

Wood Gasification Boilers: Advanced high-efficiency units that burn both the wood and the gases released from heating it (secondary combustion), producing minimal ash and smoke with efficiency levels above 80%.