Can You Use a Wood-Fired Water Heater for Hydronic Heating?

Design Considerations

A wood-fired water heater can be used for hydronic heating by circulating hot water through a thermosiphon system, which uses the buoyancy of warm water to create a circulation of water. To achieve this, the water heater’s tank must be elevated above the distribution system, and the system must be carefully designed to ensure the water returns to the tank without the need for pumps. For example, a 300-gallon tank might be placed 6 feet above the distribution system to create a 1-foot head, which is sufficient to drive the thermosiphon.

Installation and Maintenance

When using a wood-fired water heater for hydronic heating, it’s essential to size the system correctly to ensure efficient operation. A rule of thumb is to size the system for 1-2 square feet of radiator surface area per gallon of water. Additionally, the stove coils must be designed to handle the high temperatures and pressures involved, and regular maintenance is crucial to prevent corrosion and ensure optimal performance. For example, a typical batch heater might require daily cleaning and inspection to maintain its efficiency.

DIY and Pre-Fabricated Options

For those who want to build their own wood-fired water heater for hydronic heating, there are several DIY options available, such as using a converted oil-fired water heater or building a custom tank from scratch. Pre-fabricated options, on the other hand, can be more cost-effective and efficient, but may require additional customization to meet specific needs. When choosing a pre-fabricated option, look for systems that are specifically designed for thermosiphon operation and can handle the high temperatures and pressures involved.