Can you use a masonry heater to heat domestic hot water?

Masonry Heater Design Considerations

Masonry heaters are designed to operate at low temperatures, typically between 150°F to 200°F (65°C to 90°C), which is not ideal for heating domestic hot water. However, by incorporating a heat exchanger or a secondary heat transfer system, it’s possible to increase the water temperature. A common approach is to integrate a heat exchanger coil within the masonry heater’s flue or chimney, which can preheat the water before it enters the water heater.

Integrating Masonry Heaters with Heat Exchangers

When designing a system that uses a masonry heater to heat domestic hot water, it’s essential to consider the heat exchanger’s efficiency and the system’s overall performance. A well-designed heat exchanger can increase the water temperature by 20°F to 30°F (10°C to 15°C) for every 100°F (55°C) increase in the masonry heater’s temperature. This means that a 200°F (90°C) masonry heater can preheat the water to 100°F (38°C) to 120°F (49°C), which is still lower than the desired temperature for domestic hot water. Therefore, a secondary heat source, such as a conventional water heater or an electric water heater, may be necessary to bring the water to the desired temperature.

System Design and Optimization

To optimize the system’s performance, it’s crucial to carefully balance the masonry heater’s output with the heat exchanger’s efficiency and the secondary heat source’s capacity. This may involve adjusting the masonry heater’s size, the heat exchanger’s design, or the secondary heat source’s output to achieve the desired water temperature. By carefully designing and integrating the masonry heater with a heat exchanger and a secondary heat source, it’s possible to create an efficient and effective system for heating domestic hot water.