An indirect water heater uses heat from a boiler’s heating loop rather than its own fuel source to warm domestic water stored in a tank. The boiler circulates hot water through a heat exchanger coil inside the storage tank, transferring thermal energy to the domestic water supply without direct combustion contact.
Technical Details
Indirect heaters typically store 40 to 80 gallons and maintain temperatures between 120 and 140 degrees Fahrenheit. Heat exchanger efficiency rates exceed 85 percent with minimal standby losses due to tank insulation rated R-20 or higher. These systems require a circulating pump to move boiler water through the coil at 2 to 5 gallons per minute. Operating pressures range from 30 to 80 PSI on the heating loop and 40 to 100 PSI on the domestic side.
Advantages and Applications
Indirect heaters integrate efficiently with existing boiler systems, eliminating the need for separate water heating equipment in homes with hydronic heating. They provide excellent recovery rates of 5,000 to 10,000 gallons per hour and long equipment lifespans of 20+ years. Installation costs range from $1,500 to $2,500. These systems prove most economical in cold climates where boilers run year-round for space heating.