A sidearm water heater is a compact, tankless heat exchanger that connects to a boiler’s supply line, heating domestic water as it flows through without requiring a separate storage tank. This configuration allows boiler-heated water to warm incoming cold water in a coil arrangement, providing hot water instantaneously for small-demand applications.
Technical Specifications
Sidearm units measure 12 to 24 inches in length and weigh 15 to 40 pounds, fitting into tight mechanical spaces. Heat exchanger surfaces typically measure 1 to 3 square feet with flow rates of 2 to 6 gallons per minute. Operating temperatures range from 120 to 160 degrees Fahrenheit. These systems operate at boiler pressure, typically 15 to 30 PSI on the heating side and 40 to 80 PSI on the domestic supply side.
Applications and Limitations
Sidearm heaters work best in smaller homes or buildings with low simultaneous hot water demands, such as cottages and guest houses. They eliminate the need for separate heating equipment in boiler-equipped properties and reduce installation complexity. Costs range from $400 to $900 including installation. However, they cannot support high-demand usage like simultaneous showers and dishwashers without temperature drops or installation alongside storage tanks.