PowerStor Series® Indirect Fired units provide class leading performance and large amounts of hot water. These units incorporate a newly designed, super-efficient heat exchanger coil. Made of 1 1⁄2" O.D. diameter carbon steel tubing and coated with Vitraglas®, they have a total heat surface area of 27.2 feet resulting in exceptional first hour delivery and vast hot water reserves. PowerStor Series® models are the perfect addition to a boiler system.