A. O. Smith’s ProLine XE Combination Boiler has a service-friendly, compact design and is engineered with residential building professionals in mind. By moving components, such as the built-in circulator, to an easily accessible location within the unit, service and maintenance are simplified. The backlit LCD display has a user-friendly interface that provides text-based diagnostic information. Available in 110,000, 150,000 and 199,000 Btu/h models, the boilers can deliver up to 4.8 gallons of hot water per minute, the highest capacity in the combination boiler category. The unit features an air-handler interlock that immediately stops nonheated air from circulating when it alternates from space heating to domestic hot-water mode. 800-527-1953; www.hotwater.com.