MasterTemp ASME commercial rated heaters offer all the efficiency, convenience and reliability features you want in a pool heater, plus a lot more. As easy to use as your home heating system, plus, user-friendly indicator lights make system operation and monitoring a snap. The compact design and super quiet operation won't intrude on your poolside leisure time. Optional heavy-duty (HD) units with cupro-nickel heat exchanger stands up to the harshest of applications, like low pH, salt pools, high flow or heavy use.