Hayward W3H200FDN 200K BTU Low NOx Universal H-Series Natural Gas Heater. Natural Gas Pool and Spa Heater is environmentally friendly and energy efficient. Boasting an industry leading 84 percent thermal efficiency the environmentally friendly H-Series complies with all current California and Texas air quality emission standards. It is also the only pool heater to offer Cupro Nickel heat exchangers standard on all models. Cupro-Nickel is designed to withstand the harshest pool environments like low pH, high flow and heavy pool use and is also recommended for all pools using salt systems. Features: Natural Gas pool heater 200,000 BTU For In-Ground Pools and Spas Electronic Ignition Dual Thermostat Stainless steel burners Highly resilient Cupro Nickel heat exchanger Designed for the toughest environments Stands upto salt, low pH, high flow, heavy use Easy-to-read L.E.D. digital Control Panel Polymer header for superior hydraulic performance Insulated fire tile combustion chamber Larger diameter plumbing systems 2" x 2.5" CPVC unions 84 Percent thermal efficiency Meets the NOx Emission standards Meets California and Texas air quality emission standards