... ignition pin,automatic electrical pulse ignition device. 3.Over water 1.Duct exhaust type, 2.Double ignition pin,automatic ... electrical pulse ignition device.3.Over water pressure protection device,4.Water-gas interlock valve device,5.Anti-dry ... optional,11.Zero pressure water start for 5L&6L is optional,12.White coated,metallic white/silver/golden color is optional. water heater