... exhaust type, 2.Double ignition pin,automatic electrical pulse ignition device. 3.Over water 1.Duct exhaust type, 2.Double ... pin,automatic electrical pulse ignition device.3.Over water pressure protection device,4.Water-gas interlock valve device,5.Anti-dry combustion ... for gassaving,7.Anti-freezing device8.Free hand shower,9.ODS device is optional,10.20minuntestimer is optional,11.Zero pressure ...