The Valiant FT is a condensing, forced draft appliance utilizing a premix power burner based on a push through design which offers several venting options. Heat output is controlled by the venturi and zero governor gas valve, which work together to provide seamless modulation. It is designed for use with a fully pumped and pressurized water system. The turndown ratio for this appliance is up to 10:1 for natural gas models VA0110, VA0155, VA0199, VA0250, VA0299 and VA0399 and 7:1 for VA0080. The turndown for propane units is 5:1 for all models. This results in the appliance automatically modulating to provide heat outputs from 100% down to approximately 10% of rated input for models VA0110 to VA0399, and an appliance output from 100% down to approximately 14% of rated input for model VA0080.