The FXHOOOD is required by Bosch whenever a customer installs the Bosch AquaStar 125FX Tankless Water Heater. It is also required for the older 240FX model.
The FX Hood is a horizontal vent terminator with built-in freeze protection for the Bosch AquaStar 125FX and 240FX models as well as the Takagi T-K1 Tankless Water Heater. The FX Hood will prevent cold air from freezing the heat exchanger on the Bosch AquaStar Tankless Water Heaters. The back draft preventer (FX Hood) should be used with all electronic ignition gas tankless water heaters where the outside temperature can fall below 32 degrees Fahrenheit.
The Bosch FXHOOD is doubled-piped so it can be installed next to combustible materials. The face plate is 12 inches by 12 inches and the pipe is 8 inches in diameter with the inner pipe being 4 inches in diameter.