The Heat Fab backdraft reducer (9301BFP) is the preferred option for limiting backdraft for the Bosch Condensing tankless water heaters (see fig. 22).
Note: The following solution is available only for 3" diameter venting.
For this solution to be effective, the internal flapper must be 100% closed when the water heater is not running. Refer to Figures 24 and 25 for preferred installation positions in the vent system.
• Install damper per the supplied manufacturer‘s instructions.
• The damper is only to be used in the exhaust vent piping.
• Ensure directional arrow on damper label faces in the same direction as exhaust flow.
• If installed horizontally, the axis must be horizontal or slightly pitched up towards termination to ensure damper closes 100% when heater is not running.
• To allow accessibility, damper must not be installed in an enclosed section of vent pipe.
• Do not install damper in unconditioned spaces (e.g. attics) Condensation can build up while the heater is running which can later freeze and potentially block the flapper.
The Bosch C1210ES/ESC, C1050ES & C950ES are all approved to use the Backdraft Reducer.