Bosch Greentherm T9900 SE 160 Installation And Operating Instructions Manual page 31

NOTICE:
A blocked breather may cause an undesired double-siphon
effect.
▶ Ensure that the breather included in the siphon is not
obstructed to allow correct function.
Verify condensate disposal/neutralization is in accordance with
federal, State, and local regulation.
This is a high efficiency appliance, condensate flow can be as
much as 2.1 gal/hr at full power.
4.6.6 Backdraft reducer
The backdraft reducer (9301BFP) is the preferred option for
limiting backdraft (see fig. 21).
The backdraft reducer (9301BFP) is sized for 3" diameter PVC.
It is possible to use Backdraft reducer (9301BFP) for 2"
installations.
This requires 2" to 3" adapters.
Fig. 21 Part # 9301BFP
Installation
For this solution to be effective, the internal flapper must be
100% closed when the water heater is not running.
Greentherm T9900 SE/i – 6 720 813 635 (2019/03)
Refer to fig. 23 for preferred installation positions in the vent
system.
Installation considerations:
▶ Install the damper per the supplied manufacturer's
▶ Ensure directional arrow on damper label faces in the same
▶ If installed horizontally, the axis must be horizontal or
▶ To allow accessibility, the damper must not be installed in
▶ Do not install the damper in unconditioned spaces (e.g.
Fig. 22
6720608643-18.1V
Fig. 23
[1] Good
[2] Better
[3] Best
instructions.
The damper is only to be used in the exhaust vent piping.
direction as exhaust flow.
slightly pitched up towards termination to ensure damper
closes 100% when heater is not running.
an enclosed section of vent pipe.
attics) Condensation can build up while the heater is
running which can later freeze and potentially block the
flapper.
Blackflow reducer (9301BFP) installed
Installation Recommendation for Placement of
Backdraft reducer
Installation instructions
6720608643-19.1V
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