Bosch 940 ES Installation Manual page 18

Installation instructions
Solution One
The Z-flex vent termination hood is the preferred option
for limiting backdraft under the following conditions
(see Fig. 23):
• The vent hood is only to be used in the exhaust vent
piping.
• The vent hood can only be used for horizontal termi-
nations.
• The vent hood is able to meet the required clear-
ances outlined in the venting section of the water
heater's installation manual.
Fig. 23 Part nr. 2SVSHTD03 for 3" venting
Part nr. 2SVSHTD04 for 4" venting
Solution Two
If the required clearances of the Zflex termination hood
cannot be met, the Zflex damper is the preferred alter-
native (see Fig. 24).
Fig. 24 Part nr. 2ZVBP03 for 3" venting
Part nr. 2ZVBP04 for 4" venting
Installation
For these solutions to be effective, the internal flapper
must be 100% closed when the water heater is not run-
ning. Refer to Fig. 25 and 26 for preferred installation
positions in the vent system.
If using the Zflex damper:
• 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.
18
• 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.
6720608542-07.1V
Fig. 25 Combustion air piping not shown for clarity
Good - Vertical directly on top of the heater.
Better - Closer to the termination horizontally installed in a condi-
Best
6720608542-08.1V
purposes
tioned space.
- Closer to the termination vertically installed in a conditioned
space.
6720608542-06.1V
6 720 644 930