A.O. Smith 400 - 2100 Installation & Operation Manual page 13

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Determine unit location
Exhaust fans
Any fan or equipment which exhausts air from the equipment
room may deplete the combustion air supply and/or cause a
down draft in the venting system. Spillage of flue products from
the venting system into an occupied living space can cause a
very hazardous condition that must be immediately corrected.
If a fan is used to supply combustion air to the equipment
room, the installer must make sure that it does not cause drafts
which could lead to nuisance operational problems with the
unit.
Vertical Vent/Air, Horizontal Vent/Air, and Direct Vent
venting systems have specific requirements for combustion air
ducts from the outside which are directly connected to the unit.
See the requirements for combustion air duct in the venting
section.
Use of filters having MERV (Minimum
NOTICE
Efficiency Reporting Value) ratings higher than
4 is not recommended. Higher efficiency
low-micron filters can limit combustion
air leading to either nuisance problems or
potential component damage if used over
prolonged periods of time. Filters having
a MERV rating of 5 to 6 may be used
on a limited basis during the construction
phase of a project provided they are replaced
once filter loading becomes apparent. After
the construction phase is completed, it is
recommended that the filter be changed to a
4 or lower MERV disposable type filter.
Figure 1-7_Metal Panel Covering Side Combustion
Air Inlet
During construction the air filter should be checked more frequently to ensure it does not become clogged with
NOTICE
combustion dirt and debris.
Sustained operation of an appliance with a clogged filter may result in nuisance operational problems, bad
CAUTION
combustion, and non-warrantable component failures.
Installation & Operation Manual
(continued)
Combustion air filter
This unit has a standard air filter located at the combustion air
inlet. This filter helps ensure clean air is used for the combustion
process. Check this filter every month and replace when it
becomes dirty. The filter size on Models 400 - 750 is 12" x 12"
x 1" (30.5cm x 30.5cm x 2.5cm) and 16" x 16" x 1" (40.6cm x
40.6cm x 2.5 cm) on Models 1000 - 2100. You can find these
commercially available filters at any home center or HVAC
supply store.
For convenience and flexibility, you can direct the combustion
air inlet from either the back or right side of the unit. To arrange
the combustion air inlet for side entry, follow the steps below:
1. Remove the metal panel from the unit's side wall (see
FIG. 1-7).
2. Remove screws from the air filter/bracket assembly.
3. Move the filter/bracket assembly from the rear of unit to the
side opening (see FIG. 1-8).
4. Attach filter/bracket assembly to the unit's side using the
pre-drilled screw holes.
5. Attach the metal panel to the rear combustion air opening
to seal it off.
Figure 1-8_Moving Air Filter / Bracket Assembly from
Rear of Unit to Side
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