Bosch BGH96M080C4B - Filter Arrangement

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Installation Instructions
Bosch 96% AFUE Condensing Gas Furnace - BTC 770503101 J (06.2023)
7.4 Filter Arrangement
CAUTION: FIRE HAZARD
f Never install a filter on the supply air side. Filters should
always be installed on return air side of system.
WARNING: CARBON MONOXIDE AND POISONING HAZARD
f Never operate a furnace without a filter or with filter
access door removed.
Filter size
The Bosch 96% AFUE Gas Furnace BGH96 series does not include a filter from the
manufacturer. The filter and filter rack must be field supplied and field installed. A
high velocity filter is recommended, see recommended filter size and type in Table
2. One of the most common causes of furnace malfunctions is a blocked or dirty
filter. The filter must be inspected monthly for dirt accumulation and replaced if
necessary.
Filter type
Air velocity through disposable filters may not exceed 300 feet per minute (FPM).
All velocities over this require the use of high velocity filters. If a normal speed
disposable filter is used and air speed exceeds 300 feet per minute (FPM), two side
returns or one side return and the bottom return may be needed. For airflow, refer
to Tables 4 & 5.
NOTICE:
f If disposable filters are used, air passage through filters
should be increased to twice the size of original air
opening by using a transition duct or using two filters in V
shape (see Fig. 20) in normal duct size.
Figure 20
Furnace cabinet width
Filter size
Filter type
Side return Bottom return
17-1/2 16X25 16X25 High Velocity (600 FPM)
21 16X25 20X25 High Velocity (600 FPM)
24.5 16X25 24X25 High Velocity (600 FPM)
Table 3 Manufacturer recommended high velocity lter sizes - Inch
Side return
Locate the 4 knockout locations. These indicate the size of the cut-out to be made
in the furnace side panel. Refer to Fig 21, "Side Return Knockout Markings".
Figure 21
Front of
Furnace
Cut out for
side return
Side return knockout markings
Dimensions of return air "cut out" must match those shown in Figure 1.
DO NOT cut outside of the "knockout" markings.
Install the side filter rack (field supplied) following the instructions provided with
that accessory. If a filter(s) is provided at another location in the return air system,
the duct work may be directly attached to the furnace side panel.
Bottom Return lters
Filter(s) may be located in the duct system outside the furnace using an external
duct filter box attached to the furnace plenum or at the end of the duct in a return
filter grille(s). The use of straps and/or supports is required to support the weight
of the external filter box.