2 2 |
Bosch 96% AFUE Gas Furnace
Installation, Operation & Maintenance
04.2019
|
Bosch Thermotechnology Corp.
Data subject to change
7.4 Filter Arrangement
CAUTION: FIRE HAZARD
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
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 fi lter from the
manufacturer. The fi lter and fi lter rack must be fi eld supplied and fi eld installed. A
high velocity fi lter is recommended, see recommended fi lter size and type in Table
2. One of the most common causes of furnace malfunctions is a blocked or dirty
fi lter. The fi lter must be inspected monthly for dirt accumulation and replaced if
necessary.
Filter type
Air velocity through disposable fi lters may not exceed 300 feet per minute (FPM).
All velocities over this require the use of high velocity fi lters. If a normal speed
disposable fi lter 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 airfl ow, refer
to Tables 3 & 4.
NOTICE:
If disposable fi lters are used, air passage through fi lters
should be increased to twice the size of original air
opening by using a transition duct or using two fi lters in V
shape (see Fig. 19) in normal duct size.
Figure 19
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 2
Manufacturer recommended high velocity
fi
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 20, "Side Return Knockout Markings".
Figure 20
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 fi lter rack (fi eld supplied) following the instructions provided with
that accessory. If a fi lter(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
fi
lters
Filter(s) may be located in the duct system outside the furnace using an external
duct fi lter box attached to the furnace plenum or at the end of the duct in a return
fi lter grille(s). The use of straps and/or supports is required to support the weight
of the external fi lter box.
