Manual 2100-422N
Page
32 of 42
AIR FILTERS
Only Lo-Boy models are shipped with air filters. Filter
kits are available from your local distributor for
Upflow and Counterflow models. Knockouts are
provided in the sides of the FH series models to
facilitate the cutting of the return openings.
The upflow filter kit part numbers are FR23 for a
16x25x1 filter size and FR24 for a 20x25x1 filter size.
These filter kits come complete with the filter and all
necessary brackets for installing on the furnace. Each
comes with a washable aluminum mesh filter. When
installing a five ton AC unit on the furnace, one FR24
or Two FR23 must be used due to the high airflow
requirements. It is important to note that a minimum of
one inch spacing is required between the filter and the
unit side. Do not exceed 400 fpm for fiberglass
(disposable) type filters and 575 fpm for washable type
filters. See Figure 16.
The counterflow filter kit part number FR25 comes
with two washable filters. If not installing the FR25 kit
remember not to exceed 400 fpm for fiberglass
(disposable) type filters and 575 for washable type
filters. See Figure 17.
See Table 11 for filter sizes and quantities.
FIGURE 17
TYPICAL INSTALLATION OF FR25
FILTER KIT
70 5/16"
Optional
Filter
Box
"FC"
Unit
MIS-1841
TABLE 11
FILTER SIZES FOR OIL FURNACES
l
e
d
o
M
e
z
i
S
F
6
3
D
5
8
0
H
F
y
o
B
-
i
H
)
1
(
1
x
5
2
x
6
1
F
8
4
D
0
1
1
H
F
y
o
B
-
i
H
)
1
(
1
x
5
2
x
6
1
F
0
6
D
0
1
1
H
F
y
o
B
-
i
H
)
1
(
1
x
5
2
x
0
2
F
6
3
D
5
8
0
F
L
F
F
6
3
D
5
8
0
R
L
F
s
y
o
B
-
o
L
)
1
(
2
x
0
2
x
6
1
F
8
4
D
0
1
1
F
L
F
F
8
4
D
0
1
1
R
L
F
F
0
6
D
0
1
1
F
L
F
F
0
6
D
0
1
1
R
L
F
s
y
o
B
-
o
L
)
1
(
2
x
0
2
x
0
2
F
0
6
D
0
4
1
R
L
F
y
o
B
-
o
L
)
1
(
2
x
5
2
x
0
2
F
6
3
D
5
8
0
C
F
w
o
l
f
r
e
t
n
u
o
C
)
2
(
1
x
0
2
x
6
1
16"
19 1/4"
Filter
Frame
Filter
Filter
Door
(2) screws
MIS-1839 A
FIGURE 16
TYPICAL INSTALLATION OF FR26 AND
FR27 FILTER RACKS
