66832-UIM-D-1205
Unitary Products Group
7
TABLES 2 and 3 are to be used as a guide only to help the installer
determine if the duct sizes are large enough to obtain the proper air flow
(CFM) through the furnace. TABLES 2 and 3 ARE NOT to be used to
design ductwork for the building where the furnace is being installed.
There are several variables associated with proper duct sizing that are
not included in the tables. To properly design the ductwork for the build-
ing, Refer to the ASHRAE Fundamentals Handbook, Chapter on
“DUCT DESIGN” or a company that specializes in Residential and Mod-
ular Home duct designs.
IMPORTANT: The minimum plenum height is 12" (30.5). The furnace
will not operate properly on a shorter plenum height. The minimum rec-
ommended rectangular duct height is 4 inches (10 cm) attached to the
plenum.
IMPORTANT: The air temperature rise should be taken only after the
furnace has been operating for at least 15 minutes. Temperatures and
external static pressures should be taken 6" (15 cm) past the first bend
from the furnace in the supply duct and the return duct. If an external fil-
ter box or an electronic air cleaner is installed, take the return air read-
ings before the filter box or air cleaner.
I
If a matching cooling coil is used, it may be place directly on the furnace
outlet and sealed to prevent leakage. Follow the coil instructions for
installing the supply plenum. On all installations without a coil, a remov-
able access panel is recommended in the outlet duct such that smoke
or reflected light would be observable inside the casing to indicate the
presence of leaks in the heat exchanger. This access cover shall be
attached in such a manner as to prevent leaks.
The supply air temperature MUST NEVER exceed the Maximum
Supply Air Temperature, specified on the nameplate.
Operating the furnace above the maximum supply air temperature
will cause the heat exchanger to overheat, causing premature heat
exchanger failure. Improper duct sizing, dirty air filters, incorrect
manifold pressure, incorrect gas orifice and/or a faulty limit switch
can cause the furnace to operate above the maximum supply air
temperature. Refer to sections II, III and IX for additional informa-
tion on correcting the problem.
FIGURE 5: Dimensions
DOWNFLOW
UPFLOW
A
A
B
E
D
BOTTOM VIEW
F
G
29-3/4
29-3/4
C
31-1/2
31-1/2
14
BOTTOM VIEW
H
J
16-1/4
TABLE 4: Cabinet and Duct Dimensions
BTUH (kW)
Input/Output
Nominal
CFM (m
3
/min)
Cabinet
Size
Cabinet Dimension
A(in.)
A(cm)
B(in.)
B(cm)
C(in.)
C(cm)
D(in.)
D(cm)
E(in.)
E(cm)
50/40 (14.7/11.7)
1
1200 (33.98)
B
17 1/2
44.4
16 1/2
41.9
20 3/8
51.8
20.0
50.8
16
40.6
75/60 (22.0/17.6)
1
1200 (33.98)
B
17 1/2
44.5
16 1/2
41.9
20 3/8
51.8
20.0
50.8
16
40.6
75/60 (22.0/17.6)
1
1600 (45.31)
C
21
53.3
20
50.8
20 3/8
51.8
20.0
50.8
19 1/2
49.5
100/80 (29.3/23.4)
1
1600 (45.31)
C
21
53.3
20
50.8
20 3/8
51.8
20.0
50.8
19 1/2
49.5
100/80 (29.3/23.4)
1
2000 (58.63)
D
24.5
62.2
23 1/2
59.7
20 3/8
51.8
20.0
50.8
23
58.4
125/100 (36.6/29.3)
1
2000 (58.63)
D
24.5
62.2
23 1/2
59.7
20 3/8
51.8
20.0
50.8
23
58.4
150/120 (44.0/35.2)
2
2000 (58.63)
D
24 1/2
62.2
23 1/2
59.7
20 3/8
51.8
20.0
50.8
23
58.4
BTUH (kW)
Input/Output
Nominal
CFM (m
3
/min)
Cabinet
Size
K Vent
(in.)
K Vent
(cm)
F(in.)
F(cm)
G(in.)
G(cm)
H(in.)
H(cm)
J(in.)
J(cm)
50/40 (14.7/11.7)
1
1200 (33.98)
B
14 3/4
37.46
18 3/4
47.62
15 1/8
38.4
19.0
48.2
3
7.62
75/60 (22.0/17.6)
1
1200 (33.98)
B
14 3/4
37.46
18 3/4
47.62
15 1/8
38.4
19.0
48.2
4
3
10.16
2
75/60 (22.0/17.6)
1
1600 (45.31)
C
18 1/4
46.35
18 3/4
47.62
18 5/8
47.3
19.0
48.2
4
2
10.16
2
100/80 (29.3/23.4)
1
1600 (45.31)
C
18 1/4
46.35
18 3/4
47.62
18 5/8
47.3
19.0
48.2
4
2
10.16
2
100/80 (29.3/23.4)
1
2000 (58.63)
D
21 3/4
55.24
18 3/4
47.62
22 1/8
56.2
19.0
48.2
4
2
10.16
2
125/100 (36.6/29.3)
1
2000 (58.63)
D
21 3/4
55.24
18 3/4
47.62
22 1/8
56.2
19.0
48.2
5
2
12.7
2
150/120 (44.0/35.2)
3
2000 (58.63)
D
21 3/4
55.24
18 3/4
47.62
22 1/8
56.2
19.0
48.2
5
2
12.7
2
1. 4-position models may be factory configured as upflow (MU) or downflow (MD).
2. All models are supplied with 3” (7.62 cm) vent connections. An installer supplied transition to 4” (10.16 cm) or 5” (12.7 cm) must be used where necessary.
3. 3-position 150 MBH model available only in upflow/horizontal (UH) configuration.
4. Dimensions “B”, “C”, “D”, and “E” are with duct flanges turned up. “F”, “G”, “H”, & “J” are with flanges flat.
