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9.1 Return Ductwork
DO NOT LOCATE THE RETURN DUCTWORK IN AN
AREA THAT CAN INTRODUCE TOXIC, OR OBJEC-
TIONABLE FUMES/ODORS INTO THE DUCTWORK.
The return ductwork is to be connected to the air handler
bottom (upflow configuration).
10 Return Air Filters
Each installation must include a return air filter. This filtering
may be performed at the air handler using the factory filter
rails or externally such as a return air filter grille. When us-
ing the factory filter rails, a nominal 16x20x1", 20x20x1" or
24x20x1" (actual dimension must be less than 23-½"x20")
filter can be installed on a B, C and D cabinet respectively
(the cabinet size is the seventh letter of the model number).
11 Electric Heat
Refer to the installation manual provided with the electric
heat kit for the correct installation procedure. All electric
heat must be field installed. If installing this option, the ONLY
heat kits that are permitted to be used are the HKS series.
Refer to the air handler unit's Serial and Rating plate or the
HKS specification sheets to determine the heat kits compat-
ible with a given air handler. No other accessory heat kit be-
sides the HKS series may be installed in these air handlers.
The heating mode temperature rise is dependent upon the
system airflow, the supply voltage, and the heat kit size (kW)
selected. Use data provided in Tables 5, 6, AND 7 to deter-
mine the temperature rise (°F).
NOTE: For installations not indicated above the following
formula is to be used:
TR = (kW x 3412) x (Voltage Correction) / (1.08XCFM)
Where: TR
=
kW
=
3412
=
VC*
=
=
=
1.08
=
CFM
=
*VC (Voltage Correction)
NOTE: The Temperature Rise Tables can also be used to
estimate the air handler airflow delivery. When using these
tables for this purpose set the room thermostat to maximum
heat and allow the system to reach steady state conditions.
Insert two thermometers, one in the return air and one in the
supply air. The temperature rise is the supply air tempera-
ture minus the room air temperature. Using the temperature
rise calculated, CFM can be estimated from the TR formula
above. See Service Manual for more information.
Temperature Rise
Heater Kit Actual kW
Btu per kW
.96 (230 Supply Volts)
.92 (220 Supply Volts)
.87 (208 Supply Volts)
Constant
Measured Airflow
CFM
3
5
800
12
19
1000
9
15
1200
8
12
1400
7
11
1600
6
9
1800
5
8
2000
5
7
230/1/60 SUPPLY VOLTAGE - TEMP. RISE °F
CFM
3
5
800
11
18
1000
9
14
1200
7
12
1400
6
10
1600
6
9
1800
5
8
2000
4
7
220/1/60 SUPPLY VOLTAGE - TEMP. RISE °F
CFM
3
5
800
10
17
1000
8
13
1200
7
11
1400
6
10
1600
5
8
1800
5
7
2000
4
7
208/1/60 SUPPLY VOLTAGE - TEMP. RISE °F
11
HEAT KIT NOMINAL kW
6
8
10
15 19/20 25
23
31
37
19
25
30
44
15
21
25
37
13
18
21
32
12
15
19
28
10
14
16
25
9
12
15
22
Table 5
HEAT KIT NOMINAL kW
6
8
10
15 19/20 25
22
30
35
18
24
28
42
15
20
24
35
13
17
20
30
11
15
18
27
10
13
16
24
9
12
14
21
Table 6
HEAT KIT NOMINAL kW
6
8
10
15 19/20 25
21
28
33
17
22
27
40
14
19
22
33
12
16
19
29
10
14
17
25
9
12
15
22
8
11
13
20
Table 7
49
62
42
53
37
46
33
41
30
37
47
59
40
51
35
44
31
39
28
35
45
56
38
48
33
42
30
37
27
33
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