SERVICING
41
5.4
When a defrost cycle is initiated, the contacts of the
HVDR relay on the defrost board open and turns off the
outdoor fan. The contacts of the LVDR relay on the
defrost board closes and supplies 24Vac to “O” and “W2”.
The reversing valve is energized and the contacts on HR1
close and turns on the electric heater(s). The unit will
continue to run in this mode until the defrost cycle is
completed.
5.5
When the temperature of the outdoor coil rises high
enough to causes the defrost thermostat to open, the
defrost cycle will be terminated. If at the end of the
programmed 10 minute override time the defrost thermo-
stat is still closed, the defrost board will automatically
terminate the defrost cycle.
5.6
When the defrost cycle is terminated, the contacts of the
HVDR relay on the defrost board will close to start the
outdoor fan and the contacts of the LVDR relay will open
and turn off the reversing valve and electric heater(s). The
unit will now be back in a normal heating mode with a heat
pump demand for heating as described in the Heating
Operation in section 4.
S-60 ELECTRIC HEATER (OPTIONAL ITEM)
Optional electric heaters may be added, in the quantities
shown in the specifications section, to provide electric
resistance heating. Under no condition shall more heaters
than the quantity shown be installed.
The low voltage circuit in the air handler is factory wired and
terminates at the location provided for the electric heater(s).
A minimum of field wiring is required to complete the
installation.
Other components such as a Heating/Cooling Thermostat
and Outdoor Thermostats are available to complete the
installation.
The system CFM can be determined by measuring the static
pressure external to the unit. The installation manual
supplied with the blower coil, or the blower performance table
in the service manual, shows the CFM for the static mea-
sured.
Alternately, the system CFM can be determined by operat-
ing the electric heaters and indoor blower WITHOUT having
the compressor in operation. Measure the temperature rise
as close to the blower inlet and outlet as possible.
If other than a 240V power supply is used, refer to the
BTUH
CAPACITY CORRECTION FACTOR
chart below.
BTUH CAPACITY CORRECTION FACTOR
SUPPLY VOLTAGE
250
230
220
208
MULTIPLICATION FACTOR
1.08
.92
.84
.75
EXAMPLE:
Five (5) heaters provide 24.0 KW at the rated
240V. Our actual measured voltage is 220V, and our
measured temperature rise is 42°F. Find the actual CFM:
Answer:
24.0KW, 42°F Rise, 240 V = 1800 CFM from the
TEMPERATURE RISE
CHART, Table 5.
Heating output at 220 V = 24.0KW x 3.413 x .84 = 68.8
MBH.
Actual CFM = 1800 x .84 Corr. Factor = 1400 CFM.
NOTE:
The temperature rise table is for sea level installa-
tions. The temperature rise at a particular KW and CFM will
be greater at high altitudes, while the external static pressure
at a particular CFM will be less.
TEMPERATURE RISE (F°) @ 240V
CFM
4.8
KW
7.2
KW
9.6
KW
14.4
KW
19.2
KW
24.0
KW
28.8
KW
600
25
38
51
-
-
-
-
700
22
33
43
-
-
-
-
800
19
29
38
57
-
-
-
900
17
26
34
51
-
-
-
1000
15
23
30
46
-
-
-
1100
14
21
27
41
55
-
-
1200
13
19
25
38
50
-
-
1300
12
18
23
35
46
-
-
1400
11
16
22
32
43
54
65
1500
10
15
20
30
40
50
60
1600
9
14
19
28
38
47
57
1700
9
14
18
27
36
44
53
1800
8
13
17
25
34
42
50
1900
8
12
16
24
32
40
48
2000
8
12
15
23
30
38
45
2100
7
11
14
22
29
36
43
2200
7
11
14
21
27
34
41
2300
7
10
13
20
26
33
39
Table 5
HTR
KW
3.0
KW
4.7
KW
6.0
KW
7.0
KW
9.5
KW
14.2
KW
19.5
KW
21.0
KW
BTUH 10200 16200 20400 23800 32400 48600 66500 71600
ELECTRIC HEATER CAPACITY BTUH
Table 6
FORMULAS:
Heating Output = KW x 3413 x Corr. Factor
Actual CFM = CFM (from table) x Corr. Factor
BTUH = KW x 3413
BTUH = CFM x 1.08 x Temperature Rise (T)
CFM = KW x 3413
1.08 x T
T = BTUH
CFM x 1.08
