SERVICING
40
S-50 CHECKING HEATER LIMIT CONTROL(S) (OPTIONAL
ELECTRIC HEATERS)
Each individual heater element is protected with an automatic
rest limit control connected in series with each element to prevent
overheating of components in case of low airflow. This limit con-
trol will open its circuit at approximately 150
°
F. to 160
°
F and
close at approximately 110
°
F.
WARNING
Disconnect ALL power before servicing.
1. Remove the wiring from the control terminals.
2. Using an ohmmeter test for continuity across the normally
closed contacts. No reading indicates the control is open -
replace if necessary. Make sure the limits are cool before
testing.
IF FOUND OPEN - REPLACE - DO NOT WIRE AROUND
.
S-52 CHECKING HEATER ELEMENTS
Optional electric heaters may be added, in the quantities shown
in the spec sheet for each model unit, to provide electric resis-
tance heating. Under no condition shall more heaters than the
quantity shown be installed.
HIGH VOLTAGE!
Disconnect ALL power before servicing
or installing. Multiple power sources
may be present. Failure to do so may
cause property damage, personal injury
or death.
1. Disassemble and remove the heating element(s).
2. Visually inspect the heater assembly for any breaks in the
wire or broken insulators.
3. Using an ohmmeter, test the element for continuity - no read-
ing indicates the element is open. Replace as necessary.
S-60 ELECTRIC HEATER (OPTIONAL ITEM)
Optional electric heaters may be added, in the quantities shown
in the specifications section, to provide electric resistance heat-
ing. 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 pres-
sure 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 measured.
Alternately, the system CFM can be determined by operating the
electric heaters and indoor blower WITHOUT having the com-
pressor 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
in the following chart.
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
TEMPERA-
TURE RISE
chart on the right.
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 installations.
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.
3
5
6
8
10
15
19/20
25
800
12
19
23
31
37
1000
9
15
19
25
30
44
1200
8
12
15
21
25
37
49
62
1400
7
11
13
18
21
32
42
53
1600
6
9
12
15
19
28
37
46
1800
5
8
10
14
16
25
33
41
2000
5
7
9
12
15
22
30
37
CFM
HEAT KIT NOMINAL kW
230/1/60 SUPPLY VOLTAGE - TEMP. RISE
°
F
