SERVICING
49
7. Using VOM check for voltage across "W & C" terminals
on the board. You should read 24 volts.
8. If not as above, replace control board.
9. Set thermostat to off position and disconnect power be-
fore removing any jumpers or wires.
NOTE: Remove jumper across defrost thermostat and replace
jumper to 30, 60, or 90 minute position before returning sys-
tem to service.
UTEC Defrost Control
UTEC Defrost Board
1. Jumper defrost (30/60) control by placing a jumper wire
across "DFT" terminals at defrost timer board.
2. Connect jumper across test pins on defrost control board.
3. Set thermostat to call for heating. System should go into
defrost within 21 seconds.
4. Immediately remove jumper from test pins.
5. Using VOM check for voltage between the "C" and "O"
terminals on the board. Meter should read 24 volts.
6. Using VOM check for voltage between the "DF1" and
"DF2" terminals on the board. You should read line volt-
age (208-230 VAC) indicating the relay is open in the
defrost mode.
7. Using VOM check for voltage across "W2 & C" terminals
on the board. You should read 24 volts.
8. If not as above, replace control board.
9. Set thermostat to off position and disconnect power be-
fore removing any jumpers or wires.
NOTE: Remove jumper across defrost thermostat and replace
jumper to 30, 60, or 90 minute position before returning sys-
tem to service.
S-25 TESTING DEFROST CONTROL (30°/60°)
1. Install a thermocouple type temperature test lead on the
tube adjacent to the defrost control. Insulate the lead
point of contact.
2. Check the temperature at which the control closes its
contacts (30°F. ± 5°F.)
3. Raise the temperature of the control until opens
(60°F. ± 5°F.)
4. If not as above, replace control.
S-50 CHECKING HEATER LIMIT CONTROL(S)
(OPTIONAL ELECTRIC HEATERS)
Each individual heater element is protected with an automatic
reset limit control connected in series with each element to
prevent overheating of components in case of low airflow. This
limit control will open its circuit at approximately 150°F. and
close at 110°F,
WARNING
HIGH
VOLTAGE
D
ISCONNECT
ALL
POWER BEFORE SERVICING OR
INSTALLING THIS UNIT.
M
ULTIPLE POWER SOURCES MAY
BE PRESENT.
F
AILURE TO DO SO MAY CAUSE PROPERTY
DAMAGE, PERSONAL INJURY OR DEATH.
1. Remove the wiring from the control terminals.
2. Using an ohmmeter test for continuity across the nor-
mally closed contacts. No reading indicates the control
is open - replace if necessary.
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 specifications section to provide electric resis-
tance heating. Under no condition shall more heaters than
the quantity shown be installed.
The low voltage circuit in the blower section is factory wired
and terminates at the location provided for the electric
heater(s).
WARNING
HIGH
VOLTAGE
D
ISCONNECT
ALL
POWER BEFORE SERVICING OR
INSTALLING THIS UNIT.
M
ULTIPLE POWER SOURCES MAY
BE PRESENT.
F
AILURE TO DO SO MAY CAUSE PROPERTY
DAMAGE, PERSONAL INJURY OR DEATH.
1. Dissemble and remove the heating element.
2. Visually inspect the heater assembly for any breaks in
the wire or broken insulators.
