Service manual

SERVICING
34
NOTE: If the board is powered up with the jumper con-
nected to the test pins, the board will ignore test and de-
fault to 90 minute time. If the jumper is left on the test con-
nection for more than ten minutes, the board will ignore
test jumper and default to 90 minute time. If jumper is miss-
ing, the board will default to 90 minute time.
6. Whenever the (CC) compressor contactor is energized,
the solid state timer counts the compressor run time.
Total accumulated minutes (run time) is retained as long
as the Defrost (30/60) control stays closed. With the
jumper connected to the 90 minute pins, the compres-
sor run time is 90 minutes (factory wired). The board
has jumper pin for 60 and 30 minute times as well. Timer
count time may be accelerated for testing only, by plac-
ing jumper on test pins. (Example: 90 minutes = ap-
proximately 21 seconds). Remove the jumper when the
board goes into defrost mode. If the jumper is not re-
moved, the timer will remain accelerated through the
defrost period.
7. At end of the programmed time, common circuit (C) is
made to the (OUT) terminal. The reversing solenoid be-
comes energized and will stay energized until defrost
(30/60) control opens by coil temperature, or after 10
minutes of run time. Maximum defrost time limited to 10
minutes compressor run time. During the defrost time,
the board will apply power to the "W" terminal to bring
on supplemental electric heat (if installed).
8. The control de-energizes the indoor blower 60 seconds
after the call for heating is removed.
S-24 TESTING DEFROST BOARD
To check the defrost timer board for proper sequencing,
proceed as follows: With power ON; unit not running.
1. Jumper defrost (30/60 control by placing a jumper wire
across "DF" terminals.) terminal 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 across OUT Terminals
(BK-19 & BK-20). meter should read 24 volts.
6. Using VOM check for voltage across Fan terminals on
the board (VT-62 & VT-16). 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 "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 re-
place jumper to 30, 60, or 90 minute position before return-
ing system 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 auto-
matic rest limit control connected in series with each ele-
ment to prevent overheating of components in case of low
airflow. This limit control will open its circuit at approxi-
mately 150°F. and close at 110°F.
WARNING
Disconnect Electrical Power Supply:
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 re-
sistance 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
Disconnect Electrical Power Supply:
1. Disassemble and remove the heating element.
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
reading indicates the element is open. Replace as nec-
essary.
See "Electric Heater" in the Product Design Section (page
23) to verify heater amperage and temperature rise.