SERVICING
20
4. Immediately remove jumper from test pins.
5. Using VOM check for voltage across terminals “C &
O”. Meter should read 24 volts.
6. Using VOM check for voltage across fan terminals
DF1 and DF2 on the board. You should read line
voltage (208-230 VAC) indicating the relay is open in
the defrost mode.
7. Using VOM check for voltage across “W”/”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.
Remove jumper from defrost thermostat and replace
timer jumper to the desired defrost time.
NOTE: Remove jumper across defrost thermostat
before returning system to service.
Testing Defrost Thermostat
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 by lowering the temperature of the control.
The defrost control should close at approximately
30°F.
3. Check the temperature at which the control opens
its contacts by raising the temperature of the control.
The defrost control should open at approximately
60°F.
4. If not as above, replace control.
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 control 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.
Checking Heater Elements
Optional electric heaters may be added, in the quantities
shown in the spec sheet for each model unit, to provide
electric resistance heating. Under no condition shall more
heaters than the quantity shown be installed.
WARNING
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 reading indicates the element is open. Replace as
necessary.
Refrigeration Repair Practice
DANGER
Always remove the refrigerant charge in a proper manner
before applying heat to the system.
These models use the FasTest Access Fitting System,
with a saddle that is either soldered to the suction and
liquid lines or is fastened with a locking nut to the access
fitting box (core) and then screwed into the saddle.
Do not
remove the core from the saddle until the refrigerant
charge has been removed. Failure to do so could result
in property damage or personal injury.
When installing a new core or reinstalling the core after
removal, it is very important to note that before inserting
the core into the saddle, the core and saddle must be
free of debris and the “O” Ring
must
have a thin coating
of refrigerant oil applied to it. The oil is to prevent the “O”
Ring from being deformed when the core is tightened
completely. The core should be torqued to 8 ft. lb.
When repairing the refrigeration system:
1. Never open a system that is under vacuum. Air and
moisture will be drawn in.
2. Plug or cap all openings.
3. Remove all burrs and clean the brazing surfaces of
the tubing with sand cloth or paper. Brazing materials
do not flow well on oxidized or oily surfaces.
4. Clean the inside of all new tubing to remove oils and
pipe chips.
5. When brazing, sweep the tubing with dry nitrogen
to prevent the formation of oxides on the inside
surfaces.
6. Complete any repair by replacing the liquid line drier
in the system, evacuate and charge.
