44
SERVICING
1. Connect the vacuum pump, vacuum tight manifold set
with high vacuum hoses, thermocouple vacuum gauge
and charging cylinder.
2. Connect the low side line to the process tube of the
compressor.
3. Connect the high side line to the process tube of liquid
line strainer.
NOTE:
If either process tube is not long enough to receive
the compression or flare fitting and still leave room for a
pinch-off, swag the tube and braze in an extra length of
tubing.
4. Start the vacuum pump and open shut off valve to the
high vacuum gauge manifold only. After the compound
gauge (low side) has dropped to approximately 29 inches
of vacuum open the valve to the vacuum thermocouple
gauge. See that the vacuum pump will bank-off to a
minimum of 50 microns. A high vacuum pump can only
produce a good vacuum if its oil is not contaminated.
5. If the vacuum pump is working properly, close the valve
to the vacuum thermocouple gauge and open the high
and low side valves or the high vacuum manifold set.
With the valve on the charging cylinder closed, open
the manifold valve to the cylinder.
6. Evacuate the system to at least 29 inches gauge before
opening valve to thermocouple vacuum gauge.
7. Continue to evacuate to a minimum of 250 microns.
Close valve pump and watch rate of rise. If vacuum
does not rise above 1500 microns in three minutes,
system can be considered properly evacuated.
8. If thermocouple vacuum gauge continues to rise and
levels off at about 5000 microns, moisture and non-
condensables are still present. If gauge continues to
rise a leak is present. Repair and re-evacuate.
9. Close valve to thermocouple vacuum gauge and vacuum
pump. Shut off pump and prepare to charge.
Charging
Charge the system with the exact amount of refrigerant.
Refer to the unit nameplate for the correct refrigerant
charge. An inaccurately charged system will cause future
problems.
1. When using an ambient compensated calibrated charg-
ing cylinder, allow liquid refrigerant only to enter the
high side.
2. After the system will take all it will take, close the valve
on the high side of the manifold.
3. Start the system and charge the balance of the refrig-
erant though the low side. Do not charge in a liquid
form.
4. Close the low side valve on the manifold and pinch-off
both process tubes. Remove the manifold set, crimp
shut the open ends of the process tubes and braze.
5. Recheck for refrigerant leaks.
NOTE:
Do not use a refrigerant other than that shown on
the serial number identification plate.
All precautionary measures recommended by the refriger-
ant manufacturers and suppliers should be observed.
Line Piercing Valves
Line piercing valves may be used for diagnosis but are not
suitable for evacuating or charging due to the minute holes
pierced in the tubing.
Line piercing valves must not be left on the refrigerant sys-
tem. The connection between the valve and the refrigerant
tubing is not hermetically sealed and will eventually leak.
Open Lines
During any processing of the refrigeration system the lines
should never be left open to atmosphere since water vapor
will enter and add to the problem of proper evacuation.
Operating Test
The final step in a successful repair is an accurate operat-
ing test. Follow the Cooling and Heating Performance tests
provided to make sure the product is again performing to
design standards.
WARNING
NEVER TEST OPERATION WITHOUT THE UNIT IN
THE WALL SLEEVE. A SERIOUS CHANGE IN DESIGN
SPECIFICATIONS FOR AIR MOVEMENT THROUGH
THE EVAPORATOR AND CONDENSER COMPART-
MENTS, CAUSING THE FAN MOTOR TO OVER HEAT
AND THE REFRIGERATION SYSTEM TO BECOME
UNBALANCED WILL OCCUR WHEN THE UNIT IS
NOT INSTALLED IN THE WALL SLEEVE.
Efficient operation is dependent on a balanced system. One
of the most common reasons for inefficiency is the users
failure to adequately clean the condenser thereby creating
reduced air movement.
Cooling Performance Test Thermometers
The following precautions are necessary in observing the
thermometer readings in the cooling performance test.
1. Use two accurately calibrated refrigeration type ther-
mometers or a thermocouple potentiometer.
2. Thermometers are affected by body heat or changes in
air flow. Therefore, the thermometers must be secured
in proper locations with masking tape, wire or other
applicable retainers.
3. Readings should be observed without touching or mov-
ing the thermometers.
