SERVICING
190 Rev. 3
2. If the service dill valves are to be used for evacuation, it is
recommended that a core remover be used to lift the core
for greater efficiency.
3. Start the vacuum pump and open the 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 blank-off to a
maximum of 25 microns. A high vacuum pump can only
produce a good vacuum if its oil is non-contaminated.
4. If the vacuum pump is working properly, close the valve to
the vacuum thermocouple gauge and open the high and
low side valves to the high vacuum manifold set. With
the valve on the charging cylinder closed, open the mani-
fold valve to the cylinder.
5. Evacuate the system to at least 29 inches gauge before
opening valve to thermocouple vacuum gauge.
6. Continue to evacuate to a maximum of 250 microns. Close
valve to vacuum pump and watch rate of rise. If vacuum
does not rise above 1500 microns in three to five min-
utes, system can be considered properly evacuated.
7. If thermocouple vacuum gauge continues to rise and lev-
els off at about 5000 microns, moisture and non-condens-
ables are still prevent. If gauge continues to rise a leak is
present. Repair and re-evacuate.
8. Close valve to thermocouple vacuum gauge and vacuum
pump. Shut off pump and prepare to charge.
EVACUATION
S-103 CHARGING
Charge the system with the exact amount of refrigerant.
Refer to the specification section or check the unit name-
plates for the correct refrigerant charge.
An inaccurately charged system will cause future prob-
lems.
1. When using an ambient compensated calibrated charg-
ing cylinder, allow only liquid refrigerant to enter the high
side.
2. After the system will take all it will take, close the valve
on the high side of the charging manifold.
3. Start the system and charge the balance of the refriger-
ant through the low side. DO NOT charge in a liquid
form.
4. With the system still running, close the valve on the charg-
ing cylinder. At this time, you may still have some liquid
refrigerant in the charging cylinder hose and will definitely
have liquid in the liquid hose. Reseat the liquid line core.
Slowly open the high side manifold valve and transfer the
liquid refrigerant from the liquid line hose and charging
cylinder hose into the suction service valve port. CARE-
FUL: Watch so that liquid refrigerant does not enter the
compressor.
5. With the system still running, reseat the suction valve
core, remove hose and reinstall both valve core caps.
6. Check system for leaks.
When charging a remote condensing unit with a non-match-
ing evaporator coil or a system where the charge quantity is
unknown, alternate charging methods must be used. These
systems must be charged according to subcooling or super-
heat.
Coils having capillary tubes or flow control restrictors should
be charged to match the Desired Superheat vs. Outdoor
Temperature Chart in this section. Coils with thermostatic
expansion valves (TEV's) should be charged by subcooling.
See "Checking Subcooling and Superheat" sections in this
manual.
If a restriction is located, replace the restricted part, replace
drier, evacuate and recharge.
S-104 CHECKING COMPRESSOR EFFICIENCY
The reason for compressor inefficiency is broken or dam-
aged suction and/or discharge valves, or scroll flanks on Scroll
compressors, reducing the ability of the compressor to pump
refrigerant vapor.
The condition of the valves or scroll flanks is checked in the
following manner.
1. Attach gauges to the high and low side of the system.
2. Start the system and run a "Cooling Performance Test.
If the test shows:
a. Below normal high side pressure.
b. Above normal low side pressure.
c. Low temperature difference across coil.
d. Low amp draw at compressor.
and the charge is correct. The compressor is faulty - replace
the compressor.
