SERVICING
49
S-102
EVACUATION
WARNING
REFRIGERANT UNDER PRESSURE!
Failure to follow proper procedures may cause
property damage, personal injury or death.
IMPORTANT NOTE:
Because of the potential damage to compres-
sors, do not allow suction pressure at service valve to drop below 5
PSIG when pumping unit system down for repair. Outdoor section,
depending on line set length and amount of charge in system, may
not be able to hold the entire system charge.
This is the most important part of the entire service procedure.
The life and efficiency of the equipment is dependent upon the
thoroughness exercised by the serviceman when evacuating air
(non-condensables) and moisture from the system.
Air in a system causes high condensing temperature and pres-
sure, resulting in increased power input and reduced performance.
Moisture chemically reacts with the refrigerant oil to form corro-
sive acids. These acids attack motor windings and parts, causing
breakdown.
The equipment required to thoroughly evacuate the system is a
high vacuum pump, capable of producing a vacuum equivalent to
25 microns absolute and a thermocouple vacuum gauge to give a
true reading of the vacuum in the system
NOTE:
Never use the system compressor as a vacuum pump or
run when under a high vacuum. Motor damage could occur.
1. Connect the vacuum pump, vacuum tight manifold set with
high vacuum hoses, thermocouple vacuum gauge and charg-
ing cylinder as shown.
2. 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.
LOW SIDE
GAUGE
AND VALVE
HIGH SIDE
GAUGE
AND VALVE
TO
UNIT SERVICE
VALVE PORTS
VACUUM PUMP
VACUUM PUMP
ADAPTER
800 PSI
RATED
HOSES
CHARGING
CYLINDER
AND SCALE
EVACUATION
3. 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 manifold valve to the cyl-
inder.
4. Evacuate the system to at least 29 inches gauge before open-
ing valve to thermocouple vacuum gauge.
5. 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 minutes, system
can be considered properly evacuated.
6. 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.
7. Close valve to thermocouple vacuum gauge and vacuum pump.
Shut off pump and prepare to charge.
