Service Manual

SERVICING
33
S-103 CHARGING
WARNING
CAUTION
Charge the system with the exact amount of refrigerant.
Refer to the specification section or check the unit nameplates
for the correct refrigerant charge.
An inaccurately charged system will cause future prob-
lems.
1. Using a calibrated set of refrigerant scales, allow liquid re-
frigerant 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 charging manifold.
3. Start the system and charge the balance of the refrigerant
through the low side.
NOTE: R410A should be drawn out of the storage container or
drum in liquid form due to its fractionation properties, but should
be "Flashed" to its gas state before entering the system. There
are commercially available restriction devices that fit into the
system charging hose set to accomplish this. DO NOT charge
liquid R410A into the compressor.
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 cyl-
inder hose into the suction service valve port. CAREFUL:
Watch so that liquid refrigerant does not enter the com-
pressor.
Final Charge Adjustment
The outdoor temperature must be 60°F or higher. Set the room
thermostat to COOL, fan switch to AUTO, and set the tem-
perature control well below room temperature.
After system has stabilized per startup instructions, compare
the operating pressures and outdoor unit amp draw to the num-
bers listed in the technical manual. If pressures and amp draw
are too low, add charge. If pressures and amp draw are too
high, remove charge. Check subcooling and superheat as de-
tailed in the following section.
5. With the system still running, remove hose and reinstall
both valve caps.
6. Check system for leaks.
Due to their design, Scroll compressors are inherently more
tolerant of liquid refrigerant.
NOTE: Even though the compressor section of a Scroll com-
pressor is more tolerant of liquid refrigerant, continued flood-
back or flooded start conditions may wash oil from the bearing
surfaces causing premature bearing failure.
S-104 CHECKING COMPRESSOR
EFFICIENCY
The reason for compressor inefficiency is broken or damaged
suction and/or discharge valves, or scroll flanks on Scroll com-
pressors, reducing the ability of the compressor to pump re-
frigerant 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-
⇒
Below normal high side pressure.
⇒
Above normal low side pressure.
⇒
Low temperature difference across coil.
⇒
Low amp draw at compressor.
-and the charge is correct. The compressor is faulty - replace
the compressor.