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SERVICING
gauge. See that the vacuum pump will blank-off to a maxi-
mum of 25 microns. A high vacuum pump can only pro-
duce a good vacuum if its oil is non-contaminated.
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 cylinder.
4. Evacuate the system to at least 29 inches gauge before
opening valve to thermocouple vacuum gauge.
5. Continue to evacuate to a minimum 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.
S-103 CHARGING
WARNING
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.
After completing airflow measurements and adjustments, the
unit's refrigerant charge must be checked. The unit comes
factory charged, but this charge is based on 400 CFM per ton
at minimum ESP per AHRI test conditions (generally between
.15 - .25 ESP). When air quantity or ESP is different than
above, charge must be adjusted to the proper amount.
All package units are charged to the superheat method at the
compressor suction line (these are fixed orifice devices).
34
For charging in the warmer months, 10
pressor is required at conditions: 95
bulb temperature), 80
0
F dry bulb / 67
ent, approximately 50% humidity. This superheat varies when
conditions vary from the conditions described.
A superheat charge chart is available for other operating condi-
tions. Use it to provide the correct superheat at the conditions
the unit is being charged at.
After superheat is adjusted it is recommended to check unit
sub-cooling at the condenser coil liquid line out. In most oper-
ating conditions 12 + 4
0
F of sub-cooling is adequate.
An inaccurately charged system will cause future problems.
1. Using a quality set of charging scales, weigh the proper
amount of refrigerant for the system. 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 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 con-
tainer or drum in liquid form due to its fractionation proper-
ties, but should be "Flashed" to its gas state before enter-
ing the system. There are commercially available restric-
tion 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. 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. CAREFUL: Watch so that liquid refrig-
erant does not enter the compressor.
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 start-up 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 access fitting caps.
6. Check system for leaks.
Due to their design, Scroll compressors are inherently more
tolerant of liquid refrigerant.
0
F superheat at the com-
0
F outdoor ambient (dry
0
F wet bulb indoor ambi-
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