GPGM3 Installation Manual
20
Refrigerant Charge Check
the unit’s refrigerant charge must be checked. The unit
comes factory charged, but this charge is based on 325
CFM per ton and minimum ESP per AHRI test conditions
the compressor suction line.
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SUBCOOLING FORMULA = SATURATED LIQUID LINE
TEMPERATURE - LIQUID LINE TEMPERATURE
EXAMPLE:
a. Liquid Line Pressure = 417 PSI
b. Corresponding Temp. = 120°F
c. Thermometer on Liquid line = 109°F.
To obtain the amount of subcooling, subtract 109°F from
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tion sheet or technical information manual for the design
subcooling range for your unit.
EXAMPLE:
a. Suction Pressure = 143 PSI
b. Corresponding Temp. = 50°F
c. Thermometer on Suction Line = 59°F
To obtain the degrees temperature of superheat, subtract
Superheat would fall in the ± range of allowable superheat.
SUPERHEAT = SUCTION LINE TEMP - SAT. SUCTION
TEMP.
Superheat Adjustment
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from the expansion valve, locate the adjustment screw,
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Replace adjustment cap. Wait a minimum of 10 minutes
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sures to stabilize.
Refrigerant Charge Check
using the superheat method at the compressor suction line.
To increase super heat, remove charge and to decrease
super heat, add charge. After superheat is adjusted, it is
recommended to check unit subcooling at the condenser
coil liquid line. See Design Superheat and Subcooling table
for targets on each model.
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perheat & Subcooling table.
cooling and refer to Design Superheat & Subcooling table.
1. Purge gauge lines. Connect service gauge manifold
allow pressure to stabilize.
2.
and insulate for best possible reading.
3. Check subcooling and superheat. System should
have a subcooling and superheat within the range
listed on the Design Superheat and Subcooling table.
a.
superheat, then check subcooling.
NOTE: To adjust superheat, turn the valve stem
clockwise to increase and counterclockwise to
decrease.
b. If subcooling is low and superheat is high, add
charge to raise subcooling then check superheat.
c.
valve superheat, then check subcooling.
d. If subcooling is high and superheat is low, ad-
lower the subcooling.
4. Disconnect manifold set, installation is complete.