GSX Installation Manual 2019

9
Expansion Valve System
NOTE: Units matched with indoor coils equipped with a
TXV should be charged by Subcooling only.
SUBCOOLING FORMULA = SATURATED LIQUID LINE
TEMPERATURE – LIQUID LINE TEMPERATURE
1. Purge gauge lines. Connect service gauge manifold to
base-valve service ports. Run system at least 10 minutes
to allow pressure to stabilize.
2. Clamp a pipe clamp thermometer on the liquid line near
the liquid line service valve and 4-6" from the compressor
on the suction line.
a. Ensure the thermometer makes adequate contact to
obtain the best possible readings.
b. The temperature read with the thermometer should be
lower than the saturated condensing temperature.
3. The difference between the measured saturated condensing
temperature and the liquid line temperature is the liquid
Subcooling value.
4. TXV-based systems should have a Subcooling value of
8°F +/- 1°F.
5. Add refrigerant to increase Subcooling and remove
refrigerant to decrease Subcooling.
NOTE: Units matched with indoor coils equipped with
a TXV should be charged by Subcooling only.
Superheat can also be utilized to best verify charge
levels with an adjustable TXV and make adjustments
when needed in unique applications due to
refrigerant line length, differences in height between
the indoor and outdoor unit and refrigerant tubing
sizes. These adjustments should only be performed
by qualified service personnel.
Advanced Adjustment Recommendations
NOTE: Units matched with indoor coils equipped with a
TXV should be charged by Subcooling only.
SUPERHEAT FORMULA = SUCTION LINE TEMPERATURE
- SATURATED SUCTION TEMPERATURE
1. Clamp a pipe clamp thermometer near the suction line
service valve at the outdoor unit.
a. Ensure the thermometer makes adequate contact for the
best possible readings.
b. The temperature read with the thermometer should be
higher than the saturated suction temperature.
2. The difference between the measured saturated suction
temperature and the suction line temperature is the
Superheat value.
3. TXV-based systems should have a Superheat value of
8°F +/- 1°F.
4. Adjust Superheat by turning the TXV valve stem clockwise
to increase and counterclockwise to decrease.
a. If Subcooling and Superheat are low, adjust the TXV to
8°F +/- 1°F, and then check Subcooling.
b. If Subcooling is low and Superheat is high, add charge to
raise Subcooling to 8°F +/- 1°F then check Superheat.
c. If Subcooling and Superheat are high, adjust the TXV valve
to 8°F +/- 1°F Superheat, then check the Subcooling value.
d. If Subcooling is high and Superheat is low, adjust the
TXV valve to 8°F +/- 1°F Superheat and remove charge
to lower the Subcooling to 8°F +/- 1°
F.
NOTE: DO NOT adjust the charge based exclusively on
suction pressure unless for general charging in the case
of a gross undercharge.
NOTE: Check the Schrader ports for leaks and tighten valve
cores if necessary. Install caps finger-tight.