9
Expansion Valve System
NOTE: Units matched with indoor coils equipped with non-adjust-
able TXV should be charged by subcooling only.
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. Temporarily install a thermometer on the liquid line at the
liquid line service valve and 4-6" from the compressor on
the suction line. Ensure the thermometer makes adequate
contact and is insulated for best possible readings. Use liq-
uid line temperature to determine sub-cooling and vapor
temperature to determine superheat.
3. Check subcooling and superheat. Systems with TXV applica-
tion should have a subcooling of 8°F +/- 1.0°F and super-
heat of 8°F +/- 1.0°F.
a. If subcooling and superheat are low, adjust TXV to
8°F +/- 1.0°F superheat, then check subcooling.
NOTE: To adjust superheat, turn the valve stem clock-
wise to increase and counter clockwise to decrease.
b. If subcooling is low and superheat is high, add charge
to raise subcooling to 8°F +/- 1.0°F then check super-
heat.
c. If subcooling and superheat are high, adjust TXV valve
to 8°F +/- 1.0°F superheat, then check subcooling.
d. If subcooling is high and superheat is low, adjust TXV
valve to 8°F +/- 1.0°F superheat and remove charge to
lower the subcooling to 8°F +/- 1.0°F
NOTE: Do NOT adjust the charge based on suction pressure
unless there is a gross undercharge.
4. Disconnect manifold set, installation is complete.
Subcooling Formula = Sat. Liquid Temp. - Liquid Line Temp.
NOTE: Check the Schrader ports for leaks and tighten valve cores
if necessary. Install caps finger-tight.
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