Trane AM4A0A18S11SA Series, Installation, Operation And Maintenance Manual

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86 CLCH-SVX07C-EN
Coil Piping and Connections
Liquid Lines
Line Sizing
Properly sizing the liquid line is critical to a successful split-system application. The selected tube
diameter must provide at least 5°F [2.7°C] of subcooling at the expansion valve throughout the
operating envelope. Increasing the size of the liquid line will not increase the available subcooling.
Routing. Install the liquid line with a slight slope in the direction of flow so that it can be routed with
the suction line. Minimize tube bends and reducers because these items tend to increase pressure
drop and to reduce subcooling at the expansion valve. Liquid line receivers, other than those that
are factory-installed, are not recommended.
Insulation
The liquid line is generally warmer than the surrounding air, so it does not require insulation. In
fact, heat loss from the liquid line improves system capacity because it provides additional
subcooling.
Components
Liquid-line refrigerant components necessary for a successful job include a filter drier, access port,
solenoid valve, moisture-indicating sight glass, expansion valve(s), and ball shutoff valves.
Figure 76 illustrates the proper sequence for positioning them in the liquid line. Position the
components as close to the evaporator as possible.
• Filter drier. There is no substitute for cleanliness during system installation. The filter drier
prevents residual contaminants, introduced during installation, from entering the expansion
valve and solenoid valve.
• Access port. The access port allows the unit to be charged with liquid refrigerant and is used
to determine subcooling. This port is usually a Schraeder
®
valve with a core.
• Solenoid valve. In split systems, solenoid valves isolate the refrigerant from the evaporator
during off cycles; under certain conditions, they may also trim the amount of active evaporator
as compressors unload. Generally, the “trim” solenoid valve is unnecessary for variable-air-
volume comfort-cooling applications, and is only required for constant-volume applications
when dehumidification is a concern.
• Moisture-indicating sight glass. Be sure to install one moisture-indicating sight glass in the
main liquid line. The only value of the sight glass is its moisture indication ability. Use actual
measurements of temperature and pressure—not the sight glass—to determine subcooling
and whether the system is properly charged. The moisture indicator/sight glass must be sized
to match the size of the liquid line at the thermal expansion valve.