Trane Performance Air Handlers Manual de instalación descargar pdf (Pagina 61)

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CAH-SVX01B-EN 61

Coil Piping and Connections

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 58 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.

• Thermal expansion valve. The expansion valve is the throttling device that meters the

refrigerant into the evaporator coil. Metering too much refrigerant floods the compressor;

metering too little elevates the compressor temperature. Choosing the correct size and type of

expansion valve is critical to ensure it will correctly meter refrigerant into the evaporator coil

throughout the entire operating envelope of the system. Correct refrigerant distribution into the

coil requires an expansion valve for each distributor.

Figure 59. Type F refrigerant coil with packed elbow

The thermal expansion valve must be selected

for proper size and capacity. The size of the

expansion valve should cover the full range of

loadings. Check that the valve will successfully

operate at the lightest load condition. For

improved modulation, choose expansion

valves with balanced port construction and

external equalization.

Cut the process tube and cap assembly from the

liquid connection as shown in Figure 59 and

install the expansion valve directly to the liquid

connections.

Cut here

for piping

Perforated plate

(packed elbow)

Panel

Venturi type

distributor

Coil

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Trane Performance Air Handlers Manual de instalación Pagina 61

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