Trane TTA240F Series, Инструкция по применению, Страница: 12 / 28

6 SS-APG008-EN
Line Sizing, Routing, and Component Selection
Solenoid Valve
In TTA split systems, solenoid valves may be used to isolate the refrigerant from the evaporator
during the off cycles. This is only done when the indoor unit is well below the outdoor unit. The
solenoid valve on the TTA unit is a drop solenoid—open when the compressor is on, and off when
the compressor is off. If used, the solenoid requires code compliant wiring to the TTA condensing
unit. (The solenoid is not shown on the unit wiring diagram.)
Note: Solenoids should not be used in the TWA heat pumps due to the reverse flow of the liquid.
Note: Solenoids are seldom used and not included in Table 2, p. 20 .
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WARNING
Risk of Explosion with Refrigerant Line!
Liquid refrigerant trapped between two valves can become highly pressurized if the ambient
temperature increases. DO NOT add a liquid line solenoid valve in a cooling-only system that is
already equipped with a check valve. Failure to follow this recommendation could result in a
refrigerant line exploding under pressure which could result in death or serious injury.
Moisture-Indicating Sightglass
Be sure to install one moisture-indicating sight glass in the main liquid line.
Note: The sole value of the glass is its moisture-indicating ability. Use the Installation manual
charging curves—not the sightglass—to determine proper charge levels.
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 that 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.
For improved modulation, choose expansion valves with balanced port construction and external
equalization.
Table 4, p. 21 , identifies the part number of the valve recommended for TTA/TWA
systems. The tonnage of the valve should represent the tonnage of the portion of coil that the TXV/
distributor will feed.
Some expansion valve models have built-in check valves for heat pump operation and do not
require additional external check valves for reverse flow operation. These valves are identified in
Table 4, p. 21 .
The expansion valve and heat pump check valve are inclusive when the indoor unit is a TWE.
Check Valves
Due to the reverse cycle of the TWA heat pump, a check valve is required to bypass refrigerant
around the TXV while the unit is in heating mode. If the air handler is a TWE, it includes both the
TXV and check valve.