LIQUID LINE SOLENOID VALVE — Field-supplied liquid line solenoid valve(s) must be installed at the evaporator if coil surface area is exceeded per Table 8. Install liquid line solenoid valve just ahead of the TXVs (thermostatic expansion valves) which will be mounted at the evaporator. See Fig. 13 (for 38APD025-100 dual-circuit units), or Fig. 14 (for 38APS025-050 single-circuit units). Refer to Table 6.
THERMOSTATIC EXPANSION VALVES — All 38AP units must be installed with 5% bleed TXVs to ensure proper unit operation.
To achieve good mixing of the refrigerant leaving the evap- orator suction header for proper sensing by the TXV bulb:
1.Install a minimum of two 90-degree elbows upstream of the TXV bulb location. See Fig. 15 for dual-circuit units and Fig. 16 for single-circuit units.
2.Locate the TXV bulb on a vertical riser, where possi- ble. If a horizontal location is necessary, secure the bulb at approximately the 4 o’clock position.
If an oil return connection is located at the bottom of the evaporator suction header, tee-in this connection ahead of first mixing elbow. See Fig. 15 (for dual-circuit units) or Fig. 16 (for single-circuit units). When the compressor is below the evaporator, the riser at the evaporator should extend to the top of the evaporator section. After the riser is installed, the suction line can elbow down immediately. Refer to the evaporator product data for sizing information.
LIQUID LINE FILTER DRIER — Installation of a field- supplied filter drier and sight glasses in each refrigerant circuit is required. Select the filter drier for maximum unit capacity and minimum pressure drop. Figure 13 (for dual-circuit units) or Fig. 14 (for single-circuit units) shows required location of solenoid valves and recommended locations for the filter driers and sight glasses. Complete the refrigerant piping from the evaporator to the condenser before opening the liquid and suc- tion lines at the condenser. Refer to Table 6.
CAUTION
For all units with liquid lines of 100 ft (30.5 m) or more or any 025-030 size dual circuit unit application where evapo- rator is located higher than the condensing unit and liquid lines exceed 55 feet (16.8 m), a long line option kit must be installed to prevent compressor failure. The long line option kit must be mounted in the liquid line near the con- densing unit. See Fig. 17.
LONG LINE APPLICATIONS — A long line option kit must be installed for:
1.Any 025-030 size dual circuit unit where the evapora- tor is located higher than the condensing unit and the linear line length exceeds 55 ft (16.8 m).
2.Any size dual or single circuit unit with linear line length of 100 ft (30.5 m) or more.
The kit consists of a liquid line check valve and a bypass check valve to prevent charge migration to compressor. The long line option kit must be mounted in the liquid line near the condensing unit. The kit may be mounted in any orientation, horizontally or vertically. See Fig. 17 for orientation and Fig. 11 for location.
HOT GAS BYPASS — Hot gas bypass is not recommended. If hot gas bypass is used, it should be introduced before the evaporator.
FINAL CONNECTION AND LEAK TEST
CAUTION
The 38AP unit is shipped with a nitrogen holding charge. Use caution when relieving unit pressure to avoid possible equipment damage or personal injury.
Relieve the pressure caused by the nitrogen holding charge. Connect liquid line and suction line to field piping. Refer to Fig. 5-8 for circuit orientation.
IMPORTANT: Protect the liquid and suction service valves from the heat of brazing. Schrader valve cores must be removed from the liquid and suction service valves before brazing in field connection piping to avoid damage. Reinsert cores after brazing is completed.
The refrigerant system must not be opened and exposed to atmosphere for longer than 15 minutes. Connection and pump- down should be made as soon as possible to avoid acids forming in the compressor POE (polyolester) oils, which could damage the compressors.
Leak test the entire system by using soap bubbles and nitro- gen or R-410A and an electronic leak detector.
Purge nitrogen or recover R-410A from system after com- pletion of leak-checking procedure. Repair leak if one is found. When finished, evacuate and dehydrate system using the fol- lowing method.
EVACUATION AND DEHYDRATION — Because the 38AP systems use polyolester oil, which can absorb moisture, it is important to minimize the amount of time that the system interior is left exposed to the atmosphere. Minimizing the exposure time of the oil to the atmosphere will minimize the amount of moisture that needs to be removed during evacuation.
Once all of the piping connections are complete, leak test the unit and then pull a deep dehydration vacuum. Connect the vacuum pump to the charging valve in the suction line and to the liquid line service valve. For best results, it is recommended that a vacuum of at least 500 microns (0.5 mm Hg) be ob- tained. Afterwards, to ensure that no moisture is present in the system, perform a standing vacuum-rise test.
With the unit in deep vacuum (500 microns or less), isolate the vacuum pump from the system. Observe the rate-of-rise of the vacuum in the system. If the vacuum rises by more than 50 microns in a 30-minute time period, then continue the dehy- dration process. Maintain a vacuum on the system until the standing vacuum requirement is met. This will ensure a dry system.
By following these evacuation and dehydration procedures, the amount of moisture present in the system will be mini- mized. It is required that liquid line filter driers be installed be- tween the condenser(s) and the expansion devices to capture any foreign debris and provide additional moisture removal ca- pacity. Be sure to consider the pressure drop of the filter drier when determining piping requirements.
