Step 3 Ð Make Refrigerant Piping
Connections
The ®eld-supplied liquid line solenoid valve must be installed at the evaporator to avoid possible compressor damage during unit operation. See Fig. 11 (for 38AH044- 084 dual-circuit and 38AH094-134 units), or Fig. 12 (for 38AH044-084 optional single-circuit units).
The units have large suction lines to minimize friction losses. The units also have the ability to operate at low capacity. Because of these capabilities, use special care with suction piping and suction risers to ensure proper compressor oil return under all operating conditions. Maximum allowable vertical separation between the condensing unit and the evapo- rator is shown in Table 5. Size suction lines in accordance with Tables 6A or 6B through 9A or 9B and Fig. 13. Mount liquid line solenoid valve just ahead of the TXVs (thermo- static expansion valves) which will be mounted at the evaporator. See Fig. 11 (for 38AH044-084 dual-circuit and 38AH094-134 units) or Fig. 12 (for 38AH044-084 optional single-circuit units).
To achieve good mixing of the refrigerant leaving the evapo- rator 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. 14 (for 38AH044-084 dual-circuit and 38AH094-134 units) or Fig. 15 (for 38AH044-084 optional single-circuit units).
2.Locate the TXV bulb on a vertical riser, where possible. If a horizontal location is necessary, secure the bulb at approximately the 4 o'clock position.
3.Size the suction line from the evaporator to the common suction line to achieve high refrigerant velocity. See Tables 6A or 6B through 9A or 9B and Fig. 13.
If an oil return connection at the bottom of the suction header is supplied with an evaporator, tee-in this connection ahead of ®rst mixing elbow. See Fig. 14 (for 38AH044-084 dual-circuit and 38AH094-134 units) or Fig. 15 (for 38AH044- 084 optional single-circuit units). When the compressor is below the evaporator, the riser at the evaporator should ex- tend to the top of the evaporator section. After the riser is installed, the suction line can elbow down immediately.
Install a ®eld-supplied ®lter drier and sight glasses in each refrigerant system. Select the ®lter drier for maximum unit capacity and minimum pressure drop. Figure 11 (for 38AH044- 084 dual-circuit and 38AH094-134 units) or Fig. 12 (for
38AH044-084 optional single-circuit units) shows required location of solenoid valves and recommended locations for the ®lter driers and sight glasses. Complete the refrigerant piping from the evaporator to the condenser before opening the liquid and suction lines at the condenser.
Table 5 Ð Liquid Lift
UNIT | | | MAXIMUM LIQUID LIFT | |
| 60 Hz | 50 Hz | |
38AH | | |
| Ft | | M | Ft | | M |
044 | 69 | | 21.0 | 57.5 | | 17.5 |
054 | 75 | | 23.0 | 75.0 | | 23.0 |
064 | 75 | | 23.0 | 65.0 | | 19.8 |
074 | 45 | | 13.7 | 37.5 | | 11.4 |
084 | 75 | | 23.0 | 75.0 | | 23.0 |
094 | 55 | | 16.7 | 46.0 | | 14.0 |
104 | 50 | | 15.2 | 42.0 | | 12.8 |
124 | 75 | | 23.0 | 65.0 | | 19.8 |
134 | 45 | | 13.7 | 37.5 | | 11.4 |
UNITS 38AH044-084 Ð Relieve the pressure caused by the holding charge into a refrigerant recovery system. Uncap the suction line and cut the run-around tube at the liquid line as close to the loop elbow as possible. This will leave approximately 2 in. (50 mm) of straight tube for liquid line connection.
IMPORTANT: Protect the liquid valves from the heat of brazing.
Leak test the entire system by using soap bubbles and nitrogen or R-22 with an electronic leak detector.
Purge nitrogen or reclaim R-22 from system after com- pletion of leak-checking procedure. Repair leak if one is found. When ®nished, evacuate and dehydrate system using the methods described in Carrier GTAC II (General Training Air Conditioning II), Module 4, System Dehydration.
UNITS 38AH094-134 Ð Relieve the R-22 holding charge of each circuit into a refrigerant recovery system. Remove the liquid line to factory-installed suction line loop by cut- ting the loop at the liquid valve. (See Fig. 9A and 9B.) Cut as close to the 90-degree bend in the loop as possible. The remaining tube piece in the valve will be used for brazing the liquid line. Unbraze and remove the cap from the liquid line. For 38AH094 and 104 units, sweat-connect the liquid and suction lines from the evaporator. For 38AH124 and 134 units, see Piping Kit Connections on page 21.
