Enter the appropriate table to select the recommended line sizes.
Model: | Line Sizes Table | Quantity of Line Sets |
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38AUZ | 5 | 1 |
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38AUD | 6 | 2 |
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Liquid Lift —
A liquid lift condition exists when the outdoor unit is located below the indoor (evaporator) unit and liquid flows vertically up in a portion of the liquid line. The vertical column of liquid reduces the available state point subcooling at the evaporator coil’s thermal expansion valve. This effect reduces the length of liquid lift (feet of elevation) that a liquid line size can accommodate. Longer linear tube lengths will also reduce the amount of liquid lift possible.
Check Tables 5 (38AUZ) and 6 (38AUD) for maximum liquid lift capabilities for line sizes. Reselect the liquid
line tube size if necessary. If maximum available tube size cannot provide the required lift distance on this installation, relocate the outdoor unit to reduce the equivalent line length or the lift requirement.
Suction Riser —
A suction riser condition exists when the outdoor unit is located above the indoor (evaporator) unit and suction vapor must flow vertically up to return to the compressor. Oil return is a concern when the suction tube size is too large to produce the minimum refrigerant velocity to ensure oil return at minimum load conditions.
Check Table 7 for maximum suction tube size for 38AU units at minimum load conditions. Consider suction speed riser (reduced tube size for vertical segment only) or double suction riser arrangement if the recommended suction tube size does not provide necessary minimum flowrates for this riser.
38AU
Table 5 – 38AUZ 16-25 Piping Recommendations (Single-Circuit Unit)
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| Equivalent Length |
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| Linear Length |
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Model | m |
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38AUZ*16 | Liquid Line |
| 5/8 |
| 5/8 |
| 5/8 |
| 5/8 | 5/8 |
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| Max Lift |
| 25 |
| 50 |
| 75 |
| 100 | 125 |
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| Suction Line |
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| Charge (lbs) |
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| Novation |
| 24.3 |
| 27.5 |
| 30.6 |
| 33.7 | 37.8 |
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| RTPF |
| 42.7 |
| 45.9 |
| 49.0 |
| 52.1 | 56.2 |
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38AUZ*25 | Liquid Line |
| 5/8 |
| 5/8 |
| 5/8 |
| 5/8 | 5/8 |
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| Max Lift |
| 25 |
| 50 |
| 71 |
| 77 | 63 |
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| Charge (lbs) |
| 37.8 |
| 40.8 |
| 44.6 |
| 47.8 | 51.1 |
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Legend: |
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Equivalent | Equivalent tubing length, including effects of refrigeration specialties devices |
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Length |
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Linear Length | Typical linear tubing length, (50% added to linear to define Equivalent Length for this table) |
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Liquid Line | Tubing size, inches OD. |
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Max Lift | Maximum liquid lift (indoor unit ABOVE outdoor unit only), at maximum permitted liquid line pressure drop — | |||||||||||
| S | Linear Length Less than 75 ft (23 m): Minimum 2.0° F subcooling entering TXV |
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| S | Linear Length Greater than 75 ft (23m): Minimum 0.5° F subcooling entering TXV |
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Suction Line | Tube size, inches OD |
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Charge | Charge Quantity, lbs. Calculated for both liquid line sizes (where applicable), but only with larger suction line size | |||||||||||
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NOTE: | For applications with equivalent length greater than 188 ft (57 m) and/0r linear length greater than 125 ft (38 m), | |||||||||||
| contact your local Carrier representative. |
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13