• Refer to the indoor unit’s user manual for appropriate piping sizes.
• Install traps on the hot gas (discharge) lines at the bottom of any rise over 5 feet high. If the rise
exceeds 25 feet (7.5m), then install a trap in 20 foot (6m) increments or evenly divided.
• Pitch horizontal hot gas piping down at a minimum rate of 1/2” per 10 ft. (42mm per 10m) so
that gravity will aid in moving oil in the direction of refrigerant/oil flow.
• Consult factory if Liebert Lee-Temp™ condenser is below the evaporator or if a condenser not
equipped with Liebert Lee-Temp is more than 15 ft (4.6m) below the evaporator.
• Consult factory if piping run exceeds 150 feet (46m) equivalent length on traditional R-407C
DX units.
• Consult factory if piping run exceeds 300 feet (91m) equivalent length on traditional R-410A
DX units.
• Consult factory if piping run exceeds 300 feet (91m) actual length or 450 feet (137m)
equivalent length on units installed with Liebert EconoPhase units.
• Keep piping clean and dry, especially on units with POE oil (R-407C, R-410A or R-22
refrigerant).
• Avoid piping runs through noise-sensitive areas.
• Do not run piping directly in front of indoor unit discharge air stream.
• Refrigerant oil – do not mix oil types or viscosities. Consult indoor unit for refrigerant type and
oil requirements.
NOTE: Failure to use compressor oils recommended by compressor manufacturer will void compressor
warranty. Consult Vertiv™ or the compressor manufacturer for further recommendations or if you have
questions about compressor oils.
Refer to ASHRAE Refrigeration Handbook for general good practices for refrigeration piping. The
Liebert indoor cooling unit has a factory-installed high-pressure safety switch in the high side
refrigerant circuit. A pressure relief valve is provided with Liebert Lee-Temp™ receivers. A fusible plug is
factory installed in the Liebert DSE™ receivers. Consult local building codes to determine if condensers
without receivers will require field-provided pressure relief devices. A fusible plug kit is available for
field installation.
Vertiv | Liebert® MC™ Installer/User Guide | 54
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