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NOTICE
Risk of oil contamination with water. Can cause equipment damage.
Liebert® PFD systems require the use of POE (polyolester) oil. POE oil absorbs water at a much
faster rate when exposed to air than previously used oils. Because water is the enemy of a
reliable refrigeration system, extreme care must be used when opening systems during
installation or service. If water is absorbed into the POE oil, it will not be easily removed and will
not be removed through the normal evacuation process. If the oil is too wet, it may require an oil
change. POE oils also have a property that makes them act as a solvent in a refrigeration
system. Maintaining system cleanliness is extremely important because the oil will tend to
bring any foreign matter back to the compressor.
NOTICE
Risk of improper refrigerant charging. Can cause equipment damage.
Refrigerant charge must be weighed into air-cooled compressorized systems before they are
started. Starting digital scroll compressors without proper refrigerant charging can cause the
compressors to operate at less than 5°F (–15°C) evaporator temperature and at less than
55 psig (379 kPa). Operation for extended periods at less than 55 psig (379 kPa) can cause
premature compressor failure.
4.1.1 Refrigerant Piping Guidelines for Air-cooled Systems
•
Evaporators and condensing units ship with an inert-gas holding charge. Do not vent the
evaporator and condensing unit until all refrigerant piping is in place, ready for connection to
the unit and condensing unit.
•
Use copper piping with a brazing alloy with a minimum temperature of 1350°F (732°C), such as
Sil-Fos. Avoid soft solders, such as 50/50 or 95/5.
•
Use a flow of dry nitrogen through the piping during brazing to prevent formation of copper
oxide scale inside the piping. When copper is heated in the presence of air, copper oxide forms.
POE oils will dissolve these oxides from inside the copper pipes and deposit them throughout
the system, clogging filter driers and affecting other system components.
•
A pure dry nitrogen flow of 1-3 ft
displace the air. Control the flow using a suitable measuring device.
•
Ensure that the tubing surfaces to be brazed are clean and that all burrs have been removed
from the ends of the tubes.
•
Ensure that all loose material has been cleaned from inside the tubing before brazing.
•
Protect all refrigerant line components within 18 in. (460 mm) of the brazing site by wrapping
them with a wet cloth or with a suitable heat-sink compound.
•
Isolate piping from building using vibration-isolating supports.
•
When sealing openings in walls and to reduce vibration transmission, use a soft, flexible
material to pack around the tubes to prevent tube damage.
•
When installing remote condensing units above the evaporator, the suction gas lines should be
trapped at the evaporator. These traps will retain refrigerant oil in the off cycle. When the unit
starts, oil in the traps is carried up the vertical risers and returns to the compressors. For rises
over 25 ft (7.6 m), trap every 20 ft (6 m) or evenly-divided.
•
Consult factory if piping run exceeds 150 ft (46 m) equivalent length.
•
Keep piping clean and dry, especially on units with R-410A refrigerant.
•
Avoid piping runs through noise-sensitive areas.
•
Do not run piping directly in front of discharge air stream.
•
Refrigerant oil – do not mix oil types.
Refer to ASHRAE Refrigeration Handbook for general, good-practice refrigeration piping.
12
3
/min (0.5-1.5 l/s) inside the pipe during brazing is sufficient to
Vertiv | Liebert® PFD™ Installer/User Guide
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