Vertiv Liebert DSE - 5.2 Refrigerant Piping and Charging

5.2 Refrigerant Piping and Charging
WARNING! Risk of over-pressurization of the refrigeration system. Can cause explosive
discharge of high-pressure refrigerant, loss of refrigerant, environmental pollution, equipment
damage, injury, or death. This unit contains fluids and gases under high pressure. Use extreme
caution when charging the refrigerant system. Do not pressurize the system higher than the
design pressure marked on the unit's nameplate. For systems requiring EU CE compliance
(50Hz), the system installer must provide and install a pressure relief valve in the high side
refrigerant circuit that is rated same as the refrigerant high side “Max Allowable Pressure”
rating that is marked on the unit serial tag. Do not install a shutoff valve between the
compressor and the field installed relief valve. The pressure relief valve must be CE-certified to
the EU Pressure Equipment Directive by an EU “Notified Body.”
CAUTION: Risk of excessive refrigerant line pressure. Can cause tubing and component
rupture resulting in equipment damage and personal injury. Do not close off the refrigerant-line
isolation valve for repairs unless a pressure-relief valve is field- installed in the line between the
isolation valve and the check valve. The pressure-relief valve must be rated 5% to 10% higher
than the system-design pressure. An increase in ambient temperature can cause the pressure
of the isolated refrigerant to rise and exceed the system-design pressure rating (marked on the
unit nameplate).
Consult local building and plumbing codes for installation requirements of additional pressure-relief
devices when isolation valves are field installed. Do not isolate any refrigerant circuits from over-
pressurization protection.
NOTICE
Risk of oil contamination with water. Can cause equipment damage.
Liebert®DSE 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 scroll and 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 52psig(358kPa). Operation for extended periods at less than 52psig(358kPa) can
cause premature compressor failure.
5.2.1 Refrigerant Piping Guidelines forAir-cooledSystems
• Air-cooled units ship with a nitrogen holding charge. Do not vent the evaporator until all
refrigerant piping is in place, ready for connection to the unit and condenser.
• 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.
5 Piping and Refrigerant Requirements 35