Liebert Precision Cooling System DS - Manual (Page 85)

Piping
75
Leak Checking of Unit and Field Piping
Liebert unit fluid systems are factory-checked for leaks and may be shipped with a nitrogen holding
charge. Liebert unit fluid circuits should be checked for leaks at installation as described below.
8.2 Refrigeration Piping
NOTE
During leak checking of field-installed piping, Emerson recommends that the unit be isolated
using field-installed shutoff valves. When the Liebert units are included in a leak test, use of
fluid for pressure testing is recommended. When pressurized gas is used for leak testing the
Liebert unit, the maximum recommended pressure is 30 psig (2 bars) and tightness of the unit
should be verified by pressure decay over time, (<2 psig/hour [0.3 bars/hour]) or sensing a
tracer gas with suitable instrumentation. Dry seals in fluid valves and pumps may not hold a
high gas pressure.
!
WARNING
Risk of explosive discharge from high-pressure refrigerant. Can cause injury or death.
This unit contains fluids and/or gases under high pressure.
Relieve pressure before working with piping.
!
WARNING
Risk of refrigerant system rupture or explosion from over pressurization. Can cause
equipment damage, injury or death.
If a pressure relief device is not provided with the condenser unit, the system installer must
provide and install a discharge pressure relief valve rated for a maximum of 500 psig (34bar)
in the high side refrigerant circuit. Do not install a shutoff valve between the compressor and
the field installed relief valve.
One or more additional pressure relief valves are required downstream of any and all field-
installed isolation valves as shown in Figures 57 and 58. Do not isolate any refrigerant
circuits from overpressurization protection.
For systems requiring EU CE compliance (50Hz), the pressure relief valve must be CE
certified to the EU Pressure Equipment Directive by an EU “Notified Body.”
!
CAUTION
Risk of oil contamination with water. Can cause equipment damage.
Some Liebert DS Systems require the use of POE (polyolester) oil. See 12.7.1 - Compressor
Oil for requirements. 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.
NOTE
A pressure relief valve is provided with Liebert Lee-Temp condensers. A fusible plug is
provided on Liebert Fan Speed Control condensers. The Liebert indoor-cooling unit has a
factory-installed high pressure safety switch in the high side refrigerant circuit.