Application guidelines
24
FRCC.PC.002.A5.22
Installation and service
Start-up
Vacuum pump-down and
dehydration procedure
Leak detection
Before initial start-up or after a prolonged shut-
down period, energise the crankcase heater 12
hours prior to start-up. If the crankcase heater
cannot be energised long enough before start-
up, the compressor shall be heated in another
way (for example with an electric heater or flood
light) to boil off refrigerant from the oil. This is
particulary important when ambient temperature
is low at commissioning.
Moisture obstructs proper operation of the
compressor and the rest of the refrigeration
system. Air and moisture reduce service life,
increase condensing pressure and cause
excessively high discharge temperatures,
which are capable of destroying the lubricating
properties of the oil. Air and moisture also
increase the risk of acid formation, thus giving
rise to copper plating. All these phenomena
can ultimately induce mechanical and electrical
compressor failure. To eliminate these risks, it is
recommended to perform the following vacuum
pull-down procedure:
1. To the extent possible (i.e. if valves are present),
the compressor must be kept isolated from the
system.
2. After leak detection, the system must be
pulled-down under a vacuum of 500 microns
(0.67 mbar). A two-stage vacuum pump shall be
used with a capacity appropriate for the system
volume. It is recommended to use connection
lines with a large diameter and to connect these
lines to the service valves and not to the schrader
connection, so as to avoid excessive pressure
losses.
3. Once the vacuum level of 500 microns is
reached, the system must be isolated from the
vacuum pump. Wait 30 minutes during which
time the system pressure should not rise. When
the pressure rapidly increases, the system is
not leak tight. Bring the system pressure up
to atmospheric pressure with dry nitrogen or
another suitable inert gas in order to reform
a new leak detection. After repairing all leaks
the vacuum pull-down procedure should be
restarted from Step 1. When the pressure slowly
increases, this indicates the presence of moisture.
In this case Steps 2 and 3 should be repeated.
4. Connect the compressor to the system by
means of opening the valves. Repeat Steps 2 & 3.
5. Break the vacuum with either nitrogen or the
ultimate refrigerant.
6. Repeat Steps 2 and 3 on the total system.
Upon commissioning, the system moisture
content may be as high as 100 ppm. During
compressor operation, the filter drier must
reduce this content to a level of 20 to 50 ppm.
Warning
: do not use a megohmmeter or apply
power to the compressor while it is under
vacuum as this may cause motor winding
damage, and never run the compressor under
vacuum as this may cause the compressor motor
to burnout.
Whenever possible the compressor must be kept
isolated from the system during leak detection by
closing the suction and discharge valves. Use a
mixture of nitrogen and the final refrigerant (eg.
R404A or R507) and use a leak detector for the
applied refrigerant. A spectrometric detection
system using helium can also be applied. Note
that leak detection with refrigerant may not be
allowed in some countries. Do not use other
gasses such as oxygen, dry air or acetylene as
these gasses can form an inflammable mixture
with the compressor oil. Never use CFC or HCFC
refrigerants for leak detection of HFC systems.
Leak detecting additives shall not be used as they
may affect the lubricant properties. Warranty may
be voided if leak detection additives have been
used.
Eventual leaks shall be repaired respecting the
instructions written above.