Application guidelines
32
FRCC.PC.004.A9.22
Installation and service
Refrigerant charging
Start-up
Oil charge and oil level
To eliminate these factors, a vacuum pull-
down according to the following procedure is
recommended:
Whenever possible (if valves are present)
the compressor must be kept isolated from the
system.
After the leak detection, the system
must be pulled-down under a vacuum of 500
microns. A two stage vacuum pump shall be
used with a capacity appropriate to the system
volume. It is recommended to use connection
lines with a large diameter and to connect these
to the service valves and not to the schrader
connection to avoid too high pressure losses.
When the vacuum level of 500 micron is
reached, the system must be isolated from the
vacuum pump. Wait 30 minutes during which
the system pressure should not rise. When the
pressure rapidly increases, the system is not leak
tight.
A new leak detection must be performed and
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 step 2 and 3 should be repeated.
Connect the compressor to the system by
opening the valves. Repeat step 2 and 3.
Break the vacuum with nitrogen or the final
refrigerant.
Repeat step 2 and 3 on the total system.
At commissioning, system moisture content may
be up to 100 ppm. During operation the filter
drier must reduce this to a level < 20 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.
Never run the compressor under vacuum as it
may cause compressor motor burn-out.
Before initial start-up or after a prolonged shut
down period, energise the crankcase heater (if
fitted) 12 hours prior to start-up, or turn on power
for single phase compressors with trickle circuit.
Zeotropic and "near-azeotropic" refrigerant
mixtures such as R407C and R404A must always
be charged in the liquid phase. For the initial
charge, the compressor must not run and service
valves must be closed. Charge refrigerant as
close as possible to the nominal system charge
before starting the compressor. Then slowly
add refrigerant in the liquid phase, on the low
pressure side as far away as possible from the
running compressor.
The refrigerant charge quantity must be suitable
for both winter and summer operation. Refer
also to section "Protection against flooded starts
and liquid floodback" for information about
refrigerant charge limits.
WARNING:
when a liquid line solenoid valve is
used, the vacuum in the low pressure side must
be broken before applying power to the system.
The oil charge must be checked before
commissioning (1/4 to 3/4 of the oil sight glass).
Check the oil level again after a minimum of 2
hours operation at nominal conditions. In most
installations the initial compressor oil charge
will be sufficient. In installations with line runs
exceeding 66 ft or with many oil traps or an
oil separator, additional oil may be required.
Normally the quantity of oil added should be
no more than 2% of the total refrigerant charge
(this percentage does not take into account oil
contained in accessories such as oil separators
or oil traps). If this amount has already been
added and the oil level in the compressor keeps
decreasing, the oil return in the installation is
insufficient. Refer also to section "Piping design".
In installations where slow oil return is likely such
as in multiple evaporator or multiple condenser
installations, an oil separator is recommended.
Refer to the table section “Refrigerants and
lubricants” to select the correct oil.