Bitzer KT-600-4 Manual Del Usuario página 40

Check valves
Check valves in the line sections to the header are required under the following conditions ( see figure 8, page 39 ):
• If using an individual oil separator for each compressor – for protection against back condensation of refrigerant
in the separator with the compressor shut-off. Arranged in each case downstream of the oil separator.
• If the cylinder heads of the compressors can cool down below the condensing temperature at standstill ( see
page 35 ).
• Check valve for a common oil separator (installation position towards the condenser):
– If there is a danger of back condensation from the condenser or liquid receiver and
– Systems with long shut-off periods
Check valves must be suitable for use in discharge gas lines – planning and dimensioning in accordance with man-
ufacturer's specifications. As an alternative to installing a check valve, heating the oil separator during standstill is
possible.
The design of check valves for R744 systems with FI operation is very challenging and not recommended, if neces-
sary consult BITZER.
Oil separator and oil return
At a sufficient flow velocity, oil separators are not absolutely required for parallel compounding. However, they are
generally recommended for systems with large variations in load and for low temperature applications in which the
oil circulation in the system can widely vary. Depending on requirements, individual separators (per compressor) or
a common separator can be used.
For the design of the separators, the entire capacity range, including operating times at higher evaporation temper-
atures (pull down conditions) among other things, must be taken into account. Particular care during design is re-
quired for systems equipped with a common separator.
• Oil return from central oil separator: directly into the suction gas line coming from the system – at least 300 mm
upstream of the header or "Y-joint".
• Oil return from individual separators: directly into the oil return connection at the crankcase or into the suction
gas line of the compressor in question
KT-600-4 // PDF Download 40