Germetic Compact

The Bitzer hermetic compact screw compressors are especially popular for air conditioning in railways. They are dimensioned for the typical rail coach and can be controlled over a wide speed range. Their low installation height, weight and very quiet running also meet the special demands of space-restricted roof or under floor installations.

Hermetic Compact Screw Compressors VSK31 / VSK41 series

The hermetic compact screws complete the compressor screw programme in the lower capacity spectrum. They are suited for insertion into factory finished air conditioning units, liquid chiller units and in particular also for the air conditioning of railway carriages.

The space saving design with integrated oil separator and reservoir enables the simplest installation. With their small height, low weight and very smooth running over a wide speed range, they already meet today the increasing demands of confined roof and under floor installations.

The deciding features

❏ Simple and robust construction

❏ Hermetically sealed by welding

❏ Low weight

❏ Small space requirement

❏ Low noise and vibration levels

❏ Optimised design for R134a

❏ Ester oil charge

❏ Generously dimensioned roller bearings, giving high reliability and long life

❏ Integrated oil separator / oil filter

❏ Built-in check valve (VSK41)

❏ Internal pressure relief valve

❏ Suction gas cooled motor – direct drive without gears

❏ Motor protection device with

  • thermal PTC monitoring
  • manual reset
  • phase sequence monitoring

❏ High capacity and efficiency due to

  • optimized rotor profile (5:6)
  • high motor efficiency
  • precise machining

❏ Capacity control

  • stepless with variable speed (frequency converter)
  • VSK41 and VSK3162 alternative with integrated mechanical regulator (capacity regulator)

❏ Terminal box IP66 (VSK31.. with small terminal box IP65)

Design safety

Approval according to the EC Pressure Equipement Directive 97/23/EC Maximum allowable pressure 25 bar

Capacity control and start unloading

For the serie VSK41 a new form of regulating system has been developed (accessory). The basic principle corresponds to that of a control slide of industrial compressors. Thereby the displacement is reduced by moving the suction side sealing contour. The control unit is so designed that it does not reduce the stability of the compressor housing. The gaps between the rotors and the housing thus remain within tight tolerances, even with high temperatures. This measure is an important stage of development for a good overall efficiency of smaller screw compressors, due to the higher demands on precision.

As a control element there is a hydraulically activated piston for male rotor. It sits absolutely flush with the end wall / housing with full load operation. The same characteristics are therefore guaranteed in this mode as for a compressor without capacity control. With part load operation the piston moves to the rear position. It opens a generously sized port to the suction side.There with the active length of the rotor profile is shortened thus the displacement capacity is reduced accordingly. Control is made electrically via the solenoid valves situated on the vessel.

Alternative capacity control with frequency inverter upon request

More information in brochure SP-300.

Performance data based on 10 ºС suction gas superheat; 5 ºС liquid subcooling for R134a

Compressor
type		 Cond.
temp.
tc, ºC		 Refrigerating capacity Q0, W Power consumption Pe, kW
Evaporating temperature t0, ºC
15 10 5 0 -5 -10 -15
50 Hz*
VSK3161-15Y 40 Q0 37550 36250 29850 24300 19470 15170 11340
Pe 8,92 6,86 6,65 6,44 6,23 6,02 5,81
50 Q0 32200 31400 25650 20300 15450
Pe 11,24 8,71 8,49 8,28 8,07
60 Q0 26200 20700 15290
Pe 11,04 10,85 10,66
VSK4141-17Y 40 Q0 49400 47400 39300 32150 25910 15080 15080
Pe 11,38 8,78 8,50 8,23 7,96 7,69 7,43
50 Q0 42350 41400 33700 26900 20650
Pe 14,33 11,13 11,85 10,58 10,32
60 Q0 34500 27250 20100
Pe 14,11 13,87 13,64
VSK4151-20Y 40 Q0 61700 59300 49100 40200 32400 25100 18860
Pe 13,07 10,58 10,24 9,92 9,59 9,27 8,95
50 Q0 52900 51800 42100 33600 25800
Pe 17,27 13,41 13,07 12,75 12,43
60 Q0 43100 34050 25150
Pe 17,00 16,71 16,43
VSK4161-25Y 40 Q0 69400 66600 55200 45100 36360 28200 28200
Pe 15,40 11,89 11,50 11,14 10,78 10,41 10,05
50 Q0 59400 58100 47300 37750 29000
Pe 19,40 15,07 14,69 14,32 13,96
60 Q0 48400 38300 28250
Pe 19,10 18,77 18,46
60 Hz*
VSK3161-15Y 40 Pe 43750 36100 29350 2350 18310 13690
Q0 8,28 8,02 7,77 7,52 7,26 7,01
50 Pe 45300 37950 37950 24500 18640
Q0 10,77 10,51 10,25 9,99 9,74
60 Pe 38850 31650 24950 18440
Q0 13,56 13,33 13,09 12,87
VSK4141-17Y 40 Pe 57200 47400 38800 31300 24250 18200
Q0 10,60 10,26 9,93 9,61 9,28 8,97
50 Pe 59600 600500 40650 32450 24900
Q0 13,73 13,43 13,09 12,77 12,46
60 Pe 51100 41650 32900 24300
Q0 17,29 17,03 16,74 16,46
VSK4151-20Y 40 Pe 71500 59300 48500 30300 39100 22750
Q0 12,77 12,36 11,97 11,57 11,19 10,80
50 Pe 74500 62500 50800 50050 31150
Q0 16,55 16,18 15,77 15,39 15,00
60 Pe 63900 52000 41100 30350
Q0 20,85 20,85 20,20 19,83
VSK4161-25Y 40 Pe 80300 66600 54500 43900 34050 25550
Q0 14,35 13,88 13,44 13,01 12,56 12,13
50 Pe 83800 70200 57100 45600 35000
Q0 18,59 18,19 17,73 17,28 16,85
60 Pe 71700 58400 46200 34100
Q0 23,40 23,05 22,65 22,30
* Operation with frequency inverter:
VSK31: 20 … 87 Hz
VSK41: 20 … 70 Hz
Further recommendations upon request
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