Bitzer ST-140-2 Mode D'emploi page 82

11 Thermostatic control of the oil cooler
Oil coolers must be thermostatically controlled, 2 variants are possible:
• HS. and CS. compressors are controlled according to the discharge gas temperature.
• OS. compressors are controlled according to the oil injection temperature.
Control according to discharge gas temperature (HS., CS. compressors)
The sensor is attached to the discharge gas line.
NOTICE
!
!
The control of the oil cooler should correspond to the maximum discharge gas temperature selected in the
BITZER SOFTWARE ( Selecting the oil cooler with the BITZER SOFTWARE )!
The default setting in the software is 80°C for HS./OS. compressors and 110°C for CS. compressors. How-
ever, these values can be adjusted up to max. 100°C (HS./OS.) resp. 120°C (CS.).
Type of oil cooler
air cooled oil cooler:
temperature controller of
the oil cooler fan
water cooled oil cooler:
oil mixing valve or flow
regulating valve (heat
transfer fluid)
oil heater and oil thermo-
stat integrated in the oil
separator
Tab. 7: Control of the oil cooler according to discharge gas temperature for HS. and CS. compressors
Technical data of the oils (density, viscosity, specific heat capacity) can be taken e.g. from the respective data
sheet. For BITZER oils for CS. compressors, see also Technical information ST-500 .
Control according to oil injection temperature (OS. compressors)
With OS. compressors the oil injection temperature must be limited to 50°C resp. 60°C in order not to stress the
shaft seal too much thermally. The sensor must be fitted to the oil injection line. Set the following as oil injection
temperature:
• for mineral oils (MO) of viscosity 68 cSt or poly-alpha-olefin (PAO): max. 60°C
• for polyolester oil (POE) and alkylbenzene oil (AB): max. 60°C
• for mineral oils (MO) of viscosity 32 or 46 cSt: max. 50°C
The viscosity and further technical data of the oils can be taken e.g. from the respective data sheet. For the oils
used by BITZER for R717 (NH
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Setting temperature
the max. discharge gas temperature
chosen during selection ( Selecting the
oil cooler with the
BITZER SOFTWARE )
5K less than the max. discharge gas
temperature chosen during selection
( Selecting the oil cooler with the
BITZER SOFTWARE )
70°C
) see also Technical information AT-640 .
3
Example
• selection in the BITZER SOFTWARE:
max. discharge gas temperature 80°C
• setting temperature for oil cooler: 80°C
• selection in the BITZER SOFTWARE:
max. discharge gas temperature 80°C
• setting temperature for oil cooler: 75°C
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