Grasso
Refri
eration Division
GRASSO SYSTEM CONTROL
01.2004/1 638660E_chapter2.doc Chap. 2 - 29
2.7.2.17 Start limitation based on too low oil temperature
The start limitation is intended to prevent the compressor from starting if too much refrigerant is dissolved in
the oil.
If the calculated oil temperature limit reaches the saturation value based on the oil pressure in the compressor
crankcase, the compressor is blocked. In this way it is ensured that the compressor cannot be started as long as
refrigerant is dissolved in the oil. The compressor can be damaged if it is started with dissolved refrigerant in the
oil therefore such a situation should always be avoided.
The signal dominates compared to the capacity control and is effective until the calculated oil temperature limit
value has exceeded the saturation value based on the oil pressure in the compressor crankcase.
The start limitation function based on low oil temperature is illustrated in the following diagram.
T
oil
Oil temperature
A.. Time characteristic of the..
1 = actual oil temperature
2 = calculated oil temperature limit
value
b.. Start limitation value as offset to
the actual oil temperature
P
oil
[°C].. Time characteristic of the calculated
saturation value based on the oil
pressure in the compressor
crankcase. This value forms the
limitation and warning limit value.
B.. Start limitation active
Figure 2.33, Start limitation based on too low oil temperature
Oil temp
Low limit -
Oil pres °C/R >
Oil temp: Actual oil temperature in °C
Low limit: Begin of the start limitation —
enter value as an offset to the actual oil temperature in K
<< Limit values 01 >> Oil pres °C/R: Actual saturation value based on the oil pressure in the
compressor crankcase in °C/R (refrigerant dependent)
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