Reference Text on figure
(16) Extra set of fuses for CSA/UL certified compressors
(17) Customer's motor starter
(18) Separate low voltage supply or transformer
(19) For compressors with motor supply voltage > 690 V
7.7 Quality of safety components
When installing a remote emergency button or a motor contactor, the following B10d values are advised:
• Emergency stop button: 500 000
• Main contactor: 933 333
7.8 Cooling water requirements
Recommendations
The cooling water quality must meet certain minimum requirements.
No general recommendation can encompass the effects of all combinations of the various compounds,
solids and gases typically found in cooling water in interaction with different materials.
Only non-treated water must be used.
This recommendation is a general guide line for acceptable coolant quality.
Type of system
It is important to define the used cooling water system:
• an open system
• a closed system
In a closed system, the same cooling water circulates through a system without contact with air.
An open system is a pass-through system, or a circulating system with a cooling tower. In the latter case,
the composition of the water that enters the compressor must be considered, and not the composition of the
make-up water. Due to the evaporative effect in the cooling tower, much higher concentrations of ions can
be obtained in the circulating water than in the make-up water.
Ryznar Stability Index (RSI)
The Ryznar Stability Index (RSI) is a parameter for predicting whether water will tend to dissolve or
precipitate calcium carbonate. The adhesion of scaling deposits and their effect are different on different
materials, but the equilibrium of the water (scaling or corrosive) is only determined by its actual pH value
and by the saturation pH value (pH
s
).
The saturation pH value is determined by the relationship between the calcium hardness, the total
alkalinity, the total solids concentration and the temperature.
The Ryznar Stability Index is calculated as follows :
RSI = 2*pH
s
- pH
Instruction book
2920 1815 04 231
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