Blue Box SIGMA 2002 - Checks During Operation; 10.1 Checking the refrigerant charge

Blue Box - 87
10 CHECKS DURING OPERATION
- With the unit at steady conditions check that the entering and leaving condenser water temperatures are inside
the operating limits given in the technical specifications.
10.1 Checking the refrigerant charge
- After a few hours of unit operation check that the sight glass moisture indicator has a green coloured core. if the
core is yellow, moisture is present in the circuit. In such a situation the circuit must be dehydrated by a qualified
technician.
- Check the sight glass for air bubbles. A constant passage of bubbles through the sight glass could indicate that
the refrigerant must be replenished. Occasional bubbles are considered normal.
- A few minutes after the start of the compressors, check that the condensing temperature, equivalent to the
pressure read on the pressure gauge, is approximately 8 °C higher than condenser inlet water temperature.
Also check that the evaporating temperature, equivalent to the pressure read on the pressure gauge, is 5 °C
lower than the evaporator outlet temperature.
- Check that the refrigerant superheating is between 5 and 7 °C; to do this:
1) measure the temperature using a contact thermometer placed on the compressor suction pipeline;
2) read the temperature, equivalent to the pressure read on the pressure gauge connected to the compressor
suction side (saturation temperature corresponding to suction pressure); for units charged with R407C
refrigerant, refer to the D.P. (Dew Point) pressure gauge scale.
The difference between the temperatures measured in this manner is equivalent to the superheating value.
- Check that refrigerant subcooling is between 5 and 7 °C; to do this:
1) measure the temperature using a contact thermometer placed on the compressor discharge pipeline;
2) read the temperature, equivalent to the pressure read on the pressure gauge connected to the liquid
connection at the condenser outlet (saturation temperature corresponding to condenser delivery pressure);
for units charged with R407C refrigerant, refer to the B.P. (Bubble Point) pressure gauge scale.
The difference between the temperature values measured in this manner is equivalent to the subcooling
value.