Precautions For Operation; Prevention Of Liquid Flow-Back; Purging Of Non-Condensable Gases - mycom 2016 C Series Instruction Manual

4.2

Precautions for Operation

4.2.1

Prevention of Liquid Flow-back

Liquid flow-back is a phenomenon where refrigerant that did not completely evaporate with the gas
reaches the compressor. Liquid flow-back may cause insufficient lubrication of the compressor,
abnormal vibrations and noises, and abnormal foaming of lubricant (too much entry of oil). To prevent
liquid flow-back, properly adjust the expansion valve of each liquid cooler. For details, see
"Troubleshooting" in chapter 6 of this manual.
4.2.2

Purging of Non-Condensable Gases

 Some types of refrigerants emit bad smells or toxic gases. Make sure to ventilate
the air during work.
If there is a leak on the low-pressure side of the unit, air may enter the unit.
If non-condensable gas like air enters the unit, the condensing pressure rises and the energy
consumption increases. This leads to uneconomical operation.
Follow the procedure below to check for non-condensable gases.
When the compressor is stopped, allow the cooling water to flow to the unit's condenser for at
1.
least 15 minutes. Check the condensing pressure by using the pressure gauge of the compressor.
Check the cooling water temperature.
2.
Compare the condensing pressure checked in step 1 above with the refrigerant saturation
3.
pressure that depends on the cooling water temperature (as shown in the table below).
Table 4-1 Typical Refrigerant Temperature and Saturation Pressure
Temperature °C
0
4
8
12
16
20
24
28
32
36
40
■ Unless otherwise noted, the pressure unit MPa represents the gauge pressure in this manual.
When the pressure inside the condenser and the refrigerant saturation pressure that depends on
4.
the cooling water temperature are approximately equivalent, non-condensable gases do not exist.
When the pressure inside the condenser is 0.05 MPa or more higher than the refrigerant
saturation pressure that depends on the cooling water temperature, there is a possibility of
non-condensable gases entering the unit. In that case, purge the non-condensable gases from
the condenser.
Compound 2-stage Screw Compressor 2016**C
Ammonia R404A
0.328 0.509
0.396 0.590
0.472 0.678
0.557 0.775
0.652 0.881
0.756 0.996
0.871 1.121
0.998 1.256
1.137 1.401
1.289 1.559
1.454 1.728
4-5
2200LZJE-HO-C6-N_2013.12.
Chapter 4 Operation of Compressor and Unit
Pressure MPa
R507A R410A
0.523 0.699
0.606 0.807
0.696 0.924
0.795 1.053
0.903 1.193
1.021 1.346
1.148 1.513
1.286 1.693
1.435 1.887
1.595 2.098
1.768 2.324
4.2 Precautions for Operation
R134a
0.192
0.237
0.287
0.342
0.403
0.471
0.545
0.626
0.714
0.811
0.916