Water contamination in an industrial ammonia refrigeration system can lower system efficiency, and increase the electrical costs required to run the system’s refrigeration compressors.
For a given pressure, the addition of water to the ammonia will raise its temperature. At typical suction pressures, the addition of 10% water by weight will increase the evaporator temperature by about 4°F (2°C)
Air-purgers only remove non-condensables like air. If your air-purger has been venting air, it’s been leaving behind the water vapor indicates, this could be due to water in the ammonia.
If water comes out of your oil pot before the oil, there is water in your system.
With water in the system, the evaporator pressure must be lowered to maintain the desired temperature. For example a 0˚F coil with 5% water in the ammonia must operate at 14.3 psig instead of 15.7 psig. So your compressor must work harder, and uses more energy. The graph (at right) shows the extra energy cost to an ideal system operating with 0˚F evaporator and 95˚F condenser. For a 100 TR system operating 24/7 with 5% water in ammonia, the extra electric power is around $2000 per year (depending on local rates).