Effect of refrigerant charge on the performance of air conditioning systems

An air conditioning system operates in an optimal condition if the system i s fury charged with a specified amount of refrigerant. Poor field maintenan ce or refrigerant leakage causes low level of charge resulting in a lower t hermal performance and higher operating cost. An experimental investigation was conducted to study the effect of low charge level of R-22 on the perfo rmance of a 3-ton residential air conditioning system, The experimental res ults show that if a system is undercharged to 90 per cent then the effect i s small: a 3.5 per cent reduction in cooling capacity and a 2 per cent incr ease in the coefficient of performance (COP), However, the system performan ce suffers serious degradation if the level of charge drops below 80 per ce nt. An ice layer formed on the outer surface of the cooling coil impedes th e heat transfer between the warm air and cold refrigerant vapour. An econom ic analysis shows that the cost of properly charging an undercharged system which is at an 85 per cent charge level, can pay for itself in savings in a short period of 3-4 months. Copyright (C) 2001 John Wiley & Sons, Ltd.