A slight loss of refrigerant is recognized by ‘bubbles’ in the liquid-indicating sight glass installed in the liquid line of a system, a loss of performance, partial frosting of the evaporator and lower than normal operating pressures. Refrigerant may be added in vapour form to the low side of the system if the refrigerant is azeotropic such as R502. This means that it reacts as a single substance refrigerant. The zeotropic refrigerant blends do not react in a similar manner and they should be added to a system in liquid form. .
