PURPOSE: To supplement a suitable amount of refrigerant by a method wherein when a liquid surface dropping time in a sight glass is shorter than a predetermined time, refrigerant is charged with an amount of refrigerant at a time when the liquid surface dropping time reaches a predetermined time being applied as a check point and further a predetermined amount of refrigerant is charged from this check point.
CONSTITUTION: Environment of cooling cycle 1 is set, a liquid surface dropping time of a sight glass is measured and then the liquid surface dropping time is compared with a predetermined time. In the case that the liquid surface dropping time is shorter than the predetermined time, a refrigerant supplementing liquid amount control valve 16 is opened to supplement refrigerant and then the liquid surface dropping time is measured. This operation is repeated, the liquid surface dropping time changes from the short time to the predetermined time and the amount of refrigerant reaches a check point, resulting in that refrigerant is supplemented further from this check point to obtain the most suitable amount of refrigerant. At this most suitable amount of refrigerant, the liquid surface dropping time is measured again and in the case that the liquid surface dropping time is equal to the predetermined time, the refrigerant charging operation is completed.
NEMOTO NORIAKI
TSUJI TERUAKI
MATSUMOTO MITSUHARU
