In a cold apparatus using a refrigerant (a so-called low pressure refrigerant) in which an operating pressure during an operation partially becomes a negative pressure in the apparatus, an uncondensable gas such as air enters the apparatus from a negative pressure portion, passes through a compressor or the like, and thereafter, stays in a condenser. If the uncondensable gas stays in the condenser, condensation performance of a refrigerant in the condenser is hindered, and performance of a cold apparatus decreases. For this reason, bleeding air from the chiller and discharging the uncondensable gas to the outside of the apparatus are performed to secure certain performance. The uncondensable gas is sucked into the air bleeding device together with the refrigerant gas by the air bleeding, and the refrigerant is cooled and condensed. Accordingly, the uncondensable gas is separated from the refrigerant and is discharged to the outside of the apparatus by an exhaust pump or the like (refer to PTLs 1 and 2).
If a liquid refrigerant condensed by the air bleeding device is collected in an air bleeding tank included in the air bleeding device and an amount of the refrigerant liquid is equal to or more than a predetermined amount, the refrigerant liquid is returned from the air bleeding device to the chiller. In the related art, in order to ascertain the amount of refrigerant liquid in the air bleeding tank, a method of detecting a liquid level in the air bleeding tank is adopted, the liquid level is detected by a float type liquid level sensor, and a method of opening an automatic on/off valve such as a solenoid valve to return the liquid refrigerant liquid to the inside of the chiller if the liquid level reaches a predetermined liquid level or a method of installing a self-supporting float valve for opening a valve if the liquid level in the air bleeding tank reaches a predetermined value to return the liquid refrigerant to the inside of the chiller is adopted.