It refers to the level of the lubricant in the oil storage container. The oil storage container of the chiller is provided with an oil level display device. Generally, the oil level in the oil storage container should be 5 mm below the central horizontal line of the mirror. The purpose of specifying the height of the oil level is to ensure that the amount of oil required to form an oil circuit is sufficient when the pump is in operation. If the oil level is too low, it may cause the pump to be insufficient, causing malfunction or damage to the equipment.