1, if the ambient temperature is lower than 16 degrees, shift to the fifth gear; If it is lower than 10 degree, shift to the sixth or seventh gear.

2. In summer, the ambient temperature is high. At this time, the temperature in the box is difficult to drop 1 degree, and the loss of cold energy through the insulation layer and door seal of the box will also be accelerated, so that the start-up time is long and the shutdown time is short.

3. When the ambient temperature is high in summer, it should be used in weak gear 2-3.