2.3 Atmosphere condition: Relative humidity of the atmosphere couldn’t exceed 50% when the highest temperature is +40℃; much higher relative humidity is allowable under the condition of lower temperature, for example, when the temperature reaches +20℃, the relative humidity is up to 90%. As for dews, which contingently appear due to change of temperature,special steps should be taken. 2.4 Pollution degree: 3 2.5 Overvoltage category: Ⅱ 2.6 Tightening torque is 0.8~1.2N·m for the cable terminals. Cross section of the cable connection is 0.5~2.5mm2, and 8mm conductor length is needed.