When fixing distribution boxes to wooden or light steel keel wall panels, reinforcement measures should be taken. If the conduits are concealed within the wall panel and there are concealed junction boxes, the box openings should be flush with the wall surface. Fireproofing treatment should be applied to wooden wall panels, such as by applying fire-retardant paint or adding fire-retardant lining. Except for the above requirements, the fixing methods are the same as described above.
1. Faults caused by the influence of ambient temperature on low-voltage electrical appliances
Low-voltage electrical appliances in lighting low-voltage distribution boxes consist of fuses, AC contactors, residual current circuit breakers, capacitors, and meters. These low-voltage electrical appliances are designed and manufactured in accordance with GB1497 "Basic Standards for Low-Voltage Electrical Appliances," and their normal operating conditions are specified accordingly: the upper limit of ambient air temperature shall not exceed 40℃; the average ambient air temperature over 24 hours shall not exceed 35℃; and the lower limit of ambient air temperature shall not be lower than -5℃ or -25℃.
2. Faults caused by product quality issues
Because the construction period for the required distribution cabinets is short, and the lighting distribution box manufacturers have urgent needs for the supply of related low-voltage electrical appliances, the requirements for product quality are not strict enough. This has resulted in some products malfunctioning shortly after being put into operation. For example, some models of AC contactors failed to operate normally shortly after the distribution box was put into operation due to the burnt-out contactor closing coil.
3. Faults caused by improper selection of electrical appliances in the lighting distribution box.
Because the capacity of the AC contactors was not properly selected during manufacturing, AC contactors of the same capacity were installed for different outgoing circuits, and the imbalance of the three-phase load was not taken into account. As a result, the current rating of some outgoing contactors was not increased by one level from the normal selection, which led to the AC contactors burning out during the high-temperature season in summer.
