Can the cable be placed directly on the sandwich panel ceiling?

This practice is not allowed by any norm. Theoretically, PVC is flame retardant, once the wire catches fire, then the PVC flame retardant pipe can stop the fire from continuing to expand, because PVC is not easy to burn We analyze your room hazards from two points.

1. Assuming that your room is newly renovated, then there will be two lines of defense for the fire caused by short circuit or overload, the circuit breaker and the insulating skin of the wire, unless your circuit breaker specification is wrong or unqualified and the wire is a substandard product, the fire in your home may not be able to be stopped! From this point of view, the incidence of fires in new homes is lower.

2. Assuming that your room has been more than five years, then the circuit breaker may fail, the aging wire may not reach the rated load and the insulating skin can not be flame retardant, so the probability of fire in the room at this time is greatly increased, it is recommended to replace the circuit breaker, or if you have money, then redecorate and change the line, remember to wear the pipe.