The length of flexible conduit in lighting engineering shall not exceed 1.2 meters, and in power engineering shall not exceed 0.8 meters
Regarding the specification requirements for the length of flexible conduits, based on authoritative sources and the latest information, the conclusions are as follows:
Length limit in lighting engineering
The maximum allowable length of flexible conduits in lighting engineering is 1.2 meters, and this regulation is based on the following:
The national standard "GB 50303" clearly requires that when rigid conduits are connected to equipment through flexible conduits, the length of flexible conduits in lighting engineering should not exceed 1.2 meters.
Many engineering materials (including the 2024 version of the first-level mechanical and electrical textbook) cite this standard and emphasize that this restriction is to ensure the mechanical safety and installation flexibility of the transition conduit.
Length limit in power engineering
Due to higher loads and strict mechanical strength requirements in power engineering, the length limit of flexible conduits is stricter and shall not exceed 0.8 meters. This regulation can be found in:
"GB 50303" provisions and interpretations;
The latest industry technical articles and construction procedures.
Specification Basis and Background
Flexible conduits are only used as transition sections between rigid conduits and equipment and cannot replace line laying.
The length limit may be derived from engineering experience, but the specific formulation logic is not detailed in public information.
Other related requirements
Connection method: Special connectors must be used to connect flexible conduits to rigid conduits or equipment.
Fixed spacing: The fixed point spacing of exposed flexible conduits should be ≤1 meter, and the distance between the pipe clamp and the edge must be less than 0.3 meters.
Prohibited use: Metal flexible conduits cannot be used as connecting conductors for protective conductors (PE/PEN).
