Preparation before installation:
Planning and selection: Choose the correct grade (Sch 40 or 80) based on the application environment (indoor, outdoor, buried, corrosive environment).
Check materials: Confirm that all conduits and fittings have clear UL/CSA certification markings.
Tool preparation: PVC pipe cutter or fine toothed saw, deburring bayonet or file, PVC special adhesive and cleaning agent, bend spring (for small diameter bends), level ruler, tape measure.
Core installation steps and key points:
Cutting and processing:
Use specialized tools to cut and ensure that the incision is level.
Thoroughly removing burrs from both the inside and outside is a crucial step in preventing damage to the cable insulation layer during threading.
Bending (if required):
Small size conduits (usually 1 inch or less) can be cold bent using bend springs at room temperature.
Do not use open flames or other heat sources to directly heat and bend, as this can damage material properties and pose a fire hazard. Prefabricated elbows should be used for large pipe diameters.
Connection (bonding):
This is the key process of PVC conduit system. Use cleaning agents and adhesives specifically designed for PVC electrical conduits.
Process: Clean (wipe the outer wall of the catheter and the inner wall of the accessory) ->Apply glue (evenly apply on the outer wall of the catheter and the inner wall of the accessory) ->Insert and rotate 1/4 turn ->Hold in place for a few seconds. The curing speed of glue is fast, and the operation needs to be fast and accurate.
Support and fixation:
The conduit must be securely fixed using approved pipe clamps, brackets, or hangers.
The support spacing is determined by the size of the conduit and the installation method (horizontal/vertical), as specified in NEC Table 352.30 (for example, the maximum horizontal support spacing for 1/2-inch conduits is approximately 1.2 meters).
Expansion and contraction treatment:
The thermal expansion coefficient of PVC is relatively high. When laying in a long straight line, expansion joints must be installed to absorb length changes and prevent conduit bending deformation or joint detachment.
Special precautions for underground direct burial:
Schedule 40 or 80 type conduits must be used.
The bottom of the ditch should be flat and free of sharp stones, and the backfill soil should be sieved.
All connections must use waterproof adhesive and may require the use of sealing gaskets at junction boxes and other locations to prevent moisture from entering.
Grounding (Bonding):
PVC conduit itself is non-conductive, therefore it cannot be used as a grounding path.
A continuous equipment grounding conductor (EGC) must be separately laid in the system, and all metal equipment (such as metal junction boxes and lamp housings) must be connected to this conductor through green grounding screws to ensure grounding continuity.