In conduit wiring system, which is expensive in cost?

Question

Examoogle · Accepted Answer

Option C: Metal conduit

Explanation & Concepts:
Metal conduit wiring is considered the most expensive among the given options due to the high material cost of rigid steel pipes, the requirement for specialized threading tools, and the intensive labor needed for installation. While PVC conduits are made from inexpensive thermoplastic polymers, metal conduits offer superior mechanical protection and electromagnetic shielding, justifying their higher cost in industrial environments.

Working Principle: The higher cost of metal conduit (such as Rigid Steel Conduit or Electrical Metallic Tubing) arises from the raw material cost of galvanized steel and the complexity of its installation. Unlike PVC, which is flexible or easily joined with chemical solvents, metal conduit requires precise threading, bending using hickeys or power benders, and grounding continuity checks to ensure safety. The enhanced structural integrity and fire resistance property ($R_{fire} \rightarrow \infty$ relative to PVC) necessitate thicker walls and higher manufacturing precision, which are reflected in the market price.

Key Formulas: $C_{total} = C_{material} + C_{labor} + C_{accessories}$ — Total project cost calculation; $P_{shielding} \propto \mu_r \cdot t$ — Electromagnetic shielding effectiveness where $\mu_r$ is relative permeability and $t$ is thickness

Key Points: Metal conduits provide excellent protection against mechanical damage and accidental punctures.; Metal conduits act as an effective earth continuity conductor if installed with proper fittings.; PVC conduit is prone to physical crushing compared to steel conduits.; The cost index follows: Surface PVC

Advantages: High mechanical strength and durability; Provides electromagnetic interference (EMI) shielding; Fire-resistant properties; Excellent for hazardous/industrial zones

Disadvantages: High initial procurement cost; Requires skilled labor for installation; Susceptible to corrosion in humid environments unless treated; Installation is labor-intensive (threading/bending)

Applications: Industrial factories and power plants; Outdoor environments where mechanical impact is likely; Areas requiring high fire safety (Exposed overhead wiring); Commercial buildings for main feeder lines

Additional Info: Metal conduits are mandatory in many commercial installations under the National Electrical Code (NEC) for fire protection.. Option B (PVC Concealed) is cheaper than Metal conduit because PVC is lighter, corrosion-proof, and requires no threading or complex grounding bonding.

Answer: C is correct — Metal conduit is significantly more expensive than PVC alternatives due to higher material costs and the complex labor requirements for cutting, threading, and installing steel pipe.

Exam Tip: Always prioritize safety and environment when selecting conduit types; while metal is expensive, its use is non-negotiable in environments with high physical stress or fire risks.

Examoogle · Answer

Option A: PVC Surface conduit

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Option B: PVC Concealed conduit

Examoogle · Answer

Option D: All the above

Feature	PVC Conduit	Metal Conduit
Material	PVC (Polyvinyl Chloride)	Galvanized Steel
Cost	Low	High

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