Notes on Conduit vs. Cable Tray Systems

Introduction to Conduit and Cable Tray Systems

  • Importance of selecting the appropriate structure type for:

    • Support

    • Fastening

    • Directing

    • Protecting installed wire and cable runs

Market Trends

  • U.S. shipments of electrical conduit and fittings over $2.2 billion in 2004

  • Combined shipments of metallic and non-metallic conduits were over $1.7 billion.

  • Conduit remains first choice for most wiring installations due to:

    • Wide range of designs including:

    • Rigid Metal Conduit (RMC)

    • Electrical Metallic Tubing (EMT)

    • Intermediate Metal Conduit (IMC)

    • Rigid PVC, Flexible PVC, Flexible MC, Liquid-tight conduit

    • Zinc-coated corrosion-resistant steel

  • Demand for conduit decreased from 1999 to 2004 but expected to grow 1.6% per year through 2009

  • Cable tray market remains smaller with annual sales over $200 million

Sales and Popularity of Cable Tray

  • Cable tray sales growing, with increases of 25% in 2005 and annual growth of 14% between 1997 and 2004

  • Metal-clad (MC) cable becoming preferred choice for commercial wiring, contributing to increased cable tray use

Performance and Regional Influences

  • Conduit provides excellent protection due to being an enclosed raceway

    • Steel conduit offers significant tensile strength and corrosion protection

  • Historical preferences due to gas pipe installations adapted for electrical wiring

  • Outside U.S. and Canada, cable tray is preferred for power and datacom applications

    • Notable differences in preferences found in Europe, Asia, and South America

Key Findings from Electrical Industry Survey

  • Survey of preferences in various sectors indicated:

    • Both American and Canadian professionals find cable tray cheaper and easier to install

    • Majority believe conduit offers better protection

  • Professionals from pulp & paper industries favored cable trays, while oil refineries and chemical plants slightly preferred conduits

Cost Comparisons

  • Innovative solutions reducing installation costs for both conduit and cable trays

    • Examples include color-coded conduit and pre-lubricated interiors for wire pulling

  • Major cost reductions noted in studies:

    • Installing MC cable with cable tray vs. EMT conduit resulted in approximately 30% lower material and installation costs.

    • Cost analysis showed $38,000 using rigid steel conduit vs. $9,000 using galvanized steel ladder cable tray

Conclusions

  • Ease of installation and lower material costs make cable tray a cost-effective option

  • Factors to consider include:

    • Safety

    • Cost

    • Simplicity of installation

    • Conduit remains necessary in specific hazards or applications

Definition of Raceway

  • NEC defines a "raceway" as an enclosed channel for holding wires, cables, or bus bars.

  • Cable tray is classified as an open structural system, distinct from a raceway, requiring specialized cable tray-rated cables, thus impacting project costs.