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What size ammeter should be used for stainless steel cable trays

ODN and passive infrastructure knowledge brief Published 21 Jan 2024

Prepared for preliminary research by the GESTIONVAL ODN knowledge desk. Confirm network topology, split ratio, box or cabinet capacity, joint closure rating and loss budget against current standards and product documentation.

The size of the ammeter for stainless steel cable trays should match or slightly exceed the maximum current rating of the cables installed in the tray.Determining Ammeter Size

The appropriate ammeter rating is not determined by the tray material itself but by the current-carrying capacity of the cables housed in the tray. Stainless steel cable trays, such as those made from AISI 316L, are used for mechanical support and corrosion resistance, while the electrical load is carried by the cables . To select an ammeter:

  1. Identify the maximum current expected in the cable run. This is based on the cable size, insulation type, and installation conditions.
  2. Choose an ammeter with a range slightly higher than the maximum current to prevent overloading the meter. For example, if the cable carries 50 A, a 75 A or 100 A ammeter is appropriate.
  3. Consider the type of ammeter:
    • Clamp-on (current transformer) ammeters are ideal for measuring current without disconnecting cables.
    • Panel-mounted ammeters require proper sizing to match the full-load current of the circuit.
Standards and Safety Considerations
  • Follow NFPA 70 (NEC) Article 392 for metallic cable tray installations, which includes stainless steel trays .
  • Ensure the ammeter and associated wiring comply with UL listing and NEMA VE 1 standards for metal cable trays .
  • For circuits with multiple cables in a tray, consider derating factors due to heat buildup, which may affect the maximum current and thus the ammeter rating.
Practical Example

If a stainless steel ladder tray contains three 10 AWG copper conductors rated for 30 A each, the total load may reach 90 A. In this case, an ammeter rated for 100 A would provide safe measurement while accommodating potential load fluctuations.

Summary
  • Ammeter size is based on cable current, not tray material.
  • Select a meter slightly above the maximum expected current.
  • Use UL-listed or NEMA-compliant meters for safety and code compliance.
  • Consider derating for multiple cables in the tray to avoid overheating and inaccurate readings. By following these guidelines, you ensure accurate current measurement and maintain electrical safety in stainless steel cable tray installations .

What size ammeter should be used for stainless steel cable trays - GESTIONVAL ODN INFRASTRUCTURE S.L. [PDF]

What size ammeter should be used for stainless steel cable trays

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Technical note

This reference is intended for preliminary ODN and passive infrastructure research. Topology, split ratio, box or cabinet capacity, closure rating, cable type, test limits and applicable standards must be verified for the specific project.

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