By Dovydas Kersys · Chapter 8 of 58 in Machine Commissioning.

Before you begin: Follow the machine documentation, risk assessment, site procedures and lockout/tagout requirements. Commissioning can expose personnel to electrical energy, stored pressure and unexpected motion. Never defeat a safety function merely to make a test easier. Examples and diagrams are generic and must be checked against the actual machine.

Before applying power, inspect the panel as a built assembly. Commissioning should catch wiring mistakes, loose conductors, incorrect protection, debris, unremoved transport materials and mismatched components before they become energized faults.

Why this matters during commissioning

A pre-power inspection is cheap compared with repairing a damaged drive, power supply or PLC module after a wiring error.

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Commissioning procedure

  1. Compare installed devices with the schematic and BOM.
  2. Check conductor sizes, ferrules, terminal tightness, wire numbering and separation of voltage classes.
  3. Verify breaker/fuse ratings and adjustable settings against design.
  4. Inspect contactors, overloads, relays and plug-in modules for shipping damage or loose seating.
  5. Remove loose wire strands, cutoffs, screws and conductive debris.
  6. Confirm panel fans, filters, heaters and enclosure seals are complete.

Common failure patterns

  • 24 VDC wired into an analog input configured for a different signal type.
  • Supply and load sides reversed on a power device.
  • Loose neutral or common conductor.
  • Shield terminations contacting unintended terminals.

Evidence to record

  • Panel inspection checklist
  • Torque checks where required
  • Protection settings
  • Discrepancies and corrections
  • Photo or redline references

FIELD RULE: Do not energize a panel that has not been physically compared with its drawings.

Appendix A. Pre-Power Checklist

Use this as a generic prompt before first electrical energization.

☐ Approved schematic and panel layout available at the machine.

☐ Main supply rating matches design.

☐ Protective earth and bonding inspected/tested.

☐ Breaker/fuse ratings and adjustable settings verified.

☐ Control transformer / power supply taps verified.

☐ 24 VDC polarity and distribution checked.

☐ No loose conductors, strands, screws or conductive debris.

☐ PLC/I/O modules seated and keyed correctly.

☐ Drive/servo motor and feedback cables verified.

☐ Neutral/commons and shield terminations checked.

☐ External feeds, UPS circuits and backfeeds identified.

☐ Panel doors, covers and barriers installed as required for the planned test.

☐ People briefed; area controlled for energization.

FIELD RULE: Add site-specific requirements and measured values. A checkbox alone is weak evidence when a numeric measurement is available.

Continue the series

Adapted from Machine Commissioning for Maintenance and Automation Technicians, by Dovydas Kersys. © 2026 Dovydas Kersys. Featured cover image is an AI-generated editorial illustration.

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