Here at MET Labs, we’ve been product safety testing electrical/electronic equipment in the field for over 55 years. Naturally, we see the same failures over and over again. We hope this list of Top 20 Field Failures for Panel & Motor-Operated Equipment will help inspectors identify and contractors fix the most commonly observed non-compliances.
1. Supplementary Protector Usage – Supplementary Protectors are used incorrectly as branch circuit protection. When used incorrectly, these components are known to fail – welding closed and causing fires/short circuits. These can either be replaced by UL 489 listed circuit breakers or branch circuit fuses (suitable for the circuit rating).
2. Risk of Electrical Shock – Covers over live electrical parts are not secured properly. A tool or key is required to access areas that pose a risk of electrical shock.
3. Dedicated Ground – The main incoming grounding conductor is not terminated at its own dedicated point (e.g. there were two wires in the grounding terminal). The secondary ground must be moved to another grounding terminal.
4. Motor Overload Protection – Overload charts are not provided in the panel to verify the rating of the overload protection.
5. Protection of Power Supplies – The manufacturer’s instructions for overcurrent protection are not followed.
6. Strain Relief – An internal terminal strain relief device is not provided.
7. Working Space – Control panels are located too close to the wall and are not able to be serviced properly. The panel doors must be able to open at least 90 degrees.
8. Emergency Stop – Emergency stops are not provided at control and operator stations where shutdown would be required. These E-stops are required to override all other functions and operations in all modes (unless it creates another hazard).
9. Protection of Motor Drives – Motor drives are improperly protected per the manufacturer’s installation instructions. These frequency drives require specific size and type primary fuses or listed circuit breakers depending upon the size of the drive.
10. Power Transformer Protection – Power Transformers are not properly protected on the primary or secondary, based on the appropriate tables in the related standards.
11. Control Transformer Protection – Control Transformers are not properly protected. In some cases, only primary protection was found when secondary protection was also needed.
12. Termination of Wiring – Some wires are not terminated or were improperly terminated. Improper multiple terminations is a common issue and could create overheating at the terminal.
13. Conductor Ampacities Based on Termination Ratings – Conductor sizing is done improperly. Conductors are sized based on conductor ampacity without consideration to termination ratings.
14. Wire Bending Space for Main Connections – Control panels don’t have adequate wire bending space for the main connections, risking snapping the termination completely off.
15. Component Information – Components are not marked as certified (MET, CSA, UL, FM, ETL, VDE, JIS, etc.). Some components have CE marking, which is not acceptable.
16. Flexible Cords – Flexible cords are used improperly per NEC Article 400, which restricts the use of flexible cords for specific applications.
17. Multiple Power Sources – Panels that are fed with more than one source of power are not marked with a cautionary marking to protect the individual servicing the panel. This marking is required: “Caution, more than one disconnect, disconnect all before servicing.”
18. Area Classification – The environment where the product is installed is inappropriate. For example, a product intended for Ordinary Locations cannot be installed in a Class 1 Division 2 location.
19. Panel Only Certification – A control panel is certified but the load served by the panel is not.
20. Equipment Markings – Marking labels are not suitable for the surface material and temperature applied or text is not of adequate size and of good contrast.
What electrical equipment field failures do you see most often? Please leave a comment.