South Tyneside College Welding Workshop

LC Electrical Services attendance was initially requested following reports from the college maintenance team of persistent nuisance tripping affecting multiple final circuits within the welding workshop area. The reported issues were impacting operational machinery and causing intermittent loss of supply during normal workshop use.

Comprehensive fault-finding procedures were undertaken across the affected installations. Investigation identified several contributing factors, including incompatibility between installed welding and fabrication machinery and the protective devices serving the existing circuits. High inrush currents and fluctuating load characteristics associated with welding equipment were found to be adversely affecting circuit protective devices, resulting in repeated unwanted tripping.

Further assessment of the installation identified a maximum demand concern across the existing three-phase distribution arrangement. Load measurements and circuit assessment confirmed that the original three-phase distribution boards were operating close to, and in some cases exceeding, their designed load capacity. This resulted in excessive thermal stress on distribution equipment and cabling infrastructure.

Following consultation with site management, a remedial solution was implemented involving the installation of a new 160A three-phase submain supply feeding a new Schneider Electric three-phase distribution board. The new distribution board was installed to current BS 7671 requirements and incorporated appropriately rated protective devices coordinated with the connected loads. This formed part of our wider industrial electrical service.

Selected circuits were isolated, identified, and migrated from one of the existing overloaded distribution boards into the newly installed board. This redistribution of circuits allowed electrical demand to be effectively balanced across two independent supplies, reducing load diversity issues and improving overall discrimination and operational reliability of protective devices.

During containment inspection works, sections of thermally damaged and burnt cabling were discovered within the existing metal trunking system. Detailed investigation traced the cause to a faulty welding unit which had introduced sustained overload conditions leading to conductor insulation breakdown. The affected cabling was safely isolated, removed, and replaced with correctly rated conductors installed within the existing containment system.

Upon completion of installation and remedial works, all three three-phase distribution boards serving the welding workshop were subjected to full inspection and electrical testing and maintenance in accordance with BS 7671. Testing included:

• Continuity of protective conductors
• Insulation resistance testing between conductors and earth
• Verification of polarity
• Earth fault loop impedance (Zs) measurements at final circuits
• Verification of protective device disconnection times
• Functional testing of protective devices and switching equipment

Test results confirmed satisfactory insulation resistance values, compliant Zs readings, and correct operation of protective measures, verifying that no further wiring faults or deterioration were present within the installation. A formal EICR report was issued on completion.

The completed works have significantly improved load distribution, reduced risk of overload, and enhanced the safety, reliability, and compliance of the electrical installation within the welding workshop. For similar works across South Tyneside, please contact our team.