Emergency Main Switch Replacement — Cooler Installation, Weybridge

The Situation

The customer in Weybridge had a large cooler unit — the kind used to keep a room or storage space at a controlled low temperature — fed by a dedicated high-current circuit with a 100A Hager SB299U main isolator switch. The switch had been in service for a number of years and had started showing warning signs: intermittent tripping, a faint burning smell near the board, and on inspection, visible blackening around one of the terminal entry points.

This kind of fault — where arcing occurs inside the switch housing at the terminal connection — is a recognised fire risk. The heat generated by a poor or corroded connection causes the surrounding plastic to char and can, if left unattended, ignite surrounding materials. The customer was right to treat it as an emergency.

Brad Neil Electrical was called out the same day. On arrival, the extent of the damage was immediately clear: the terminal housing on the faulty switch had a burn hole where arcing had occurred, and the internal contacts showed signs of significant heat damage. The switch needed replacing before the circuit could be safely re-energised.

The faulty Hager SB299U 100A main switch removed from the cooler circuit. The burn hole at the terminal entry point is clearly visible — caused by sustained arcing at a degraded connection.

The Work Carried Out

The circuit was isolated safely and the faulty Hager SB299U 100A double-pole isolator was removed. Before fitting the replacement, the incoming cable terminations were inspected — the conductors were in good condition with no heat damage extending back into the cable, which confirmed the fault was contained within the switch itself.

A new like-for-like 100A double-pole isolator was fitted, the terminations were made off correctly to the manufacturer's specified torque settings, and the circuit was tested before being re-energised. The cooler was back in operation the same afternoon.

The customer was advised to have the full installation inspected — an EICR (Electrical Installation Condition Report) — to check whether any other circuits showed similar signs of deterioration. This is standard practice following an emergency fault of this nature, and gives the homeowner a complete picture of the installation's condition.

The rear of the removed switch, showing heat discolouration and damage to the terminal block. The fault was contained within the switch — the incoming cable was undamaged and the replacement was straightforward.

Job Summary

Warning Signs to Watch For

Electrical faults like this one rarely appear without warning. The signs are often subtle at first — easy to dismiss or attribute to something else. If you notice any of the following, treat it as urgent and call a qualified electrician:

None of these symptoms should be ignored. An electrical fire can develop quickly once arcing or overheating takes hold — and unlike a tripped breaker, a fire does not announce itself with a warning light.