Why does my consumer unit main switch trip immediately when I turn it on – Advice from Electriman, North London Electricians

What is actually happening when your main switch trips instantly?

The main switch in your consumer unit, sometimes called the incomer or isolator, is designed to carry the load of your entire electrical installation. When it trips the moment you switch it on, it means something is causing an immediate overcurrent or fault condition serious enough to operate the protective device before any electricity can flow normally through your home.

This is your installation's safety system working correctly. The danger is not that it tripped, but what caused it to trip.

The most common reasons this happens are:

1. A major short circuit on one of your circuits, for example a wiring fault inside a socket, light fitting or appliance.

2. A large earth fault, where a live conductor has come into contact with earth somewhere in the system.

3. A failed or damaged piece of equipment plugged in and left switched on, such as a fridge, washing machine or electric shower.

4. Water ingress into a socket, outdoor fitting or the consumer unit itself.

5. In older installations, deteriorated cable insulation causing conductors to touch.

What you can safely do yourself:

1. Before touching anything, make sure your hands are dry and you are standing on a dry floor.

2. Switch off and unplug all appliances throughout the house.

3. Move all the individual circuit breakers or fuses inside the consumer unit to their off positions.

4. Now try switching the

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Electriman covers Mill Hill, Barnet, Finchley, Edgware, Enfield, Watford and surrounding areas. All work is Part P certified and fully insured.