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February 20, 2006

Identifying Electricity Supply

Filed under: Electrical DIY — DO or DIY @ 11:51 am

3 – Electricity

In the UK, most homes are supplied with electricity via cables either underground or overhead. This connects to a sealed terminal box located inside of your home, from which two cables run to an electricity meter and two cables run to the consumer unit.  The consumer unit is often located under the staircase, in the hallway or in the garage – it distributes electricity in your home.

Most consumer units include MCB’s  (miniature circuit breakers) that automatically switch off in case of faults or colour-coded fuses that enables you to locate them and switch off the power to a specific circuit..

There are cables running from the consumer unit to supply various circuits in your home. These are the usual circuits:

Ring Main Circuit

This is the most common circuit. It connects the power points in a loop then returns to the consumer unit. Power points can be fitted by adding spurs to the ring main.

Dedicated Circuit.

Some appliances such as cookers use much more power and require a dedicated circuit supplying electricity only to them.

Radial circuit

The main circuit used to be radial rather than ring. This can also feed many sockets, but it terminates at the end of the last power point. Most lighting runs on radial circuits because a single circuit could not cope with the combined wattage of many light bulbs.

How to isolate circuits

If your lights suddenly go off, or an electrical device (e.g. an iron) blows the circuit you will need to go the consumer unit.  You will need to check whether it is a modern consumer unit with MCBs or one with fuses. If you’re not sure call an electrician.

With MCBs

To do it yourself, first make sure that the main switch in the consumer unit is turned off – it may already have automatically switched off if all power in the house has gone off. 

Then unplug or switch off the electrical device that caused the power failure.
Then go back to the consumer unit and take off its cover.

The “blown” MCB switch is normally in the down position – just push it up again and the circuit should now function when you put the main switch back on.

With Fuses

It’s less easy with fuses – so it’s best to call an electrician Don’t touch the consumer unit or turn the main switch off – wait for the electrician to arrive. He’ll turn off the main switch then will take out each fuse in turn and inspect it. When the faulty one is identified, it will need to be repaired with the correct amperage fuse wire. He’ll then turn the main switch back on again and check that everything is working.

Working with electricity is dangerous – if you’re not competent, call an electrician to fix any problems. In the UK, most electrical work has to be carried out by a qualified electrician.  Read more about regulations re electrical DIY.

Also, before you start any DIY job, make sure you have a first-aid kit, you’re wearing comfortable & sensible clothing!

Identifying Services

Before you do any DIY work or repair on your home, you should be able to identify and isolate your gas, electricity and water supplies.  Read our other articles about identifying water & gas supply or how to drain your water system.

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