Electricity - the mains supply

"What’s in the electricity meter cupboard"

With any work involving the electrical circuitry of your house, you will need to know what’s what when you look at the incoming supply.

The main components will be the service head, the meter, the consumer unit and the earth terminal.

Electricity service head

On no account should this item be interfered with.

Service headThe electricity supply from the Local Company arrives in your house at a main fuse. This is to prevent problems with your wiring from interfering with other supplies in the locality.

The fuse is in a sealed fitting to prevent tampering. This then feeds the meter via two large wires – one blue (old cable colour = black), one brown (old cable colour = red). These may be sheathed in grey so the colour coding may not be apparent.

Electric meter

The meter receives the electricity supply from the service head and measures the consumption of power in your house. There may be additional components like time clocks and switches if you make use of the ‘cheap rate’ night time supply. The dials on the meter record the number of units of power used so that you can be billed. This then feeds the consumer unit via a pair of large wires – one blue (old cable colour = black), one brown (old cable colour = red). These may be sheathed in grey so the colour coding may not be apparent.

Again, on no account should this meter be interfered with.

Consumer unit - referred to as the fuse board

Consumer unitThis is supplied with electricity from the meter and forms the main distribution point to the circuits in your house. The wires from the meter terminate at a double pole switch (double pole switches break both the live and neutral) inside the consumer unit. On the other side of the switch, the neutral is joined to a connector block which accommodates all the neutral, blue (old cable colour = black) wires from your circuits. The live, brown (old cable colour = red) goes to a bar, which sits behind one end of all the fuses. The link from here to the terminal of each circuit is protected by a fuse mounted between the two. Another connector block accommodates all the earth (green and yellow) wires from your circuits and connects them back to the main earth terminal.

Earthing and the earth terminal

As well as the items mentioned above, there will be a main connection block for Earth. This links the earth connection on your consumer unit and any other earth bonding wires (from metal fittings such a sinks, radiators and pipework) to the Electricity Company's earth.

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AlertThis material is " for information purposes " only. Strict rules govern what electrical work can be done without notification and inspection.
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