Rewiring a House

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The property before work began

The property featured on this page was undergoing a rewire because of fire damage. The electrical installation had become unsafe due to a lack of testing and maintenance. As a result a cable became overheated and started a fire. No-one was hurt as one of the occupants noticed the smoke and raised the alarm. A smoke detector was not installed. All of the photos shown here were taken in the kitchen, but the principle of installing cables and accessories in the first and second fix would apply across the property.

Fittings and ceiling removed View to back of kitchen

Fittings and ceiling removed

View to back of kitchen

Old damaged fitting Old burried cables

Old damaged fitting

Old burried cables

Running in new cables

The first part of the electrical rewire job is to remove as much as possible of the old electrical installation. This means turning off the power and removing the old consumer unit, before removing all the old accessories including plug sockets and light fittings. The electrician would normally leave one double socket live close to the supply equipment. It is best to plan to move out of a house during a rewire or better still have the rewire done before you move in.

Next is the dusty part of the job. Power tools will be used to cut chases in the walls ready for the new electrical cables. Sections will be chiselled out so that when the back boxes for sockets are fixed to the walls the plasterers can run the plaster over the cables and flush with the accessories. Once the chases are in position the floorboards will be raised and holes or notches cut to allow the cables to be run through from point to point.

Removing old socket outlets Running in new cables

Removing old socket outlets

Running in new cables

Mounting back boxes First fix of scoket and appliance supplies

Mounting back boxes

First fix of socket and appliance supplies

Finishing the first fix

The cables in a domestic installation will typically be PVC / PVC twin and earth cable with copper cores. The size of the cable will vary depending on the load and the length of the run. Remember that different types of cables can carry different loads and rating factors must be applied to cables before a cable size is selected; common sizes in domestic situations are as follows;

1.5mm live, 1mm earth – often used for 6amp and 10amp lighting circuits
2.5mm live, 1.5mm earth – often used for 32amp final ring or 20amp radial circuits
6mm live, 2.5mm earth – used on 32amp cooker circuits
10mm live, 4mm earth – recommended for 40amp shower circuits

Older properties may have 1mm live with 1mm earth but this is no longer used due to its limited capacity.

First fix of ceiling lights Protective bonding for gas and water supplies

First fix of ceiling lights

Protective bonding for gas and water

Old consumer unit Close-up of old consumer unit

Old consumer unit

Close-up of old consumer unit

New consumer unit and second fix

Once the back boxes are in place and the new cables have been run from electrical point to point to create the circuits, the cables will be protected with capping. The capping will prevent the plasterer’s trowel from damaging the insulation when the walls are covered. The cable ends will be placed inside the back boxes out of the plasterer’s way.

The new plaster will take about two days to dry sufficiently before the electricians can return to fit the accessories such as socket facia and light switches and fittings. Once these are in place the new consumer unit will be fitted. It is a general requirement now that new consumer units have circuits split between two RCDs

Testing new consumer unit New split load RCD protected consumer unit

Testing new consumer unit

New split load RCD protected consumer unit

Second fix socket outlets in place Sockets and ceiling lights in place

Second fix socket outlets in place

Sockets and ceiling lights in place

Finishing the job and the completed work

Final testing will be done on the circuits before the job is considered to be complete. Testing consists of a series of dead and live tests that confirm the installation is safe and ready for use.

Tightening the accessories Finished kitchen

Tightening the accessories

Finished kitchen

View to window The cooker and worktops

View to window

The cooker and worktops

 

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