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Electrical wiring

Extremely low frequency EMFs index » Overview | Power lines | Substations | Electrical wiring | Electrical appliances


The way that buildings are wired can produce high electromagnetic fields (EMFs) in the home, school and workplace. Even recently re-wired buildings can lead to problematic levels of fields, as wiring for low EMFs is not covered in the IEE wiring regulations. High magnetic and electric fields are commonly found near walls, ceilings of downstairs rooms, and the floors of upstairs rooms. In the UK, buildings usually have 'ring' circuits feeding the power sockets. These circuits always give rise to higher magnetic fields than 'radial' or 'tree and branch' wiring, which are commonly used in other countries. High magnetic fields can be caused by lighting circuits as well. Ideally the field levels in your home should be no higher than 0.1 microtesla (magnetic field) and 5 volts per metre (electric field). Some lighting circuits for fluorescent or halogen lights can create high EMF levels not only in the room in question, but also in rooms above.

The Institute of Electrical Engineers (IEE) provide a set of wiring regulations (known as BS7671 17th Edition) for electricians. These provide guidance for electricians to wire buildings in such a way as to avoid the danger of electric shocks for the people occupying them. The guidelines (which are not, in themselves, legally binding though do have legal implications) do not require low electromagnetic fields (EMFs).

Building wiring can be, and often is, responsible for high electromagnetic fields (EMFs) in the home, school and workplace. High levels of EMFs can aggravate, or even cause, a number of chronic health problems. You can use screened cables for wiring, but it is slightly more time-consuming and expensive to use than the ordinary type of cable, and most electricians do not see the need.

The Stakeholder Advisory Group on ELF EMFs (SAGE) was set up by the Department of Health to explore the implications and to make practical recommendations for a precautionary approach to power frequency electric and magnetic fields. It has now produced its first report, and more information, including on house wiring, may be found in this and in the supporting papers that are available from the Department of Health website.

Workplaces where there is heavy duty cabling involved in providing power for some processes can create very high EMFs. One factory near Liverpool had fields of over 1000 microtesla immediately above the cable, which crossed an area with no restrictions for workforce access.

Wiring used to be in metal 'conduits' (metal tubes that contained the cables). This generally resulted in very low EMFs. However, this was an expensive way of wiring a building, and was quite difficult to do. With the improvements in plastic technology, cables covered in plastic insulation were a much cheaper and easier way of installing electric power in a building. This became the 'norm'.

If changes are made to any part of wiring, by an electrician, then they have to sign off the whole of that circuit as meeting the appropriate regulations. Note that it is now illegal to re-wire someone else's property, without having the correct qualifications, or having the work formally inspected when complete and before "making live". (Building Regulations Part P) Demand switches (to reduce the exposure to EMFs at night) on lighting circuits are unnecessary if the house is wired for low EMFs. Installing demand switches on power circuits are more difficult because of the appliances (e.g freezers) which are meant to be on all the time.

Illnesses such as cancer and depression, are associated with living in electromagnetic fields above 0.2 microtesla (magnetic field) and ME has also been linked with high electric fields (measured in volts per metre).

We have more comprehensive information on (wiring 21 pages) available in our article library.

Powerwatch Comments If you are concerned about possible exposures to powerfrequency electromagnetic fields, then you can purchase or hire meters such as the ELF PF4 or the MagneMeter (both of which we designed) from EMFields. They come complete with straightforward instructions, and comparison levels to see how 'safe' your readings are, and EMFields will offer technical advice on your readings if you hire directly from them.