When installing an extractor fan in a bathroom, it is important to remember that under the wiring regulations a room containing a bath or shower is considered to be a special location and certain conditions apply.
These conditions apply because of the increased risk of electric shock due bare wet skin which results in a reduction in body resistance and the increased possibility of large areas of the body coming into contact with earth potential.
The new wiring regulations introduced in 2008, the 17th edition, has changed the conditions set out in the 16th edition. For example, RCDs are required for all circuits in locations that contain a bath or shower. The requirements for local supplementary bonding have been relaxed if certain conditions are met.
Rooms containing a bath or shower are divided into zones with different conditions being applied to each zone. The new zones are Zone 0, Zone 1 and Zone 2. Zone 3 no longer applies. This is partly due to the introduction of RCDs and partly to help bring the UK in line with the electrical standards in Europe.
Zone 0 is inside the bath tub or shower basin – The external influence is IPX7 no accessories or switchgear to be installed.
Zone 1 is the space above the bath tub or shower basin up to a height of 2.25m – The external influence is IPX4 only SELV circuits; Extra low voltage via safety source such as a transformer installed outside the zone
Zone 2 is the space that extends horizontally from the edge of the bath tub or shower basin for 0.6m to a height of 2.25m – The external influence is IPX4 or IPX5 if water jets are used. No switchgear or accessories in this zone unless SELV with the safety source outside the zone or a shaver socket that complies with BS EN 61558-2-5