There are extra considerations for electrical wiring in a bathroom.
Article currently incomplete.
Why are bathrooms special?
In a bath or shower room you may wet, naked, and barefoot. These factors can lower your skin's electrical resistance, and also mean you have a better connection to an electrical earth due to the lack of shoes etc. The result is that any electrical shock could have far more serious consequences - large electrical currents could flow through you to earth.
Hence there are a number of additional measures and precautions that come into play where electrical installations are located in places such as these where users are at a higher than normal risk of injury or death from the effects of electric shock.
What is a "bathroom"
Bath and shower rooms are one such example of these special locations. Others include:
- Swimming pool areas
- Steam rooms
Note that there are also some locations that may place water in electricity in close proximity, which are not considered to pose special risks. This include:
- Rooms containing just a sink or basin, but no shower or bath
Finally you have Kitchens which have their own particular risks - but the requirements are subtly different from bathrooms.
Bathrooms are divided into zones for electrical purposes.
- The interior of the bath or shower
- Electrical appliances here must be IPX7
- Electrical appliances here must run on SELV at a maximum of 12v ac or 30v dc
- area directly above zone 0, upto a height of 2.25m above the bath or shower, or to the height of the maximum reach of the shower head if that is greater.
- Electrical appliances must be SELV with the transformer outside all the zones
- Electrical appliances must be IPX4 or better
- area beyond zones 0&1, extends 60cm horizontally and upto 2.25m vertically beyond zones 0&1.
- Also area within 60cm of sinks, plus area directly below this
- Electrical appliances must be IPX4 or better
- Electrical appliances here must run on SELV wth transformer outside the zones
- zone 3 ceased to exist in 2008 with the 17th edition of the wiring regs.
- Outside zone 2
- Under the bath if a tool is required to gain access
- Shaver units permitted
- SELV appliances permitted
- Non-selv portable appliances in bathrooms must be physically prevented from entering zone 2. This is usually done by limiting mains lead length on the appliance.
Unsuitable in all zones
- Some appliances are marked unsuitable for bathrooms
- Some appliances are not thus marked, but are still unsuitable. CRT TVs are one example.
Unless an installation complies with the latest requirements of the 17th edition (i.e. all required main equipotential bonding is installed, and additional protection for all circuits used in the bath / shower room is provided by a RCD with trip current of 30mA or less) then supplementary equipotential bonding is required.
See Earthing and Bonding for more detail.
Electrical Equipment in bathrooms
One fundamental requirement for any electrical equipment (be it an appliance or an accessory such as a switch) is that it should be suitable for the location. This means one needs to apply some common sense when choosing and installing equipment.
Ordinary electrical light switches are permitted in a bathroom, however one should only use them where there is no possibility that someone could operate them from the bath or shower. They also should not be in locations where they are likely to get splashed or have excess steam or vapour directed at them. Traditionally, pull switches are used to mitigate some of these risks. Common alternatives include using conventional switches located outside of the room.
Switches will also be required for other devices like heaters or towel rails. Some may be intended for day to day use (i.e. "functional switching"), other may only be required just for isolation when carrying out maintenance. Again, the type of switch selected will depend on where it is going, as well as when you anticipate it being used.
Historically, 13A general purpose mains sockets have not been permitted in bathrooms at all. The 17th edition has introduced a slight relaxation of this, but it will only apply for very large bathrooms since it permits a socket to be installed as long as it is at least 3m from the outer edge of zone 2.
Shaver sockets are permitted in zone 2, but only if they are of the isolating type with integral transformer.
Spurs / Cable connection units
Electrical equipment in a bathroom will generally need to be via a permanent "hard wired" connection. Typically to a cable outlet unit (switched or otherwise), or a fused spur unit (again, switched or otherwise). If an electrical appliance requires external functional switching (i.e. day to day control, rather than just for isolation purposes) then this may be better provided by a pull switch even if the connection unit includes a switch for isolation purposes.
Towel Rails / Radiators
Section to be written.