The 17th Edition of the Wiring Regulations has many changes in requirements that we will be covering over the next few editions of VoltiBULLETIN. One of these changes concerns Special Locations, where there are several new categories. Here, we cover Special Locations - rooms containing bath(s) or shower(s):
Typical examples include marinas, or locations containing swimming pools. Such locations clearly feature particular inherent or environmental circumstances (in these case wet or damp, with or without salt) that demand different IP codes for equipment and accessories and supplementary bonding is required within the restricted zones.
The Special Locations contained in the 16th Edition have been revised to align with the latest IEC and CENELEC standards.
Locations containing a bath or shower:
Under the16th Edition, there is (remember that the 16th Edition still applies until after the 2nd July 2008, when installations should comply only with the 17th Edition) the requirement is for all electrical equipment in bathrooms to be bonded together along with all metal pipework. This supplementary bonding connects to the circuit protective conductors - ie: the earth wiring - of the electrical equipment inside the bathroom(s). It must not be taken back to the main earth terminal in the consumer unit.
Again under the requirements of the 16th Edition, 2.5mm bonding conductors are suitable in circumstances where the cable is protected inside conduit or trunking (or safely under floorboards or within walls). If, however, any part of the conductor is not so protected, then a 4mm bonding conductor must be used. If any of the units in a bathroom are supplied using plastic pipes, then these units do not need supplementary bonding, even if they have exposed metal fittings. All electrical equipment still needs to be supplementary bonding.
The requirements of the 17th Edition, however, are different. In particular, the changes from the 16th Edition, are substantial. Section 701 in the 17th Edition covers locations containing a bath or a shower.
In terms of earth bonding in bathrooms, no longer is supplementary equipotential bonding - between metallic service and waste pipes and the earth connections of equipment required. However, this is only so if the main bonding of services within the property is in place and the metallic pipework can be proved by testing to be continuous. This means that the need for green and yellow cables in bathrooms and shower rooms is unlikely to be necessary.
The zones have been simplified. Zones 0, 1 and 2, as defined in the 16th Edition, are retained. Zone 3 is removed.
Socket-outlets, previously banned from bathrooms because of the risk of dampness causing electric shock, are now allowed, but they must be fitted three metres from the boundary of Zone 1. This probably means that many bathrooms will not be allowed to actually have socket-outlets, as they will be too small to comply with the new three metres rule. Importantly, all circuits need now 30mA RCD protection. However, any such socket-outlet would probably have to be on a spur, because any circuit entering an area with a bath or shower must terminate there and not carry on to any other area.
Note also that all cables buried in walls surrounding bathrooms (and shower rooms), regardless of the pints they are serving, have to be protected by 30mA RCDs.
Separated Extra Low Voltage (SELV) socket outlets and shaver socket outlets are permitted, provided that they are more than 3m from Zone 1.
The 30mA RCD protection requirement now applies also, under the 17th Edition, for ALL socket outlets in a home, as follows:
This important change (Chapter 41) concerns socket-outlets in the domestic environment. Additional protection is now required for all socket-outlets - for automatic supply disconnection. Specifically, in AC systems, such additional protection is to be provided by using an RCD (I?n not exceeding 30mA). Such RCDs will be provided for the following:
- Socket outlets not exceeding 20A rating for use by ordinary persons and intended for general use, and mobile equipment not exceeding 32A rating for use outdoors.
- Mobile equipment not exceeding 32A rating for use outdoors.
Therefore, essentially, every domestic room - including bathrooms etc - now requires RCD protection for each socket, though there is debate about the best way of achieving the required protection. The only exceptions are socket-outlets for use under the supervision of skilled or instructed persons (in certain commercial / industrial locations), or a specific labelled, or 'otherwise suitably identified', socket-outlet provided for the connection of a particular item of equipment. There is also an exception for deep freezers where nuisance tripping could ruin foodstuffs or make them dangerous.
Definitions of Equipotential Bonding:
Although supplementary equipotential bonding is no longer required in bathrooms (or shower rooms) under the requirements of the 17th Edition, it is still important not to confuse supplementary bonding with equipotential bonding on gas and incoming water supply immediately upstream of the cocks. Equipotential bonding will always be required where protection against electric shock (indirect contact) is provided by Earthed Equipotential Bonding and Automatic Disconnection of Supply (EEBADS). There are, essentially, three forms of bonding, and they should not be confused with 'earthing'. The following are definitions (though not defined as such in the 17th Edition):
- Main Equipotential Bonding - This applies to all installations where EEBADS is used.
- Supplementary Equipotential Bonding - This applies to some Special Locations and installations, and other special circumstance installations where EEBADS is used. Remember, no longer is supplementary equipotential bonding required in bathrooms.
- Additional Equipotential Bonding - This applies where EEBADS is used where disconnection times for circuits cannot be met, and where circuits with differing disconnection times come from a common distribution board.
Where main equipotential bonding of metal services is necessary, main equipotential bonding conductors are required . The following metal parts should be connected to the main earthing terminal, where they are extraneous-conductive-parts:
- Metal water service pipes.
- Metal gas pipes.
- Other metal service pipes (including oil and gas supply
pipes) and ducting. - Metal central heating and air conditioning systems.
- Exposed metallic structural parts of the building.
- Lightning protection systems.
- The last three are, perhaps, unlikely to apply in the domestic environment.
Other bonding issues:
Alterations and additions to an installation Regulation 131.8, which was previously numbered 130-07-01 in BS 7671:2001(2004), now has been amended to include the words 'if necessary'. The reason is that when making an alteration or addition to an existing installation, Regulation 131.8 states that, amongst other requirements, the earthing and bonding arrangements are to be adequate for the intended altered circumstance. The words 'if necessary' have been added to clarify that, in some instances, the condition of the existing earthing and bonding arrangements may not have any bearing on the intended altered circumstance and would, therefore, not need to be upgraded.
In terms of protective bonding, it has been established whilst assessing an existing installation, prior to an alteration to the fixed installation, that the main equipotential conductors are undersized and do not comply with the 17th Edition. Is this acceptable? The answer is that there has been no change or relaxation from the 16th
Edition. Regulation 131.8 requires that the bonding arrangements are adequate and the requirements for sizing such conductors can be found in Chapter 54.
Other Special Locations:
There are other Special Locations in the 16th Edition. The 17th Edition has them too, but there have been changes and additions. These Special Locations have been revised to align with the latest IEC and CENELEC standards. So the existing and new Part 7s are [new Part 7s designated (n)]:
Section 701 - Locations containing a bath / shower - Covered already.
The 17th Edition includes additional sections on special locations not currently included, as follows:
Section 702 - Swimming pools and other basins - The requirements now include fountains and the zones have changed from A, B, and C to 0, 1, and 2 (ie: numeric, not alphabetic). There has been a simplification of lighting issues.
Section 703 - Rooms and cabins containing all sauna heaters (not just hot air). Zones are now 1, 2 and 3.
Section 704 - The 17th Edition now covers construction and demolition sites. The reduced disconnection times and 25V equation no longer appear.
Section 705 - Agricultural and horticultural premises. No 25V or reduced disconnection times.
Section 706 - Conducting locations with restricted movement.
Section 708 - Electrical installations in caravan/camping parks and similar locations. (Currently Division Two 608).
Section 709(n) - Marinas and similar locations. There are particular electrical installation risks associated with these. Water, salt and relative movement of structures all cause problems, and the presence of salt water, dissimilar metals and a potential for leakage currents increases corrosion rates. Because of the damp, there is also greater risk of electric shock.
Section 711 (n) - Exhibitions, shows and stands. The particular risks associated with these arise from the temporary nature, the lack of permanence, severe mechanical stresses and access to the general public.
Section 712 (n) - Solar photovoltaic (PV) power supply systems.
Section 717 (n) - Mobile or transportable units.
Section 721 - Electrical installations in caravans and motor caravan parks. Each socket outlet must now be individually protected with overcurrent and RCD protection.
Section 740(n) - Temporary electrical installations for structures, amusement devices and booths at fairgrounds, amusement parks and circuses.
Section 753(n) - Floor and ceiling heating systems.
Note that if there is overlap between the 16th and 17th Editions on a longer project, the client should be consulted and made aware of the situation. An agreement should be reached between the electrical contractor, responsible for the construction element of the electrical work and the client.