RegulationsAmendment No. 3 BS 7671 & Consumer Units for use in Domestic (Household) Premises

REGULATION 421.1.201
From January 2015 Amendment No. 3 to BS 7671 IET Wiring Regulations prescribe that within domestic (household) premises, consumer units and similar switchgear assemblies shall have their enclosures manufactured from noncombustible material, or be enclosed in a cabinet or enclosure constructed of non-combustible material and comply with product standard BS EN 61439-3.

What are Domestic Household Premises?
Typical domestic household premises would include single and multiple occupancy homes such as houses, bungalows, high rise & low rise flats, apartments, student lets, sheltered accommodation, farmhouses, houseboats, static homes, home office, attached garages, workshops and detached summerhouses etc. Other types of building you may need to consider (these may be commercial ventures) but also where people live and guests sleep overnight such as guest houses, hostels, bed & breakfast accommodation, nursing homes etc.

What is Non-combustible Material?
There are many types of non-combustible material, however, amendment 3 of the 17th Edition regulations provides an acceptable example as ferrous metal i.e. Steel Consumer Units.

regulations-1What is an Enclosure?
The consumer unit enclosure must be manufactured from a non-combustible material so as to limit the spread of fire. An enclosure means the box, cover, door, hinges, handle and any components required to maintain the integrity of the unit.

What is Similar Switchgear?
Similar switchgear is switchgear that is used for the same fundamental application i.e. a circuit protection assembly with two pole isolator and one or more circuit protection devices, e.g. fuse switch, garage unit or PV switchgear etc.

What are Cabinets?
Typical cabinets are meter cabinets that are normally built into the fabric of the building and that may or may not
include consumer units within. If the cabinet is of an all metal construction (non-combustible), then a standard skeleton consumer unit (FAL) can be installed within. If the cabinet is of a combustible material, a metal consumer unit is required.

The most important change from the 16th to the 17th Edition is the increased use of residual current devices. Previously, RCDs have only been required to protect socket outlets for use outdoors (where disconnection times were unable to be achieved), and special locations.

With the introduction of the 17th Edition, this has changed, the term ‘Additional Protection’ is used throughout the publication. The use of RCDs are recognised as a means of providing additional protection in the event of a failure of the provision for basic protection, as an additional means of fault protection, and to protect against carelessness by users.

If an RCD is used to provide Additional Protection it must then meet the requirements of the regulation 415.1.1. That is, that the RCD must have a rated residual operating current not exceeding 30mA, and an operating time not exceeding 40ms at 5x the rated current.

The 17th Edition refers to various applications and installations which require additional protection by the means of the aforementioned RCD.

The first of which is found in Regulation 411.3.3, which has been modified in Amendment 3, where by additional protection is required for:

a). Socket outlets with a rated current not exceeding 20A
b). Mobile equipment with a current rating not exceeding 32A for use outdoors

An exception to ‘a’ is permitted:

1). Where, other than for an installation in a dwelling, a documented risk assessment determines that the RCD protection is not necessary, or
2). For a specific labelled or otherwise suitably identified socket outlet provided for connection of a particular item of
equipment

This regulation has been modified in Amendment 3 to provide less exceptional circumstances where RCD’s may not be used. The document doesn’t define the risk assessment, but the installer should consider each individual socket in all areas, and should include consideration and timings for regular assessments. Labelling could be interpreted as a socket outlet marked ‘fridge’, ‘freezer’. ‘I.T.’