GN4 on Consumer units.
3.8 Enclosures
Where enclosures are constructed on site, reference must be made to the appropriate product standard for the necessary resistance to heat and fire. In the absence of such a standard, maximum likely temperatures of the enclosure must be determined and enclosures selected that are well able to withstand these temperatures.
BS 476 Fire tests on building materials and structures (Part 4 – Non-combustibility test for materials, Part 12 – Method of test for ignitability of products by direct flame impingement) provides type tests for materials.
Where equipment is installed in an enclosure or enclosed space, e.g. ballasts or other controlgear within a ceiling, adequate arrangements must exist for safely dissipating heat generated.
3.8.1 Consumer units and similar assemblies in domestic premises
Regulation 421.1.201, which was added to BS 7671:2008 by Amendment No. 3 (2015), requires consumer units and similar switchgear assemblies installed in domestic (household) premises to comply with BS EN 61439-3 and to either:
(a) have their enclosure manufactured from non-combustible material or
(b) be enclosed in a cabinet or enclosure constructed of non-combustible material and complying with Regulation 132.12.
An example of a non-combustible material, according to Note 1 to Regulation 421.1.201, is ferrous metal, such as steel.
The implementation date for Regulation 421.1.201 is 1 January 2016 (six months after Amendment No. 3 comes into effect); see Note 2 to the regulation. However, this does not preclude compliance with the regulation prior to that date.
Where option (b) above is used, it is important that the cabinet or enclosure is suitably selected and erected to meet the requirements of Regulation 132.12. These relate to adequacy of space for initial installation and later replacement individual items equipment, and accessibility of the equipment for operation, inspection, testing, fault detection, maintenance and repair.
The intent of Regulation 421.1.201 is, as far as is reasonably practicable, to contain any fire within the non-combustible enclosure or cabinet and to minimise the emission of flames to the surroundings or into conduits trunking or ducting. Consequently. both of the following are necessary, irrespective of which of options (a) or (b) is adopted.
The non-combustible enclosure or cabinet must provide a complete envelope (e.g. base, cover, door and any components such as hinges, screws and catches) as necessary to maintain fire containment. All blanks, circuit-breakers and other devices must be contained within the non-combustible enclosure or cabinet. The installer must seal all openings into the non-combustible enclosure or cabinet for cables, conduits, trunking or ducting that remain after the installation of cables. Good workmanship and proper materials must be used and account must be taken of the manufacturer's relevant instructions, if any.
The phase 'similar switchgear assemblies' in Regulation 421.1.201 means assemblies used for the same fundamental application as a consumer unit. An example could be a three-phase distribution board intended to be operated by ordinary persons.
Regulation 421.1.201 is intended to apply consumer units and similar switchgear assemblies to BS EN 61439-3 inside all domestic (household) premises, including their integral / attached garages and outbuildings and those in close proximity.
3.9 Terminations
Regulation 526.5 is the general requirement for the enclosure of terminations and joints of live conductors and PEN (combined protective and neutral) conductors. A further important requirement is to provide an enclosure which will protect the joint or connection against the environment.
Poor terminations and connections are cited as a frequent cause of fire, and close attention is required by the designer, the installer and the person responsible for the inspection and testing to all aspects of the subject.
For this reason, Regulation 526.5 requires that all terminations and joints at whatever voltage, including ELV, shall be made within a suitable enclosure. Because there is always a risk of overheating and consequent fire at a joint or termination, these must be enclosed and the enclosure where not incorporated in suitable equipment or accessory must meet the specified fire resistance requirements. This applies equally to LV and ELV connections, to luminaires and to similar equipment. The relatively high currents of ELV equipment mean particular care has to be taken with joints and terminations. When compression joints are used, crimping tool, lug and cable must be compatible.
Other matters which should be considered under this heading are:
(a) dirty or misaligned equipment contacts which may give rise to local heating, and
(b) loose or inadequate cable supports which may place mechanical stresses on connections, causing overheating.
One method, which could be considered when inspecting electrical installations for signs of overheating, is the use of thermal imaging. This is not required by BS 7671 and would therefore be in addition to the inspections and tests stated in Part 6 of BS 7671.
The use of thermographic surveying is discussed in Guidance Note 3: Inspection & Testing.
3.8 Enclosures
Where enclosures are constructed on site, reference must be made to the appropriate product standard for the necessary resistance to heat and fire. In the absence of such a standard, maximum likely temperatures of the enclosure must be determined and enclosures selected that are well able to withstand these temperatures.
BS 476 Fire tests on building materials and structures (Part 4 – Non-combustibility test for materials, Part 12 – Method of test for ignitability of products by direct flame impingement) provides type tests for materials.
Where equipment is installed in an enclosure or enclosed space, e.g. ballasts or other controlgear within a ceiling, adequate arrangements must exist for safely dissipating heat generated.
3.8.1 Consumer units and similar assemblies in domestic premises
Regulation 421.1.201, which was added to BS 7671:2008 by Amendment No. 3 (2015), requires consumer units and similar switchgear assemblies installed in domestic (household) premises to comply with BS EN 61439-3 and to either:
(a) have their enclosure manufactured from non-combustible material or
(b) be enclosed in a cabinet or enclosure constructed of non-combustible material and complying with Regulation 132.12.
An example of a non-combustible material, according to Note 1 to Regulation 421.1.201, is ferrous metal, such as steel.
The implementation date for Regulation 421.1.201 is 1 January 2016 (six months after Amendment No. 3 comes into effect); see Note 2 to the regulation. However, this does not preclude compliance with the regulation prior to that date.
Where option (b) above is used, it is important that the cabinet or enclosure is suitably selected and erected to meet the requirements of Regulation 132.12. These relate to adequacy of space for initial installation and later replacement individual items equipment, and accessibility of the equipment for operation, inspection, testing, fault detection, maintenance and repair.
The intent of Regulation 421.1.201 is, as far as is reasonably practicable, to contain any fire within the non-combustible enclosure or cabinet and to minimise the emission of flames to the surroundings or into conduits trunking or ducting. Consequently. both of the following are necessary, irrespective of which of options (a) or (b) is adopted.
The non-combustible enclosure or cabinet must provide a complete envelope (e.g. base, cover, door and any components such as hinges, screws and catches) as necessary to maintain fire containment. All blanks, circuit-breakers and other devices must be contained within the non-combustible enclosure or cabinet. The installer must seal all openings into the non-combustible enclosure or cabinet for cables, conduits, trunking or ducting that remain after the installation of cables. Good workmanship and proper materials must be used and account must be taken of the manufacturer's relevant instructions, if any.
The phase 'similar switchgear assemblies' in Regulation 421.1.201 means assemblies used for the same fundamental application as a consumer unit. An example could be a three-phase distribution board intended to be operated by ordinary persons.
Regulation 421.1.201 is intended to apply consumer units and similar switchgear assemblies to BS EN 61439-3 inside all domestic (household) premises, including their integral / attached garages and outbuildings and those in close proximity.
3.9 Terminations
Regulation 526.5 is the general requirement for the enclosure of terminations and joints of live conductors and PEN (combined protective and neutral) conductors. A further important requirement is to provide an enclosure which will protect the joint or connection against the environment.
Poor terminations and connections are cited as a frequent cause of fire, and close attention is required by the designer, the installer and the person responsible for the inspection and testing to all aspects of the subject.
For this reason, Regulation 526.5 requires that all terminations and joints at whatever voltage, including ELV, shall be made within a suitable enclosure. Because there is always a risk of overheating and consequent fire at a joint or termination, these must be enclosed and the enclosure where not incorporated in suitable equipment or accessory must meet the specified fire resistance requirements. This applies equally to LV and ELV connections, to luminaires and to similar equipment. The relatively high currents of ELV equipment mean particular care has to be taken with joints and terminations. When compression joints are used, crimping tool, lug and cable must be compatible.
Other matters which should be considered under this heading are:
(a) dirty or misaligned equipment contacts which may give rise to local heating, and
(b) loose or inadequate cable supports which may place mechanical stresses on connections, causing overheating.
One method, which could be considered when inspecting electrical installations for signs of overheating, is the use of thermal imaging. This is not required by BS 7671 and would therefore be in addition to the inspections and tests stated in Part 6 of BS 7671.
The use of thermographic surveying is discussed in Guidance Note 3: Inspection & Testing.
