Re-take - Useful Information for 2394 :

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Change here . O.S.G.

O.S.G. 2.4.1. pre- 2011: ◄
Portable generator used with a floating earth . Small portable generators, ranging in output from 0.3kVA to 10kVA single-phase often have a floating earth .

O.S.G. 2.4.1. (A3 - 2015) ◄
Portable generator used with a floating earth . Small portable generators, ranging in output from 0.2kVA to 10kVA single-phase often have a floating earth .

refer us to . regulation . 551.4.4.

No change . 2008 / 2011 / 2015
Additional requirements for protection by automatic disconnection where the installation and generating set are not permanently fixed .

This regulation applies to portable generating sets and to generating sets which are intended to be moved to unspecified locations for temporary or short-term use . Such generating sets may be part of an installation which is subject to similar use . This regulation does not apply to permanent fixed installation’s.

Note: For suitable connection arrangements see BS-EN-60309 series.

 

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The importance in getting O.S.G. ( A3 2015)

Changes are made ( A1 2011 & A3 2015) :book:

O.S.G. pre-2011: ◄
7.2.5. Requirements for RCDs
RCDs are required:
411.5.
411.3.3. (i)
701.411.3.3.
411.3.3. (ii)
522.6.101
522.6.102
522.6.103
for cables without earthed metallic covering installed in walls or partitions with metal parts ( not including screws or nails) and not protected by earthed steel conduit or the like .

411.3.3. (b) i .
411.3.3. (a) ii .
(ii) socket-outlet circuits un situations where the use of equipment and work on the building fabric and electrical installation is controlled by skilled or instructed persons, for example, in some industrial and commercial locations; see 3.6.2.2.

O.S.G. 2015: ◄
7.2.5. Requirements for RCDs
RCDs are required:
411.5.
411.3.3. (i)
701.411.3.3.
411.3.3. (ii)
522.6.202.
522.6.203. (f)
for cables without earthed metallic covering installed in walls or partitions with metal parts ( not including screws or nails) and not protected by earthed steel conduit or the like .

(( Making you aware ))
Note: Metallic capping does not meet the requirements for (( mechanical protection )) as required by 522.6.204 . Metallic capping is used to protect the cables during the installation process and, once plastered over, does not provide any further protection .

Similarly, metallic capping would not meet the requirements for 522.6.204. (ii) or (ii) and would not satisfy the requirements of BS-7671: for a (( protective-conductor ))

A single layer of steel with a minimum thickness of 3mm is generally considered to provide sufficient mechanical protection against penetration by nails, screws and the like, except where short-fired nails are likely to be used.

411.3.3. (a)
specific labelled socket-outlets, for example, a socket-outlet for a freezer. However, the circuit cables must not require RCD protection as per (e) and (f) above, that is, circuit cables must be enclosed in earthed steel conduit or have an earthed metal sheath or be at a depth of at least 50mm in a wall or partition without metal parts.

411.3.3. (b)
In non-domestic premises, a documented risk assessment determines that the risk to users is sufficiently low for socket-outlets with a rated current not exceeding 20A .

2015: . as per (e) and (f) ................ 2011: as per (v) and (vi)

 

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Schedule of Inspections for the Electrical Installation Certificate :icon_bs:

The existing Schedule of Inspections for the Electrical Installation Certificate has been deleted. It is replaced by (a) and (b) below, one of which (as applicable) is to be used as the basis for the Schedule of Inspections to accompany the certificate.

(P/422) a. For installations in domestic and similar premises with up to 100A supply, a model schedule of inspections for new installation work in such premises.
b. For installations not covered by (a), a list of examples of items requiring inspection during initial verification of new installation work.

(a) and (b) contain a greater number of items than were included in the existing Schedule of Inspections (deleted by Amendment No. 3), many of which are quite detailed or particular. This gives (a) and (b) the advantage of being more like checklists. A few examples of items in (a) and/or (b) are:

1.0. items relating to the electrical intake equipment ;
such as the:
1.1. service cable
1.2. service head,
1.3. distributor’s earthing arrangement
1.5. metering equipment.

2.0. items relating to parallel or switched alternative sources of supply.

7.0. items relating to consumer units or distribution boards, such as:
7.1. adequacy of access and working space for items of electrical equipment including switchgear (132.12);
7.2. presence of linked main switch(s) (537.1.4, 537.1.5, 537.1.6);
7.4. suitability of enclosure(s) for IP and fire ratings (416.2, 421.1.6, 421.1.201); and
7.6. confirmation that all conductor connections are correctly located in terminals and are tight and secure.

8.0. items relating to circuits, such as:
8.1. adequacy of conductors for current-carrying capacity with regard to type and nature of the installation; ( Section 523)
8.3. segregation/separation of Band I (ELV) and Band II (LV) circuits, and electrical and non-electrical services (528);
8.4. cables correctly erected and supported throughout including escape routes, with protection against abrasion (521, 522); and
8.14. provision of additional protection by RCD not exceeding 30mA (with a list of possible applications).

 

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Some changes in ( A3 - 2015 ) :icon_bs:

(P/417) Minor Electrical Installation Works Certificate

In Part 3 ( Essential Tests ) of the Minor Electrical Installation Works Certificate, the fields for insulation résistance test readings to be inserted have been changed from [ Old 2011 - “ Line/earth ” and “ Neutral/earth ” ] Now (( to ‘ Live-Live ’ and ‘ Live-Earth ’ 2015 ))

Also in Part 3, the amount of detail required to be inserted in relation to the testing of an RCD has been increased, such that the operating time at 5 IΔn ( as well as at IΔn ) is included, as is confirmation that the test button of the device operates satisfactorily. ............. ✓

In Part 4 (Declaration), a field has been added for details to be recorded of any permitted exceptions to Regulation 411.3.3 relating to the omission of RCD protection to socket-outlets. As mentioned above in relation to the similar field in the Electrical Installation Certificate, this exception may be used only for an installation other than in a dwelling. Where the exception is used, a copy of the risk assessment must be attached to the certificate as required by Regulation 411.3.3.

 

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Some changes in ( A3 - 2015 )

Electrical Installation Condition Report

In Section D (Extent and limitations of inspection and testing) of the Electrical Installation Condition Report, text has been added to the effect that an inspection should be made within an accessible roof space where other electrical equipment is present.

Section J (Particulars of installation referred to in the report) now includes separate tick boxes for main bonding conductor connections to water installation pipes, gas installation pipes, oil installation pipes, structural steel, lightning protection and any other parts (as referred to in Regulation 411.3.1.2) to which such connections have been made.

In Section K (Observations), the column headed ‘Further investigation required (yes/no)’ has been deleted. However, it is still possible to state that further investigation is required in relation to an observation, by means of additional classification code, ‘FI (Further investigation required)’, which is now recognised in Section K.

Note 9 of the notes for the person producing the report has been revised with regard to where the inspection has revealed an apparent deficiency that could not be fully identified due to the extent or limitations of the inspection. The note points out that if a further investigation may reveal that the deficiency warrants the award of classification code C1 (Danger present) or C2 (Potentially dangerous), a recommendation of further investigation required (Code FI) should be recorded at Section K (Observations). It should be appreciated, however, that an FI classification should not be recorded if the investigation could only be expected to lead, at worst, to the award of C3 classification (Improvement recommended) in relation to the observation.

Notes 7 and 8 of the notes of guidance for recipients have been revised with regard to the person who undertakes any necessary remedial work in relation to a deficiency revealed by the inspection. Instead of referring to ‘a competent person’, the notes now refer to ‘a skilled person competent in electrical installation work’. The change has been made to the notes in order to describe more clearly the qualities that should be possessed by the person chosen to carry out such remedial work.

Note 9 of the notes of guidance for recipients has been revised for the same reason as Note 9 of the notes for the person producing the report, mentioned earlier; that is, in relation to further investigation.

Note 10 of the notes of guidance for recipients has been revised with regard to the person who undertakes re-inspection of the installation at appropriate intervals. Instead of referring to ‘a competent person’, the note now refers to ‘a skilled person competent in inspection and testing of electrical installations’. The change has been made in order to describe more clearly the qualities that should be possessed by the person chosen to carry out such periodic inspections.

Some additions and modifications have been made to the Condition Report Inspection Schedule Guidance for the Inspector, and to the Condition Report Inspection Schedule for Domestic and Similar Premises with up to 100 A Supply. The result is that these schedules, which are essentially checklists, are more comprehensive than they previously were.

In the Condition Report Inspection Schedule for Domestic and Similar Premises with up to 100 A Supply, the column headed ‘Further investigation required (yes/no)’ has been deleted. Also, the text in the schedule relating to the use of recommendation codes has been revised to take account of the introduction of the new Code FI (Further investigation required), mentioned earlier.

 

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Wiring Matters 54 - Special Edition , 2015
Reduction in maximum values of earth fault loop impedance in BS-7671:

Editor's note: references to the 'current' version of BS 7671 relate to BS 7671:2008(2011), i.e. the 'green cover' Regulations. This version is current until 30 June 2015. On 1 July 2015, BS 7671:2008+A3:2015 comes into effect.

One of the changes being introduced by BS 7671:2008+A3:2015 (IET Wiring Regulations Seventeenth Edition), which was published in January and comes into effect on 1 July, is a reduction of maximum values of earth fault loop impedance (Zs) in Tables 41.2, 41.3, 41.4 and 41.6.

Reason for the reduction
The reason for the reduction in the maximum Zs values is the introduction of the ‘minimum voltage factor’ given in Technical Report PD CLC/TR 50480:2011 Determination of cross sectional area of conductors and selection of protective devices.

Minimum voltage factor
The minimum voltage factor (Cmin) takes account of the fact that the voltage of the electricity supply to an electrical installation varies depending on time and place, changing of transformer taps and other considerations.

For example, for a low voltage supply given in accordance with The Electricity Safety, Quality and Continuity Regulations 2002 as amended (ESQCR), variations of up to 10% above or 6% below the declared voltage at the declared frequency are permitted, unless otherwise agreed in writing by the distributor, the supplier and the consumer (regulation 27(3) of the ESQCR refers).

The minimum voltage factor (Cmin) always has a value less than 1. Cmin is applied as multiplier to the nominal line voltage to Earth (U0) when determining maximum values of earth fault loop impedance (Zs).

Amendment No. 3 to BS 7671:2008 gives Cmin the value of 0.95 where the low voltage supply given in accordance with the ESQCR.

One might wonder why 0.95 was chosen rather than 0.94, given that the ESQCR permits the supply voltage to be as much as 6% below the declared value, as already mentioned. However, 0.94 was thought to be unrealistically low, and Technical Report PD CLC/TR 50480:2011 gives Cmin the value of 0.95 for the worst-case condition in a low voltage installation.

Tables of maximum earth fault loop impedance
As a result of the Cmin value of 0.95 mentioned above, all maximum values of Zs in Tables 41.2, 41.3, 41.4 and 41.6 of BS 7671 have been correspondingly reduced by Amendment No. 3 to 0.95 times (or 5% lower than) those in the current version of BS 7671.

For example, for a 32 A type B circuit-breaker to BS EN 60898 or the overcurrent characteristics of a 32 A type B RCBO to BS EN 61009-1, Table 41.3 in Amendment No. 3 gives the maximum Zs value of 1.37 ohms at a nominal voltage (U0) of 230 V. This compares with 1.44 ohms in the same table of the previous version of BS 7671.


Protective devices and voltages that are not covered in the tables of maximum earth fault loop impedance
Where it is necessary to find the maximum value of Zs for a protective device not covered in Tables 41.2, 41.3, 41.4 and 41.6 or for a nominal voltage (U0) other than 230 V, the formula given in Appendix 3 of BS 7671 (as revised by Amendment No. 3) can be used. Examples of protective devices not covered by the tables are fuses of higher current ratings and moulded-case circuit-breakers (MCCBs).

The revised version of the Appendix 3 formula, as given in Amendment No. 3, is reproduced below:
Zs = (U0 × Cmin) / Ia

where:

U0 is the nominal a.c. rms line voltage to Earth.
Cmin is the minimum voltage factor to take account of voltage variations depending on time and place, changing of transformer taps and other considerations.

NOTE 1: For a low voltage supply given in accordance with ESQCR, Cmin is given the value 0.95.
Ia is the current causing operation of the protective device within the specified time.


Measured values of Zs
When Zs values are measured at ambient temperature, account needs to be taken of the increase in resistance of the conductors with increasing temperature due to load current, as explained in Appendix 14 of BS 7671, before the measured values can be checked for compliance against the maximum values of Zs referred to in BS 7671.

Appendix 14 has been revised by Amendment No. 3 to BS 7671:2011.

 

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Current version .

411.3.3 Additional protection
In a.c. systems, additional protection by means of an RCD in accordance with Regulation 415.1 shall be provided for:
(i) socket-outlets with a rated current not exceeding 20A that are for use by ordinary persons and are intended for general use, and
(ii) mobile equipment with a current rating not exceeding 32A for use outdoors.
An exception to (i) is permitted for:
(a) socket-outlets for use under the supervision of skilled or instructed persons, or
(b) a specific labelled or otherwise suitably identified socket-outlet provided for connection of a particular item of equipment.

NOTE 1: See also Regulations 314.1(iv) and 531.2.4 concerning the avoidance of unwanted tripping.
NOTE 2: The requirements of Regulation 411.3.3 do not apply to FELV systems according to Regulation 411.7 or reduced low voltage systems according to Regulation 411.8.


Removal of the exception for socket-outlets for use under the supervision of skilled or instructed persons

Unlike the current version of Regulation 411.3.3, the new version does not permit the omission of RCD protection to a socket-outlet just because the socket-outlet is for use under the supervision of skilled or instructed persons.

The exception for socket-outlets for use under the supervision of skilled or instructed persons was removed because:

a. it was no longer seen as having any relevance, given the development in the application of RCDs to the general requirements of BS 7671 over recent years; and

b. there had been reports of the exception being abused, such as RCD protection to socket-outlets at a school being omitted on the basis that they were to be used under the supervision of a person instructed by the head teacher. :30:

New version ( A3 - 2015 )

411.3.3 Additional protection
In a.c. systems, additional protection by means of an RCD in accordance with Regulation 415.1 shall be provided for:
(i) socket-outlets with a rated current not exceeding 20A, and
(ii) mobile equipment with a current rating not exceeding 32A for use outdoors.

An exception to (i) is permitted:
(a) where, other than for an installation in a dwelling, a documented risk assessment determines that the RCD protection is not necessary, or
(b) for a specific labelled or otherwise suitably identified socket-outlet provided for connection of a particular item of equipment.

NOTE 1: See also Regulations 314.1(iv) and 531.2.4 concerning the avoidance of unwanted tripping.
NOTE 2: The requirements of Regulation 411.3.3 do not apply to FELV systems according to Regulation 411.7 or reduced low voltage systems according to Regulation 411.8.

NOTE 3: See Appendix 2, item 10 in respect of risk assessment.

 

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Documented risk assessment

Omitting RCD protection for any socket-outlet on the basis of a risk assessment is a serious matter and must never be done lightly. Such omission is not permitted for an installation in a dwelling; it is permitted only for an installation in some other type of location (see indent (a) of the new version of Regulation 411.3.3).

The risk assessment would have to be carried out in accordance with The Management of Health and Safety at Work Regulations 1999 (SI 1999 No 3242) (MHSW), which applies in England and Wales, or the corresponding Statutory Regulations in other parts of the United Kingdom. The MHSW is referred to in NOTE 3 of the new version of Regulation 411.3.3 by means of its reference to item 10 of Appendix 2 of BS 7671.

MHSW puts the responsibility for carrying out risk assessments onto (as applicable) every employer and every self-employed person. The risk assessment relates to the health and safety of employees and self-employed persons while at work, and the health and safety of other persons arising out of, or in connection with, the conduct by the employer/self-employed person or his undertaking (MHSW regulation 3 refers).

In order for the omission of RCD protection to any socket-outlet on the basis of risk assessment to be permitted by Regulation 411.3.3, the risk assessment must determine that the RCD protection is not necessary. The risk assessment must be documented and a copy of it must be attached to the Electrical Installation Certificate or (where applicable) Minor Electrical Installation Works Certificate covering the installation of the socket-outlet.

The person who prepared the risk must be prepared to justify his or her conclusion that RCD protection was not necessary, possibly in a court of law, especially if someone was killed or injured as a result of the RCD protection being omitted.

The electrical installation designer must equally be prepared to justify his or her own decision to accept the finding of the risk assessment and omit the RCD protection to the socket-outlet(s) from his or her design.


Specifically labelled or otherwise suitably identified socket-outlet

The exception in indent (b), relating to the omission of RCD protection for specific socket-outlets, is included in both the current and new versions of the regulation.

It is stressed that the exception may only be applied for a socket-outlet that has been provided for the connection of a particular item of equipment. The socket-outlet must be labelled or otherwise suitably identified so that users will be clearly informed that the socket-outlet is intended only for plugging in that particular item of equipment and for no other purpose. Unless the electrical installation designer is convinced that the socket-outlet cannot reasonably be expected to be used for other purposes, RCD protection for that socket-outlet should not be omitted.

In the vast majority of cases, it should not be necessary to omit RCD protection for a socket-outlet. For compliance with Regulation 531.2.4, a socket-outlet should be connected to an RCD that serves a sufficiently small number of other socket-outlets or items of equipment, so that any protective conductor current that may be expected in normal service will be unlikely to cause unwanted tripping of the RCD.

 

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What constitutes an escape route ?

An escape route is a route designated for escape to a place of safety in the event of an emergency.

Escape routes may include not only defined routes such as corridors, stairways and hallways, but also open areas through which escaping persons might reasonably be expected to need to pass on their way to a place of safety.

For premises covered by The Regulatory Reform (Fire Safety) Order 2005 (FSO), which applies in England and Wales, the designation of the escape routes is part of the risk assessment that the FSO requires the ‘responsible person’ to carry out and keep up to date. Similar legal requirements apply in Scotland and Northern Ireland.

 

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Fire resisting supports in escape routes

BS 7671:2011+A3:2015 (IET Wiring Regulations Seventeenth Edition), which was published in January 2015 and comes into effect on 1 July, will include a requirement that wiring systems in escape routes shall have fire-resisting supports. The requirement is included in a new regulation (Regulation 521.11.201), which is reproduced below.

521.11.201 Wiring systems in escape routes shall be supported such that they will not be liable to premature collapse in the event of fire. The requirements of Regulation 422.2.1 shall also apply, irrespective of the classification of the conditions for evacuation in an emergency.

NOTE 1: Non-metallic cable trunking or other non-metallic means of support can fail when subject to either direct flame or hot products of combustion. This may lead to wiring systems hanging across access or egress routes such that they hinder evacuation and fire fighting activities.

NOTE 2: This precludes the use of non-metallic cable clips, cable ties or trunking as the sole means of support. For example, where non-metallic trunking is used, a suitable fire-resistant means of support/retention must be provided to prevent cables falling out in the event of fire.

The term ‘ wiring system ’, which is used in the regulation, is defined in BS 7671 as ‘an assembly made up of cable or busbars and parts which secure and, if necessary, enclose the cable or busbars.’ Thus the term covers cables (and busbars) together with any containment system for them, such as conduit, trunking and cable tray.

Reason for the new regulation

The purpose of Regulation 512.11.201 is to improve the safety of firefighters and others in escape routes under fire conditions. Wiring systems that drop and hang across escape routes due to failure of a means of support in fire conditions have the potential to entangle persons. In recent years, a number of firefighters have died as a result of being entangled in this way.

 

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Application of Regulation 422.2.1

A further requirement of Regulation 521.11.201 is that the requirements of Regulation 422.2.1 shall also apply, irrespective of the classification of the conditions for evacuation in an emergency. Regulation 422.2.1 contains various provisions for safety in the event of a wiring system being affected by fire.

 

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Intent of the new regulation :icon_bs:

The intent of Regulation 421.1.201 is considered to be, as far as is reasonably practicable, to contain any fire within the enclosure or cabinet and to minimise the escape of flames.

 

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Similar switchgear assemblies

The phrase ‘similar switchgear assemblies’ in Regulation 421.1.201 means those assemblies used for the same fundamental application as a consumer unit. A consumer unit is defined in Part 2 of BS 7671:

‘Consumer unit (may also be known as a consumer control unit or electricity control unit). A particular type of distribution board comprising a type-tested co-ordinated assembly for the control and distribution of electrical energy, principally in domestic premises, incorporating manual means of double-pole isolation on the incoming circuit(s) and an assembly of one or more fuses, circuit-breakers, residual current operated devices or signalling and other devices proven during the type-test of the assembly as suitable for such use.’

An example of a similar switchgear assembly is a three phase distribution board that is intended to be operated by ordinary persons. This would have to have isolation that interrupts the three incoming line conductors and the neutral, rather than just double-pole isolation as mentioned in the above definition.

 

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O.S.G. Electrical supplies to furniture ( A1-2008:2011) & (A3- 2015) No changes

Where electrical equipment is installed within purpose-built items of furniture, such as:
cupboards
shop displays
lecterns, and supplied from a plug and socket arrangement, no specific standard exist for such installations’ .

Therefore guidance is given here which, essentially, follows the principles of BS-7671. For electrical systems in office furniture and educational furniture, BS-6396:2008 currently exists for installations which are supplied via a 13A BS-1363 plug.

The following points should be adhered to :

415.1.1.
• socket-outlets supplying items of furniture must be protected by an RCD providing additional protection at 30mA

• cables of Band I and Band II circuits to be kept apart as far as is reasonably practicable. see also 7.4.1.

• cables of Band I and Band II circuits, which are often hidden beneath the desk, should be sufficiently mechanically protected from damage caused by movement of chairs, storage of materials and the movement of feet and legs

• cable management systems or containment, such as conduit or trunking, should be installed to allow the safe routing, protection and separation of cables through the equipment

• long-term use of multi-gang extension leads should be avoided by installing a sufficient number of socket-outlets to supply the equipment to be used:
► Employers should not allow ad hoc solutions to be created by uses . See also BS-6396:2008.

• ensure that cables are sufficiently protected and cannot become trapped or damaged where desks are designed to be extended or altered to suit different activities or users .

543.2.1. 543.2.6.
There is no general requirement to ensure electrical continuity across the metallic frame of an item of furniture unless the frame has been designed to be used as a protective conductor .

Note: New to O.S.G. (A3-2015) ▼

Where luminaires are installed in display stands, one of two methods of protection against electric shock must be used :
(a) SELV or PELV .. 559.8.414.
(b) protection by a 30mA RCD .. 415.1.

 

[Richard Burns]

For Amberleaf:
Changes to model forms of certification and reporting in BS-7671:

As part of BS 7671:2008+A3:2015 (IET Wiring Regulations Seventeenth Edition), which was published on 1 January 2015 and comes into effect on 1 July 2015, some changes have been made to the model forms of certification and reporting in Appendix 6 of BS 7671. This article summarises the main changes.

Electrical Installation Certificate (A3 - 2015)

A new section has been added on the first page of the Electrical Installation Certificate for details to be recorded of any permitted exceptions to Regulation 411.3.3 (see Figure 1). This relates to where additional protection for one or more socket-outlets rated at 20A or less by an RCD has been omitted on the basis that a documented risk assessment has determined that such protection is not necessary. This exception may be used only for an installation other than in a dwelling. Where the exception is used, a copy of the risk assessment must be attached to the certificate as required by Regulation 411.3.3.

Figure 1 - New section regarding permitted exceptions


The section where details of the main protective bonding conductors of the installation are to be recorded has been expanded (see Figure 2). This now includes separate tick boxes for main bonding conductor connections to water installation pipes, gas installation pipes, oil installation pipes, structural steel, lightning protection and any other parts (as referred to in Regulation 411.3.1.2) to which such connections have been made.

Figure 2 - Changes to section for details of main bonding connections


In the notes of guidance for recipients, a change has been made to the note that points out that, for safety reasons, the installation will need to be inspected at appropriate intervals. Instead of referring to ‘a competent person’, the note now refers to ‘a skilled person competent in inspection and testing of electrical installations’. The change has been made in order to describe more clearly the qualities that should be possessed by the person chosen to carry out such periodic inspections.

A new note of guidance has also been added to tell the recipient that the certificate is valid only if accompanied by the Schedule of Inspections and the Schedule(s) of Test Results. (( P/416))