Re-take - Useful Information for 2394 :

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Reasonably-practicable or absolute

If the requirement of the regulation is absolute, then that regulation must be met regardless of cost or any other consideration.
If the regulation is to be met ‘ so far as is reasonably practicable ’ , then risks, cost, time, trouble and difficulty can be considered.

You may come across it as

( “ so far as is reasonably practicable ” )
( “ as low as reasonably practicable ” ).
is the term most often used in the Health and Safety at Work etc Act and in Regulations.

 

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The definition of “ Electrical equipment “ is very brood , including anything used or intended to be used or installed for use :

The term “ Equipment “ as the BS-7671:
Definition makes clear , relates to ( All ) equipment that will be utilized in an electrical-installation , So as to be clear as to what is included , in BS-7671: definition of “ Electrical equipment “ is repeated below :

P/27 , Electrical equipment : ( abbr: Equipment )
Any item for such purposes as generation , conversion , transmission , distribution or utilisation of electrical energy , such as machines , transformers , apparatus , measuring instruments , protective-devices , wiring-systems , accessories , appliances and luminaires .

Electric installation : ( abbr: Installation )
An assembly of associated electrical equipment having co-ordinated characteristics to fulfil specific purposes .

Fundamental requirements for selecting all “ Equipment “

It is important to note . that the selection & erection requirements of the 17[SUP]th[/SUP] Edition do not generally repeat the requirements contained within the equipment’s product Standards . Instead , BS-7671: addresses equipment solely in accordance with installation-requirements ( Regulation 113.1. )

When selecting equipment , the following must be considered :

• Compliance with the appropriate product Standard’s :
• Suitability for the anticipated operational condition’s :
• Suitability for the anticipated , External influences :
• Provides adequate accessibility for , maintenance :

( Regulation 113.1. ) Equipment :
The Regulation’s apply to items of , electrical-equipment only so far as selection & application of the Equipment in the installation are concerned , The Regulation’s do not deal with requirements for the construction of assemblies of electrical-equipment , which are required to comply with appropriate Standards .

Electrical equipment : ( abbr: Equipment ) BS-7671

 

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Testing :

The difference between a Certificate and a Report

As its title suggests, an Electrical Installation Certificate certifies that new electrical installation work complies with the current edition of BS-7671: it is not suitable for reporting on the condition of an existing installation and should not be used for that purpose.

P/392. ( EIC ) This safety Certificate has been issued to confirm that the electrical installation work to which it related has been designed , constructed ,inspected & tested in accordance with British Standard 7671 ( the IET Wiring Regulations )

( EIC )
Such certification includes a declaration that the installation work has been designed, constructed and inspected and tested in accordance with the requirements of BS-7671 it is a ( declaration that the installation is safe to be taken into service )

Similarly, an Electrical Installation Condition Report is not suitable for the initial certification of a new installation, or of new work associated with an alteration or addition to an existing installation, and so should not be used for that purpose.

On completion of the initial verification of an electrical installation, or of an alteration or addition to an installation, an Electrical Installation Certificate (EIC) or Minor Electrical Installation Works Certificate (MEIWC) should be issued ( Regulation 631.1 of BS-7671 refers ).

The certificate issued should be based upon the model form given in Appendix 6 of BS-7671 and should include a record of the inspection activities performed and the results of the testing carried out as part of the verification process.

Importantly, an EIC or MEIWC must not be issued until any defects or omissions revealed during the verification of the installation work covered by the certificate have been remedied ( Regulation 632.4 of BS 7671 refers ).

Such certification includes a declaration that the installation work has been designed, constructed and inspected and tested in accordance with the requirements of BS-7671. In short, it is a declaration that the installation is safe to be taken into service.

( EICR ) .. The report contains a summary of the overall condition of the installation in terms of whether it remains Satisfactory, or is Unsatisfactory, for continued use.

On completion of the periodic inspection and testing of an electrical installation, an Electrical Installation Condition Report ( EICR ) should be issued ( Regulation 634.1 of BS-7671 refers ). The report should be based upon the model form given in Appendix 6 of BS-7671 and should include a record of the inspection activities performed and the results of the testing carried out as part of the periodic inspection process.

The report details the outcome of an assessment of the in-service condition of an electrical installation against the requirements of the issue of BS-7671 current at the time of the inspection, irrespective of the age of the installation or to which edition of the Wiring Regulations it was designed. Details of any damage, defects, deterioration, non-compliances or dangerous conditions should be recorded on the report (Regulation 634.2 of BS-7671 refers).

Electrical :
( EIC ) .. Installation Certificate . New installation :
( EICR ) .. Installation Certificate Report .. Existing property :

 

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Protective-earthing , requires all exposed-conductive-parts to be connected to a protective conductor which in turn is connected to the main earthing terminal and hence, via the earthing conductor to the means of earthing

Main-protective-equipotential-bonding
In each installation main protective-bonding-conductors complying with Chapter 54 are required to connect to the main earthing terminal extraneous-conductive-parts, such as water & gas installation pipes, other installation pipework and ducting, central heating , air conditioning systems and exposed metallic structural parts of the building.

Automatic disconnection in case of a fault
When a fault occurs, the fault current has to be of sufficient magnitude to operate the circuit protective device to automatically disconnect the supply to the faulty circuit within a prescribed time. ... ( RCD in earth fault condition's 0.04s )

( an RCBO ) may be employed. Where an RCD is used for fault protection .

Basic protection provided by ... Insulation or barriers & enclosures
Fault protection provided by ... Protective earthing , Protective bonding , Automatic disconnection . ( ADS )

RCD : used for , Addition protection & Fault-protection

Additional protection
BS-7671 recognizes this measure as reducing the risk of electric shock in the event of failure of one or other of the two basic protective measures
( Insulation & Barriers or Enclosures ) and/or failure of the provision for fault protection or carelessness by user(s)

 

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Protective measures

A protective measure must consist of provision of basic protection & provision of fault protection, which normally are independent.
For example, in the case of automatic disconnection of supply .

Basic protection is provided by insulation & barriers and enclosures .
Fault protection is provided by protective earthing, protective bonding & automatic disconnection of supply .

Basic & fault protection are independent .

Basic protection is defined as:
P/23 : Protection against electric shock under fault-free conditions

Basic protection is provided to protect persons or livestock coming into direct contact with live parts

Protection under fault conditions or fault protection is defined as:
P/28 : Protection against electric-shock under single fault conditions

Fault protection provides protection against persons or livestock coming into contact with exposed-conductive-parts which have become live under single fault conditions

P/27 : Exposed-conductive-part is defined as:
Conductive part of equipment which can be touched and which is not normally live but which can become live under fault conditions

Basic protection & Fault protection : ... " Protection against electric-shock "
Additional-protection : ... " Protection against electric-shock "

" Protection against electric-shock "
p/51 : Note : In electrical installation's the most commonly used protective measure is ( ADS ) Automatic disconnection of supply

Fault protection is provided by :
p/32 : Protective-earthing , Earthing of a point or points in a system or in an installation or in equipment for the purposes of Safety
P/32 : Main-protective-equipotential-bonding equipotential bonding for the purpose of Safety
P/23 : Bonding-conductor A protective-conductor providing equipotential bonding . ( Equal-bonding )
Automatic disconnection of supply in the case of a fault.

P/51 : Chapter 41 : Protection against Electric Shock .
This chapter deals with protection against electric-shock as applied to electrical installations .

refer . P/51 . 2011:
in BS-7671:2001:
i) protection in use without a fault ( now designated basic protection ) was referred to as protection against direct-contact .
ii) protection under fault-conditions ( now designated fault protection ) was referred to as protection against indirect-contact .

411.3. : Requirements for fault-protection .
411.3.1. : Protective earthing & protection equipotential bonding .
411.3.1.1. : Protective earthing .

411.3.2. Automatic disconnection in case of a fault .

Protective measure : ( ADS ) 411
411.1. General
Automatic disconnection of supply is a protective measure in which :

i) Basic-protection is provided by ( Basic insulation of live-parts or by barriers or enclosures )
ii) Fault-protection is provided by protective-earthing , protective-equipotential-bonding & automatic disconnection .. in case of a fault .

 

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Dimming-equipment : can vary from simple dimmer switches, used in domestic situations, to large, multi-way dimming units

Testing

BS 7671 requires that all circuits are inspected and tested prior to being put into service; see Regulation 610.1.
The testing sequence is given in Section 612 of BS-7671 and will not be reiterated here but there are a number of points worth highlighting.

When undertaking insulation resistance testing, Table 61 shall be applied, e.g. test voltage of 500 v d.c. with a minimum insulation resistance measurement of 1 MΩ, when verifying insulation resistance between non-earthed protective conductors and Earth. Where equipment is likely to influence the verification test, or be damaged, such equipment the test voltage for the particular circuit may be reduced to 250 V d.c. but the insulation resistance shall have a value of at least 1 MΩ.

Regulation 612.3.3 recognises that where the circuit includes electronic devices which are likely to influence the results or be damaged during the test, a measurement between the live conductors connected together and the earthing arrangement only can be made.

In the event of a fault of negligible impedance, protective devices in all lighting circuits should disconnect the fault within the required time or supplementary provisions are applied to achieve the same degree of safety. The use of non-standard equipment is not a barrier to electrical installation design but the designer must ensure that the level of safety is not compromised.

The requirements of BS-7671:2008
Equipment :
Regulation 511.1 of BS-7671:2008 requires that all equipment complies with the relevant requirements of the applicable British Standard, or Harmonised Standard, appropriate to the intended use of the equipment.

Where equipment is not manufactured to a recognised standard, as highlighted , Regulation 511.2 requires that such equipment offers the same degree of safety as that afforded by compliance with the Regulations; this is also recognised in Chapter 12.

Fundamentally, the ( Regulations do not apply to electrical appliances (( but )) , as the dimming equipment is controlling outgoing circuits - that can be considered as part of the electrical installation - it would be necessary to make reference to this instance as a departure from BS-7671 in the Electrical Installation Certificate; Regulation 120.3 requires the designer to follow technical requirements intended to ensure that electrical installations conforms to the fundamental principles of Chapter 13 and states:

Any intended departure from these Parts requires special consideration by the designer of the installation and shall be noted on the Electrical Installation Certificate specified in Part 6. The resulting degree of safety of the installation shall be not less than that obtained by compliance with the Regulations

Therefore, the Regulations are not a barrier to non-standard equipment but designers must ensure the equipment used is just as safe as equipment made to recognised standards.

Regulation 515.1 requires that there be no harmful effect between electrical and other installations. The best approach, where practicable, is to arrange that the installations are kept separated. Elevated temperatures from hot running dimmer units in hot environments need to be considered and such sources of heat kept separate from susceptible parts of the building fabric or theatrical properties.

Regulation 515.2 requires that where equipment carrying current of different types or at different voltages is grouped in a common assembly (such as a switchboard, a cubicle or a control desk or box), all the equipment belonging to any one type of current or any one voltage shall be effectively segregated wherever necessary to avoid mutual detrimental influence.

 

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Regulation 621.5 states that Periodic Inspection & Testing shall be undertaken by a competent person.

Regulations apply to design, erection and verification of electrical installations, also additions and alterations to existing-installations. Existing installations that have been installed in accordance with earlier editions of the Wiring Regulations may not comply with this edition in every respect. This does not necessarily mean that they are unsafe for continued use or require upgrading.

 

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Useful Junk .

How did it all Start : !!! Number of socket-outlets

( Parker Morris Report ) How many socket do you require in a house !!!!

Firstly :
All equipment must be “ fit for purpose “ as the law demands bearing in mind the purpose to which the equipment is to be put , its use and the environmental condition in which it is to be used .
SAFETY

It has already been stated that the number of socket-outlets being advocated is primarily on the grounds of safety. The resulting dangers of not having sufficient socket-outlets may be summarised as follows:

• If there is no convenient socket at the location where the user wishes to use the appliance, he will almost certainly take steps to overcome the problem himself. This will either mean lengthening the flex or providing a ‘ do-it-yourself ’ extension to the socket. In both cases, there is a likelihood that this will not be done properly, resulting in a dangerous electrical situation often involving a loss of earthing at the point where it is required.

• If the longer flexes are provided there is a serious risk of these being stumbled over. Falls are the most common cause of accidents in the home. Such accidents are not considered ‘ electrical accidents ’. Long flexes placed under carpets, etc are equally liable to create a fire danger with continuous traffic over them and also lead to incorrect and hazardous use of mains connectors.

• With sufficient socket-outlets available adaptors may be used. ( Adaptors not designed for continuous loading of high current can overheat ) Moreover, ( several appliances connected to the same socket mean that these may be left alive even though they are not in use ) , since there is no individual controlling switch. This is an additional danger, as is the possibility of overloading.

• There are two principal dangers arising from a poor electrical installation and associated equipment. They are either the personal risk of electric shock or the damage to individuals and property through fire. So far as the electric shock is concerned, there are no specific statistics available other than those of fatalities directly attributable to an electrical cause.
PART P OF THE BUILDING REGULATIONS

From 1st January 2005 electrical installation work carried out in dwellings in England and Wales will become subject to Part P of the Building Regulations.

Part P imposes the requirement that:

“ Reasonable provision shall be made in the design, installation and testing of electrical installations in order to protect persons from fire or injury ”.

and that:

“ Sufficient information shall be provided so that persons wishing to operate, maintain or alter an electrical installation can do so with reasonable safety ”.

THESE REQUIREMENTS APPLY TO ALL ELECTRICAL INSTALLATION WORK CARRIED OUT IN DWELLINGS IN ENGLAND AND WALES. FAILURE TO MEET THESE REQUIREMENTS WILL BE A CRIMINAL OFFENCE.

In addition, as a consequence of Part P, from 1 January 2005 electrical installation work in dwellings in England and Wales will count as “ building work ” , as defined in the Building Regulations 2000, and hence should be notified to a Building Control Body before the work commences, unless:

(1) the proposed work is to be undertaken by a Competent Person (an individual or a company authorised to selfcertify compliance on completion of the work); or

(2) the proposed work is of a minor nature.
Further information regarding Part P of the Building Regulations can be found at Partp.co.uk

CONVENIENCE

If socket-outlets are not conveniently placed to the user they will not be used. Also, unless they are reasonably placed along the wall and located on several walls in the room, the danger of trailing flexes will not be removed. Thirty five percent of families move house every 5 years or less and a further 23% move house at intervals of less than 10 years *. Each family has a different arrangement of furniture and pattern of living. This point was made in the ( Parker Morris Report ) , but has seldom been taken note of. However it is common experience that in every home there is at least one socket-outlet in the living area, which is unusable due to furniture being placed in front of it, and this frequently happens in bedrooms as well.

” General Household Survey ”. HMSO

 

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( Parker Morris Report ) Recommended Minimum Quantity of Double-Socket-Outlets for Dwellings .

This is the ( ECA's ) take on it, an upgraded version of the , Parker Morris Report

How many socket do you require in a house IET Regulation

BS-7671:2008: 2011: O.S.G. P/178 . There is much in the 1961 report that still rings true today.
H7 Number of Socket-outlets .

553.1.7. Sufficient socket-outlets are required to be installed so that all equipment likely to be used can be supplied from a reasonably accessible socket-outlets , taking account of the length of flexible cable normally fitted to portable-appliances and luminaires . Table H7 provides guidance on the number of socket-outlets that are likely to meet this requirement .

( Parker Morris Report ) Table 1 – Minimum Number of Socket Outlets to be Provided in Homes

All socket-outlets should be of the ( twin-switched-type )

Room Type

Smaller Dwellings Rooms Typically ( 4 / 12m[SUP]2[/SUP] ) ...
- Main Living Room ( see note 4 ) Socket-Outlets 4
- Dining Room , Socket-Outlets 3
- Single Bedroom , Socket-Outlets 2
- Double Bedroom , Socket-Outlets 3
- Studies , Socket-Outlets 4
- Utility Rooms , Socket-Outlets 3
- Kitchens ( see note 1 ) Socket-Outlets 6
- Garage ( see note 5 ) Socket-Outlets 1
- Conservatories , Socket-Outlets 2
- Halls ( see note 4 ) Socket-Outlets 1
- Lofts , Socket-Outlets 1

Note: In accordance with BS 7671 (Regulations for Electrical Installations) all socket outlets likely to supply portable equipment used 30mA residual current device.

2011: O.S.G. Table H7 .. Minimum number of ( Twin-socket-outlets ) to be provided in homes .
Smaller rooms ( up to 12m[SUP]2[/SUP] )

- Main Living Room ( see note 4 ) Socket-Outlets 4
- Dining Room , Socket-Outlets 3
- Single Bedroom ( see note 3 ) Socket-Outlets 2
- Double Bedroom ( see note 3 ) Socket-Outlets 3
- Bedsitting room ( see note 6 ) Socket-Outlets 4
- Study Socket-Outlets 4
- Utility Rooms , Socket-Outlets 3
- Kitchens ( see note 1 ) Socket-Outlets 6
- Garage ( see note 2 ) Socket-Outlets 2
- Conservatory , Socket-Outlets 3
- Hallways , Socket-Outlets 1
- Loft , Socket-Outlets 1
- Location containing a bath or shower , ( note 5 )

 

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( Parker Morris Report ) Table 1 – Minimum Number of Socket Outlets to be Provided in Homes
Medium Dwellings Rooms Typically ( 9 / 25m[SUP]2[/SUP] )

- Main Living Room ( see note 4 ) Socket-Outlets 4
- Dining Room , Socket-Outlets 3
- Single Bedroom , Socket-Outlets 3
- Double Bedroom , Socket-Outlets 3
- Studies , Socket-Outlets 4
- Utility Rooms , Socket-Outlets 4
- Kitchens ( see note 1 ) Socket-Outlets 8
- Garage ( see note 5 ) Socket-Outlets 1
- Conservatories , Socket-Outlets 3
- Halls ( see note 4 ) Socket-Outlets 2
- Lofts , Socket-Outlets 1

Note: In accordance with BS 7671 (Regulations for Electrical Installations) all socket outlets likely to supply portable equipment used 30mA residual current device.

2011: O.S.G. Table H7 .. Minimum number of ( Twin-socket-outlets ) to be provided in homes .
Medium rooms ( up to 12 / 25m[SUP]2[/SUP] )

- Main Living Room ( see note 4 ) Socket-Outlets 6
- Dining Room , Socket-Outlets 4
- Single Bedroom ( see note 3 ) Socket-Outlets 3
- Double Bedroom ( see note 3 ) Socket-Outlets 4
- Bedsitting room ( see note 6 ) Socket-Outlets 5
- Study Socket-Outlets 5
- Utility Rooms , Socket-Outlets 4
- Kitchens ( see note 1 ) Socket-Outlets 8
- Garage ( see note 2 ) Socket-Outlets 3
- Conservatory , Socket-Outlets 4
- Hallways , Socket-Outlets 2
- Loft , Socket-Outlets 2
- Location containing a bath or shower , ( note 5 )

( Parker Morris Report ) Table 1 – Minimum Number of Socket Outlets to be Provided in Homes
Larger Dwellings Rooms Typically ( 25 / 225m[SUP]2[/SUP] )

- Main Living Room ( see note 4 ) Socket-Outlets 6
- Dining Room , Socket-Outlets 4
- Single Bedroom , Socket-Outlets 3
- Double Bedroom , Socket-Outlets 3
- Studies , Socket-Outlets 6
- Utility Rooms , Socket-Outlets 4
- Kitchens ( see note 1 ) Socket-Outlets 10
- Garage ( see note 5 ) Socket-Outlets 2
- Conservatories , Socket-Outlets 4
- Halls ( see note 4 ) Socket-Outlets 2
- Lofts , Socket-Outlets 1

Note: In accordance with BS 7671 (Regulations for Electrical Installations) all socket outlets likely to supply portable equipment used 30mA residual current device.

2011: O.S.G. Table H7 .. Minimum number of ( Twin-socket-outlets ) to be provided in homes .
Larger rooms ( more than up to 25m[SUP]2[/SUP] )

- Main Living Room ( see note 4 ) Socket-Outlets 8
- Dining Room , Socket-Outlets 5
- Single Bedroom ( see note 3 ) Socket-Outlets 4
- Double Bedroom ( see note 3 ) Socket-Outlets 5
- Bedsitting room ( see note 6 ) Socket-Outlets 6
- Study Socket-Outlets 6
- Utility Rooms , Socket-Outlets 5
- Kitchens ( see note 1 ) Socket-Outlets 10
- Garage ( see note 2 ) Socket-Outlets 4
- Conservatory , Socket-Outlets 5

 

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The Scope of BS-5839: Pt 6 .

This code of practice cover fire alarm systems starting from a simple self-contained battery-smoke-alarm right through to major systems with central panel/s in accordance to BS-5839 - pt 1 .

BS-5839: Pt 6 covers the following domestic building types .
Bungalows
Multi-storey houses
Individual flats
Individual maisonettes
Mobile homes
Individual sheltered accommodation as well as their common parts
Houses in multiple occupation ( HMOs )
Certain NHS housing in the community
Mansions
Shared houses
Houses divided into several self-contained single-family dwelling units .

Not included are hostels , caravans , boats ( Other than permanently moored ) & mmunal parts of blocks or flats or maisonettes .

Basic design guidance for most domestic installations (Grade D, Category LD3)
Where more than one alarm is provided they should be interconnected, so that detection by one unit operates the alarm signal in all of them.

Typically, a steady Green-light simply means that it is receiving AC power.

These are powered by two power sources.
Main’s power & battery power. The battery power operates the detector should the fire interrupt the house main’s .

 

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Unfortunately : there is ( No-legal-Requirement ) to carry out Periodic Inspection & Testing of premises within the UK ... ( Why the Hell - NOT )
( Why is so many Electrician’s. Unemployed ) ... Business for Sale .

 

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What types of mechanical protection provide sufficient protection against penetration by nails, screws and the like .

As an example, steel of 3 mm minimum thickness is generally considered to provide sufficient mechanical protection, except where shot-fired nails are likely to be used.

Regulation number(s) 522.6.101 , 522.6.103

 

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[h=4]Does the device that has to be provided for switching off a bathroom extract fan for mechanical maintenance need to be located adjacent to the fan[/h][h=4][/h][h=4]No, but the device does need to be so placed and marked as to be readily identifiable and convenient for the intended use[/h]Regulation number(s) 537.3.2.4 . P/152
[h=4][/h]

 

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[h=4]Does the 17th Edition permit connection of smoke alarms to an adjacent lighting circuit taking into account Regulation 560.7.1, which states that circuits of safety services shall be independent of other circuits[/h][h=4][/h]Yes. The particular requirements of BS 5839-6 take precedence over the general requirements of BS-7671
Regulation number(s) 110.1

 

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Definitions of the terms:

( CNE ) Combined neutral & earth
( DNO ) Distribution network operator
( Earth ) Capital ‘ E ’ to imply the general mass of Earth, i.e. true Earth, e.g. the ground that you walk on
( earth ) Lower-case ‘ e ’ to imply the earth of the electrical installation
( PEN ) conductor , A conductor combining the functions of both protective-conductor & neutral-conductor

 

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Short-circuit
A short-circuit is a connection between line & neutral, or between line & earth

Line & Neutral . live-conductor(s)
Circuit-protective-conductor , under earth-fault-conditions .

P/34 . Short-circuit-current
An overcurrent resulting from a fault of negligible impedance between ( Live conductors ) having a difference in potential under normal operating conditions .

 

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Four concepts

Provision of : Isolation . 537.2 . P/150
• Purpose : " Electrically skilled persons "
To enable electrical work to be carried out on .. ( Isolated circuit with safety )

Provision of : Switching OFF for mechanical maintenance . 537.3. P/151
• Purpose : " Non-electrically skilled persons "
To enable non-electrical work to be carried out on switched circuit with safety

refer : Table 53.4. P/149
Switching off for mechanical maintenance .
A Shower or Cooker switch may perform the function of switching off for mechanical maintenance .

Provision of : Emergency switching . 537.4 . P/152
• Purpose : " Anyone "
To cut off rapidly electrical energy to remove any unexpected hazard

Provision of : Functional switching . 537.5 ( BS-7671: Control ) P/153
• Purpose : Installation user
To enable proper functioning and control of current - using equipment

a switch in a socket-outlet
a switch in a lighting switch / pull-cord
a contactor switching the supply
push buttons
a thermostat
a pressure switch

The requirements for functional switching are contained in Section 537.5. & also referred to in Section 612.13. for functional testing in BS-7671:2011

Functional switching is defend in part 2 , Definitions of BS-7671: P/28
An operation intended to switch " on or off " or vary the supply of electrical energy to all or part of an installation for normal operating purposes

Functional switching is for " Normal operating purposes " & that it can be either one of two-functions .
• Switching on or off
• Varying the supply of electrical energy

Functional switching can be either Manually operated or Automatic operated Regulation 537.5.2.2.

Regulation 537.5.1.1. requires that a functional switching device be provided for each part of a circuit which may require to be controlled of other parts of the installation .

2392 / 2394 .
Functional switches do not have control all the ( Live-conductors of a circuit ) they can be single-pole-devices , such ( light switches ) Regulation 537.5.1.2. Neutral-conductors are not permitted to be switched independently of their associated line conductors .

Functional switches do have to be " appropriate " & a single device is allowed to control two or more items of equipment intended to operate simultaneously , Regulation 537.5.1.3.

Regulation 537.1.3. which requires that functional switches be " Appropriate "
functional switching devices , the operation , location & type of must be suitable for the most onerous duty they are intended to perform Regulation 537.5.2.1.

 

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Inspection & Testing

Functional switching is included among the items requiring Inspection in BS-7671:
The Schedule of inspections lists " Selection of appropriate Functional switching devices .

Functional switching is also included among the examples of items requiring inspection for an ( EICR ) The presence & condition of appropriate devices in accordance with Regulation 537.5.1.1. must be verified , Correct operation of the functional devices as required by Regulation 537.1.3. & 537.5.2.2. must also be confirmed

the ( EICR ) Inspection Schedule for domestic & similar premises , require a functional check of the manual operation of main switches ( item 4.8 ) further checks would be required on larger installations where the sample checklist in Appendix 6 of BS-7671: list Functional Switching as part of the Inspections .

BS-7671:2011: P/400 ( item 4.8 ) Condition Report Inspection Schedule for Domestic & Similar Premises with up to 100A Supply
Manual operation of circuit-breakers & RCDs to prove disconnection . 612.13.2.

Inspection & Testing of functional switching devices is not specifically included on the ( MEIWC ) Although , the Notes require " Appropriate Inspection & Testing " should always be carried out

Functional testing :
the requirement for functional testing in Regulation 612.13.1. & 612.13.2. include functional switching.
Functional testing includes ensuring that installed electrical equipment is working .

 

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P/193 . Protection by Automatic Disconnection of the supply ( Reg. 612.8 )

Where RCDs are applied also for protection against fire, the verification of the conditions for protection by automatic disconnection of the supply may be considered as satisfying the relevant requirements of Chapter 42.

612.8.1 General

a) TN system


Compliance with Regulation 411.4. shall be verified by :

1) Measurement of the earth fault loop impedance (see Regulation 612.9)
2) Verification of the characteristics and/or the effectiveness of the associated protective device. This verification shall be made:

- For overcurrent protective devices, by visual inspection (i.e. short-time or instantaneous tripping setting for circuit breakers, current rating and type for fuses)

- For RCDs, by visual inspection and test.
The effectiveness of automatic disconnection of supply by RCDs shall be verified using suitable test equipment according to BS EN 61557-6 (See Regulation 612.1) to confirm that the relevant requirements in Chapter 41 are met.

The disconnection times required by Chapter 41 shall be verified.

Compliance with Regulation 411.5. shall be verified by :

b) TT system

1) Measurement of the resistance of the earth electrode for exposed-conductive-parts of the installation (see Regulation 612.7)
2) Verification of the characteristics and/or the effectiveness of the associated protective device. This verification shall be made:

- For overcurrent protective devices, by visual inspection (i.e. short-time or instantaneous tripping setting for circuit breakers, current rating and type for fuses)

- For RCDs, by visual inspection and test.
The effectiveness of automatic disconnection of supply by RCDs shall be verified using suitable test equipment according to BS EN 61557-6 (See Regulation 612.1) to confirm that the relevant requirements in Chapter 41 are met.

The disconnection times required by Chapter 41 shall be verified.

P/193/194 . Regulation 612.8.1. & 612.10.
Residual current device , Test instrument(s)
require the use of an RCD test instrument to BS-EN-61557-6 .. (Part 6 ) to test the operation RCDs used for fault-protection & additional-protection respectively .

in Exams : 2394. this will get into Exams . ▼
GN-3 , P/58 411.4.5.
operation of residual current devices
for each of the tests , readings should be taken on both positive & negative half-cycles and the longer operating time recorded . 0º / 180º degrees

GN-3 2008 : 612.8.1. In order to test the effectiveness of residual current devices after installation , a series of tests may be applied to check that they are within specification and operative satisfactorily . This test sequence will be in addition to proving that the test button is operational .

GN-3 2008 : Facts : The effectiveness of the test button should be checked after the test sequence .
GN-3 2011: The RCD test button will only operate the RCD if it is energized

for each of the tests , reading should be taken on both positive & negative half-cycles & the longer operating time recorded .

GN-3 2011: P/58 . 2.7.18
Operating times of RCDs are required to be tested in the following circumstances :
612.8.1. Where they are relied on for disconnection for compliance with Chapter 41 .
612.10. Where they are installed as additional protection as specified in Chapter 41 .

Where RCDs are installed with circuit-breakers & the circuit has the characteristics to satisfy Chapter 41 without the RCD , then testing of the RCD is not essential unless it is specified for additional protection .

for each of the tests , reading should be taken on both positive & negative half-cycles & the longer operating time recorded .

 

[amberleaf]

Recap .

Following testing for effectiveness by instrument , RCDs are required to be operated by their integral test facility to verify functionality (Regulation 612.13.1 refers).

612.13.1 Functional testing . " Push the Button "
Where fault-protection & / or additional protection is to be provided by an RCD , the effectiveness of any test facility incorporated in the device shall be verified .

 

[amberleaf]

Recap .

Regulations RCBO . P/57
in the case the maximum-earth-fault-loop-impedance ( Zs ) is determined according to the residual current characteristic , given in BS-7671: clause 411.4.9. & table 41.5.

Non-delayed RCDs to BS-EN-61008-1 & BS-EN-61009-1 , for a nominal voltage Uo of 230V ,
In such cases , an overcurrent protective device shall provide protection against overload-current & fault-current .

The characteristic of the circuit-breaker ( B,C,D ) according to the application .. Overload , Short-circuit

O.S.G. p/23 . Overload-protection : circuit-breakers to BS-EN60898 types ( B,C,D ) &
Residual current circuit-breakers with integral overcurrent protection ( RCBOs ) to BS-EN-61009-1 .. RCD side / Earth-fault

Types of RCD

Residual current operated switching device NOT designed to perform the functions of Protection against ( Overload & or Short-circuit )
BS-EN-61008-1 RCCB : we need , Overload-protection : circuit-breakers to BS-EN60898

RCBO , being a unit with a combined circuit-breaker & RCD , will carry out functions , ( 3/1 ) Overload . Short-circuit , Earth-fault .

Circuit-breakers Note : There is no Type (A) instantaneous tripping characteristic to avoid confusion with the ( A abbreviation for amperes

Circuit-breakers ( Fig 3A4 ) Type B circuit-breakers to BS-EN-60898-1 & RCBO to BS-EN-61009-1

P/55 . The values specified in Table 41.3. for the Types & ratings of overcurrent-devices listed may be used instead of calculation .

by calculation ( B ) : 3 x 6A = 18A .. 5 x 6A = 30A
by calculation ( C ) : 5 x 6A = 30A .. 10 x 6A = 60A
by calculation ( D ) : 10 x 6A = 60A .. 20 x 6A = 120A

 

[amberleaf]

Recap .

RCDs are used to provide protection against the specific dangers that may arise in electrical installations, including:

Fault protection :
Additional protection;
Protection against Fire

An RCD is a protective device used to automatically disconnect the electrical supply when an imbalance is detected between live conductors.
In the case of a single-phase-circuit, the device monitors the difference in currents between the line & neutral-conductors.

Note that the term ‘ live ’ conductor includes both the line & neutral-conductors .. residual current .. dual current Line & Neutral

Under-Fault-free-conditions .
In a healthy circuit, where there is no fault current flowing to earth or protective conductor current, the sum of the currents in the line & neutral conductors is ( zero )

Under-fault-conditions
If a line-to-earth fault develops a portion of the line conductor current will, therefore, not return through the neutral conductor

The device monitors this difference, operates and disconnects the circuit when the residual current reaches a preset limit, the residual operating current

An RCD does not provide protection against overcurrent
Overcurrent protection is provided by a fuse or a circuit-breaker.
Combined RCD & circuit-breakers are available and are designated RCBOs.

O.S.G. p/23 3.1 Protection
Types of protective device RCBO
RCBO , being a unit with a combined circuit-breaker & RCD , will carry out functions , ( 3/1 ) Overload . Short-circuit , Earth-fault .

434 : P/83 Protection against Fault-current
This section only considers the case of a fault between conductor(s) belonging to the same circuit .

Types of RCD
RCCB :
Residual current operated circuit-breaker without integral overcurrent protection .. P/34
A residual current operated switching device NOT designed to perform the functions of Protection against ( Overload & or Short-circuit )

RCBO :
Residual current operated circuit-breaker with integral overcurrent protection .. P/34
A residual current operated switching device designed to perform the functions of Protection against ( Overload & or Short-circuit )

P/25 Circuit-breakers :
A device capable of making , carrying & breaking normal load current , Etc refer .
Appendix 1 , P/285 , BS-EN-60898:1991
Specification for circuit-breakers for overcurrent protection for household & similar installations

• BS-EN-60898 was further developed into parts 1 & 2 . BS-EN-60898-1 was first published in the UK in 2003 for A,C circuit-breakers

BS-EN-60898 specifically deals with circuit breakers intended for use by uninstructed or untrained people
Table 53.4. p/149 . further point is that BS-EN-60898-1 breakers are always suitable for isolation .

► Miniature circuit breakers conforming to ( MCBs ) manufactured to earlier standards ( such as BS-3871 ) are unlikely to be suitable for Isolation

P/24 Circuit :
A assembly of electrical equipment supplied from the same origin & protected against overcurrent by the same protective-device .

Overcurrent protective device ( OCPD )

 

[amberleaf]

Recap : Need a Sanity check !!
I always , check my Polarity on the supply side before throwing the main-switch .

GN-3 P/75 . Table 3.4 Testing to be carried out where practicable on Existing installations .
Under the heading of ( Polarity ) At the following positions ( Origin of the installation ) Etc .

Recap :
GN-3 P/47 2.7.12 Polarity testing
( Visual inspection )
Alternatively , Polarity can be verified by visually checking core colours at the terminations , thus verifying the installer's connections

Regulation P/31 . Origin of the installation
The position at which electrical energy is delivered to an electrical installation .

 

[amberleaf]

Inspection checklist :
O.S.G. P/85 .
611.3. The inspection must include at least the checking of relevant items from the following checklist :
526 ( vi ) correct connection of accessories & equipment ( including polarity )

Regulations P/189 611.3. ( vi ) Correct connection of accessories & equipment .

Regulations P/23 . Accessory :
A device , other than current-using equipment , associated with such equipment or with the wiring of an installation .

SWA . Mechanical protection .. protection against physical damage .

 

[amberleaf]

612.10. Additional protection .. Breaking in down .
the verification of the effectiveness of the measures applied by additional protection is fulfilled by visual inspection & test

Where RCDs are required for additional protection , the effectiveness of ( ADS ) by RCDs shall be verified using suitable test equipment according to BS-EN-61557-6 see Regulation 612.1. to confirm that the relevant requirements in Chapter 41 are met .

Plain English , 612.13.1. The effectiveness of RCD test facility will be verified . Etc

 

[amberleaf]

( Extracts )
Some light headed reading .

Past to Present . Has it gone pear shape .

Part P , comes into Force . 2005 : ◄
Many electrical faults are not caused by bad workmanship, so why bother with Part P ?

In the Regulatory Impact Assessment, the Government estimated that around ► 30% of electrical accidents could be prevented through regulation, and that this would justify bringing electrical work in dwellings under Building Regulations control.

Design , Installation , Inspection & Testing .

third party certification
1.28 . Unregistered installers should not themselves arrange for a third party to carry out final Inspection & Testing , The third party - not having supervised the work from the outset - would not be in a position to verify that the Installation work complied fully with BS-7671:2001 requirements , An Electrical Installation Certificate can be issued only by the installer ( responsible for the installation work )

1.29 . A third party could only sign a BS-7671:2001 . Periodic Inspection Report , or similar , The Report would indicate that electrical safety tests had been carried out on the installation which met BS-7671:2001 criteria fully with BS-7671:2001: but it could not verify that the installation complied fully with BS-7671:2001: requirements - for example with regards to routing of hidden cable .

 

[amberleaf]

Useful Junk .

Testing Continuity of ring-final-circuit conductors
Two main reasons for conducting this test :

To ensure that the ring circuit conductors are continuous , & indicate the value of ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) for the " Ring " .
To establish that interconnections in the ring-final-circuit do not exit .

Exams , by calculation .
Earth electrode / Three lead . (3)
Earth electrode résistance testing , readings obtained from an earth electrode résistance . 181Ω + 185Ω + 179Ω = 545 ÷ (3) = 181.67Ω

E1 : Three - or Four terminal type
Caution : if this is the only earth-electrode this may leave the installation unprotected against earth-faults & complete isolation of the installation must be made .

One other test not included in Part 6 of the IET Regulations but which nevertheless has to be carried out is external earth-fault-loop-impedance ( Ze )

Obtaining ( Ze ) This entails isolating the installation
By measurement : Undertaken in order to prove an earth connection
By Enquiry .. Must test to ensure Earth is present .

Exams , 2394 Wording .
External Loop Impedance ( Ze )
The value of ( Ze ) is measured at the origin of the installation on the supply side with the ( Means ) of earthing disconnected
Exams , Do Not conduct this test if the installation cannot be Isolated . " make a statement "

Testing for ( Ze , Zdb & Zs ) loop impedance .

Direct measurement of ( Zs ) can only be made on a live installation. No earthing-conductors are disconnected for the purposes of the test
( Zs ) due to the parallel earth paths present within the installation

GN-3 P/53 ( Zdb )
For larger installations with consumer units or distribution boards not at the origin , there can arise confusion over the term ( external earth loop impedance (Ze ) & some prefer to write or note the earth fault loop impedance at the distribution board as ( Zdb ) as strictly speaking , this value is not external to the installation . Thus , the formula is denoted .

 

[amberleaf]

You're reason , ( Ze ) confirms the presence of an earth connection . in a court of Law .

for our younger members

GN-3 P/52 Measurement of total earth fault loop impedance ( Zs ) using an instrument .
Measurement of ( Zs) is made on a live installation & for ( safety & practical reasons ) neither the connection with earth nor bonding-conductors are disconnected .

 

[GLENNSPARK]

You're reason , ( Ze ) confirms the presence of an earth connection . in a court of Law .

for our younger members

GN-3 P/52 Measurement of total earth fault loop impedance ( Zs ) using an instrument .
Measurement of ( Zs) is made on a live installation & for ( safety & practical reasons ) neither the connection with earth nor bonding-conductors are disconnected .

well...you want the parallel paths on Zs as its system loop.

this is the normal operating scenareo of the system..that is with earthing, bonding and any other parallel paths connected...

will also affect the PFC....which is why prospective fault current is measured with all parallel paths connected...

 

[amberleaf]

Certification :

( EICR ) Prospective fault-current ( Ipƒ ) [SUP]2 [/SUP]
( EICR ) External loop-impedance ( Ze ) [SUP]2 [/SUP]

( EIC ) Prospective fault-current ( Ipƒ ) [SUP]2 [/SUP]
( EIC ) External loop-impedance ( Ze ) [SUP]2 [/SUP]

( Note : (2) by enquiry or by measurement

By Enquiry .. Must test to ensure Earth is present .
By measurement : Undertaken in order to prove an earth connection

( Generic Schedule of Test Results ) P/402 .. Correct supply polarity confirmed □

 

[amberleaf]

Extracts .
p/400 , Domestic & Similar Installations Condition Report Inspection Schedule

Acceptable condition (✓)
Description : The condition of the particular item inspected has been classed as acceptable

Not Verified (N/V)
Description : A particular item on the schedule is relevant to the installation but has not been verified as to its condition

Limitation (LIM)
Description : A particular item on the schedule is relevant to the installation but there were certain limitations in being able to check the condition

Not Applicable (N/A)
Description : The particular item on the inspection schedule is not relevant to the installation being inspected

Unacceptable condition (C1)
Description : The condition of the particular item inspected has been classed as unacceptable. Immediate danger is present and the safety to those using the installation is at risk (e.g. a live part is directly accessible)

Unacceptable condition (C2)
Description : The condition of the particular item inspected has been classed as unacceptable. There is potential danger and the safety to those using the installation may be at risk (e.g. absence of main protective bonding)

Improvement recommended (C3)
Description : The installation is not dangerous for continued use but the inspector recommends that an improvement could be made in relation to the item inspected (e.g. no RCDs for additional protection are installed)

For the inspector included in Appendix 6 should have a statement highlighting that any older installations designed prior to BS-7671:2008 may not have been provided with RCDs for additional protection. If this is the case then the inspector should record a ( C3 ) classification code as a minimum in relation to item 5.12 of the schedule. This is to highlight that the installation could be improved in this respect.

 

[GLENNSPARK]

Certification :

( EICR ) Prospective fault-current ( Ipƒ ) [SUP]2 [/SUP]
( EICR ) External loop-impedance ( Ze ) [SUP]2 [/SUP]

( EIC ) Prospective fault-current ( Ipƒ ) [SUP]2 [/SUP]
( EIC ) External loop-impedance ( Ze ) [SUP]2 [/SUP]

( Note : (2) by enquiry or by measurement

By Enquiry .. Must test to ensure Earth is present .
By measurement : Undertaken in order to prove an earth connection

( Generic Schedule of Test Results ) P/402 .. Correct supply polarity confirmed □

except this dont...does it...

 

[amberleaf]

The measurement of ( Ze requires disconnection of parallel paths )
whilst ( PFC requires parallel paths ) & therefore these tests at the origin of the supply should be carried out separately.

Where ( Protective measures are used ) that require knowledge of the earth-fault-loop-impedance, as is the case where ( ADS ) is used , Regulation 612.9. requires the relevant impedances , to be measured or determined by an ( Alternative method ) by implication , this makes a demand for testing , Line / Earth-fault-loop-impedance . Etc .

612.9. Earth fault loop impedance ( Zs )
&
612.11. Prospective fault current . ( pƒc )

Prospective fault current ( PFC )

Like many of the modern multifunction testers on the market today, the Megger series displays the ( PFC ) at the same time as the loop test results - in the upper display.

it is important to understand that the measurement of ( PFC ) should not be recorded unless the particular requirements for the test are taken into account - in other words, the measurement of ( Ze ) requires disconnection of parallel paths )) whilst ( PFC requires parallel-paths ) therefore these tests at the origin of the supply should be carried out separately.

The value of earth-fault-loop-impedance may be determined by :

Direct-measurement of ( Zs )
Direct-measurement of ( Ze ) at the origin of the circuit & adding to this the value of ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) measurement during continuity tests :
Zs = Ze + ( R[SUP]1[/SUP] + R[SUP]2[/SUP] )

( Ze ) in order to eliminate any parallel earth return paths . The Earthing-conductor are disconnected for the duration of the test .
Will ensure that the reading is not distorted by the presence of , Gas & Water-service-pipes acting as part of the earth-return-path .

 

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Do we learn by our mistakes !!! Purpose of Initial Verification

Chief Examiners’ report , 2011 . Blast form the past .

GN-3 , 2011: P/15. refer

The lack of knowledge of the requirements of Guidance Note 3 continues to be apparent in answers given by candidates.

Few candidates were able to correctly identify the purpose on an Initial Verification process as identified in GN-3.

► Purpose of Initial Verification
Initial Verification is carried out on a new installation ( before ) it is put into service .

► The purpose of initial verification is to confirm by way of ( Inspection & Testing ) during construction & on completion , that the installation complies with the design & construction aspects of BS-7671: in so far is reasonably practicable .
610.1 , 611.2. , 612.1.

 

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BS-7671: P/36 ( Verification )
All measures by ( means ) of which compliance of the electrical installation with the relevant requirements of BS-7671: are checked , comprising Inspection , Testing , & Certification .

P/29 , Inspection
Examination of an electrical installation using all the senses as appropriate .

P/36 , Testing
Implementation of measures to assess an electrical installation by ( means ) of which its effectiveness is proved .
This includes ascertaining values by ( means ) of appropriate measuring instruments , where measured values are not detectable by ( Inspection )

 

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The Inspection & Testing of new work is known as initial verification . As the Regulation suggests .

BS-7671:2011: Regulation 621.1. States that " Where required " , periodic inspection & testing of every installation shall be carried out in accordance with Regulation 621.2. to 621.5. in order to determine , so far as is reasonably practicable , whether the installation is in a satisfactory condition for continued service .

 

[amberleaf]

Useful Junk .

Determination of 3 - phase fault current .

Highest single phase value measured = 2.28kA
( 2.25kA , 2.28kA , 2.25kA )

By calculation : 2.28 x √3 = 3.95kA
An approximation can be done as ( 2 x ) the reading .. 2 x 2.28 = 4.5kA

 

[SirKit Breaker]

Useful Junk .

Determination of 3 - phase fault current .

Highest single phase value measured = 2.28kA
( 2.25kA , 2.28kA , 2.25kA )

By calculation : 2.28 x √3 = 3.95kA
An approximation can be done as ( 2 x ) the reading .. 2 x 2.28 = 4.5kA

True enough, but for the exam keep it simple and double the highest single phase reading as it errs on the side of caution.

Cheers...........Howard

 

[Knobhead]

This really should be back as a sticky.