Re-take - Useful Information for 2394 :

[amberleaf]

O.S.G. Electrical supplies to Furniture :book:

My point .

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 .

 

[amberleaf]

3.1. O.S.G. Protective device - 2008 & 2011. ◄ Passed tense
The consumer unit ( or distribution board ) contains devices for the protection of distribution circuits and final circuit against:

i) overload
ii) short-circuit
iii) earth fault ........... Etc

Functions i and ii are carried out usually by one device, i.e. a fuse or circuit-breaker.
Function iii may be carried out by the fuse or circuit-breaker provided for functions i and ii or by an RCD

An RCBO, being a unit with a combined circuit-breaker and RCD, will carry out functions i, ii, and iii .

Things has changed . (A3) 2015 . ▼ :book:

3.1. O.S.G. Protective device
The consumer unit ( or distribution board ) contains devices providing:

(a) Overload protection ✓
(b) Short-circuit protection ✓
(c) Fault current protection ✓
(d) Additional protection: RCD(s) ✓

Functions a, b, and c, are usually carried out by one device, i.e. a fuse or circuit-breaker.
An RCBO, being a unit with a combined circuit-breaker and RCD, will carry out functions a, b, c, and d .

 

[amberleaf]

Learning curve only .

GN-3 . 2008: ◄ :book:

4) rule of thumb figures .
As a rule of thumb, the measured value of earth fault loop impedance for each circuit at the most remote outlet should not exceed 0.8 of the relevant value in the BS-7671 tables. This takes into account the increase of résistance of the conductors with the increase of temperature due to load current and errs on the side of safety .

Another method is to use the rule of thumb as described in Appendix 4 of BS-7671:2011: ◄

Circuit has a measured Zs of 0.51Ω
BS-EN-60898-1 circuit-breaker . Type C 32A
Table 41.3 . maximum permissible Zs for the circuit is 0.72Ω

multiply the maximum permitted value by ( 0.8 ) 0.72 x 0.8 = 0.57Ω ( This now becomes the maximum permissible value ))

Question is . Higher or lower .

As the measured value is less than . ?? will the circuit be acceptable .

BS-7671:2015 ◄
Using a factor of 0.8
Table 41.3 . maximum permissible Zs for the circuit is 0.68Ω
BS-EN-60898-1 circuit-breaker . Type C 32A

 

[amberleaf]

Learning curve only . (( Look at the dates ))

Q ) When taking impedance measurement at ambient temperature a rule-of-thumb correction factor may be applied to the values in BS-7671: to take into account the increased résistance of the conductors due to load current is ?

0.75
0.8
0.5
1.2

GN-3 BS-7671 Amd 1 2002. ◄ Past tense :book:


4) Rule of Thumb figures ( 0.75 )
As a rule of thumb, the measured value of earth fault loop impedance for each circuit at the most remote outlet should not exceed three-quarters of the relevant value in the BS-7671 tables. The three-quarters figure allows for a reduced cross-section protective conductor and errs on the side of safety.

GN-3 . ◄ :book:
2008:
2011:
2015:

4) rule of thumb figures (0.8)
As a rule of thumb, the measured value of earth fault loop impedance for each circuit at the most remote outlet should not exceed 0.8 of the relevant value in the BS-7671 tables. This takes into account the increase of résistance of the conductors with the increase of temperature due to load current and errs on the side of safety .

 

[amberleaf]

411.8.1.3. Requirement for fault protection . :icon_bs:
Extracts : 2015
Where a circuit-breaker is used, the maximum value of earth fault loop impedance (Zs) shall be determined by the formula in Regulation 411.4.5.

Alternatively, the value specified in Table 41.6. may be used instead of calculation for the nominal voltages (Uo) and the types and ratings of overcurrent devices listed therein .

Reduced low voltage system(s) :icon_bs:

Table 41.6.
Maximum earth fault loop impedance (Zs) for 5s disconnection time and Uo of 55V (single-phase) and 63.5V (three-phase)
see Regulations 411.8.2. and 411.8.3.

BS-EN-61558-1:2005+A1:2009
411.8.4.1. (i)
717.411.6.2. (ii)
717.413.

BS-EN-61558-2-23. Particular requirements for transformers for construction sites.
411.8.4.1 (i)

Voltage of 65V to earth, three-phase.
55V to earth , single-phase will give protection against severe electric shock .

They therefore recommended that portable tools used on construction sites . etc 110V centre-tapped transformer .

What’s new . (A3) - 2015 .

Note 1: The circuit loop impedance's have been determined using a value for factor Cmin of 0.95.
Note 2: The circuit loop impedance's given in the table should not be exceeded when:
(i) the line conductors are at the appropriate maximum permitted operating temperature, as given in Table 52.1. and
(ii) the circuit protective conductors are at the appropriate assumed initial temperature, as given in Table 54.2. to 54.5.

if the conductors are at a different temperature when tested, the reading should be adjusted accordingly, see Appendix 14.

Note 3 : Where the line conductor insulation is of a type for which Table 52.1. gives a maximum permitted operating temperature exceeding 70°C, such as thermosetting, but the conductor has been sixed in accordance with Regulation 512.1.5:
(i) the maximum permitted operating temperature for the purpose of Note 2 (i) is 70°C and
(ii) the assumed initial temperature for the purpose of Note 2 (i) is that given in Tables 54.2. to 54.4. corresponding to an insulation material of 70°C thermoplastic.

Note 4 : Data for fuses of rating exceeding 200A should be obtained from the manufacture.

 

[amberleaf]

RVS .

in the Eyes , H&S Executive accepts that a voltage of 63.5V to earth three-phase
55V to earth , single-phase . will give protection against severe electric shock .

PS. don’t be complacent here in Exams . by calculation !! . rule out nothing from City & Guilds :30:

Alternatively, the value specified in Table 41.6. may be used instead of calculation for the nominal voltages (Uo) and the types and ratings of overcurrent devices listed therein .

 

[amberleaf]

(A3) P/35 . Short-circuit current . :icon_bs:
An overcurrent resulting from a fault of negligible impedance between live-conductor(s) having a difference in potential under normal operating conditions .

Not in Definitions .

Short circuit(s)
A short-circuit is the current that will flow when a “ dead short ” occurs between live-conductors ( Line to neutral ) for single-phase
Line to line for three-phase .

(PSCC) Prospective short circuit current is the same , but the term is usually used to signify the value of short-circuit at , Fuse , Circuit-breaker positions .

You’re reason is ; Fuses and circuit-breakers . (( protecting the circuit conductors from damage ))

The meaning of the word “ Protection ” as used in Regulations & GN-3 in the electrical industry , is no different to that in everyday use . People protect themselves .

Protection against mechanical damage .

The word “ Mechanical ” is somewhat misleading in that most of us associate it with machinery of some sort .
in fact a electrical overcurrent left uninterrupted for too long can cause distortion of conductors and degradation of insulation . both of these effects are considered to be “ Mechanical damage ”

re-cap . The Regulations tell us . Let us start by considering the (( ways )) of preventing “ Mechanical damage ” caused by physical impact and the like . Etc

 

[amberleaf]

A bathroom is “ an at risk ' location ”

Protective Measure: Electrical separation .
413.3.6. & 418.3.

This method relies on a supply from a safety source such as an isolating transformer to BS-EN-61558.

BS-EN-61558-2-5:2010. Particular requirements for shaver transformers and shaver supply units .

The two main principles underlying protection by electrical-separation is that neither the source of the supply nor any live parts of the separated circuit is connected to any other circuit or to Earth.

Thus, in the event of a single fault to an exposed-conductive-part of equipment in the separated circuit, fault protection is afforded because there is no path for fault current to return to the source. For an installation in a dwelling, the only likely application of the use of electrical separation is a shaver supply unit complying with BS EN 61558-2-5.

This protective measure is limited to the supply of one item of current-using equipment supplied from one unearthed source with simple separation. The source of supply is an isolating transformer conforming to BS-EN-61558.

An example of electrical separation is a shaver supply unit.
because the secondary side of the transformer (which supplies the shaver) is isolated from the mains; in Theory only ; “ think of the shaver being supplied by a big battery ” !

Electrical separation . :icon_bs:
This method relies on a supply from a safety source such as an isolating transformer to BS-EN-61558-2-5 which has no earth connection on the secondary side. In the event of a circuit that is supplied from such a source developing a live fault to an exposed-conductive-part , there would be no path for shock current to flow .

BS-EN-61558-2-5:2010.
Sec 701
533.1.5.(ii)
701.512.2
701.515.3.(ii)
701.512.3 Appx 6
Cond. Report item 6.3.....

6.3. Shaver sockets comply with BS-EN-61558-2-5 formerly BS-3535 ( 701.512.3 .

413.3.6 . refer
No exposed-conductive-parts of the separated circuit shall be connected either to the protective conductor or exposed-conductive-parts of other circuit, or to Earth .

Note: if the exposed-conducive-parts of the separated circuit are liable to come into contact, either intentionally or fortuitously, with the exposed-conductive-parts of other circuits, protection against electric shock no longer ((depends solely on protection with )) electrical separation but also on the protective provisions to which the latter exposed-conducive-parts are subject.

418.3.
Electrical separation for the supply to more than one item of current-using equipment .

Where the measure is used to supply two or more items of equipment from a single source, a warning notice complying with Regulation 514.13.2. shall be fixed in a prominent position adjacent to every point of access to the location concerned .

Note: Electrical separation of an individual circuit is intended to prevent shock currents through contact with exposed-conducive-parts that may be energized by a fault in the basic insulation of the circuit .

 

[amberleaf]

Introduction to the first amendment ; Deleted by BS-7671:2008: Amendment 3 .
Introduction to the second amendment ; Deleted by BS-7671:2008: Amendment 3 .

P/4 . Introduction to BS-7671:2008(2015) :icon_bs:

The Regulations apply to the :
- Design
- Erection
- Verification of electrical installations
- Additions and alterations to ((Existing installations))

((Existing installations)) that have been installed in accordance with earlier editions of the Regulations may Not comply with this edition in every respect .

:13: This does Not necessarily mean that they are unsafe for continued use or require upgrading . :deal:

 

[amberleaf]

530.3.4 - Pass tense ............. BS-7671:2008: (2011) :icon_bs: ( PS look at the dates )
For an installation with a 230V single-phase supply rated up to 100 A that is under the control of ordinary persons, switchgear and controlgear assemblies shall either comply with BS-EN-60439-3 and Regulation 432.1 or be a consumer unit incorporating components and protective devices specified by the manufacturer complying with BS-EN-60439-3 including the conditional short-circuit test described in Annex ZA of BS-EN-60439-3 the standard.

► BS-EN-60439-3:1991 .. Pass tense
Particular requirements for low-voltage switchgear and controlgear assemblies intended to be installed in places where unskilled person have access to their use . Distribution boards .

( A3 - 2015) Regulation 530.3.4. (( changes have been made )) :icon_bs:

530.3.4 For an installation with a 230V single-phase supply rated up to 100A that is under the control of ordinary persons, switchgear and controlgear assemblies shall either comply with BS-EN-61439-3 and Regulation 432.1 or be a consumer unit incorporating components and protective devices specified by the manufacturer complying with BS-EN-61439-3, including the conditional short-circuit test described in Annex ZB of BS-EN-61439-3 the standard.

BS-EN-61439-3:2012: CCUs
Low-voltage switchgear and controlgear assemblies Distribution boards intended to be operated by ordinary persons ( DBO)

Intro to Amd 3
421.1.201.
530.3.4.

P/40 . D.N.O. Distribution network operator
560.6.9 Note 1 .

Note 1 : The parallel operation of a private source with the public supply network is subject to authorization by the distribution network operator (DNO) This may require special devices, for example to prevent reverse power. Refer also to Section 551, the DCode (Distribution Code of licensed distribution operators ) and ENA Engineering Recommendations G83/2 and G59/3.

 

[amberleaf]

Chapter 61
Initial Verification :icon_bs: 2015

610.1. Every installation shall, [during erection] and [on completion] [before being put into service] be inspected and tested to verify, so far as is reasonably practicable, that the requirements of the Regulations have been met .

You’re Q - New installation

Q) List the Three-stages in a new installation when inspection and testing should be carried out .
i) during erection.
ii) on completion . and
iii) before being put into service .

 

[amberleaf]

Something I knocked up .

-&-s are looking for ; Principle and responsibilities .

Q) Technical knowledge , practical skills, experience of the type of installation to be inspected and to employ adequate testing equipment are the factors that determine the competence of the test engineer.

i) BS-7671:2008:2015; .. non-statutory
ii) Guidance Note 3 .. non-statutory
iii) GS-38 .. non-statutory . PS read the questions carefully . -&-s . C&Gs will trip you up .

Identify and state the legal status of Two publications that the test engineer will have to comply with when carrying out the inspection and testing process .
1) Health and Safety at Work (etc) Act 1974 .. Statutory
2) Electricity at Work Regulations 1989 .. Statutory

Please read carefully ;
2394. Comments .
Abbreviations such as EWR and HSWA are acceptable. Candidates must correctly identify whether these are ACT or REGULATIONSs in order to achieve the marks .

The candidate could have offered other health and safety regulations or reference to the Health and Safety at Work Act as a possible answer .
The particular document must relate to the process of inspection and must be a stator document .

Duty holder , to ensure that electrical systems used at work under their control are safe . (( You have a duty of care , responsibilities ))

Q) State the title given in law to the inspector whilst carrying out the inspection of an electrical installation.
The Electricity at Work Regulations and the term “ Dutyholder ” refers to anyone having a duty of care to others .

Q) Identify the British Standard for electrical test instruments that are to be used by the test engineer to obtain measurement values on circuit within an installation .

BS-EN-61557 .. Electrical safety in low-voltage distribution systems up to 1000V a.c. and 1500 d.c. Equipment for testing, measuring or monitoring of protective measures . General requirements .

 

[amberleaf]

Refraction ) The particular document must relate to the process of inspection and must be a statutory document .

 

[amberleaf]

Something I knocked up .

PS read the wording in the questions carefully . C&Gs will trip you up

Making you aware off .

An attic extension is to be carried out in a domestic installation .
The lights are to be taken from the first floor lighting circuit and a new radial circuit consisting of 6 double sockets is to be installed.

( existing )
( new )

Q) Identify four documents that needs to be completed and given to the client .

Electrical Installation Certificate .. PS accompanied by ??? What

Schedule of Inspection ( for new installation work only )
Generic Schedule of Test Result .............. (( Wording used in Regulations & GN-3 ))
Minor Electrical Installation Work Certificate .............. (( for the additional lighting points ))

P/416 . Electrical Installation Certificate
The Electrical Installation Certificate is to be used only for the initial certification of an new installation or for an addition or alteration to an existing installation where new circuits have been introduced .

P/418 . Minor Electrical Installation Work Certificate
The Minor Electrical Installation Work Certificate is intended to be used for additions and alterations to an installation that do not extend to the provision of a new circuit .

Examples . include the :
- addition of socket-outlets
- lighting points to an existing circuit
- the relocation of a light switch etc .

This Certificate may also be used for the replacement of equipment such as accessories or luminaires .

 

[amberleaf]

Chapter 41 . Protection against Electric Shock .
410 Introduction
This chapter with protection against electric shock as applied to electrical installations .

I will put the question in a way; (Four)
How many “ protective measures ” against electric shock are allowed by the wiring regulations BS-2008:2015:

learning curve .

P/53 . 410.3.3. :icon_bs:
In each part of an installation one or more protective measures shall be applied, taking account of the conditions of external influence .
The following protective measures generally are permitted:
(i) Automatic disconnection of supply (Section 411)
(ii) Double or reinforced insulation (Section 412)
(iii) Electrical separation for the supply to one item of current-using equipment (Section 413)
(iv) Extra-low voltage (SELV) and (PELV) (Section 414)

The protective measures applied in the installation shall be considered in the selection and erection of equipment.
For particular installations see Regulations 410.3.4. to 9

Note: In electrical installations the most commonly used protective measure is automatic disconnection of supply .

 

[amberleaf]

(A3) P/424. Electrical Installation Condition Report

Condition Report :icon_bs:

Amendment 3 will make a small number of changes to the electrical installation condition report and associated notes, including a requirement to carry out an inspection within an accessible roof space where electrical equipment is present in that roof space.

Section D, Extent and Limitations of Inspection and Testing .

The inspection and testing detailed in this report and accompanying schedule have been carried out in accordance with BS-7671:2008 (IET Wiring Regulations ) as amended to ........................................................................

It should be noted that cables concealed within trunking and conduits, under floors, in roof spaces, and generally within the fabric of the building or underground. have not been inspected unless specifically agreed between the client and inspector prior to the inspection . An inspection should be made within an accessible roof space housing other electrical equipment .

 

[amberleaf]

(A3) Section 714 Outdoor Lighting Installations . :icon_bs:

In 2008 some major changes to the requirements for outdoor lighting installations were introduced, covering requirements for:

• car parks;
• gardens;
• parks;
• places open to the public;
• illumination of monuments; and
• floodlighting.

These will be retained in Amendment 3, along with the recommendations for additional protection by a 30mA RCD for telephone kiosks, bus shelters, advertising panels and town plans.

Amendment 3 will make only minor changes to outdoor lighting installations. One important change will be that individual circuits will be required to be isolated.

Extracts .

714.537. Isolation & switching .
714.537.2. Isolation
714.537.2.1. General

714.537.2.1.1. Every circuit shall be capable of being isolated individually from each of the live supply conductors , except as detailed in Regulation 537.1.2.

714.537.2.1.201.
Where it is intended that isolation and switching is carried out only by instructed persons and subject to suitable provisions being made so that precautions can be taken to prevent any equipment from being inadvertently or unintentionally energized, for TN systems, the means of switching the supply ( On-load ) and the means of isolation is permitted to be provided by a suitably ( rated fuse-carrier )

 

[amberleaf]

RP/308 . BS-EN-60898
Connecting devices for low-voltage circuits for household and similar purposes.

BS-EN-61009-1:2004+13:2012.
Electrical accessories.
Residual current operated circuit-breakers with integral overcurrent protection for household and similar uses (RCBOs)
Table 41.3.
411.4.9.

(( Point to remember )) ▼ :icon_bs:

BS-7671:2008:2015: Only provides us with information, which is relevant to equipment which we could purchase and fit at the time it was published
Therefore, the regulations only deal with BS-EN-60898 circuit-breaker(s) and BS-EN-61009-1 RCBOs

BS-EN-60898 is the most onerous Standard written for the manufacturing and testing of circuit breakers.

By definition its title ‘Specification for circuit breakers for overcurrent protection for household and similar installations’, implies that the circuit breaker will be generally used on final circuits. The scope of the Standard states that the circuit breakers are designed for use by uninstructed people and are not designed to be maintained. This is further emphasised by the many tests required to ensure the safety of the person who will return the circuit breaker to service. It does not mean that this Standard only refers to circuit breakers in domestic situations. All buildings have final circuits, and in many instances the first person attempting to reset a circuit breaker could be classed as uninstructed. The Standard recognises this by including the words ‘ and similar installations’ in its title.

Part 2 of BS-7671:2015: defines an instructed person (electrically) as ‘ a person adequately advised or supervised by skilled persons (as defined) to enable that person to perceive risks and to avoid hazards which electricity can create

 

[amberleaf]

Electrical Glossary . :svengo:

Crimp: a permanent, solderless connection between wires achieved by compression in the conductive tubing of the crimp connection or terminal
Dolly: type of switch in the form of a typically vertically aligned lever . see toggle .
Installation method : immediate environmental context within which a length of wire / cable is installed .
Luminaire: French word for lamp or light commonly used by electricians .
mA) milliamp, 1 / 1000 of an amp .

Raggles: Scottish term for chasing . PS, am raggling out the wall .

 

[amberleaf]

(A3) GN-3. Requirements for inspection and testing .

Extracts
it is important that the competency of the skilled person carrying out the periodic inspection and test is of the appropriate level, having gained sufficient education, training or practical skills, and knowledge to be fully conversant with the aspects required of carrying out such an important inspection .

The Inspector

BS-7671:20082015) has to State the facts . :icon_bs:
requires that the inspection and testing shall be carried out by a Skilled persons, competent .

with regards to verification he/she must have .

Sufficient technical knowledge
( i.e. fully versed in the inspection and testing requirements contained in BS-7671:2015)

relevant practical skills .
( i.e. have sufficient practical skills to carry out the inspection and test procedures outlined in Guidance Note 3 ) :book:

appropriate testing equipment .
Instruments used in the testing process ( where the values are to be recorded in the generic schedule of test results ) must comply with the appropriate parts of BS-EN-61557 . :deal:

P/35. Skilled person (electrically) Person who possesses, as appropriate to the nature of the electrical work to be undertaken, adequate education, training and practical skills, who is able to perceive risks and avoid hazards which electricity can create.

Note1 : The term “(electrically)” is assumed to be present where the term “ skilled person ” is used throughout BS-7671.

O.S.G. This book is the side companion to the Wiring Regulations