Re-take - Useful Information for 2394 :

[amberleaf]

Based on Learning curve only .

Ambient temperature multipliers :book:
O.S.G. Expected ambient temperature (°C) & Multiplier values to Table 11
GN-3 . Expected ambient temperature (°C) (α) to table B1

As divider values GN-3 . table B2 . 0°C to 40°C
As divider values O.S.G. table 12 . 5°C , 10°C , 15°C , 20°C , 25°C .

This is because the table is intended to be used to calculate the résistance value of a conductor when you know the temperature that it is going to operate at.

In your case here , you are going to measure the temperature of the room, and calculate the résistance of the cable back to what it would be at 20°C.
Ambient temperature multipliers to be applied to R[SUP]1[/SUP] + R[SUP]2 [/SUP]values are shown in O.S.G. table 12

Example . You have measured an R[SUP]1[/SUP] + R[SUP]2 [/SUP]value of 0.84Ω
measured ambient temperature at 25°C .. R[SUP]1[/SUP] + R[SUP]2 [/SUP] ----- temp factor = the value of résistance at 20°C .

O.S.G. Table 12 @ 25°C - 1.02 (Cƒ*)
0.84Ω ÷ 1.02 = 0.82Ω résistance of the cable at 20°C

Having corrected the measured value to what it would be at 20°C the next step is to calculate what the résistance of the cable would be at its operating temperature .

O.S.G. table 13 .
Multipliers to be applied to table 11 to calculate conductor résistance at maximum operating temperature .
This is where you use the (1.2) multiplier
The résistance of the cable at its maximum operating temperature of 70°C .. 0.82 x (1.2) = 0.98Ω

This value can now be added to the measured Ze to provide a value of Zs , Which can be compared directly to the maximum Zs values provided in Chapter 41 of BS-7671: :icon_bs:

 

[amberleaf]

Useful junk .

The “ Add up method ”
When the fifteen-edition of the regulations appeared in 1981. :book:

It carried a lot of ((New & Controversial thinking)) One of the equations that appeared

Zs = Ze + ( R[SUP]1[/SUP] + R[SUP]2[/SUP] )

In theory : BS-7671 is a design book . ( Regulation’s ) Earth fault loop impedance is given by: Zs = Ze + ( R[SUP]1[/SUP] + R[SUP]2[/SUP] )

 

[Richard Burns]

For Amberleaf:
Learning curve
Resistances in parallel


These are resistances joined like the rungs of a ladder. Here the total resistance decreases the more resistances there are. The overall resistance of two or more conductors will also decrease if they are connected in parallel


The insulation between conductors is in fact countless millions of very high value resistances in parallel.
Hence an increase in cable length results in a decrease in insulation resistance. This value is measured in millions of ohms, i.e. megohms (MΩ).


The total resistance will be half of either one and would be the same as the resistance of a 2.0mm2 conductor. Hence resistance decreases if the conductor’s cross sectional area increases.


1 / R total = 1/R1 + 1/R2 + 1/R3 + 1/R4 . ( 1/R total 1/3 + 1/6 + 1/8 + 1/2 )




R1 ÷ 3 = 0.333333333 . R1 ÷ 6 = 0.166666666 . R1 ÷ 8 = 0.125 . R1 ÷ 2 = 0.5 . ( total = 1 ÷ 1.125 ) .. R total = 0.89 , round up.

 

[amberleaf]

To describe why the requirement for equipotential bonding is so important.

What is earth and why and how we connect to it ?

The thin layer of material which covers our planet - rock, clay, chalk or whatever - is what we in the world of electricity refer to as earth. So, why do we need to connect anything to it? After all, it is not as if earth is a good conductor.

The simple answer is, in our case, the definition of Earth, i.e. the conductive mass of earth, whose electric potential at any point is conventionally defined as zero (0 V).

This allows us to assign a standard reference for a potential difference. This is exactly what it says it is: a difference in potential (volts). In this way, two conductors having PDs of, say, 20V and 26V have a PD between them of 26 - 20 = 6V
The original PDs (i.e. 20V and 26V) are the PDs between 20V and 0V and 26V and 0V. This 0V or zero potential comes from Earth.

Thus, if we connect a T5-1000 electrical tester between a live part (e.g. the line conductor of a socket outlet) and earth, we will read 230V; the conductor is at 230V and the earth at zero. The earth provides a path to complete the circuit.

If the person were touching a faulty appliance (at 230V) and a gas or water pipe (at 0V) under fault condition’s there would be a potential difference (230V) that would lead to an electric shock.

One method of providing some measure of protection against these effects is to join together (equipotential bonding) all metallic parts that are at earth potential and connect them to the electrical point of earthing (main earth terminal).

Equipotential bonding: :13:
Electrical connection maintaining various exposed-conductive-parts & extraneous-conductive-parts at substantially the same potential.

This ensures that all metalwork in a installation is at or near 0V and, during a fault, all metalwork and the earthing of the installation will rise to a similar potential.

The intent is to ensure that the difference in potential between parts is less than 50V (the “safe” touch voltage, Ut).
So, simultaneous contact with two such metal parts would not result in a dangerous shock, as there would be no significant potential difference (PD) between them.

In summary, connecting metalwork to the installation earthing (bonding) means that during fault conditions it places all parts of the installation at a similar potential (equipotential).

Add to this, a low-resistance earth fault return path, which will enable the circuit protection to operate very fast (automatic disconnection of supply), and we have significantly reduced the risk of electric shock.

 

[amberleaf]

Safe Isolation is required ..................... lock off .

learning curve .

Main protective-bonding-conductor ... ( Gas service pipe )
Wander lead ( R[SUP]2[/SUP]) GN-3 tells us , must be below 0.05Ω

You are measuring something very low . ( in Ω )

4.3. Low résistance ohmmeters .
GN-3 tells us .
Instrument
(must be accurate) The measuring range should cover the span 0.02Ω to 2Ω ..

Wander lead used . 50m (( null out the leads )) one end into your Megger & the other onto the disconnected earthing-conductor

A good way of measuring it , ( Length ) 10mm[SUP]2 [/SUP]main protective conductor up to 25m would be ok . ( you should get a low reading )

This is bonding the Gas service pipe .
One end of test probe onto the disconnected earth-conductor . Green lead with crocodile clip
At gas meter :- to carry out the final check , to measure the resistance of the protective-bonding-conductor

Other lead from your Megger ( Red ) onto the Gas pipe .
this tell you that the BS-951 earth clamp is satisfactory and the clamp is secure and in good condition ( reading of 0.02 ) lower than 0.05Ω

if there was dirt or corrosion on the pipe , the résistance will be high .

 

[amberleaf]

Could calculations be used in Exams . Q/As 2394 / 2395

Still in use . by GN-3 . :book:

Rule of thumb 2008 . 2.7.14.
Rule of thumb 2011 . 2.7.15.
Rule of thumb 2015 . 2.7.16.

 

[amberleaf]

O.S.G.
A3 2015 . Guidance on initial testing of Installations . :book:

10.1. Safety and equipment
HSR 25 . EWR regulation 14 .
Electrical testing involves danger , The Electricity at Work Regulations 1989 .

State that :
a) it is unreasonable in all the circumstances for it to be dead ;
b) reasonable in all the circumstances for the work to be carried out ; and
c) that suitable precautions are taken to prevent injury .

Although live testing and diagnosis for fault finding may be justifiable, there could be no justification for any subsequent repair work to be carried out live.

612.1. 610.1. it is the test operative’s duty to ensure their own safety, and the safety of others, whilst working through test procedures. When using test instruments, this is best achieved by precautions such as .

2011: i , ii , ii , iv .
2015: a , b , c , d .

 

[amberleaf]

O.S.G.
A3 2015 :book:

Regulation 120.3.
1.4. Departures from BS-7671:2015

Where the designer decides to depart from BS-7671: the resulting degree of safety must not be less than that obtained by compliance with the Regulations. The designer is responsible for the safety of the design. Any intended departures from BS-7671: although the designer is confident regarding safety, must be recorded on the Electrcal Installation Certificate, There is a difference between an intended departure and a non-compliance .

 

[amberleaf]

(( Risk assessment is Electrical safety ))

Regulation .. A3 2015. P/417
( MEIWC ) Minor Electrical Installation Work Certificate

Part 1: Description of minor works
(1)
(2)
(3)
(4) Details of departures, if any, from BS-7671:2008 as amended
(5) Details of permitted exceptions ( Regulation 411.3.3. ) ........... Where applicable, a suitable risk assessment(s) must be attached to this Certificate .

Risk assessment attached [ ✓ ]

411.3.3. Additional protection . refer . :book: :icon_bs:

Part 3 : Essential Tests
RCD operation ( if applicable ) Rated residual operating current ( IΔn ) ...... mA
Disconnection time at IΔn ...... mS
Disconnection time at 5 IΔn ...... mS

Satisfactory test button operation ...... ( insert ✓ to indicate operation is satisfactory )

 

[amberleaf]

Regulation .. A3 2015.
( MEIWC ) Minor Electrical Installation Work Certificate :icon_bs:

(4) Details of departures, if any, from BS-7671:2008 as amended
Non departures are to be expected except in most unusual circumstances, see regulations 120.3 and 133.5.

(5) Details of permitted exceptions ( Regulation 411.3.3. ) ........... Where applicable, a suitable risk assessment(s) must be attached to this Certificate .

In non-domestic installations where a risk assessment has been carried out and the findings show that additional protection by RCD is not necessary, the assessment(s) must be attached to this Certificate .

 

[amberleaf]

Regulation .. A3 / 2015 :icon_bs:

Abbreviations used in the Standard ▼
P/41 ► IP International Protection Code .. 412.2.2.3.

Regulation 412.2.2.3.
Where a lid or door in an insulating enclosure can be opened without the use of a tool or key, all conductive-parts which are accessible if the lid or door is open shall be behind an insulating barrier ( providing a degree of protection not less than IPXXB or IPX2 ) preventing persons from coming unintentionally into contact with those conductive-parts, This insulating barrier shall be removable only by the use of a tool or key .

 

[amberleaf]

Abbreviations used in the Standard ▼ :icon_bs:
P/41 ► PE Protective conductor , meaning - Fig 3.8

TN- systems .. Fig 3.8
All exposed-conductive-parts of an installation are connected to this ( Protective-conductor ) via the main earthing terminal of the installation .

TN-C-S ( PME) system
All exposed-conductive-parts of an installation are connected to the (PEN) conductor via the main earthing terminal and the neutral terminal , (( these terminals being linked together ))

TT system
All exposed-conductive-parts of an installation are connected to earth electrode which is (( electrically independent )) of the source earth .

A3 / 2015

P/37 . re-cap 1,2,3,4, . Protective-conductor(s)
1) circuit protective conductor
2) main protective bonding conductor
3) earthing conductor
4) supplementary protective bonding conductor(s) .. Where required .

 

[amberleaf]

A3 - P/153
537 Isolation and Switching tables .

53.4 - Guidance on the selection of protective, isolation and switching devices
Device
Standard
Isolation (4)
Emergency switching (2)
Functional switching (5)

Yes = Function provided, No = Function not provided

(1) Function provided if the device is suitable and marked with the symbol for isolation (see BS EN IEC 60617 identity number S00288).
(2) See Regulation 537.4.2.5
(3) Device is suitable for on-load isolation, i.e. disconnection whilst carrying load current.
(4) In an installation forming part of a TT or IT system, isolation requires disconnection of all the live conductors. See Regulation 537.2.2.1.

(5) Circuit-breakers and RCDs are primarily circuit-protective devices and, as such, they are not intended for frequent load switching.
Infrequent switching of circuit-breakers on-load is admissible for the purposes of isolation or emergency switching. For a more frequent duty, the number of operations and load characteristics according to the manufacturer’s instructions should be taken into account or an alternative device from those listed as suitable for functional switching in Table 53.4 should be employed.

NOTE 1: An entry of (1,3) means that the device is suitable for on-load isolation only if it is marked with the symbol for on-load isolation
NOTE 2:In the above table, the functions provided by the devices for isolation and switching are summarized,

 

[amberleaf]

134.1 Erection :icon_bs:
134.1.1 Good workmanship by skilled or instructed persons and proper materials shall be used in the erection of the electrical installation.
The installation of electrical equipment shall take account of manufacturers’ instructions.

134.2 Initial verification
134.2.1 During erection and on completion of an installation or an addition or alteration to an installation, and before it is put into service, appropriate inspection and testing shall be carried out by skilled persons competent to verify that the requirements of this Standard have been met.

Appropriate certification shall be issued in accordance with Sections 631 and 632.

Ordinary person
Person who is neither a skilled person nor an instructed person .

Instructed person (electrically).
Person adequately advised or supervised by electrically skilled persons ( as defined ) to enable that person to perceive risks and to avoid dangers hazards which electricity can create.

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

Note 1 : The term “ (electrically) ” is assumed to be present where the term “ skilled person ” is used throughout BS-7671:

 

[amberleaf]

Amendment 3: 2015 . :icon_bs:

Part 4
Protection for safety

Chapter 41 Protection against electric shock

411 Protective measure: Automatic Disconnection of Supply
411.3 Requirements for fault protection

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 32 A 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.

 

[amberleaf]

411.4 TN system

411.4.5 The characteristics of the protective devices (see Regulation 411.4.4) and the circuit impedances shall fulfil the following requirement:

Zs × Ia ≤ Uo ≤ Cmin

where: Zs is the impedance in ohms (Ω) of the fault loop comprising:
- the source
- the line conductor up to the point of the fault, and
- the protective conductor between the point of the fault and the source.

Ia is the current in amperes (A) causing the automatic operation of the protective device within the time specified in Table 41.1 of Regulation 411.3.2.2 or, as appropriate, Regulation 411.3.2.3.Where an RCD is used this current is the rated residual operating current providing disconnection in the time specified in Table 41.1 or Regulation 411.3.2.3.

Uo is the nominal a.c. rms or d.c. line voltage to Earth in volts (V).
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: For a low voltage supply given in accordance with the Electricity Safety, Quality and Continuity Regulations 2002 as amended,
Cmin ) is given the value 0.95.

NOTE : Where compliance with this regulation is provided by an RCD, the disconnection times in accordance with Table 41.1 relate to prospective residual fault currents significantly higher than the rated residual operating current of the RCD.

 

[amberleaf]

414 Protective Measure: Extra-low Voltage Provided by SELV or PELV

414.2. Requirements for basic protection and fault protection

Both basic protection and fault protection are deemed to be provided where:
(i) the nominal voltage cannot exceed the upper limit of voltage Band I, and
(ii) the supply is from one of the sources listed in Regulation 414.3, and
(iii) the conditions of Regulation 414.4 are fulfilled.

NOTE 1: If the system is …......

 

[amberleaf]

Protection Against Thermal Effects

421 Protection Against Fire Caused by Electrical Equipment

421.1 General requirements
421.1.1 Persons, livestock and property shall be protected against harmful effects of heat or fire which may be generated or propagated in electrical installations.

Manufacturers’ instructions shall be taken into account in addition to the requirements of BS-7671.

NOTE 1: Harmful effects of heat or fire may be caused by:
- heat accumulation, heat radiation, hot components or equipment
- failure of electrical equipment such as protective devices, switchgear, thermostats, temperature limiters, seals of cable penetrations and wiring systems
- overcurrent
- insulation faults or arcs, sparks and high temperature particles
- harmonic currents
- external influences such as lightning surge.
- inappropriate selection or erection of equipment

NOTE 2: Lightning strikes and overvoltages are covered in BS-EN-62305 and Section 443 of these Regulations.

 

[amberleaf]

New regulation .

► 421.1.201
Within domestic (household) premises, consumer units and similar switchgear assemblies shall comply with BS-EN-61439-3 and shall:
(i) Have their enclosure manufactured from non-combustible material, or
(ii) be enclosed in a cabinet or enclosure constructed of non-combustible material and complying with Regulation 132.12.

Note 1: Ferrous metal, e.g. steel, is deemed to be an example of a non-combustible material.
Note 2: The implementation date for this regulation is the 1[SUP]st[/SUP] January 2016, but does not preclude compliance with the regulation prior to that date .

 

[amberleaf]

132.12. Accessibility of electrical equipment

Electrical equipment shall be arranged so as to afford as may be necessary:
(i) Sufficient space for the initial installation and later replacement of individual items of electrical equipment
(ii) Accessibility for operation:
- inspection, testing
- fault detection
- maintenance and repair

 

[amberleaf]

511 Compliance with Standards

511.1 Every item of equipment shall comply with the relevant requirements of the applicable British or Harmonized Standard, appropriate to the intended use of the equipment. The edition of the standard shall be the current edition, with those amendments pertaining at a date to be agreed by the parties to the contract concerned (see Appendix 1).

Alternatively, if equipment complying with a foreign national standard based on an IEC Standard is to be used, the designer or other person responsible
for specifying the installation shall verify that any differences between that standard and the corresponding British or Harmonized Standard will not result in lesser degree of safety than that afforded by compliance with the British or Harmonized Standard . Such use shall be noted and appended to the appropriate documentation specified in Part 6 .

 

[amberleaf]

514.9 Diagrams and documentation

514.9.1 A legible diagram, chart or table or equivalent form of information shall be provided indicating in particular:
(i) the type and composition of each circuit (points of utilisation served, number and size of conductors, type of wiring), and
(ii) the method used for compliance with Regulation 410.3.2, and
(iii) the information necessary for the identification of each device performing the functions of protection, isolation and switching, and its location, and
(iv) any circuit or equipment vulnerable to the electrical tests as required by Part 6 .

For simple installations the foregoing information may be given in a schedule.
A durable copy of the schedule relating to a distribution board shall be provided within or adjacent to each distribution board.

Any symbol used shall comply with IEC 60617.

 

[amberleaf]

514.10 Warning notice: voltage

514.10.1 Every item of equipment or enclosure within which a nominal voltage exceeding 230 volts to earth exists and where the presence of such a voltage would not normally be expected, shall be so arranged that before access is gained to a live part, a warning of the maximum voltage to earth present is clearly visible.

 

[amberleaf]

521.10 Installation of cables

521.10.1 Non-sheathed cables for fixed wiring shall be enclosed in conduit, ducting or trunking. This requirement does not apply to a protective conductor complying with Section 543.

Non-sheathed cables are permitted if the cable trunking system provides at least the degree of protection IPXXD or IP4X, and if the cover can only be removed by means of a tool or a deliberate action.

NOTE: For a trunking system to meet IP4X requirements, IP4X trunking and related system components would need to be installed. If a system includes site-fabricated joints, the installer must confirm the completed item meets at least the degree of protection IPXXD.

New Regulation .
521.201 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 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.

 

[amberleaf]

( Out goes equipotential wording ) :svengo:

544 Protective Bonding Conductors :icon_bs:

544.1 Main protective bonding conductors

544.1.2 The main protective bonding connection to any gas, water or other service shall be made as near as practicable to the point of entry of that service into the premises. Where there is an insulating section or insert at that point, or there is a meter, the connection shall be made to the consumer’s hard metal pipework and before any branch pipework. Where practicable the connection shall be made within 600 mm of the meter outlet union or at the point of entry to the building if the meter is external.

 

[amberleaf]

559.5 Wiring systems

559.5.1 Connection to the fixed wiring

At each fixed lighting point one of the following shall be used for the termination of the wiring system:
(i) A ceiling rose to BS 67
(ii) A luminaire supporting coupler to BS 6972 or BS 7001
(iii) A batten lampholder or a pendant set to BS EN 60598
(iv) A luminaire to BS EN 60598
(v) A suitable socket-outlet to BS 1363-2, BS 546 or BS EN 60309-2
(vi) A plug-in lighting distribution unit to BS 5733
(vii) A connection unit to BS 1363-4
(viii) Appropriate terminals enclosed in a box complying with the relevant part of BS EN 60670 series or BS 4662
(ix) A device for connecting a luminaire (DCL) outlet according to IEC 61995-1.
(x) An installation coupler BS EN 61535.

NOTE: In suspended ceilings one plug-in lighting distribution unit may be used for a number of luminaires.

559.5.1.201
A ceiling rose or lampholder shall not be installed in any circuit operating at a voltage normally exceeding 250 volts.
559.5.1.202
A ceiling rose shall not be used for the attachment of more than one outgoing flexible cable unless it is specially designed for multiple pendants. 559.5.1.203
Luminaire supporting couplers and devices for the connection of luminaires are designed specifically for the electrical connection of luminaires and shall not be used for the connection of any other equipment.
559.5.1.204
Lighting circuits incorporating B15, B22, E14, E27 or E40 lampholders shall be protected by an overcurrent protective device of maximum rating 16A.
559.5.1.205.
Bayonet lampholders B15 and B22 shall comply with BS EN 61184 and shall have the temperature rating T2 described in that standard.
559.5.1.206.
In circuits of a TN or TT system, except for E14 and E27 lampholders complying with BS EN 60238, the outer contact of every Edison screw or single centre bayonet cap type lampholder shall be connected to the neutral conductor. This regulation also applies to track mounted systems.
559.5.1.207.
A lighting installation shall be appropriately controlled.

NOTE: See Table 53.4 for guidance on the selection of suitable protective, isolation and switching devices.

559.5.1.208.
Consideration shall be given to the provision of the neutral conductor, at each switch position, to facilitate the installation of electronic switching devices.

 

[amberleaf]

Part 6
Inspection & Testing :icon_bs:

Chapter 61
Initial Verification

610.5
The verification shall be made by a skilled persons, or persons, competent in such work

▼▼ Out 2015
Some methods of test are described in IET Guidance Note 3, Inspection & Testing, published by the Institution of Engineering and Technology. Other methods of testing are not precluded provided they give valid results

612.12 Check of phase sequence
For polyphase circuits, it shall be verified that the phase sequence is maintained.

Chapter 62
Periodic Inspection & Testing
621.5
Periodic inspection and testing shall be undertaken by a skilled person or persons, competent in such work .

Chapter 63
Certification & Reporting
631.4
Electrical Installation Certificates, Electrical Installation Condition Reports and Minor Electrical Installation Works Certificates shall be compiled and signed or otherwise authenticated by skilled person or persons, competent to verify that the requirements of the Standard have been met.

 

[amberleaf]

2015. :icon_bs:

P33. Protective equipotential bonding . Equipotential bonding for the purposes of safety .
P33. Protective bonding conductor . Protective conductor provided for protective equipotential bonding .

Fig 2.1. - Illustration of earthing and protective conductor terms ( see chapter 54)
(2) main protective bonding conductor

544. Protective bonding conductors
544.1. main protective bonding conductors
544.2. Supplementary bonding conductors

612.2.1. Continuity of protective conductors.
including main and supplementary equipotential bonding .

 

[amberleaf]

2015 . Watch your wording in Exams .

O.S.G. 4.3. :book:
Main protective bonding of metallic services .
O.S.G. 4.4
Earthing conductor and main protective bonding conductor cross-sectional areas

O.S.G. 4.3.
Main protective bonding of metallic services .
( Figures 2.1 (i) to 2.1 (iii))

The purpose of protective equipotential bonding is to reduce the voltages between the various exposed-conductive-parts and extraneous-conductive-parts of an installation, during a fault to earth and in the event of a fault on the DNO .

411.3.1.2. main protective bonding conductor(s)
are required to connect extraneous-conductive-part is a conductive part, such as a metal pipe , liable to introduce earth potential into the installation or building.

it is common. particularly under certain fault conditions on the LV supply network , for a potential to exist between true Earth, i.e. the general mass of Earth and the earth of the electrical system. Therefore, buried metallic parts which enter the building are to be bonded to the main earthing terminal of the electrical installation.

Examples of extraneous-conductive-parts
(a) metallic installation pipes
(b) metallic gas installation pipes
(c) other installation pipework , for example, heating oil
(d) structural steelwork of the building where rising from the ground
(e) lighting protection systems ( where required by BS-EN-62305)

 

[amberleaf]

530.3.1
In polyphase circuits the moving contacts of all poles of a multipole device shall be so coupled mechanically that they make and break substantially together, except:

 

[amberleaf]

2015 - 530.3.4 :icon_bs:
For an installation with a 230 V 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 ZA of the standard.

Appendix 1 ( normative ) P/309
BS EN 61439-3:2012.
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.

421.1.201 Within domestic (household ) premises, consumer units and similar switchgear assemblies shall comply with BS-EN61439-3 and shall:
(i) have their enclosure manufactured from non-combustible material, or
(ii) be enclosed in a cabinet or enclosure constructed of non-combustible material and complying with Regulation 132.12.

Note 1: Ferrous metal, e.g. steel, is deemed to be an example of a non-combustible material.
Note 2: You know the rest . 1[SUP]st[/SUP] of January 2016 .

 

[amberleaf]

2015 - O.S.G. 2.2.6. Consumer unit assemblies :book: :svengo:

421.1.201 Where a consumer unit is installed in domestic (household ) premises, domestic garages and outbuildings, one of the following applies:

► the enclosure manufactured from non-combustible material, or
► the consumer unit is enclosed in a cabinet constructed from non-combustible material

Note: This requirement will be effective from 1[SUP]st[/SUP] January 2016, although implementation before this date is not prohibited.

Ferrous metal, i.e. steel is deemed to be an example of a non-combustible material.

plastic enclosures manufactured from 960 degree glow-wire rated material would NOT be classified as “ non-combustible material ” in the context of this regulation .

Where a steel consumer unit is installed in an installation forming part of a TT system, the earth fault loop impedance Ze, is likely to be much higher than that permitted by the overcurrent protective device, i.e. cut-out. Should the tails become loose or damaged and make contact with the metal enclosure, it is likely that the overcurrent device will NOT operate within 5s . The IETs Wiring Regulations Policy Committee, therefore, advises the following:

(a) Consideration should be given to the selection and installation of a class 11 metal consumer unit when used on installation(s) forming part of a TT system. The consumer unit must have been validated as non-combustible using an appropriate test method such as an internal hot wire test and that the metal enclosure does not make contact with any line conductors in the event of an internal fire. Individual manufactures will be able to advice on products which meet these requirements, or

(b) A Class 1 metal consumer unit is installed and each outgoing circuit is protected by an RCBO.
(c) A split, Class1 metal consumer unit is installed, where the double-pole main switch of the consumer unit should incorporate an S type ( time delayed ) RCCB ,e.g. 100mA S - type RCCB.

Note: In cases where RCBOs protect each outgoing circuit. the risk of the solid busbar ( connecting the supply side of each RCBO ) making contact with the ferrous enclosure is minimal. In split consumer units, where two or three RCCBs protect multiple circuits through individual circuit-breakers, the risk of the single-insulated conductors ( connecting the load side of the double-pole main switch to the supply side of the RCCBs) making contact with the ferrous enclosure due to vibration and / or abrasion or being damaged is far higher. In essence, where the construction and layout of the consumer unit is such that the risk of live conductors making contact with the ferrous enclosure is minimal, then the double-pole main switch need not incorporate an S - type RCCB.

In all cases:
522.8.1.
(a) the tails need to be protected to avoid mechanical damage and disturbance at the incoming terminals in the consumer unit in order to avoid the line conductor becoming disconnected or damaged and making contact with the metal enclosure. e.g. clipping or clamping the tails, or installing in trunking and the use of a suitable cable-entry gland, In all cable entry arrangements, the enclosure shall not have sharp edges that could damage cables.

416.22. 416.22.1.
(b) entry point of the meter tails into the metal consumer unit must maintain the fire protection of the consumer unit so far as reasonably practicable. In essence, this means maintaining the requirement for the horizontal top surface of the enclosure to provide a degree of protection of at least IPXXD or IP4X and, elsewhere, IP2XC after installation in accordance with the manufacturer’s instructions as required by BS-EN-61439-3

522.8.1. 521.5.1.
(c) the meter tails also need to be protected to avoid any foreseeable damage and must enter a ferrous enclosure through the same entry point.

A non-combustible enclosure includes base, cover, door and any components, e.g. hinges, covers, screws and catches necessary to maintain fire containment, Devices and blanks are contained within the non-combustible enclosure and therefore, do not have to be manufactured in a non-combustible material e/g. steel, however, the use of non-combustible blanks is NOT precluded.

Where the consumer unit is to be located in an external non-habitable building, e.g. garage or shed, which is not in close proximity to a dwelling, consideration could be given to installing a consumer unit of non-ferrous construction, The term “ not in close proximity ” is always a moot point and the decision to install a non-ferrous enclosure must be supported by a documented risk assessment and must be appended to the Electrical Installation Certificate.

Useful junk . Belling Out - Slang for testing installations

 

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With your exams, PS the right word is used in Chief Examiner report. .

2015 . GN-3 have (( boldly marked out some important items )) in pages now :book:

2.6.17. Prospective fault current ( Ipƒ ) from wording(s)

434.1 Regulation 612.11. introduces the requirements of Regulation 434.1. into the testing section, the designer being required to determine the prospective fault current, under both short-circuit and earth fault conditions , Etc , at every relevant point of the installation ......

With the power on, the maximum value of the prospective short-circuit current can be obtained by direct .......... etc.

 

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Why is GN-3 & BS-7671:2015 so important in Exams . the Questions will be taken from these books .

The Regulation have to states the facts .
GN-3 , is Guidance , with BS-7671:2015 . Do you want , C&Gs “ Nil Pwa ” for their effort :13:

2015 GN-3 : Same wording .

For consumer units or distribution boards not at the origin, there can arise confusion over the term “ external earth loop impedance ” (Ze) and some prefer to write or note the earth fault loop impedance at the distribution board as Zdb. As this value is not external to the installation, the formula is modified to : ................ Zs + Zdb + ( R[SUP]1[/SUP] + R[SUP]2[/SUP] )

 

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re-cap 2015. “Making you Aware ” .

411.4.5. 411.5.3. Guidance Note 3 tell us , . Operation of residual current devices .
For each of the tests, readings should be taken on (( both )) positive and negative half-cycles and the longer operating time recorded . ( 0° / 180° )

Because we use a Megger Multifunction Tester’s it does it Automatically . everything is all right NO . C&Gs “ Nil Pwa ” for their effort .. does it make us complacent !!

 

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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 does not provide protection against overcurrent. Overcurrent protection is provided by a circuit-breaker . BS-EN-60898-1

 

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GN-3 Purpose of Initial verification . 611.2.
Chapter 61 of BS-7671:2008: states the requirements for “ INITIAL VERIFCATION ” As far as reasonably practicable, an inspection shall be carried out to verify :

GN-3 Purpose of Initial verification .
BS-7671:2011: provides a format list in Regulation 611.2. of items to be verified, again so far reasonably practicable; these as follows:

(A3 ) GN-3 Purpose of Initial verification .
BS-7671:2015: provides a format list in Regulation 611.2. of items to be verified, again so far reasonably practicable; these as follows:

Q) State the document that should accompany an Installation Electrical Installation Certificate or Electrical Installation Condition Report .

GN-3 P/12 . 1.3.1. ( Certificates and Reports )
(i) Schedule of items inspected .
(ii) Schedule of test results .

Following the initial verification of a new installation or changes to an existing installation.
an Electrical Installation Certificate together with a : Schedule of inspections and a Schedule of test results .....

is required to be given to the person ordering the work. in this context “ work meaning the installation work ” not the work of carrying out the inspection and testing. Likewise, following the periodic inspection and testing of an existing installation, an Electrical Installation Condition Report, together with schedules of inspection and schedules of test results, are required to be given to the person ordering the inspection .

Part of. Inspection checklist . :book:

GN-3 . Cooker control unit .
(a) Sited to one side and low enough for accessibility and to prevent flexes trailing across radiant plates . 522.2.1.
(b) Cable to cooker fixed to prevent strain on connections . 522.8.5.

 

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PS. have you looked :30:

From the IET . Books 2015.

Amendment(s) 3 - 2015
To discourage counterfeiting and help customers to recognise genuine copies of the IET Wiring Regulations, the IET has placed a hologram on the inside front cover of three of its new titles:


• BS 7671:2008+A3:2015
• On-Site Guide to BS 7671:2008+A3:2015
• Guidance Note 3, 7th Edition

The hologram contains the IET logo in large print and small and the word “ GENUINE ”, as well as a number of hidden measures, including text that is visible with a magnifying glass.

 

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O.S.G. :book:

Installation and use of Non-standard cables.

133.1.1. 511.1. 511.2.

For the purpose of this guidance publication and ensuring compliance with BS-7671: the installation and use of non-standard cables, such as
SY, CY, and YY cables is discouraged.

The letters signify:

S - steel braid
Y - PVC
C - copper braid

To identify:

SY cables - steel braided, usually translucent sheath, PVC insulated flexible conductors.
YY cables - usually gray PVC sheath, PVC insulted flexible conductors.
CY cables - tinned copper wire braid, usually gray PVC sheath, PVC insulated flexible conductors.

To meet the requirements of BS-7671: every item of equipment must comply with a British or Harmonized Standard, in the absence of such, reference can be made to IEC standards or the appropriate standard of another country, SY , YY and CY cables are NOT made to British or Harmonised Standards.

This is NOT deemed sufficient for the purposes of BS-7671:

it is important that cables have approval from an independent testing organisation and installers should ensure that all cables purchased have manufacturers’ identification and a specification reference/standard number printed on the sheath to ensure testing, if necessary, and traceability .

 

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O.S.G. :book: P/84

On-Site Guide is designed to be taken on-site for easy referencing and provides simple guidance on the application of BS-7671:

Consumer units in dwellings .

With BS-7671:2008+A3:2015: the requirements for non-combustible consumer units was introduced.

installers adding or amending circuits in dwellings will encounter older consumer units, i.e. those not complying with Regulation 421.201, for many years to come. it is important that installers do not advise the replacement of consumer units simply because they don’t comply with the current version of BS-7671:

To ensure the ongoing use of such enclosures and assemblies, the installer must ensure the following :

(a) confirmation that ALL conductor connections are correctly located in terminals and are tight and secure; this may involve seeking the advice of the manufacture of the equipment to establish correct torque setting for screwdrivers when checking terminals. This applies to all conductor/busbar connection within the consumer unit, not just those relating to the addition or alteration .

(b) there are no signs of overheating.
(c) all covers, shields and barriers supplied when originally installed are present and in good, serviceable condition .

it must be verified for all conductor/busbar connections:

(i) not clamping on insulation .
(ii) conductor not damaged e.g. through “ incision ” on a solid conductor during insulation removal, or strands removed .
(iii) conductors are correctly placed, for example on the correct side of a moving plate in a cage-clamp terminal .
(iv) permitted number of conductors per terminal is not exceeded .
(v) no undue strain on the electrical connection, particularly incoming tails

So far as is reasonably practicable, confirm that incorporated components such as a Main Switch, circuit-breakers, RCBOs, RCCBs etc ., are not subject of a product recall . This could be achieved by direct question to the manufacturer .