***Useful Information For The Working Sparky***

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Given my issue is with Earth , how do I Test that Earth ? Apprentices’

I understand the Basic Principles of using a Mulitmeter on a simple Circuit ( i.e. Testing for current in Series , for volt diffences in Parallel )
If I was Testing voltage in the Live , and I had a good Earth , or I was measure voltage across the Bulb , that would be easy .
But in the case of my Earth problem at the Switch , what do I need to Test : ?

You are worried about voltage on the Earth Conductor of the Lighting Circuit , for a start , Measure Voltage ( P-N . N-E . P-E )
Then put a bulb into on the Circuit , switch it on , and Measure them all again

Then take out all bulbs , turn OFF at the Mains switch , and Measure ( Lowest Ohms Range ) Résistances between them all :
Then Main Switch back on , and Measure Résistance ( N-E / Only :
You will be able to see what’s happening then , ( Get Measuring with Meter Ω )

Insulation Résistance Ohmmeters :

The instrument used should be capable of developing the test voltage required across the Load , The Test Voltage Required is : ( Table 61 ) (1) 250V d.c for SELV and PELV circuits : (2) 500V d.c for all Circuits rated up to and including 500V , but excluding Extra-Low voltage circuits mentioned above : (3) 1000V d.c for all Circuits rated above 500V up to 1000V
Instruments conforming to BS-EN 61557-2 will fulfil all the above instrument requirements :
The factors affecting in-service reading accuracy include 50Hz currents induced into cables under test , and capacitance in the test object , these errors cannot be eliminated by test procedures , capacitance may be as high as 5 uf , and the instrument should have an automatic discharge facility capable of safely discharging such a capacitance , Following an Insulation Résistance test , the instrument should be left connected until the capacitance within the installation has fully discharged ,

 

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Insulated Cables :

Non-Flexible Cables :
1, Correct type ( 521 ) :
2, Correct current rating ( 523 ) :
3, Protected against mechanical damage and abrasion ( 522.8 ) :
4, Cables suitable for high or low ambient temperature as necessary ( 522.1 ) :
5, Non-sheathed cables protected by enclosure in conduit , duct or trunking ( 521.10 ) :
Sheathed cables :
* Routed in allowed zones or mechanical protection provided ( 522.6.6 ) :
* in the case of domestic or similar installations not under the supervision of skilled or instructed persons , additional protection is provided by RCD having ( I∆n ) not exceeding 30mA ( 522.6.7 ) :
7, Cables in partitions containing metallic structural parts in domestic or similar installations not under the supervision of skilled or
Instructed persons should be / ↔ provided with adequate mechanical protection to suit both the installation of the cable and its normal use / ↔ provided with additional protection by RCD having (I∆n ) not exceeding 30mA ( 522.6.8 ) :
8, where exposed to direct sunlight , of a suitable type ( 522.11 ) :
9, not run in lift shat unless part of the lift installation and of the permitted type ( BS-5655 and BS-EN 81-1 ( 528.3.5 ):
10, buried cable correctly selected and installed for use ( 522.6.4 ) :
11, correctly selected and installed for use overhead ( 521 ) :
12, internal radii of bends not sufficiently tight as to cause damage to cables or to place undue stress on terminations to which they are connected ( relevant BS , BS-EN and 522.8.3 ) :
13, correctly supported ( 522.8.4 and 522.8.5 ) :
14, not exposed to water , etc, unless suitable for such exposure ( 522.3 ) :
15, metal sheaths and armour earthed ( 411.3.1.1 ) :
16, identified at terminations (514.3 ) :
17, joints and connections electrically and mechanically sound and adequately insulated ( 526.1 and 526.2 ) :
18, all wires securely contained in terminals , etc. without strain ( 522.8.5 and section 526 ) :
19, enclosure of terminals ( section 526 ) :
20, glands correctly selected and fitted with shrouds and supplementary earth tags as necessary ( 526.1 ) :
21, joints and connections mechanically sound and accessible for inspection , except as permitted otherwise ( 526.1 and 526.3 ) :

PELV :

PELV ( protective extra-low voltage ) installations are inspected and tested as for SELV ( 612.4.2 )
Installations except that an insulation test is not made between PELV circuits and ( 414.4.1 ) Earth :

( PELV systems may include a protective conductor connected to the protective conductor of the primary circuit , basic protection in the secondary circuit is dependent upon the primary circuit protection )

Functional extra-low voltage :
extra-low voltage circuits not meeting the requirements for SELV or PELV are inspected ( 612.4.4 ) and tested as low voltage circuits :

Electrical Separation :
The source of supply should be inspected to confirm compliance with Regulations , ( 612.4.3 ) in addition ,
Should any doubt exist , the voltage should be measured to verify it does ( 413.3.2 ) not exceed 500v ,

The insulation between live parts of the separated circuit and any other adjacent ( 612.4.3 ) in addition ,
Conductor ( in the same enclosure or touching ) and /or to earth , must be tested , this test should be performed at a voltage of 500v dc , and the insulation résistance should be not less than 1.0MΩ ,

Instrument : use an insulation résistance tester for this test :

The live parts of the separated circuit must be tested to ensure that they are electrically ( 413.3.2 ) separate from other circuits ,
This is achieved by testing between the live conductors of the separated circuit connected together and the conductors of any other adjacent circuit strapped together :

The first test applied to this arrangement is an insulation résistance test at 500v dc the insulation résistance should be not less than 1.0MΩ :

Instrument : use an insulation résistance tester for this test :

( 413.3.5 ) A separate wiring system is preferred for electrical separation , if multicore cables or insulated cables in insulated conduit are used , all cables must be insulated to the highest voltage present and each circuit must be protected against overcurrent ,

( 612.4.3 ) A 500v dc , insulation résistance test is performed between the exposed-conductive- ( 413.3.3 ) parts of any item of connected equipment , and the protective conductor or exposed-conductive-parts of any other circuit , to confirm compliance with the Regulations , the insulation résistance should be not less than 1.0MΩ

Instrument : use an insulation résistance tester for this test :

 

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NEW OR REWIRED DOMESTIC AND SIMILAR INSTALLATIONS : Apprentices’

* Does the 17th Edition require all 13 A socket-outlets in domestic premises to be RCD-protected ?
For new installations and rewires in domestic premises, all socket-outlets need to have additional protection by RCD, except perhaps for those intended to supply particular items of equipment such as freezers. Any socket-outlet not having RCD protection needs to be specifically labelled or otherwise suitably identified to indicate its intended use, such as ‘freezer only’. However, if the wiring to a dedicated socket-outlet is concealed in a wall or partition at a depth of less than 50 mm, or if the internal construction of the wall or partition includes metallic parts other than metallic fixings, the circuit will still need to be suitably protected (by RCD or other means). Regulation Numbers : 411.3.3 (522.6.6) (522.6.8 )
*The 17th Edition requires most if not all circuits in domestic premises to be RCD-protected. There have been a number of suggestions as to how the consumer unit may best be configured to comply with the Regulations, the most common being a main switch with RCBOs protecting each individual circuit. However, another suggestion favours a main switch with two RCDs protecting separate DIN rails. If careful consideration is given as to what each bar will control in the way of upstairs and downstairs lighting and power circuits, will this configuration comply?
Yes, as long as the division of final circuits between the RCDs is carefully considered so as to minimize the consequences of unwanted tripping. Separate RCD protection is not necessarily required for each circuit of an installation but, in order to minimize the likelihood and consequences of tripping, a single (‘front end’) RCD should not be used to protect all the circuits. Regulation Numbers : ( 314.1 )
* The 17th Edition does not now define a zone 3 in a bathroom or shower room. What electrical equipment and accessories can be installed in the area between 0.6 m and 3.0 m from the edge of the bath or shower basin? Moreover, what minimum degree of IP protection are manufacturers likely to recommend?
There is no change from the 16th Edition requirements – that is, the general rules apply. The manufacturer’s installation instructions must always be followed. Regulation Numbers : ( 512.2 ) ( 134.1.1 )
* Do ‘meter tails’ concealed in walls or partitions need to be protected in accordance with Regulations 522.6.6 and/or 522.6.8 ?
* Yes. Meter tails concealed in a wall or partition at a depth of less than 50 mm from a surface must be protected in accordance with Regulation 522.6.6. Also, irrespective of the depth from a surface, meter tails concealed in a wall or partition having internal metallic parts (except nails and screws, etc) are subject to the requirements of Regulation 522.6.8. Regulation Numbers : 522.6.6: 522.6.8 : 314.1: 314.2 :
However, additional protection for meter tails by means of an RCD is not an acceptable option in respect of Regulation 522.6.7 (which in consequence rules out reliance on 522.6.6(v), routing in the ‘safe zones’ alone), or in respect of Regulation 522.6.8(v). Also, for TT systems, the only option remaining is to provide suitable mechanical protection (that is, to comply with Regulations 522.6.8(iv) and/or 522.6.6(iv) as appropriate).
* Where the Regulations specify additional protection by RCD, does this include RCBOs ?
Yes. Where the generic term ‘RCD’ is used, it refers to most types of residual current device including RCBOs (Residual current-operated circuit-breakers with integral overcurrent protection), RCCBs (Residual current-operated circuit-breakers without integral overcurrent protection) and SRCDs (Socket-outlets incorporating a residual current device). For the purposes of the Regulations, it does not include PRCDs (Portable residual current devices). 411.3.3

• Does boiler pipework need to have additional equipotential bonding for electrical safety reasons ?
There is no specific requirement in the Regulations for boiler pipework to be supplementary bonded. However, such bonding may be called for in the boiler manufacturer’s instructions, in which case BS 7671 requires those instructions to be followed (Regulation 510.2 refers). Any stated requirement for additional bonding that is considered to be unnecessary should be queried with the manufacturer concerned, and amended installation instructions requested. Regulation Numbers : 411.3.3
* Does the dispensation in Regulation 701.415.2 to omit supplementary bonding in a location containing a bath or shower apply to TT systems? Yes Regulation Numbers : 701.415.2
* If the mains supply cable to a fixed appliance such as a flat screen TV is concealed in a wall or partition at a depth of less than 50 mm, does the 17th Edition require the lead to be RCD-protected in accordance with Regulation 522.6.7 even though it’s connected by means of a plug and socket ?
Yes. The risk of penetration by a nail or screw is the same as for other concealed cable. Also, if the wall or partition has internal metallic parts (except nails and screws, etc), RCD protection in accordance with Regulation 522.6.8 is required irrespective of the depth of the cable from the surfaces. Regulation Numbers : 522.6.7, 522.6.8
* To overcome thermal insulation issues, is it permissible to design a ring final circuit using 2.5 mm² cable protected by a 20 A protective device?
Yes, if the effective current carrying capacity of the cable is at least 12.5 A (20 A × 20/32), so as to effectively have the same ‘deemed to comply status’ as Regulation 433.1.5 gives to 30 A and 32 A ring final circuits. 433.1.5
* 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. 522.6.6 : 522.6.8 :

* Five flats are fed individually from five ‘sub-mains’ originating at the main intake position. The five gas and water meters are main bonded at the main intake position. Do we still need to provide main bonding in each of the flats?
Whilst main protective bonding is required at the main intake position, it is good practice also to provide main protective bonding in each flat even though, in this case, the origin of each installation could be considered to be at the main intake position. Regulation Numbers : 411.3.1.2
* Is an RCD main switch (such as a 100 mA time-delayed device) still required in the consumer unit of a new domestic installation forming part of a TT system?
For a domestic installation complying with the 17th Edition where all the final circuits are RCD-protected, an RCD main switch is no longer required, provided that the consumer unit is of all insulated construction.
*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 ?
No, but the device does need to be so placed and marked as to be readily identifiable and convenient for the intended use 537.3.2.4
* 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?
Yes. The particular requirements of BS 5839-6 take precedence over the general requirements of BS 7671. 110.1
* Does the R1 + R2 test confirm& the correct polarity of a radial circuit ?
No, not on its own. Whilst the test can provide an indication of polarity, it needs to be combined with inspection and further testing as required by Part 6 of BS 7671: 2008 ( 611.3, 612.6 )
* Appendix 15 of BS 7671: 2008 gives advice on ring final circuits and sharing/spreading the load around the circuit. Item (iii) suggests that cookers, ovens and hobs over 2 kW should be on their own dedicated circuit. Why can’t ovens of less than 3 kW be connected to a ring final circuit via a suitable connection point such as a socket-outlet or fused connection unit?
Appendix 15 is intended to give guidance only. Such connection is not prohibited, provided that no part of the ring final circuit will be overloaded as a result. 433.1.5 :
*Is it necessary to verify voltage drop during initial verification ?
Verification of voltage drop is not normally required unless there is considered to be a voltage drop problem. 612.14
* Considering Regulations 134.1.1 and 510.2 which require equipment to be installed in accordance with instructions provided by the manufacturer, are installers now required to check torque settings for connection tightness at consumer units where these are manufacturers instructions.
Yes. It is necessary to check that all connections are tight, and any specific installation instructions must also be followed.

 

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*In a location containing a shower, what is the horizontal limit of zone 1 for showers without a basin?
The limit of zone 1 horizontally is 1.2 m from the centre point of the fixed water outlet (the end of the rigid pipe of the fixed water installation) on the wall or ceiling, irrespective of whether the shower head is fixed or on the end of a flexible hose. Beyond zone 1, the general rules of BS 7671 apply, including Regulation 512.2 concerning external influences. In particular, the IP rating of any electrical equipment must be adequate. 701.32.4 : 512.2 :

Regulation 560.7.7 requires cables for safety circuits, other than metallic screened fire-resistant cables, to be adequately and reliably separated from other circuit cables. In addition to mineral insulated cables, what cables would be exempted from this separation requirement ? (560.7.7 )
Soft-skinned cables to BS 7629-1: 2008 would be exempted from the separation requirements as they have a metallic screen and their survival in a fire has been tested in accordance with BS EN 50200. However, cables to BS 8436: 2004 would not be exempted as the product standard does not require their fire resistance to be tested. Irrespective of the above, BS 5839-1 recommends that, for a fire detection and alarm system complying with that standard, the circuits of fire alarm systems should be segregated from the cables of other circuits to minimize the potential for those other circuits to cause malfunction of the fire alarm system.

*In a location containing a shower, what is the horizontal limit of zone 1 for showers without a basin?
The limit of zone 1 horizontally is 1.2 m from the centre point of the fixed water outlet (the end of the rigid pipe of the fixed water installation) on the wall or ceiling, irrespective of whether the shower head is fixed or on the end of a flexible hose. Beyond zone 1, the general rules of BS 7671 apply, including Regulation 512.2 concerning external influences. In particular, the IP rating of any electrical equipment must be adequate. 701.32.4 : 512.2 :

Regulation 560.7.7 requires cables for safety circuits, other than metallic screened fire-resistant cables, to be adequately and reliably separated from other circuit cables. In addition to mineral insulated cables, what cables would be exempted from this separation requirement ? (560.7.7 )
Soft-skinned cables to BS 7629-1: 2008 would be exempted from the separation requirements as they have a metallic screen and their survival in a fire has been tested in accordance with BS EN 50200. However, cables to BS 8436: 2004 would not be exempted as the product standard does not require their fire resistance to be tested. Irrespective of the above, BS 5839-1 recommends that, for a fire detection and alarm system complying with that standard, the circuits of fire alarm systems should be segregated from the cables of other circuits to minimize the potential for those other circuits to cause malfunction of the fire alarm system.
* As the designer of an installation, am I allowed to rely on the RCD element of an RCBO to provide for fault protection in order to allow for loop impedance values greater than given in Table 41.3?
Yes, so long as all the other applicable requirements of the 17th Edition are met, including those for protection against overload and short circuit. 411.4.4 : 411.4.5 : 411.4.9 :
* Are there any particular requirements relating to the mounting height or location of consumer units for electrical installations in new dwellings?
The provision of access to consumer units is not specifically covered by Building Regulations or BS 7671. However, consumer units need to be so located as to enable reasonable access to the users, including for the purpose of testing the RCDs at regular intervals, and in case of emergency. 132.12 : 341.1 : 513.1 :
* Is the space within an airing cupboard in a bathroom or shower room that would otherwise be in a particular zone were it not for the cupboard door, considered to be within that zone?
No, unless the cupboard door does not effectively limit the extent of the location. However, where an airing cupboard opens into zone 1 or zone 2, we recommend that circuits supplying equipment in the airing cupboard are be provided with additional protection in accordance with Regulation 415.1.1. 701.32.1 : 701.411.3.3 :
Note: Unless otherwise indicated, all references to ‘RCD’ in this section relate to residual current devices having a rated residual operating current ( I∆n ) not exceeding 30 mA and an operating time not exceeding 40 ms at a residual operating current of 5 ( I∆n ) provided as additional protection in the event of failure of the provision for basic protection and/or the provision for fault protection or carelessness by users (Regulation 415.1.1)

PLACES OF WORK – NEW INSTALLATIONS :

The 17th Edition requires socket-outlets rated at up to 20 A and intended for use by ordinary persons to be provided with additional protection by means of a 30 mA RCD. Many socket-outlets in offices may be considered to be subject to this requirement. However, many offices will have computers producing protective conductor current, individually and/or collectively. This accumulated protective conductor current could cause the circuit RCD to operate. Such disruption will not be acceptable to the office users, particularly in banks etc. How can such unwanted tripping be avoided?
Where additional protection by RCD is necessary, unwanted tripping can be avoided by appropriate sub-division of circuits. 314.1, 531.2.4.
*Which 13 A socket-outlets in commercial and industrial premises are required to have additional protection by RCD?
Socket-outlets in commercial and industrial premises must have additional protection by means of an RCD if they are rated at 20 A or less and are for general use without the supervision of a skilled or instructed person. An exception is made for a specific labelled/identified socket-outlet for a particular item of equipment. 411.3.3 :
The decision as to which socket-outlets are provided with RCD protection in accordance with these criteria should be made in consultation with the client’s duty holder under the Electricity at Work Regulations 1989 :
As a general principle, it may be considered that socket-outlets in commercial and industrial premises needing to have additional protection by means of an RCD include the following: those in common, circulation and public areas; those in self-catering areas; those intended for use by cleaners; and those that may reasonably be used to supply mobile equipment for use outdoors.
*Which socket-outlets in commercial and industrial premises are NOT required to have additional protection by RCD?
Socket-outlets in commercial and industrial premises must have additional protection by means of an RCD if they are rated at 20 A or less and are for general use without the supervision of a skilled or instructed person. An exception is made for a specific labelled/identified socket-outlet for a particular item of equipment. 411.3.3 :
The decision as to which socket-outlets are provided with RCD protection in accordance with these criteria should be made in consultation with the client’s duty holder under the Electricity at Work Regulations 1989.
As a general principle, it may be considered that socket-outlets in commercial and industrial premises NOT needing to have additional protection by means of an RCD include the following: a socket-outlet labelled for the connection of a specific item of equipment; socket-outlets not intended for general use, such as those in floor service boxes intended for the connection of workstations and other IT equipment; socket-outlets for use under the supervision of skilled or instructed persons so as to minimize the possibility of careless use.
* If an RCD is used to achieve automatic disconnection within the prescribed time, is the supplementary bonding called for in 411.3.2.6 still required? 411.3.2.2, 411.3.2.3, 411.3.2.4 :
No. An RCD is a valid way of complying with automatic disconnection requirements. 411.4.4 :
* In a milking parlour, is supplementary bonding required only where livestock can make simultaneous contact with extraneous-conductive parts (such as metallic gate posts and gates) and exposed- No. The 17th Edition requires all extraneous- and exposed-conductive-parts that can be touched by livestock to be supplementary bonded, whether or not the parts are simultaneously accessible.
No. The 17th Edition requires all extraneous- and exposed-conductive-parts that can be touched by livestock to be supplementary bonded, whether or not the parts are simultaneously accessible.
* Does a portacabin that is intended to be moved from place to place only infrequently, and which is supplied for example by SWA cable, fall within the scope of Section 717 of the 17th Edition? 717.1
No. Section 717 applies to transportable units that are intended to be moved relatively frequently from place to place and which therefore need to be supplied through flexible cables.

 

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PERIODIC INSPECTION OF EXISTING DOMESTIC AND SIMILAR INSTALLATIONS :

* During periodic inspections of domestic electrical installations, I often find that cables that are concealed in walls at a depth of less than 50 mm have no additional protection by means of an RCD, as is now required for installations complying with the 17th Edition. What Recommendation Code should I give ?
Code 4. Although existing installations need to be assessed against the requirements of the 17th Edition, this does not necessarily mean that they require upgrading, unless a departure from the latest requirements constitutes an immediate or potential danger. Introduction to BS 7671: 2008

*What Recommendation Code should be given if it is found that there is no supplementary bonding in a bathroom, and the alternative protective measures called for in the 17th Edition are not present ?
Recommendation Code 2
* Is it necessary to verify voltage drop during a periodic inspection?
Verification of voltage drop is not normally required unless there is considered to be a voltage drop problem. 621.2
*What should be recommended if, during a periodic inspection, the safety of an installation forming part of a TT system is found to be relying on a voltage-operated earth-leakage circuit-breaker (VOELCB) for fault protection?
If a VOELCB on a TT system fails to operate when tested with an instrument or integral test button, this would normally warrant a Code 1 recommendation (requires urgent attention).
But, subject to the VOELCB being proved to operate correctly, continued reliance on it for fault protection (protection against indirect contact) would normally warrant a Code 4 recommendation.
However, if the VOELCB relies on a water pipe not permitted by Regulation 542.2.4 to be a means of earthing, this should attract a Code 2 recommendation (requires improvement).

 

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Periodic Inspection Reporting -
Recommendation Codes for Domestic and Similar
Electrical Installations ,

In General Terms : The Recommendation Codes should be Used as Follows :

Code (1) ( Requires Urgent Attention )
This code is to be used to indicate that danger exists ,
Requiring urgent remedial action .
The persons using the installation are at risk . the person ordering the report should be advised to take action without
Delay to remedy the observed deficiency in the installation , or to take other appropriate action ( such as switching off –
And isolating the affected parts of the installation ) to remove the danger . the inspector should not wait for the full report
To be issued before giving this advice .

As previously indicated . some certification .
Registration and membership bodies make available “ Dangerous Condition “ notification forms to enable inspectors to record ,
And then to communicate immediately to the person ordering the report , any Dangerous condition discovered ,

Code (2) ( Requires Improvement )
This code is used to indicate that the observed deficiency requires action to remove potential danger .

The person ordering the report should be advised that ,
Whilst the safety of those using the installation may not be at immediate risk , remedial action should be taken as soon as possible
To improve the safety of the installation ,

Code (3) ( Requires further investigation )
It would be unusual to need to attribute a Recommendation Code 3 to an observation made during the periodic inspection of a domestic or similar installation ,

However , the code could be used to indicate , that the inspector was unable to come to a conclusion about an aspect of the installation or . alternatively . that the observation was outside the agreed purpose , extent or limitations of the inspection ,
But has come to the inspectors attention during the inspection and testing

The person ordering the report should be advised that the inspection has revealed an apparent deficiency which could not , due
To the agreed extent or limitations of the inspection , be fully indentified , and that the deficiency should be investigated as soon as possible .
A Recommendation Code 3 would usually be associated with an observation on an aspect of the installation that was not foreseen
When the purpose and extent of the inspection , and any limitations upon it , were agreed with the client .

The purpose of periodic inspection is not to carry out a fault-finding exercise .
But to assess and report on the condition of the installation within the agreed extent and limitations of the inspection .

Code 4 ( does not comply with the current issue of BS-7671 )
This code is to be used to indicate that certain items have been identified as not complying with the Requirements of the current issue of BS-7671 , but that the users of the installation are not in any danger as a result ,

The person ordering the report should be advised that the code is not intended to imply that the installation is unsafe , but
That careful consideration should be given to the benefits of improving those aspects of the installation ,

General requirements :

Where you observe a real and immediate danger that puts the safety of those using the installation at risk, you
should give a Recommendation Code 1 (requires urgent attention). You should also advise the customer
immediately (preferably in writing) that urgent work is necessary to remove the danger. This action is
necessary to satisfy the duties imposed on the inspector
and others by the Health and Safety at Work etc Act 1974 and the Electricity at Work Regulations 1989.

A Code 2 recommendation should be given where

the observed deficiency requires action to remove potential danger. In that case the customer should be
advised that, whilst the safety of those using the installation may not be at immediate risk, action should
be taken without delay to remove the potential danger to make the installation safe.

We believe it would not be reasonable to report that the condition of the installation is ‘satisfactory’ if any
observation in the report has been given a Recommendation Code 1 or Code 2 according to Best
Practice Guide No. 4,

The recommended interval until the next inspection should be made conditional upon all the observations
with a Recommendation Code 1 or Code 2 being put right to make the installation safe.
It would be unusual to give a Recommendation Code 3 (requires further investigation) to an observation made
during the periodic inspection of a domestic or similar installation. Where a Code 3 is justified, and there is no
Recommendation Code 1 or 2, you should consider your overall assessment of the condition of the
installation carefully before deciding whether to record it as ‘satisfactory’ or ‘unsatisfactory’ in the report.

Dangers :
During the inspection, you should identify any dangers that might occur during testing, and take appropriate
safety precautions. Where it is necessary to inspect live parts inside equipment the supply to the equipment
must first be isolated, proved dead and locked off, prior to access

Dangerous conditions

If you identify a dangerous condition, you should contact the customer urgently to get permission to
carry out any necessary work to make the condition safe. While waiting for permission, you should make
every effort to reduce the risk of danger to people, animals and property. If necessary the area of danger
should be blocked off and appropriate warning notices fitted.

Disturbance to the installation of the property and its owner (or occupier) :

Any inspection and testing should be done without disturbing the electrical installation or the occupier of
the dwelling more than is necessary. Where it is necessary to disconnect part or all of an installation to
carry out a test, you should do this at time agreed with the owner (or occupier).

Questions :

You may need to ask the homeowner about:
• diagrams of the electrical installation;
• records of previous electrical installation
inspections and tests;
• the electricity supply, for example, the location of
the consumer unit and meter; and
• earthing arrangements, for example, the location
of any protective bonding clamps (such as at the
stopcock for the water main or gas supply).
Usually the homeowner will not have this information,
and you will need to carry out some exploratory work so
inspection and testing can be done safely and
effectively. This work will include gathering information
about circuits, switchgear and controlgear.

Changes :

You should make a note of any known changes, either
in environmental conditions, the structure of the
building or any alterations or additions affecting the
suitability of the present installation, such as whether or
not the method of wiring is still suitable for its present load or environment

Visual inspection of electrical equipment :

You should make a thorough visual inspection of all electrical equipment that is not concealed, including
the accessible internal condition of an appropriate sample of all equipment. (Normally, for each circuit, a
sample of at least 20% to 30% of the accessories or points is necessary.)
The condition of the equipment and of any damage found should be noted and recorded in the report. The
condition of all electrical equipment and materials

sample of at least 20% to 30% of the accessories or points is necessary.)
The condition of the equipment and of any damage found should be noted and recorded in the report. The
condition of all electrical equipment and materials
should also be noted, taking into account any information from the manufacturer. The notes should cover:

• safety
• wear and tear
• corrosion
• damage; excessive loading (overloading)
• age
• external influences (such as mechanical impact or presence of water), and
• if the equipment is suitable for the installation.

You should assess condition of the equipment, together with any changes made to the building or its services
which affect electrical safety.

• Switchgear.
• Luminaries.
• Socket-outlets.
• Other electrical points (such as lighting and cooker points).

Any sign of overheating, overloading or damage to the insulation, armour, sheath or conductors needs to be noted.

Flexible cables and cords :

Where a flexible cable or cord forms part of the fixed wiring installation, your inspection should include:
• an examination of the cable or cord, for damage or faults

• an examination of the terminations and anchorages for damage or faults, and
• evidence of correct installation and extra
protection against mechanical damage and heat,
for example, by using heat-resistant sleeving.
Accessories and switchgear You should make a thorough internal visual inspection
of the accessible parts of a sample of accessories and switchgear to assess their electrical and mechanical condition.
However, every switching device that is a part of the installation under inspection will need to be inspected if the sample inspection shows up:
• results that are noticeably different from any results recorded previously
• results that are noticeably different from those expected, or
• poor conditions (for example, fluid in the accessories or switchgear, or worn or damaged
mechanisms), unless there is clear evidence of how the damage to the equipment occurred.

Protective devices :

You should confirm that protective devices, such as circuit-breakers, fuses and RCDs are:
1. in the correct position
2. in good working order
3. suitable for the type of earthing system
4. of the correct type, size and overload rating (or setting) for the circuits that they protect
5. easy to access for normal operation, maintenance and inspection, and
6. labelled correctly.

 

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Ring Circuit :

R1 = 0.42Ω Line / Line : Ring Final Circuits ( Measured End to End ) Continuity ( Dead Test )
Rn = 0.43Ω Neutral / Neutral : Ring Final Circuits ( Measured End to End ) Continuity ( Dead Test )
R2 = 0.73Ω Earth – Earth : Conductor : Ring Final Circuits ( Measured End to End ) Continuity ( Dead Test )

Leads on Line Conductor / Neutral Conductor

* Ring – Circuit : Line and Neutral ↔ Line and Neutral : on Connector Block R1 / Rn ( Set on Ohms : Tested 0.19Ω )
* Ring – Circuit : Line and Neutral at each Sockets , Adapter Socket for Leads = 0.20
Spur on the Ring / will be higher : Ω

Leads on Line Conductor / Earth Conductor

* Ring – Circuit : Line and Earth ↔ Line and Earth : on Connector Block at CCU : = 0.23Ω
* Ring – Circuit : Line and Earth : → Adapter Socket for Leads = 0.25Ω .. at each Socket in Ring ,

R1 + R2 All circuits ( At Least one Column to be Completed )
0.43 + 0.73 = 1.16 ( 1.16 ÷ 4 = 0.29Ω )
1.16 ÷ ( 4 ) = 0.29Ω ( along as the Reading was Not taking with a Spur on the Ring ( 4 ) ←

Remember to Null leads : or subtract :

( Big Copper Lower Résistance )

 

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Lighting Circuits , ( Dead Test ) Lighting Circuit is a Parallel Circuit :

Line / Earth : on Connector Block at CCU :
At Pendent : Lead on CPC / Lead on Switch Live , = 0.70Ω
Switch is On at testing
( Polarity can be Checked by turning the switch OFF ) “ Open Circuit “ > 9999 or 2000 ≈ 0º / 180º ≈ Testing ,

The furthest Light ( R1 + R2 )

Remember to Null leads : or subtract :

Code 3 ( Requires further investigation )
Observations’ that would usually warrant a Code 3 :

Recommendation include :

* Unable to trace final circuits :
* Unable to access equipment or connections needing to be inspected that are known to exist but have been boxed in such as by panels or boards that cannot be easily removed without causing damage to decorations :
* insulation résistance of less than 1 Megohms between Live conductors connected together and Earth ,
When measured at the consumer unit with all final circuit connected ,

Domestic Inspection & Testing : 2392-10

External Earth Fault Loop Impedance “ Ze “ : ( Danger Live Test )

Main Eathing Conductor Disconnected 16mm2 ( Parallel Paths )

RCD Non – Trip Tester : ( 3 – Leads )

Locked OFF : ( Caution : Electrician at work do not switch on )

Lead on Earth , 1st ← 16mm2
Lead on Neutral , 2nd ← ←← : this may come up :
Lead on Line , Testing : 241V ( Polarity Checked ) = 0.69Ω 1st ← “ Good Practice to Repeat this Test “( 0.66Ω ) 2nd

Highest off the Two Readings : ←

Re-Connect Main Eathing Conductor 16mm2 :

External Earth Fault Loop Impedance “ Ze “ Commonly used for ( Ra ) for TT Systems :

Measurement of Installation Earth Electrode Résistance

* Method (1) fusing a four-terminal Proprietary Earth Electrode Test Instrument :
20 ↔ 30 m ↔ : 2m ← → 2m
Method (1) fusing a three-terminal Proprietary Earth Electrode Test Instrument :
20 ↔ 30 m ↔ : 2m ← → 2m
Temporary Test Rods

Domestic CCU : 2392-10

416.2.2 : IP4X : hole no greater than 1mm ( Top )

416.2.4 : IP2X : hole no greater than 12.5mm ( Sides & Fronts )
No deeper than 80mm into the Enclosure

Segregation of Band I & Band II circuits or Band II insulation used :

Band II ( Normally low voltage ) 50 volts :
Band I (Normally Extra-low voltage ) 120 volts :
Band I / Band II - can only be contain in the same Wiring Systems : ( 528.1 ) if Adopted ;

Domestic Inspection & Testing :

Measurement of Maximum Prospective Fault Current , ( Danger Live Test )
This is Locked OFF :
Prospective Earth Fault Current :

Lead on Main Eathing Bar 1ST
Lead on Neutral 2nd
Lead on Live

Tester : 242 V loop Reading = 0.66Ω this will very though out the day
You have parallel paths in ( PFC ) 375 A

Next Test :
Prospective Short Circuit Current :
With 3 – Leads : you put Green one onto the Blue one
Line by its self
Short is Between ( Live & Neutral )

Lead on Neutral 1st
Lead on Line 2nd
Good Practice to Repeat this Test “

Expecting a Low Loop Reading here , lot more Copper in Circuit , = 0.53Ω
242 V ( PFC 458 Amp )

Highest Reading on to the Test / Schedule of Test Results , kA ( PFC )
Prospective Fault Current :
At Consumer Unit(s) kA

Amps to kA

Reading , 760A ÷ 1000 = 0.76kA
Reading , 1760A ÷ 1000 = 1.76kA

Domestic Inspection & Testing :

Earth Fault Loop Impedance ( Zs ) by Measurement and by Calculation : ( Danger Live Test )

Cover been put on the Consumer Unit and Supply Connected

This Live Test should only be taken on Sockets , they have No exposed parts
243 v ( Polarity Correct ) 1st Loop = 0.72Ω Around all Sockets : 2nd Loop = 0.74Ω / 234V

The Highest Reading you obtain : / Schedule of Test Results , ↔
Maximum Measured Earth Fault Loop Impedance , Zs Ω

RCD no-Trip Tester ,

Calculation to Determine
Earth Fault Loop Impedance ( Zs )
Zs = Ze + R1 + R2 )
Zs = Ze + 0.8
Zs = 0.69 + 0.8 = Zs = 1.49Ω

Zs = 1.49Ω
Radial Circuit ,

Domestic Inspection & Testing :

Polarity Tests :
Confirmed on other ways , ( R1 + R2 ) ( Ze ) ( Zs ) Confirmed Polarity ,

Metal Trunking :

(1) Line and Natural cables contained in the same metal trunking ( 521.5.2 )
(2) Protected against damp or corrosion ( 522.3 & 522.5 )
(3) Earthed ( 411.4.2 )
(4) Joints mechanically sound and of adequate continuity ( 543.2.4 )

Busbar Trunking and powertrack systems :

(1) Busbar Trunking to comply with BS-EN 60439-2 or other appropriate standard and powertrack system to comply with
BS-EN 61534 series or other appropriate standard ( 521.4 )
(2) Securely fixed and adequately protected against mechanical damage ( 522.8 )
(3) Joints mechanically sound and of adequate continuity ( 543.2.4 )

Conduits :

(1) Securely fixed, box lids in place and adequately protected against mechanical damage ( 522.8 )
(2) Inspection fittings accessible ( 522.8.6 )
(3) Number of cables for easy draw not exceeded 9 522.8.1 & See , On Site Guide Appx 5 )
(4) Solid elbows and tees used only as permitted ( 522.8.1 & 522.8.3 )
(5) Ends of conduit reamed and bushed ( 522.8 )
(6) Adequate boxes suitably spaced ( 522.8 and see , On Site Guide Appx 5 )
(7) Unused entries blanked off where necessary ( 412.2.2 )
(8) Conduit system components comply with a relevant British Standard ( Section 511 )
(9) Provided with drainage holes and gaskets as necessary ( 522.3 )
(10) Radius of bends such that cables are not damaged ( 522.8.3 )
(11) Joints , scratches , etc. in metal conduit protected by painting ( 134.1.1 & 522.5 )

Rigid Metal Conduit :

(1) Complies with BS-EN 50086 or BS-EN 61386 ( Section 511 )
(2) Connected to the main earth terminal ( 411.4.2 )
(3) Line and Neutral cables contained in the same conduit ( 521.5.2 )
(4) Conduit suitable for damp and corrosive situations ( 522.3 & 522.5 )
(5) Maximum span between buildings without intermediate support ( 522.8 and see Guidance Note 1 and On Site Guide Appx 5 )
Guidance Note 1 ↔ “ Selection and Erection of Equipment “

Rigid Non-Metal Conduit :

(1) Complies with BS-4607 , BS-EN 60423 . BS-EN 50086-2-1 or the BS-EN61386 . series ( 521.6 )
(2) Ambient and working temperatures within permitted limits ( 522.1 and 522.2 )
(3) Provision for expansion and contraction ( 522.8 )
(4) Boxes and fixings suitable for mass of luminaire suspended at expected temperature ( 522.8 , 559.6.1.5 )
Greggs : ( 559.6.1.4 ) ( LSC )

Flexible Metal Conduit :

(1) Complies with BS-EN 60423 & BS-EN 50086-1 or the BS-EN 61386 series ( 521.6 )
(2) Separate protective conductor provided ( 543.2.1 )
(3) Adequately supported and terminated ( 522.8 )

Trunking :

General ,
(1) Complies with BS-4678 or BS-EN 50085-1 ( 521.6 )
(2) Securely fixed and adequately protected against mechanical damage ( 522.8 )
(3) Selected , erected and routed so that no damage is caused by ingress of water ( 522.3 )
(4) Proximity to non-electrical services ( 528.2 )
(5) Internal sealing provided where necessary ( 527.2.4 )
(6) Holes surrounding trunking made good 9 527.2.1 )
(7) Band I circuits partitioned from Band II circuits or insulated for the highest voltage present ( 528.1 )
(8) Circuit partitioned from Band I circuits or wired in mineral-insulated metal-sheathed cables ( 528.1 )
(9) Common outlets for Band I and Band II provided with screens , barriers or partitions ,
(10) Cables supported for vertical runs ( 522.8 )

Areas common to most buildings ( Lux ) Lighting :

Entrance hall , Lobby , Waiting room 200 Lux
Enquiry desk 500 Lux
Corridor , Passageway , Stairs 100 Lux
Atria 50 – 200 Lux
Changing room , Cloakroom , Lavatory 100 Lux
Rest room 150 Lux
Canteen , Cafeteria , Dining room 200 Lux
Kitchen 300 Lux

Offices :

General Offices 500 Lux
Computer Workstations 300 – 500 Lux
Conference room , Executive Office 300 – 500 Lux

Banks & Building Societies :

Counter , Office Area : 500 Lux :
Public Area : 300 Lux :

Retailing :

Fashion : 500 / 750 Lux
Supermarket 750 : Lux
Restaurant 200 Lux
Bookshop , Chemist , Jeweller 500 Lux
Superstore 1000 Lux
Electrical / Furniture Store 750 Lux
Showroom 500 / 750 Lux
Arcades and Malls 50 / 300 Lux

Places of Public Assembly :

Cinema and Theatre Foyer 200 Lux
Booking Office 300 Lux
Auditoria 100 – 150 Lux
Library 150 – 300 Lux
Museum Art Gallery 50 – 300 Lux
Lecture Theatre 300 Lux
Church 100 – 300 Lux

Hotels :

Entrance Hall 100 Lux
Reception on Desk 300 Lux
Bar , Restaurant , Dining room , Lounge 50 – 200 Lux
Bedroom 50 – 100 Lux
Kitchen 150 – 300 Lux

Areas Common to Most Buildings

Performing a Test on SWA :

length of SWA 2.5mm 3 core wired into a Consumer Unit at one end and an isolator at the other.
how to perform a test on SWA ;

1 , Continuity ( 612.2

2 , Insulation Resistance ( 612.3

3 , Polarity ( 612.6

Performing a Test on SWA :

Isolate Consumer Unit :

( 1 ) Remove conductors from CU , terminals

( 2 ) Connect line to cpc of SWA & test continuity at the load side of isolator between line & cpc, turn isolator on / off
while testing proves line is switched ( R1 + R2 done & polarity )

( 3 ) Remove link between line & cpc

( 4 ) Set meter to 500v test IR between line & cpc

( 5 ) Test IR between line & neutral

( 6 ) Test IR between neutral & cpc

 

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Motor Circuits :

Loop impedance tests on motor circuits can only be carried out on the supply side of isolated motor controlgear .
Continuity tests between the circuit protective conductor and motor are then necessary ,

Circuits incorporating an RCD :

Where the installation incorporates an RCD , the value of earth fault loop impedance obtained in the test should be related to
The rated residual operating current ( I∆n ) of the protective device , to verify compliance with Section 413 of BS-7671 ,

Zs ( I∆n ) ≤ 50 for TN-Systems :

411.5.3 : Ra ( I∆n ) ≤ 50 for TT-Systems :

Operation of residual current devices :
612.8.1 Where there is RCD protection , the effective operation of each RCD must be verified by a test simulating an appropriate fault condition independent of any test facility ( 411.3.3 ) incorporated in the device ,
Followed by operation of the integral test device , the nominal rated tripping current should not exceed 30mA where the
RCD provides additional protection for socket-outlets not exceeding 20A intended for general use by ordinary persons or mobile equipment having a current value not exceeding 32A that is being used outdoors ,

Inspection Checklist :

( This checklist may also be used when carrying out periodic inspections )

General ,

(1) Complies with requirements : ( 133.1 – 134.1 )
(2) Accessible for operation , inspection and maintenance ( 513.1 )
(3) Suitable for local atmosphere and ambient temperature ( Ch 52 ) see BS-EN 60079 for electrical apparatus for the use in an explosive gas atmosphere and BS-EN 61241 for electrical apparatus for use in the presence of combustible dust )
(4) Circuits to be separate ( No borrowed Neutrals 314.4 )
(5) Circuits to be identified ( Neutral and Protective conductors in the same sequence as Line conductors 514.1.2 – 514.8.1 )
(6) Protective devices adequate for intended purpose ( Ch 53 )
(7) Disconnection times likely to be met by installed protective devices ( Ch 41 )
(8) Sufficient numbers of conveniently accessible socket-outlets are provided in accordance with the design ( 553.1.7 )
(9) All circuits suitably identified ( 514.1 – 514.8 -514.9 )
(10) Suitable main switch provided ( Ch 53 )
(11) Supplies to any safety services suitably installed , e.g. Fire Alarms to BS 5839 and Emergency lighting to BS 5266
(12) Environmental IP requirements accounted for ( BS-EN 60529 )
(13) Means of isolation suitably labelled ( 514.1 – 537.2.2.6 )
(14) Provision for disconnecting the Neutral ( 537.2.1.7 )
(15) Main switches to single-phase installations , intended for use by an ordinary person , e.g. domestic . shop . office premises . to be double-pole ( 537.1.4 )
(16) RCDs provided where required ( 411.1 – 411.3 -411.4 - 411.5 – 522.6.7 – 522.6.8 – 532.1 -701.411.3.3 – 701.415.2 – 702.55.4 – 705.411.1 – 705.422.7 – 708.553.1.13 – 709.531.2 – 711.410.3.4 – 711.411.3.3 - 740.410.3 - 753.415.1 )
(17) Discrimination between RCDs considered ( 314 – 531.2.9 )
(18) Main earthing terminal provided ( 542.4.1 ) readily accessible and identified ( 514.13.1 )
(19) Provision for disconnecting earthing conductor ( 542.4.2 )
(20) Correct cable glands and gland plates used ( BS-6121 )
(21) Cables used comply with British or Harmonised Standards ( appendix 4 of the Regulations 521.1 )
(22) Conductors correctly identified ( section 514 )
(23) Earth tail pots installed where required on mineral insulated cables ( 134.1.4 )
(24) Non conductive finishes on enclosures removed to ensure good electrical connection and if necessary made good after connecting ( 526.1 )
(25) Adequately rated distribution boards ( BS-EN 60439 may require derating )
(26) Correct fuses or circuit-breakers installed ( Sections 531 & 533 )
(27) All connections secure ( 134.1.1 )
(28) Consideration paid to electromagnetic effects and electromechanical stresses ( Ch 52 )
(29) Overcurrent protection provided where applicable ( Ch 43 )
(30) Suitable segregation of circuits ( Section 528 )
(31) Retest notice provided ( 514.12.1 )
(32) Sealing of the wiring system including fire barriers ( 527.2 )

There are Two Methods for Measuring the values of ( PFC ) but these can only be used when the supply has already been connected .
By then , the fuses and circuit breakers will already be installed .

The first Method is to Measure the Impedance of the supply by Determining its Voltage Regulation ,
That is the amount by which the Voltage falls with an increase in current ,
For Example : Consider an Installation with a no-load terminal voltage of 230V . if when a current of 40A flows ,
The voltage falls to 228V . the volt drop will be due to the Impedance of the Supply ,

Thus ( Zs ) = Systems volt drop = 230 – 228 Ω = 2 Ω
……………. Current ………………......... 40 ……….. 40 …………… 2Ω ÷ 40A = 0.05 Ω


Then ( PFC ) = Uo = 230V = 4600A / or 4.6 kA
……………………..... Zs …….. 0.05Ω …… ( 230V ÷ 0.05Ω = 4600 kA - ( PFC )


A Second Measurement Method is to use a Loop Impedance Tester , and Connected to Phase – Neutral
( Instead of Phase and Earth ) to Measure Supply Impedance , This can then be used with the Supply voltage as above to Calculate ( PFC ) ,

Some Manufacturers modify their Earth-loop testers so that this connection is made by selecting “ PFC “ with a switch .
The instrument measures supply voltage , and Calculate . then displays ( PFC )

A possible difficulty in measuring ( PFC ) and thus being able to use fuses or circuit breakers with a lower breaking capacity
Than that suggested by the supply Company , is that the supply may be reinforced . more load may result in extra or
Different transformers’ and cables being installed , which may reduce supply Impedance an Increase ( PFC )

Using 240V - 238 = 2Ω ( 2 ÷ 40A = 0.05Ω ) 240 ÷ 0.05Ω = 4800 kA ( PFC )

Extent of the Work :

When entering into an agreement for the Periodic Inspection and Testing of a building under your control it is a fundamental requirement that the extent and limitations of the inspection and testing be fully described for the contractor. It is recommended that the following procedures are adopted and that the relevant points be discussed with the contractor prior to completing the agreement documents.
* Determine your requirements for inspection and testing and tailor the procedures accordingly.

* Agree before commencing the work the amount of down time that can be tolerated and arrange a provisional programme for switching off:

- Totally.
- Individual Areas or Distribution Boards.
* It is important that these times are confirmed immediately prior to the contractor switching off.

* As it is neither practical nor possible to inspect all parts of the installation, a sampling process will be employed, normally in the order of 10% of all accessories, lighting fittings and control equipment.

* Detail any limitations of the inspection and testing to be carried out and explain that the installation must not be dismantled in any way other than opening equipment covers, and that the building structure must not be disturbed. This means that concealed cables and equipment will not be inspected.

* Identify any new parts of the installation that may not need to be included in the work.

Contractor's Reports :
On completion of the Inspection a report should be provided by the contractor, detailing, to the best of their knowledge and belief, the condition of the installation, results of all tests carried out, a list of recommendations and a conclusion as to whether the installation is safe to use in its present state. If the conclusion drawn is that the installation is unsafe, then the supply should be switched off and notices placed warning of the danger before the contractor leaves site.
Visual Inspection Only :
Check for any obvious mechanical damage or deterioration of materials and equipment, exposed cables and live parts, missing covers, fixings, labels and notices etc.
N.B. This procedure will not necessitate switching off the installation.
Visual Inspection Supplemented By Testing
Visual Inspection :
Repeat as for Visual Inspection Only but also include a thorough inspection of:
* The main switchgear and all distribution boards. These should be inspected for the following:
• Fuses and MCBs are correctly rated for over-current and fault current
• Fuse and switch contacts are clean and have not been over-heating
• Conductor terminations are tight and correctly lugged (if possible)
• Busbar connections are properly made and clamps are tight.

* Cables - whenever possible cables should be inspected to ascertain:
• The suitability for the load and operating environment
• The condition of the insulation and protection
• Adequacy of fixings and mechanical protection
• Suitability of glands and shrouds
• Proper use of earthing rings and earth connections
• Any signs of over-heating and damage.

* Equipment, accessories and lighting fittings should be inspected for:
• Deterioration due to the atmosphere, mechanical damage, over-heating and adequate fixings.
• Connections of conductors and condition of flexes.
This should include removing light fitting covers, switch plates, socket outlets and covers of equipment.
A sample of approximately 10% of all parts and areas of the installation should be inspected.
N.B. Actual % to be agreed with yourselves.

 

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BS-7671:2008 Part 2 - page 32 fig- 2.1 ↔ (2) ( Old Equipotential bonding ) ↔ Main Protective Bonding Conductor 10mm2 → (2)

R2 – or Wander Lead Method :

50 meters : Wander Lead has a Résistance of One Ohm
Check this with the other Lead ( Testing Two Leads together )
On the Continuity Setting : Giving a reading off - R: 1.13Ω
(1) Null out or (2) Subtract at end off testing

( R2 ) When Testing Main Protective Bonding Conductor , it must be Disconnected both Ends :
Connect one Lead to Main Protective Bonding Conductor at ( CCU )
Connect one Lead to Main Protective Bonding Conductor at ( Main Water Pipe )
On the Continuity Setting : Giving a reading off - R : 0.03Ω
At this stage you have Continuity ,

On-Site Guide BS-7671 :2008 ( Table 9A )

Résistance of 10mm2 Copper Conductor ( 10 – 1 meter length - 1.83 MΩ ←

100 metres = 0.18Ω s approx ,
10 metres = 0.02Ω s approx ,

0.03Ω s = 15 metres approx ,

This Test is repeated the same way for the Gas : Main Protective Bonding Conductor 10mm2 and the Earthing Conductor

If the Main Protective Bonding Conductors & the Earthing Conductors , if they are visible through out is Length it is not necessary to do Continuity ( R2 )