Re-take - Useful Information for 2394 :

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What is insulation résistance ??

GN-3 . /39
The purpose of the insulation résistance test is to verify that the insulation of conductors' provides adequate insulation , is not damaged and that live conductor's or protective conductor's are not short-circuited .

 

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2395-302 Chief Examiners Report . ◄ refer to .

learn by mistakes .

When asked why the earthing conductor must be connected to the installation earthing system during a prospective fault current test, common answers given by candidates included that it would be dangerous if it wasn't connected and you would not be able to carry out the test if it wasn't connected.

Few candidates appreciated that the earthing conductor would be connected when a fault occurred and the parallel paths would increase the level of fault current that would flow, and it is this maximum value that must be determined during the test.

Chief Examiners' 2394 . (13)

Testing

When asked to explain why an earth fault loop impedance test needed to be carried out on existing circuits after a board change,
many candidates failed to state that the protective devices for these circuits would have changed

Few answers identified the need to confirm that the maximum earth fault loop impedance values was not exceeded in order to ensure the appropriate disconnection times would be met in the event of an earth fault.

Some candidates had difficulty explaining why the earthing conductor must be disconnected from the installation earthing arrangements during a measurement of external earth fault loop impedance. Most answers included comments relating to the removal of parallel paths, but

answers indicated the need to confirm the intended external path was effective. from the installation earthing arrangements during a measurement of external earth fault loop impedance. Most answers included comments relating to the removal of parallel paths, but

► few answers indicated the need to confirm the intended external path was effective. ◄◄◄

 

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C&Gs have asked this question many times .. & will not stop asking

Question on earth electrode testing . ( One method ) not typing out two pages . sorry

GN-3 2008: ◄► P/46
Earth electrode résistance . example .

Measurement by standard method
When measuring earth-electrode-résistances to earth where low values are required as in the earthing of the neutral point of a transformer or generator , test method 1 below may be used

Instrument used as earth electrode résistance tester for this test .

Test method 1
before this test is undertaken , the earthing conductor to the earth-electrode must be disconnected either at the electrode or at the main earthing terminal to ensure that all the test current passes through the earth-electrode alone

Note : This will leave the installation unprotected against earth-faults . ◄◄ safety

Note : After completion of the Testing ensure that the Earthing-conductor is Reconnected. ◄◄ safety

GN-3 2011: ◄
Earth electrode résistance testing .
Three methods' of measuring the résistance of an earth-electrode. refer . Test method E1 , Test method E2 , Test method E3 . ▼

GN-3 2008: Earth electrode for RCDs .
if the electrode under test is being used in conjunction with a residual current device the following method of test may be applied as an alternative to the earth electrode résistance test . where the electrical résistance to earth are relatively high& precision is not required , an earth fault loop impedance tester may be used .

TT- systems always get heads turning in Exams .

with TT - systems C&Gs are looking for safety at all times .

 

[Richard Burns]

Chief Examiners' 2394 . (12)
The final question on the paper required the candidate to describe an (earth fault loop path) for the system given in the scenario.
Many diagrams were incomplete.
Candidates failed to identify the component parts of the earth fault loop path and so lost considerable marks. A large number of marks are allocated to the labelling, or identifying in a written description, the component parts of the earth fault loop path as indicated in GN 3.

GN3 states the following elements of the earth fault current loop path:
The circuit protective conductor
The main earthing terminal and earthing conductor
For TN systems the metallic return path or for IT or TT systems the earth return path
The path through the earthed neutral point of the transformer
The source line winding
The line conductor from the source to the point of the fault

These are example diagrams with the parts of the EFLI identified as well, for understanding (Zs, Ze, R1, R2, R1+R2)

 

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Thank you . You.r a Star Richard . Outstanding . my friend .
This is what it is all about . A better understanding . 100%

 

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Useful Junk .

Residual current devices ( RCDs ) in TN systems

For a circuit using an RCD for fault protection, Regulation 411.4.5 requires that the product of the earth fault loop impedance (Zs) and the rated residual operating current ( I∆n ) of the RCD does not exceed Uo volts (V)
therefore follows that the maximum permitted value of (Zs) is given by equation : ( Zs = Uo / I∆n ) Ω

Where: ( I∆n ) is the rated residual operiting current of the RCD in amperes .

For a circuit of nominal voltage Uo 230 V supplied through an RCD having a rated residual operating current ( I∆n ) of 100mA (0.1 A), the maximum permitted value of (Zs) produced by equation : is 2300 ( 230 V 0.1 A ) = 2300Ω

100mA ÷ 1000 = 0.1A

10mA ÷ 1000 = 0.01A
30mA ÷ 1000 = 0.03A
300mA .
500mA . Etc

 

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" Continuity " Small rant .

(i) O.S.G. P/90 / 91 . 10.3.1.
(ii) GN-3 . 2.7.6. Continuity of ring final circuit-Conductor(s)
612.2.2. A three-step test is required to verify the ( Continuity ) of the , Line , Neutral , & Protective-conductors .

Step 1 . is end-to-end ( Ω ) measure the résistance of each Ring / Loop .. Identify
( Certification ) R/P.402 .. Schedule of test results . Ring final circuit continuity ( Ω ) 10 , 11 , 12 . Little ( r [SUP] 1 N 2[/SUP] )

Measurements taken at the Origin of an ( A1 ring circuit 100m[SUP]2[/SUP] ) O.S.G. table H2.1.
( r[SUP]1 [/SUP] = 0.4Ω ) .. T&E
( r[SUP]N [/SUP] = 0.4Ω ) ..
( r[SUP]2[/SUP] = 0.67Ω ) ..

Determine the measured value of résistance ( at each socket-outlet ) ends of the circuit are cross connected to form a ( Figure of 8 )

( Figure of 8 ) Step 2 . Connections for testing , Line & Neutral .
( Figure of 8 ) Step 3 . Connections for testing , Line & Circuit-protective-conductor . CPC

cross connection between Line & Neutral at origin ... measure résistance between Line & Neutral at each socket
cross connection between Line & CPC at origin ... measure résistance between Line & Circuit-protective-conductor at each socket

recap . GN-3 . tells us .

Line & Neural is measured at each socket-outlet , The ( Readings ) obtained at each of the sockets wired into the ring will be substantially the same & the value will be approximately one-quarter of the résistance of the line plus , CPC loop résistance . ( r[SUP]1 [/SUP]+ r[SUP]2[/SUP] ) / 4 .

Line & Earth is measured at each socket-outlet , The ( Readings ) obtained at each of the sockets wired into the ring will be substantially the same & the value will be approximately one-quarter of the résistance of the line plus , CPC loop résistance . ( r[SUP]1 [/SUP]+ r[SUP]2[/SUP] ) / 4 .

( r[SUP]1 [/SUP]+ r[SUP]N [/SUP]= 0.4 + 0.4 = 0.8 ÷ 4 = 0.2Ω ) line & neutral
( r[SUP]1 [/SUP]+ r[SUP]2 [/SUP]= 0.4 + 0.67 = 1.07 ÷ 4 = 0.267Ω ) line & circuit-protective-conductor .

The highest value recorded represents the maximum ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) of the circuit & is recorded on the Schedule of test results .

Note : A higher résistance value will be recorded at any ( socket-outlets wired as Spurs )

Note : R/P.402 . Where there are no spurs connected to the ring-final-circuit this value is also the ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) of the circuit .

The other test confirmed is : Polarity by Continuity method .

Three specific requirements for ( Verification ) of polarity with the regard to ( Accessories )
612.6. Polarity
(i) All single-pole devices are connected in the line conductor only .
(ii) The centre contact of Edison screw lamps . refer . ( LED lights are taken centre stage now ) 2 Dee ,
(iii) Wiring has been correctly connected to socket-outlets & similar accessories

( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) am single narrowed out ( R[SUP]2[/SUP] ) what has you achieved , you have verified , by test that must be carried out to confirm that your circuit-protective-conductors are continuous throughout you loop . .. under earth-fault-conditions your RCD will take it out

( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) am single narrowed out ( R[SUP]1[/SUP] ) what has you achieved , you have verified , by test you carried out to confirm that your line-conductors are continuous throughout your loop . *

612.6. Polarity
(i) All single-pole devices are connected in the line-conductor only * Circuit-breaker or RCBO . etc

GN-3 & BS-7671: have their merits of each test . nock on affect .

 

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State the action to be taken regarding the Earthing-conductor before measuring the résistance of an earth-electrode .
( Earth electrode testing ) ... Do not disconnect any protective-conductors before ( Isolating the supply )

Disconnect earthing conductor at ( MET ) to avoid parallel earth paths .

GN-3 : 2.7.12. Q/As

recap . Test method 1 .
before test is undertaken , the earthing-conductor to the earth-electrode must be disconnected either at the electrode or the ( MET ) to ensure that all the test current passes through the earth electrode alone .

This will leave the installation unprotected against earth faults .

 

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Useful Junk

Any surface potential ( V )

The potential ( V ) arising on an installation earth-electrode under earth fault conditions will have a value relative to the nominal voltage to Earth of the supply ( Uo ) as follows:

V = Uo x R[SUP]A[/SUP] / Zs (V )

Where :
( Uo ) is the normal voltage of the supply
( R[SUP]A [/SUP]) is the sum of the resistances of the earth electrode and the protective conductor connecting it to the exposed-conductive-parts
( Zs ) is the earth fault loop impedance of the faulty circuit

For example , suppose an earth fault of negligible impedance has occurred in a circuit of an installation in a TT system and suppose the nominal voltage of the supply ( Uo ) is 230V, the earth fault loop impedance ( Zs ) is 100Ω and the earth electrode resistance is 80Ω.

By substituting these values into equation : V = 230V x 80Ω ÷ 100Ω = 184V

it is found that the potential ( V ) appearing at the earth electrode is 184 V.

the duration over which the potential exists must be considered, account being taken of the fact that persons or livestock will generally be in contact with the general mass of Earth .

 

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Changes to existing electrical installations, such as additions or alterations

Regulation . 132.16 . What are they asking us for . Simple . Assessment of an Existing Installation

‘ No addition or alteration, temporary or permanent, shall be made to an existing installation, unless it has been ascertained that the rating and the condition of any existing equipment, including that of the distributor, will be adequate for the altered circumstances. Furthermore,

the earthing and bonding arrangements, if necessary for the protective measure applied for the safety of the addition or alteration, shall be adequate ’.

 

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Means of earthing :
The means of earthing is the arrangement through which a connection is made to the general mass of Earth .

 

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On small rant mode . Chief Examiner's report

Examples Only , Scenarios

• Additional lighting point (luminaire and/or switching) on a single existing circuit.
- Minor Works Certificate may be used provided the existing circuit protective device is suitable for protection of the modified circuit, and other safety provisions are adequate

Changes to existing electrical installations, such as Additions or Alterations . your Q . Overlooked
Existing circuit protective device is suitable for protection of the modified circuit .. make a statement

Chief Examiner's report , 2394 , lost marks
• Additional socket-outlet on a single existing radial or ring circuit
- Minor Works Certificate may be used provided the existing circuit protective device is suitable for protection of the modified circuit, and other safety provisions are adequate

• Replacement of an accessory, such as a socket-outlet or a ceiling rose, on a like-for-like basis

Changes to existing electrical installations, such as additions or alterations

( MEIWC ) Part 2 Installation details .
( 3 ) Protective devices for the modified circuit ... ( Type ........ Rating ....... A ) ◄◄◄ ( Protective devices )

Examples of work that falls within the scope of a Minor Electrical Installation Works Certificate . R/P.394

• the addition of a socket-outlet to a ring or radial final circuit
• work carried out on a lighting final circuit, including an alteration to the switching arrangements
• the addition of a lighting point or
• the replacement of an accessory or luminaire

work considered to fall within the scope of the Minor Electrical Installation Works Certificate, refer to the Minor Electrical Installation Works Certificate.

Note : that for the provision of a new circuit, the Electrical Installation Certificate must be used; Not the Minor Electrical Installation Works Certificate.

R/P. 196 , Any defects or omissions in the work covered by the Electrical Installation Certificate or the Minor Electrical Installation Works Certificate must be made good before the Certificate is issued ( Regulation 632.4 ) and before the installation is energised.

Minor Electrical Installation Works Certificate may be used only
where the work involves an alteration or an addition to an existing single circuit and where the work does not entail the provision of a new circuit .

Verification of the means of earthing
the earthing and bonding arrangements, if necessary for the protective measure applied for the safety of the addition or alteration, shall be adequate ’.

 

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How hard can it BE ??? 2394 / 5 .

Unit 301 - Multiple choice examination . 2013 / 14 .

This examination covers areas of knowledge & understanding which are common to both ( Initial verification ) & ( Periodic inspection )
This assessment is the same assessment for both qualifications & learners need only achieve the test once .

40 questions & 1 hour 20 minutes long ... Closed book examination

Outcome:
Understand the requirements for completing the safe isolation of electrical circuits & installation(s) .. N/questions ( 7 ) (%) - 18
Understand the requirements for inspection & testing of electrical installation(s) .. N/questions ( 2 ) (%) - 5
Understand the requirements for safe testing electrical installation(s) .. N/questions ( 11 ) (%) - 27
Understand the requirements for testing circuits which are not energised .. N/questions ( 7 ) (%) - 18
Understand the requirements for testing energised installation(s) .. N/questions ( 13 ) (%) - 32
Total .. N/questions ( 40 ) (%) - 100

Unit 302 - Written Examination
The examination papers for both qualifications ( 2394 & 2395 ) have the same format , They each have ( 6 structured ) qualifications & are 1 hour 30 minutes long . Each question is worth 15 marks .

 

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Your Q .

Structure of the exam .
Each paper is divided into two sections , Section A & Section B .

Section A of each paper has three-questions which are often divided into a number of parts ( a , c , & i ) ii) , iii ) & so on
with each part of the question relating to a different learning outcome , The number of marks available for each part of the question is shown on the paper & this can be used to indicate how long to spend on your answer .

Section B also has three questions, but these relate to the scenario contained within a " source " document . These questions may also be divided into parts but often relate to a single learning outcome . Candidates are expected to display an in-depth knowledge of the particular subject .

Note : 2394
►► Typical examples include ( DESCRIBING a TEST PROCRDURE ) or ( EVALUTING TEST RESULTS )

As the Chief Examiner , reminds us .

Knowledge of BS-7671
Guidance Note 3 &
Electricity at Work Regulations GS-38 is required by all candidates. Some candidates demonstrate little background knowledge and struggled with questions relating to the requirements of GS 38, the purpose of Initial Verification, the steps to take should a test fail and what the test button on an RCD does.

Chief Examiner (13) 2394: Chaps this is not a spin Off . from 2392/10 .. PS no written Exams .

The Chief Examiner is asking you . TO
Read carefully & answer what the ( Question actually Asks )

Often a question is answered ( INCORRECTLY ) because of a ( failure to UNDERSTAND ) what is being asked & what is required , it is an easy trap to fall into under exams conditions where you are under pressure .

Chief Examiner Report . is for a reason . Learn by our mistakes'

The danger here is that you may answer a question to which you know the answer , ( But ) which is not the question you have been asked in the paper ( 49% ) Remember , the questions are set to ( Establish your level of understanding in specific areas ) so the correct response is important if the marks are to be obtained ,

Chief Examiner Report . Learn by our mistakes'
Take a little longer to READ the QUESTION carefully to ensure you are quite clear about what is required .

 

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Where am I going Wrong !!

Chief Examiner : 2394 : Wording of Questions :

I will not download this again , ◄► Take heed

Coupled with the number o marks available . gives valuable clues as to what is expected , the words used in the question provide the first clue . if you look out for the following words & phrases & understand what they mean , you should be able to provide an appropriate answer .

Meanings : C&Gs

State :
The means the answer is expected to be a short statement , not a long or ( RAMBLING PARAGRAPH ) The response to this type of question may even be just a single word or group of words which may not be need to be a complete sentence .

List :
This means you should produce a simple list of items or actions , The answer should be similar to that produced for the " State " question , however ,
on this occasion the items would be expected to follow a sequence & form a list , as would be expected for a shopping trip .

Explain briefly :
This requires a brief explanation ; usually no more that one or two sentences . it does not require paragraphs of explanation & the word " briefly " is used to indicate this requirement .

Explain with the aid of a diagram :
This means exactly what is says . The answer should comprise both a diagram & an explanation , The examiner is trying to help you achieve maximum marks by asking for both an explanation & a diagram because this method of providing information is likely to be the most efficient .

Show all calculations :
Again the examiner is tying to help you score as many marks as possible, Where a calculation is required & the only thing offered by the candidate is the numerical answer , then if it is wrong , the candidate would score no marks . if the candidate includes each step of the calculation then marks will be awarded for each correct step . it is always in your best interest to show all stages of the process , Where relevant remember to show the applicable units which apply to your answer e.g. ( V , Ω , kA ) etc .

With the aid of a fully labelled diagram :
This indicates that a diagram needs to be provided with the component parts clearly labelled , The marks for these questions are divided between the diagram & the labelling .

To obtain the maximum marks for the question both the labelling & the diagram must be completed

Describe :
These questions often relate to test procedures & you are required to demonstrate your knowledge of the test process , look at the number of marks available to give you an indication of how much detail you need to go into .

Describe , in detail :
This indicates that a more detailed answer is required & again the number of marks available for the question gives an indication of the depth of the answer required

A series of short bullet pointed statements is a very effective method of providing an answer , but remember that all necessary information must be included

Direct measurement :
This indicates that a test is required & the results are not to be established by using a calculation . For example , where you are asked to describe the direct measurement of earth-fault-loop-impedance , ◄► Take heed
then a description of the test procedure is required , Describing an ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) test & then stating how to determine the value by calculation using , Zs = Ze + ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) will result in no marks being awarded for the answer .

 

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Terminology : ( When things go Pear Shape )

The simplest of mistakes will cost you . " marks "

it is important to answer questions using the correct terminology , which is the same as that used in GN-3 & BS-7671:2011:

Chief Examiner has given you a reasonable explanation . ( Why ) Always use correct titles & terminology .
Brand names should ( Not ) be used to describe items of equipment . test instruments & the like .

Chief Examiner , example
the instrument used to test for continuity is a low résistance ohmmeter . it should not be referred to using a manufactures name ( Megger ) or referred to as a continuity tester .

This is because the precise performance requirements given in BS-7671: & GN-3 must be Met . ◄◄

Some continuity testers & instruments that provide continuity features may not meet these requirements.

Your Q . ▼ Here's you reason .
Multifunction test instruments are commonly used for testing electrical installations . You need to be aware of the individual functions & ranges of these instruments , This includes such functions as insulation résistance , continuity , earth fault loop impedance & prospective fault current measurement .

The appropriate measurement scale for a particular test must be clearly stated , Also be careful to use the correct units & symbols to describe test instrument readings , ( mΩ , Ω , MΩ , A , kA , mS )

The use of the correct terminology for the component parts of an electrical system is also important .
The application of the terms used in BS-7671: is necessary as this leaves no doubt as to the part being described . typical terms , includes earthing-condutor , main-protective-bonding-conductors & circuit-protective-conductors , Terms such as ( earth wires or cross-bonding ) do not correctly identify components & the examiner is unable to award marks for such items .

Another common error is the use of incorrect titles for documents , if you refer to the " Electricity at Work Act " instead of the " Electricity at Work Regulations " or the Health & Safety at Work Regulation's instead of the " Health & Safety at Work Act " this will result in no marks being awarded. this also applies to the title of documents which are completed during the inspection & testing process & handed to the client .

 

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Section ( B )
Each paper is related to a scenario which is given in the Source Document .

The scenario gives details of an electrical installation , or part of an installation . it identifies what is to be carried out , & provides information that is to be used to answer the final three questions on the exam paper . This means that the answer to these questions should relate to the installation indentified in the scenario .

The most common error made by candidates at this point in the paper is failing to ( READ ) the scenario & apply the information given to these final three questions .

scenario , clearly states a TN-C-S system is used & a question asks for a diagram of the earth fault loop path , producing a drawing of a TN-S system will result in no marks being awarded . Etc

Common errors : when answering questions that relate to the scenario .
- not obtaining permission for isolation or for testing to proceed .
- no isolation procedure mentioned when it is appropriate
- no instrument & lead check carried out
- incorrect procedures described , such as not being able to describe the three steps in GN-3 for ring final circuit continuity
- not describing the test process in the correct sequence
- failure to consider the safety aspects necessary for the testing process
- failure to reinstate the installation safely once testing is complete

You are expected to be able to describe the procedures for carrying out activities , including the inspection & testing of installations & circuits , These descriptions should follow the format given in GN-3 .

 

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Written Examination 2395 . Q/As ( 1 )

(i) The electrical installation in a craft workshop is scheduled for a periodic inspection & test for insurance purposes .
a) State two statutory documents which apply to the inspection & testing process

A) Electricity at Work Regulations .
A) Health & Safety at Work ( etc ) Act .

Comments .
Abbreviations such as EWR & HSWA are acceptable . candidates must correctly identify whether these are an Act or Regulations in order to achieve the marks .

1 b) State three non-statutory documents which the inspector may need to refer to relating specifically to inspection & testing

BS-7671:
On - Site Guide
Guidance Note

Comments
GS-38 is an acceptable alternative so any three from these four are acceptable . Abbreviations such as OSG. & GN-3 are also acceptable answers . As the question asks for three items , the examiner will only mark the first three responses .

1 c) State who the inspector will consult to establish the extent & limitations of the periodic inspection & test
A) The client
A) The insurance company
Comments The person ordering the work or the person requesting the work are acceptable alternatives to the client . note Read the question carefully , the main question stem specifies that the work is for insurance purposes.

The response must relate to the insurance company & so other interested third parties or any other specific third party such as licensing authority etc will not receive a mark .

1 d ) Explain why the sequence of testing for the periodic inspection may be diffident to that given in BS-7671: for initial verification
A ) The installation has been inspected & tested & placed in service . Periodic inspection verifies the current condition or the safety of the installation 7 not the confirmation of the safety of the installation before placing in service

Comments
The candidate needs to explain the purpose of periodic inspection & how this differs from initial verification in order to obtain the marks, Examiners will consider the description used & whether this explains the reason for there being no sequence for the periodic tests . Answers such as inconvenience & because the installation is energised are not acceptable as these do not affect the sequence of testing but relate to the extent & limitations agreed with the client .

Tip . Many candidates confuse the sequence of tests with the sampling of the installation , sampling does not relate to the sequence , BS-7671: gives a required sequence of tests to be carried out at initial verification , All these tests could be carried out at periodic inspection but not necessarily in the same sequence . The answer needs to clarify why this is the case .

Chief Examiner had a field day with this ONE .

1 e ) State the first action to be taken by the inspector should an exposed live part be identified on a socket outlet circuit during the inspection
A ) Make a recommendation to the responsible person that the circuit is isolated until a repair can be carried out .

Comments
A ) Alternative answers include ;
inform client & obtain permission to isolate until repair can be carried out
Or
Isolate with the clients permission until a repair can be carried out .

Notes :
Isolate the supply & record the results , & similar answers are not acceptable as the inspector is required to inform 7 recommend the isolation . Not to carry out the isolation without first seeking agreement from the Client / User .

Guidance Note 3 , in the general requirements section , identifies the action to be " recommend the immediate isolation of the defective part "
The person ordering the work should be informed , in writing , of this recommendation without delay ,

 

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2 a ) A periodic inspection is to be taken in a hotel fitness room .
i) State three checks that need to be carried out to avoid damage to equipment before an insulation résistance test is conducted .

Comments :
Alternative answers include ; ensure no connection between live conductors & earth or link out controls .

As the question asks for three items , the examiner will only mark the first three responses .

2 a) ii) State the test voltages to be applied for the insulation résistance test

A) 500V
2 a) iii ) State the effects on the value of insulation résistance produced by cable length .

A ) As length increases resistance decreases

Comments :
An alternative answer includes as length decreases résistance increases .
Alternative terms such as higher or lower are acceptable

2 b) Insulation résistance tests between live conductors & earth on the individual circuits produced the following results , 200MΩ , 200MΩ , 150MΩ , 50MΩ , 25MΩ , 100MΩ , 2MΩ .

Calculate the expected overall value of insulation résistance if the installation was tested with ( with all the circuit connected )

Show all calculations .
A)

1/Rt = 1/R1 + 1/R2 + 1/R3 + 1/R4 + 1/R5 + 1/R6 + 1/R7

1/RT = 1/200 + 1/200 + 1/150 + 1/50 + 1/25 + 1/100 + 1/2

1/RT = 0.005 + 0.005 + 0.007 + 0.02 + 0.04 + 0.01 + 0.5

1/RT = 0.587

RT = 1.7MΩ

Comments :
Either the formula or the figures are acceptable for the first line . The correct units must be included in the final answer to obtain the marks .

Tip : it is important to show all the calculations' used to arrive at the answer as should an error be made the marks lost will relate just to the error whereas providing just the answer or omitting some calculation stages together with obtaining the wrong answer will result in all the marks being lost .

2 b ) ii) State , given reasons , whether the insulation résistance for the installation complies with BS-7671:
A ) 1.7MΩ ≥ than minimum 1MΩ & so it complies .

Comments :
Candidates need to explain the reason for their answer so simply " yes " would only receive 1 mark .

The response to Part (ii) of this question is dependent on the answer to the candidates response to Part (i) if the candidate has an incorrect answer in (i) this will not affect the marks awarded in (ii) The examiner will mark (ii) based upon the answer given by the candidate in (i)

 

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2394 : Inspection & Testing : Q/As . your turn , your call .

A test of continuity of the ring final circuit supplying the stages area socket-outlets is to be carried out .

i) State the test instrument to be used for the test .
ii) State ONE check to be made on the test instrument before carrying out the test other than calibration
iii) State the action to be taken with the test leads before the test is carried out . Remember this one .