***Cont../ Useful Information for Electricians & Apprentices***

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411. Protective Measure – Automatic Disconnection of Supply. ( ADS )

2392-10. Threecomponents . ◄► FaultProtection .

411.3.1.1. Protective Earthing .
411.3.1.2. Protective Equipotential Bonding .
411.3.2. Automatic disconnection in a Case of a Fault.

“ Second Digit “ [ IP ]
2 ] Protection against dripping water when tiltedup to 15% .
4 ] Protectedagainst splashing water .
5 ] Protected against water jets . .
6 ] Protected against heavy seas .
7 ] Protected against the effects of - [ Immersion]
8 ] Protectedagainst complete - [ Submersion ]

Definitions. for degrees of protection provided by enclosures of electrical equipment as:

i) Protection of person against access to hazardous parts inside the enclosure .
ii)Protection of the equipment inside the enclosure against ingress of solidforeign objects .
iii) Protection of the equipment inside theenclosure against harmful effects due to the ingress of water .

 

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Protection Against Overcurrent .
Regulation. 131.4.

TheElectricity at Work Regulation 1989 =Part 11 . “ States “
That “ Efficient “ means . suitably located . shall be provided for protecting from “ Excess “ of current every part of the system as may benecessary to prevent danger .

Regulation . Reinforces this . 131.4. States that “ Persons & Livestock “ . shall be protected against injury. & property shall be protectedagainst damage .
Due. to excessive temperatures orelectromagnetic stress caused by Overcurrents . likely to arise in Live conductor’s .

2392-10: 131.2.2.. NOTE:
Inconnection with fault protection . the application of the method of protectiveequipotential bonding is one of the important principles for Safety .

ProtectionAgainst fault current :
Regulation. Reinforces this . 131.4. States that “

TheElectricity at Work Regulation 1989 =Part 5 . “ States “
That “ NoElectrical “ equipment shall be put into use where it’sstrength & capability may be exceededin such a way as may give rise to danger .

Regulation 131.5.
Whichrefers to any [ conductor(s) ] being able to carry fault current withoutgiving rise to excessive temperatures . ( inAddition )
Anyitem of electrical equipment intended to carry fault current shall be providedby mechanical protection against electromagnetic stress which could result ininjury or damage to persons . livestockor property . .

Niceone Bruce .

 

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Hospitals’: 2011.

-&-s. Q) The connecting of a Mobile Generator ? . this may be achieved by a [ Plug-in-facility ] BS-EN-60309 - Socket
p/283: BS-EN-60309 : Plugs . sockets-outlets . & couplers forIndustrial purposes . Table - 54.4. [ 551.4.4.note ]

Regulation p/171: - 551.4.4 . NOTE : for suitable connection arrangements see . BS-EN-60309 - Series .

!!!. Do I Need . An External earth leadconnection to the Generator Star . ??

 

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Explain the terms

a. Earthing : p/27
b. Bonding Conductor. : p/23 . A protective conductor providing Equipotential Bonding .


lets Open it Up .

Solution
a. Earthing: connection of the exposed conductive parts of an installation tothe main earthing terminal of that installation.
b. Equipotential Bonding . Electrical connectionmaintaining various . exposed-conductive-parts &extraneous-conductive-parts at substantially the same potential .

Wording: “ Meanings “
Twotypes of [ Bonding ] normally used are

• Main protective bonding . &
• Supplementary protective bonding . [ where required ]

Main protective bonding – is alwaysrequired .
Reasons: Bonding reduces the voltage theremight have been .

[MET ] A terminal block . where Earthing & Bonding conductor(s) are connected together . Etc

Protective Equipotential Bonding – 411.3.1.2.
Ineach installation . Main protective bondingconductors . shall connect to the [ MET ] ► Extraneous-conductive-parts including the following .
i)Water installation pipes .
ii)Gas installation pipes . Etc .

Bonding– the correct title is ‘ Equipotential bonding ’. ‘ Electrical connection maintainingvarious exposed-conductive- parts and extraneous-conductive-parts at substantiallythe same potential ’

 

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Ohm’sLaw .
Thecurrent in Amperes ( I ) is equal to theelectromotive force . Or Voltage ( V) divided by the Résistance ( R ) inohms .

Current (I) = Voltage (V) / Résistance ( R ) : I =V/R .

CurrentFlow - System voltage & Loadrésistance determine the flow of current.
ShortCircuit - Accidental connection createsfault . During a Short-circuit . onlythe résistance of the fault path limits current . Current may increase to manytime’s the load current .

Overloadis defined as an Overcurrent that is confined to the normal current path . “Excessive “ connected loads . ( StalledMotor’s ) Can Overload a circuit .
Mostconductors can carry a moderate Overload for a [ Short duration without damage]

Start-upOr Temporary Surge Currents : Motor’s . Transformer’s.
Overcurrents protection must be selected that will carry thesecurrents . MCB .

Short-circuitis any current not confined to the Normal path.
The “ Term “ comesfrom the fact that such current’s. bypass the normalload . Etc . Short / path around the Load . When a current isGreater than . normal current .

[ Short-circuit’s. ] are usually caused by Accidental contact Or wornInsulation . damage occurs . Facts. [ Moreserious than Overloads ]
[ Short-circuit’s. ] include two Or more conductors accidentallytouching . Short-circuit / Fault currents.

Typesof Electrical Fault’s :
Overcurrents– can be divided into two categories . Overloads / Short-circuits .
Anyelectrical current that “ Exceeds “ therating of the circuit is an “Overcurrent “

Or worn Insulation . damage occurs .
ATest that can be take for Granted . youwill get this on your 2392-10 . practical
Theimportance of this test . is that you could have damaged your cable duringInstalling it .

632.4. Defects or omissions revealed duringInspection & Testing of the Installation work . Shall be made good beforethe Certificate is issued .

p/31 : Origin of anInstallation : The position at which electrical energy isdelivered to an electrical installation .
p/24 : Circuit An assembly of electrical equipment supplied from the same Origin &protected against Overcurrent by thesame Protective device(s)

p/25 . Circuit breakers: .
Circuitbreakers : are designed to protectcircuits from Overloads &Short-circuits conditions . When applied within their ratings .
MCB. is connected to an electrical circuit& acts as a bridge between the circuit & the power supply .
MCBs. are designed to protect electrical circuits from being Overloaded .
Calculatea Watt-load for circuit breakers . 10A x 230V = 2300W .

 

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• Surge current Or Inrush current . the maximum .instantaneous input current drawn by an electrical device when first turned on.

• BS-7671:2011 . put specific responsibility onthe Installer . 510.3 . requires that the Installer takes intoAccount the Manufacture’s Instruction’s .

 

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Faultcurrents to be considered include faults between Line conductors & Earth .Line conductors & Neutral . & Line to Line conductors .
most domestic installations the ( PFC ) the value canexceed until 6kA . up to which value the ( Icn & Ics ) values are the same.
highestfault currents will arise with Three-phase Line conductors shorting together & to Earth .

 

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Just a reminder .

So where does this [ 0V ] or[ Zero ] potential come from . The Earth .
p/26 . Earth .
The conductive mass of the . Earth .whose electricalpotential at any point is conventionally taken as [ Zero ]

 

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Just a reminder . 2392-10 .
Earthing matters will come up in Exams .-&-s

Conductors used in such connections . are called “ Protective Conductors “ . & theycan be . subdivided .

Domestic Installations - Circuit protective conductors . CPC. For connectingexposed-conductive-parts to the [ MET ]
Domestic Installations - Main protective bonding conductors . for [ Bonding] together main incoming services .

 

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• Whencompleting Additions to a circuit such as an extra socket

a. state the type of Certificate to be issued
b. list three items of information that need to be entered on the form
c. state to who the form should be given.

Solution

a. A Minor Electrical Installation Works Certificate.
b. (i)- Details of the existing installation . (ii)- Description of the minorworks . (iii)- Essential Tests / Test results.
c. The person ordering the work.

Q/As . it’s all you need to know to passyou on your Exams . 2392-10 . :banghead:

 

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( MEIWC )
Minor ElectricalInstallation Works Certificate . are used for . “ Minor Works “ Only .

It come under this . Certification & Reporting : Regulation aretelling you the [ Answer’s ] :13:

Notes p/394 :
Minor WorksCertificate is intended to be Used for . Additions & Alterations .to aninstallation that Do Not Extendto the provision of a New Circuit .

Minor ElectricalInstallation Works Certificate. Q) Inspecting & Testing shouldalways be carried out . A) Irrespective of the extentof the work undertaken .


Let’s open it Up . Q/As -&-s .

Q) state to who theform should be given. A) The personordering the work . 2392-10 :

P/394 : ( To be appended to theCertificate )

2392-10 . You : should havereceived an “ Original “ certificate & the contractor should have retained a ( Duplicate )
if you were the person ordering the Work .

►► “ BUT “ not the Owner of the installation . “ You “ should pass this Certificate . Or a copy of it . to the “ Owner “

Point to NOTE here . MinorElectrical Installation Works Certificate.

2392-10 . -&-s are looking for . The right Certification& Reporting : for the Job .

This Certificate isNOT appropriate if yourequested the “ Contractor “ to undertake more [ Extensive Installation Work ]
For which youshould have received an [ Electrical InstallationCertificate ] EIC .

Regulations . are saying that ? you cannot use a Minor Certificate for Major Work . Etc .

Minor ElectricalInstallation Works Certificate. Notes . : are used for “ Minor Work “ that Do Not Extend to a New Circuit .

p/394 . Regulation aretelling you the [ Answer’s ]

□ The addition of a socket outlet to an “ Existing Circuit “
□ The addition of a Lighting point to an “ Existing Circuit “
□ Relocation of a light switch .
□ Can also be used for the replacement ofaccessories & luminaries .

□ NOT : for the replacement of distribution boards Or similar items .

 

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Part 4: Declaration

I/We CERTIFY that the said works do not impair the safety of the Existing Installation, that the said works have been designed, constructed, inspected and tested in accordance with BS 7671:2011…(IET Wiring Regulations), amended to……………………(date) and that said works, to the best of my/our knowledge and belief, at the time of my/our inspection, complied with BS 7671 except as detailed in Part 1.

( MEIWC)

 

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Inspection& Testing : 2392-10 : 2011 . -&-s . “ InitialVerification “

Ifthe Inspection & Tests . are Satisfactory . a signed ( EIC ) 631.4 . together with a . Schedule of Inspections .& a Schedule of Test Results . 632.1 .
( Asin Appendix G ) are to be given to the person ordering thework . 632.3.

▲ (EIC ) p/391 . Bottom page . Regulations are telling you the Answers. 2392-10 .
Schedules : The attached Schedules are part of this document & thisCertificate is valid only when they are attached to it .
………….. Schedules ofInspections & ………… Schedules of Test Results are attached.

 

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InspectionProcess . “ Wording “

VisualInspection . 2392-10 :

Wesee the words : Omission ?? . of appropriate sleving on Lighting Switch conductors &Two-way lighting strappers .

 

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Remember - aLive conductor includes the Neutral also .

2391-10: prepare for taking the Exam .

Studentmust be aware of the correct use of Terminology when Answering Questions .Marks will be lost for Incorrect Use . “Nil Pwa“ - No points

Using: Completion Certificate “ instead of . ( EIC) Electrical InstallationCertificate .
Using: Electrical Inspection Certificate “ instead of . ( EIC ) Electrical Installation Certificate .
Using: Initial Inspection Certificate “ instead of . ( EIC) Electrical InstallationCertificate .
Using: Minor Work Certificate “ instead of . ( MEIWC ) Minor ElectricalInstallation Works Certificate . ◄► This is myFull Tile . Exams

2392-10:
Thisdocument is made up of Three-parts : ( 1. EIC ) 2 . Schedule of Inspections : 3. Schedule of Test Results : Exams .

( EIC ) ThisCertificate must be issued for a completely new Installation .
( EIC ) must beaccompanied by a Schedule of Test Results & a Schedule of Inspection .Without these two documents . the ( EIC ) is notValid . p/392– ( 2) ****

An Inspection & Test which is carried out ona [ New Installation ] to prove compliance is called an [ InitialVerification ]
p/395: Schedule ofInspections – ( forNew Installation work Only )

[ Initial Verification Inspection]
Thisdocumentation which should be completed is the . Electrical InstallationCertificate . ( EIC ) this must be accompanied by a Schedule ofTest Results & a Schedule ofInspection .

Thecertificate issued for an Initial Verification must be accompanied by aschedule of : ????
a.Test results only .
b.Inspections only .
c.Tests & schedules of inspections .
d.Schedule of inspections . & Schedules of test results . “ take your best Shot “ :icon_bs:

“ Facts“
▲ (EIC ) p/391 . Bottom page . Regulations are telling you the Answers. 2392-10 .
Schedules : The attached Schedules are part of this document & thisCertificate is valid only when they are attached to it .
………….. Schedules ofInspections & ………… Schedules of Test Results are attached.

 

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Allinformation given by myself on these forums is used at entirely your own riskand is not necessarily the view of www.electriciansforums.net.

Justfor reading “ purposes “

ExtractFans in Bathrooms & Shower rooms .

- Ameans of Isolation to enable the fan to be separated from the source of energybefore gaining access to Live parts .
Themeans of Isolation would be provided by the device at the Origin of the Circuit. MCB – BS- EN 60947-3 Fan Isolatormounted adjacent to the fan

BS-EN 60947-3 . applies to switches . disconnections. switch- disconnections . & fuse-combination units to be used in distribution circuit & motor circuits of which the rated voltage does notexceed 1000V . a.c. or 1500 d.c.

-A means of switching off the fan for the purposes of Mechanical maintenance .cleaning .

BS-EN 60947-3 . fan Isolator mounted adjacent to the fan would fulfil therequirement for switching off for Mechanicalmaintenance . Regulation – 537.3.2.4. .requires the open position of the contacts of such a switch to be clearlyindicated .

-A functional switch to enable the fan to be switched “ On “ & “ OFF “ this functionalswitch may not be required where a . humidistat is used as a means of control .

Any suitable switch in table 53.2. of BS-7671:2011 would fulfil the requirements forthe functional switching . for such rooms without a window the fan is usuallyconnected to the light switch . Or a separate switch provided for rooms with awidow .

□ ExtractFans with a “ Run-on “ timer & / or humidistat .

BS-EN 60947-3 . fan Isolator .
Mountedadjacent to the fan would provide the appropriate means of switching “ OFF “ for Mechanical maintenance . Where theisolator switches both the switch wire & permanent Line conductor this would also provide a meansof [ Local Isolation ] where access to Live parts is required . the isolator should be located adjacent to the fan out with .Zones 0. 1.& 2 in accordance with Section 701of BS-7671:2011

Note; Such isolators also permit the Neutral conductor to be isolated .

□ ExtractFans without a “Run-on “ timer & / or humidistat .

Fanswhich are simply controlled by afunctional switch we would also recommend a BS- EN 60947-3 . fan isolator mounted adjacent to the fan as above. to provide the appropriate means of switching “ OFF “ for Mechanicalmaintenance . & local isolation . this is particularly important ifthe functional switch is mounted outside the room . consequently out with thecontrol of the person working on the fan .

ElectricalFixtures . Building Standards . requires that these fixtures can be Operated Safety .

P/286: BS-EN 60947-3 . – 533.1. 2011 .

 

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Methodsof determining ( Ze )

Threemethods : Calculation . Enquiry . Measurement . must be used todetermine ( Ze )

Thedeclared maximum values of ( Ze ) & ( PSCC ) at the Origin .
230VSingle-phase & 230 / 400V Three-phase .

Characteristic: External Earth Fault Loop Impedance . ( Ze )
TN-S- 0.80Ω .
TN-C-S– PME . 0.35Ω .
TT- 21Ω .
Prospective Short Circuit Current ( Isc ) at theOrigin . [ Single-phase supply - 16.000A ] ……….. ( Isc ) meaning . p/38. A .
Prospective Short Circuit Current ( Isc ) at theOrigin . [ Three-phase supply - 25.000A ]

Themaximum values of ( Ze ) & (Isc ) declared by an electricity distributor are based on opposite suppositionsconcerning the impedance of the supplyto an installation . & cannot therefore be expected to occur at the sametime .
Inparticular . the maximum values of ( Ze) are based on the supply of higherimpedance – such as one employing long runs of low voltage cable & a distributiontransformer of lower ( kVA rating ) & the maximum values of ( Isc ) are based on the supply of lower impedance –such as one employing short runs of low voltage cable & a distribution transformerof higher ( kVA rating )

Thedeclared maximum values of ( Ze ) & (Isc ) can . in this case of a . TN-C-S system . be used to estimate the maximum value of ( Ze ) liable to occur in normal circumstances .& hence to determine the range of the possible values of ( Ze )

Example. Consider a Single-phase supply of nominal voltage . 230V . to aninstallation forming part of a TN-C-S system . where the electricity distributor declares a maximum values of ( Ze ) as 0.35Ω & (Isc ) as 16.000A . By Ohms law . it can estimated that .
When ( Isc ) is at is maximum value of 16.000A . ( Ze ) willbe at its minimum value of . 0.014Ω - givenby 230V ÷ 16.000A . therefore . in this case . the normal range of valuesof ( Ze ) should be taken as [ 0.014Ω to 0.35Ω ] in the absence of better information .

Themethod of estimating the minimum value of ( Ze ) given in the Example .strictly applies only to a TN-C-S system . Although it can generally be usedwith reasonable accuracy for a TN-S system also .

Note: Calculator - 230V ÷ 16000 = 0.014 )

The reason why the method referred to inthis Example strictly applies only to a TN-C-S system . is that it uses the maximum [ prospective short – circuit current ] at the Origin .
Onthe assumption that this is equal to the maximum [ prospective earth – fault current ] at the Origin .
- upon which the minimum value of ( Ze ) really depends . Only for a TN-C-S system is the assumptionfully justified . this is because the short – circuit & earth – fault currents in such a system share a common path in the distribution network . due tothere being a combined protective & neutral ( PEN ) conductorin the network . the assumption is only approximately true for a TN-S system . which uses separate protective & neutral conductors throughout .

Enquiry. like calculation . does not verifythat the intended means of earthling is present or that the value of ( Ze ) iswithin the expected normal range therefore . confirmation of theserequirements by measurement is still required before the installation isEnergized .

 

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Sinks .Domestic : Domestickitchens, bedrooms and cloakrooms (unlike bathrooms and shower rooms) are notincluded amongst the special installations or locations in Part 7 of BS 7671 and are not rooms where the resistance of thebody is likely to be significantly reduced. Therefore, normal precautionsagainst electric shock should be adequate and the general rules of BS 7671 are applicable. However,whilst BS 7671:2011 does not forbid the installation of asocket-outlet or other accessory close to a sink in a domestic kitchen, bedroomor cloakroom, the requirements of Regulation 512.2.1 have to be taken into account. Therequirements of Regulation 512.2.1 mean that ordinary BS 1363socket-outlets and similar accessories are not suitable to be installed soclose to sinks or draining boards that they are likely to be splashed withwater or operated with wet hands. Thepenetration of water into an accessory could have serious effects. Waterentering the terminals and mechanism may lead to corrosion, internal arcing,general degradation and eventually malfunction. Additionally, and moreseriously, water may provide a track for the line voltage to be transmitted tothe front cover of the accessory, giving rise to the risk of electric shock.
512.2.1. ‘Equipment shall be of a design appropriate tothe situation in which it is to be used or its mode of installation shall takeaccount of the conditions likely to be encountered.’
A rule of thumb recommendation for domestic premises, to avoid theeffects of splashing, is that ordinary BS 1363socket-outlets and similar accessories should ideally be mounted not less thanabout 300 mm (ideally not less than about 1000 mm), in the horizontal plane,from the extremity of a sink top or wash basin.

 

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“ Definitions“

A “ wiring system “ & “ Conduit “ are defined in part 2 – 2011 .

Wiringsystem “ p/36.
Anassembly made up of cables or busbars . & parts which secure & . if necessary. enclose the cable or busbars .

Conduit“ p/25 .
Apart of a closed wiring system for cables . in electrical installations . allowing them to be drawn in & / orreplaced . but not inserted laterally .

Steelconduit forms part of a wiring system .

- PEN conductors :

Steelconduit must not be used as a combined protective & neutral ( PEN ) conductor . Regulation 543.2.10 .States .
543.2.10 . – A separate metalenclosure for cable shall not be used asa PEN conductor .

Restrictionson Use .
BS-7671:2011. places restrictions on the use ofSteel Conduit .

LiftShafts .
No cable or conduit is to be run in a lift ( orhoist ) shaft unless it forms part of the lift installationas defined in BS- EN 81-1 – Regulation 528.3.5. refers .
Apermitted exception is equipment relating to the lift installation . such aswell lighting . which commonly utilises conduit.

 

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EarthFault Loop Impedance :

A limiting value of earth fault loop impedance . isspecified in the ( ADS ) requirements for TT system under two circumstances.

Wherean RCD . is used for fault protection .
Wherean Overcurrent device . is used for fault protection .

ProtectiveMeasure ( ADS ) for a TT system.
Asfor other types of electrical system . the magnitude & duration of voltagesbetween “ simultaneously accessible “ Exposed-conductive-parts . & Extraneous--conductive-parts . occurring anywherein a installation during an Earth Fault . ADS , achieves this coordinating thecharacteristics of the protective device for automatic disconnection . the earthing arrangements for the installation& the relevant impedance of the circuit concerned .

BS-7671:2011 . States three fundamental requirements for “ Fault Protective “ by ADS in a TT system .
- Protectiveearthing - Regulation / 411.3.1.1.
- Protective equipotential bonding . - Regulation / 411.3.1.2.
- Automaticdisconnection in case of a Fault . - Regulation/ 411.3.2.

Protectivedevices :

Faultprotection . 411.5.2. requires on ormore of the following types of protective devices shall be used . the “ Former being preferred “
- RCD.
-Overcurrent protective device such as .Fuse or Circuit breaker .