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

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O.S.G.. The use of other methods’ of determining Maximum Demand is Not Precludedwhere Specified by the Installation Designer

FirstlyI make no Apologies for the Way am Writing on any Matters . it can be a first day Apprentice or some one Needing aJog of Memory .
Sowe are all in the Same Boat . “ To Learn “

For the Apprentices . The Day we stop learning is the Day we hang Upour Tool-Bag

CookerDesign Current Calculations

Thefirst thing you have to do is get Your Head around the Calculations !!

(From a Design point of View ) 2392-10

DomesticInstallation Oven(s) & Hob(s) are to be Calculated upon their MAXIMUM LOADING
Startwith a simple Calculation ( An Oven has a rating of 2kW ) 2000

(I = P/V ) Formula … I = 2000 ÷ 230V = 8.70A …. Weare Using the Unit Amps


2392-10/ Domestic Installation Oven(s)

Ovenhas 4 Rings ( 2 x 1kW ) & ( 2 x 1.5kW ) & Grill ( 2kW ) & Oven (3kW )

-Controlled via a CookerSwitch with a Socket outlet .

Asa Designer . we’ll have to Apply Diversity ??

Important )- Diversity allowance to be Applied to the FULL LOAD CURRENT for CookingAppliances .

TheO.S.G. is telling us . Purpose of the Final Circuit fed from theConductors )
O.S.G.Table 1B p/97 – column (3) Cooking Appliances → At the Top of the Page Note : Type ofPremises ( 2392-10 → Household Installations ) Domestic Installation(s)

DomesticInstallation(s) Only O.S.G. - 10A + 30% f.l – Full Load ) of connected Cooking Appliances in the Excess of 10A+ 5A if a socket-outlet is incorporated in the Control Unit . ( C.C.U. ) – 45A + 13A Socket Switched with Neon .

Fromyour point of View ( The First 10A ofthe rated current plus 30% of the reminder ( Plus) 5A if the Control Unit incorporates s Socket.

Calculations)- You bank “ Hold OFF“ the first 10 Amps of the Maximum Load Current )
The10A will be used at the End of the Calculations’

-So your Work out the Total Power Rating & then calculate the Full Load Current

Calculations)- Power = ( 2 x 1 ) + ( 2 x 1.5 ) + ( 2+ 3 ) = 10kW

I= 10000 ÷ 230V = 43.48A … round it up to the first four numbers43.47826087 ( 48 ) 43.48A

UsingDiversity allowance stated ↑↑ ( 43.48A sub 10A = 33.48A )

I= 33.48 x 30 ÷ 100 = 10.04A

Youradding the ( 5A ) for Socket outlet . I = 10A + 10.04 + 5A = 25.04A )- Asa Designer this is your Expected Current Demand .

Remember )- Supply Cables Rated to suit DesignCurrent ( Iz )

 

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Testing . .

ElectricalInstallation Condition Report . ( EICR )
634.1.
Amendment No 1 –BS07671:2008 . reporting of periodicinspection & testing .

Full . ( EICR) documentation comprises .

ElectricalInstallation Condition Report .
&
Schedule ofInspections ( one or more )
&
Schedule of Test results . ( one or more )

Exams : On completion of . periodic inspection &testing . this ( EICR ) & itsaccompanying . Schedule of Inspections .& Schedule of Test results . mustbe given to the . Client or Person . who ordered the Inspection .

634.2.
A most importantpoint to . remember is that any damage . deterioration . defects . Part 2- dangerous conditions &non-compliance with BS-7671: that may give rise to danger ( danger being a riskor injury to persons or livestock ) mustbe recorded on the report .

 

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Testing . . 2392-10 . Exam’s Q/As

EarthFault Loop Impedance Testers:

ETC. : To minimise . Electric Shock . hazard from the potential of the protectiveconductor . the [ Test durationshould be within safe limits ] this means that the . instrument should cut [ OFF ] the test current after [ 40mS ] or atime determined by . the safety limits .

EarthFault Loop Impedance Testers: Exams : BS-EN-61557-3 .

 

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InitialVerification – ( Inspection & Testing ) forms .

Following an . InitialVerification . or [ Additionor Alteration to an ExistingInstallation ] an (EIC ) is required to be completed &issued together with . InspectionSchedules . & Test results Schedules.

There are twooptions . for ( EIC ) provided . form 1 : or form 2 : .

Form 1 : - Shortform of ( EIC ) to beused when . ONE person is responsible for the. design . construction . inspection & testing of an installation .
Or
From 2 : - ( EIC ) Three signatoryversion . from appendix 6 – BS-7671 .

Whichever . ( EIC ) isused . appropriate numbers of the following forms are required to . accompanythe Certificate .

Form 3 – Schedule ofInspections’ .
&
Form 4 – Generic . Scheduleof Test results .

For completeness .two samples of typical completed from 4s [ Schedule of test results ] areincluded . One . being for a Single-phase installation . & the other for a Three-phase installation .

2392-10 . this isthe kind of things -&-s will beasking you . ▲ which for ? . Single-phase / Three-phase installation.

 

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Point . to note: p/389 . Certification & Reporting .
( x ) Additionalforms may be required as . clarification . if needed by . Ordinary persons . or inexpansion . for larger or more complex installations .

 

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( MEIWC)
Two thing spring tomind . -&-s . 2392-10

The . Minor WorkCertificate . is intended to be used for . Alterations or Additions . to an [ Installation thatdo not extended to the provision of a NEW Circuit ]

This Certificatemay also be used for the .
replacement ofequipment such as accessories or luminaires , but not for the replacement of . distributionboards . or similar items . [ Appropriateinspection & testing . however . should always becarried out irrespective of the extent of the work undertaken . ] -&-s

 

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( MEIWC)

Description of ( MWs)

The minor work mustbe so described that the work that is the subject of the Certificate . can bereadily identified .

120.3. & 133.5.
No departures areto be expected except in most . unusual circumstances . 633.1.

Installationdetails .
Method of faultprotection must be clearly identified .Automatic disconnection of supply . ADS

If the existinginstallation lacks either an effective means of earthing or adequate . mainequipotential bonding conductors . this must be clearly stated in the spaceprovided – 633.2.

Recorded departures. form BS-7671 . may constitute . non-compliance with the . Electricity Safety. Quality & Continuity Regulations – 2002 . as amended . or the Electricity at Work Regulations 1989 . it is important that the Client isadvised immediately in Writing .

Essential Tests .
Relevant provisionsof part 6 . Inspection & Testing –BS-7671 . must be applied in full to all ( MWs )

Where asocket-outlet is added to an existing circuit . it is necessary to :
i) establish that the earthing contact of thesocket-outlet is connected to the ( MET)
ii) measure the ( IR ) of the circuit that has been added to . &establish that it complies with Table 61 .
iii) measure the EarthFault Loop Impedance . to establish that themaximum permitted disconnection time is [Not Exceeded ]
iv) Check that the polarity of the socket-outletis correct .
v) if the work is protected by an . RCD . verifythe effectiveness of the ., RCD .

 

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Inyour own words state what we mean by “ Basic protection “ & how is itachieved :

GN-3. 2012
Basic protection .
Sect– 416 . 416.2.
Ismost usually provided by [Insulation ] & or [ Enclosures ] the inspection of this measure is to check that insulation has not beendamaged during installation & that [Enclosures ] have been selected for atleast . IPXXB or IP2X .& for top surfaces . at leastIPXXD or IPX4 . & are not damaged .

(IR ) is of course a fundamental test to be carried Out .

 

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Inyour own words state what we mean by “ fault protection “ & how is it achieved .

Faultprotection by ( ADS )
Summaryof RCD requirements :
AnRCD should be cable of disconnecting allLine conductors at substantially the same time .
AnRCD cannot be used for fault protection on it’s own .

AnRCD on it’s own does not provide protection against overcurrents .
Overcurrentprotection is provided by a [ fuse or miniature circuit breaker – MCB] Exams’ . Combined :- RCD & MCB . RCBOs

RCCBs. BS-EN-61008-1 . p/34 .
Residual current operated circuit/breaker . [ Without integral overcurrent protection] for it’s time – household &similar uses

RCBOs. BS-EN-61009-1 . p/34 .
Residual current operated circuit/breaker . [ With integral overcurrent protection ] – household & similar uses .

Basicprotection : can be achieved by either preventing the current from passingthrough a body or by limiting the valueof the current to a non-hazardous level .
Faultprotection : can be achieved by similarmethods . but also by reducing the time the body is exposed to the fault .therefore aiming to reduce the time to a non-hazardous level .

Theprotective measure available :

Automaticdisconnection of supply – ( ADS )

Basicprotection 411.2.: can be achieved by either preventing the current from passing through a body or by limiting the value of thecurrent to a non-hazardous level .
To achieve basic protection the electrical equipmentmust rather employ the requirements of basic insulation of Live parts . – 416.1. :

Live parts . such as energizedconductors . must not be accessible . &
Conductiveparts . which are accessible suchas “ Metal pipes “ must not be hazardous Live .

 

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610.1. it should be noted the regulation 610.1.requires inspection & testing to be carried out during the erection stageof the installation . as well as on completion .

132.14.1.
Verification ofPolarity : Single-pole device in a TN- or TT system .
530.3.2:
Must be verifiedthat . single-pole devices for protection or switching are installed in lineconductors only .

Inyour own words state what we mean by “ fault protection “ & how is it achieved .

GN-3 :
Fault Protection .
The various methodsof fault protection are classified in a number of [ subsections ] BS-7671 -

Sect 411 . –418.1.
Automaticdisconnection of supply – ( ADS )
Method 1 : ( ADS )
For each circuit .automatic disconnection is required & . although the main part of .Verification is measurements of earth fault loop Impedance in order to confirm sdisconnectiontimes . there are inspection aspects to consider for verifying ( ADS ) follows :

2392-10 .
542.3. Earthing conductor .
Sect – 543 .Circuit protective conductors .
Sect – 544 .protective bonding conductors .
- Mainbonding conductors .
- Supplementary bonding conductors . where required.

312.2. The earthing system must be determined .
TN-C-S . - Protective multiple earthing – ( PME )
TN-S system .
TT system – Earth Electrode(s).

 

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Fused connectionunit :
Correct rating& fuse – 533.1.
Complies withBS-1363-4 – 559.6.1.1. – vii .

Cooker control unit.
- Sited to one side& low enough for accessibility & to prevent flexes trailing across radiant plates – 522.2.1.
- Cable to cookerfixed to prevent strain on connections – 522.8.5.

Test Method 2 : (R[SUP]2 [/SUP] )
Test Method 1: ( R[SUP]1[/SUP] + R[SUP] 2 [/SUP])

Radial circuit oflength about 55m with 2.5mm[SUP]2 [/SUP] Line & protective conductors should havean ( R[SUP]1[/SUP] + R[SUP] 2 [/SUP]) résistance .
Length of circuit –55m
Résistance of cableis . 7.41 mΩ/m ( at 20°C)
Theoretical minimum d.c. résistance = ( 55 x 2 x7.41 ) / 1000 = 0.82Ω

 

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Additions &Alterations .

132.16. Every addition & alteration to an existinginstallation must comply with the current edition of BS-7671 . & must notimpair the safety of the existing installation . in this respect . in order to verify that the addition & alterationto an electrical installation complies with BS-7671 . the existing installation must beinspected & tested to confirm the safety of the addition & alteration . 633.1. 633.2.

- Protective conductorcontinuity .
- Earth fault loopimpedance .

633.2. Whilst there is no obligation to inspect & test any part of the existinginstallation that does not affect & is not affected by the addition & alteration. observed departures are required to be noted in the comments box . of ( EIC ) single-signature . or multiple-signature . &minor work certificates .

 

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Recording the .Prospective Fault Current . ( PFC )

Both the ( EIC ) & the ( EICR ) contain a box headed . Nature of Supply Parameters . . whichrequires the . ( PFC ) at the [ Origin ] to be recorded .
The value to berecorded is the . Greater of either the short-circuit current . – between liveconductors . or the earth fault current . between line conductor(s) . & the. ( MET )

if it is considered necessary to record values atother relevant points . they can be . recorded on the . Schedule of Test Results . where the protective devices used . at theOrigin have the necessary rated breaking capacity . & devices with similar breakingcapacity are used throughout the installation . it can be assumed that theregulations are satisfied in this respect for all . distribution boards .

 

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PhaseSequence Testing . 612.12.

Thiscame up on Exams . 2391-10 ..

The 17[SUP]th[/SUP] Edition . introduced inregulation – 612.12. a requirement to [ Verify ] that the . phase-sequence ismaintained for multiphase circuits within an installation . in practice . thiswill be . achieved by checking polarity & connections throughout theinstallation .


Optionally& occasionally . the inspector may wish to . check phase sequence by usinga phase rotation tester . either .
- Rotating disk type . Or
- Indicator lamp type .

 

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Verification in Medical Locations . 710 :

710.61. The installation & testing of theseinstallations is very much a . specialist area & only the general requirements of .BS-7671 . are provided in this GN- .initial verification is carried out by an inspection & functional tests ofthe isolation IT system . equipment including the . insulationmonitoring devices . testing is required to measure the . leakage current ofthe output circuit of . Medical IT isolating transformers . & measurementof the résistance of the . supplementary equipotential bonding .

 

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Purposeof . Periodic Inspection & Testing . 621.2. is to provide an Engineering view . on whether or not theinstallation is in a satisfactory condition where it can continue to be usedSafety .