***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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The most effective way ofTesting for ( Earth Faults) in the wiring or equipment is byMeasuring the Insulation Résistance . as described in Section 6 . 612.3.1.
( Nobreakdown of the Conductor Insulation ) Nails . & Picture hooks . Screws . ???????????? :svengo:

2392-10 .
Floorboards’ Nail driven between the Neutral & Earthconductor(s) creates a ( Neutral to Earth Fault) :hurray:
“ RCD to Trip “
The Fault can be located byInsulation Testing .
Damaged cable must be replaced& either relocated to avoid further damage or protected .

2392-10 :- Requirements to protect cables from Impact& Penetration are given in Regulation 522.6.5. ( v ) p/100 . 522.6.5. the same . ( v ) p/124

 

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Section 712 :

Solar Photovoltaic ( PV ) Power Supply System(s)

712.512 : p/243 Accessibility.

712.513.1. The selection & erection of equipment shall facilitatesafe maintenance & shall notadversely affect provisions made by themanufactures of ( PV ) equipment to enable maintenance or service work to becarried out safely .

Scope .
Section 712 of BS-7671:2008 - ( Applies to the Electrical Installationof ( PV ) power )

Supply systems including system(s) with a.c. modules .

Note )- Section 712 does NOT apply to ( PV )power supply system(s) which are intended for ( Standalone Operation )

New Topics covered . On-Site Guide is Portable Generators .
Two classes of ( TemporaryGenerators ) – (i) Portable Generators .(ii) Mobile Generators .
Generators used for short periods :- One-day & these used for longer timescales .

□ Portable generators with an electrical output rating of up to( 10kVA ) used for small scale work –short term use ( Less than one day )
□ Mobile Generators . used for longer periods & can be in Excess of (( 10kVA ))

• Portable generator used with a Floating Earth .
• Portable generator used without reference to the general mass ofthe Earth .
• Portable generator referenced to the general mass of the Earth .

Permanent use of Generators . Guidance Note 5 - Guidance Note 7 .Section 551 . BS-7671:2008 / 2011 .

Generator(s) are used to ( supply Concession Vehicles ) such as (Burger Vans ) look Section 717 . Mobile & Transportable Units . / GuidanceNote 7 .

Temporarily supply electrical equipment or electricalinstallations with a generator where the mains or usual supply is Unavailable .

Portable generator with Floating Earth :

Small portable generators’ . ranging in ( Output ) from 0.3kVA / 10kVA single phase often have a ( Floating Earth )
Connection of the Socket-outlet of the Unit to the ( Neutral ) of the generator winding.
The ends of the generator winding are brought out to one or more (Three-pin socket-outlet(s) which should conform to BE-EN 60309-2.
[ The Earth socket-tube ofthe socket-outlet(s) are usually connected ( Internally to the Frame of the GeneratorOnly ] ► This arrangement is a form of ( Electrical Separation )

When do NEW INSTALLATIONS have to COMPLY with Amendment No 1 . Requirements
Amendment No 1 July 2011& will come into effect on ( 1 January 2012 ) This means that Installation(s) designedafter ( 1 January 2012 ) will need to comply with the Amendment 1 requirements

An Installation that was designed to the 17[SUP]th[/SUP] Edition “ BEFORE “ 1 January 2012 but gets completed after thisdate should be Certified to the 17[SUP]th[/SUP] Edition

 

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110.2. Exclusions fromScope . :hurray:

First Amendment ( xii )Electric fences covered by BS-EN 60335-2-76 . The rest are thesame . ( i ) - ( xi )

 

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( T ) Testingpurposes :- suitablewarning sign(s) & / or notices shall be provided 2391 / 2392 .

134.1.7. Where necessary forsafety purposes . suitable warning sign(s) & / or notices shall be provided.

134.2. Initial Verification .
During erection & on completion of an installation or anaddition or alteration to an installation . & before it is put into service. appropriate ( Inspection & Testing ) shall be carried out by CompetentPersons to verify that the requirements of this Standard have been met .

Appropriate certification shall be issued in accordance withSection 631 & 632 .

134.2.2. The designer ofthe installation shall make a recommendation for the interval to the firstperiodic inspection & test as detailed in Part 6 .
Note : The requirements of Chapter 34 ( Maintainability ) should be taken into consideration .

135 . Periodic Inspection and Testing .
135.1. It is recommendedthat every electrical installation is subjected to Periodic Inspection andTesting . in accordance with Chapter 62.

Definitions – Part 2 . p/25 .
□ Current-carrying capacityof a conductor .
The maximum current which can be carried by a conductor under specified conditions without its steady-statetemperature exceeding a specified value .

□ Current-using equipment .
Equipment which converts electrical energy into another form ofenergy . such as light . heat or motive power .

 

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Definitions . p/26 . New .to First Amendment

Discrimination : Ability ofa protective device to operate in preference to another protective device inseries .

 

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Definitions . p/26 . change.

Exposed-conductive-part . :carols:
Conductive part of equipment which can be touched & which isnot normally live . but which can become live under fault conditions .

Exposed-conductive-part .
Conductive part of equipment which can be touched & which is notnormally live . but which can become live when basic insulation fails .

 

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UsefulJunk .

17[SUP]th[/SUP] Edition Wiring Regulations . Requirements forElectrical Installations 2008 . :gettree:

The term ( Phase ) is replaced with the term ( Line )

Line is the Internationallyused term . Do Not confuse ( Line ◄ ) conductor with ( Live ◄ )conductor which can be a ( Neutral ) conductor .

Line Conductor )- p/29 . Definitions

A conductor of an A.C. system for the transmission of electricalenergy other than a ( Neutral ) conductor . A protectiveconductor or a ( PEN ) conductor . Theterm also means the equivalent conductor of a D.C. system unless otherwisespecified in the Regulations .

( PEN Conductor ) p/33 . Definitions
A conductor combining the functions of both protective conductor& Neutral conductor .

 

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Portablegenerator referenced to the general mass of the Earth.

Wherethere are ( Extraneous-conductive-parts ) or ( Exposed-conductive-parts ) fromother electrical systems present .
Generatorreference Earthing by means of an (Earth Electrode ) to the general mass of Earth should beinstalled .

NOTE )- That this does NOTcreate a ( TT Arrangement ) Thesupply will be ( TN-S ) from the generator but the ( Neutral ) or (Star point ) will be referenced to thegeneral mass of Earth .

( Generator reference Earthing - Using Earth Electrode )
Wherean Earth Electrode is supplied it will need to be tested by the Standard Method using a (Proprietary Earth Electrode résistance tester )

NOTE )- That an Earth FaultLoop Impedance Tester cannot be used for this Test as the Earth Electrode is NOT used as a meansof Earthing it used to reference the portable generator to the general mass ofthe Earth . As the Earth Electrode isused for referencing & NOT as a means of Earthing . The résistance should .( Ideally be Less than 200Ω )

If buried . generator reference Earthing&/or Bonding conductors should be sized in accordance with Table 54.1. & suitably protected in accordancewith Regulation 543.3.1. Whererestrictions . such as concreted / paved areas or the portable generator isbeing used some distance above ground level . make it impossible to install anEarth Electrode . ( Simultaneously )accessible metal parts . i.e. accessibleExtraneously-conductive-parts or Exposed-conductive-parts from other electrical systems . may beBonded to the ( MAIN ) Earthing Terminal of the generator .

Whereseparate accessible Extraneous-conductive-parts or Exposed-conductive-parts from other electricalsystems are connected together . protective conductors can be sized inaccordance with Regulation 544.1.1.

 

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Importantto Emphasise that Generators must be Used in “ Accordance with the Manufacturers Instructions “ :iagree:

WhereGenerators are ( Hired from plant-hire companies ) it is ( Responsibilityof the plant-hire company ) toprovide the Hirer with Information regarding the Safe use of their Equipment . Underno circumstances should Hirers attempt to change the Internal electricalconnections of Hired Equipment .

Where( Doubt Exists ) as to the Internal Earthing connectionsof the generator . a ( Continuity Testbetween Neutral & Earth socket-tubesat the socket-outlet can be undertaken ) Very Low reading – Less than ( 0.1Ω ) wouldindicate that it is not a generator with ( Floating Earth)

 

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Responsibilitiesof the Duty Holder :carols:

Minor Electrical Installation Work(s) Certificate .
( Requirements for Electrical Installations BS-7671 [[ IET Wiring Regulations ]]

To be Used only for minor electrical work which does NOT includethe provision of a NEW circuit .

System Earthing Arrangement . TN-C-S □ - TN-S □ - TT □
Part 2 )- Installation details . Comments on existing installation . Includingadequacy of ( Earthing & Bonding ) arrangements ( T -&-s ) Regulation 131.8. )
131.8. Moved by BS-7671:2008 Amendment No 1 to 132.16 . ◄ p/393

( T -&-s ) 132.16. p/20 .
Additions & Alterations to anInstallation .

No addition or alteration . temporary orpermanent . shall be made to an existing installation . Unless it has beenascertained that the rating & the CONDITION of any EXISTING EQUIPMENT . including that of the distributor . will beadequate for the altered circumstances . furthermore . the EARTHING & BONDING arrangements . if necessary forthe protective measure applied for the SAFETY of the ADDITION or ALTERATION .shall be adequate .

 

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For Minor Works the Installer is often the Designer of theAddition or Alteration . :svengo:

 

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Definitions – Part 2 : p/31 (NEW ) First Amendment :carolers:

Minor Works .

Additions & Alterations to an installation that do not extendto the provision of a new circuit .

 

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Definitions – Part 2 : p/31 / p/28 :christmaswreath:

From a Inspectors point of View.

Reporting : Communicatingthe results of ( Periodic Inspection& Testing ) of an electricalinstallation to person Ordering the Work .

 

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Standard ( PVC )Insulated Cable(s) are designed to operate at Temperature’s up to ( 70°C ) beyond this there is a risk of Damage . :gettree:

p/340 . Table 4D5 - ( 70°C ) Thermoplastic Insulated & Sheathed flatcable with Protective Conductor - ( Copper Conductors ) T&E .

Cableis guided by two main principles’ .

i)Cable should be able to carry the current load ( Imposed ) on it without ( Overheating )
(( Extreme conditions of temperature it willencounter during its Working Life . ))

ii) You should have sufficient sound Earthing - Limit the voltage to which people areExposed . Safe Level . ( Fault Current to trip MCB inshort time . )

OverCurrents can be Classed into two types

Overload )- An overload occurs when a current flows thatis somewhat to High .
□ Overloadsdon’t normally cause immediate damage . ( The likelihoodof Damage gradually as the duration of the Overload Increases )
□Cables will Overheat & Melt . (Exposing bare conductor(s)

□ DomesticInstallations Overloads usually results from using to many Appliances at the same time . 2392-10

ShortCircuit )-
□ isa connection between Line & Neutral . OR Line & Earth .
Youare looking for a ( Low Résistance ) & thecurrent that can flow may be hundreds or thousands of times to High for thesystem .

Thiscurrent is called the ( FaultCurrent or Short Circuit Current )

Short Circuit Current . An overcurrent resulting from a fault ofnegligible impedance between ( Live Conductors L/N ) having a difference in potential under normaloperating conditions . p/34

Fault Current : A currentresulting from a Fault . p/28

InPractice )- DomesticInstallation(s) Overload protection& Short circuit protection are both provided by the same Device . ( MCB ) or ( RCBO )
Additional Protection . may beprovided by an ( RCD )

Residual Current Operated circuit breaker withIntegral Overcurrent Protection ( RCBO ) designed to perform the functions of protection against Overload & Short Circuit.
“ Resi/ dual “ dual - two - L/N

 

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Circuit Breaker : ( MCB ) Definitions . p/25 - p/21 :17:

A device capable of making . carrying & breaking normal loadcurrents & also making & automatically breaking . under pre-determinedconditions . ( Abnormal Currents )
Such as ( Short Circuit Currents ) . it is usually required to operateinfrequently although some types are suitable for frequent operation .