***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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RingFinal Circuits . ( Point of Utilisation ) 2005/6

Inthis system the Line . Neutral . & Circuit Protective conductors areconnected to their respective terminalsat the consumer unit , Loop into eachSocket-outlet in turn & then returned to their respective terminals in theConsumer Units . Thus :-

Forminga Ring . Each Socket-outlet has two-outlet has two connections back to the MainSupply .

Considerationmust be given to the loading of the Ring Final Circuit .

SingleSocket - 1 point .
DoubleSocket - 1 point .
LightFitting with 1 Switch - 1 point .
LightFitting with two – 2 way switches & Intermediateswitch = 1 point .

Cooker. Isolator Switch with a combined Socket is - 2 points .

Asthe FirstAmendment No 1 2011 . rightly says

Appendix 15 ( Informative ) p/425

The load current in any part of the circuit should be unlikely toexceed for long periods the current-carrying capacity of the cable (Regulation 433.1.103 refers )
This can generally be achieved .

i) Locating Socket-outletsto provide reasonably sharing of the Load around the Ring .
iv) Taking account of thetotal floor area being served . ( Historically . a limit of 100m[SUP]2 [/SUP] hasbeen adopted )

On Site Guide .
Which is an “ Abbreviated “ version of BS-7671 :yes:

 

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Diversity - Table 1B . R/B O.S.G. p/97 second column

Justa reminder . Example .

Cookers . 100% - of 4000W / 230V = 17.39A
Cookers . 80% - of 3000W / 230V = 10.43A

 

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Useful Junk .

Example . The Screw Rule .

Thedirection of the magnetic field is traditionally using the “ Screw Rule “ :49:

Rotationof Screw = Rotation of magnetic field . “ Clockwise “
Directionof Screw = Direction of Current . →

Inthe Screw Rule we think of a normal (Right-hand threaded Screw )

Themovement of the Tip represents the direction of the Current through a straightconductor & the direction of rotation of the Screw represents thecorresponding direction of rotation of the magnetic field .

Rotationof Screw = Rotation of magnetic field .

 

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Definition:

Statutorylaws & regulations are written in a legal framework .

Definition:

Non-statutoryregulations & codes of practice interpret the Statutory regulations telling us how we can comply with the law .

BS-7671:2011 . incorporating No 1

114 . Relations with Statutory Regulations .
114.1. The Regulations areNon- Statutory .

ElectricCurrent .
The drift of “ Electrons “ within a conductor is known as an “ Electric Current “ measured in amperes & given the symbol ( I )

Voltagedrop :
Amountof voltage lost due to a résistance ,

 

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Guidance on Initial Testingof Installation(s)

Safety & Equipment . O.S.G. 2011

610.1. it is the Test operative’sduty to ensure their OWN safety . &the safety of others . whilst 612.1. working through Testprocedures . When using Test instruments . this is best achieved by precautionssuch as :-

i Knowledge & experience of the correctapplication & use of the test instrumentation . leads . probes &accessories ( is of the greatestimportance )

612.1. ii checking that the testinstrumentation is made in accordance with the appropriate safety standardssuch as BS-EN 61243-3 foe two pole voltage detectors & BS-EN61010 or BS-EN 6 for instruments.

Iii checking before eachuse that all leads . probes . accessories ( including all devices such as crocodile clips used to attach toconductors ) & instruments includingthe PROVING UNIT are clean . undamaged & functioning; also checking that isolation can besafely effected & that any locks or othermeans necessary for securing the isolation are available & functional .

GN-38 . iv observing the safety measures &procedures set out in ( HSE ) GuidanceNote GS-38 for all instruments . leads . probes & accessories . some testinstrument manufacturers advise that their instruments be used in conjunction withFUSED TEST LEADS & PROBES when the instruments has in-built electrical protectionbut it should be NOTED that such Electrical Protection does NOT extend to the ( PROBES & LEADS )

 

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BS-EN 61557 forinstruments

 

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Making you Aware

O.S.G. - First Amendment . BS-7671:2008 – ( 2011 ) p/35 - p/47

537.5. Functional Switching

537.5.1.1. A switch must beinstalled in each part of a circuit which may require to be controlledindependently of other pars of the installation .

530.3.2. Switches must not be installed in the neutralconductor alone .

537.5.1.3. Allcurrent-using equipment requiring control shall be controlled by a switch .

537.5.2.3. Off-loadisolators . fuses & links must not be used for functional switching .


NOTE : Table 53.4. of BS-7671:2008 – ( 2011 ) permits the use of CIRCUIT-BREAKERS for functional switching purposes but . in each case . The manufacturershould be consulted to establish suitability .

 

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Making you Aware

O.S.G. - First Amendment . BS-7671:2008 – ( 2011 ) p/33 - p/45

537.2. Isolation .

132.15.1. - 5.1.1. Requirement ◄◄

537.1.4. (i) A main linked switch or circuit-breakershould be provided as a MEANS of isolation & of interrupting theSUPPLY on LOAD .

For SINGLE-PHASE household &similar supplies that may be operated by UNSKILLED PERSONS . a DOUBLE-POLE DEVICE must be used for ( TT & TN- systems ) ◄◄

For a THREE-PHASE supply to an installation forming part of a TT system . an isolator MUST interrupt the LINE & NEUTRAL CONDUCTORS .
In a TN-S or TN-C-S system ONLY the LINE CONDUCTORS need be INTERRUPTED . ◄◄

 

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Making you Aware ( Extracts ) refer to Copper Conductors & are Relatedto 25mm[SUP]2[/SUP] SupplyTails from the Meter .

O.S.G. - First Amendment . BS-7671:2008 – ( 2011 ) p/32 - p/44

Typical Earthing Arrangements for Various Types of Earthing System.

Making you Aware

542.4.2. The earthing ( BAR ) is sometimes used as the ( MAINEARTHING TERMINAL ) .
However . means MUST beprovided in an Accessible Position forDisconnecting the Earthing Conductor to facilitate measurements’ of ExternalEarth Fault Loop Impedance . ( Ze )

NOTE : for TN-S & TN-C-S installations .

ADVICE . about the availability of an Earthing Facility & the Precise arrangement for CONNECTIONshould be OBTAINED from the Distributor or Supplier .

 

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Making you Aware . Extracts.

O.S.G. - First Amendment . BS-7671:2008 – ( 2011 ) p/31 - p/43

Earth Electrodes .

NOTE : Regulation 542.2.6.PERMITS the USE of privately owned WATERsupply PIPEWORK for Use as an EarthElectrode where precautions are taken againstits REMOVAL & it has been consideredfor SUCH USE .

This relaxation will NOT APPLY to an INSTALLATION within a ( DWELLING ) ◄◄ 2392-10 :gettree:

 

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Making you Aware . Reminder .

O.S.G. - First Amendment . BS-7671:2008 – ( 2011 ) p/30 - p/42

415.2. Supplementary EquipotenalBonding is REQUIRED in some of theLOCATIONS & INSTALLATIONS ( Falling within the SCOPE of Part 7 of BS-7671 )
If the installation MEETS the REQUIREMENTS of BS-7671:2008 – ( 2011 ) FOR Earthing & Bonding . There is NO SPECIFIC REQUIREMENT for Supplementary Equipotenal Bonding OF.

□ Kitchen pipes . sinks or draining boards .
□ Metallic boiler pipework .
□ Metallic furniture in KITCHENS .
□ Metallic pipes to Wash-hands basins & WCs .
□ Locations containing a BATH or SHOWER . ►► PROVIDING the CONDITIONS ofRegulation 701.415.2 ARE MET

NOTE : Metallic waste pipesdeemed to be ( Extraneous-conductive-parts ) must be connected by main protectivebonding conductors to the main Earthing Terminal .
See also 4.3.

Change .

4.2. ) Copper Earthing conductors cross-sectional area ( C.S.A. ) for TT supplies for Earth Fault Loop Impedance notless than ( 1 ohm ) p/29
Notes :
1) protected againstcorrosion by a Sheath .
2) for impedances less than (1 ohm ) determine as per Regulation 543.1.2.
3) The main protective bonding conductors shall have across-sectional area of not less than half that required for the earthingconductors & not less than ( 6mm[SUP]2[/SUP]) Regulation 544.1.1.

4.4. (ii ) Copper Earthing conductors cross-sectional area ( C.S.A. ) for TT supplies

Notes :
1) protected againstcorrosion by a Sheath .
2) The main protective bonding conductors shall have across-sectional area of not less than half that required for the earthingconductors & not less than ( 6mm[SUP]2[/SUP]) Regulation 544.1.1.

4.4. (ii ) Bonding connections to incoming metalservices should be made as NEAR as practicable to the point of entry of theservices into the premises . BUT on the Consumer’s Side of any Insulating Section . 544.1.2.

□ Reminder . (- Main Protective Bonding of Plastic Services. p/41 .

There is ( NO REQUIREMENT ) to Main Bond an incoming service where theincoming service pipe is ( PLASTIC )
Example (- Where YELLOW is USED for NATURAL GAS & BLUE for Potable Water .

 

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Making you Aware . Reminder . OFF THE WORDING .

O.S.G. - First Amendment . BS-7671:2008 – ( 2011 ) p/7

110.1. The scope generallyfollows that of BS-7671 . The guide includes material NOT included in BS-7671. provides background to the intentions ofBS-7671. & gives other sources of ( INFORMATION ) HOWEVER . IT DOES NOT ensure compliance with BS-7671 . it is a SIMPLE GUIDE to the REQUIREMENTS of BS-7671. to satisfy themselves of COMPLIANCE .

It is expected that persons carrying out WORK in ACCORDANCE withthis GUIDE will be COMPETENT to do so .

HSR25 . EWR . ◄◄ Electrical installations . in the United Kingdomwhich comply with the IET Wiring Regulations . BS-7671 MUST COMPLY with all relevant statutory regulations . such as the Electricity atWork Regulations 1989 - ( Regulation 16 ) The Building Regulations & . where relevant. the Electricity Safety . Quality & Continuity Regulations ( 2002) & Amendment ( 2006)

That’s why the Assessor will ask for the BS-7671:2008 First Amendment . NOT the O.S.G.

 

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Building Regulations . p12.
The Building Regulations ofEngland & Wales .

p/13 - Note : Guidance isavailable for each part of the Building Regulations in the form of Approved Documents which can be freelydownloaded from the Department for Communities & Local Government ( DCLG ) website : www.planningportal.gov.uk

 

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Making you Aware . Reminder . OFF THE WORDING .

O.S.G. - First Amendment . BS-7671:2008 – ( 2011 ) p/12

This guide also contains information which may be required ingeneral Installation Work . for Example . conduit & trunking capacities .bending ( Radii ) of cables . etc .

The guide introduces the use of standard circuits . which arediscussed in Section 7 . however .because of simplification . This Guide may NOT give the most ECONOMICAIL RESULTS .

This Guide is NOT a REPLACEMENT for BS-7671. which should ALWAYSbe CONSULTED .

Defined terms according to Part 2 of BS-7671 are Used .

In compliance with the definitions of BS-7671 . Throughout thisGUIDE the TERM . Line conductor is Usedinstead of Phase conductor & Live part is Used to refer to a conductor orconductive part intended to be energised in normal Use . including a Neutralconductor .

The terminals of electrical equipment are identified by theLetters . L . N . & E . ( or PE )

NOTE : for Clarification.

► The distributor of electricityis deemed to be the organisation owning the electrical supply equipment . &

► The supplier of electricity is the organisation from whom electricityis purchased .

 

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Sometimes we cant see . The Forest for the Trees . – We can’t see the Solution to the problem . it right in front off Us . BS-7671: :banghead: