***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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Just a Reminder : 2392-10 :santa_cheesy:

132.6. Cross-sectional Area of Conductors . ( C.S.A. ) :rant:
:rant:
The Cross-sectional area ofconductors shall be determined for both normal operating conditions & .where appropriate . ( for Fault Conditions according to )

i) The admissible maximum temperature .
ii) The admissible voltage drop . ( Vd )
iii) The electromechanical stresses likely to occur due to ( Short – circuit ) & ( Earth Fault Currents )
iv) Other mechanical stresses to which the ( Conductors ) are likely to be ( Exposed )
v) The maximum ( Impedance ) for correct operation of ( Short Circuit ) & (Earth Fault Protection )
vi) The method of installation .
vii) Harmonics .
viii) Thermal insulation .

 

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The “ Fundamental Principles “

thatare given in Chapter 13 are intended to provide for the safety of persons .livestock & the protection of property against dangers & damage whichmay arise in the reasonable use of electrical installations .

itis recognised that good workmanship by competent persons using proper materialswill reduce any hazards that may arise & that every item of equipment shallcomply with the Appropriate BritishStandard .

Electricaljoints are a potential source of overheating & if NOT securelymade could ultimately cause a fire . for this reason there are severalregulations relating to electrical connections .

Thisis mentioned within Chapter 13 . in regulation 134.1.4. Every electrical joint& connection shall be of proper construction as regards conductance .insulation . mechanical strength & protection .

“Good workmanship by competent persons using the proper materials will reducethe risk of Overheating or Fire . “

 

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Maintenance Free Connections ( 2392-10 )

Junctionboxes are commonly used .

Regulation 526.3.requires that every connection shall be accessible for ( Inspection . Testing & Maintenance )
There are 6 exceptionsto the rule ( vi ) is .

Equipmentcomplying with ( BS-5733) for a ( Maintenance Free ) accessory & ( Marked ) with thesymbol ( MF) & installed in accordance with the Manufactures Instructions .

BS– 5733 . ( Defines ) a Maintenance Free accessory as :-
Anaccessory which does NOT require further ( Inspection . Testing or Maintenance ) afterinstallation in a circuit . & which incorporates ( ScrewlessTerminals ) & cable clamps to secure any associated cables .

TheElectrical Safety Council Technical Manual States that a junction box with Screw Terminals must be ( ACCESSIBLE ) MUSTbe ACCESSIBLE .
Thisis to allow ( Inspection ) of jointswhich could have relaxed or loosened over time . a potential problem withscrewed terminals . SO . unless provision is made for ( Access ) where boarding . carpet or other similar covering is laidover a ( JunctionBox ) it may not be consideredaccessible & maintenance free terminals should be Used .

Appendix15 of the Wiring Regulations which states “ Junction Boxes with Screw Terminals must be Accessible for ( Inspection . Testing & Maintenance ) or Alternatively . use Maintenance Free Terminals / Connection - Regulation 526.3.

“Junction Boxes with Screw Terminals must be Accessible for Inspection …… ETC

Regulation : 526.3. p/106

i) . ii) . iii) . iv) the Same

Regulation : 526.3. p/131 :christmastree1:

v) Joints or connectionsmade in equipment by the manufacturer of the product & not intended to be ( Inspectedor Maintained )

vi) Equipment complyingwith BS-5733 for amaintenance-free-accessory & marked with the symbol ( MF ) & installed in accordance with theManufactures Instructions .

 

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DownlighterJunction box . :svengo:

Whenfitting recessed downlighters the following method would overcome all the issues .

Thesheath of both solid conductors & flexible conductors for the light fittingcan be secured as they enter the Enclosure .
ThisEnables compliance with . Regulation 522.8.5. in particular where it states that thereshall be no ( Undue Mechanical Strain on the Terminations )of the conductor(s)

Regulation 526.8. whichrequires the cores of Sheathed Cables from which the Sheath has been removed tobe Enclosed . can be seen to be complied with .

Cableclamps prevent Strain on Terminations for Compliance with Regulations .

Regulation 522.8.5. p/125 / Regulation 522.8.5. p/101 Thesame

Every cable or conductor shall be supported in such a way that itis not exposed to ( Undue MechanicalStrain ) & so that there is noappreciable mechanical strain on the terminations of the conductors . accountbeing taken of mechanical strain imposed by the supported weight of the cableor conductor itself .

Regulation 526.8. Connectionof multiwire . fine wire & very fine wire conductors .

Regulation 526.8.1. p/107.
In order to avoid inappropriate separation or spreading ofindividual wires of multiwire . fine wire or very fine wire conductors .suitable terminals shall be used or the conductor ends shall be suitablytreated

Regulation 526.9.1. p/131 . Connection of multiwire . fine wire & veryfine wire conductors .
In order to avoid inappropriate separation or spreading ofindividual wires of multiwire . fine wire or very fine wire conductors .suitable terminals shall be used or the conductor ends shall be suitablytreated

Requirements of 17th Edition Wiring Regulations – BS-7671:2008 .

A further potential problem can be found within the ( Junction Box ) concerning the type of conductors that are typicallyterminated . it is often the case in Domestic Installation(s) that solid twin & CPC cables will be used for the fixed wiring withthe conductor to the light fitting . Etc . or transformer if the lighting is ( ELV )
Being a ( Flexible conductor )

Strands of flexible cable are Secured adequately in the terminal& not been damaged to ensure compliance with regulation 526.2.

Asa Tester . How many time have you seen this . ?? . Q - Junctionbox :bulb2:
Whenthe conductor was removed for (Inspection ) it is clear that some ofthe Strands have been damaged during termination .

 

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MaintenanceFree Terminals ,
Theaccess to electrical connections should be adequate for their ( Safe ) &proper ( Inspection) Testing & Maintenance .

Inthis Respect . connections should be in a locationwhere they can reasonably be reached & where there is adequate workingspace . :svengo:

Whereconnections are made in roof spaces & inter-floor spaces the Enclosures containingthe connections should normally be fixed & provision must be made for theiraccess .

Providing )- These TWO CONSTRANINTS are COMPLIED with .Then the continued use of standard circular junction boxes remain ACCEPTABLE . :iagree:

 

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Plain English .

MaintenanceFree Junction Box )- Suitable for use in INACCESSIBLE LOCATIONS . ( MF ) :svengo:

TraditionalJunction Boxes )- Acceptable forLocations which are ACCESSIBLE .

 

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UsefulJunk .

BS-7671 is a British Standard for the “ Requirements for ElectricalInstallations “ it is important torealise that the regulations apply to the “ Design . Erection &Verification of Electrical Installations “

&are NOT intended to be a ( Product Standard ) This is covered at the beginning of thisdocument in Part 1 . Scope :welcome:

Regulation. 113 . Equipment .
113.1. The regulations apply to items of electricalequipment only so far as ( selection& application of the equipment inthe installation are concerned . The regulations Do Not Deal with requirementsfor the construction of assemblies of electrical equipment which are required tocomply with appropriate Standards .

Itis also important to appreciate that BS-7671 does NOTPRECLUDE the use of equipmentthat complies with the appropriate ( Product Standard) regardless of whether the construction of the equipment meets all theRegulations within BS-7671 .

Example.. Etc .
CeilingRose . BS-67 . Etc

Abovehave features which are NOT in accordwith BS-7671 but are ( PERMITTED )by virtue of their compliance to the appropriate ( PRODUCT STANDARD )

 

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The ( Principle) behind the Use of a ( Key or Tool ) is thatit requires a ( DeliberateAct ) to expose the ( LIVE ) conductor(s) . resents2:

 

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Regulation 412.2.2.3. p/62 :20:

Is concerned with ( Ensuring ) thatpersons opening the box do not come into contact with ( Live Parts Unintentionally )

412.2.2.3.
Where a ( Lid or Door ) inan insulating enclosure can be opened without the use of a tool or key . allconductive parts which are accessible if the lid or door is open shall bebehind an insulating barrier ( Providing a degree of protection not less thanIPXXB or IP2X preventing persons from coming unintentionally into contact with thesesconductive parts . This insulatingbarrier shall be ( Removable only by the use of a Tool orKey )

 

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Regulation relating to Junction Boxes is 521.8.3. p/122 . which requires that where ( Two or More ) circuits are terminated in a Single JunctionBox this shall comply with BS-EN 60670-22 :gettree:

Regulation relating to Junction Boxes is 521.8.3. p/98
which requires that where ( Two or More ) circuits are terminated in a Single JunctionBox this shall comply with BS-EN 60670-22 or BS-EN 60947-7.

p/235 . BS-EN 60670-22 . particular requirements forconnecting boxes & enclosures . 521.8.3.
p/236 . BS-EN 60947-7. specification for low-voltage switchgear& control gear . 521.8.3.

 

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Appendix15 ( Informative )

Fig 15A . i) . ii) . iii). the same .
iv) taking account of the total floor area being served . ( As a rule of thumb . a limit of 100m2 has been adopted )

iv) taking account of the total floor area being served . (Historically . a limit of 100m2 has beenadopted ) :20:

 

[Lux]

Hello there every one.

 

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Table of Table(s)

Table 41.1. – Maximum disconnectiontimes .
Table 41.2. – Maximum earthfault loop impedance ( Zs ) for fuses . for 0.4s disconnection time with Uo of 230V.
Table 41.3. – Maximum earthfault loop impedance ( Zs ) for circuit breakers with Uo of 230V .
Table 41.4. – Maximum earthfault loop impedance ( Zs ) for fuses . for 5s disconnection time with Uo of 230V.
Table 41.5. – Maximum earthfault loop impedance ( Zs ) for non-delayed RCDs to BS-EN 61008-1 & BS-EN 61009-1 for Uo of 230V – Regulation 411.5.3.

Regulation 411.5.3. Where an RCD is used for earth faultprotection . the following conditions shall be fulfilled : p/50 Wording

Regulation 411.5.3. Where an RCD is used for fault protection .the following conditions shall be fulfilled : p/57 Wording

Aswith the 17[SUP]th[/SUP] Edition . & First Amendment .

411.5.3. Note 2 : Where (Ra ) is not Known . it may be replaced by ( Zs )

Maximum earth fault loop impedance . ( Zs ) for non-delayed RCDsto BS-EN 61008-1& BS-EN 61009-1. for ( Uo of 230V ◄ ) - Regulation 511.5.3.

With the First Amendment : 41.5.
Rated residual operating current ( mA ) 30 : Maximum earth fault loop impedance ( Zs) ( Ohms ) 1667*
Rated residual operating current ( mA ) 100 : Maximum earth fault loop impedance ( Zs) ( Ohms ) 500*
Rated residual operating current ( mA ) 300 : Maximum earth fault loop impedance ( Zs) ( Ohms ) 167
Rated residual operating current ( mA ) 500 : Maximum earth fault loop impedance ( Zs) ( Ohms ) 100

Aswith the 17[SUP]th[/SUP] Edition . & First Amendment .
Note 2 : The Résistance ofthe installation earth electrode should be as low as practicable a Value exceeding ( 200 ) Ohms may not be stable . Refer Regulation 542.2.4.

 

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UsefulJunk . ( Electricians Judgement . ) :icon_bs:

Whatshould I do if the Manufactures InstallationInstructions for a product ( Conflict ) with the requirements of BS-7671:2008 . or include inappropriate or unnecessary Technical Requirements’

Any Installation Instructions considered tobe Technically Unsound should be ( Queried ) with the Manufacturer & / or referred to the ElectricalContractors registration body for Information .

Yes. I have had this on Site .

 

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Howmuch power does the Individual Built in-oven Draw . Individual Built in-oven – No hob . Supplied with a ( 13A Plug ) BS- 1363 .

Specs/ Regulations e.g. 3kW / 3000W . ( Maximum you can get from 13A Fuse )
Current - ( Amps )
Power– ( Watts ) / (Voltage )

Current ( Amps ) 3000 ÷ 230V = ( Current ( Amps ) 13.04 Amps) Uo /230V
13Aplug & Socket . ( Note :- 0.04 of an Amp over would be took up in Diversity as stated in BS-7671:2008 17[SUP]th[/SUP] Edition. :gettree:

TheDesign of UK Electrical Circuit means that NOT only is every Individual Appliance Protected by a Fuse . ( Protected from Overloading )

BS- 1363 – p/278 . 13A plugs . Socket-outlets . connectionunits & Adaptors .
BS- 1362 – p/278 . Specification. for general purpose fuse links for domestic & similar purposes ( Primarily for usein plugs )

BS- 1362 – During normal flow of Electricity . The fuse (Permits ) the power to pass Unobstructed . Duringan Unsafe Overload . A small piece of Metal Melts . stopping the flow ofElectricity .

Definitions Part 2 / p/28. p/25 The same.

( Fuse ) A device which .by the melting of one or more of its specially designed & proportioned components. Opens the circuit in which it is inserted by breaking the current when thisexceeds a given value for a sufficient time . The fuse comprises all the partsthat form the complete device .

( Fuse element ) A part of a fuse designed to MELT when the fuseoperates .