***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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Appendix 15 ( Informative )

Ring final circuit arrangements .Regulation 433.1..103 .
2392-10 :

The load Current in any part of the circuit should be unlikelyto exceed for long periods the Current –carrying capacity of the cable ( Regulation 433.1.103 refers )
Thiscan generally be achieved . p/425 .

i) Locating socket-outletsto provide reasonable sharing of the Load around the Ring . :svengo:
iv) Taking account of thetotal floor area being served . ( Historically . a limit of 100m[SUP]2[/SUP] has been adopted ) :svengo:

Does the ( R1 + R2 ) Test confirm the correct polarity of a radialcircuit .
NO )- not on it’s Own Whilst the test can provide an Indication ofpolarity . it needs to be combined with Inspection & further Testing asrequired by part 6 - BS-7671:2008 .

January1[SUP]st[/SUP] 2005 Legislation came into effect which broughtElectrical Work in Dwellings under the BuildingRegulations . ( & made it aControlled Service )

ThisAmendment to the Building Regulations .Known as ( Part P ) imposes “ SAFETY “ REQUIREMENTS

ClassifiesElectrical Installation Work – into two basic Categories , ( Notifiable ) & ( Non-notifiable )

 

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BS-1363: Plug there isn’t ( YET ) a regulation to prevent you from plugging itin .

Eachtype of Fuse has a ( Time – current characteristic) which shows the time required to Meltthe Fuse for any given level of Overload Current .
AFuse is a very basic protection device which is destroyed ( i.e. it Blows )

Just a reminder .

Definitions – p/34 .
Résistance Area - ( R[SUP]a[/SUP] ) . ( for an Earth Electrode Only ) The surface area of ground ( around an Earth Electrode) on which a significant voltage gradient may Exit . :rant:

 

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Justmaking you Aware . -&-s . Common Q/As :santa5:

Stationary Equipment . p/35- p/30 .

Electrical Equipment which is either Fixed or whichhas a Mass Exceeding ( 18kg ) & is Not provided with a carrying handle .

 

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Definitions’ )- p/23

Accessory “ Means . a device . other than current-usingequipment . associated with such equipment or with the wiring of an installation.
Appliances “ Means . an item of current using equipment other thana luminaire or an independent motor .


Supplier– see Distributor
Distributor p23 : Aperson who distributes electricity to consumer using electrical lines &equipment that he/she owns or operates .

Origin of an Installation p31 : Theposition at which Electrical Energy is delivered to an Electrical Installation

Wordingfrom a 2392-10 point of View . ( At the Origin ) ▲ :svengo:

Surge Current P/35 : A transientwave appearing as an Overcurrent caused by a ( Lighting Electromagnetic Impulse )

Surge Protective Device (SPD ) P/35
A device that is intended to limit transient overvoltage’s &divert surge Currents .

p/141.Basics )- 534.2.1. Use of ( SPDs )
where required by Section 443 or otherwise specified . SPD shallbe installed .

i) Near the origin of aninstallation . or
ii) In the main distribution assembly nearest the origin of aninstallation .

534.2.3.6. p/145 Co-ordination of SPDs
SPDs shall be selected & erected such as to ensurecoordination in operation .

536.2. Selectivity between overcurrentprotective devices .

Where Selectivity between overcurrent protective devices isnecessary to prevent danger & where required for proper functioning of theinstallation . the manufacture’s instructions shall be taken into account .

536.3 p/148 . Selectivity betweenRCDs .

Where Selectivity between RCDs . is necessary to prevent danger& where required for proper functioning of the installation . the manufacture’sinstructions shall be taken into account .

 

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Abrasion . damage to wiring systems due to : p/437 :christmastree1:

522.6.1.
Impact ( AG ) p/124 .
Wiring systems shall be selected & erected so as to minimizethe damage arising from mechanical stress . e.g. by impact . abrasion .penetration . tension or compression during installation . use or maintenance .

717.52.2. – (ii) p/248. The wiring systemshall be installed using one or more of the following :
ii) Sheathed flexible cablewith thermoplastic or thermosetting insulated to BS-6004. BS-7211 or BS-7919 .if precautionary measures are taken such that no mechanical damage is likely tooccur due to any sharp-edged parts or abrasion .

721.522.7.1. Vibration ( AH) p/255

As the wiring will be subjected to vibration . all wiring shall beprotected against mechanical damage either by location or by enhanced mechanicalprotection . Wiring passing through metalwork shall be protected by means of suitable bushes or grommets . securelyfixed in position . Precautions shall be taken to avoid mechanical damage due to sharp edges or abrasive parts .

 

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Whenmust the Test be Carried Out . :60:

InitialVerification : consists of Visual Inspection& Testing . of ElectricalInstallation to determine ( as reasonably practicable ) have been met . includingrequirements for the Reporting of the Test Results.

610 : Initial Verification.

610.1. p/189 .
Every installation shall . during erection & on completion beforeput into service . be Inspected & Tested to verify . so far as is “ reasonably practicable “
That the requirements of the regulations have been Met .

610.3 :
The Verification shall include comparison of the results with relevantcriteria to confirm that the requirements of the regulations have been Met .

2392-10 (- as Regulation 610.6. rightly reminds us . On Completion of the Verification .according to Regulation(s) 610.1. to 610.5 ◄ a Certificate shallbe prepared

611 : Inspection .
611.1. Inspection shallprecede Testing & shall normally be done with that part of the Installationunder Inspection disconnected from the Supply .

612. Testing
612.1. The Tests ofRegulations 612.2. to 13 . Where relevant. shall be carried out & the results compared with relevant criteria .

612.13. 2392-10 . from your point of View
Functional Testing . is the Last Test . ( &Operational Tests )

AsRegulation rightly says . 612.14.
Note : Verification of voltage drop is NOT normally required duringInitial Verification

632 : Initial Verification

632.4. Defects or Omissions revealed during Inspection & Testing of the Installation workcovered by the Certificate shall be made good before the Certificate is Issued.

InsulationRésistance :

WhereSurge Protective Devices ( SPD ) arelikely to Influence the Test or be Damaged . such equipment shall bedisconnected before carrying out the Insulation Résistance Test . ( These will be creeping in after next year . -&-s Q/As )

Whereit is NOT reasonably practicable to disconnect suchequipment . ▲

2392-10. NOTE 2 (- Insulation Résistance values are usually much “ HIGHER “ than those of Table 61 . p/191. p/158 . 500V / 1.0MΩ . Etc.

 

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What is Verification “Meaning “ :gettree:

Definitions : p/36 Verification .

All measures by means of which “ COMPLIANCE “ of the electrical installation with the relevantrequirements of BS-7671 are CHECKED .

Verification of theProtection by ( MCB ) in a ( TN – System ) ◄◄
According to BS-7671:2008 .No 1 : 2011

Maximum value of ( Zs ) .Example - 1.44Ω / MCB 16A . Characteristic C )

As an Inspector “ Your Instrument reads ( 1.14Ω ) or 202A on Fault Current Range . it means that the condition ( Zs x Ia ≤ Uo )

The ( Zs ) of 1.14Ω is Less than ( 1.44Ω ) or the Fault Currentof 202A is more than ( Ia ) of 160A .

In case of Fault between Line & Earth . The wallSocket Tested in this ( Example ) Protected because the MCB will trip withinthe disconnection time required.

Verification of theProtection by ( MCB )
Table 41.3. – p/56
Type C – 16A – 1.44Ω

According to BS-7671:2008 . No 1 : 2011
Maximum Earth Fault Loop Impedance ( Zs ) for circuit breakers with Uo of 230V . for instantaneous operation giving “ COMPLIANCE “ withthe ( 0.4s ) disconnection time of Regulation 411.3.2.2. .

NOTE : 411.3.2.2.

The Maximum disconnection time Stated in Table 41.1. SHALL be applied to FINAL CIRCUITS NOT exceeding ( 32A ) 0.4s / TN- ◄◄

 

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Electrical Installation Condition Report . p/396 :carolers:

The inspection & testing detailed in this report &accompanying schedules have been carried out in accordance with BS-7671:2008( IET Wiring Regulations ) as amended to ….

It should be NOTED that cables concealedwithin trunking & conduits . under floors . in roof spaces . &generally within the fabric of the building or underground . have NOT been Inspected unless specifically agreed between the Client& Inspector prior to the Inspection .

 

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BS-5266 : EmergencyLighting .

110.1.3. (ii) . p/14
The regulations are intended to be applied to electrical installationsgenerally but . in certain cases , they may need to be supplemented by therequirements or recommendations of other British or Harmonized Standards or bythe requirements of the person ordering the work . ETC .

(ii) Emergency Lighting – BS 5266

528.1 . Note 2 . P/133 Proximity toelectrical services .
Except where one of the following methods is adopted . neither a voltage Band 1 nor a voltage Band 11 circuitshall be contained in the same wiring system as a circuit of nominal voltageexceeding that of low voltage . & a band 1 circuit shall not be contained inthe same wiring system as a Band 11 circuit .

Note 2 . Requirements forseparation & segregation in relation to safety services are given in BS-5266 & BS-5839.

560.8.1. Note 2 . P/186
One or more of the following wiring systems shall be utilised forsafety services required to operated in fire conditions .

Note 2 : BS-5266 . BS-5839 & BS8519 specifiescables to BS-EN 60702-1 . BS7629-1 & BS-7846 asbeing suitable when appropriately selected for this application .
(ii) Emergency Lighting –BS-5266.

560.9. p/187 .
Emergency lighting system shall comply with the relevant parts ofBS 5266 series .

710.560.9.1. – (i) p/236 . Safety Lighting .
In the event of main power failure . the changeover period to thesafety services source shall not exceed 15s . The necessary minimum illuminance shall be provided for the following .

(i) Emergency lighting& Exit Sign to BS-5266 .

BS-5266 : EmergencyLighting . Code of practice for the EmergencyLighting of premises . 560.8.1. note 1 – (i) p/186

Note 1 : The codes of practice in the UK for emergency lighting . firealarms & life safety & fire fighting applications are :
(i) BS 5266 Part 1 : Emergency lighting – Code of practice for theemergency lighting of premises .

 

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E.A.W.R.1989 . Compliance - Electricity at Work Regulation . :svengo:

Regulation ( 16 ) Person to be Competent.

Status/ Absolute .
Noperson shall be engaged in any work activity where technical knowledge or experience isnecessary to prevent danger . or where appropriate . injury . unless he possessessuch knowledge or experience . or isunder such degree of supervision as may be appropriate having regard to thenature of the work .

LegalRequirements .

Toachieve compliance with the legal requirements of the Electricity at Work Regulations1989 requires proof that an electrical system is safe . which involves amongstother things . proper Inspection & Testing of an system by competent person(s)& the creation & maintenance of records .

First Amendment . p/25

Competent Person .
A person who possesses sufficient technical knowledge . relevant practicalskills . & experience for the natureof the electrical work undertaken & is able at all times to prevent danger& . where appropriate . injury to him /herself & others .

 

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Failureto comply with the Building Regulations is a criminal offence & localauthorities have the power to require the removal or alteration of work thatdoes not comply with the requirements .

What is the Requirements of Part P .

It is a Legal requirement for all work on Fixed ElectricalInstallations in dwellings & associated buildings to comply with RelevantStandards .

TheRelevant UK Standard is :

BS-7671:2008 . Requirements for electrical installations ( IET Wiring Regulations 17[SUP]th[/SUP] Edition. First Amendment . ) :rant:
BS-7671:2008 . Covers requirements for Design . Installation . Inspection . Testing .Verification & Certification .

UsefulJunk .

Part P : Applies to parts of Electrical Installationsthat operates at voltages NOT exceeding 1000V a.c.

 

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Certification.

BS-7671:2008. requires that a person installingelectrical work or altering an existing installation must test the installation& provide certification to the owner.

 

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FundamentalPrinciples . are intended to provide for ( Safety ofPersons ) Livestock & the Protection of Property against Dangers &Damage which may arise .Etc


“ Touch Voltage“

Reminder. The Objectof BS-7671:2008. First Amendment No 1 2011 .

Chapter 41 . Protection against Electric Shock .

The PROVISION of requirements CONCERNING protection AGAINST Electric Shock .

The Touch Voltage concept is concerned with the latter form of ( Electric Shock ) it is used to determine the ( Magnitude ) of voltage to which the Person at ( RISK ) would be subjected in the ( EVENT ) of an EARTH Fault Occurring in an Installation .

 

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Part P : Applies to parts of ElectricalInstallations that operates at voltages NOT exceeding 1000V alternatingcurrent .

Justa Reminder .

Whatare Electrical Installations defined as . Plain English .

Anyfixed Electrical Cables or fixed electrical equipment located on the consumer’sside of the electricity supply meter . it also includes Low voltage & Extra-low voltageinstallations .

What are Electrical Installations defined as . 2011

Voltage . nominal . p/36 – p/31.

Voltage by which an installation ( or part of an installation ) isdesigned . the following ranges of nominal voltage ( r/ms values for A.C. ) are defined .

“ Extra-low voltage “ meansvoltage not exceeding .

i) in relation toalternating current . ( 50 ) volts between conductors & earth . OR
ii) in relation to directcurrent . ( 120 ) volts between conductors .

“ Low voltage “ meansvoltage not exceeding .

i) in relation toalternating current . ( 1000 )volts between conductors or ( 600 )volts between conductors & earth . OR
ii) in relation to directcurrent . ( 1500 ) volts between conductors . or ( 900 ) volts between conductors & earth .

 

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PartP . Electrical Safety . Design &Installation . p/16

P1 . Reasonable provision shallbe made in the design & installation of electrical installation(s) in orderto protect persons operating . maintaining or altering the installations fromfire or injury .

Limits on Application . :svengo:

Therequirements of this part apply ONLY toelectrical installation(s) that are intended to operate at . Low-voltage or Extra-low voltage & are : ◄

a) in or attached to a dwelling.