Re-take - Useful Information for 2394 :

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Trying this out . changed mysettings to .” Times Roman “ font

Calculate the speed at which a four-pole synchronous motor will run from a50Hz supply

f = n x p .
∴ 50 = n x 2 ( 4 poles gives 2 -pairs )
∴ n = 50 / 2 .
= 25 revs .

 

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Q) 2394 : The Regulations are designed to protect ( Who & what ) : Persons .Property . Livestock .

BS-7671: Wiring Regulations 2008:2011: ( 17[SUP]th[/SUP]Edition ) is the British standard for electrical installation in the United Kingdom. it is a non-statutory document . the purpose of the wiring regulations is toprotect - persons . property and livestock . from harm which could arise from theuse or presence of electricity .

Regulations are designed to protect . “ Property “ RCDs provide someprotection against electrical fires .

 

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BS-3871 replaced by BS-EN-60898 . there still out there .for years to come .
Miniature circuit breaker(s) BS-3871-1 .cant stress this enough ( part - 1 ) M1 to M9 . that’s what Inspectionis all about .

“ Room for improvement “ ( is the protective device BS-3871 . BS-EN-60898 )
Can we alter it from an Circuit breaker to an RCBO ? one option .

There is no requirement to change the consumer unit if you are installing anew final circuit . various requirements to provide mechanical protection . orRCD protection to the installed wiring & socket outlets . 411.3.3 .522.6.101 . 522.6.102 .

2394 : keep in mind : BS-7671:2008:2011 . does notdefine a kitchen as a special location .

( BR ) covering Approved Documents P . kitchen(s)
Is defined in the Building Regulations as a “ room or part of a room whichcontains a sink & food preparation facilities “

There can be some misunderstanding of correct terminology . Earthingconductor . upgraded to 16.00mm[SUP]2[/SUP] . ◄ This is the importantone .
Main protective bonding conductor 10.00mm[SUP]2[/SUP] .

Pont to note : Isolation & Switching .??
BS-EN-60898 . circuit breaker . Yes
( Genetic - RCD ) BS-EN-61009-1 .RCBO . Yes
BS-3871 replaced . This is the one you have to be awareof . can we use this to isolate .


2394: take it in the contents that its meant .
A Street is short . A Road is long . what you put In you willget Out . Studying .

 

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2394: What’s in a Book .
O.S.G. Simplifies

GN-3 . tells us where . The Tables in this appendix are as Appendix 2 ofthe O.S.G. .
The Tables provide ( Maximum ) permissiblemeasured earth fault loop impedance ( Zs ) 612.9 . “ Circuit-loop-impedance “

For compliance with BS-7671 where conventional final circuits are used .the values are those that must not be exceeded in the tests described at a testambient temperature of ( 10°C to 20°C ) 411.4.6. 411.4.7. 411.4.8. 543.1.3.

( Protective device(s) “ Genetic “ Fuse . Circuit breaker .
411.4.6. Where a fuse is used . Etc . ( ► 0.4s ) watch the wording )
411.4.7. Where a circuit breaker is used . ( re-minder the values specified in Table 41.3 for thetypes & ratings of overcurrent devices listed may be used instead of calculation )
411.4.8. where a fuse is used for a distribution circuit or final circuit .Etc . ( ► 5s ) watch the wording)
543.1.3. C.S.A. where calculated shall be not less than the valuedetermined by the . Etc

Regulations
Tables 54.2. p.161 . where the assumedinitial temperature is ( 30°C ) ◄

O.S.G. P.184 . Note 1 . see Table 54.3 ofBS-7671: which applies where the protective conductor is not incorporated or bunchedwith cables . or for bare protective conductors in contact with cables covering. ( 70°C ) ◄

O.S.G. P.184 . Note 2 .see Table 54.3 ofBS-7671: which applies where the protective conductor is a core in a cable oris bunched with cables

 

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Taken form old note . & tweaked . Leaning curve .

Zs = Ze + ( R[SUP]1[/SUP] + R[SUP]2[/SUP] )

Zs - Circuit-loop-impedance .

Zs = Ze + ( R[SUP]1[/SUP] + R[SUP]2[/SUP] )
Zs ) circuit-loop-impedance

The resistance of these conductors can be obtained from .
O.S.G. - Table 11 .
GN-3 p107 tells us . Maximum permissiblemeasured earth fault loop impedance .

Shower circuit . 30m in length is wired in . 6.0mm[SUP]2[/SUP] / 2.5mm[SUP]2[/SUP] cable.
BS-1361 . BS-88-3 32A fuse . Ze is given as (0.15Ω )

Zs = Ze + ( R[SUP]1[/SUP] + R[SUP]2[/SUP] )

6.0mm[SUP]2[/SUP] = 3.08 mΩ/m . 2.5mm[SUP]2[/SUP] = 7.41 mΩ/m .
Note : 6.0mm[SUP]2[/SUP] /2.5mm[SUP]2[/SUP] =10.49Ω . O.S.G. table - 11 ( 20°C )

Ze ) - 0.15Ω . length = 30m . multiplying factor 1.2

Zs = Ze + ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) x lengthx multiplier ---- 1000 .

Zs ) = 0.15 + ( 10.49 x 30 x 1.2 ) --- 1000 . = 0.15 + 0.38 = 0.53Ω

 

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(AMD ) - the Assumed MaximumDemand can be still greater than the supply fuse . you will find that thesupply fuse has been in place for manyyears . & never been a problem . because of diversity .

Mostoff the time . 2394 : We are using. consumer-units with split-loads .

 

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What is the requirements of Part - P . from Extracts .

2005 it is a legal requirement for all work of fixed electricalinstallations in dwellings and associated buildings to comply with relevantstandards .
The relevant UKstandard is BS-7671: Requirements for electrical installation . the IET wiringregulations - 17[SUP]th[/SUP] Edition .
As . BS-7671:2008:2011: covers requirements for . design . installation .inspection . testing . Verification . Certification .

re-minder 2394:

Notifiable work includes new installation(s) house re-wires . and theinstallation of a new circuit(s)
Notifiable work also includes addition(s) toexisting circuits in kitchens . bathrooms .outdoors and in other special locations .

Non - notifiable :
- Replacing accessories such as socket-outlets . cooker - switch andceiling rose(s)
- Replacing the cable for a single circuit only . where damaged . by fire .rodent or impact .

impact
on condition that the replacement cable has the same current carryingcapacity . follows the same route and does not serve more that one sub -circuit through a consumer unit .

- re - fixing or replacing the enclosures of existing installationcomponents :- if the circuit(s) protective measures are unaffected by increasedthermal insulation .
- installing or upgrading main or supplementary equipotential bonding :- suchwork shall comply with other applicable legislation . such as the Gas Safety - installationand use Regulations .

- Work that is not in a kitchen or special location and does not involve aspecial installation and consists of .
• Adding lighting point - light fittings &switches to an existing circuit(s)
• Adding socket-outlet and fused spurs to an exitingring or radial circuit(s)
Only : if the existing circuit protective device is suitable and provideprotection for the modified circuit . and other relevant safety provisions aresatisfactory .

BS-7671:2008:2011:recommend that the voltage drop in a circuit should not exceed a certainpercentage of the volte at the Origin of a circuit .

Percentage is 3% for lighting .
Percentage is 5% for power . powercircuit 5 x 230V ÷ 100 = 11.5V

Uo / 230V single - phase supply the voltage drop on a lighting circuitshould not exceed ( 3% of 230V ) 3 x 230V ÷ 100 = 6.9V

This will creep into the Exams .

 

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Useful Junk . taken from Extracts .

Main protective bonding for boilers .
There is No Requirement with BS-7671: to provide supplementary protectivebonding to the pipework connected to domestic boilers . however there is a requirementto provide main protective bonding to central heating systems . although nospecific detail is provided where the bonding conductor should be connected . youwill be advised this could be connected at the flow or return pipes of the boiler.

However in a domestic central heating installation it may be that centralheating pipework is not considered as an ( Extraneous conductive part ) andmain protective bonding would then not be required . the decision ultimatelylies with the installation designer to determine what is not an ( Extraneousconductive part )

 

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Useful-Junk

“ De-NeutralisingBlack “ Blast from the Past

Underthe new indemnification colours for fixed-wiring introduced by Amendment - 2 . to BS-7671: Black is now used to indentify a ( Phase-conductor . Not a Neutral ofcourse ) . all single-phase applications. it would be preferable to use cables .marked for such use . that is with brown . blue . green-and-yellow . cores

Breaking the Black /Neutral association .

Wherethree-core cables marked in the . New three-phase colours used . for single-phase applications . it isproposed that . as a convention . the Black-core is ( Usedfor the Protective-conductor ) the Brown for the .phase-conductor . andthe ( Gray for the Neutral ) This convention is intended to break . theassociation between Black andNeutral . it mean that the ( Black-corewould normally be overmarked . Green-and-yellow . and the ( Gray-core overmarked Blue or ( N ) the Brown-core would not need additional-marking .

 

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Useful-Junk

“ De-NeutralisingBlack “

Where SWA - cables with Brown. Black and Gary -cores . are used for Street-lighting applications . the ( Black-core ) being used as a circuit-protective-conductor in parallel with the .Armouring to minimise circuit-lengths .

Fire-alarm system’s

Applying the same convention to a ( Flat-three-core ) fire-alarm - interlink cable . the Gray would be overmarked as the ( Neutral) and the Black - interlink overmarked Brown .

3- core & Earth .
Brown- Phase-conductor .
Black- . overmarked brown .
Gray- Neutral . overmarked blue .
Earth is Earth .

 

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Approved Document P . 2005 - Extracts .

There are Two : simply - stated . Legal-requirements .

the first isthat .
“Reasonable provision shall be made in the design . installation . inspection and testing of electrical -installation in order to protect persons from fire or injury .

The second requirement is that .
“ Sufficient-information shall be provided so that persons wishing to operate .maintain or alter an electrical-installation . cando so with reasonable-safety .

My- Limitations . on the application of the requirements .
Yes : p.16 / 2008.
Therequirements of this . Part apply only to electrical-installations . that areintended to . operate at . Low or Extra-low voltage .

Installation(s) in Dwellings . To operate at . Low or Extra-low-voltage . The Extra-low-voltage band was included to cover such things as . Extra-low-voltage downlights . cause of a number of house - fires .

 

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Medical-Grounds . Equipment . ESC .

I have posted this for a reason. ( SPDs ) which can be used in Domestic - installations.

Q) . Is it necessary to install . Surge-protective-devices . indomestic and similar premises .

Generally No .

However . where a risk-assessment is carried out and this indicates that unacceptable-consequences-exit . such as to human-life . ( as a result of damage to essential-medical-equipment ) Example .

( SPDs ) must be installed . in addition . where the consequences of equipment-failure due to an . Overvoltage are deemed to be unacceptable after discussion with the customer . ( SPDs ) protection should be provided .

 

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GN-3 - p70 . Periodic-Inspection . (Take nothing for Granted )

2394 : With any . New-Installation . re-wire . it does not mean that the . DNO - Electrical-intake-equipment. is New . ( Visual - inspection )
GN-3 . and Regulations . reminds us .

Example . checklistof items that require - inspection .
The following is acopy of the checklist in . Appendix - 6 . BS-7671:2008:2011: which lists items at various-locations within an installation that may requireinspection .

Electrical-intake-equipment. GN-3

Service-cable .
Service-cut-out /fuse .
Meter-tails -Distributor .
Meter-tails -Consumer .
Metering-equipment .
Isolator .

Distributor’s / Supply-intake-equipment .

BS-7671:2008:2011: P.400 . Condition-Report-Inspection-Schedule .

Service-cable . -condition .
Condition of - service-head.
Condition of - tails- Distributor .
Condition of - tails- Consumer .
metering-equipment .
Condition of isolator - where-present .

 

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Youwill use BS-7671:2011: as the documentagainst which a professional judgement needs to be made . along with theRegulations .

The Regulations Must - State the Facts .

MultipleChoice Questions from all Sections . 2394 : those will come in Handy . 2008:2011:

Contactof persons or livestockwith exposed-conductive-parts which have become live-under-fault-conditions .is referred to as .
• Basic-protection .
• Fault-protection .
• Electric-shock .
• Earthing .

▲ Regulation - p.28 . ( By definition )
Fault-protection: Protection against electric-shock under single-fault-conditions .

▲ Note : for low voltage installations . systems aequipment . fault-protection generally corresponds to protection against indirect-contact. mainly with regards to failure of basic-insulation. indirect-contact is ( contact of persons or livestock with exposed-conductive-parts . which have becomelive under fault-conditions )

The disconnection of the nearest “ appropriate “ protection-device is called : ( All in the Wording . Yeah )
• Discrimination.
• Diversity .
• BS-EN-60898 .
• 30mA RCD .

▲ Regulation - p.26 .
Abilityof a protective-device to operate in preference to another protective device inSeries .

Ring-final-circuit. NOT exceeding 32A must disconnect within :
• 5 seconds .
• 300mS .
• 40mS .
• 0.4 seconds .

▲ Regulation - p.53 . 411.3.2.2.
Themaximum disconnection-time stated in Table - 41.1. . shall be applied tofinal-circuits Not exceeding 32A . ( 0.4s tells us it’s a TN - system )

Whichof the following devices would be suitable for protecting a . 9.5kW shower:
• BS-88-2 .
• BS-88-3 .
• 30mA RCD.
• 100mA RCD .

▲ Manufactureinstructions - New shower fitted andthe ( Manual )says an RCD must be fitted . it is a requirement of BS-7671:2011: that all equipment is installed in accordance with the . manufacturer’s instructions and documentation.
▲ BS-7671: requires circuitsof locations containing baths or showerto have RCD - protection .
▲ Regulation - 701.411.3.3. requires that all circuits within this location shall be provided with additional-protectionby a . residual-current-device ( RCD ) not exceeding . 30mA with an opening-time . not exceeding . 40mS .at a residual-current . of 5 x IΔn . thiswould effectively be . 150mA . the RCD -requirement will include . ( LV) low-voltage . lighting-circuit(s) . shower-circuit(s) . electric-towel-rails .

 

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MultipleChoice Questions from all Sections . 2394 : those will come in Handy . 2008:2011:

Whichof the following would be the appropriate protection-device for a Large-motor :
• BS-EN-60898 - Type D .
• BS-EN-61009-1 .
• BS-EN-60898 - Type B .
• BS-1362 .

Usingtables within BS-7671:2011: if the supply cables coming into a domesticproperty is 25mm[SUP]2 [/SUP] . what size should the Earthing-conductor be .
• 16mm[SUP]2[/SUP].
• 25mm[SUP]2[/SUP] .
• 10mm[SUP]2[/SUP] .
• 50mm[SUP]2 [/SUP] .

Usingtables within BS-7671: 2011 . what size earthing-conductor should be used whenbonding to the main incoming gas and water pipes when the incoming supply is (25mm[SUP]2 [/SUP]) .
• 16mm[SUP]2 [/SUP].
• 10mm[SUP]2 [/SUP].
• 4mm[SUP]2 [/SUP].[SUP][/SUP]
• Any of the above .

Whenperforming an insulation-résistance test on an SELV system . what should the test-voltage be :
• 50V .
• 24V .
• 500V .
• 250V .

Table- 61 . p.191 .
Whatis the . Minimum-insulation-résistance (MΩ ) for an SELV system :
• 0.5 MΩ .
• 0.2 MΩ .
• 1.0 MΩ .
• 0.4 MΩ .

2394: The Regulations Must - State the Facts .

Appendix - 6 . ( Informative ) p.389
Model-forms . Certification and Reporting .

iv) Competent-persons will . as appropriateto there function under . (i) (ii) & (iii) have a sound knowledge and experience relevant . to the nature of the work . undertaken and tothe technical-standards set down inthese Regulations . be fully versed in the . Inspection and Testing procedures contained in the . Regulations and employ . adequate testing equipment .

Periodicinspection and testing must beundertaking by : (iii)
• Special Company .
• Competent Person.
• Apprentice .
• Electrician .

▲ All installations must be . Inspected and Tested- periodically to ensure that they are safe for . continued-use .

Pointto note : 621.3 . Precautions shall betaken to ensure that the . periodic-inspection & testing shall not cause danger to ( Persons or Livestock ) and shall not cause ( Damage to Property ) and equipment even if the circuit isdefective .

(i)(ii) & (iii) ( EIC ) - ( MWC ) - ( EICR ) Authenticated - by a Competent Person .