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
-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
Fundamentally . Two typesof form are recognised by BS-7671 . Certificates & Reports .
□ Certificates are issuedfor New Installation Work . □ Reports are Issued forInspections of Existing Installations .
Certification
Two types of Certificatefor New Work recognised by BS-7671 : □ ElectricalInstallation Certificate . □ Minor ElectricalInstallation Work Certificate .
● ElectricalInstallation Certificate . is intended to be is used where moresignificant Installation Work is undertaken . ● Minor Electrical Installation Work Certificate . is intended to be issuedfor an Addition or Alteration to an existing circuit .
isdefined in the Building Regulations as a Room or Part of a Room which contains aSink & Food preparation facilities .
“ As a guide only “ inOpen plan areas the zone of a Kitchen may be considered to extended from theedge of the Sink to a distance of ( 3m ) or to anearer dividing wall .
□ In large bathrooms . The locating a Bath or Shower isdefined by the ( Walls of theBathroom )
Just a Reminder p/15 . 2392-10
B/R . 2008
The BuildingRegulations ( Regulation 4 (2)) require that on (Completion of Work ) in an existing building. The building should be NO WORSE in terms of the level of compliance with the otherApplicable Parts of Schedule 1 . to the Building Regulations . including Parts . A. B . C . E . F . L. & M .
P/15. PartA . ( Structure ) depth of chases in walls .& size of holes & notches in floor & roof joists .
PartB . ( FireSafety ) fire safety of certain electricalinstallations . PROVISION of fire alarm & fire detection systems . fire résistance ofpenetrations through floors & walls .
PartM . ( Access to& use of buildings ) heights of switches . socket outlets &other equipment .
Just a Reminder 2392-10. :christmaswreath:
Theprimary RESPONSIBILITY for ACHIEVING COMPLIANCE with the Building Regulations rests with the PERSON carrying out the Building Work .
(i) The ElectricalInstallation Certificate required by Part 6 should be made out & signed or otherwise authenticated by a ( Competent Persons or Person(s) in respect ofthe design . construction . inspection & testing of the work .
(ii) The Minor Works requiredby Part 6 should be made out &signed or otherwise authenticated by a (Competent Persons or Person(s) in respect of the design . construction . inspection& testing of the minor work .
(iii) The ElectricalInstallation Condition Report requiredby Part 6 should be made out &signed or otherwise authenticated by a (Competent Persons ) in respect of the inspection & testing of anInstallation . .
(iv)( Competent Persons ) will . as appropriate to theirfunction under (i) (ii) & (iii) above . have a sound knowledge & experience relevantto the nature of the work undertaken & to the technical standards set downin these Regulations . be fully versed in the ( Inspection & Testing ) procedurescontai9ned in these Regulations & ( Employ Adequate Testing Equipment )
(v)The Electrical Installation Certificate will ( Indicate ) the responsibility for design . construction .inspection & testing . whether in relation to ( NEW WORK ) or further work on an ( EXISITING INSTALLATION ) .
2392-10 (- -&-s 2011 :17:
Where design . construction. inspection & testing are the responsibility of ( ONE PERSON ) a Certificate with a ( SINGLE-SIGNATURE DECLARATION ) in the form shown below ( MAY REPLACE ) the ( MULTIPLE SIGNATURES )
Protection Against Overcurrent . Chapter 43 . p/79
430.3. General Requirement. (T )
A protective device shall be provided to break any ( Overcurrent in theCircuit Conductors ) before such a current could cause a ( DANGER ) due to ( THERMAL ) or MACHANICAL effects detrimental to ( INSULATION ) connections . joints . terminations orthe surrounding of the Conductors .
The protection against overload current & the protectionagainst fault current shall be co-ordinated in accordance with section 435.
NOTE :- An overcurrent maybe an ( Overload current ) or a ( Fault current ) :icon_bs:
Inspection & Testing section of anElectrical InstallationCertificates must be signed only by a competent person or person(s)
Regulation : 631.4 - p/196 .
□ ElectricalInstallation Certificates . Electrical Installation Condition Reports &Minor Electrical Installation Works Certificates shall be compiled & signedor otherwise authenticated by a competent person or persons .
In this context . “ Competent “ means having adequate knowledge &experience of the type of work being Inspected & Tested in order to be able to “ Verify “ so far as is reasonably practicable . whetheror not the work meets . the requirements of BS-7671:2008 - First Amendment . 2011 .
□ For Alterations & Additions . it needs to be “ Verified“ that the work complies withBS-7671:2008 - First Amendment . 2011 . &does not impair the safety of the existing installation . Regulation - 633.1. - p/196. it also needs to be confirmed that theEarthing & Bonding arrangements upon which the new work relies for safetyare adequate Regulation – 132.16 . Any defects found in the existing installation. found in the existing installation unrelated to the work being certified .must be recorded on the certificate . Regulation – 633.2. – p/196 .
□ The person(s) responsible for Inspection & Testing thework are responsible for comparing the results with the relevant criteria .Regulations - 612.1. – p/190 . to confirm that the work Inspected &Tested meets the requirements of BS-7671:2008 - First Amendment . 2011 . before signing for Inspection &Testing element of the work on the certificate. for example ! . it needs to beconfirmed that the limiting values of ((Zs )) have not been exceeded .
□ if any Test indicates a failure to comply . that test . theresults of which may have been influenced by the circumstances that caused the failure. need to be repeated afterthe fault has beenrectified . Regulation - 612.1. – p/190 . Defects or Omissions revealed during the Inspection& Testing must be made good before the work is put into service &before the certificate is signed & issued . Regulation - 632.4. p/196.
□ The person(s) responsible for Inspection & Testing mustcompile the Schedule of Inspections & the Schedule of test results . forissue as part of the certificate to the person ordering the work . Regulation - 631.1. p/195 .
Earthing&Bonding arrangements :carols:
Earthing (- Connection of the exposed-conductive-parts ofan installation to the Main Earthing Terminal of that installation . p/27 Bonding (-Bonding conductor . Aprotective conductor providing Equipotential bonding . p/23
2392-10.
Part P of the Building Regulations for England& Wales. :carolers:
Domestic Electrical Installation Work . That is notifiable underPart P of the Building Regulationsfor England& Wales. Only the person(s) responsible for the ( CONSTRUCTION ) of the ( WORK ) are (LEGALLY ) entitle to Self-certify that the Electrical Work Complieswith the relevant requirements of the BuildingRegulations
Mounting Heights of Electrical Equipment in Dwellings . :santa5:
Regulation 553.1.6. p/174.
Requires that a wall mounted socket-outlet is sufficient heightabove the floor or any working surface to minimize the risk of mechanicaldamage to the socket-outlet or to an associated plug & flexible cord duringinsertion . use or withdrawal of the plug .
553.1.6. Asocket-outleton a wall or similar structure shall bemounted at a height above the floor or any working surface to minimize the riskof mechanical damage to the socket-outlet or to an associated plug & itsflexible cable which might be caused during insertion . Use or withdrawal ofthe plug .
Automatic Disconnection of Supply. ( ADS) A requirementof the regulations is that in the event of a fault occurring of negligibleimpedance between Live conductors ( Being / Neutral) or Line conductors & Earth . Supplyis interrupted within the times stated in Table 41.1. BS-7671:2011.
TT. – Uo / 230V . 0.2 for any circuits rated ( Under ) ≤ 32A) & ( 1s ) for any circuit ( Over ) ≥ 32A ) DisconnectionTime could be Met – by the Use of an RCD .
TTsystem – maximum EFLI - ( Zs ) Ω
AnEarth Electrode value of greater than ( 200Ω ) is considered by some to beUnstable . Other use a figure of ( 100Ω) Singlevertical rod Electrodes . “ Depth “ is an Important Factor & a ( 2.4m deep ) Electrode with Initial Résistance of . say ( 300Ω) will be more stable than a shallow (1.2Ω ) rod with an initial résistance of. say ( 100Ω ) Thus the effects of freezing & drying out can be all buteliminated in the UKby installing ( 2.4mDeep Electrodes’ )
Asthe BS-7671:2011. Rightly reminds us . For Non-delay RCDs to BS-EN 61008-1& BS-EN 61009-1
Table 41.5. are Obtained by the use of “ Ohm’sLaw “
Calculation is given in Regulation 411.5.3. ( R[SUB][FONT="Times New (W1)"]A [/SUB]x IΔn ≤ 50V ) [/FONT]
R[SUB][FONT="Times New (W1)"]A [/SUB] ) is the résistance of the Earth Electrode &the Protective conductor ( Zs ) can beused in place of ( R[SUB][FONT="Times New (W1)"]A [/FONT][/SUB] ) ◄◄ “ WORDING “ [/FONT] R[SUB][FONT="Times New (W1)"]A [/SUB] ) is the résistance of the Earth Electrode &the Protective conductor connecting itto the exposed-conductive-parts ( in Ohm’s ) [/FONT] IΔn ) is the Trip current rating of the RCD . 50V ) is the Maximum permitted Touch Voltage .
Calculation )- it is Importantto remember that in most cases the trip rating of an RCD is given in ( milliamps ) Calculation )- to find the Maximum Résistance permissible fora ( 30mA RCD ) - 50/0.03 = 1666.66. Rounded up 1667Ω
411.5..2 )- One or More of the followingtypes of protective devices shall be Use . theformer being preferred ( i ) AnRCD . ◄◄ (ii) Overcurrent Device . MCB.
NOTE 1 . An appropriate overcurrent protective device may be usedfor fault protection provided a (Suitably Low Value of Zs ) ispermanently & reliably assured .
□ Generalpurpose RCDs to BS-4293 . are Used . this is not a problem as they mustdisconnect within ( 200mS ( 0.2s ) this would satisfy Regulation 411.3.2.2. p/53 :- 411.3.2.2. . The maximum disconnection timestated in Table 41.1 shall be applied toFinal Circuit NOT Exceeding( Under ) ≤ 32A )
□ The requirement for BS-EN type RCDs is that they disconnect within ( 300mS ) ( 0.3s ) This disconnection time is not ( Fast Enough )to satisfy the Regulations . & their use could cause some “ Concern “
Regulation do take into Account that a ( Fault Current ) is going to be at least TWICE the TRIPrating ( 2 Δn) of a-the RCD As a FAULT CURRENT is almost certainly going to be ( 2 x IΔn ) a BS-EN Type RCD will comply with theRequirements .
Asthe BS-7671:2011. Rightly reminds us p/295 . BS-EN type RCDs . Appendix 3 . BS-EN 61008-1& BS-EN 61009-1 Operates within the correct time ( 300mS ) at times one ( IΔn ) then it will operate at (150mS or Less at twice IΔn )
Therefore . if the RCD is satisfactory when tested at times ( Half) ( Times One ) & ( Times Five 5 xtimes for 30mA & below Only ) No further tests are required . & it can be Accepted that theRCD is Satisfactory .
p/57- Table 41.5. of BS-7671:2011 . provides maximum values of ( Zs ) which will ensure the correct operation of theRCD .
The maximum fault current which can flow between Live conductorsis called ( PSCC ) The maximum fault current which can flow between Live conductors& Earth . ( PEFC )
2392-10 (- As a Tester . You are required to determinethe value of each of these TWOCURRENT.S.
( By Measurement ) -&-s . The Highest Value must be recorded . Test Certificate “ Known as ( PFC ) -&-s
2392-10 :- InstalledEquipment in an Domestic Installation must be capable of withstanding the Maximum Fault Current ( PFC) which could flow at the point at which it is installed . for -&-s point of View . Ensuring Equipment is to the British Standardwill ensure Compliance .
Regulation s 612.11. ProspectiveFault Current .
2392-10. The prospective short-circuit current & prospectiveearth fault current shall be MEASURED . calculated ordetermined by another method , ( At The Origin , & other relevant points in the Installation .
Theadequacy of the Existing Installation istherefore required to be Assessed in THREE-AREA.S .
□ Existing Equipment – including that of theSupply . may have to carry Increased Load . ( it is necessary to establish that the rating& condition of all appropriate equipment within an Installation Overcurrents / MCBs )
□ Earthing & Bonding arrangements . ( Verification of the means of Earthing bydetermination of the External Earth Fault Loop Impedance ( Ze ) 313.1. ( iv ) • As a Measured value to verify that theintended means of Earthing is both present & of the expected value . • Ascertaining that the Earthing Conductor isof Adequate Cross-sectional area .
□ Certain additional considerations . ( The ratings of cables in the Installation )
2392-10:- Upgrading of an Existing Installation. where necessary .
□When an Existing Installation is NOT adequateto support a proposed Addition or Alteration safely the work must NOT proceed .
□The client must be Advised immediately & preferably in writing .
□ The necessary upgrading work should be recommendedto the client .
□ When the client’s consent has been given . theupgrading work should be completedbefore the Addition or Alteration is put into service .
Installation. Additionto .or upgrading of . main protective equipotentialbonding in an Installation relying on the protective measure ( ADS ) for Protection .
Whereprotection is provided by ( ADS ) Regulation 411.3.3.
610.4. p/189 .
For an Addition or Alteration to an existing installation . itshall be VERIFIED that the Addition or Alteration complies with the Regulations& does NOT impair the safety of the EXISTING INSTALLATION .
110.1.2. p/14 . ( vi ) “ SCOPE “ Addition or Alterations to installations & also parts of the existing installationaffected by an Addition or Alteration ◄◄ [ Safety of the Existing Installation ]
610.5. The Verification shall bemade by a Competent Person .
2392-10: -&-s . Q ) Circumstances which require an Initial Verification . A) New installation(s) or Additionsor Alterations .
612.9. : Earth Fault Loop Impedance . 612.10 : Additional protection – RCDs . [ Toconduct the Test on – “ Earth Fault Loop Impedance “ before “ Additional protection “ Why ? . A faulty RCD can pose a problem . “ Shock Risk “ if the Loop Impedance is Inadequate.
UnderFault Conditions . the Earth is a Live Conductor. CPC .
CPC.Form part of an Earth Fault Loop path within an Installation . It’s purpose is to carry any current which is caused due to anEarth Fault & forms part of the (ADS ) Important . -&-s
Any “ Article(s) “ provided by this forum in this section . assume that the Designer & Installerintend to comply fully with the requirements of the 17[SUP]th[/SUP] Edition . BS-7671:2008. No 1. 2011
SteelWire Armour used as a CPC . “ Useful Junk “ .
Table 54.7. p/162 . Minimum cross-sectionalarea of protective conductor in relation to the cross-sectional area ofassociated Line Conductor .
Calculationto use which will give us the minimum CSA of the Steel Wire Armouring which is suitable foruse as a ( Protective Conductor ) Withoutany further calculation other than ( Zs )
2392-10: Using a ( 10mm[SUP]2[/SUP] two core ) - ( 70°C) thermoplastic . SteelWire Armour Cable . Using the Armour forthe CPC.
Calculation– minimum CSA . of Armouring. ? [ k[SUP]1[/SUP] / k[SUP]2[/SUP] x S ]
Table. 43.1. or 54.3. Value ( k ) for aCopper Conductor is ( 115 ) 54.3. is for theprotective conductor & that we are looking for Value ( k ) for the Line Conductor. ( Copper Conductor ) it will have the same Value ( k ) as it would have if itwere to be Used as a CPC .
p/85. Table ( 43.1. ) Values of ( k ) for CommonMaterials , for calculation of the effects of Fault Current for disconnectiontimes up to ( 5 sec )
p/161. Table ( 54.3. ) Values of ( k ) for protectiveconductor ( INCORATED ) in a ( CABLE ) or bunched withcables . where the assumed Initial Temperature is ( 70°C )or ( Greater )
p/161. Table 54.4. Value ► ( k ) for ► ( Steel Sheath Armour ) is ► ( 51 ) Note - ►►( 70°C ) thermoplastic. Calculation– 115 ÷ 51 x 10mm[SUP]2[/SUP] = 22.54mm[SUP]2 [/SUP]
□ Any “ Article(s)“ provided by this forum in this section. assume that the Designer &Installer intend to comply fully with the requirements of the 17[SUP]th[/SUP] Edition . BS-7671:2008. No 1. 2011
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