***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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The following errors occurredwith your submission :39:

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Part1 ) “ This is some thing I knocked up Amber . “ Wording comes in different Meaning on Exams . But they all work aroundthe same principle(s)

Firstly)- What is ( Zs) in Definition . Earth Fault LoopImpedance . ( Ω ) 41.3 – Maximum Earth Fault Loop Impedance .

2392-10.

Q)- A Prospective Earth Fault Current Test.
needsto be carried out on a Domestic Installation .Which has a Type “ B “ circuit breaker fitted .

State ( Which instrument(s) can be used . The testvoltage & current supplied by the Meter.
Whatequipment is likely to be fitted to the circuit .
State( the precautions needed to be takenprior to the test .
Describethe Test .

i)State ( Which instrument(s) can be used. The test voltage & current supplied by the Meter.

AProspective Earth Fault Current Test .
( PFC Tester ) – or Loop ImpedanceTester : with function ?
Thevoltage range the meter will work on it from ( 50Vto 500V ) which is taken form the Supply it is Plugged into .

Workon is from ( 50 V ) to ( 500V ) Which istaken from the supply plugged into .
Itmeasures the current between Line & Neutral across an Internal Impedance inside theTester . ( PFC ) = I = V/R = 230 / 0.5 =460A )
Yourmeter . will return a Value . 0A up to ≈ 50kA . ( 2392-10 – Youwill not use this Method in Initial Verification )

Asthe regulations say . ! Values can also be ascertained by (Calculation or Measurement ) “ Meaning “ Determined by other ways . 612.11

Thisis a Live Test . You may be measuring Live Energised Conductors ( Whenusing Clip-on Leads ) when -&-s are looking for . ?? Safety at all Times .

 

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Part2 ) Firstly : as Tester. 2391-10 & 2392-10. :39:

Secondly : Competent Person .



Competent Person . As this notthe first Live Test . ( PFC ) you WILL HAVE Informed persons . “ Meaning “

TheWhy’s . ►Warning Signs – Informing persons whocould be AFFECTED by “ LiveTesting “ ◄◄ This is what -&-s like to Hear .



What other Precautions Required. ?? Are you not the Person conducting the TEST. ◄◄ Yeah



1)Check the condition of the “ Test Instrument “& “ Probes / Leads

2)Check Test Leads & Probes conform to ( GN-38) ↔ full Title / HSE .

3)What –&-s . harp on about ?? Working with Live Terminals / Careful not to TOUCH any LIVE PARTS ( 17[SUP]th[/SUP]Edition 2008 )



MCB32A – BS-EN 60898



So. for the sake of the Regulations .

Youshould check your reading against the Time Current Graphs for relevant devicesto get an Actual Disconnection Time . 2391-10 ( 460A ) ?? 0.1 s / 5s



2392-10- You should check your Disconnection Time Table 41.1 ( TN-0.4 or TT-0.2 )



Example. ( PFC ) = I = V/R = 230 / 0.5 = 460A )

( 230V ÷ Ze / 0.28Ω= 821A )

( Ia ) /Operation of protective device within the time stated – Zs = Uo/Ia . 6A ÷ Current / 30A = 0.2s



TwoTests . Here . 612.11. ( PFC )



Prospective Short Circuit Current . …. Line & Neutral

Prospective Earth Fault Current . ….. Lineto Earth



Measurethe ( PFC ) at the Originof the Supply .

Etc. Check that the test instrument . Leads. Probes & Crocodile Clips . -&-s GN-38



►►►Check the Polarity Indictor ( if Any ) on the instrument for correct connection

Usingthe ( PFC ) Loop Tester set the selector switch to ( PFC ) & the range switch tothe highest setting ( test for PFC Value)



Youcan ( Reduce the Range switch to a Lower Setting ) to obtain a more AccurateValue .



Withthe . Megger 1552 / you have two settings . (PFC → No-Trip ) ( PFC → Loop– Hi )



Ifthe voltage measured at the time of test is 230V & the measured value ofFault Loop Impedance between Line & Neutral at the Originis ( 0.05Ω )

Maximumprospective Short – circuit = 230V / 0.05 = 4600A ( or 4.6 kA )



If( Ze ) is known & the Looptester does not have the facility to measure EarthFault Current .

Itcan also be Calculated by using the formula . ( Ipf ) = Uo / Ze .



p/35– Regulation . ( Ipf ) Prospective Fault Current .

p/36– Regulation . ( Uo ) Nominal Line to Earth voltage .

p/36– Regulation . (Ze ) External Earth Fault LoopImpedance .



3-Phase Installations the ( PFC ) recorded is Twice ( 2 x ) the Maximum SinglePhase Value Measured .

 

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InsulationRésistance . in your own words . Example. :6:

Example- Table 61 (- SELV = 50V/ A.C . to 250V /D.C.. ( V ) to ( MΩ ) ≥ 0.5 . (Mains to D.C. Current ) Remember . MinimumInsulation Résistance “ Wording “ . ≥ 0.5 - MΩ .

 

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RingFinal Circuit . Basics. :6:

Statethe effect on Conductor Résistance when Cables are Connected in Parallel .

Current in a Parallel Circuit.

Ohmslaw states that the Current is ( Inversely Proportionalto the Circuit Résistance ) Thisfact is True in Both ( Series ) & ( Parallel ) Circuits .

Thereis a Single Path for current in a ( Series )circuit .
Theamount of current is determined by the Total résistance of the circuit &the applied voltage . In a ( Parallel ) sourcecurrent divides among the Available Paths .

 

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Apprentices. :39:

Revision– Factors affecting Résistance .

Therelationship between the length of a conductor & its résistance is said tobe ( - Directly Proportional. / to its Length ( L )

Therelationship between the Cross-sectional Area of a conductor & its résistanceis said to be ??? Proportional.

• Thicknessof a Conductor . “ Cable “ Wire “

The Cross – sectional area of a conductor ( Affectsthe Résistance ) Thicker Wire provides ( Low Résistance) because they have more space for Electrons tomove .
Fevercollisions occur .

(Smaller )- Wire of the same substance ( Provides HigherRésistance ) because they Offer Less Space for to move around in .

► If you still get them in-&-s . How to remember . ( Proton is Positive ◄►You can remember that because they both start withthe Letter ( P )◄◄◄ Two / Ps

Proton = Positive . ( Two. P ) -&-s :6:
Neutrons= Neutral
Electrons= Negative .

 

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Extra Low Voltage . p/31

AnyVoltage in a Domestic Installation UP – TO ( 50V ) Thinkabout - SELVor PELV

SELV or PELV

ElectricalProduct may also be Indentified as a ( PELV ) - ProtectiveExtra – Low – Voltage . ( Low-Voltage but connectedto Earth ) watch this -&-s . :6:
SELV . Separated Extra – Low –Voltage. ( Low-Voltage but with Output Isolatedfrom the Input ) watchthis -&-s . :6:

 

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Apprentices)- some Testing matter to think about . Numbers . Yeah . :willy_nilly:

( R1 + R2 ) Testing – method( 1 )
( R2 ) Test - method ( 2 )

Testmethod ( 1 ) Continuity .
Testmethod ( 2 ) Continuity .

Zs = Ze + ( R1+ R2 ) Formula – Calculating – Earth – Loop – Impedance.

 

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Two/ Point HERE . 2391-10 . Do NotUse The Wording(s).

Multi – Function – Tester . ( MFT ) Ambers doing Handstands on this Matter . Give -&-s what they want to HEAR . Professionalism. Not a D.I.Y. er :89:

Thisgoes for you as well 2392-10 . Combined Instrument that can perform all the requiredTests ( Not a “ Part– P or 17[SUP]th[/SUP] Edition – Tester) ◄◄◄

►►Right Chaps . We keep this for On Site Only . “ Megger “ SlangTerm for an Insulation Résistance Tester .

 

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UsefulJunk .

Termedan “ Extraneous-Conductive-Part “
“ Water Pipe “ Not part of an Electrical System /Equipment . Froma Tester point of View .

P/27. Regulations / OverloadCurrent . An Overcurrent occurring in a circuit which is “ ElectricalSound “
Example– To much plugged into a KitchenRing ?? Washing machine / Tumble Dryer . Kettle . Toaster . T.V. :89:

2392-10 . PS. I can only give Guidance . Remember . as a Designer . The Kitchen Ring Final Circuit is always 100% / Maximum Demand . Yeah . Table1B . Colum 9 .
Point to Note : ( kW ) ◄◄◄◄ ► Real / Power . Yeah :89:

 

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Watchyour Wording here . Yeah ( LV) Regulation(s) . p/31 .

Low / Voltage :

AnyVoltage in a Domestic Installation . ABOVE - ( 50V ) → Band 11Circuits .

AnyWiring that carries ( Main Voltage ) → Band 11

 

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Certification& Reporting . 2392-10 . :6:

Minor Electrical InstallationWork Certificate . -&-s (- This is the documentthat must be Issued if an Existing Circuit is Worked On .

 

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ThePart P ( BR ) BuildingRegulations :smilewinkgrin:

Ineffect you have to .

Design ) The installation . soit is safe as it can be . ( P1 ) ElectricalSafety ( BR)
Install : The wiring &accessories to the standard of BS-7671 .
Inspect & Test : Your new work for compliance with BS-7671 .
Certificate : The work you havecompleted in compliance with BS-7671 .

Apprentices(- Ohm- Law . is the cornerstone ofelectrical calculations .

Referringto the Triangle ( Four Values ) V . I .R . & Z . – ( R or Z)

Symbol– ( V ) : Meaning – Electrical “ Pressure “ : Unit / Volt : Unit Abbreviation ( V ) :
Symbol– ( I ) : Meaning – Electrical “ Current “ : Unit / Amp : Unit Abbreviation ( A ) :
Symbol– ( R ) : Meaning – Electrical “ Résistance “ : Unit / Ohm : Unit Abbreviation ( Ω ):

Symbol– ( Z ) : Meaning – Electrical “ Impedance “ : Unit / Ohm : Unit Abbreviation ( Ω ):

Ifwe Compare an Electrical Circuit to a Garden Hosepipe .

•When you turn on the Water to the hose – The system will stabilise to a steadyflow .
•The pressure is constant & a set current is flowing .
•The flow is governed by the ( Bore ) résistanceor impedance of the pipes “ And “ the pressurepushing the water along .

Apprentices(- if you crimp the pipe . The waterwill slow down . This is because the résistance orimpedance of the pipes ( has just increased ) :- Therefore .
Toget the same current flowing again you have “ TwoChoices “

-Turn up the pressure to increase the FLOW
-Decrease the résistance / impedance by removing the “ Obstruction“ of the pipe .

Canyou work this as . More or Less the same with Electrical Circuit (s)

As I can not download Picture YET . am Working on it ?? Electrical -Drawing ◄

Wewill use ( R ) as you know it is the Symbol forelectrical résistance or loading . ( Scenario- Table Lamp at your bedside )

[V = 10V . I = 5A . R = Ω ] -→ > 5A -→ R = ?Ω ← 10V →. R = V/I – R = 10V ÷ 5A = 2Ω
[V = 100V . Z = 1000Ω . I = A ] -→ > I = ?A -→ 1000 = Ω ← 100V → . I =V/Z – I = 100 ÷ 1000 = 0.1A
[I = 100A . R = 1.0Ω . V = ?V ] -→ > 100A -→ 0.1Ω ← V =?V → . V = I x R - V = 100 x 0.1 = 10V

 

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Part( 1 )

Keepit Short for Understanding . :smilewinkgrin:

Firstly (- Themost important thing to remember . inany -&-s . ( ADS ) Automatic Disconnection of Supply . 17[SUP]th[/SUP] Edition 2008 . / Red Book – 415.1.1.
Thisis a primary method of protection from Electrical Shock .
-&-s point of View (- Insulation . Barriers . Earthing. MCBs. These four will stand you fast on (ADS ) RCDs . “ Testing “

Asyou are heading towards 2392-10 .

Earthing . Does a RCD need . “ Earthing “ . Important -&-s . What is the reason for EarthLoop Impedance . ?? Before we test any RCDs . ????? HINT / CPC
wouldan Earth Fault Loop Impedance test . ( Zs ) becomplete without an Earth / Polarity . ( Everything has aknock on effect ) for Testing .Yeah

Barriers . 2392-10 point ofview – 416.2.2. Top of ConsumerUnit ( CU ) IPXXD or IP4X . ( Shallbe possible ONLY by the USEof a key or TOOL “ Screwdriver“ +
Barriers . 2392-10 point ofview – 416.2.4. Side & Bottom of Consumer Unit ( CU ) or IPXXB or IP2X . ( Shallbe possible ONLY by the USEof a key or TOOL “ Screwdriver“ +

2392-10. IP – Rating : Arating given an “ Enclosure “ to describe its “ Résistance “ to ( Solids &Water Intrusion ) it is expressed in Numbers . IPX4 ??

Insulation . Insulation Resistance . ( IR ) They are not Crossed / Polarity . ? ( ifit is not . Initial Verification / Age / Wear& Tear on Cable(s)
Insulation . Where they are no breaks in the Cable(s)Dead-Short . ( Fit for its Extended Use )
Insulation . Can we use the Term ? Fault / Finding . Insulation Resistance .

MCBs . To ensure correctprotection form “ Overloads “ it is Importantthat the “ Protective Device - MCB “ operatingcurrent ( I[SUP]2[/SUP][SUP][/SUP]) is not bigger than ( 1.45 / times ) the current capacity of the Cable ( Iz ) The rating of the MCB - ( In ) MUST not beGreater THAN the CABLE carryingcapacity ( Iz )

Asfrom -&-s point of View - OperatingCurrent of the protective device is always larger THANits RATED VALUE .

2392-10point of view – 514.1.2. Installation of Cables . I canStress this Enough ◄► Identification & Notices . Thiswill bring out the Professional side ofyou . “ Tester “

( T ) As Far as is reasonably practicable . wiring hallbe so arranged or marked that it can be Indentified for – Inspection / Testing/ Repair or Alteration of the Installation .
(Can we say here . “ Maun Bonding Conductor has to be Identifiable “) If One has to Test it . would it safe Time / Money . ???

 

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Part( 2 )

AsDesigner in the Making :smilewinkgrin:

Regulation(- Chapter 521.3. p/97 ) Types of WiringSystem .
TheRegulations are giving you Examples . Yeah .

Table4A2 – gives Examples of installation methods of cables includingreference methods for obtaining Current-Carrying-Capacity whereit is considered that the same current-carrying-capacities can safely be Used .

TheRegulations always gives an Option 99.9% itis Not Implied that such Methods must be Employed or that Other Methods are Prohibited. Etc . Learning Curve


WhereExams are concerned . ( Earthing &Bonding are Two DifferentMeanings ) 2391-10 / 2392-10

Apprentices(- The regulations require the Earth to be HALF the SIZE of the Main CircuitConductor .

The- Whys . The Main Earthing Conductor . 543.1.3. States that where it is Desired Not toCalculate the minimum size of a Protective Conductor.
(Using the Adiabatic Equation ) Table 54.7 . p/130 . Should be Used -

2392-10- As you know The size of Mater Tails in Domestic Installation(s) is 25.0mm[SUP]2[/SUP] - Read this Carefully ◄
Table54.7 . Half the LineConductor size would be ( 12.5mm )

Froma Designers point of View – Manufactures do not produce this SIZE . So the next size UPwould be ( 16.0mm[SUP]2[/SUP] )

2392-10– Table 54.8 . p/134 . Minimum cross-sectional-area of the Main ProtectiveBonding Conductor .

Note : Local Distributors Networkconditions may Require a Larger Conductor . ( DNO )

Apprentices(- Continuity Testing – Test performedon a circuit to make sure the Earth Reachesthe End of it . Yeah .
Circuit-Protective-Conductor . ( CPC ) -&-s
Earthing-Conductor Regulation . p/32 .. This cable is the Last Path out of the Domestic Installation . for Fault / Current . itconnects the system Earth to the Main-Earthing-Terminal . ( MET ).
Main-Protective-Bonding-Conductor .Earth cable that is run to the Main/Incomer of any service to a DomesticInstallation . Usually – Gas . Water .

Fault Protection . ( ADS ) Regulations . 411 .
Thisis a System of putting in place a Protection against ElectricShock . in the Event of a Fault Situation. ( This takes us down many Paths . Yeah. for this matter ADS )