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
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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 .
( PFCTester ) – 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 .
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 .
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
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:
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 .
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:
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
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 . ???
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 )
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