***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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2392-10. Your Assessor . is looking for this principle .

p/25. CompetentPerson .

Aperson who possesses sufficient technical knowledge & experience for thenature of the electrical work undertaken & is able at all times to preventdanger . & where appropriate . injury . to him/herself & others .

This Definition is aligned with . the Memorandum of Guidance on the Electricity atWork Regulations 1989 – ( HS(R) 25 ) Guidance onRegulations
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BS-7671:2008. No 1 . 2011 .

411 . Protective Measure – Automatic disconnection of Supply .

Disconnection Times .
p/53. Disconnection circuit(s) & circuit(s) not covered by Table 41.1.

p/54- 411.3.2.3. TN- : 5 s maximum .
p/54- 411.3.2.4. TT- : 1 s maximum .
p/60- 411.8.3. Reduced Low-voltage system(s) . 5s maximum .
p/179- 599.10.3.3. Outdoor Lighting Installations . 5s maximum .

 

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411 – Protective Measures / Automatic disconnection of the Supply .

Fault Protection .

2392-10 . Three Components “ That is Important“
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p/53- 411.3.1.1. ProtectiveEarthing .
411.3.1.2. Protective Equipotential Bonding .
411.3.2. Automaticdisconnection in case of a Fault .

 

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Justa Reminder .

Part 5 – Selection & Erection of Equipment .
p/169- Chapter 55 – Other Equipment .

p/172- 551. Low VoltageGenerating Sets .

551.7.2.
i) The conductors of the final circuit shall meet the following .

( Iz ≥ In + Ig )

Where :
Iz ) is the current-carrying capacity of the final circuitconductors .
In ) is the rated current of the protective device of the final circuit.
Ig ) is the rated outputcurrent of the generating set . &

ii) not be connected to afinal circuit by plug & socket . &
iii) A 30mA RCD on thefinal circuit shall disconnect all Live Conductors .
iv) The Line & Neutralconductors of the final circuit & of the generating set shall not be connected to Earth.
v) Disconnection times muststill be Met .

This regulation does not apply to an Uninterruptible Power Supply provided to supply specific items ofcurrent –using equipment within the final circuit to which it is connected .

 

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p/163- 543.2.7. Earthing Tail Requirement .

Where the protective conductor is formed bymetal conduit . trunking or ducting or the metal sheath and/or armourof a cable . the earthingterminal of each accessory shall be connected by a separate protective conductor to an earthing terminal incorporated in the associated box or other enclosure .

 

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2392-10.

Colour Coding of the Insulation ensures correct Polarity atTerminals . ( Insulating Tape ) Tail’s

 

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Sorry . Grand kids all day . can’t get my head stuck into books . :banghead:

CableSizing .

Sizingof an Electrical Load . “ Cable “

Importantthat the cable can :-

□ Operate continuouslyunder ( Full Load ) without being damaged .
□ Withstand the worst ( Short Circuit(s)Current(s) flowing through the cable .
□ Provide the load with a suitable voltage . ( Avoid excessive voltage drops )

• Ensure operation of the ( Protective Device during an Earth Fault )

Definitions . p/26.
EarthFault Current . A current resulting from a Fault of negligible impedancebetween a Line conductor & anExposed-conductive-part ( or a Protective Conductor )

Résistanceof the Protective Earthing. ( PE ) conductors mustbe low enough to permit the passage of current necessary to operate the Protective Device .

Q/. When . Earth Fault Loop Impedance should be measured .
(Using a suitable instrument ) 612.1. BS-EN 61557.

□ Installation work is completed .
□ Checking Inspection / Visual . & Testing has been carried out .
□ Supply has been applied .

 

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Thenominal voltage is 230V . The ( Maximum voltage drop ) from the “ Point of Supply“ where the Consumer Mains joints to the Installation(s) cable(s) .
“ Power “ Toany part of the Installation must NOT be more than ( 5% )

Thisis to ensure that “ Appliances will operate as intended . ( 5% ) Voltage Drop = 11.5V .
p/314- Table 4Ab –Voltage drop . ( Lighting – 3% ) - ( Power – 5% ) DNO .

(i) Low voltage installation(s) directly from a Public Low voltage …………. Etc .

Appendix. 4 of BS 7671:2008: No1 . (wiringregulations) states that 'The voltage drop between the origin of aninstallation and any load point should not be greater than the values in Table 4Ab , expressed with respect to the value of the nominal voltage of the installation'.

To help select cables that comply with the percentagevoltage drops specified above, the cable data given in Appendix4 of BS- 7671:2008: No 1 . supplies values from which the appropriate calculations can be made. Thesevalues are expressed in terms of a current of oneampere for arun of one metre .

p/130 - 525.101.
The above requirements are deemed to be satisfied if the voltagedrop between the Origin of the installation ( Usually the supply terminals )& a socket-outlet or the terminals of fixed current-using equipment doesnot exceed that stated in Appendix 4 .

P/256 . Table of Voltage Drop. 6 .
In the tables . values of voltage drop are given for a current of one ampere for a metre run . i.e. for a distance of 1m along the route taken bythe cables .

 

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RCDswork on . Current Alone .

Ifthe Outgoing current doesn’t Equal thereturning current then it should Trip .

( RCDs operateon Current . in order for current to flow youmust have a ( Potential Difference)

p/34- Residual Operating Current :- Residual Current which causes the RCDto operate under specified conditions .


□ Regulationsrequiring CPCs in lighting circuits were introduced in 1966 .

□ ElectricalExtension Leads . The longer the run ofcable . The more Résistance . mort Heat. CoP.

 

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UsefulJunk

Lighting / Lamps. every night.

16. hour / day . x 7 . day / week . x52 weeks = 5840 / hours . ( 16 x7 x 52 = 5840 h/s )

3. hour / day . x 5 . day / week . x 20 weeks = 300 / hours . ( 3 x 5x 20 = 300 h/s )

 

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□ Abstract/ Scope .

Laysdown requirements for the Verification . by inspection & testing . of thecompliance of the installation with the relevant requirements of other parts of EN-60364 .Criteria for testing are given & tests described . Thispart is concerned only with new installations : it is not concerned withinspection & testing of existing installations : However . the criteria for inspection & the tests described may beapplied . if thought appropriate . to existing installations .

Keywords - Building :Electrical installation : Verification : Initial verification .

Other standards to which reference is made in the Regulations . No 1

p/290- Superseded by – HD – 60364-6: 2007 . Initialverification


□ Reference
Low voltage electrical installations . Part 5-54 : Selection anderection of electrical equipment – Earthing arrangements . protectiveconductors & protective conductors

Abstract / Scope .
Addressesthe earthing arrangements . protective conductors & protective bondingconductors in order to satisfy the safety of the electrical installation . Hasthe status of a basic safety publication in accordance with IEC Guide 104 .

p/290- HD 60364-5-56 : 2007 - EarthingArrangements . No 1

Keywords – Building .Electrical installation . Earthing arrangement . Conductor; protection .


□ Reference – HD60364-1 : 2008 . p/290 .

Low-voltage electrical installations . Part 1 : Fundamentalprinciples . assessment of general characteristics . definitions .

Abstract / Scope .

Givesthe rules for the design . erection . and verification of electricalinstallations . The rules are intended to provide for the safety of persons .livestock and property against dangers and damage which may arise in thereasonable use of electrical installations and to provide for the properfunctioning of these installations . IEC-60364-1 . applies to the design . erection & verification of electrical installations suchas those of . a ) residential premises : b ) commercial premises : c ) publicpremises : d ) industrial premises : e ) agricultural & horticulturalpremises : f ) prefabricated buildings : g ) caravans . caravan sites &similar sites : h ) construction sites . exhibitions . fairs & otherinstallations for temporary purposes : i ) marinas : j ) external & similar installations : k ) medical locations : I ) mobile ortransportable units : m ) photovoltaicsystems : n ) low-voltage generatingsets : IEC- 60364-1 covers : a ) circuitsupplied at nominal voltages up to & including 1000V a.c. or 1500V dc : b )circuits . other than the internal wiring of apparatus . operating at voltagesexceeding 1000V & derived form aninstallation having a voltage not exceeding 1000V a.c. for Example . dischargelighting . electrostatic precipitators : c ) wiring systems & cables not specifically covered by the standardsfor appliances : d ) all consumerinstallations external to buildings : e ) fixed wiring for information &communication technology . signalling . control & alteration of theinstallation & also part of the existing installation affected by theextension or alteration .

 

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Adisadvantage of some RCBOs is that you cannot tell if they tripped by Overcurrent . or an EarthFault . This can make Fault finding harder .

RCDshave to be designed to interrupt fault currents. They will beat the Fuse / MCB in doingso . in the case of a fault current to Earth . RCD must trip within ( 0.04seconds ) - ( Unless time delayed type ) whereasFuse / MCBs is allowed ( 0.4 or 5 seconds ) dependingon circumstances . :banghead:

RCDscan also be switched OFF manually & can take the place of the IsolatorSwitch in the Consumer Unit . ( if theybreak Line & Neutral )

 

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2392-10: RCDs - Nuisance Tripping . One Cause . :13:

Oneof the common cause of RCD trips usuallyoccurs when the RCD is fitted for the ► First Time ◄ (- Theyshow up Neutral / Earth Faults NOT previously known to exit .
Currenttaken by the Load does NOT flow equally in the Neutral & Live conductorsthrough the RCD it will see this as (Residual Current & Trip )

Thisis NOT anuisance trip !!. The RCD is correctly stating there is a Problem. :banghead:

Basics.
i) residual - resi “ dual “ / Meaning . Two. L/N
ii)residual current “ Current “

 

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Basics.

ii)residual current “ Current “

AnRCD protects by constantly monitoring the Current flowing in the Line & Neutralconductors . Under normalcircumstances .

Current flowing in the two Wiresare ( Equal ) T&E :13:

UnderFault conditions ( Imbalance Occurs ) - Trip .

 

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Basics.

RCDshave another “ Important Advantage “ they reduce the risk of Fire bydetecting Leakageto Earth in Cables .
RCDswork on the principle “ What goes IN must come OUT .

Comparingthe “ CURRENT“ flow in both Line/ Supply . & Neutral / Return .