***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 : Learning Curve .

MK. Residual Current Devices ( RCDs ) D/P

BS-EN 61008: 1995 .

17[SUP]th[/SUP] Edition 2011 . Regulations . 537.2.2.2. & 537.3.2.2.

537.3.2.2. A device for switching OFF for mechanical Maintenance or acontrol switch for such a device shall require ( Manual Operation )

The ( Open Position ) ofthe contacts of the ( Device ) shall be ( Visible ) or be ( Clearly ) & ( Reliably Indicated )

Note : Theindication required by this regulation may be ( Achieved ) by the use of the (Symbols . “ O “ & “ I “ ) to indicate the ( Open ) & (Closed position respectively )

 

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2392-10: Let’s notforget . Fan Isolator can be Usedas a Double pole or T riplepole Isolator .

 

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ElectricalTesting .

TheElectrical Contractor is charged with the responsibility to carry out anumber of tests on an electricalinstallation .

Thereasons for testing the installation .

• To ensure that theinstallation compiles with the IET Regulations . 2011
• To ensure that theinstallation meets the specification .
• To ensure that theinstallation is safe to use .

 

[spaldingsparks]

Re: ***Cont../ Useful Information for Electricians’ & Apprentices***

Hi Amberleaf
Like the posts
I would also like to mention the wiring up of 3kw Immersion heaters, I have come accross a few over the years (old me) and if a standard 13A fused spur has been used they can suffer from the constant load (Heat Damage) as the circuit should be on its own, a 16amp MCB feeding a 20 amp double Pole switch works far better and then as seems to be common now days the addition of shower pumps ETC by the dreaded plumbers can still be run on a fused spur from the primary side of the DP Switch.
I hope this extra info helps all

 

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Functional Earthing . ( FE )

Q/ . if an RCD / RCBO is provided with a( functional earthing ) conductor . – for -&-s Q/As . Coloured White.
Q/ . May this conductor be connected toan Earthing Terminal ?

A/ . Yes .
Thepurpose of this conductor is to allow a (Return Path ) for the Electronic Circuit . if the Neutral is disconnected . ( To ensure the RCD still operatescorrectly )

Theconductor does NOT perform a Protective Earth Function .

RCBO. Will normally have two circuit(s) for detecting an ( Imbalance& Overload ) Same interrupt method ( Imbalance/ Trip RCD / RCBO . Overload/ MCB .

Testing / Verification .

Impedance – ( EarthFault Loop Impedance )

Q/ . When existing circuit(s) are extended or new circuit(s) installed . What limiting factors affect the ( Length of the Circuit )
A/ . Limiting factors - Voltage drop & Earth Fault Loop Impedance.

CircuitRoute – Length based on Loop Impedance . VoltageDrop . ( Vd ) Single-phase. Line & Neutral - Max 5% of 230V . Power

 

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Q / State the three generalrequirements to which the installed equipment must conform when carrying out anInitial Inspection .

i) The equipment is incompliance with standards . To the correct BS - or BS-EN .
ii) Correctly selected& erected in accordance with BS- 7671:2008: No 1: 2011
iii) It is not visiblydamaged .

State :-

Q / . i) When an InitialInspection & Testing should becarried out . 610.1. p/189
ii) The precautions to betaken during an Inspection & Testing

A / . i) During and on completion . before being put into service.
A / . ii) Avoid danger topersons . livestock and damage to property . 610.1. p/189

Justa reminder . 2392-10 . -&-s . 2012. The Q/As . are in the Regulations& GN-3.

632 – Initial Verification . p/196
632.1– 632.2. 632.3. 632.4. ◄ Important in -&-s Q/As . 2392-10 . No 1 2011

 

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Reporting. 2011

Electrical Installation Condition Report . 2392-10 : -&-s Q/As - 2012

The ElectricalInstallation Condition Report . ( EICR ) is intended to beissued when a ( Periodic Inspection ) of an electrical installation has been carried out .

The ( EICR) does NOT certify ANYTHING& . HENCE . must NOT be ISSUED tocertify NEW electrical installation work . ◄◄ 2392-10 : -&-s - 2012

Thepurpose of the ( EICR ) is to REPORT on the condition of an EXISTING electricalinstallation ◄◄

Ultimately. present one of two OUTCOMES .

□ Satisfactory. The installation is deemed safe for continued USE .
□ Unsatisfactory . Oneor more issues of safety have been IDENTIFIED .

 

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UsefulJunk . p/178

No Lampholder may be used on circuit(s) exceeding 250V – IET Regulation 559.6.1.2.

&all Metal Lamp holders must have anEarth Terminal .

Flexible Cords . Deleted byBS-7671:2008 . No 1 . P/28
Flexible Cable . A cable whose structure & materials make itsuitable to be flexed while in service .

 

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□ Intermediate Switching .

The action of the Intermediateswitch is to cross-connect the “strapping wires “
This gives us the ability toroute a supply to any terminal depending upon the switch contact position’s .

Intermediate Switching has two position’s.

□ Copper has better conductivity for a givencross-sectional area .

□ Ambient Temperature .
Current-carryingcables produce heat . & the rate at whichthe heat can be dissipated depends upon the temperature surrounding the Cable.

□ Direct Sunlight .
Cables sheathedin ( PVC ) should NOT be installed in positions where they are exposed todirect sunlight because this causes them to harden & crack . Ultravioletrays leach out the ( Plasticiser in the PVC ) making it hard & brittle .

Earthing:- p/27

BS-7671 defines “ Earthing “ as a connection of any exposed conductiveparts of an Installation to its Main Earthing Terminal .
This is done toensure that all the “ Metalwork “ associated with the Installation(s) is effectively connected to the General Mass of the Earth .

This means that. in the event of an Earth Fault . the voltage developed to Earth is restrictedto ( 230V ) this is the case even on a (400V ) three-phase supply . where automatic disconnection of the supply can beachieved .

Bonding:- p/23 .

BS-7671:2011. fails to define Bonding – but does define a ( Bonding Conductor )
Thisis a ( Protective Conductor proving Equipotentinal Bonding ) this in turn is defined as an ( ElectricalConnection maintaining various Exposed Conductive Parts & Extraneous Conductiveparts ) - Substantiallythe same Potential .

In Order forCurrent to flow . TWO conditions have to be MET :-

i) There has to be a circuit for current to passalong .
ii) There has to be a ( Potential Difference – Voltage )

 

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Useful Junk .

230V a.c. RCBOs. Commercial / Industrial - Flying neutral lead . 700mm ( equivalentto 27.6 inches )
230V a.c. RCBOs. Domestic – Single pole . - Flying neutral lead . 200mm ( equivalentto 7.87 inches )

 

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2392-10 . No - 2011

The test procedures must be followed carefully & inthe ( Correct Sequence ) As indicated by IET Regulation(s) - 612.1. p/190 .

This ensuresthat the ( ProtectiveConductors ) are correctlyconnected & secure before the ( Circuit is Energized )
The test(s) ofRegulation – 612.2. - to 612.13.

Wording . Visual Inspection. The IETRegulation 612.3. gives a Checklist forthe Initial Visual Inspection – of the Installation

□ Connection of conductors .
□ Identification of conductors
□ Presence of fire barriers . ETC . This can only be done by . Visual Inspection .

 

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2392-10 . No - 2011

Justa Reminder . as an Inspector .

If any ( Tests ) fails to comply with the IET Regulation(s) .
Then all thepreceding Tests must be repeated after the ( Fault ) hasbeen rectified .
This is becausethe earlier Test results may have been (Influenced by the Fault ) - Regulation. 612.1.

 

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Just a Reminder. 2392-10

Earth Fault Loop Impedance . 612.9.

During the Test. The instrument does an . Ohms law calculation& displays the test results as a ( Résistance Reading )

 

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Just a Reminder. 2392-10

Testing forContinuity of Protective Conductors . & Main & Supplementary Equipotential Bonding.
-&-s .point of View . The object of the Testis to ensure that the circuit protective conductor– CPC. ( iscorrectly connected ) -&-s

Total Résistancewhich is ( Low Enough to permit the Overcurrent Protective Device ) 2391-10 / 2392-10 . operate within the disconnection timerequirements . IET Regulation – 411.4.6. “ Motor “ gM . “ Generalpurpose “ gG

a) “ General purpose “ ( gG ) &motor circuit application ( gM ) fuses to BS-88-2 fuse systems ( E ) bolted & (G ) clip in.

As an Inspector/ should anEarth Fault Occur .

 

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DomesticInstallation(s) -&-s 2011

Just a Reminder . – 2392-10

Testing should be carriedout from the day the Installation commences – Regulation . 610.1 :rant:

Regulation . 610.1

Every installationshall . during erection & on completion before being put into service . be ( Inspected & Tested ) to verify . so far as is reasonablypracticable . that the requirements of the regulations have been met .