***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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RCD - protection . Therequirements of Regulation 314.1. Division of Installation . need to be taken into account . whendesigning & installing the circuitprotective arrangements . 314.1. States thatevery installation shall be divided into circuits as necessary to .

i) avoid danger & minimize inconvenience in the event of afault .
ii)
iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit .
iv) Reduce the possibility of unwanted tripping of RCDs due toexcessive protective conductor ( PE ) currents not due to a Fault .

( protective conductor currents ( PE ) produced by equipment innormal operation )

Meansa Single RCD cannot be Used to protect the whole installation . ( As in theevent of a fault . The Supply will be lost to all circuits ( Inconvenience / Danger )

 

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RCDs are NOT designed to break the HighShort Circuit Currents . Etc . Must beused with an Overcurrent Device / MCB

RCBO / will . Overload - Short circuit . p/34

 

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Whereprotection is provided by an RCD . The effective operation of each RCD . shall be verified by a Test simulating anAppropriate fault condition independentof any Test facility incorporated in the device .

30mA– 0.03A .
10mA– 0.01A .

2392-10 (- On.Site.Guide :- does “NOT “ express any preference between Ring FinalCircuit or Radial Circuit(s) . Both circuit(s) are available to Designers / Electricians

Radial& Ring Final Circuit(s) & NO preferenceis assigned to any Circuit(s) Designers / Electricians are free to choose any of the Three StandardsCircuit(s) A1 – A2 – A3 .
Regulation 314.3.
Thisallows the designer to develop final circuit(s) coving different ( Floor areas ) & using different ratingsof protective devices

Useful Junk . “ ConductorSize “

Theconductor size for a fused spur is determined from the total current demand served by that spur .Which is limited to a maximum of 13A .

 

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Justa Thought .

TheLoad current in both legs of the Ring Final Circuit is shared as Equally as Possible. :icon_bs:

2392-10(- if we look around the Kitchen . Everything is grouped aroundthe Sink . W/machine . T/dryer /D/Washer . Etc .

Ifthe Sink does NOT happen to be more or less in thecentre of the Ring Final Circuit . One leg will carry MOREcurrent than the OTHER . ???

 

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SELV.

A voltage NOT exceeding 50V a.c. or 120V d.c. between conductors at any point of a circuitwhich is separated from circuits with higher voltages & from earth byinsulation at least equivalent to that for ( Class II ) or which has equivalent protective means .

SELV. p/34
( separated extra-low voltage ) An extra-low voltage system which iselectrically separated from earth 7 from other systems in such a way that asingle fault cannot give rise to the risk of electric shock .

Final Circuit . p/28
A circuit connected directly to current-using equipment . or to asocket-outlets or other outlet points for the connection of such equipment .

Fixed Equipment . p/28
Equipment designed to be fastened to a support or otherwisesecured in a specific location .

SupplyPoint .
A pointat which electrical energy is delivered .

Origin of a Installation / Circuit .p/31 .
The position at which electrical energy is delivered to an electricalinstallation .

Stationary Equipment . p/35 . -&-s
Electrical equipment which is either fixed or which has a massexceeding ( 18kg ) & is not providedwith a carrying handle .

( This value of thisMASS is GREATER than 18kg . in standards relating to Household Appliances ) Domestic. CoP /2392-10

RadialFinal Circuit .
A finalcircuit that serves two or more points including socket-outlets .

Ring Final Circuit . p/34 .
A Final Circuit arranged in the form of a ring & connected toa single point of supply .

Spur . p/34
A branch from a ring or radial final circuit .

Portable Equipment . ( see Mobile Equipment ) p/32 .
“ Mobile Equipment “ Portable Equipment – deprecated )) p/31 .
Electrical equipment which is moved while in operation or whichcan easily be moved from one place to another while connected to the supply .

 

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UsefulJunk

Reason . BS-1363. p/278 BS-1363

1gang & 2 gang 13A . switched socket –outlet .
The switch avoidsUnnecessary Wear on the socket as it can beswitched OFF rather than Unplugged .

13ARectangular Pin Plug . 1362 : 1973 – ( 1992 ) p/278
Commonlyreferred to as . “ Flat / pin . Square / pin . Fused Plug . Commonly used sizes . 3A . 5A . 13A . CoP .

BS-1363. Fused connection unit with double pole switch & front flex outlet ‘
Reason . Used to supply permanentlyconnected appliances & also provides a meansof control . By removing the Fuse we have Isolation . Lock / OFF . M/K

FusedConnection Unit . Unswitched with Neon . should be used it is requiredthat the appliance should NOT be accidentally SwitchedOFF . Alarm/circuits & Freezers’ .

Socketoutlets provide an easy & convenient method by which portable appliancesmay be connected to the electrical supply . BS-1363

TheBritish . Ring Final Circuit system . & BS-1363 .

13Aplugs . socket-outlet(s) . connection unit(s) & adaptors plug &socket-outlet system were Introduced into the UK. In 1947 .

PDF] THE ORIGIN OFTHE BS 1363 PLUG AND SOCKET OUTLET ... Useful Junk . Good Reading.

 

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O.S.G. . Back of the Book .we have Electrical Symbols . to Use .

 

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2392-10 (- It is recommendedthat twin socket-outlet(s) be installed rather than single types as the initialcost is low in relation to having them replaced at a later date . .
2392-10 (- The following Guidelines as to recommended numberof Socket-Outlet(s) per location in a Typical Domestic Dwelling . O.S.G. P/178 . Table H7

 

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Note : Other methods are Not precluded .

2392-10(- Ring Final Circuit .

Thecable used must be capable of carrying (0.67 times ) the rated current of the protective Device . On the circuit .
Example. This is ( 2.5mm[SUP]2[/SUP]) Which has a current carrying capacityof ( 32A) When installed in Normal Domestic Installations.

Usingthe Factor of ( 0.67times ) we can calculate the maximumload on the circuit .

Calculation. Maximum Load on Cables .. 23 ÷ 0.67 = 34.33 Amps .

Alternatively.

Givena protective device current rating . find the minimum . Current Carrying Capacity of the cable required .

Calculation. Minimum . C.C.C. of Cable . 32 x 0.67= 21.44Amps

MCBwith a rating of ( 32A ) is fitted to a Ring Final Circuit(s) in DomesticInstallation(s) This provides protectionfor ( 2.5mm[SUP]2[/SUP] ) cables

Ring Final Circuit arrangements Regulation . 433.1.103 .
(iv) taking account of the totalfloor area being served . ( Historically . a limit of 100m[SUP]2[/SUP] has been adopted ) p/425 :13:

 

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Note : Other methods are Not precluded .

2392-10(- Ring Final Circuit .

Thecable used must be capable of carrying (0.67 times ) the rated current of the protective Device . On the circuit .
Example. This is ( 2.5mm[SUP]2[/SUP]) Which has a current carrying capacityof ( 23A) When installed in Normal Domestic Installations.

Mistakein calculations . ( 23A ) ◄◄

 

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Cooker Example .Calculation .

Note :Other methods are Not precluded . :banghead:

To ascertain the total loading of an electric cooker,the loading of the individual elements, motors, lights etc. must be added. Forexample, the total load of a typical electric cooker is comprised of thefollowing loads:

Boiling Ring RH Rear . 2000 W
Boiling Ring RH Front . 2000 W
Boiling Ring LH Rear . 2000 W
Boiling Ring LH Front . 2000 W
Grill Element . 1800W
Oven Element LH . 1200 W
Oven Element RH . 1200 W
Hot Cupboard Element . 500 W
Oven Lamp . 40 W

Total Load 12,740 W

The full-load current of this cooker may now becalculated:

FullLoad Current = Load in Watts
…………………………Full Load Current

I = 12740
…. 230

I = 55Amps approximately

However,diversity is allowed and should be assessed as follows:

The first 10 Amps of thetotal rated current of the cooker, plus 30% of the remainder of the total ratedcurrent.

First 10A = 10 A

30% 0f Remainder = (55 – 10 ) x 30% = 13.5 A

Total = 10 +13.5 = 23.5 A

 

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Instantaneous ElectricShower(s) . O.S.G.- Table– A2 .

AnElectric Shower heats only the required amountof water ( Instantaneously) Wording .

 

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Wiring Regulation Restrictions.

Domestic Installation(s) . The total ( REN ) –Ring equivalent number . value of all Telephone equipment connected on a Line must NotExceed ( 4 )

 

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2392-10: MK . Switch Disconnectors 100A . BS-EN 60947-3.

17[SUP]th[/SUP] Edition 2011 . Regulations . 537.2.2.1. & 537.2.2.2. p/151.

Devices for Isolation . 537.2.2.1.
A device for ( Isolation ) shall ( Isolate ) all live supply conductor(s) from the circuit concerned .subject to the provisions of Regulation 537.1.2.

A device suitable for isolation shall be selected according to the requirements which are basedon the overvoltage category applicable at the point of Installation . Etc .

Equipment used for ( Isolation ) shall comply with Regulation(s) 537.2.2.1. & 537.2.2.2. to ( 6 ) ◄◄ :13:

537.2.2.2. The position ofthe contacts or other means of ( Isolation ) shall be either externally visible or clearly& reliably indicated . An indication of the isolated position shall occuronly when the specified ( Isolation ) has been obtained ( in EACH POLE )

 

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2392-10: MK . Miniature Circuit Breaker(s) MCBs . BS-EN 60898 : 2003 .

17[SUP]th[/SUP] Edition 2011 . Regulations . 537.2.2.1. & 537.2.2.2. p/151.

When the Green Indicator is Visible . ( Then a contact gap of 4mm has been ACHIEVED ) “ Supply is Cut-OFF “

BS-EN 60898 : requires the tripping to occur within ( 100milliseconds ) Fault Current of up to6000A .