***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 )

 

[shill]

Thank you for all the easy to read info... you made it easy to follow, thank you

 

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Calculationof Earth Fault Loop Impedance :speechless:

The most commonly used measure . Automatic Disconnectionof supply either the Overcurrent protective devices - Which also provideprotection against “ Overload &Short circuit Currents for the circuit Concerned .

ResidualCurrent Devices . RCDs or combined devices RCBOs . Whichever type of device ischosen .

TheEarth Loop Impedance that has to be considered is that which comprises the Impedance of the Source .
TheLine conductor up to the Fault plus the Protective Conductor from the fault to the Source .

Whys& How’s .

Note:- That when an RCD or RCBO is used to provide Automatic Disconnection of thesupply in a ( TN- system ) the calculation of ( Zs ) is normally “ Unnecessary “ provided that “ Continuity“ of the EarthLoop has been Established . ◄◄

Anotherreason for calculating the Earth Loop Impedance is to check that the “ Circuit Protective conductors are adequatelyprotected thermally . & That they comply with the “ Adiabatic Equation givenin Regulation . 543.1.3. – Subject ofChapter 4 .

 

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BS-7671:2008– Bottom of . Table 41.3 – NOTE.

ContainsNO requirements in relation to the Conductor Temperatureat which the Earth Loop Impedance iscalculated .
Note :- The notes to the tables of Maximum Earth FaultLoop Impedance . – Table 41.2. – to 41.4. . States . that the Tabulated Valuesshould NOT be exceeded when the conductors’ are at their Normal Operating Temperature.

ifthe conductors’ are at a different temperature when tested . The reading should be Adjusted Accordingly – Appendix 14.

 

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Current – Carrying Capacity . ofa Conductor . :speechless:

TheMaximum Current which can be carried by aconductor under Specified Conditions without itssteady state temperature exceeding a specified value.

 

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Apprentices.

Namethree types of “ Diagram “used in the Electrical Industry . & explain – ThereUse . :icon_bs:

Anythree from Wiring diagram . Circuit diagram . Block diagram . Layout drawing .Installation drawing . Schematic drawing . Site plan .

A wiringdiagram provides a pictorial representation of an Electrical Circuit . showing arepresentation of the components .
A blockdiagram typically shows the flow of aprocess . each function being represented by a block .
A schematicdiagram uses symbols to show the arrangement of a system clearly .
Whereasa layout diagram shows the physical arrangement of the wires & components .

 

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:45:2392-10: ▼
Q) The main switch in a “ Single – Phase “ domestic Installation interrupt’s how many “ Live Conductors “

-&-s: BS-7671 – Regulation 537.1.4. The main switch should interrupt both LiveConductors on a Single/Phase Supply .

A MainSwitch intended for operation by “ Ordinary Person“ of a Household or similar Installation . shall Interruptboth Live Conductors of a Single-phase supply .

Q) How many poles would the main switch on aThree-phase & Neutral – TN-S supply have .

Threepoles - BS-7671 – Regulation 537.1.2. The Neutral neednot be Switched . ( TN-S or TN-C-S )

2392-10: ▼

Q) State: Two precautions that must be takenbefore carrying out Insulation Résistance Testing .

i) Remove sensitive equipment – Dimmers .Programmers . P.I.R.
ii) Remove equipment that “ GIVES “ falsereadings – Lamps . Neon’s . Motors .
iii)Check it is Safe to continue with the Test . When applying – 250 / 500V .

-&-s: Make sureNo-one else is in contact with any part of the Circuit .

 

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2392-10: ▼

Inrelation to Electrical Installations . :waving:

Whatis meant by Maximum Demand :- This is an Assessment of the current demand of an Installation.
Whatis meant by Discrimination :- The co-ordination ofprotective device(s) so that the device nearest to the load . being of a lowerrating . operates before the device futher up the line . Thereby minimisingloss of supply when a fault occurs .
Whatis meant by Diversity :- An allowance given when calculating maximum demand . due tothe fact that not all of the appliances . will be Used at the Same Time .

 

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2392-10:

FunctionalTesting ?? :waving:

Testing of Switches . Disconnections. Controls . RCDs . to check that they FunctionCorrectly .

 

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2392-10:

ApprovedVoltage Tester . To - GN-38 . :waving:
State:- Three of the requirements for Test Leads .
i) Retractable tips . or not more than ( 4mm) prefer 2mm . Fingers guards . Robustleads . coloured or identified . long enough for the purpose . Fused probes .

State:- the method of Ensuring it is working Effectively .
ii) By the use of an Approved Proving Unit .Testing the voltage tester . Before & After testing the equipment . or Circuit .

 

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Definitions’/ p/23 . EarthingConductor

A protectiveconductor connecting the main Earthing Terminal of an Installation to an EarthElectrode or to other means of Earthing .

Connectsthe main Earthing Terminal to the source of Earth . either an Electrode ( TT ) or means ( TN-S or TN-C-S ) :95:

 

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2392-10: ( T )

Howis Discrimination achieved when Using RCDs . :- Byusing Time-delayed RCDs . :79:

 

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Insight to the working of 17[SUP]TH[/SUP] Edition . “ Examples “

BS-7671:2008. Section 708 – Caravan & Camping Parks .

Thisis accommodated by the provision of suitably placed socket outlets . supplied via distribution circuits .

External Influences .
Equipmentshould have at least the following protection codes .
Impactrésistance . 708.512.2.
IPX4– for the presence of Splashes – ( AD4 ) in accordance with BS-EN 60529.
IP3X– for presence of small objects - ( AE2 ) in accordance with BS-EN 60529.
IK08- for presence of high severity mechanical stress ( AG3) in accordance with BS-EN 62262 .
(The ( IK ) codes are for Impact & ( 0.8 ) is an Impact of ( 5-Joules ) ImpactRésistance .
( Environment – p/324 . AG3 – High Severity . Reinforced Protection . IK08 )

British Standards to whichReference is made in the Regulations . Appendix1 – “ Normative “ p/228 – ( Requirement )

BS-EN 62262:1992 . – 2004 . Specification for degrees’ ofprotection provided by enclosures ( IP Code )
527.2.6.– (i) the system satisfies the test of BS-EN 62262 for ( IP33 )
527.2.6.– (ii) any termination of the system in one of the compartments , separated bythe building construction being penetrated . satisfies the test of BS-EN 62262for ( IP33 )
702.512.2.: External Influences . Electrical equipment shall have at least the following degree of protection according to BS-EN 62262. ( IP ???? )
708.512.2.- (i) & (ii)
708.553.1.8.each socket-outlet & its enclosure forming part of a caravan pitch electricalsupply equipment shall comply with ( BS-EN 60309-2 ) & meet the degree of protection of at least( IP44 ) accordance with BS-EN 60529 .
A721.55.6.- p/218. Terminal blocks .
A721.55.10.- p/218. External lights .

Note : Section 721 : tells us . p/209 – Wording . Yeah :96:
Inorder not to ►► MIX ◄◄ Regulationson different Subjects such as those for Electrical Installation ofcaravan parks with those for Electrical InstallationINSIDE caravans .
Section– 708 . concerns Electrical Installations ( IN ) caravanparks . camping parks & similar locations & . Outside.
Section– 721 . concerns Electrical Installations ( IN ) caravans& motor caravans . Inside

WiringSystems .
Thedistribution circuits are erected either Underground or Overhead .
708.521.1.1.- i) Underground cable ( Preferred )should be suitably protected against Mechanical damage . tent pegs . steelspikes . & at a depth of NO less than ( 0.6m )
708.521.1.2.- ii) Overhead . if overhead . Then ( 6m) above ground where there is Vehicle movement ( 3.5m ) elsewhere .

Switchgear& Socket outlets .
708.530.3.- Supply equipment should be adjacent to . or within ( 20m ) of the pitch .
708.553.1.8.– Socket-outlets should be :- BS-EN 60309-2– ( IP44 )
708.553.1.9.- at between ( 0.5m to 1.5m ) aboveground .
708.553.1.10.- rated not less than ( 16A )
708.553.1.13.– each socket-outlet shall be protected individual by an ( 30mA ) RCD protection. ( The device shall disconnect all LIVE CONDUCTORS including the NEUTRAL.
708.553.1.14.– if the supply is ( TN-C-S ) the protective conductor of each socket-outletneeds to be connected to an ( Earth Rod ) Regulation – 411.5. TT System .

 

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AdditionalProtection . :hurray:

703.411.3.3.Sauna heater .
Allcircuits in the location should have “ Additional Protection “ against shock by30mA RCD .
Except Sauna heater circuits unless Recommended by the Manufacturer . :svengo:

 

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External :- Earth Fault Impedance . ( Ze )

The Importance of this Test . To establish that a good Earthexists at the installation in order for the Remainingtests to go ahead . :svengo:

 

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Additions & Alterations to anInstallation . :waving:

General :

Many existing electrical installations require one or moreAdditions or Alterations during their lifetime . An Addition or Alteration maybe minor ( such as the Addition of a point to a final circuit . or therepositioning of a point ) or major ( such as the Addition of a new finalcircuits . distribution circuits . distribution boards & an upgrade to thesupply .

Where an Addition or Alteration ( which temporary or permanent) is to be made to an installation . the relevant requirements of BS-7671 .have to be met such that both the Addition or Alteration is Safe . & thesafety of the Existing Installation is not Impaired.

In order to be meet the requirements of BS-7671 . Followingmust be undertaken .

• Assessment ofthe existing installation to establish that the parts upon which the Additionor Alteration will rely for safety are both present & suitable for thealtered circumstances . & will continue to be so . & that the supply issuitable .
• Upgrading of parts of the existing installation . where foundnecessary to safely accommodate the Addition or Alteration . as a result of theabove Assessment .
The electricity distributor will need to upgrade thesupply . if Necessary .
• Design & construction of the Addition or Alteration inaccordance with the requirements of BS-7671 .
(T) • Inspection &Testing of any upgrading of the existing installation . & of the Addition or Alteration . as requiredby chapter 63 of BS-7671:2008
• Certification of any upgrading of the existing installation . & of the Addition or Alteration . as requiredby chapter 63 of BS-7671:2008

Assessment of an Existing Installation .
Regulation ( 131.8.) requires an Assessmentto be made of the relevant parts of an existing installation which is tobe Added to or Altered of the Supply .

Regulation ( 131.8.) No Addition orAlteration . temporaryor permanent shall be made to an existing installation . unless it has been ascertained thatthe rating & the condition of any existing equipment . including that ofthe distributor . will be Adequate for the Altered circumstances . furthermore . The Earthing & Bonding arrangements . if necessary for theprotective measured applied for the safety of the Addition or Alteration . shall beAdequate .