***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 “ Testing “
Meansfor Disconnecting the Earthing Conductor .

542.4.2. – requires means fordisconnection of the Earthing Conductor . to be provided at or near the ( MET ) of aninstallation to “ Facilitate measurement“ of the Résistance of the Earthing arrangements .

Meansof Earthing “ . Earthing Conductor → [ Bolted Link] → Connections : Circuit protective conductor : Mainprotective bonding conductors :
Functionalearthing conductors – if required : & lighting protection system bonding conductors - if Any .

 

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Inorder to decide whether or not a specific “ Item “ is an Extraneous-conductive-part :

Q). is the item liable to introduce a potential . generally . EarthPotential .
Isthe item liable to introduce a “potential to a person “ or Livestock . who may be in contact with another potential .

Tointroduce a “ potential “ to such a person . the item must not only be apotential . but must be able to “ Introduce the potential “ introduction of the potential requires [ Two-things ]

- Thefirst is that the item [ or a Conducting item in electrical contact with it ] must be accessible to be [ Touched by a part of such a person’s body ]

- Thesecond is that any [ Electrical résistance ] through which the item is connectedto the [ Source ] of its potential – such as the résistanceconnecting an item with Earth potential . must not be so great as to preventthe potential being introduced to a person – due to voltage drop in the résistance.

Isthe item part of the Installation .

Onlyan item which does not form part of the electrical installation concerned may be an [ Extraneous-conductive-part ] however . items serving a purely non-electrical purpose within theinstallation should not be ruled out . moreover . items forming part of anotherinstallation are not precluded .

 

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Thirdpart “ & NOT forming part of the ElectricalInstallation .

Thispart of the definition limits [ Extraneous-conductive-parts ] tobeing items which Do Not From Part . of the electrical installation in question .

Therefore. items which may be [ Extraneous-conductive-parts include ] the following . which are referred to inRegulation – 411.3.1.2. with regard to “ Main Protective bondingconductor “ provided such items arealso covered by other parts of the definition referred .

Waterinstallation pipes .
Gasinstallation pipes .. Etc .

Anyother non-electrical items which fallwithin the definition may be Extraneous-conductive-parts .
Althoughthe definition precludes items forming part of the electrical installation frombeing Extraneous-conductive-parts .items . serving a purely non-electrical purpose within an electricalinstallation should NOT be ruled OUT . such items may include .

A Metalsupport system or carrier for cables having non-metallicsheaths which is not required to be earthed .

Moreover– items forming part of another electrical installation – that is . aninstallation supplied from a different origin or having a separate earthing arrangements .
Are not precluded from being . Extraneous-conductive-parts . such items mayinclude . for Example . a metal conduit or the metal sheath or armouring of acable entering the premises from another building .

 

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SpecialInstallations or Locations : 2011:

Theuse of SELV.

701: locations containing a bath or Shower .

701.414. Protection against electric shock .
701.512.3. Erection of switchgear . control gear &accessories .
701.55. Current – using equipment .
701.753. Electric floor heating systems .

702. Swimming pools . Application ofprotective measures against electric shock .

702.414. Protection against electric shock .
702.522.24. Junction boxes .
702.53. Switchgear & controlgear .
702.55. Other equipment .

703. Hot air saunas . Protection against electricshock .
704. Construction & demolition siteinstallations . 704.410.3. - 704.414. Protection against electric shock .
705. Agricultural & horticultural premises . 705.414. Protection against electricshock .
706. Conducting locations . 706.410.3.10. Protection against electric shock .

711. Exhibitions . shows & stands . 711.414.4.5. . Protection againstelectric shock .
712. Solar photovoltaic ( PV ) power supply systems . 712.414. Protection against electricshock .

 

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Emergency Lighting :

Checklist .

For Emergency Lighting .
Non-Maintained . -&-s . The light only operates whenthe [ Normal main supply fails ] Emergency Lighting only .
( Permanent L ./ N )

Maintained . -&-s. The lighting operates normally & continues to operate when the normalmains supply fails [ Mains lighting& Emergency lighting ]
( Switched L : Permanent L . / N )

Final Exit Sign’s:
To provide illumination of escape routes .

Junctions : Install within 2 metres of escape route junctions .

Corridors : Install within 2 metres . horizontal distance of achange of direction in an escape route .

Stairways : Installwithin 2 metres . horizontal distance of achange in floor level or stairs [ each tread to receive direct light ]

Final Exit : Install externally within 2 metres horizontal distance of any final exits . Note : that sufficient light will be needed tomuster a roll call .

Alarm Exit : Firealarms . first aid points & fire fighting equipment . installed within 2metres horizontal distance .

Escalators : Shouldnot be used as an escape route . butrequires the same illumination to protect Uses on it when the supply fails .

Toilets : Install in all toilets exceeding [ 8m[SUP]2[/SUP] ] area or where natural light is not present .

Lifts : Toprovide emergency illumination in alllifts .

Control Rooms : Motorgenerator . control & plant rooms for essential & safety services .

Open Areas : Open rooms either with a particular hazard . an escape route passing through or largerthan [ 60m[SUP]2[/SUP] ]

Hazardous Areas : Areas of high risk should beilluminated to [ 10% ] of normal lighting or [ 15 lux ] whichever is greater .

Lighting Requirements .
When luminaires have been sited to cover the locations[ Above ] ▲ additional luminaires may be required toensure minimum lighting levels areachieved .
Manufactures provide spacing tables for this purpose . Spacingtables advise how far to locate the first luminaire . then how far . apart otherluminaires should be located for a given mounting height . Installation to the spacing’s will ensure thelighting levels will be achieved .

Escape route corridors : 1 lux minimum on the centre line of the escaperoute .
Open Areas : 0.5lux minimum on the centre core to within 0.5m of the walls .

Exit signs : Signs should apply to the European SignsDirective & be either . back illuminated or have an Emergency luminairewithin 2m of horizontal height . Signs should be of thesame formal throughout the building .

 

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Emergency Lighting :
Form . EmergencyLighting design guide . 4 Edition 2008 .

Workplace directive – 89/654 .
Is 5 or more people areemployed there must be a writtenrecord of the assessments findings & the action taken . -&-s Exams

Maintained Emergency Luminaire :
A Luminaire containing one or more lamps all of whichoperate from the normal supply . or fromthe emergency supply at all material times .

Non - Maintained Emergency Luminaire :
A Luminaire containing one or more lamps . whichoperate from the emergency supply ONLY upon failure of the normal mains supply.

Normal Lighting :
All permanently installed [ Artificial ] lighting operating from the normal electricalsupply that in the absence of adequate [ daylight ] is intended for use duringthe whole time that the premises are Occupied .

Rated duration :
The manufactures declared duration . specifying the time for which the emergency lightingwill provide the rated lumen output after mains failure . this may be for anyreasonable period but in normally [ one or three hours . ] -&-s Exams

Rated Load : Themaximum load that may be connected to the system & will be supplied for theduration .

Re – charge period :
The time necessary for the [ Batteries ] to regain sufficient capacity to achieve their ratedduration .

Self – contained emergency luminaire or Single point luminaire :
A luminaire or sign . providing maintained or .Non-maintained emergency lighting in which all the elements such as the battery. lamp & the control unit are contained within the housing or within one metre of the housing .

Slave or Centrally supplied luminaire :
An emergency luminaire without its own batteriesdesigned to work with a central battery system .

 

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Usefuljunk :

EdisonBase – Light Bulb’s . 612.6. (ii) [ Indicates ] 230V / E27 . male screw base.
E27 . the number “ 27 “ simply signifiesthe number of millimetres in diameter of the base itself . [ 27mm ]

 

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Zones : Previous 16[SUP]th[/SUP] Edition .
Identifiedzones within the bathroom to [ Illustrate] what typeof electrics in the Bathroom . can be usedor installed .

Zones: 17[SUP]th[/SUP]Edition . “ Updated “

Takeinto account . Windows : doors : walls ceiling & partitions . [2392-10 - You are . Assessing the level of Risk in each Zone ]

Circuits in a Bath or Shower room . both power & lightingmust be Additionally protected by an RCD . 30mA - 701.411.3.3.: 314.1 (iv) : 531.2.4. Unwanted tripping .

17[SUP]th[/SUP]Edition – reinforces this .
Bath or Shower islocated in a building with Protective equipotential bonding in place . 411.3.1.2.

Mainprotective bonding conductor(s) . (i) Water installation pipes . [ Extraneous – conductive– parts ]

p/27 . Equipotential bonding. Electrical connection maintaining various . Exposed-conductive-parts & Extraneous-conductive-parts

• 2392-10 : Exams

Inyour own words . State . the meaning of a circuit overload & short-circuit protection . What will provide this type of protection !! :icon_bs:
p/35 . RCBO .

Wording .
Residualcurrent operated switching device . designed to perform the functions ofprotection against [ Overload & / or Short-circuit]

 

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Bathroomequipment . selection & erection requirements .

Equipmentin “ Zone 1& 2 “ shall be at least IPX4 . Regulation . 701.512.2.( ii )
Equipmentin “ Zone 0 “ shall be at least IPX7 . Regulation . 701.512.2.( i )
Equipment exposed to cleaning jets to be at least IPX5. . Regulation . 701.512.2.

Zone 0 “ only 12V currentusing equipment . complying with a relevant standard is allowed . 701.55 .
(ii) - Fixed & permanently connected .
(iii) - SELV . safety source located outside of Zone .

in Zone 1 “ only :

Water/pumps. electrical shower(s) . Shower/pumps . ventilation equipment . towel rails . waterheaters . luminaires & 25V - SELV equipment is allowed . 701.55.
Fixed& permanently connected . SELV safety . source located outside of Zone . 0. 1. & 2 .

in Zone 2 “ only :

12V. SELV switches & shaver supply .socket-outlets to BS-EN-61558-2-5 . are the onlyallowed switchgear or accessories . 701.512.3.
SELV. safety source located outside of Zone .

2392-10: IP rating. dependent upon it’s location in the room . :banghead:

 

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GN-3– 2012 :

Classification of danger & non-compliances ( foruse during periodic inspection & testing )

Classification of danger or non-compliances [Description ]
C1: Danger present . Risk of injury . immediateremedial action required .

Notes &guidance :
To be cited insituations which cannot be left . it is suggested that these are rectified orpossibly . isolation may be recommended or necessary . examples : includeaccessible bare live parts , badly damaged equipment with risk of access tolive parts . incorrect polarity . arcing found in switchgear .

C2: potentially dangerous – urgent remedial action required .
To be cited insituations that . whilst urgent , do not require immediate remedial action . .examples : include a non-earthed installation . ( this requires a further faultto manifest injury ) fundamentally undersized cables . earth loop faultimpedance values greater than ( BS-7671) requirements . a “ borrowed “ neutral . equipment with inappropriatelyselected IP . ( this may be . C1 if severe ) insulationreadings under ( 1MΩ )connections not terminated within appropriate enclosures .

C3: Improvements required .
To be cited where .C1 or C2 . do not apply . examples : include the absenceof most warning notices . absence of therequired diagrams & charts . no or incorrect marking of conductors atterminations , absence of an ( RCD ) specified for additional protection . ( Where the circuit otherwise tests as normal )

 

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GN-3– 2012 : ( IR )

InsulationRésistance of a . Three-phase 4– core power cable .
The cable is tested.

Insulation Résistancetest on . 4-core power cable :

Test 1 : L1 / L2 .
Test 2 : L1 / L3 .
Test 3 : L2 / L3 .

Test 4 : L1 + L2 +L3 – ( connected together ) to Neutral
The lowest value ofthese tests . is recorded as “ between Live conductors “

Test 5 : L1 + L2 + (connected together ) to Earth .
The lowest value ofthese tests . is recorded as “ between Live conductors & Earth “

Note :it is essential for . Tests 5 & 6 that the cable earth is connected to the installation earthing terminal.

( IR ) readings obtained should be not less than theminimum values referred to table.BS-7671:2011 . Table61 .

 

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GN-3– 2012 : ( IR )

612.4.1. : SELV tests .
Test type .

Basic insulation .between Line conductors & all other circuits including other . SELV &PELV . & low voltage circuits . ( 250V – d.c.) Minimum – 0.5MΩ .

Line / Earth : Between al SELV live parts & Earth .

Note: in situations where the SELV conductorsare separated by just ( insulation ) such as within a ( multicorecable ) with low voltage circuits . then the test voltage shall be increasedto ( 500V d.c.) & the (IR ) shall be not less than . ( 1MΩ )

612.4.2. : PELV tests .
Test type .

Basic insulation .between Line conductors & all other circuits including other . SELV &PELV . & low voltage circuits . ( 250V – d.c.) Minimum – 0.5MΩ .

Note: in situations where the PELV conductorsare separated by just ( insulation ) such as within a ( multicorecable ) with low voltage circuits . then the test voltage shall be increasedto ( 500V d.c. ) & the ( IR ) shall be not less than . ( 1MΩ )

 

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Teatmethod 2 : for circuits .

Instrument : use a low-résistance ohmmeter for test . ◄► Exams – 2391-10 .

One lead of thetest instrument is connected to the earth terminal at the distribution board . via a length of test cable or ( Wandering Lead ) the other test lead is used to make contactwith the protective conductor at . various points on the circuit under test .e.g. luminaires. switches . spursoutlets . etc . the résistance ofthe ( Wandering Lead ) & the test leads areeither auto-nulled prior to making the test ormeasured & subtracted from measured readings .

This test measuresthe continuity résistance of the circuit protective conductors ( R[SUP]2[/SUP] ) which should be ( Recorded on the Scheduleof Test Results )

Note: Parallel earth paths & effects on thereadings ) ◄► Exams – 2391-10 .

Exams – 2391-10 . Wording : Mainswitch [ OFF ] all fuses removed . circuit/ breakers [ OFF ]

Results : for test method 2 :

The results shouldfirst & foremost indicate ( No Open Circuit ) in the protective conductors . for insulatedwiring systems installed in conditions where accessory boxes & similar are not connected tofabric or other elements that mat be earthed . then the measurement will equate to the protective conductor résistance ( R[SUP]2[/SUP] ) this test can detect poor continuity atjunctions & connections since . for a New installation with new accessories. the contribution of résistance of healthy connections is negligible & canbe ignored . thus by employing the résistance data for copper conductors .

Expected values forhealthy cable & connections can be checked .

Example . Radialcircuit . of length about . 55m with a 2.5mm[SUP]2[/SUP] copper protectiveconductor should have an ( R[SUP]2[/SUP] ) résistance .
Length of circuitis 55m .
Résistance of cableis . 7.41 mΩ/m - at 20°C .
Theoretical minimumd.c. résistance- ( 55 x 7.41 ) / 1000 = 0.41 Ω

When verifying this circuitthe . Inspector . should be looking for a reading of that order . say . 0.4 to 05Ω . if the circuit had several outlets . thusmeasuring that the protective conductor was broken & connected in screwterminals at each accessory . then a slightly higher value may be measured . asthere would be some résistance at the termin

 

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( IR ) Testing . 2392-10 . / 2394 .Exams . Q/As .

For circuits containing [two-way switching or two-way & intermediate switching ] the switches must be [ operated one at a time] at a time & the circuits subjectedto additional ( IR) test in these configurations .

 

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Testing . .

Earth fault loop impedance: Verification . 612.9.

Where limitation ofearth fault loop impedance is part of a protective measure .then it is fundamental that the [ InitialVerification ] process includesverification of earth fault loop impedances .

The earth faultcurrent loop comprises the followingelements . starting at the point of fault on the line – earth loop .
Circuit protective conductor.
Main earthingterminal & earthing conductor .
TN-system’s the metallic return path or . in the case of . TT & IT . systems .the earth return path .
Path through theearthed neutral point of the transformer .
Source line windings . &
Line conductor fromthe source to the point of fault .

612.8. - 612.9. :
There are [ Two-methods ] used for verifying total . earth faultloop impedance for a circuit :

- Measurement oftotal earth fault loop impedance ( Zs )using an instrument .
- Measurement of ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) during continuity testing of a circuit . & addition to the measured earth faultloop impedance external to that circuit ( Ze )

Exams . Instrument : use an earthfault loop impedance tester . for this test .