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
-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
Designing )- part ( 2 )
:6: Ourcircuit is installed in a conduit which contains two-other-circuits Ifwe look at Table ( 4C1 ) we see that a ratingfactor ( Cg ) of ( 0.7) must be used because the conduit now contains Three-circuits . Using ( column 2 ) from ( 4D1A) we can see that a ( 2.5mm[SUP]2 [/SUP])cable has a Current-Carrying Capacity ( It ) of ( 24A )
( Iz ) will nowbe ( 24 x 0.7 = 16.8A )
Dueto being Enclosed with other circuits a (2.5mm[SUP]2 [/SUP]) cable can only carry( 18.9A ) This is assuming that all of yourcables are fully loaded & operating at ( 70°C)
Veryoften your cables are NOT fully loaded .provided that they are operating at NO more than( 30% ) of their grouping rating factor they can be discounted .
Designing )- part ( 1 )
:6: Letsus say a ( 2.5mm[SUP]2 [/SUP])cable is to be installed in an Area which has an Ambient Temperature of ( 40°C ) We can see Table ( 4B1) that a ( 70°C Thermoplastic Cable ) has tohave a rating factor of ( 0.87 – Ca ) Applied toit . This will give us the maximum current that the cable could carry withoutthe conductor temperature rising above ( 70°C . 24 x 0.87 = 20.88A ) Thisvalue is known as ( Iz )
( Iz ) is the current which a cable can carry Under itsInstallation Conditions .
Thisshows us that due to the cable starting at a Higher Temperatureit will require less current to take its Temperatureto ( 70°C )
Abbreviationsused in ( PV ) system .
:hurray: STC )- Standard Test Conditions . Voc)- Open Circuit Voltage . Vmp)- Maximum power point voltage . ( this is voltage under load ) Isc)- Short Circuit Current . Imp)- Maximum power point current ( this is current under load )
A Switch Disconnector must be provided to Isolate the ( PV ) array from the rest of the system . To avoid ElectricShock . ( PV ) array should be connected to the Switch Disconnector at the earliest Opportunity. The Switch Disconnector must be ( DOUBLE POLE ) & it is very important to ensurethat the Disconnector used to isolate the D.C.side of the system is rated for D.C. currents .
Whenswitching D.C. the circuit ( Creates a much bigger ARC & the switch has to be ABLE toCOPE with this ) Itis PERMISSIBLE to use a DOUBLE POLE circuit breaker to BS-EN 60898as a Disconnector .
Wherethe Installation consists of more than One String . Isolation must be providedfor each String . ( Which must be Readily Accessible)
Itis Usually a good Idea to provide Isolation as Close to the Array as Possible& also at the Inverter End .
D.C.)- The first Important thing to Rememberwith regard to ( PV ) panels is that they are ( ALLWAYSLIVE ).
Apprentices(- Solar Photovoltaic ( PV ) power supply system(s) Regulations - p/200
Thissection is for use with any “ Temporary Installations “ used for “ Exhibitions .Shows . Displays or Stands “
Thesecan be Indoors or Outdoors . it must be remembered that the Section ( Only Appliesto the Actual Temporary Installations ITSELF )
NOTthe Installation of the building from which the ( SUPPLY MAY be TAKEN ) ◄► Also it does NOT Apply to MOBILE UNITS
Theproblems surrounding this Type of Installation are it is Temporary . & becauseof this it is NOT Usually FIXED to be PERMANENT STRUCTURE .
Thiscould result in Mechanical Stress ◄► due to Movement of the STRUCTURE ( Plus general Public )
Dueto the Nature of this type of Installation . The wiring system must be well protectedfrom Mechanical Damage .
Wherethere is Access to the General Public . flexible cords must be very wellprotected against Mechanical Damage . Where the building which is being usedfor the Show or Exhibition Stand does NOT have a FIRE Alarm system . flame-retardantcables . conduit or trunking must be Used . & cables should NOT be joinedunless it is in ( An Accessory ) Thetrunking & conduit must have protection to a minimum of IP4X .
Switchgear& Control gear must be placed in an Enclosure . which can only be ( Openedby the Use of a Key or Tool ) This is unless they are Intended to be used by anOrdinary Person . This means of Isolation for the Show or Exhibition Stand mustbe readily Accessible to the User of the Stand .
Thissection of the Regulations also states that ( Where an Electric Motor may giverise to a Hazard it must be provided with an Effective Means of Isolation )
TN-C-Ssystems must NOT be USED & must be converted to a ( TT System : TN-S Systemmay also be Used )
TheSupply to the Temporary Structure must be Protected by a ( Time-delay or S-type RCD which has a Maximumrating of 300mA ) This is to provide Discrimination for Final Circuit(s) All other Circuit(s) apart from ( EmergencyLighting Circuit(s) must be Protected bya 30mA RCD. )
AllMetal parts which can be ( Accessed from within the Stand ) must be Bonded tothe ( MET ) within the Unit .
Aswith all other Electrical Installations .consideration must be given to Heat . This could be generated by the ElectricalEquipment & could cause Danger . Damage or Fire . to materials whichsurround it . or it could be an External Source of Heat which could causesimilar Damage to the Actual Electrical Installation .
SocketOutlets must be Installed to Reduce the ( Use of Trailing Leads ) Where socketoutlets are Installed in the Floor they must be protected from the ( Ingress ofWater ) & Mechanical Damage from Person or Equipment passing across them .
MK . ( The Spur has a Hole in the Fuse carrier forpadlock ) :bulb2:
WhenServicing or Repairing Appliances ( Fuse Carries ) Spur’s. Connection Units can be Padlocked for AdditionalSafety . (Fuse – Carriers can be Locked Open using a Padlock . list No – K2000 )
“ Spur(s) “ I now there saying put the Fuse in youPocket . Etc . by using a MK . Padlocked Off / You have Safe Isolation .
Regulation415.1.1. ( The Whys !! )
:19: Domestic Installation . We all use cables with ( Thermoplastic– PVC ) Insulation that are NOT Mechanicallyprotectedor ( Incorporate an Earthed metallic covering ) These cables would require RCDprotection .
Regulation415.1.2. Theuse of RCDs is notrecognised as a ( SOLE MEANS ) ofprotection & does not obviate the need to Apply one of the protectivemeasures specified in Sections 411 to 414
411: Protective Measure . ( ADS ) Automatic Disconnection of Supply. ProtectiveMeasure )- Where this protective measureis applied . Class II . equipment may also beUsed. ( 2392-10 / Bathrooms )
AsDesigners . 2392-10 . Five Installation methods areoffered for “ Cables “ at a Depth of Less than (50mm ) Regulation. 522.6.6.
i) The cable should incorporate an Earthedmetallic covering . ( Which acts as a Circuit Protective Conductor) CPC ii)The cable should be Enclosed in Earthed Conduit. iii)The cable should be Enclosed in Earthed Trunkingor Ducting . iv)The cable should be ( Mechanically protected ) againstpenetration by . Nails or Screws . ( -&-s . 2392-10 – Exams . plus / part – P ) v) The cable should be Installed in a SafeZone .
Weall Thing we know it all . But we don’t . ( The more you put IN – The moreyou get OUT) That’swhy . we have Guidance note 3 . O.S.G. / Part – P . 17[SUP]th[/SUP] Edition – BritishStandards . Etc. “ We are still all Learning “
Concealedcables requiring RCD protection ( ADS ) Rememberthat an Earth is the Most Important Arsenal youhave with an RCD . “ Under / Fault Protection “
Itis a Legal Requirement that the ( Statutory Document) Electricity at Work Regulations 1989 . is Adhered to & that ( Installation(s) are SAFEto USE .
&Do Not Cause any “ Danger “
The( Non-Statutory )documents .
17[SUP]TH[/SUP]Edition – BS-7671:2008 ( British Standards ) in a Court of Law .
Onsite–Guide … ( Guidanceonly ) O.S.G.– p/7 )- The scope generally follows that of BS-7671 . it includes material NOT included in BS-7671 . Provides“ Background to the Intentions of BS-7671 “ &gives other sources of information .
Wording(- This guide does Not Ensure Compliance with BS-7671:2008 . it is a SimpleGuide ( in Plain Words – it isreturning us back to the 17[SUP]TH[/SUP] Edition – BS-7671:2008 ( British Standards ) in a Court of Law .
GuidanceNote – 3 )- Inspection & Testing : Are Not Legalrequirements . But by following them we are deemed to be Complying withthe Electricity at Work Regulations 1989 .
Approved Document P . is called“ Electrical Safety “ &will be complied with if the Standard of Electrical Work meets the “Fundamental Requirements of Chapter 13 of ( BS-7671:2008)
Compliancewith PART – P Inthe Secretary of Statesview . The requirements of Part – P will be METby adherence to the “Fundamental Principle’s “ forachieving safety given in ( BS-7671:2008 )
Toachieve these requirements Electrical Installations in Dwellings Etc . ( MUSTBE )
• Designed & installed toafford appropriate protection against Mechanical & thermal damage . &so that they do not present Electric Shock & Fire hazards to people . • Suitably ( Inspected & Tested) ◄► to verify that they meet the relevant equipment & Installation Standards.
2392-10: ( In the Eyes of BS-7671:2008 – Competent Person)
:81:
IntegralTest Device : GN-3 . p/57 .
AnIntegral Test Device is incorporated in each RCD . This device enables thefunctioning of the ( Mechanical Part ) of the RCD . to be verified by pressing thebutton marked ( T ) or Test .
GN-3)- are telling YOU as a TESTER . ( Please Note) OPERATION – of the IntegralTest Device [ DoesNOT provide a Means of Checking ] ◄◄◄◄◄◄◄
► TheContinuity of the Earthing Conductor or theAssociated Circuit Protective Conductor(s) .or ► AnyEarth Electrode or other means of Earthing . or ►Anyother path of the Associated Installation Earthing. or ►TheSensitivity of the Device.
The RCD Test Button )- Will only OPERATEthe RCD if is ENERGISED.
AllInspected / Tested electrical equipment must carry a Label detailing . -Date of Inspection / Test . -Name of Inspector . -Date of Next Inspection / Test .
Ever thing has a Reason . ?? AllNew Equipment NOTyet requiring Inspection / Testing must carry a Label detailing .
-Date of First Proposed Inspection / Test . ( It will work it’sway into the System )
:rockon:
Arethere any Legal Requirements for Electrical Inspection . ( PIR )
BS-7671:2008– Red Cover . Requirements for Electrical Installations 17[SUP]th[/SUP]Edition . Require that “ Every new installation & Alteration or Extensionto an Existing Installation be Inspected &Tested before being put into SERVICE .
Electricityat Work Regulations 1989 – State .
i)As may be necessary to prevent danger . All system shall be maintained so as toprevent . so far as is reasonably practicable . such danger . Regulation 4 (2)) ii)System “ Means “ An electrical system in which allthe electrical equipment is . or may be . Electrically connected to a ( Common Source ) of electrical energy & includessuch source & such equipment . Regulation . 2 (1))c iii)Electrical equipment – includes ( Anything Used) intended to be used or ( Installed for Use )to generate . provide . transmit . transform . rectify . convert . conduct .distribute . control . store . measure or use Electrical Energy . Regulation 2. ( 1 ))
Regulation621.1 . Periodic Inspection & Testing . ( PIR )
Whererequired . periodic inspection & testing of ( EveryElectrical Installation ) shall be carried out in accordance withRegulation . 621.2. to 621.5. in order to ( Determine ) So far as isreasonably practicable . Whether the installation is in a ( Satisfactory Condition for ContinuedService )
Igot this on 2392-10 )- 621.2. ( PIR ) -&-s PeriodicInspection . comprising of a detailed Examination of the Installation ( Shall be carried out Without Dismantling or with PartialDismantling as Required )
2392-10. ( PIR ) Certification& Report . 634.1. p/163 Periodic Inspection Report .together with a Schedule of Inspections & a Schedule of Test Results .
1[SUP]st[/SUP]Amendment to the 17[SUP]th[/SUP] Edition . Red Cover. is still in use till then
:43: Itbecomes effective from January 2012 . Themost significant change is to the Certificates& Reports used for Inspection & Testing .
Fundamental Principles. Regulation . 131.2.1. Two-basic methods by which basic protection can be Accomplished .
• Preventing a current from passing through the body ofany person or livestock . • Limiting the current which can pass through a body toa Non-hazardous value .
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