***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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Workingmy way around the 17[SUP]th[/SUP] Edition – Selection & Erection / Part 5

Making you aware of “ Accessibility“ :aureola:

Everyconnection shall be Accessible for Inspection
- Exceptions include . ◄◄ :50:

- Designedto be Buried .
- Compound resin Joint .
- Connectionto Floor / Ceilingheating Elements .
-Soldered . Welded . Brazed . Compressed Joints . or appropriate compressiontool .

 

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Workingmy way around the 17[SUP]th[/SUP] Edition – Selection & Erection / Part 5

Making you aware of “ Installation CircuitArrangements “ Part – 3 & 5 :dupe:

Thenumber of circuits & outlets per distribution board will be .

520.3. FundamentalPrinciples . :freak:

i)Cables & Conductors .
ii)Connections . Terminations & Joints.
iii)Supports & Suspensions .
iv)Enclosures & Protection against External Influences .

OvercurrentProtection – Chapter 43 .
Isolation& Switching – Section 527 .
Currentcarrying capacity of the conductors – Section 523 .
ExternalInfluences – Chapter 52 . 522 . App 5

CableSelection Overview .

Therequirements are :-
Thecable supplying the Load should be able to carrythe current to the Load safety . after takinginto account Diversity . without the cable Overheating– 523 . App 4

Protective Devices should beable to provide protection for the cable from Excess Current – 432. 433 .

TheLength of the cable is Limited to Ensureadequate voltage supplies the Load . 525.

MaximumLoop Impedance of a circuit is Low enough to ensure disconnection within timesspecified by Table 41.1.

( 0.4 - TN ) & (0.2 sec - TT ) for all circuits 32A ( FinalCircuits Not Exceeding 32A ) P/46
(5 sec disconnection time ) for Sub –main distribution circuits . Etc .

 

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2392-10: Protection against Shock .

Two Important Measurements mustbe taken to prevent this hazard . :50:

i) Impedance of acircuit conductors is kept to a minimum . The Earth Fault LoopImpedance under Fault Conditions .
ii) Overcurrent device protecting the circuit isselected to rapidly disconnect an Earth Fault .

 

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Room Thermostat should belocated in the part of the house where people spend the most time . it shouldbe ( 1.5m. ) above floor level .
( 0.5m away from an outside wall ) :aureola:

Relevanttests of Regulation – 612.2. to 612.13 .Example Continuity of Protective conductors & Earth Fault Loop Impedance .Applicable to parts of the system(s) such as room & cylinder Thermostats .motorized valves & programmers .

( YES ) Automatic Disconnection of Supply ( ADS ) is acommonly – used protective measures against Electric Shock in such systems .The Continuity of the protective conductorsto each point should be confirmed . This value of ( R2 ) or ( R1 + R2 ) may be used to estimate the Maximum EarthFault Loop Impedance of each control circuit for Verification Purposes . Insulation Résistancetests should also be carried out . precautions having been taken to avoiddamage . to any Electronic Components . The test results should be recorded on a Schedule oftest results .

Regulation. 411.3.1.1. – 411.3.2. – 612.9.

 

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DoesBoiler pipework need to have Main Protective Bonding Conductor for ElectricalSafety Reasons . :dupe:

Thereis “ NO SPECIFIC “ requirements for Boiler pipework to be SupplementaryProtective Bonding Conductors .
However:- Such bonding may called for in the Boiler Manufactures . in which case BS-7671:2008 .requires those Instructions to be followed ( Regulation 510.2. refers )
Anystated requirements for Additional Bondingthat is considered to be Unnecessary should be queried with the Manufactures Concerned. & Amended Installation instruction requested .

 

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DoesBoiler pipework need to have Main Protective Bonding Conductor for ElectricalSafety Reasons .

Regulationnumber(s) 411.3.3 . :aureola:

 

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Isan RCD Main Switch . ( Such as a 100mA time – delayed device )still required in the Consumer Unit of a New Domestic Installation forming partof a TT System . :dupe:

Fora Domestic Installation complying with the 17[SUP]th[/SUP] Edition where allthe Final Circuits are RCD – protected .
AnRCD Main Switch. is NOlonger required . Provided that the Consumer Unit is of all Insulated Construction .

2392-10:-
Asthe Designer of an Installation . Am I allowed to rely on the RCD element of an RCBOto provide for Fault Protection in order to allow for ( Loop ImpedanceValues ) Greater than given in Table 41.3 .

Yes) . So long as all the other Applicable requirements of the 17[SUP]th[/SUP] Edition ( as Amended ) are met .Including those for protection against Overload & Short – Circuit .
Regulationnumber(s) 411.4.4. - 411.4.5. - 411.4.9. :aureola:

Wherethe Earth Fault Loop Impedance for a circuit Exceeds the Maximum ( Zs) for the Overcurrent Device . is it permissible to use an RCD .
Yes:- Regulation . 411.4.4. - 411.5.2.

CanI use an ( Electrical Connector ) having “ push fit “ connections that the Manufacturer claims areMaintenance free in an area that will be inaccessible when the installation iscomplete .

NotNecessarily . Not all types or designs of Push Fits ( Screw less – type ) Clamping with the requirements ofRegulation - 526.3. ( vi )

Ifthe connector will be inaccessible when the Installation is complete . it mustComply with BS-5733 for a Maintenance – free accessorywith the Manufactures Instructions .

BS-5733 Requires . Example . Tests for Résistance to ageing .Cyclic loading . Overload . Fault current & Vibration .

 

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Workingmy way around the 17[SUP]th[/SUP] Edition – Protection . Isolation . Switching. Control & Monitoring .

Making you aware of “ Motor Control:

537.5.4. “ Plain English “ :rant:

537.5.4.1.) Non – automatic restart .
537.5.4.2.) Non – reversal of Motor on breaking .
537.5.4.3.) Non – reversal of Motor for SafetyPurposes .

 

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Sizing of Main & CircuitProtective Conductors’ . :icon_bs:

(K1 ) = k value for Line Conductor – Table 43.1. – p/49
( K2 ) = k value for ProtectiveConductor – Table 54.2. – 54.6. - p/129 . p/130 .

 

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Workingmy way around the 17[SUP]th[/SUP] Edition . 2392-10

Regulation. 544.1.2. Main ProtectiveBonding Conductor . ( Gas / Water ) :rant:

Positioningof Bonding Connection . ( Apprentices –look at the drawings – p/32 – Regulations )

17[SUP]th[/SUP]Edition . The main equipotential bonding connection to any . Gas . Water . orother services shall be made as near as practicable to the point of entry ofthat “ Service “ into the premises . Where thereis an Insulating section or insert at that point . or there is a ( Meter ) Theconnection shall be made to the Consumer’s hard ( MetalPipework ) & before any branch pipework . Where practicable theconnection shall be made within ( 600mm ) of themeter outlet union or at the point of ( Entry ) to the building if the meter isExternal .

Thisone may come up in Exams . -&-s

 

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Workingmy way around the 17[SUP]th[/SUP] Edition . 2392-10

Regulation. 544.1.2. Main ProtectiveBonding Conductor . ( Gas / Water )

External Supply Meters . are Bonded at thePoint of Entry . ◄◄◄ :icon_bs:

 

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Workingmy way around the 17[SUP]th[/SUP] Edition . 2392-10

Regulations. p/32 . The . How’s & Why’s . Fig / 2.1

(2 ) - Main Protective Bonding Conductors .

Protective Bonding must beApplied to all Areas where there is .

TheLikelihood of ElectricShock is Greatly Increased to Water . :icon_bs:

 

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Workingmy way around the 17[SUP]th[/SUP] Edition . 2392-10

Definitions. p/24 .

Extraneous-Conductive-Part. Conductive part liable to introduce apotential . generally Earth Potential . & not forming part of theElectrical Installation .

( A Metallic Fixture notassociated with the Electrical Installationthat could become Live under Fault Conditions ) :icon_bs:

 

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Workingmy way around the 17[SUP]th[/SUP] Edition . 2392-10

525 (- Volt Drop for NormalOperation – Appendix 2 & 12 . ) 2392-10 . :icon_bs:

Formula: to find the Actual Volt Drop when the Cable is known . App 4 .
( V.D. / max = mV / A / m x Ib x L / 1000 )

Alternativeformula when the Cable is NOT Known & theminimum size is to be found :

( mV /A/ m – max = V.D./ max = V.D. – max x 1000 / Ib x L )

 

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ApplyingElectrical Design . :smug:

Selectcable size from Appendix 4 .
• Cableselection for type should have already been considered due to initial characteristicsof purpose . Environment . Maintainability . part 3 & 4 . Appendix 5 – External Influences .

• Appendix4 – table 4A1 provides methods of Installation which are cross referenced whenselecting the maximum Current Carrying Capacity ofthe circuit cable . p/260 .

• 2392-10 . DomesticInstallation cables are to be used the Appendix 4 – Table 4D5 . ( Sheathed flat cables) T&E.

525.1– Requirements for volt drop inbuildings .

Table 12 – Voltage Drop . Regulation - p/358

Making you Aware .

(i) Low voltage Installations supplied directly from apublic Low voltage distribution system ( lighting – 3% ) – ( Other uses 5% )
(ii)Low voltage Installations supplied from private LV supply – ( * ) ( lighting – 6% ) – ( Other uses 8% )

( * ) The voltagedrop within each final circuit should not exceed the values given in ( i )

Wherethe wiring systems of the Installation are longer than ( 100m ) .the voltage drops indicated above may be increased by ( 0.005% ) per metre of the wiring system beyond ( 100m ) without this increase being greater than ( 0.5% )

Thevoltage drop is determined from the demand bythe Current-using Equipment . applying Diversity factors where Applicable. or from the value or the Design Current of the Circuit .

Current– Using Equipment :17:

554.1.Electrode water heaters & boilers .

554.1.4. RCD tooperate in Excess of 10% of rated current but can be extended to 15% dependant upon machine . Time Delay RCDs maybeUsed .