Re-take - Useful Information for 2394 :

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BS-1361 fuse, Type I and Type II.

BS-1361 Type I rated 240v 16.5kA
BS-1361 Type IIa rated 415v 60/80A 33kA
BS-1361 Type IIb rated 415v 80/100A 33kA

BS-1361:1977:
Specification for cartridge fuses for a.c. circuits in domestic and similar premises

Requirements, ratings and tests for fuse links, fuse bases and carriers. Dimensions and time/current zones for fuse links.
Type I-rated 240V and 5A to 45A for replacement by domestic consumers .
Type II-rated 415V and 60A, 80A or 100A for use by the supply authority in the incoming unit of domestic and similar premises.

The Type I's are little ones that fit in the consumer unit fuseholders.
The Type II's are big ones that fit in the service cut-out fuseholder. ( DNO ) 33kA distributors service heads.

Fuse(s)
On what principle does the fuse operate .

The action of a fuse is based upon the heating effect of the electrical current . During overloads or Short-circuits the fuse gets heated up to melting point due to excessive current and breaks the circuit .

Fuses :
Typical Industrial Applications

( aM ) Motor circuit protection against short-circuit only . ( Partial range )
( gG ) General purpose fuse essentially for conductor protection
( gM ) Motor protection

Fuse : short for fusible link .

BS-1361 Type II fuses are used in electrical mains incomers

 

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The term ‘ rated current ’ generally means the same as ‘current setting ’, as used in BS-7671 in relation to protection against overcurrent.

Overcurrent instantaneous tripping (‘Type’ of RCBO)

RCBOs conforming to BS-EN-61009-1 are classified into three distinct ‘Types’, known as Type B, Type C and Type D.
according to their instantaneous tripping overcurrent. Instantaneous tripping overcurrent is the minimum value of current causing an RCBO to operate automatically without intentional time delay (that is, within a time not exceeding 0.1 s or 100ms).

BS-EN-61009-1 permits instantaneous tripping to occur at a value of overcurrent, expressed as a multiple of the rated (or nominal) current (In)
Standard values of rated residual operating current given in BS-EN-61009-1 . 0.01A, 0.03A, 0.1A, 0.3A and 500mA / 0.5A.
( by calculation - 30mA ÷ 1000 = 0.03A ) 10 , 30 , 100 . 300mA

Rated residual operating current, IΔn
Rated residual operating current ( IΔn ) of an RCBO is the value of residual current, assigned to the RCBO by the manufacturer, at which an RCBO operates under specified conditions.

Where the function of an RCBO as a residual current device (rather than that as an overcurrent device) is used for fault-protection as part of the protective measure Automatic Disconnection of Supply (ADS)

Residual current breakers conforming to BS-EN-61009 all have a conventional tripping current of 1.45 (In) The related conventional time is 1 hour for circuit-breakers of rated currents (In) up to and including 63 A, and 2 hours for circuit-breakers of rated currents greater than 63 A.

Ambient air temperature, normally of 30°C.

in this case RCBOs :- its contacts are in the Open-position , Regulation’s 537.2.2.2. and 537.3.2.2.

537.2.2.2.
the position of the contacts or other means of isolation shall be either externally visible or clearly and reliably indicated . An indication of the isolated position shall occur only when the specified isolation has been obtained in each-pole .

537.3.2.2.
A device for switching Off for mechanical maintenance or a control switch for such a device shall require manual operation .

the Open-position of the contacts of the device shall be visible or be clearly and reliably indicated .

Note : The indication required by this regulation may be achieved by the use of the symbols “ 0 “ and “ I “ to indicate the open and closed positions respectively .

RCBOs , Suitability for use for isolation and switching Table 53.4. BS-EN-61009-1.
Isolation : Yes (3) Device is suitable for On-load isolation . i.e. disconnection whilst carrying load-current .
Functional switching : Yes .. ( you.re in control )

 

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Taken from old notes .

2008: 433.1.5.
2011: 433.1.103.

( Ib ) in each leg of cable is not to exceed 20Amps . current will not be the same all round ring-final-circuit .
assumed to be 20A at far end additional ( 12A ) evenly distributed [ 32A + 20 = 52A ÷ 2 = 26A ] L.v.d. = 4 ( 5% ) 11.5 x 1000 ÷ 26A ÷ 18mV = 98.3m
( 4 x 11.5 x 1000 / 26 / 18 = 98.3m )

The maximum circuit length is then the smallest of ( 2 to 4 ) Regulation . Table 4D5 . Particular interest for Domestic and Office installations
Ring-final-circuit . 2.5mm[SUP]2[/SUP] - 1.5mm[SUP]2[/SUP]

Table 4D5 . 18mV assuming ( Ib ) 32A
L.v.d. 4 x 11.5 x 1000 ÷ 32 ÷ 18 = 79.9m

( Cable doubled (2) cable length to farthest point

BS-1363 20A . 411.3.3 Ordinary persons
P/278 . BS-1363 13A plugs , socket-outlets etc 433.1.103.
P/174 . Table 55.1. Fused plugs and shuttered socket-outlets . 2-pole and earth . for A.C.

P/174 . 553.1.100.
Every socket-outlet for household and similar use shall be of the shuttered type and . for A.C. installation , shall preferably be of a type complying with BS-1363 .

Appendix 15 ( Informative )
This appendix sets out (( Options for the design )) of Ring and Radial final circuits for household and similar premises in accordance with Regulation 433.1.

P/426 . Fused connection unit ( FCU ) to BS-1363-4 . maximum fuse 13A
Junction box to BS-EN-60670-22 .
junction boxes with screw terminals must be accessible for inspection . testing & maintenance or , alternatively , use maintenance-free terminals / connections . Regulation 526.3.

 

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Extracts .
Final circuit PVC (( Thermoplastic )) Sheathed cable .

Determine the cable size and suitable BS-EN-60898 circuit breaker for a 3.65kW storage heater installed in an office. The heater is to be wired in thermoplastic insulated and sheathed 6242Y cable (PVC sheathed). The circuit length is 20 metres and the cable will be in contact with thermal insulation exceeding 100mm in thickness on one side for a significant part of its run above a plasterboard ceiling

The characteristics of the supply are as follows:
Nominal Voltage = 230 volts
PFC at origin = 1.75kA
Ze at origin = 0.13 ohms

Answer
Step 1 Calculate design current ( Ib )
Total Ib =
Ib = 15.9 amps

Step 2 Select protective device ( In )
As we have seen Ib ≤ In and Ib = 15.9 amps The nearest suitable size of circuit breaker would be a 16 amp Type B from Table 41.3 (Part 4 BS-7671: 2008).
( In ) = 16 amps.

Step 3 Determine maximum disconnection time
The maximum disconnection time for compliance with 411.3.2 for a final circuit not exceeding 32A is 0.4 seconds.

Step 4 Determine correction factors
There are no correction factors applicable but the cable is directly in contact with thermal insulation exceeding 100mm in thickness on one side. This means that the only de-rating required is to choose the sheathed cable size from Table 4D5 referring to Reference Method 101 (column 3).

Step 5 Applying correction factors
No correction factors to apply.

Step 6 Select the cable size ( Iz )
It replaces ( In )
It = 16 amps From Table 4D5 (Appendix 4 BS 7671: 2008 (2011))
Reference Method 101 column 3 the nearest suitable size of thermoplastic insulated and sheathed cable (PVC sheathed) to carry 16 amps is 2.5mm² which can carry 17 amps (in this instance).

Iz = 17 amps
Cable size = 2.5mm[SUP]2 [/SUP]

Step 7 Check shock constraints
The maximum Zs value for a 16 amp Type B circuit breaker from Table 41.3 (Part 4 BS-7671: 2008 (2011)) is 2.87 ohms

Zs = 0.6 ohms where Ze = 0.13 ohms
F = 1.2 from Table 3 (Page 10) of these notes
R1 + R2 = 19.51mohms/M for 2.5/1.5mm2 cable from Table 4 (Page 20) of these notes
L = 20 metres (given in question)

which is acceptable as it is less than 2.87 ohms from Table 41.3.

Step 8 Check thermal constraints
The CPC of the thermoplastic insulated and sheathed cable (PVC sheathed) does not comply with Table 54.7 so the adiabatic equation must therefore be applied.

S = 1.05mm2
where I = Fault current
t = Disconnection time of fault current
t = 0.1s from Fig 3A4 Appendix 3 BS 7671: 2008 (2011) for 16 amp BS-EN-60898 Type B circuit breaker at 383.3 amps
k = 115 from Table 54.3 (Part 5 BS 7671: 2008(2011)) for 70°c PVC

As the CPC of the cable is 1.5mm² and the minimum CSA for thermal constraints is 1.05mm[SUP]2 [/SUP] the CPC is adequate.

Step 9 Check voltage drop
where mV = 18mV from Table 4D5 (Appendix 4 BS 7671: 2008 (2011))
Ib = 15.9 amps
L = 20 metres

VD = 5.7 volts which is acceptable as 5% of 230 volts = 11.5 volts

 

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Regulation 411.4.7.
Where a circuit-breaker is used . Etc
The values specified in Table 41.3. for the types and ratings of overcurrent devices listed may be used instead of calculation .

Calculation for BS-EN-60898-1 circuit-breakers (( only ))
Type B , ( Zs ) 20A type B / C / D can be calculated , Sherlock Ohms
5 x 20 = 100
230 ÷ 100 = 2.3Ω [ 20A – 2.30 ]

Type C , ( Zs ) 10 x 20 = 200
230 ÷ 200 = 1.15Ω

Type D , ( Zs ) 20 x 20 = 400
230 ÷ 400 = 0.57Ω

( Zs ) value for a 20A Type 1 BS-3871 .
4 x 20 = 80
230 ÷ 80 = 2.87Ω

O.S.G. Table 7.2.7.(ii) P/72
Circuit-breakers BS-3871-1
Type 1 . Multiplier ( 4 )
Type 2 . Multiplier ( 7 )
Type 3 . Multiplier ( 10 )
Type 4 . Multiplier ( 20 )

 

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Enhanced Fire Safety from Consumer Units

Amendment 3 to BS-7671:2008 Requirements for electrical installations ( IET Wiring Regulations ) will be published on 5[SUP]th[/SUP] January 2015 . These new and changed regulations will apply to all Electrical Installations designed after 1[SUP]st[/SUP] July 2015 * . Whilst there are many additions and changes being introduced through this amendment , it is expected that there will be specific new regulations relating to the enhancement of Fire Safety.

One particular regulation , 421.1.201. is expected to address the selection of Consumer Units in domestic ( household ) premises and , as such , introduces a new enhanced functionality to this equipment . The regulation is expected to state :

“ Within domestic ( household ) premises , consumer units and similar switchgear assemblies shall comply with BS-EN-61439-3 and shall :
(i) Have their enclosures manufactured from non-combustible material ,
Or
(ii) Be enclosed in a cabinet or enclosure constructed of non-combustible material and complying with regulation 132.12.

Note (1) : Ferrous metal e.g. steel is deemed to be an example of a non-combustible material
Note (2) : * The implementation date for this regulation is the 1[SUP]st[/SUP] January 2016 .
This does not preclude compliance with this regulation prior to this date “

The intent of regulation 421.1.201 is considered to be , as far as is reasonably practicable , to contain any fire within the (( Enclosure )) and to minimise flames from escaping , caused mainly as a result of poorly instead connections .

What is a definition of “ Non-combustible “
There is no published definition for “ Non-combustible “ that aligns with the intent of regulation 421.1.201. Ferrous metal , e.g. steel , is deemed to be one example of a non-combustible material that meets the intent of the regulation .

What constitutes a “ Non-combustible enclosure “
A non-combustible enclosure includes : Base , Cover , Door , and any components , e.g. Hinges , Covers , Screws and Catches , necessary to maintain fire containment .

Blanks and devices are contained within the non-combustible enclosure .

How is account taken of cable entries into a non-combustible enclosure “ with respect to containment of internal fire and escape of flames ?
Good workmanship and proper materials must be applied by the installer . The cable installation entry method shall , as far as is reasonably practicable, maintain the fire containment of the enclosure . Account shall be taken of the manufacturer’s instructions , if any .

What is meant by “ Similar switchgear assemblies “ ?
“ Similar switchgear assemblies “ are assemblies used for the same fundamental application as consumer-units .

Does regulation 421.1.201. apply to consumer units and similar switchgear assemblies installed in domestic ( household ) garages and outbuildings . ( Yes ) the intent of regulation 421.201. is that it applies to consumer units and similar switchgear assemblies to BS-EN-61439-3 . inside all domestic ( household ) premises including their integral / attached garages and outbuildings or those in (( close proximity ))

[h=1]Design Verification :- BS EN 61439-3:2012[/h][h=2]Low-voltage switchgear and controlgear assemblies. Distribution boards intended to be operated by ordinary persons (DBO)[/h]
Extracts form IET.
Does this mean all installed consumer units with plastic enclosures are a fire risk ?

No, provided the consumer unit and its incorporated components conform to the relevant product standard(s), do not have latent defects, and have been installed correctly to the manufacturer’s instructions.

Definition of non-combustible:

2011: P/277 :- BS-476: Part 4: 1970 Non-combustibility test for materials.
This test classifies materials as either ' non-combustible' or 'combustible '. It is the most stringent standard for the fire performance of materials and gives a measure of the heat and flames generated by the material under standard heating conditions. Non-combustible materials can be used without restriction anywhere in a building. Their use ensures that hazards due to smoke and toxic gases are " minimised " and that the fabric of a building will not make a contribution to a fire.

 

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In 2012/4 253 London Fire Brigade recorded fires where a consumer unit was identified as the source of ignition.

Number of fires :
2005/06 - 27
2006/07 - 28
2007/08 - 33
2008/09 - 21
2009/10 54
2010/11 - 73
2011/12 - 71
2012/13 - 220
2013/14 - 253 ... offending CU

 

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[h=1]Extracts :
Circuit breakers used as switching devices[/h]
The 17th edition introduced a quick selection table 53.4 to assist with the selection of devices used for various functions such as isolation, emergency switching and functional switching.

This table suggests that circuit breakers to BS-EN-60898-1, BS-EN-60947-2, and RCBO’s to BS-EN-61009-1 are suitable to be used as functional switches. So in a shop for instance where the lights may be either all on or all off the circuit breaker in the distribution board could be used to switch the lights on and off.

Whilst circuit breakers are suitable to switch loads of course, their primary function is as circuit protection devices and depending on the type of load they are switching may not be the best product to select for this purpose.

For this reason Amendment 3 has added a small note to this table stating:
Circuit-breakers and RCDs are primarily circuit-protective devices and, as such, they are not intended for frequent load switching. Infrequent switching of circuit-breakers on-load is admissible for the purposes of isolation or emergency switching.

For a more frequent duty, the number of operations and load characteristics according to the manufacturer’s instructions should be taken into account or an alternative device from those listed as suitable for functional switching in Table 53.4 should be employed.

So specifiers or installers should either consult the manufacturer of the circuit breaker giving information as to the type of load being switched or better still use a device listed in the table as a switching device which are designed for this frequent duty.

10th December 2014

 

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Table A2 ( 1 ) Lighting . 66% of total current demand

6 - Fluorescent lamps : ( 1.8 ) P/110 - Note ( 2 )
Table A1 Lighting circuit , Current equivalent to the connected load, with a minimum of 100W per lampholder .
Assume 100W per lamp and from note (2) , multiply the lamp wattage by ( 1.8 ) I = W x 1.8 / V = 6 x 100 x 1.8 / 230 = 1080 / 230 = 4.7A

10 x 58W Single linear fluorescent lamps , 10 x 58W = 580W , multiply by 1.8 to give 1044 VA and hence 4.5A .
( contain modern HF ballasts or power factor correction )

if the ( VA ) rating of the lighting units is unknown , then use the rated wattage of the actual tubes / lamps used multiplied by ( 1.8 to arrive at an estimate of the ( VA ) rating for the lamp and ballast ) 10 x 580 , 580 x 1.8 = 1044 VA

 

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Homeowners report carried out . ( EICR )
Question’s to be Asked . ??

- Never act upon the recommendations .
- Electrical Installation Condition report .. Observations ; you could probably put money on them never being touched .
- Report will never see the light of day again . (Stuck in a drawer) next time around . ( Yeah )

Electrical Installation Condition Report is not a certificate. ((Condition reporting Only )) ... satisfactory condition for continued service

Periodic Inspection & Testing
621.1. Where required , periodic inspection and testing of every electrical installation shall be carried out in accordance with Regulation 621.2. to 621.5. in order to determine , so far as is reasonably practicable , (( whether the installation is a satisfactory condition for continued service )) Wherever possible Etc.

621.2. Periodic inspection comprising a detailed examination of the installation shall be carried out without dismantling , or with partial dismantling as required , as required , supplemented by appropriate tests from Chapter 61 to show that the requirements for disconnection times , as set out in Chapter 41 for protective-devices , are complied with , to provide for : refer

 

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All users of the IET Wiring Regulations need to be aware of the coming changes in Amendment No 3 to the 17[SUP]th[/SUP] Edition ( BS-7671:2008+A3:2015)
Consumer Units ( to come into effect January 2016 )

New Amendment BS-7671 : 1[SUP]st[/SUP] January 2015 . Options - for six months you can install to Amendment 2 or Amendment 3 , that means as from 1[SUP]st[/SUP] of July 2015 all electrical installation’s design to the new Amendment shall be installed to the new Amendment and certified to the third Amendment .

1[SUP]st[/SUP] July 2015 Certified :- To guarantee as meeting the standard . “ certification “

Amendment No 3 publishes on 5 January 2015 and comes into effect on 1[SUP]st[/SUP] July 2015 , All new installations from this point must comply with Amendment No 3 to BS-7671:2008

 

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Appendix 3 Time/current characteristics of overcurrent protective devices and RCDs
This includes changes in connection with maximum earth fault loop impedance to take account of the Cmin factor given in CLC/TR50480:2011.

December 2012
PD CLC/TR 50480:2011
Determination of cross-sectional area of conductors and selection of protective devices

Descriptors
Electric cables, Power cables, Insulated cables, Electric conductors, Copper, Aluminium, Stranded conductors, Flexible conductors, Electric wires, Diameter, Electrical resistance, Resistance measurement, Dimensional tolerances

[h=3]‘Cmin’ factor[/h]Maximum earth fault loop impedances given in Tables 41.2, 41.3, 41.4 and 41.6 will be revised to take into account the Cmin factor given in CLC/TR50480:2011.

Cmin is the minimum voltage factor to take account of variations in voltage, depending on time and place, changing of transformer taps and other considerations. The notes to the Tables will be changed to reflect maximum permitted operating temperature. In addition, Regulations 411.5.4 and 41.6.4 will include a Cmin factor.

( Zs change every single Zs value throughout BS-7671: ( A3 ) will be changing , the new factor coming in Cmin it will reduce all exciting Zs values 0.05%

 

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Installation method change ( A3 )

Escape routes :- you are not allowed to rely on plastic or non-metallic means of support , that means plastic trunking or plastic tray what you have to do , you can still use it but support it with metal fixings and make sure that it does not come down , also if you have used ( Cable Ties ) plastic tie wraps in the past , you will have to use metal tie wraps stopping the cable dropping down in the event of a fire .

 

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Sticking to the theme of fire’s .

( CCU ) consumer units ( A3 )
Consumer units will have to change , what they’re saying now is ( Household ) domestic premises must be made of Non-combustible martial , to give you an example of Non-combustible martial ( Ferris metal , example Steel ) take effect on 2016

 

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Changes ( A3 )
Model form’s ; electrical installation’s ( Certification )

Electrical Installation Certificate
Schedule of items Inspected, use to be a tick box with 44 boxes now it’s going to be 3 pages worth , (( Now to 120 boxes ))