Re-take - Useful Information for 2394 :

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The following is an analysis of possible changes for Amendment No 2, after it had been reviewed by CAG 25 Nov 2011.

Each panel is asked to “consider/reconsider” each of the comments below ASAP. The panel should: Agree, indicate if Editorial or T), Not agree, amend (propose something similar or new), WIP or allocate to AMD 3

132.15.1 and 132.15.2
Comment (justification for change)

132.15.1 and 132.15.2 should be deleted as the fundamental requirement for disconnecting devices is now to be found in the new regulation 132.10. Furthermore, there is no need for the content of regulation 132.15.2 (which relates to only one type of equipment) to actually appear in Chapter 13 (fundamental principles )

Specific requirements for motor control arrangements already exist elsewhere in BS 7671 and the general requirements for isolation, switching for mechanical maintenance, functional switching and emergency switching contained in section 537 should be applied to motors as appropriate to particular circumstances.

We now have two regulations (132.10 and 132.15.1) saying much the same thing with differing degrees of emphasis.

Proposed change
132.15.1 and 132.15.2 should be deleted
Note: A previous response to this deletion made during the final phase of Amd No 1, was:
132.15.2 which, as previously stated, has no logical place in Part 1 of the regulations and which is very commonly misunderstood by users of BS 7671.

These regulations should not be deleted, for the following two reasons.

(1) Approved Document P clause 0.1 indicates that the requirements of Schedule 1 to regulation 7 of the Building Regulations for England and Wales will be met by adherence to the fundamental principles in Chapter 13 of BS 7671. Those fundamental principles will be deficient without Regulations 132.15.1 and 132.15.2.

(2) Regulation 12 of the Electricity at Work Regulations 1989 requires means for isolation.
But it was also agreed that “ the issue be reconsidered for Amd 2 ”

 

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Consumer Units for Domestic Household and other Premises .

17[SUP]th[/SUP] Edition wiring regulations incorporating Amendment No 3 :2015

Firstly ; Regulations relating to 421.1.201. (( Enhancement of Fire Safety )) caused by Electrical Equipment
421.1.201 that is intended to improve fire safety in domestic premises.

421.1.201. as far as is reasonably practicable, to contain any fire within the enclose and to minimise flames from escaping caused mainly as a result of poorly installed connections .

The crucial importance of checking that all electrical connections are properly made
(( Screw terminals to make significantly reducing risk of loose connections )) manufacturer’s PS wish list

The intent of Regulation 421.1.201. 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 .

One of the most common fault . :yesnod: Neutral conductor
Failure to tighten neutral conductor connections to the same torque as line conductor connections due to a misconception that neutral conductors carry less current.

Inadvertently taking cable insulation inside the terminal at a connection, resulting in the securing screw or the clamp of the terminal not making proper contact with the conductor.

Failure to check factory installed connections for tightness where required to do so by the manufacturer; and tightening connections to an incorrect torque and/or with inappropriate tools.

Good workmanship and proper materials must be used, and account must be taken of the manufacturer’s relevant instructions, if any.

 

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Extracts .

Similar switchgear assemblies :icon_bs:
The phrase ‘similar switchgear assemblies’ in Regulation 421.1.201 means those assemblies used for the same fundamental application as a consumer unit. A consumer unit is defined in Part 2 of BS-7671:

‘Consumer unit (may also be known as a consumer control unit or electricity control unit). A particular type of distribution board comprising a type-tested co-ordinated assembly for the control and distribution of electrical energy, principally in domestic premises, incorporating manual means of double-pole isolation on the incoming circuit(s) and an assembly of one or more fuses, circuit-breakers, residual current operated devices or signalling and other devices proven during the type-test of the assembly as suitable for such use.’

An example of a similar switchgear assembly is a three phase distribution board that is intended to be operated by ordinary persons. This would have to have isolation that interrupts the three incoming line conductors and the neutral, rather than just double-pole isolation as mentioned in the above definition. :aureola:

 

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Regulation 421.1.201 was principally introduced to cover the interior of a household building and any garage or other outbuildings integral, attached, or in close proximity to that building.

The intent of Regulation 421.1.201. 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 .

 

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( BR ) What’s the right height for fixing socket outlets, switches and controls ?

It all depends on what sort of building you are working on and if it is:
New
Complete rewire would be an opportunity to install accessories in line with Building Regulations
Existing
In existing dwellings, switches and controls are generally higher and outlets lower than the mounting heights required by Building Regulations.

re-cap (A2)
Sockets that are too LOW should be moved - 553.1.6 page 174
A socket-outlet on a wall or similar structure shall be mounted at a height above the floor or any working surface to minimize the risk of mechanical damage to the socket-outlet or to an associated plug and its flexible cable which might be caused during insertion, use or withdrawal of the plug

In a world of ever-changing legislation

Regulation 132.12 & Building regulations Part M

Electrical equipment is referenced in two separate parts of the Building Regulations:

Part P of the Building Regulations relates to electrical safety in dwellings.

The approved document prescribes that switches, sockets and consumer units in new dwellings should be easy to reach, in accordance with Part M of the building regulations.

Part M which deals with access to and use of buildings, and recommends that switches sockets and other equipment should be located between 450mm and 1200mm from finished floor level and does not specifically mention the consumer unit.

However, Part P suggests one way to comply is by mounting the consumer unit so that the switches are between 1350mm and 1450mm from the finished floor level.

The consumer unit also needs to be accessible

therefore the location and the height need to be taken into consideration. For instance a small under-stair cupboard may be classed as difficult to access and hence be an unsuitable place to install a consumer unit. Care should also be taken that the consumer unit is placed in a position where it not likely to be damaged by impact.

Stair cupboard may be classed as difficult to (( access ))
I wish the DNO was consulted on this matter over the years, alcoves or cupboard(s) high up near the ceiling.. “ Unique concept ” you wonder why Electricians have back trouble , Risks and assumptions

Compliance BS-7671: (A2)

• Regulation 132.12 Accessibility of electrical equipment bullet point (ii)

Electrical equipment shall be arranged so as to afford as may be necessary:
(ii) accessibility for operation, inspection, testing fault detection, maintenance and repair.

re-cap (A2) Existing
Sockets that are too LOW should be moved - 553.1.6 page 174
A socket-outlet on a wall or similar structure shall be mounted at a height above the floor or any working surface to minimize the risk of mechanical damage to the socket-outlet or to an associated plug and its flexible cable which might be caused during insertion, use or withdrawal of the plug

 

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In the form of Isolation . Kitchen Safety
(ESC)

2013 : if appliances such as fridges , dishwashers , washing machines are fitted under worktops’ , getting to (( Socket-outlets )) may be difficult . ideally , these appliances should be controlled by a (( Switched fuse connection unit )) mounted above the worktops where you can reach it easily

A washing machine etc. will normally fit into a space and the only way to reach the isolation point (Plug and socket) would be to pull out the machine

Isolation switches for white goods in a kitchen

So the main (( Question )) is the plug is readily available would remove the requirement to fit isolators. ( 99.9% NO )
in an “ Emergency “ aspect
Washing machine was why you wanted to switch if off dragging it out while it is trying to bash you kitchen to pieces is not really an option .
So in your case here , After sore knuckles , The Means of isolation should be provided .

Washing machines
Dishwashers
Tumble dryers
Under counter fridges Etc

Isolation Switch .
Shower isolation switch
Cooker isolation switch
Main isolation switch ( CCU )
Isolation of kitchen appliances .. the need for , to fit isolators ( Spurs )
Isolation for fans in Bathrooms Etc .

 

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(A2) 2011: CCUs loose connections .

Where torque settings for connection tightness are specified in manufacturers’ instructions, does this mean installers must confirm these settings during work using a torque driver

Regulations 134.1.1 and 510.3 state that manufacturers’ instructions are to be taken into account during installation work. It is necessary to check that all connections are tight, and the use of a torque screwdriver is one way of confirming this.

134.1.1 Erection
510.3 Every item of equipment Etc . refer :icon_bs:

 

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Known one ask for ( Vd ) anymore

Reminder . 612.14. Verification of voltage drop
Note : Verification of voltage drop is not normally required during initial verification .

it’s just a learning curve

Voltage drop calculations .. Voltage drop = mV x Ib x length / 1000
Where the voltage drop is in volts and:
mV is the millivolts dropped per ampere per metre
Ib is the design current of the current of the circuit ( the current intended to be carried )
Length is the length of the circuit in metres. The division by 1000 gives the answer in volts .

Résistance of copper conductor
in order to design for compliance with BS-7671 limiting values of earth fault loop impedance given in Tables 41.2 to 41.4 it is necessary to establish the relevant impedance of the circuit conductors concerned at their operating temperatures

O.S.G. Table 11 1.5mm[SUP]2[/SUP] with 1.0mm[SUP]2[/SUP] earth , CPC is given as 30.20mΩ therefore if the cable is 20mts in length this will be
30.20 x 20 ÷ 1000 = 0.60Ω which is the value of R[SUP]1[/SUP] + R[SUP]2[/SUP]

( VD ) ( A2 ) 2011 .. “ Single cables “
Identify a suitable cable - Table 4D1A P/332 reference method B
1mm[SUP]2[/SUP] cable has a rating of ( 4 ) 13.5A

Calculate the voltage drop ( Vd ) BS-7671: Table 4D1B P/333 reference method A & B .. Conduit
Voltage drop = ( mV/A/m ) x Ib x L ÷ 1000 .. 44 x 4.35 x 23 ÷ 1000 = 4.4V

Appendix 4 P/314
This circuit complies with the requirements of BS-7671:2011: in the calculated volte drop ( 4.4V ) is less than the maximum permitted ( 3% ) for a single phase lighting circuit .. Single phase 3% of 230V = 6.9V

 

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( A2 ) 2011
it’s just a learning curve ( Q )

BS-7671: identifies that the cross sectional area of a conductor shall be determined by :
a) the admissible maximum temperature
b) the nominal voltage
c) voltage tolerance
d) the earthing system

You go straight to BS-7671:2011 :icon_bs: index and look up ( CSA ) of conductors and cables P/442 , you will find reference to 132.6. Sec 524
you would now look in Part 1 Chapter 32 regulation 6 P/19

Your Answer is : The ( CSA ) of conductor(s) shall be determined for both (( normal operating conditions )) and where appropriate , for fault conditions according to : (i) the admissible maximum temperature
Therefore you know that ( A ) must be the answer .

 

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( A2 ) 2011 :icon_bs:
it’s just a learning curve ( Q )

The algebraic sum of the currents in the live conductors of a circuit at a point in the electrical installation is known as the :
a) residual current .... (( resi/dual-current ))
b) harmonic current
c) Line current
d) Neutral current

P/444 looking in the BS-7671:2011: index the only (( Phrase you can find )) from the Question is Electrical installation , Definition Part 2
looking in Part 2 Definitions P/33 . (( Residual current ))
Algebraic sum of the currents in the live conductors of a circuit at a point in the electrical installation

 

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( A2 ) 2011
it’s just a learning curve ( Q ) :icon_bs:

Which one of the following cannot be used as ( Basic Protection )
a) isolation of live parts
b) barriers or enclosures
c) protective earthing and bonding
d) obstacles

Options – a,b,d. all provide basic protection .. refer to Section 416 & 417 . P/66 / P/67
Option (c) provides fault-protection .. what is your Answer

 

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( Ze ) External loop impedance ... ( Testing you have proven an Earth into the building ) important test
( Zs ) = The earth fault loop impedance of the (( internal current carrying circuit ))
R[SUP]1[/SUP] + R[SUP]2[/SUP] = the sum of the résistance of the Line-conductor ( R[SUP]1[/SUP] ) and the circuit-protective-conductor ( R[SUP]2[/SUP] ) between the point of utilisation and the origin of the installation . Equitation Zs = Ze + ( R[SUP]1[/SUP] + R[SUP]2[/SUP] )

 

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[h=5]Meter Tail Investigation Report[/h]Download the full report ◄

Meter Tail Investigation Report , 805.00 KB ◄

Meter Tails
Electrical Safety Council ( ESC )

Investigation looking at the effects on the terminals of consumer unit main switches when the (( Meter Tails )) are disturbed using reference standard BS-EN-60947-1:2007 + A1: 2011

( CCU ) To assess the mechanical strength (( tightness )) of meter tail screw terminal connections typically found in consumer unit main switches . following

[url]http://www.electricalsafetyfir...htness-of-meter-tails/[/URL]

 

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Be aware of the Consequences

CCUs loose connections

 

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IET . 2015

Commonly, loose connections within consumer units can lead to overheating – one of the main causes of the units catching fire. With many based under the staircases of residential buildings, such fires can block exit routes and impede the ability to escape.