Re-take - Useful Information for 2394 :

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Can some one advise me on M/Soft words 2007? Please. it has is spacing’s . and onAuto . what am I doing wrong .

 

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As Electricians, Haveyou ever been Asked ??? ( 1000 – times ) Why doRCDs sometimes trip Unnecessarily Residual currentdevices (RCDs ) are used extensively in installation to provide ( Fault-protection) & ( Additional-protection ) againstelectric-shock Since the introductionof the 17[SUP]th[/SUP] Edition of the IET Wiring Regulations most, if not all finalcircuits in a new or re-wired installation in domestic premises to be providedwith , ( Additional-protection by anRCD ), having a rated residual operating current ( I∆n ) of 30mA and anoperating time not exceeding 40mS , at 5I∆n WhileRCDs provide an ( Enhanced Level) of Shock-protection, precautions should be taken to avoid , Unwanted-trippingof the devices on healthy circuits, Repeated unwanted tripping is likely todamage user confidence in RCDs, and has been known to result in them beingbypassed by frustrated consumers. Unwanted tripping ofRCDs can be caused by the current that may flow in the protective-conductor ofcircuit supplying certain items of Class-1 earthed-equipment during theirnormal operation, Such items include equipment-incorporating : • Electrical noise – ( radio-frequency ) suppressionfilters, such as personal computers’, hi-fi equipment, TVs, DVDs, & thelike .• Heating-elements,such as cookers, water-heaters or radiant-heaters Etc .• Motors,such as fridges & Freezers ( Common) To avoid unwanted-tripping,RCDs should be so selected and circuits so subdivided that anyprotective-conductor current expected to occur during normal operation of theLoad(s) will be unlikely to cause tripping of the device. Facts :That product standards permit certain equipment, such as personal computer’s tocreate up to 3mA of leakage currentin the protective-conductor In order to minimisethe risk of unwanted tripping of RCDs, the number of items ofprotective-conductor-current generating equipment per circuit, and the numberof circuits’ served by each RCD, need to be sufficiently small . Tripping of an RCD mayresult if the total protective-conductor-current in the circuit(s) it servesexceeds ( 50% ) of it’s rated residual operating current, that is ( 15mA for a30mA device )

 

[amjed]

hye i try to make my first 6 post sorry ..

 

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Re-cap : 2392-10.
Final-circuits ( As the Duty Holder ) Consumer-unit(s) is not Energised until all of itsfinal-circuits have been completed, and Inspected and Tested .

 

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Electrical Safety& Safe isolation procedures for ( low-Voltage-Installation )

Re-cap : Regulation’s BS-7671:2008:2011:

Regulationsgives ( Technical-Guidance ) on the Regulations .

It’s purposeis to amplify the Nature of the precautions in general terms so as to help inthe achievement of high standards of electrical-safety in compliance with theduties imposed . HSE .

Re-cap

Safe isolationprocedures ,

For all workon LV electrical-equipment or circuit(s), it is important to ensure that thecorrect point of isolation is identified, that an appropriate means ofisolation is used, and that the supply cannot inadvertently be reinstated whilethe work is in progress, The conductors must be proved to be dead at the point of work beforethey are touched . Etc

Re-cap : 2392-10.

In TT-systems, the incoming Neutral-conductor cannot reliably be regardedas being at Earth-potential .
For TT-Supplies, a double-pole-switching-device which disconnects the Line& Neutral-conductor(s) must be used as the Means of Isolation .

 

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The Regulations have stated the Facts .

Note : Table-53.4 . p/149 . Circuit-breaker(s)conforming to BS-EN-60898 are suitable for Isolation .
Miniature-circuit-breakers ( MCBs ) manufactured to earlier standards, such as BS-3871, are unlikely to besuitable for Isolation .
Switchgear conforming to BS-EN60947-3 & circuit-breakers & RCDsconforming to BS-EN60947-2 are suitable for isolation if marked with the symbol.

 

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Re-cap
Isolating Device(s)
Single-pole-switches are the most commonly used to control-circuit’s .
2392-10 : As the Regulations reminds us , These switches ( Isolate ONLY the line-conductor ) feeding the load .

 

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Switch : isa mechanical-device that can carry and break a current ( Under-normal-circuit-conditions )

Disconnector : is a mechanical-device that carriesthe design-current for its ( Intended-purpose )

 

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Re-cap :
The Term “ Isolation & Switching“ as used in BS-7671:2008:2011: refers to four-distinct-functions .
Isolation .537.2 , p/150
Emergency-switching . 537.4 , p/152
Functional-switching . 537.5 , p/153, for thereason of ( Control )
Switching off for , -Maintenance. 537.3 , p/151
Mechanical-maintenance p/152 : 537.3.2.4.
A device for switching off for ( Mechanical-maintenance ) shall be so placed and durably-marked so as to bereadily identifiable and convenient for the intended use .

 

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230V single-phase-supply rated up to 100A, are under the control ofOrdinary-persons,
Switchgear / Controlgear
Comply with BS-EN-60439-3 and Regulation 432.1 ,
Or
Be a consumer-unit incorporating components complying with, BS-EN-60439-3
Consumer-unit : 10 way High-Integrity consumer-unit , Main-switch 100A 230v/ 240V – 50Hz . Main-switch BS-EN-60439-3 , are under the control of Ordinary-Persons
p/284. Particular requirements for,LV switchgear & controlgear assemblies intended to be installed in places where,unskilled-persons having access to their use, BS-EN-60439-3 : 1991

 

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Isolation& Switching :

Isolation – To enableelectrical-work to be carried out safety on the isolate-circuit or equipment .
□ Electrically-skilled or Supervised-person .

Switching off for Mechanical-maintenance :

To enablenon-electrical-work to be carried out safety on the switched-circuit orequipment
□ Non-electrical-skilled-persons

Functional-switching :

To enable proper functioningand control of electrical-equipment
□ The user of the installation

Emergency-switching :

To cut off rapidlyelectrical-energy to remove an unexpected hazard
□ Anyone

 

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BS-7671:2011:

Switch-disconnector : p35 .
A switch which , in the open-position, satisfiesthe ( Isolating-requirements ) specified for a disconnertor .

Emergency-switching : p/27 .

An operation intended to remove, as quickly as possible, danger, which may have occurred unexpectedly.
Functional-switching : p/28
An operation intendedto switch “ On “ or “Off “ or vary the supply of electrical-energyto all or part of an installation for ( Normal-operating-purposes )
Isolation/29
A function intended to cutoff for reasons of safety the supply from all, or a discrete section, of theinstallation by separating the installation or section from every source of electrical-energy

 

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Taking from Extracts: Pastto Present.
TheTerm “ Isolation& Switching “ as used in BS-7671: from 2001 / 2011:
p/29 - Isolation: The definition ofisolation in BS-7671: ( A function intended to cut off for reasonsof safety the supply from all, or a discrete section, of the installation byseparating the installation or section from every source of electrical-energy)
BS-7671: have statedthe facts
Isolation:is provided to permit an electrically-competent-person to work safely on all orparts of an electrical-installation .
Onceelectrical-equipment has been securely isolated from the “ Sourceof energy “ has been discharged, askilled or instructed-person should be able to safely access parts that arenormally live, or may become live, without the ( Risk ofDanger ) from electrical-shock,electrical arcing or explosion or from ( Electrical-powered-equipment &Machines )

The corresponding-definition in the “ Electricityat Work Regulations “ adds the specific requirements that the isolation is tobe ( Secure ) EWR – 1989
This means the Isolated-equipment cannotbe ( Re-energised Accidentally or Inadvertently)
The procedure of “ Isolation“ includes

(a) Correct-identificationof the equipment and circuit to be ( Worked-On )
(b) Disconnection,
(c) Securingthe means of disconnection
(d) Postingnotices &
(e) Proving( Dead) In some cases additional-precautions will also be needed.

 

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Being an Electrician, Risks with this kind of Work !! :13: :icon_bs: “ You don’t get a second-chance “ ( Isolation ) Locking-OFF … ( Verify that All Conductors are indeed dead )


Providingthe Isolator is local to the Extract-fan : 2392-10 – Minimal-risk of : Inadvertently orUnintentionally switched back-ON (Locking-OFF )
There no room forsecond chance(s) in this profession . Stay alert and focused. Distractions can be fatal. ( Withany Circuits )

Re-cap : 2392-10 / 2394 : Facts ( Three-pole-Isolator ) which can be locked-OFF. MK

Isolation will arise duringthe lifetime of any Installation (Domestic-premises)

Local-Isolator in thelighting and extract-fan-circuit for a ( 2392-10 - Windowless-bathroom in Dwellings) Etc

Reason – TT-system .Isolate the fan from the ( Source of energy) in Order to work safely on it . boththe Line-conductor & Neutral-conductor(s)will need to be Isolated .

Part of theIsolation-procedure is to ( Verify that All Conductors are indeed dead )

Inadvertently orUnintentionally switched back-ON (Locking-OFF )

I00A Main-Switch in the Consumer-Unit ( Forma perfectly adequate means of Isolation ) Precautions - ( Locking-OFF )

• Circuit-breaker in the Consumer-Unit .Installation forming part of a , TN-system where theNeutral-conductor can be regarded as , being reliably connected with Earth, itmay not be necessary to disconnect both (Conductors ) and safeisolation may be able to be achieved by isolating the ( Line-conductor ) by means such as switching-OFF and locking-OFFthe appropriate-circuit-breaker … Appropriatecircuit-breaker providing the device is suitable for such Use .

P/150 - 537.2.1.1. Everycircuit shall be capable of being (Isolated ) from each of the line-supply-conductors. In a TN-S or TN-C-Ssystem, it is not necessary to isolate or switch the neutral-conductor where itis regarded as being reliably connected to Earth by a suitable-low-impedance .

Provision may be madefor isolation of a group of circuits by any common-means. If theservice-conditions allow this .

► P/150 . 537.2.1.2. Suitable means shall be provided to prevent anyequipment from being ( Inadvertently or Unintentionally Energized ) Etc

( Three-pole-Isolator ) which can be locked-OFF. Your Reason – Securing the means ofIsolation is thereby “ Simplified“

• Part of the Isolation-procedure is to (Verify that All Conductors are indeed dead )

• Inadvertently or Unintentionally switchedback-ON ( Locking-OFF )

Re-cap:Table 53.4 – P/149 Guidance on theselection of protective, isolation and switching devices . BS-7671:2011: have stated the Facts .

… Appropriate circuit-breaker providing the device is suitable for such Use .

Re-cap: P/405 - Isolationand Switching
WindowlessBathrooms:
Windowless bathroomsand toilets have to be fitted with a fan that includes a timer-circuit to ensurethe fan continues to run for a period after the light has been switched OFF

 

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“ Back tosome Basic’s “

BS-7671:2011: Must state the facts .

Re-cap . 17[SUP]th[/SUP] Edition requirements for ( Testing of RCDs)
p/193 - 612.8.1. following requirements in terms of ( Verification of installed RCDs )

612.8.1. requires the effectiveness of automatic-disconnection of supply by ( RCD ) ► To be Verified using , test-equipment meeting the requirements of BS-EN-61557-6 . ( refer ) GN-3 / p/81 . ◄

4.1 – Instrument-standard . ( Thebasic-instrument-safety-requirements )
BS-EN-61557-6 : Electrical-safety in low-voltage distribution-systems up to 1000V a.c .& 1500V d.c.
Equipment for testing , measuring or monitoringof protective measures , Residualcurrent devices – ( RCDs )

BS-7671:2011: Must state the facts ( Protective Measures ) Residual current devices – ( RCDs ) in:
p/193 . TN – Systems , TT – Systems , & IT– Systems .

This is to confirm that the relevantrequirements of . Chapter – 41 ( Protectionagainst electric-shock are Met ) p/49 :icon_bs: