Re-take - Useful Information for 2394 :

[amberleaf]

Wherethe Question ask , “ explain with the aid of a diagram “ then a diagram & a written-explanation is required .

Q) Test-instrument used for working onelectrical-systems should . ?
a) be less than 10 years old .
b) Have non-insulated test-probes .
c) Have insulated test-probes .
c/ A ) To protect the user from electrical-shock ,whilst using the instrument . handling-probes.

Q) When is ( Live-working-permissible )
a) When the person-carrying out the work is a competent-person .
b) When it is unreasonable in all-circumstances for theequipment to be made dead & suitable precautions are taken .
c) When the means of isolation cannot be identified .
d) When the person working on the equipment is wearingrubber-gloves .
b/ A ) This is a requirement under , regulation - 14 , EAWR Regulations . However . it does not mean that , Live-working isthen “ Safe “

Chapter- 41 . Protection against Electric-shock .

Why . do we have , Additional-protection ?

Q) The lowest level of ,electrical-current which can harm thehuman-body is normally-measured in ?
Microamps .
Kiloamps .
Amps.
Milliamps.

Research . has shown that a person is in , serious-danger of afatal-electric-shock at . or approximately 30 - Milliamps . :gettree:

 

[B16 Tom]

Just got home from my 2394 online exam. All the qusetions seem to be on Insuation resistance and RCDs.
Ie Why do we use RCD protection for additional protection? Is it for <50v touch voltage? Is it for Ma protection? etc etc.....
how would you test a 100Ma RCD a)0.5x and 1x b)0.5x 1x 5x etc etc..... Testing for 300ma rcd cant rememver anymore?? if i can will post here.

 

[amberleaf]

Q). All electrical test probes and leads must complywith the standards set by the . ?
BS-EN-60898.
BS-7671:2011.
H&S Guidance note GS-38.
IET Regulations Part - 3 .

Q). For electrical test results to bevalid the test instruments used . ?
Mustbe new .
Mustbe of an approved type .
Must have a calibration certificate .
Musthave a digital readout .

Q). The test required by the IETRegulations to ascertain that the Circuit-protective-conductor is correctly connected is called . ?
Basicprotection .
Continuityof ring-final-circuit-conductors .
Continuityof protective-conductors . 612.2.1.
Earth-electrode-résistance.

Q) . The valueof a satisfactory-insulation-résistance-test on each final-circuit of a 230V installationmust be . ?
Less than 1Ω
Less than 0.5MΩ
Not less than 0.5MΩ
Not less than 1MΩ .. ( Table - 61 ) Up to and including 500V, ►►►► Minimum-insulation-résistance - 1.0MΩ . Circuit-nominal-voltage . ( V) -&-s . 100%

Q) . Instrument-calibration-certificate are usually valid for a period of . ?
3 months
12 months
3 years
18 months

Q) . What shouldbe given to the client when testingis completed . ? 632.1.
Original-test-documentation .
Copy of the drawings .
Technical advice on the use of equipment .
Designer’s- specifications .

Frequency of periodic-inspections , GN-3 . p.64 . table- 3.2. ( recommended-initial-frequenciesof inspection of electric-installations )
Q) . Aninstallation has been in use for , 10 years , Which test-procedures is most-appropriate. ?
Minor -works
Initial-verification
Periodic-inspection and testing .
Portable-appliance-testing .

Q) . What does not from part of test-documentation . ?
Electrical-installation-certificate ( EIC )
Schedule-test-results - (Generic )
Schedule of inspections - ( fornew-installation-work-only )
designer-specifications.

Q) What is not requirement during testing . ?
Costs are kept down .
No danger is caused to persons .
No danger is caused to livestock .
Avoiding damage to property .

Q) What is the displacement of the three-phases in , athree-phase-supply . ?
180 degrees
90 degrees
120 degrees - each with a Phase- displacement of 120° from each other . Electrical-degrees
45 degrees

 

[amberleaf]

B16 - Tom . Off to work now . will domy best to get back to you somewhere alongthe line . Read some of the posts .


To provide additional-protection against , electric-shock , an RCD musthave a rated-tripping-current of no more than 30mA .

RCD - Earth-fault-conditions . 0.04s . Not -0.4s
Constantly monitors the electric-current through on or more-circuits,it is used to protect . ( residual - current ) dual - current . line/ Neutral

30mA . 30 /1000 = 0.03A

50% . of 30mA ,15mA . the RCD . should not trip .
500%.of 30mA, the RCD . should trip in under 40mS


Calculations for determining touch-voltage is( Ze ) the rated ( mA ) of an RCD . RCD - 100mA ?
TT - system . 200Ω , 200Ω x 100mA ÷ 1000 =20V

Touch-voltage .
50V / 0.03A = 1666.6666 . 1667Ω
50V / 0.1A = 500Ω


RCD- Testers .

GN-3.84
i).Should be capable of supplying full-range oftest-currents . 50% . 100% . 500%. - ½ . x1 . 5 x .
ii).-&-s . Test -current should be applied for . no-longer than . 2 seconds .RCD - Only
iii).Instrument to . BS-EN-61557-6 . willsatisfy the above .

Re-cap.GN-3. p.58
Operation of . residual-current-device . ( Big time -&-s )
411.4.5.
For each of the tests . readings should be taken on . both positive & negative . half-cycles and the. longer-operating-time-recorded.

 

[amberleaf]

AdditionalProtection :

Is the , Presence of residual-current-device .

Theinspector should check that AdditionalProtection has been provided by a residual-current-device . RCD having the operating-characteristics .Section - 415 .

Regulation- 411.3.3.

Socket-outletswith a rated-current not exceeding 20A that are intended for , general-use byordinary-persons .
Mobile-equipment with a current-rating not exceeding 32A for use outdoors .

Insulation-Résistance between-Live-conductors & Earth .

Table- 61 . the Minimum-acceptable-value for a 400 / 230V installation , ( ≥ 1.0MΩ )

Regulations have to statedthe facts , Table - 61 . Up to & including 500V , ( ≥ 1.0MΩ )


How do you test a 100mA - RCD . ? . Megger- 1552. 3 x - setting , ½ . x1 . 5x , let narrowit down , ( 50% / 500% - is for Additional Protection - 30mA)

( ½ /50% ) 15 - half of 30mA . No-trip.
x5 - 500% . 30mA - 40mS . will -Trip

leavesus , x1 . 100% - BS-EN-61009-1 . 100mA - 100% , 300mS . Hint ! You do not test ( 5x times rating ) 100mA

Note : BS- only , 200mS
Note : BS-EN only , 300mS

P.295- Regulations have to statedthe facts , Table - 3A - time/current performance-criteria for RCDs , to BS-EN-61008-1 & BS-EN-61009-1
( Right if we screw it UP . 5x 100mA is 500mA , to much to inject into theinstallation ) this is what -&-s are looking for . Will you **** it Up . ! impairing-safety. You do not do this . :17:

Watch your Questions here , RCDs !! . ( G ) or ( S - type) delayed type

2 x , testing required of RCDs . 30mA , 50% & / 500% ( G ) General-purpose RCD .

BS-7671:2011: recognizes ( 2 xtypes ) of protective-devices for disconnection of the circuit is required in a , ( TT ) system under-fault-conditions .

An - RCD .
An Overcurrent-protective-device . Circuit-breaker.

415.2.The use of RCD , is not recognized as asole-means of protection and does not ,obviate the need to apply , one of the protective-measures Etc

Wherean RCD is used for , ( Earth ) fault-protection , Regulation - 411.5.3. requires the following condition to be fulfilled :
0.2s ) maximum-disconnection-time for a.c. final-circuits not exceeding 32A .

Under, ( Earth ) fault-conditions the RCD will take it out , 0.04s Lessthan , 0.2s . whilst the circuit-breakerthinks about it . the RCD has used its Presences .

By-calculations : Maximum-prospective-short-circuit-current , Line to Neutral , 230V / 0.05Ω = 4600A , 4.6kA ( PSCC )

An RCD : provides protection against , earth-faults occurring in equipment & reduces theeffect of Electric-shock . Etc


Must dash to work . 14:20 . in & out

 

[brucelee]

Hi tom

this thread is for information only i believe and your questions would be better posted in the section for inspection and testing were they will be answered more quickly

In regard to your question regarding 100mA RCDs
100mA RCDs are not used for additional protection so when testing
test at 1/2 I delta n (50mA) on both half cyles of the waveform the device should not trip then
test at 1 x i delta n (100mA) on bth half cycles device should trip in 300ms if BSEN 61008 record the highest reading
do not test at 5x as the device is not used for additional protection neither is a 300mA or 500mA

so you answer would have Been (a) there is loads of this info in this thread and others on the forum use the search bar at the top

where an RCD with a rated residual operatng current I delta n not exceeding 30mA is used to provide additional protection (against direct contact) with a test current of 5 x I delta n the device should open in less than 40ms

where loop impedence values cannot be met RCDs of an appropriate rating can be installed there rating can be determined from
I delta n = 50/Zs

I delta n is the rated operating current of the device
50 is the touch voltage and Zs the measured earth fault loop impedence

the accepted lethal level of sock current is 50mA and hence RCDs rated at 30mA or less would be appropraiteforuse where shock is increased risk
30mA are used for
. All socket outlets rated at no more than 20A and for unsupervised general use
. Mobile equpment rated at not more than 32A for use outdoors
. all circuits in a bath /shower room
. Preferred for al circuits in a TT installation
. All cables installed less than 50mm from surface of a wall or partiition (in safe zones) if the instalation is unsupervised , and also at any depth if the construction of the wall or partition includes metallic parts
. in zones 0, 1 and 2 of swimming pool locations
. All circuits in a location containing saunas
. socket outlet final circuits not exceeding 32A in agricultural locations
. circuits supplying class 11 equipment in restrictive conductive locations
. each socket outlet in caravan parks and marinas and final circuits for houseboats
. al socket outlets rated at no more than 32A for show stands etc
. All socket outlet circuits rated at no more than 32A for construction sites ( where reduced low voltage is not used )
. All socket outlets supplying equipment outside mobile or transportable units
. All circuits in caravans
. All circuits in circuses
. A circuit supplying class II heating equipment for floor and ceiling heating systems

 

[amberleaf]

2394: are getting pounded with Questions about RCDs . backto Basics


The Whys . RCD - Testing . ◄◄

▲▲ The . Trip-current can be affected by the direction of the , test-current , So tests must be carried-out for both-half-cycles . test-current .

- positive-half-cycle . ≈ 0°
- negative-half-cycle . ≈ 180°


Additional protection : ( Plain - English )

isto limit the current and time that the fault can pass through the body . ◄◄

Touch-voltage. by calculation . 50V / 30mA = 1666.

5 x test ) only for protective-devices. Used to provide - Additional protection ( 30mA) : “ 500% x “

General-purpose- Non-delayed RCD - ( G )


Note RCDs : Greater of the two-trip-times for record-purposes .


Thanks Bruce . Waterdamage . big time . this is the only job there handing out . head &shoulders shampoo . Client . Can you save the lighting . !!!!!! :svengo:

 

[amberleaf]

Regulations have stated the Facts .

Requirementsfor ( Testing of ) RCDs :

The17[SUP]th[/SUP] Edition has thefollowing-requirements in terms of ( Verification ) of installed RCDs .

612.8.1. requires the ( Effectiveness) of automatic - disconnection of supply by RCD tobe ( Verified) using test-equipment meeting the requirements of BS-EN-61557-6 , This is to confirm that therelevant-requirements of , Chapter - 41 . Protection against electric-shock . are Met .

 

[amberleaf]

The ( x5times ) current is onlyrequirement for 30mA - RCD , used foraddition-protection ( tripping-time - 40mS )
x5 Test , is N/A for anything bigger than 30mA . 2394: exams

RCD- testers , have a built-in-function that limits the voltage that the tester can raise the earth by , 50V or less . :gettree:

100mA- tripping times . x1 - 300mS

Fault-protection . 2392-10 Basics .

Overcurrent-protection-devices, like circuit-breakers to act promptly on small earth-leakage -currents , tocomply with regulations , the earth-fault-loop-impedance in ohms . multiplied by therated-tripping-current of the RCD in amperes must not exceed 50V.

Foran RCD with a rated-current of 30mA . the maximum-permissible-earth-fault-loop-impedance is calculated as follows ( Table - 41.5 )
Zs - maximum = 50 / In = 50 ÷ 0.03A = 1666Ω .

 

[amberleaf]

In ) Rated-current of the contacts . Expressed in amperes . 100A .
IΔn ) Sensitivity . or residual-operating-current . Usuallyexpressed in amperes . 0.03A / 30mA

 

[amberleaf]

300mA. Fire - protection. against the , initiation of Fire . protection - Degree of protection .

Againstfire : Basics .
Majorityof fires which occur as a result of faulty-wiring , are started by current flowing to earth , Fire can be started by fault-current of less than , 1 - amp .
Overload-protective-devices, such as a circuit-breaker will not detect such a small-current , RCD will detect this fault-current &interrupt the supply ,

 

[amberleaf]

Accessory : Sockets ,Switches , Ceiling-roses . Lighting. Etc .

(MEIWC )
( Certificate ) may be used for the replacement of equipment such as , Accessories or luminaires.
( Certificate ) include the Addition of : Socket-outlets .
( Certificate ) or Lighting-pointsto an Existing-circuit . therelocation of a light-switch .

Electrical-installation-certificate, ( EIC ) A Safety-certificate . on completion . Once you sign off the certificate , you are taking responsibility for that installation :gettree:

New-installation .
Or changes to an ( Existing-installation)

Thecertificate - confirms that the installation has been :
Designed.
Constructed.

Inspected & Tested . of the work described on the certificate .

PART 4ECLARATION . ( MEIWC )

I / We CERTIFY that the works do not impair the safety of the existinginstallation, that thesaid works have been designed, constructed, inspected and tested in accordancewith BS 7671:2008 (IET Wiring Regulations), amended to .................................. (date) andthat the said works, to the best of my / our knowledge and belief, at the time of my / our inspection compliedwith BS 7671 except as detailed in Part 1 above.

Comments on existing installation, includingadequacy of earthing and bonding arrangements (see 132.16)

( MEIWC ) is a certificate of compliance and good - workmanship . by far the easiest way of demonstrating -compliance . BS-7671:2011:

Regulation- 633.1. & 633.2. refer to all alterations and additions , supported by the appropriate-certification.

2394: This can be in the form of , either , Minor-works-certificate(s) or Electrical-installation-certificate(s) .

 

[amberleaf]

Certification & Reporting

p.390- Electrical Installation Certificate - ( EIC )
Q). if when installing aNew-Consumer-Unit . On the ( EIC ) Certificate , Whichdo you Tick . ? :gettree:

Descriptionand Extent of the installation .
New-installation . □
Addition to an existing-installation . □
Alteration to an existing-installation . □

□ If New- Build / Installation or a complete re-wire was conducted . Tick - New-installation.

□ An Addition : this box should be ticked is an existing installation has been modifiedby the addition of on or more new circuits .

□ Replacementof Consumer-Unit , and reconnection of existingcircuits . Tick - Alteration . - Altered the installation.

 

[amberleaf]

16[SUP]th[/SUP] Edition , Blastfrom the Past .

Insulation - résistance . ( 713-04-01 )
The insulation-résistance between Live-conductors andbetween each live-conductor and Earth shall be measuredbefore the installation is connected tothe supply .
The PEN - conductor in , TN-C systems shall be considered as part of the earth , Where appropriate during this measurement , Line & Neutral-conductors may beconnected together .

Understanding the relationship between the Two-Issues . 17[SUP]th[/SUP]Edition / 2008 / 2011:

612.3.1. Insulation - Résistance. 713-04-01.
Theinsulation-résistance shall be measured between live-conductors and betweenlive-conductors and the , protective-conductor connected to the earthing-arrangements , Where appropriate during this measurement , Line & Neutral-conductors may beconnected together .

612.3.2. the Insulation - Résistance-measured with thetest-voltages indicated in , Table - 61. shall be considered satisfactory if themain-switchboard and each-distribution-circuit-tested-separately .withall its final-circuits-connected butwith current-using-equipment-disconnected . has an insulation-résistance not less than the appropriate-value given in Table - 61 .

713-04-02 .
the Insulation - Résistance-measured with thetest-voltages indicated in , Table - 71A is 61. shall be considered satisfactory if themain-switchboard and each-distribution-circuit-tested-separately .withall its final-circuits-connected butwith current-using-equipment-disconnected . has an insulation-résistance not less than the appropriate-value given in Table - 71A is 61 .

Contraryto popular believes . Insulation-résistance-tests required by 612.3. are whole-installation . or , at the least , large-section tests .
Single-circuit-testing , has always been in 612.3.1.

 

[amberleaf]

My mate at the collage , has informedme that . A lot of people are on the understand , a quick fix will save there bacon . Q /As , 2392-10 & 2394 . Etc .

Thefundamental - principles . are at the basic - levels . Understanding first .

BS-7671:2011: States the facts .
GN-3. Guidance . Tells us how-to .
O.S.G. Guidance . Simplicity .

:rant:


2392-10: Q) - Do we test the ( Ze ) at the Origin . or dowe take pot-luck that there in an , Earthing-conductor . Verification.

The complete Earthing-Arrangement of any installation . Has a knock on affect . Protection against Electric-shock . Ief

Before connection of the supply :

Visual Inspection
Continuity of (circuit-protective-conductors ) & Earthing-conductors . ( Have we confirmed we have an Earth ) Continuity


Visual Inspection
Continuity of thering-final-circuits . Three-steps to be taken . ( Have we confirmed we have an Earth ) Continuity

With the supply connected :

Earth-loop-impedance-test, to determine the Quality of your Earthing . ◄◄◄◄◄◄ 612.9

That’swhy the Regulations , have it in a certain-order . for Testing . Verification

Testingof RCDs to check that they do trip at the, correct-time , & current-rating . ( Longbefore this you have confirmed you have Earthing ) 612.10.


Scenario: 612.8.1. for your Exams . Back toBasics . 2394: TN - system . p.193

Compliance with Regulation - 411.4. , The regulations must state the facts . ( Have we confirmed we have an Earth )

1) measurement of the earth-fault-loop-impedance . ETC .

2) verification: of the characteristics and / or the effectiveness of the associated ( Protective-devices )

Circuit-loop-impedance . ( Zs ) or (Ze ) that part of the ,earth-fault-loop-impedance which is external to the installation . ( Have we confirmed we have an Earth )

( Protective-devices ) Overcurrent-protective-devices . Visual Inspection . Etc .
( Protective-devices ) for RCDs , Visual Inspection , and Test .

Q) what comes first .. Verification of Earthing .

(Ze ) at the Origin 313.1. Earthing-conductor . Verification.
Earth-loop-impedance-test, to determine the Qualityof your Earthing 612.9. ( Circuit-loop-impedance ) RCD relies on Earth-fault-protection .

Testingof RCDs to check that they do trip at the, correct-time , & current-rating .612.10.

RCD relies on any fault to Earth . as a primary-means of providing-protection against Electrocution. ( Earth-fault-protection ) That’s why!! , we confirm we have an Earth , First