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
 
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:




 
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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 .
 
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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 .

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

 
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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 4:DECLARATION . ( 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) .


 
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.

 
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.

 
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














 
2394: GN-3 . p47 ( is for Guidance )

Explain why it is necessary to verifypolarity . from -&-s

State the procedures for verifying polarity

Polarity testing .

Thepolarity of all circuits must be verified before connection to thesupply , with either an , ohmmeter or the continuity-range of an insulation and continuity-tester . Etc

Alternative, polarity can be verified byvisually-checking core-colours at terminations , thus verifying the installers-connections .Whatever-method is used , polarity-checks are required at all points on a circuit .

Instrument : Use a low-résistance-ohmmeter for these-test . Etc

Itis necessary to check that all fuses andsingle-pole-control and protective-devices are connected in the line-conductor . Thecentre-contact of screw-type-lampholders must be connected to the line-conductor - except E14 , & E27 to BS-EN-60238 .

Note : The continuity-test , Ring-continuity-test , may confirm polarity . Etc . Read up on GN-3 . :gettree:

 
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Understandingthe Inspection-process forelectrical-installations : ( You havewritten exams , Yeah ) 2394 .

Inspection: Visual-inspection of main-intake, consumer-units-connections or distribution-board , power-circuits , lighting-circuits , Etc .

• Understanding how to carry out testing and commissioning :

Instrument(s) : Low-résistance-ohmmeters , Insulation-résistance-testers , Earth-fault-loop-impedance-testers, Earth-electrode-résistance-testers , RCD - testers , Phase-rotation-instruments .

Earth-fault-loop-impedance-testers, GN-3 . p.83
These instruments may also offer additional-facilities for deriving-prospective-fault-current ,

Thebasic-measuring-principle isgenerally the same as for , Earth-fault-loop-impedance-testers, Etc

Approved-voltage-indicator, proving-unit , verifying-test-instruments , calibration-procedures , -&-s Use of documentary-evidence.

Statethe tests to be carried out on anelectrical installation in accordance with BS-7671: and IET Guidance Note 3
Identifythe appropriate-instrument for each test to be carried out in terms of :

• The instrument is fit for purpose
• Indentifying the correct scale or setting

GN-3 . Testing-instruments & equipment . p.81

p.82/ 84 .
Low-résistance-ohmmeters - BS-EN-61557-4 .
Insulation-résistance-testers- BS-EN-61557-2 .
Earth-fault-loop-impedance-testers- BS-EN-61557-3 .
Earth-electrode-résistance-testers-
RCD- testers - BS-EN-61557-6
Phase-rotation-instruments - BS-EN-61557-7.

 
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Inspection before Testing : “ Polarity “ :gettree:

A Visual-inspection shall be made to verify that theelectrical-installation / equipment as installed is correctly selected and erected in accordancewith BS-7671:2011:

( Written-exams )
 
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Statethe effects on insulation-résistance-values that the following can have : 2394:

Cables connected in parallel .
Variationsin cable-length .

Insulation-résistance shall not be lower than , 1.0MΩ for Low-voltage-installation under a test-voltage of , d.c.- 500V . as requested by Table - 61 - Etc.
 
Lengthof Cable :
Theinsulation - résistance of a length of a cable is the resultant of a number ofsmall leakage-paths , of a number ofsmall individual-leakage-paths , or résistance between the conductors and the cable sheath .

Theseleakage-paths are distributed along the cable . Hence , thelonger the cable , the greater the number of leakage-paths and thelower the insulation-résistance .
 
Basic principles when it comes to Insulation Résistance . 2394:

Résistance in , Series the formula is . Rt = R1 + R2 + R3 + R3 + R ……… résistance value will be Higher .

Résistance in , Parallel the formula is. Rt = 1/ ( 1/ R1 + 1/R2 + 1/R3 + 1/R ……… ) résistance value will be Lower . :gettree:

Where multiple-circuits are to be tested from the same-distribution-board , or consumer-unit , then the Overall-insulation-résistance can be calculated using the , Parallel formula . 612.3.2.
 
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Can anybody help me out here, I passed my 2391 a couple of years agoand am a time served JIB electrician, can I test and sing a condition report for a house I rent out as a legal document.
 
Bycalculations :

Measurementusing an earth-electrode-test-instrument .

GN-3. p.49 Typical-earth-electrode-test using a three or four-terminal-tester. ( three 3 rods )

Three readings are taken .

Example:

Three-measurementsare taken : 79Ω + 85Ω + 80Ω , = 244Ω

-&-s. these must be added together and an average value calculated . total-value of three readings = 244Ω , 244 / 3 = 81.33Ω .

Exercise .

Insulation résistance : Note . that ifthe live-conductors are joined and thentested to earth , insulation-résistance-value may be lower due to theconductors being in parallel .

Three-phase sub-main

L1 to earth is 130MΩ
L2 to earth is 80MΩ
L3 to earth is 50MΩ
N to earth is 100MΩ

Ifthese conductors were now joined and then tested to earth . 1/R[SUP]1[/SUP] + 1/R[SUP]2[/SUP] + 1/R[SUP]3 [/SUP]+ 1/R[SUP]4 [/SUP] + 1/Rt[SUP] [/SUP]( Rt - total )

Values: 1/30 + 1/50 + 1/100 + 1/0.05 = 19.92MΩ

Your calculator has button with [ 1/X ] 130 X-[SUP]1[/SUP] + 80 X-[SUP]1[/SUP] + 50 X-[SUP]1[/SUP] + 100 X-[SUP]1[/SUP] = X-[SUP]1[/SUP] is 19.92MΩ

Note . this value is still acceptable but lower because the conductors are in parallel .

 
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Testing:

Thetests indicated in Part - 6 .

Mustbe carried out in order given so that essential-safety-features are proven-first . 612.1 :gettree:
 
Insulation-résistance : Old working Example . “ How to “ 2392-10 . 2394

Between- poles insulation-résistance test onindividual-circuits on a installation .

Lighting - 250MΩ
Ring-final-circuit - 25MΩ
Water heater - 2MΩ
Cooker - 1MΩ
Radial-circuit - 1.14MΩ

Whatwould be the reading taken at the supply-terminals . ( 1/250 = 4. ) <

By calculation . 1/Rt = 1/250 + 1/25 + 1/2 + 1/1 + 1/1.14 . ( 1 ÷ 1.14 = 0.877 )

1/Rt = 0.004 + 0.04 + 0.5 + 0.877 : Rt - total , 1/Rt = 2.421 . therefore :- Rt 1/ 2.421 = 0.41MΩ . not acceptable . :carolers:

 
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