***Cont../ Useful Information for Electricians & Apprentices***

[amberleaf]

O.S.G.. The use of other methods’ of determining Maximum Demand is Not Precludedwhere Specified by the Installation Designer

FirstlyI make no Apologies for the Way am Writing on any Matters . it can be a first day Apprentice or some one Needing aJog of Memory .
Sowe are all in the Same Boat . “ To Learn “

For the Apprentices . The Day we stop learning is the Day we hang Upour Tool-Bag

CookerDesign Current Calculations

Thefirst thing you have to do is get Your Head around the Calculations !!

(From a Design point of View ) 2392-10

DomesticInstallation Oven(s) & Hob(s) are to be Calculated upon their MAXIMUM LOADING
Startwith a simple Calculation ( An Oven has a rating of 2kW ) 2000

(I = P/V ) Formula … I = 2000 ÷ 230V = 8.70A …. Weare Using the Unit Amps


2392-10/ Domestic Installation Oven(s)

Ovenhas 4 Rings ( 2 x 1kW ) & ( 2 x 1.5kW ) & Grill ( 2kW ) & Oven (3kW )

-Controlled via a CookerSwitch with a Socket outlet .

Asa Designer . we’ll have to Apply Diversity ??

Important )- Diversity allowance to be Applied to the FULL LOAD CURRENT for CookingAppliances .

TheO.S.G. is telling us . Purpose of the Final Circuit fed from theConductors )
O.S.G.Table 1B p/97 – column (3) Cooking Appliances → At the Top of the Page Note : Type ofPremises ( 2392-10 → Household Installations ) Domestic Installation(s)

DomesticInstallation(s) Only O.S.G. - 10A + 30% f.l – Full Load ) of connected Cooking Appliances in the Excess of 10A+ 5A if a socket-outlet is incorporated in the Control Unit . ( C.C.U. ) – 45A + 13A Socket Switched with Neon .

Fromyour point of View ( The First 10A ofthe rated current plus 30% of the reminder ( Plus) 5A if the Control Unit incorporates s Socket.

Calculations)- You bank “ Hold OFF“ the first 10 Amps of the Maximum Load Current )
The10A will be used at the End of the Calculations’

-So your Work out the Total Power Rating & then calculate the Full Load Current

Calculations)- Power = ( 2 x 1 ) + ( 2 x 1.5 ) + ( 2+ 3 ) = 10kW

I= 10000 ÷ 230V = 43.48A … round it up to the first four numbers43.47826087 ( 48 ) 43.48A

UsingDiversity allowance stated ↑↑ ( 43.48A sub 10A = 33.48A )

I= 33.48 x 30 ÷ 100 = 10.04A

Youradding the ( 5A ) for Socket outlet . I = 10A + 10.04 + 5A = 25.04A )- Asa Designer this is your Expected Current Demand .

Remember )- Supply Cables Rated to suit DesignCurrent ( Iz )

 

[amberleaf]

Scenario Only . This isonly an Example on the Wording that canbe Used :svengo:

-&-s. Section A . 2391-10 . :hurray:

Electricalinstallations require Inspection & Testing throughout their working life .

State( Three ) separate occasions when Inspection& Testing must be undertaken . Excluding Periodic Inspection .

New installations . additional work . alterations . minor works.

State( Three ) items of information that are required by a person undertaking the Inspection & Test ofan installation . Excluding information containedon diagrams . charts . or tables .

Maximum demand in amperes . number & type of live conductors. type of Earthing arrangement . thenominal voltage & frequency . prospective fault current & ( Ze ) external earth fault loop impedance . type& rating of the protective device .

State: the legal status for each of the following documents .

i)GS-38 / Non- statutory .
ii)GN-3 / Non- statutory .
iii)BS-7671 / Non- statutory .

State: Three different practical situations that may require the use of the sense oftouch during the Inspection process.

Feel for excessive heat from circuit breaker(s) or PVC/PVC .cable .
Feel for loose bolts connecting sections of cable trays .
Feel exposed bonding cable & clamps for ( Tightness )

List: Three items to be checked . as identified on the Schedule of Inspections .where fault protection is provided by automatic disconnection of supply ( ADS )

Check for presence of main bonding .
Earthing . circuit protective conductors .
choice & setting of protective devices .

 

[amberleaf]

State: Three requirements for test probes & / or lead as required by GN-38 . (2391-10 & 2392-10 here ) :hurray:

No more than 4mm exposed tip of probe 2mm – preferred .
Finger guards .
Fused test probe .
Leads long enough foe ( Safe Use ) leads in good order – No obviousdamage .

State: the correct instrument for conducting EACH ofthe following tests .

Continuity of the ring final circuit(s) – Low résistanceohmmeter . ( Ω )
External earth fault loop impedance on a ( TN ) system . Earth fault loop impedance tester .
Earth electrode résistance for a ( Generator installation ) . Earth electrode résistance tester .

Satewhy – for safety reasons .

a)Inspection must take place before testing (- Hazards such asexposed live parts . dangerous methods of erection & unexpected & dangerousenvironmental conditions .

b)BS-7671 identifies a sequence of tests tobe followed before the installation is Energised (- ifprotective conductor continuity is not confirmed then because this could be abreak or a loose connection there would be no point in insulation testing asthis would not go beyond the break

c)The installation polarity is checked when the supply is connected for the firsttime (- The supplier polarity could be reversed orthe electrician may incorrectly connect the tails ( in Reverse ) :svengo:

 

[amberleaf]

Statein the correct sequence the first FIVE teststhat would need to be undertaken on an ( A1 )Ring Final Circuit – during Initial Verification . :hurray:

GN-3 / p33 – 2.7.4.

i)Continuity of the protective conductors .
ii)Continuity of ring final circuit conductors .
iii)Insulation résistance .
iv)Polarity
v)Earth fault loop Impedance ( Zs )

Atthis point 2392-10 . You should get the book – GN-3 :bulb2:

( A1 ) O.S.G. – P/158

 

[amberleaf]

Rectification .

Apprentices. in the Regulation . Dead Testing

612.2.
612.2.1.
612.2.2.
612.3.
612.6 . By continuity methods

Testprior to the installation being Energised .

Sorryabout that my eyes get tired at thistime off night . Amber . ◄◄ :20:

Only when in Use . TT System .Earth electrode résistance . 612.7. ??

 

[amberleaf]

Part1

Important Announcement “ 2392-10 “ :46:
Goingfor your 2391-10 . is not a walk in the Park . It is not a Multi – Questions Testhere . I will Tax your Brain .

Mypoint of View here “ Amber “ . Getting a( Quick Fix ) does not help ( You ) in anyway to this Exam . 2391-10 .You have toStudy –BS-7671 / GN-3 :46:
Knowit inside OUT .

Whatis in a ( Question ??????? ) To many ( Implications ??????? ) jumpingover the garden wall . doesn’t mean it’s the shortest way .

State:

Two Test Methods to verify the continuity of the Protective Conductors . ( Question ) ◄◄
(- O.S.G. – p/80 . Three-steps Continuity of the Ring FinalCircuit Conductors . GN-3 – p36 .

Thisis a Quick Fix . ( Answers ) :20:
Method 1 (- Connect the Line ( R1to the CPC R2 at the distribution board ) measure résistance at the End of the circuit between( R1 & R2 ).
Method 2 (- Wander Lead method . ( R2 ) A → to → B . No breaks in cable / & theCable is Single . No / Parallel Paths .??

-&-sasked the ( Question ) Test Instrument to be Used to Conduct thisTest (- Low-Résistance Ohmmeter ) The correct Wording at all times . -&-s

Instrument(- Use a low-RésistanceOhmmeter for these tests – p/82 – 4.3. low-Résistance Ohmmeter

GN-3. The instrument used for low-Résistance Test may be either a Specialised low-Résistance Ohmmeter . or
TheContinuity range of an ( Insulation & Continuity Tester )◄◄ Wording . All in One Tester .

612.2.1 .
Thetest current may be ( D.C. or A.C. ) it is recommendedthat it be derived from a source with No-load voltage between ( 4V & 24V ) & ashort-circuit current not less than ( 200mA )

Instrumentsto ( BS-EN 61557- 4 ) will meet the above requirements .

 

[amberleaf]

Part2

SomeImplications . to Think about . Yeah :46:

Anyonecan make a mistake . even the most experienced of electricians . For this reason. all ( ElectricalInstallations ) alterations & additions should be Tested . Inspected& subsequently Certified ( Prior to handing over tothe Client for Use )

AsI have Explained this matter before . Reasons .
TheCertificate issued describes the ( Current Operating Parameters ) & will provide thebasis for any future alterations & additions to the Installation .

For-&-s point of View. You are giving a AccurateRepresentation of the Installation .
For-&-s point of View. The Test Instrument must . must be Accurate . (must be consistent )

 

[amberleaf]

Part3 .

Asa “ Inspector “

Thestart of your . Fundamental Principles . Requirements made in the Regulations . :hurray: :20:

BS-7671.Requires that every installation shall be ( Inspected &Tested ) to verify that the regulations havebeen met before being ( Put into Service ) following Regulations.

( T ) 134.2. Initial Verification. 134.2.1.
Duringerection & on completion of an Installation or an Addition or Alteration toan Installation . & before it is ( Put into Service) appropriate ( Inspection & Testing ) shall be carried out by ( Competent Persons ) to verify that the requirements of thisStandard have been MET .

( T ) 610. Initial Verification. 610.1.
EveryInstallation shall . during erection & on completion before being ( Put into Service ) be ( Inspected& Tested ) to verify . So far as isreasonably practicable . that the requirements of the regulations have been MET .

Precautionsshall be taken to avoid danger to persons & to avoid damage to property& installed equipment during ( Inspection & Testing )

( T ) 612. Testing . 612.1 InitialVerification .
Thetest of Regulations ( 612.2. to 612.13 )

612.2.1. – Continuity of the Protective Conductors’ ( Electrical Installations ) alterations & additionsshould be Tested . Inspected & subsequently Certified ( Prior to handing over to the Client for Use )

YourCertification . is your Compliance with Electricity at Work Regulation 1998 . ( ElectricalInstallations ) alterations & additions should be Tested . Inspected& subsequently Certified ( Prior to handing over tothe Client for Use )

Itis important that Electricians are not just able to ( Construct) They should also be able to ( Recognise ) Faults & take action .

-&-s. They are Asking the ( Big / Question ) Describe how to carry out ( CommonTests ) Soyou have to think like a Tester . at all times .
-&-s. Will be asking NEXT . Explain the NEED to comply with Test Values .

Itis Under Fault Conditions that Lives & Propertywill be at RISK . That’s why . BS-7671 Harp ON .

OldAmber is off on One AGAIN .

 

[amberleaf]

Am Sorry about the Break in the Forum . am having Problems with downloading . ◄◄◄

Iwill get Phil to down load something for me . tosee if its my Computer . ◄◄◄ :46: Amber

 

[amberleaf]

UsefulJunk .

BS-7671:2008.

Requiresthat the InstrumentsUsed for measuring Insulation Résistance mustbe capable of providing the Test Voltages stated

TestCurrent of ( 1mA ) instruments that are maintaining to ( BS-EN 61557) will satisfy the requirements ◄◄ What’s in a Number. Not a Multi/ Tester

It is Important that we read the Questions Carefully . -&- .We are all bad for not Look right . Yeah :46:

Insulation – Résistance . Ohmmeters .

Apprentices / Insulation Résistanceshould have a High Value & therefore InsulationRésistance Meters must have the Ability to Measure HighRésistance Readings .
TheTest Voltage - then you go to Table 61 . p/158

Apprentices / ( MΩ )

 

[amberleaf]

Every Cable has Résistance . :38:

Thisone always comes around . One way or Another.

State: the effect EACH of the following would have onthe measured résistance of a conductor .

Increasein length – Increase résistance .
Decreaseis CSA - Increase résistance .
Increasein temperature - Increase résistance .

2392-10. you will get this in Exams .

A Prospective Fault Current Test . is to be carried out on a Single-phase electricalinstallation . STATE .

a)The two Tests which are to be Undertake .

Testbetween the ( Line ) & ( Neutral ) for the maximum ( PSCC )

&between the ( Line & ( Earth ) for the Maximum ( PEFC)

b)Which value from ( a ) above will be Recorded asthe ( PFC ) The highest value above . ◄

the Highest Readingsfrom the Two Test . One or the Other .

Apprentices. if we look at BS-7671 . 612.11 ( Live Test ) ≈

Itwill tell you ( PFC) firstly . BUT they are TwoTests to perform . ≈

i) Prospective Short Circuit Current (- ( PSCC) Line &Neutral .

ii)Prospective EarthFault Current (- ( PEFC ) Line & Earth

2392-10 . ifyou have Measured . you do not need to Calculate. :dots: Yeah

Apprentices. . if we look at Regulations p/341 .

Certification& Reporting - Schedule of Test Results . ( PFC– kA ) :icon_bs:

ii)Prospective EarthFault Current (- ( PEFC ) Line & Earth . Example .
Typeof Supply . TN-S / TN-C-S / TT .
YourEarth External to the Installation - ( Ze ) ( PEFC ) Line & Earth .

Apprentices. With this Test . You are looking for Parallel Path(s) . Yeah Earthing . ◄ ≈ :mad2:

 

[amberleaf]

TTSystem . 2392-10 . Learning Curve . to becoming 2391-10. Q/As to be Had Here . ????? :earmuffs:

Iwill bring this to your Attention . the Importance of GN-3 ◄ :speechless:

AnEarth Electrode Resistance Test .
Isto be carried out using an EarthElectrode Resistance Tester . 2392-10 ( is it D.C. or A.C. ? )
Statethe recommended . ?? ( You want to belooking in GN-3 – p/46 / 47 )

a)Soil conditions during testing . GN-3 p/46 . Attheir driest . ( To Record highest Résistance ) ………….. GN-3 / During Dry Weather .
Regulations .542.2.2.
Thetype & embedded depth of an Earth Electrode shallbe such that Soil drying & freezing will not ( Increase) its résistance above the required value .

b)Distance between an Earth Electrode which is (3m in Length ) & the furthest Test Spike .GN-3 . P/46 . ( 30m)
c)Minimum number of Test Readings required . 3 readings &record the average . Fig – 2.6 / 3 xSpikes .

GN-3 . gives Solutions.

Oneway . ? p/47 . if the temporary spike résistance is too high . measures toreduce the résistance will be necessary , such as driving the spike(s) deeperinto the ground .

TestMethod 1 . Before this Test is Undertaken . the EarthingConductor to the EarthElectrode mustbe Disconnected either at Electrode or at the MainEarthing Terminal
Toensure that all the Test Current passes throughthe Earth Electrode ALONE.

-&-s. Switch OFFSupply before Disconnecting the Earth .
-&-s. AFTER completion of Testing ensure that the Earthing Conductor is Reconnected.

So. A Quick Fix to Answers are not Enough . Yeah .

Earth Electrode Résistance . Transformer ? Generator ? Test Method 1 BS7671 – Mobile or Transportable Units . Example

P47– GN-3 . Earth Electrode for RCDs . ( Questionsyou have to ask yourself ????????? ) Not a Quick Fix toAnswers . Only

Earth Electrode for RCDs
Ifthe Electrode under Testis being used in conjunction with a residual current device the followingmethod of Test may ( Be Applied ) as an (Alternative to the EarthElectrode Résistance Test )

Getyour GN-3 Book . Solutions :speechless:

Wherethe Electrical Résistance to Earth are ( Relatively High& Precision is Not Required )

AnEarth Fault Loop Impedance Tester may be USED . ETC

GN-3 – ( Alternative for RCD protected TT /Installation ) Method2 . p/48

2392-10. A Loop Impedance Tester .is connected between the Lineconductor at the SOURCE of the TT /Installation & the Earth Electrode .

From-&-s point of View . The Impedance Reading taken is Treated as the Electrode Résistance .

AsGN-3 rightly put it . / Values above 200Ωmay not be stable . as Soil Conditions Changedue to FACTORS such as Soildrying & freezing .
:angelsad2:

 

[amberleaf]

Test Method 1 :

Uses the Line as areturn Lead . Otherwise known as . ( R1 + R2 ) Method

Most Common Method usedfor ( Final Circuit(s) …. Point to Note . Wording( Final Circuit(s) / Radial(s) / RingFinal Circuit
Line conductorruns alongside a Protective conductor .

Instrument to be Used . ( Low-résistance-ohmmeter )

Some Wording for -&-s . ( Low-résistance-ohmmeteris then connected at the Most / FurthestPoint of the Circuit . & a Readingis Obtained )
This Readingof the Line Conductor & the Protective Conductor & is given the Name ( R1 + R2 )

Sate : The scale to be Used . ( Ω )

Record ( R1 + R2 ) on the Schedule of Test Results .

Advantages ( R1 + R2 ) readings can be used forworking out Our Earth Fault Loop Impedance Value ( Ω ) . ifwe decided NOT to measure it .
Advantages ( R1 + R2 ) Polarityof the circuit is also Obtained at the Same Time

Advantages ( R1 + R2 ) Polarity( By Continuity Methods ) :rockon:

 

[amberleaf]

Useful Junk .

“ Earth Résistance “is the Résistance of soil to the passage of Electrical Current .

“ Earth “ is arelatively poor conductor of Electricity compared to Normal Conductor(s) likeCopper . :dots:

Practical “ Earth Electrode“ that provides a ( Low-Earth-Résistance )is not always easy to Obtain .

State : When you find that your Earth Electrode resistance is NOT Low-enough . there are several ways you can improveit .
State : Two methods .

•lengthen the Earth Electrode in the Earth .
• Use multipleRods .

( R ) Résistance ( a ) is the cross-sectional-area of the path … (Ra ) . PS. This is my Own Conclusions . Amber . :icon_bs:

17[SUP]th[/SUP] Edition .

( Ra ) is the SUM of therésistance of the Earth Electrode & the Protective Conductor connecting it to the ( Exposed-conductive-parts) in Ohms .

 

[amberleaf]

Two Methods are given in IEE Guidance Note 3 …. ( TT Systems )

Inspection & Testing for measuring the ( Résistance of Installation Earth Electrodes )

Test Method 1 . Before thisTest is Undertaken . the Earthing Conductor to the Earth Electrodemustbe Disconnected either at Electrode or at the Main Earthing Terminal
Toensure that all the Test Current passes through the Earth Electrode ALONE.

Test Method 1 :

Which ( ONLY ) the ( Résistance ) of the Electrode & the Earthingconductor connected to it are Measured .

Used where a ( High Level ofAccuracy ) & where Low Valuesof Electrode Résistance to Earth are Required .

Test Method 1 :

Involves the Use of a ( ProprietaryTest Instrument )
Regard to Electrode TestInstruments . ?? Proprietary make of Instrument with a ( Three or Four) Terminal arrangement should be used in order that the résistance of the Test leads& Test Electrode may be Evaluated . ( D.C. ) batteries or rechargeable .

How to Remember (- TT Systems - Test Method 1: ←→ ( Résistance ) :6: :willy_nilly:

 

[amberleaf]

Two Methods are given in IEE Guidance Note 3 …. ( TT Systems )

How to Remember (- Test Method 2: ←→ ( Impedance ) :6: :willy_nilly:

Test Method 2 :

Which the ( Impedance )of the ( Whole Earth Fault Current Part is Measured )

& is taken to be the ( Résistanceof the Electrodes ) This Method is Used. ( High Level of Accuracy is NOT StrictlyRequired ) ◄◄ :6:

Test Method 2 : ▼▼▼
Involves the use of a ( EarthLoop Impedance Tester ) GN-3