M
Marvo
It's listed in the sticky that highlights the important threads.
A
amberleaf
Useful Junk .
Extracts
Electrical Enclosures Outdoors
The likelihood of water penetration must be carefully assessed
Presence of water . Etc
P/123 . Regulation 522.3.1
A wiring system shall be selected and erected so that no damage is caused by condensation or ingress of water during installation, use and maintenance.
P/123 . Regulation 522.3.2
Extracts
Electrical Enclosures Outdoors
The likelihood of water penetration must be carefully assessed
Presence of water . Etc
P/123 . Regulation 522.3.1
A wiring system shall be selected and erected so that no damage is caused by condensation or ingress of water during installation, use and maintenance.
P/123 . Regulation 522.3.2
A
amberleaf
sorry about that cut off
P/123 . Regulation 522.3.2
Where water may collect or condensation may form in a wiring system provision shall be made for its harmless escape through suitably located drainage points.
P/123 . Regulation 522.3.2
Where water may collect or condensation may form in a wiring system provision shall be made for its harmless escape through suitably located drainage points.
A
amberleaf
Extracts .
It is worth considering Section 710 in relation to veterinary surgeries if there are concerns over animal welfare during surgery
Veterinary practise
BS 7671 Regulation 411.3.3 sets out the requirements for additional protection to socket outlets for use indoors. There are exceptions depending upon the level of supervision, and also for socket outlets that are provided for a specific item of equipment - as opposed to those for general use.
If there are concerns over the welfare of animals in the event of a trip, then dedicated circuits for this equipment could be considered, ensuring that the outlet is identified to the equipment it has been designed to serve (exception (b) of 411.3.3.).
Any outlets intended for general purpose use by ordinary persons should be additionally protected at 30mA by an RCD, unless the use of them is effectively supervised. The question of supervision should be discussed with the practice management to establish whether any such supervision is achievable and sustainable.
The same discussion should also include any supervision required by Regulation 522.6.101 with reference to cables concealed in walls and partitions, as a consumer unit replacement is effectively an alteration as defined by BS 7671 and hence the requirements of 522.6.101 should be considered.
P/230 . Worth considering Section 710 in relation to veterinary surgeries if there are concerns over animal welfare during surgery
( Note 2 to Regulation 710.1 ).
It is worth considering Section 710 in relation to veterinary surgeries if there are concerns over animal welfare during surgery
Veterinary practise
BS 7671 Regulation 411.3.3 sets out the requirements for additional protection to socket outlets for use indoors. There are exceptions depending upon the level of supervision, and also for socket outlets that are provided for a specific item of equipment - as opposed to those for general use.
If there are concerns over the welfare of animals in the event of a trip, then dedicated circuits for this equipment could be considered, ensuring that the outlet is identified to the equipment it has been designed to serve (exception (b) of 411.3.3.).
Any outlets intended for general purpose use by ordinary persons should be additionally protected at 30mA by an RCD, unless the use of them is effectively supervised. The question of supervision should be discussed with the practice management to establish whether any such supervision is achievable and sustainable.
The same discussion should also include any supervision required by Regulation 522.6.101 with reference to cables concealed in walls and partitions, as a consumer unit replacement is effectively an alteration as defined by BS 7671 and hence the requirements of 522.6.101 should be considered.
P/230 . Worth considering Section 710 in relation to veterinary surgeries if there are concerns over animal welfare during surgery
( Note 2 to Regulation 710.1 ).
A
amberleaf
Basics :
( Existing installation ) The full ( EIC Report ) documentation .
( New installation ) Safety certification
Firstly this one goes round the circuit , all the time
You have to ( prove ) that you are competent person , in the eyes of C&G
Firstly people need to get their heads around the difference between Initial verification & Periodic Inspection & Testing. They are 2 different jobs that have some common activities.
Inspection & Testing
Turning to Initial verification & Testing you need to have a look at chapter 61 of BS-7671:2011:. Have a look and see what tests are applicable to Initial verification ( Chapter 61 )
Turning to Periodic Inspection & Testing you need to have a look at chapter 62 of BS-7671:2011:. Have a look and see what tests are applicable to Periodic testing ( Chapter 62 )
P/16 . Extracts . Verification :
The responsibility for comparing inspection & test results with relevant criteria as required by Regulation 612.1. ... ( relevant criteria ) Testing
( Existing installation ) The full ( EIC Report ) documentation .
( New installation ) Safety certification
Firstly this one goes round the circuit , all the time
You have to ( prove ) that you are competent person , in the eyes of C&G
Firstly people need to get their heads around the difference between Initial verification & Periodic Inspection & Testing. They are 2 different jobs that have some common activities.
Inspection & Testing
Turning to Initial verification & Testing you need to have a look at chapter 61 of BS-7671:2011:. Have a look and see what tests are applicable to Initial verification ( Chapter 61 )
Turning to Periodic Inspection & Testing you need to have a look at chapter 62 of BS-7671:2011:. Have a look and see what tests are applicable to Periodic testing ( Chapter 62 )
P/16 . Extracts . Verification :
The responsibility for comparing inspection & test results with relevant criteria as required by Regulation 612.1. ... ( relevant criteria ) Testing
A
amberleaf
Taken from Extracts
You have to put in the studying
GN-3 : P/35
Method 2 . ( R[SUP]2[/SUP] ) Testing bonding conductors & earthing conductors
re-cap ,
To confirm the continuity of these protective conductor's , test method 2 may be used .
This method can also be used to confirm a bonding connection between extraneous-conductive-part , where it is not possible to see a bonding-connection e.g.
P/34
Test method 2 ... ( for circuit )
re-cap ,
This test measures the continuity résistance of the circuit protective conductor , ( R[SUP]2[/SUP] ) which should be recorded on a , Schedule of Test Results
( see earlier note " Parallel earth parts & effects on test readings )
P/32 , 2.7.5. Continuity of protective conductors , including Main & Supplementary bonding
Regulation 411.3.1.1. requires that installations which provide protection against electric-shock using ( ADS ) must have a circuit protective conductor ( run ) to & terminated at each point in the wiring & each accessory , refer .
Regulation 612.2.1. requires that a continuity check be carried out on all circuits including ring-circuit's
There are ( Two widely used test methods ) that have evolved for checking conductor continuity , also measures ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) which , when added to the external impedance ( Ze ) enables the earth fault loop impedance ( Zs ) to be checked against the design
P/33 , Test method 1 ... ( for circuit ) Connections for testing continuity of protective-conductors
2.7.6. Continuity of ring-final-circuit-conductor(s)
Three-steps test is required to ( Verify the continuity ) Etc refer
Regulation 612.2.2.
You have to put in the studying
GN-3 : P/35
Method 2 . ( R[SUP]2[/SUP] ) Testing bonding conductors & earthing conductors
re-cap ,
To confirm the continuity of these protective conductor's , test method 2 may be used .
This method can also be used to confirm a bonding connection between extraneous-conductive-part , where it is not possible to see a bonding-connection e.g.
P/34
Test method 2 ... ( for circuit )
re-cap ,
This test measures the continuity résistance of the circuit protective conductor , ( R[SUP]2[/SUP] ) which should be recorded on a , Schedule of Test Results
( see earlier note " Parallel earth parts & effects on test readings )
P/32 , 2.7.5. Continuity of protective conductors , including Main & Supplementary bonding
Regulation 411.3.1.1. requires that installations which provide protection against electric-shock using ( ADS ) must have a circuit protective conductor ( run ) to & terminated at each point in the wiring & each accessory , refer .
Regulation 612.2.1. requires that a continuity check be carried out on all circuits including ring-circuit's
There are ( Two widely used test methods ) that have evolved for checking conductor continuity , also measures ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) which , when added to the external impedance ( Ze ) enables the earth fault loop impedance ( Zs ) to be checked against the design
P/33 , Test method 1 ... ( for circuit ) Connections for testing continuity of protective-conductors
2.7.6. Continuity of ring-final-circuit-conductor(s)
Three-steps test is required to ( Verify the continuity ) Etc refer
Regulation 612.2.2.
A
amberleaf
My point is :
in your wording in Exams . You have proven a true reading . ( Ω ) in the eyes of C&Gs
I normally , Null my test-leads when carrying out the ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) test ... meter takes the résistance of the leads into consideration Let you examiner known . ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) You have proven a true reading . " Nulling out leads "
in your wording in Exams . You have proven a true reading . ( Ω ) in the eyes of C&Gs
I normally , Null my test-leads when carrying out the ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) test ... meter takes the résistance of the leads into consideration Let you examiner known . ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) You have proven a true reading . " Nulling out leads "
A
amberleaf
Why do you need to null the test leads on an instrument , in the eyes of C&Gs
Accuracy. If you don't null ( zero ) the test leads when you measure the résistance of your circuit you will also be measuring the resistance of your leads at the same time giving a false / inaccurate
Functional check of your leads & tester
Accuracy. If you don't null ( zero ) the test leads when you measure the résistance of your circuit you will also be measuring the resistance of your leads at the same time giving a false / inaccurate
Functional check of your leads & tester
A
amberleaf
On Rant Mode :
There was also evidence of a lack of understanding of basic electrical principles . RCDs
Chief Examiners’ report - August 2013
A large number of candidates were unable to correctly explain the effect on an RCD of a line to neutral fault. Most candidates believed this would result in the operation of the RCD and very few identified that the RCD would operate in the event of a fault between live conductors & earth.
Most candidates identified the Electricity at Work Regulations as identifying the requirements for an inspector (although some incorrectly referred to it as an Act). Very few candidates were able to identify the title given to an inspector (Duty Holder) and the status (competent person) which are attributed to the Inspector in EWR.
▼▼▼
Candidates appear to be unaware of the required action by the inspector in the event of a dangerous situation being discovered during the inspection. The most common incorrect answer was to isolate the supply, often including repair the fault etc. The inspector’s responsibility is referred to in GN-3 under Item 1.2 Required competence as: ‘In the event of a dangerous situation being found the inspector should recommend the immediate isolation of the defective part.’ It is important to remember that the inspector must obtain permission before isolating to ensure there are no other serious consequences to that action
Chief Examiners’ report . There's always room for Improvement .
GN-3 . 1.2 Required competence .
610.5. The inspector carrying out the inspection & testing or any electrical installation must as appropriate to his or her function , have a sound knowledge & experience relevant to the nature of the installation being inspected & tested , & of BS-7671: & other relevant technical standards , The inspector must also be fully versed in the inspection & testing procedures & employ suitable test equipment during the inspection & testing process .
The inspector should have sufficient inspection & testing skills together with experience in interpreting the results with respect to the requirements of BS-7671:
it is worth noting that the person responsible for inspection & testing may be required to formally demonstrate competence by means of registration / certification under a recognised scheme . etc
it is the responsibility of the inspector , as appropriate to either the initial or periodic inspection , to
634.2. ►► In the event of a dangerous situation being ( found ) the inspector should recommend the , immediate isolation of the defective part .
The person ordering the work should be informed , in writing , of this recommendation without delay .
There was also evidence of a lack of understanding of basic electrical principles . RCDs
Chief Examiners’ report - August 2013
A large number of candidates were unable to correctly explain the effect on an RCD of a line to neutral fault. Most candidates believed this would result in the operation of the RCD and very few identified that the RCD would operate in the event of a fault between live conductors & earth.
Most candidates identified the Electricity at Work Regulations as identifying the requirements for an inspector (although some incorrectly referred to it as an Act). Very few candidates were able to identify the title given to an inspector (Duty Holder) and the status (competent person) which are attributed to the Inspector in EWR.
▼▼▼
Candidates appear to be unaware of the required action by the inspector in the event of a dangerous situation being discovered during the inspection. The most common incorrect answer was to isolate the supply, often including repair the fault etc. The inspector’s responsibility is referred to in GN-3 under Item 1.2 Required competence as: ‘In the event of a dangerous situation being found the inspector should recommend the immediate isolation of the defective part.’ It is important to remember that the inspector must obtain permission before isolating to ensure there are no other serious consequences to that action
Chief Examiners’ report . There's always room for Improvement .
GN-3 . 1.2 Required competence .
610.5. The inspector carrying out the inspection & testing or any electrical installation must as appropriate to his or her function , have a sound knowledge & experience relevant to the nature of the installation being inspected & tested , & of BS-7671: & other relevant technical standards , The inspector must also be fully versed in the inspection & testing procedures & employ suitable test equipment during the inspection & testing process .
The inspector should have sufficient inspection & testing skills together with experience in interpreting the results with respect to the requirements of BS-7671:
it is worth noting that the person responsible for inspection & testing may be required to formally demonstrate competence by means of registration / certification under a recognised scheme . etc
it is the responsibility of the inspector , as appropriate to either the initial or periodic inspection , to
634.2. ►► In the event of a dangerous situation being ( found ) the inspector should recommend the , immediate isolation of the defective part .
The person ordering the work should be informed , in writing , of this recommendation without delay .
M
Meggerman
634.2. ►► In the event of a dangerous situation being ( found ) the inspector should recommend the , immediate isolation of the defective part .
The person ordering the work should be informed , in writing , of this recommendation without delay .[/QUOTE]
mmm.... and then when they don't do anything about it, who are they going to look at. I would still isolate it myself if it was not a easy fix. I could quite happily argue about that as could justify my actions on grounds of safety. If they want it back on in an unsafe condition let them turn it back on.
The person ordering the work should be informed , in writing , of this recommendation without delay .[/QUOTE]
mmm.... and then when they don't do anything about it, who are they going to look at. I would still isolate it myself if it was not a easy fix. I could quite happily argue about that as could justify my actions on grounds of safety. If they want it back on in an unsafe condition let them turn it back on.
A
amberleaf
Meggerman . I do understand your views .
634.2. ►► In the event of a dangerous situation being ( found ) the inspector should recommend the , immediate isolation of the defective part .
The person ordering the work should be informed , in writing , of this recommendation without delay .
It is important to remember that the inspector must obtain permission before isolating to ensure there are no other serious consequences to that action
Meggerman , My situation here is only to point out the facts here .
634.2. ►► In the event of a dangerous situation being ( found ) the inspector should recommend the , immediate isolation of the defective part .
The person ordering the work should be informed , in writing , of this recommendation without delay .
It is important to remember that the inspector must obtain permission before isolating to ensure there are no other serious consequences to that action
Meggerman , My situation here is only to point out the facts here .
M
Meggerman
I know mate, I'm not shooting the messenger
. I think 634.2. should be rewritten with regard to domestic (as there is going to be nothing of more serious consequence in a home than that of electric shock or fire) and give Electricians the authority to isolate dangerous situations as Gas Safe engineers can.
A
amberleaf
100% right my friend . Electricians the authority to isolate dangerous situations as Gas Safe engineers can.
A
amberleaf
On Rant mode .
( IR ) GN-3 : The purpose of the insulation résistance test is to verify that the insulation of conductors provides adequate insulation .
is not damaged & that live conductors or protective conductors are not short-circuited .
( IR ) -&-s . That any circuit under ( 2MΩ ) should be investigated
GN-3 are reminding us . résistance values should be ( 2MΩ or greater ) for each circuit .
The whole installation must have an ( IR ) résistance of greater than ( 1MΩ )
Table 61 : Minimum values of ( IR ) 1.0MΩ
Note 2 : ( IR ) values are usually much higher than those of Table 61 . 1.0MΩ
My reason is ( Conductors in Parallel ) " Scenario "
( Zdb ) Three phase sub-main is tested & the results are ??
L1 to earth - 130MΩ
L2 to earth - 80MΩ
L3 to earth - 50MΩ
Neutral to earth - 100MΩ
Conductors joined & tested to earth . ( 500V - d.c. )
Calculation : 1/R[SUP]1 [/SUP] + 1/R[SUP]2 [/SUP]+ 1/R[SUP]3 [/SUP]+ 1/R[SUP]4 [/SUP]= 1/Rt
Values :- 1/30 + 1/80 + 1/50 + 1/100 + 1/0.05 = 19.92MΩ
By Calculation : 130 X[SUP]1 [/SUP] + 80 X[SUP]1 [/SUP] + 50 X[SUP]1 [/SUP] + 100 X[SUP]1 [/SUP] = X[SUP]1 [/SUP]19.92MΩ
lower because the conductors are in ( Parallel )
GN-3 : reminds us . Testing of individual circuits . New & Existing circuit's.
Extracts : GN-3 :
( IR ) Simple installations that contain No distribution circuits should preferably be tested as a Whole .
To perform the test in a complex installation it may need to be ( subdivided ) into its component parts .
reminder : 2392 / 2394 :
Although an ( IR ) value of Not less than ( 1MΩ ) complies with Regulation , New installations should Not yield test results this ( LOW )
Regulation : Note 2 : ( IR ) values are usually much higher than those of Table 61 . 1.0MΩ
( IR ) GN-3 : The purpose of the insulation résistance test is to verify that the insulation of conductors provides adequate insulation .
is not damaged & that live conductors or protective conductors are not short-circuited .
( IR ) -&-s . That any circuit under ( 2MΩ ) should be investigated
GN-3 are reminding us . résistance values should be ( 2MΩ or greater ) for each circuit .
The whole installation must have an ( IR ) résistance of greater than ( 1MΩ )
Table 61 : Minimum values of ( IR ) 1.0MΩ
Note 2 : ( IR ) values are usually much higher than those of Table 61 . 1.0MΩ
My reason is ( Conductors in Parallel ) " Scenario "
( Zdb ) Three phase sub-main is tested & the results are ??
L1 to earth - 130MΩ
L2 to earth - 80MΩ
L3 to earth - 50MΩ
Neutral to earth - 100MΩ
Conductors joined & tested to earth . ( 500V - d.c. )
Calculation : 1/R[SUP]1 [/SUP] + 1/R[SUP]2 [/SUP]+ 1/R[SUP]3 [/SUP]+ 1/R[SUP]4 [/SUP]= 1/Rt
Values :- 1/30 + 1/80 + 1/50 + 1/100 + 1/0.05 = 19.92MΩ
By Calculation : 130 X[SUP]1 [/SUP] + 80 X[SUP]1 [/SUP] + 50 X[SUP]1 [/SUP] + 100 X[SUP]1 [/SUP] = X[SUP]1 [/SUP]19.92MΩ
lower because the conductors are in ( Parallel )
GN-3 : reminds us . Testing of individual circuits . New & Existing circuit's.
Extracts : GN-3 :
( IR ) Simple installations that contain No distribution circuits should preferably be tested as a Whole .
To perform the test in a complex installation it may need to be ( subdivided ) into its component parts .
reminder : 2392 / 2394 :
Although an ( IR ) value of Not less than ( 1MΩ ) complies with Regulation , New installations should Not yield test results this ( LOW )
Regulation : Note 2 : ( IR ) values are usually much higher than those of Table 61 . 1.0MΩ
G
GLENNSPARK
mmm.... and then when they don't do anything about it, who are they going to look at. I would still isolate it myself if it was not a easy fix. I could quite happily argue about that as could justify my actions on grounds of safety. If they want it back on in an unsafe condition let them turn it back on.[/QUOTE]
without first gaining permission from the person ordering the work?
A
amberleaf
On rant mode :
Table 41.5. ( Zs ) non-delayed RCDs
BS-EN-61008-1
BS-EN-61009-1
BS-7671:2011: gives maximum earth fault loop impedance permissible for the correct operation of RCD
The values . By calculation
50 ) is the maximum voltage
I∆n ) is the trip rating of the residual current device .
Zs ) is the earth fault loop impedance
rating of the device is ( 100mA ) .. 50 / 01 = 500Ω
Electrode résistance in ( Ω ) 100mA - 500Ω
P/57 . BS-7671: Note 2* , The résistance of the installation earth-electrode should be low as practicable .
A value exceeding 200 ohms may not be stable .
( 50V ÷ 30mA = 1.666666667 ) 1667*
411.5. TT system
411.5.1. Every exposed-conductive-part which is to be protected by a single protective device shall be connected , via the main earthing terminal , to a common earth-electrode .
GN-3 P/48 . E1
Scenario : Three electrodes - earthing electrode under test . a current electrode & a potential electrode .
measurement taken , 79Ω , 85Ω , 80Ω . = 244 ... added together & an average value calculated . 244 ÷ 3 = 81.33Ω
find the different between the average value & the highest measured value . ( 85Ω ) 85 sub 81.33 = 3.67
the percentage of this value to the average value must now be found . 3.67 x 100 ÷ 81.33 = 4.51
fig 2.7 . P/49
GN-3 tells us that the accuracy of this measurement is typically ( 1.2 times the percentage deviation )
correct value . x percentage deviation ( 1.2 ) 4.51 x 1.2 = 5.41
refer to . P49
The accuracy of the measurement using this technique is typically ( 1.2 times ) the percentage deviation of the readings , it is difficult to achieve an accuracy of measurement better than ( 2% ) & inadvisable to accept readings that differ by more than ( 5% ) refer .
Table 41.5. ( Zs ) non-delayed RCDs
BS-EN-61008-1
BS-EN-61009-1
BS-7671:2011: gives maximum earth fault loop impedance permissible for the correct operation of RCD
The values . By calculation
50 ) is the maximum voltage
I∆n ) is the trip rating of the residual current device .
Zs ) is the earth fault loop impedance
rating of the device is ( 100mA ) .. 50 / 01 = 500Ω
Electrode résistance in ( Ω ) 100mA - 500Ω
P/57 . BS-7671: Note 2* , The résistance of the installation earth-electrode should be low as practicable .
A value exceeding 200 ohms may not be stable .
( 50V ÷ 30mA = 1.666666667 ) 1667*
411.5. TT system
411.5.1. Every exposed-conductive-part which is to be protected by a single protective device shall be connected , via the main earthing terminal , to a common earth-electrode .
GN-3 P/48 . E1
Scenario : Three electrodes - earthing electrode under test . a current electrode & a potential electrode .
measurement taken , 79Ω , 85Ω , 80Ω . = 244 ... added together & an average value calculated . 244 ÷ 3 = 81.33Ω
find the different between the average value & the highest measured value . ( 85Ω ) 85 sub 81.33 = 3.67
the percentage of this value to the average value must now be found . 3.67 x 100 ÷ 81.33 = 4.51
fig 2.7 . P/49
GN-3 tells us that the accuracy of this measurement is typically ( 1.2 times the percentage deviation )
correct value . x percentage deviation ( 1.2 ) 4.51 x 1.2 = 5.41
refer to . P49
The accuracy of the measurement using this technique is typically ( 1.2 times ) the percentage deviation of the readings , it is difficult to achieve an accuracy of measurement better than ( 2% ) & inadvisable to accept readings that differ by more than ( 5% ) refer .
S
Sintra
Guys can we please keep this thread as info only from Amberleaf and cut the replies.
A
amberleaf
Extracts'
After replacing a consumer unit, it is found that there is a shared neutral between the upstairs and downstairs lighting circuits.
Would it comply with BS-7671: if I put the lighting onto one circuit to avoid the RCD tripping ?
Electrical Safety First's Best Practice Guide No 6 ( Consumer unit replacement in domestic premises ) sets out a procedure to help avoid such foreseeable circumstances.
In any event, the shared neutral situation must be corrected to remove the electric shock hazard.
Preferably each circuit should be provided with its own neutral to satisfy Section 314.
However, where this is not practicable, the two lighting circuits sharing the neutral may be connected to a single protective device (creating a single circuit), provided that the circuit is suitable for the connected load.
Regulation number(s) 314 .
After replacing a consumer unit, it is found that there is a shared neutral between the upstairs and downstairs lighting circuits.
Would it comply with BS-7671: if I put the lighting onto one circuit to avoid the RCD tripping ?
Electrical Safety First's Best Practice Guide No 6 ( Consumer unit replacement in domestic premises ) sets out a procedure to help avoid such foreseeable circumstances.
In any event, the shared neutral situation must be corrected to remove the electric shock hazard.
Preferably each circuit should be provided with its own neutral to satisfy Section 314.
However, where this is not practicable, the two lighting circuits sharing the neutral may be connected to a single protective device (creating a single circuit), provided that the circuit is suitable for the connected load.
Regulation number(s) 314 .
A
amberleaf
just in from work . knock something up .
On rant mode .
Circuit breakers : As it cannot be predicted where in the ( Range ) a circuit breaker will trip ?? 3 / 5 , 5 / 10 , 10 / 20 . etc
3 x 32A = 96.
5 x 32A = 160.
10 x 32A = 320
The limiting values of earth fault loop impedance for BS-EN-60898-1 , in Table 41.3 are based on the upper range values of current
Instantaneous Tripping .
B above ( 3 In ) up to & including ( 5 In )
C above ( 5 In ) up to & including ( 10 In )
D above ( 10 In ) up to & including ( 20 In )
P/301 , fig 3A4 . The prospective earth fault current for ( 32A type B ) circuit breaker is required to be not less than ( 160A ) .. that is , 5 In . etc
by calculation 5 x 32A = 160A .. Zs ≤ 230 / 160 = 1.43 . etc
P/302 , fig 3A5 . The prospective earth fault current for ( 32A type C ) circuit breaker is required to be not less than ( 320A ) .. that is , 10 In . etc
by calculation 10 x 32A = 320A
P/303 , fig 3A6 . The prospective earth fault current for ( 32A type D ) circuit breaker is required to be not less than ( 640A ) .. that is , 20 In . etc
by calculation 20 x 32A = 640A
Type B trips between 3 & 5 time full load current .. ( 5 maximum ) etc
Type C trips between 5 & 10 times full load current
Type D trips between 10 & 20 times full load current.
Confirm the maximum permitted earth fault loop impedance of BS-EN-60898-1 , circuit breakers
Type B circuit-breaker will withstand currents of upto a maximum of ( 5x ) it's current rating ( In ) before disconnection occurs.
Divide nominal voltage to Earth ( Uo ) 230 by ( 5 ) 230 ÷ 5 = 46.
Type C, the maximum ( 10x ) current rating 230 / 10 = 23.
Type D, maximum ( 20x ) current rating 230 / 20 = 11.5
32A type B circuit breaker ( ÷ ) B figure of ( 46 ) by calculation :- 46 ÷ 32 = 1.43, rounded up to 1.44 which is the value given in table 41.3 of BS- 7671.
To adjust the value for the temperature corrected value, multiply ( 1.44 ) figure in this instance by 0.8 which gives us 1.44 x 0.8 = 1.152 , value given in O.S.G. table B6 ( B 32A - 1.16 )
On rant mode .
Circuit breakers : As it cannot be predicted where in the ( Range ) a circuit breaker will trip ?? 3 / 5 , 5 / 10 , 10 / 20 . etc
3 x 32A = 96.
5 x 32A = 160.
10 x 32A = 320
The limiting values of earth fault loop impedance for BS-EN-60898-1 , in Table 41.3 are based on the upper range values of current
Instantaneous Tripping .
B above ( 3 In ) up to & including ( 5 In )
C above ( 5 In ) up to & including ( 10 In )
D above ( 10 In ) up to & including ( 20 In )
P/301 , fig 3A4 . The prospective earth fault current for ( 32A type B ) circuit breaker is required to be not less than ( 160A ) .. that is , 5 In . etc
by calculation 5 x 32A = 160A .. Zs ≤ 230 / 160 = 1.43 . etc
P/302 , fig 3A5 . The prospective earth fault current for ( 32A type C ) circuit breaker is required to be not less than ( 320A ) .. that is , 10 In . etc
by calculation 10 x 32A = 320A
P/303 , fig 3A6 . The prospective earth fault current for ( 32A type D ) circuit breaker is required to be not less than ( 640A ) .. that is , 20 In . etc
by calculation 20 x 32A = 640A
Type B trips between 3 & 5 time full load current .. ( 5 maximum ) etc
Type C trips between 5 & 10 times full load current
Type D trips between 10 & 20 times full load current.
Confirm the maximum permitted earth fault loop impedance of BS-EN-60898-1 , circuit breakers
Type B circuit-breaker will withstand currents of upto a maximum of ( 5x ) it's current rating ( In ) before disconnection occurs.
Divide nominal voltage to Earth ( Uo ) 230 by ( 5 ) 230 ÷ 5 = 46.
Type C, the maximum ( 10x ) current rating 230 / 10 = 23.
Type D, maximum ( 20x ) current rating 230 / 20 = 11.5
32A type B circuit breaker ( ÷ ) B figure of ( 46 ) by calculation :- 46 ÷ 32 = 1.43, rounded up to 1.44 which is the value given in table 41.3 of BS- 7671.
To adjust the value for the temperature corrected value, multiply ( 1.44 ) figure in this instance by 0.8 which gives us 1.44 x 0.8 = 1.152 , value given in O.S.G. table B6 ( B 32A - 1.16 )
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Initial Verification . is required for ( New work ) & alterations & additions .
Cover your " Derriere "
GN-3 . P/16 . ( Verification ) as a Competent person .
The responsibility for comparing Inspection & Test-results with relevant criteria , as required by Regulation 612.1. lies with the party responsible for inspection & testing the installation , this party , which may be the person carrying out the inspection & testing , should sign the inspection & testing box of the ( EIC ) or the declaration box of the ( MEIWC ) if the person carrying out the inspection & testing has also been responsible for the design & construction of the installation , he or she must also sign the design & construction boxes of the ( EIC ) , or make use of the single signature ( EIC )
Initial Verification
Q/As C&G. State the reason why it is necessary to undertake an initial verification !!
GN-3 . P/15 . 2.1. ( Initial Verification ) is carried out on a ( New installation ) before it is put into service .
The ( Purpose of initial verification ) is to confirm by way of Inspection & testing , during construction & on completion , that the installation complies with the design & construction aspects of BS-7671: .. in so far as is reasonably practicable .
612 Testing .
612.1. The tests of Regulations 612.2. to 612.13 , where relevant , shall be carried out & the results compared with relevant criteria
610.1. Initial Verification
Every installation shall , during erection & on completion before being put into service , be inspected & tested to verify , .. in so far as is reasonably practicable
Protection of persons & livestock
The prevention of damage to property & installed equipment , during inspection & testing .
611.2. The inspector shall be made to verify that the installed electrical equipment is . refer (i) (ii) (iii) etc
GN-3 : 611.2. BS-7671: provides a format list in Regulation 611.2. of item to be ( Verified ) again so far as is reasonably
612 Testing .
612.1. The tests of Regulations 612.2. to 612.13 , where relevant , shall be carried out & the results compared with relevant criteria , (i) (ii) (iii) etc
Cover your " Derriere "
GN-3 . P/16 . ( Verification ) as a Competent person .
The responsibility for comparing Inspection & Test-results with relevant criteria , as required by Regulation 612.1. lies with the party responsible for inspection & testing the installation , this party , which may be the person carrying out the inspection & testing , should sign the inspection & testing box of the ( EIC ) or the declaration box of the ( MEIWC ) if the person carrying out the inspection & testing has also been responsible for the design & construction of the installation , he or she must also sign the design & construction boxes of the ( EIC ) , or make use of the single signature ( EIC )
Initial Verification
Q/As C&G. State the reason why it is necessary to undertake an initial verification !!
GN-3 . P/15 . 2.1. ( Initial Verification ) is carried out on a ( New installation ) before it is put into service .
The ( Purpose of initial verification ) is to confirm by way of Inspection & testing , during construction & on completion , that the installation complies with the design & construction aspects of BS-7671: .. in so far as is reasonably practicable .
612 Testing .
612.1. The tests of Regulations 612.2. to 612.13 , where relevant , shall be carried out & the results compared with relevant criteria
610.1. Initial Verification
Every installation shall , during erection & on completion before being put into service , be inspected & tested to verify , .. in so far as is reasonably practicable
Protection of persons & livestock
The prevention of damage to property & installed equipment , during inspection & testing .
611.2. The inspector shall be made to verify that the installed electrical equipment is . refer (i) (ii) (iii) etc
GN-3 : 611.2. BS-7671: provides a format list in Regulation 611.2. of item to be ( Verified ) again so far as is reasonably
612 Testing .
612.1. The tests of Regulations 612.2. to 612.13 , where relevant , shall be carried out & the results compared with relevant criteria , (i) (ii) (iii) etc
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BS-EN-60898-1 Circuit breakers have replaced the fuses of yesteryear . so the RCDs have been written in stone .
Each manufacturer is free to specify at what range of current the circuit-breaker will react to a perceived ( short circuit )
Circuit breaker is the basic means by which wiring is protected from both a short circuit & overload damage .
Definitions : P/35 . Short-circuit current . An overcurrent resulting from a fault of negligible impedance between ( Live-conductors ) having a difference in potential under normal operating conditions
A fault such as a short-circuit or earth fault , is not an ” Overload ”
Circuit breaker has two independent trip mechanisms: Thermal & Magnetic.
The former reacts to overloads & causes the circuit breaker to trip, while the latter responds to short circuit fault currents.
- Circuit breaker is affected by the temperature of its surroundings
- The magnetic portion of a circuit breaker is sometimes called the instantaneous trip portion.
The defection of the bi-metallic strip depends on the temperature thus the circuit-breaker has a trip temperature and it is the heat generated within the circuit-breaker that causes the temperature to rise, the faster the heat rise, the faster the breaker reaches temperature and trips. Heat is directly proportional to the power (watts)
Under fault conditions .
Magnetic trip level vs. Thermal trip time .
Magnetic trip level / Amperes .
Thermal characteristics (trip time) .. Seconds . ( depending on current level )
Thermal Example : The light draws more than 15A , 10A circuit-breaker for an extended period of time creating a thermal overload.
- Circuit-breaker is not intended to prevent electrical-shock .. That is why you use ( ADS ) RCD / RCBOs ( Additional protection )
- Circuit-breaker does not prevent arcing
- Thermal portions of breakers are affected by ambient temperatures
- Definition P/23 . Ambient Temperature : The temperature of the air or other medium where the equipment is to be used .
( Expected air temperature surrounding the rated circuit breaker )
GN-3 . P/56
Two short-circuit capacity ratings are defined in BS-EN-60898-1 & BS-EN-61009-1 :
( Icn ) the rated short-circuit capacity ( marked on the device )
( Ics ) the service short-circuit capacity .
This has came up on in Exams , before
( Icn ) value ( in Amperes )
( Icn ) is the maximum fault current the device can interrupt safety , although it may no longer be usable
( Icn ) value is marked on the device in a rectangle e.g. ( 6000 ) & for the majority of applications the prospective fault current at the terminals of the circuit-breaker should not exceed this value .
( Ics ) is the maximum fault current the device can interrupt safety , without loss of performance
for domestic installations the ( PFC ) is unlikely to exceed 6kA ... Exams . up to which value ( Icn ) ◄► will equal ( Ics )
O.S.G. Table 7.2.7. P/71
The difference between the two is the condition of the circuit-breaker after manufactures testing . ( Icn ) & ( Ics )
Manufacturer ( Overload )
A slow & small overcurrent situation that causes the ampacity and temperature of the circuit to gradually increase over time.
This type of event is characterized by a slight increase in the load (ampacity) on the circuit and is interrupted by the thermal trip unit of the breaker
Manufacturer ( Breaker definition )
A breaker is a device designed to isolate a circuit during an overcurrent event without the use of a fusible element. A breaker is a resettable protective device that protects against two types of overcurrent situations; Overload & Short Circuit.
Manufacturer ( Short circuit )
A rapid and intense overcurrent situation that causes the ampacity of the circuit to increase. This type of event is characterized by a dramatic increase in
the load (ampacity) on the circuit and is interrupted by the magnetic trip unit of the breaker
Manufacturer ( Overload protection )
The thermal trip unit protects against a continuous overload. The thermal unit is comprised of a bimetal element located behind the circuit breaker trip bar and is part of the breaker’s current carrying path When there is an overload, the increased current flow heats the bimetal causing it to bend. As the bimetal bends it pulls the trip bar which opens the breaker’s contacts.
Each manufacturer is free to specify at what range of current the circuit-breaker will react to a perceived ( short circuit )
Circuit breaker is the basic means by which wiring is protected from both a short circuit & overload damage .
Definitions : P/35 . Short-circuit current . An overcurrent resulting from a fault of negligible impedance between ( Live-conductors ) having a difference in potential under normal operating conditions
A fault such as a short-circuit or earth fault , is not an ” Overload ”
Circuit breaker has two independent trip mechanisms: Thermal & Magnetic.
The former reacts to overloads & causes the circuit breaker to trip, while the latter responds to short circuit fault currents.
- Circuit breaker is affected by the temperature of its surroundings
- The magnetic portion of a circuit breaker is sometimes called the instantaneous trip portion.
The defection of the bi-metallic strip depends on the temperature thus the circuit-breaker has a trip temperature and it is the heat generated within the circuit-breaker that causes the temperature to rise, the faster the heat rise, the faster the breaker reaches temperature and trips. Heat is directly proportional to the power (watts)
Under fault conditions .
Magnetic trip level vs. Thermal trip time .
Magnetic trip level / Amperes .
Thermal characteristics (trip time) .. Seconds . ( depending on current level )
Thermal Example : The light draws more than 15A , 10A circuit-breaker for an extended period of time creating a thermal overload.
- Circuit-breaker is not intended to prevent electrical-shock .. That is why you use ( ADS ) RCD / RCBOs ( Additional protection )
- Circuit-breaker does not prevent arcing
- Thermal portions of breakers are affected by ambient temperatures
- Definition P/23 . Ambient Temperature : The temperature of the air or other medium where the equipment is to be used .
( Expected air temperature surrounding the rated circuit breaker )
GN-3 . P/56
Two short-circuit capacity ratings are defined in BS-EN-60898-1 & BS-EN-61009-1 :
( Icn ) the rated short-circuit capacity ( marked on the device )
( Ics ) the service short-circuit capacity .
This has came up on in Exams , before
( Icn ) value ( in Amperes )
( Icn ) is the maximum fault current the device can interrupt safety , although it may no longer be usable
( Icn ) value is marked on the device in a rectangle e.g. ( 6000 ) & for the majority of applications the prospective fault current at the terminals of the circuit-breaker should not exceed this value .
( Ics ) is the maximum fault current the device can interrupt safety , without loss of performance
for domestic installations the ( PFC ) is unlikely to exceed 6kA ... Exams . up to which value ( Icn ) ◄► will equal ( Ics )
O.S.G. Table 7.2.7. P/71
The difference between the two is the condition of the circuit-breaker after manufactures testing . ( Icn ) & ( Ics )
Manufacturer ( Overload )
A slow & small overcurrent situation that causes the ampacity and temperature of the circuit to gradually increase over time.
This type of event is characterized by a slight increase in the load (ampacity) on the circuit and is interrupted by the thermal trip unit of the breaker
Manufacturer ( Breaker definition )
A breaker is a device designed to isolate a circuit during an overcurrent event without the use of a fusible element. A breaker is a resettable protective device that protects against two types of overcurrent situations; Overload & Short Circuit.
Manufacturer ( Short circuit )
A rapid and intense overcurrent situation that causes the ampacity of the circuit to increase. This type of event is characterized by a dramatic increase in
the load (ampacity) on the circuit and is interrupted by the magnetic trip unit of the breaker
Manufacturer ( Overload protection )
The thermal trip unit protects against a continuous overload. The thermal unit is comprised of a bimetal element located behind the circuit breaker trip bar and is part of the breaker’s current carrying path When there is an overload, the increased current flow heats the bimetal causing it to bend. As the bimetal bends it pulls the trip bar which opens the breaker’s contacts.
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( Manufacturer )
BS-EN-60898-1 . define the rated current ( In ) of a circuit breaker for low voltage distribution applications as the maximum current that the breaker is designed to carry continuously (at an ambient air temperature of 30°C )
BS-EN-60898-1 . define the rated current ( In ) of a circuit breaker for low voltage distribution applications as the maximum current that the breaker is designed to carry continuously (at an ambient air temperature of 30°C )
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Circuit-breaker is labelled with the rated current in amperes, but without the unit symbol "A" . Instead, the ampere figure is preceded by a letter " B. C . D ", which indicates the instantaneous tripping current
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On rant mode .
( MEIWC ) ... classed as , " Certificate "
The Regulations' must state the facts ... ( MEIWC ) You have to prove yourself in any Exams .
P/389 . ( iv ) Competent person will , as appropriate to their function under (i) have a sound knowledge & experience relevant to the nature of the work undertaken & the technical standards set down in these Regulations : be fully versed in the inspection & testing of an installation .
Certification & Reporting
P/398 . (ii) The Minor Work Certificate , required by Part 6 should be made out & signed or otherwise authenticated by a competent person in respect of design , construction , inspection & testing of the ( minor work )
In a case of an alteration or additions of an ( Existing electrical installation )
Minor Electrical installation Work Certificates .. ( MEIWC )
Sometime it helps to break thing down into Q/As .
P/394 . ( MEIWC ) The Minor Work Certificate is intended to be used for :
( Existing electrical circuit ) Additions ) to an installation that ( do not extend ) .. to the provision of a new-circuit .
( Existing electrical circuit ) Alteration ) to an installation that ( do not extend ) .. to the provision of a new-circuit .
Ask yourself what can it be used for . ??
This Certificate may also be used for the replacement of equipment such as accessories or luminaries
This Certificate may also be used for the replacement of socket-outlets .
This Certificate may also be used for the replacement luminaires . etc
( MEIWC ) ... But Not for the replacement of distribution boards or similar items
C&Gs like to hear this one , Appropriate inspection & testing , however , should always be carried out irrespective of the extent of the work undertaken
Point's to be aware of . ( MEIWC )
P/394 . This Certificate is not appropriate if you requested the contractor to undertake more extensive installation work . for which you should have received an Electrical Installation Certificate . ( EIC )
( MEIWC ) ... classed as , " Certificate "
The Regulations' must state the facts ... ( MEIWC ) You have to prove yourself in any Exams .
P/389 . ( iv ) Competent person will , as appropriate to their function under (i) have a sound knowledge & experience relevant to the nature of the work undertaken & the technical standards set down in these Regulations : be fully versed in the inspection & testing of an installation .
Certification & Reporting
P/398 . (ii) The Minor Work Certificate , required by Part 6 should be made out & signed or otherwise authenticated by a competent person in respect of design , construction , inspection & testing of the ( minor work )
In a case of an alteration or additions of an ( Existing electrical installation )
Minor Electrical installation Work Certificates .. ( MEIWC )
Sometime it helps to break thing down into Q/As .
P/394 . ( MEIWC ) The Minor Work Certificate is intended to be used for :
( Existing electrical circuit ) Additions ) to an installation that ( do not extend ) .. to the provision of a new-circuit .
( Existing electrical circuit ) Alteration ) to an installation that ( do not extend ) .. to the provision of a new-circuit .
Ask yourself what can it be used for . ??
This Certificate may also be used for the replacement of equipment such as accessories or luminaries
This Certificate may also be used for the replacement of socket-outlets .
This Certificate may also be used for the replacement luminaires . etc
( MEIWC ) ... But Not for the replacement of distribution boards or similar items
C&Gs like to hear this one , Appropriate inspection & testing , however , should always be carried out irrespective of the extent of the work undertaken
Point's to be aware of . ( MEIWC )
P/394 . This Certificate is not appropriate if you requested the contractor to undertake more extensive installation work . for which you should have received an Electrical Installation Certificate . ( EIC )
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Make your Mind up . Certification & Reporting
( EIC )
The Electrical Installation certificate says the work YOU did complies with wiring regulation's . making me a .. ( Safety Certificate 99.9% )
( ECIR )
The main purpose of the Electrcal Installation condition report is to detect so far as is reasonably practicable, and to report , What
likely to impair the safety of an electrical installation ?? ( You can open Pandora's box here )
in theory > Which is not the same as saying the work you have carried out complies with IET Wiring Regulations . ( Reporting )
( EIC )
The Electrical Installation certificate says the work YOU did complies with wiring regulation's . making me a .. ( Safety Certificate 99.9% )
( ECIR )
The main purpose of the Electrcal Installation condition report is to detect so far as is reasonably practicable, and to report , What
likely to impair the safety of an electrical installation ?? ( You can open Pandora's box here )
in theory > Which is not the same as saying the work you have carried out complies with IET Wiring Regulations . ( Reporting )
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Inspection
Regulation's has stated the Facts .
Electrical installation's should always be carried out in a safe manner.
Regulation 611.1 of BS-7671: requires that , Inspection precedes testing and is normally to be done with that part of the installation under inspection disconnected from the supply.
Regulation's has stated the Facts .
Electrical installation's should always be carried out in a safe manner.
Regulation 611.1 of BS-7671: requires that , Inspection precedes testing and is normally to be done with that part of the installation under inspection disconnected from the supply.
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Select Committee finding needs industry sense check
19/03/2014
That is the view of NICEIC & ELECSA in response to parliamentary recommendations for all domestic electricians to have a qualification equivalent to NVQ level 3 within the next five years
19/03/2014
That is the view of NICEIC & ELECSA in response to parliamentary recommendations for all domestic electricians to have a qualification equivalent to NVQ level 3 within the next five years
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Responsibility for earthing ... ( under ESQCR )
Where it is necessary for an installation to be earthed to meet the requirements for safety, it is the consumer"s responsibility to ensure the installation is correctly earthed. This is because, in order to receive a supply, the consumer is required to have an installation that meets the safety requirements of regulations 26(1) and 26(2) of The Electricity Safety, Quality and Continuity Regulations 2002 (ESQCR).
The safety requirements of regulations 26(1) and 26(2) are that the consumer’s installation is so constructed, installed, protected and used or arranged for use so as to prevent, so far as is reasonably practicable, danger or interference with the distributor’s network or with supplies to others. A consumer"s installation that complies with BS 7671 is deemed to meet these requirements.
In practice the electrical contractor, on behalf of the consumer, should ensure that the installation is correctly earthed before issuing an Electrical Installation Certificate .. ( EIC )
Where it is necessary for an installation to be earthed to meet the requirements for safety, it is the consumer"s responsibility to ensure the installation is correctly earthed. This is because, in order to receive a supply, the consumer is required to have an installation that meets the safety requirements of regulations 26(1) and 26(2) of The Electricity Safety, Quality and Continuity Regulations 2002 (ESQCR).
The safety requirements of regulations 26(1) and 26(2) are that the consumer’s installation is so constructed, installed, protected and used or arranged for use so as to prevent, so far as is reasonably practicable, danger or interference with the distributor’s network or with supplies to others. A consumer"s installation that complies with BS 7671 is deemed to meet these requirements.
In practice the electrical contractor, on behalf of the consumer, should ensure that the installation is correctly earthed before issuing an Electrical Installation Certificate .. ( EIC )
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Useful Junk . be fed from a 110V centre tapped transformer .
Extracts .
H&S accepts that a voltage of ( 63.5V to earth ) Three-phase .
( 55V to earth ) single phase , will give protection against severe electrical shock , They therefore recommend that ( Portable tools ) used on construction site(s) . etc
P/61 . Table 41.6 . ( Single-phase ) Uo of 55V , & 63.5V Three-phase
Maximum earth-fault-loop-impedance ( Zs ) Etc . can you get this on any Exams . ??
41.6 :- 32A circuit-breaker ( B ) 32 x 5 = 160A ... Rating / Current .. ( 55V ) ÷ 160A = 0.34Ω , ( 63.5V ) ÷ 160A = 0.396875Ω . 0.40
:- 40A circuit-breaker ( C ) 40 x 5 = 400A ... Rating / Current .. ( 55V ) ÷ 400A = 0.1375Ω , 0.14Ω , ( 63.5V ) ÷ 400A = 0.15875Ω . 0.16
Explanatory note under the table referring to Appendix 14. Note that this appendix is " Informative ", therefore guidance rather than a regulation.
Reduced Low Voltage Systems .
Earth fault loop impedance values for this system may be taken from Table 41.6 of the regulations
Extracts .
H&S accepts that a voltage of ( 63.5V to earth ) Three-phase .
( 55V to earth ) single phase , will give protection against severe electrical shock , They therefore recommend that ( Portable tools ) used on construction site(s) . etc
P/61 . Table 41.6 . ( Single-phase ) Uo of 55V , & 63.5V Three-phase
Maximum earth-fault-loop-impedance ( Zs ) Etc . can you get this on any Exams . ??
41.6 :- 32A circuit-breaker ( B ) 32 x 5 = 160A ... Rating / Current .. ( 55V ) ÷ 160A = 0.34Ω , ( 63.5V ) ÷ 160A = 0.396875Ω . 0.40
:- 40A circuit-breaker ( C ) 40 x 5 = 400A ... Rating / Current .. ( 55V ) ÷ 400A = 0.1375Ω , 0.14Ω , ( 63.5V ) ÷ 400A = 0.15875Ω . 0.16
Explanatory note under the table referring to Appendix 14. Note that this appendix is " Informative ", therefore guidance rather than a regulation.
Reduced Low Voltage Systems .
Earth fault loop impedance values for this system may be taken from Table 41.6 of the regulations
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P/17 . Regulation 131.5:
‘Conductors other than live conductors, and any other parts intended to carry a fault current, shall be capable of carrying that current without attaining an excessive temperature. Electrical equipment, including conductors, shall be provided with mechanicalprotection against electromechanical stresses of fault currents as necessary to prevent injury or damage to persons, livestock or property.
Note : For live conductors, compliance with Regulation 131.4 assures their protection against overcurrents caused by faults.’
P/17 . Regulation 131.4:
‘ Persons and livestock shall be protected against injury, and property shall be protected against damage, due to excessive temperatures or electromechanical stresses caused by any overcurrents likely to arise in live conductors.’
Types of fault current
There are two types of fault current: short-circuit current and earth fault current, as referred to in the following definitions from Part 2 of BS 7671:
P/34 . ‘ Short-circuit current. An overcurrent resulting from a fault of negligible impedance between live conductors having a difference in potential under normal operating conditions.’
P26 . ‘ Earth fault current. A current resulting from a fault of negligible impedance between a line conductor and an exposed-conductive-part or a protective conductor.’
‘Conductors other than live conductors, and any other parts intended to carry a fault current, shall be capable of carrying that current without attaining an excessive temperature. Electrical equipment, including conductors, shall be provided with mechanicalprotection against electromechanical stresses of fault currents as necessary to prevent injury or damage to persons, livestock or property.
Note : For live conductors, compliance with Regulation 131.4 assures their protection against overcurrents caused by faults.’
P/17 . Regulation 131.4:
‘ Persons and livestock shall be protected against injury, and property shall be protected against damage, due to excessive temperatures or electromechanical stresses caused by any overcurrents likely to arise in live conductors.’
Types of fault current
There are two types of fault current: short-circuit current and earth fault current, as referred to in the following definitions from Part 2 of BS 7671:
P/34 . ‘ Short-circuit current. An overcurrent resulting from a fault of negligible impedance between live conductors having a difference in potential under normal operating conditions.’
P26 . ‘ Earth fault current. A current resulting from a fault of negligible impedance between a line conductor and an exposed-conductive-part or a protective conductor.’
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Useful junk .
A cooker control unit is an assembly primarily intended for controlling the supply of electricity to a cooker. It also incorporates a switched socket-outlet for the electrical supply to other electrical appliances. The product standard for cooker control units is BS-4177:1992 - ( P/278 ) Specification for cooker control units. .. Table 53.4.
Table 53.4 of BS-7671:
permits the main switch of a cooker control unit to act as a means of isolation. As for any device used to provide isolation, a cooker control unit should be clearly identified by position or durably marked to indicate the circuit it isolates (Regulation 537.2.2.6 refers). The cooker control unit should be labelled with the word ‘ COOKER ’ adjacent to the main switch that controls the supply to the cooker. Similarly, markings are required such that the ‘ ON ’ and/or ‘ OFF ’ positions of the main switch can be identified.
A cooker control unit is an assembly primarily intended for controlling the supply of electricity to a cooker. It also incorporates a switched socket-outlet for the electrical supply to other electrical appliances. The product standard for cooker control units is BS-4177:1992 - ( P/278 ) Specification for cooker control units. .. Table 53.4.
Table 53.4 of BS-7671:
permits the main switch of a cooker control unit to act as a means of isolation. As for any device used to provide isolation, a cooker control unit should be clearly identified by position or durably marked to indicate the circuit it isolates (Regulation 537.2.2.6 refers). The cooker control unit should be labelled with the word ‘ COOKER ’ adjacent to the main switch that controls the supply to the cooker. Similarly, markings are required such that the ‘ ON ’ and/or ‘ OFF ’ positions of the main switch can be identified.
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Q/As . C&Gs . Which of the following features should test probe to GS-38 have .
- Have finger guards ... barriers/guards
- Be rated at 200V a.c.
- Have exposed tips of 4mm or more
- Be coloured identically
The Electricity at Work Regulations 1989 require those in control of part or all of an electrical system to ensure that it is safe to use and that it is maintained in a safe condition.
The most important features that are relevant for electrical test equipment for use by electrically competent people are as follows
(a) Equipment should be, so far as reasonably practicable:
(i) constructed
(ii) maintained
(iii) used in a way to prevent danger .. being responsibly for your own Actions . competent person
It summarises the main issues to be borne in mind when carrying out electrical testing.
(b) No live working unless:
(i) it is unreasonable to work dead
(ii) it is reasonable to work live
(iii) suitable precautions are taken to prevent injury .. being responsibly for your own Actions . competent person
The probes
Electrical test equipment for use by electricians
(i) have finger barriers or are shaped to ( guard ) against inadvertent hand contact with the live conductors under test;
(ii) are insulated to leave an exposed metal tip not exceeding ( 4mm ) measured across any surface of the tip.
Where practicable it is strongly recommended that this is reduced to ( 2mm ) or less, or that spring loaded retractable screened probes are used;
( 4mm ) Dead testing . making contact with accessories .
( 2mm ) Live testing . " Hand's "
Probes can be provided with a variety of shapes of tip to allow access to the different types of contact.
should have suitable high breaking capacity (hbc), sometimes known as hrc, fuse, or fuses, with a low current rating (usually not exceeding 500mA), or a current-limiting resistor and a fuse.
(ii) are coloured so that one lead can be easily distinguished from the other
(vi) do not have accessible exposed conductors other than the probe tips, or have live conductors accessible to a person’s finger if a lead becomes detached from a probe, indicator or instrument when in use. The test lead or leads are held captive and sealed into the body of the voltage detector
The use of test equipment by electricians falls into three main categories
(a) testing for voltage (voltage detection)
forms an essential part of the procedure for proving a system dead before starting work but may also be associated with simple tests to prove the presence of voltage. Items
(b) measuring voltages
(c) measuring current, resistance and (occasionally) inductance and capacitance.
( b & c ) are more concerned with commissioning procedures and fault finding.
(b) No live working unless:
(i) it is unreasonable to work dead
(ii) it is reasonable to work live .. ( fault finding )
(iii) suitable precautions are taken to prevent injury
- Have finger guards ... barriers/guards
- Be rated at 200V a.c.
- Have exposed tips of 4mm or more
- Be coloured identically
The Electricity at Work Regulations 1989 require those in control of part or all of an electrical system to ensure that it is safe to use and that it is maintained in a safe condition.
The most important features that are relevant for electrical test equipment for use by electrically competent people are as follows
(a) Equipment should be, so far as reasonably practicable:
(i) constructed
(ii) maintained
(iii) used in a way to prevent danger .. being responsibly for your own Actions . competent person
It summarises the main issues to be borne in mind when carrying out electrical testing.
(b) No live working unless:
(i) it is unreasonable to work dead
(ii) it is reasonable to work live
(iii) suitable precautions are taken to prevent injury .. being responsibly for your own Actions . competent person
The probes
Electrical test equipment for use by electricians
(i) have finger barriers or are shaped to ( guard ) against inadvertent hand contact with the live conductors under test;
(ii) are insulated to leave an exposed metal tip not exceeding ( 4mm ) measured across any surface of the tip.
Where practicable it is strongly recommended that this is reduced to ( 2mm ) or less, or that spring loaded retractable screened probes are used;
( 4mm ) Dead testing . making contact with accessories .
( 2mm ) Live testing . " Hand's "
Probes can be provided with a variety of shapes of tip to allow access to the different types of contact.
should have suitable high breaking capacity (hbc), sometimes known as hrc, fuse, or fuses, with a low current rating (usually not exceeding 500mA), or a current-limiting resistor and a fuse.
(ii) are coloured so that one lead can be easily distinguished from the other
(vi) do not have accessible exposed conductors other than the probe tips, or have live conductors accessible to a person’s finger if a lead becomes detached from a probe, indicator or instrument when in use. The test lead or leads are held captive and sealed into the body of the voltage detector
The use of test equipment by electricians falls into three main categories
(a) testing for voltage (voltage detection)
forms an essential part of the procedure for proving a system dead before starting work but may also be associated with simple tests to prove the presence of voltage. Items
(b) measuring voltages
(c) measuring current, resistance and (occasionally) inductance and capacitance.
( b & c ) are more concerned with commissioning procedures and fault finding.
(b) No live working unless:
(i) it is unreasonable to work dead
(ii) it is reasonable to work live .. ( fault finding )
(iii) suitable precautions are taken to prevent injury
A
amberleaf
Who come first ?? Plumber / Gas fitter or Electrician .
Electricity was manly used on street lighting for a replacement for ( Gas ) only later did it gain widespread use in households . Etc
the next Q , So who is ( JPEL/64 )
& how is Harmonisation achieved . ?
The UK Nation Committee responsible for BS-7671: is JPEL/64
J ) joint IET/BSI Committee
P ) Power
EL ) Electrical
64 ) IEC designation for committees dealing with low-voltage electrical installation(s)
Regulation's P/2 . ( JPEL/64 )
Electricity was manly used on street lighting for a replacement for ( Gas ) only later did it gain widespread use in households . Etc
the next Q , So who is ( JPEL/64 )
& how is Harmonisation achieved . ?
The UK Nation Committee responsible for BS-7671: is JPEL/64
J ) joint IET/BSI Committee
P ) Power
EL ) Electrical
64 ) IEC designation for committees dealing with low-voltage electrical installation(s)
Regulation's P/2 . ( JPEL/64 )
A
amberleaf
Q/As , State the three areas : of reasonability to be recorded on the Electrical Installation Certificate . ( EIC )
The person reasonable for the Design .
The person reasonable for the Construction .
The person reasonable for the Verification . .. Inspection & Testing .
Initial verification . 2.1.
GN-3 . P/15 .
Appx 6 . it is important to recognise the responsibilities of the signatories for the Design . Construction & Verification .
While the inspector is responsible for verifying aspects of both design & construction , he/she cannot & is not meant to absolve responsibility for these elements ; indeed
This is why the inspector carries out the inspection & testing .... so far is reasonably practicable .
recap : GN-3 . P/16 ... Certificate(s) 2.2.
Appendix 6 of BS-7671: contains three model forms for the ( initial certification ) of a new installation
an addition or alteration to an Existing installation
• Multiple signature ( EIC )
• Single signature ( EIC )
• Minor ( MEIWC)
Multiple signature ( EIC )
allows different persons to sign for design , construction , inspection & testing . refer
Single signature ( EIC )
Where design , construction , inspection & testing are the responsibility of one person, a certificate with a single signature may replace the .. multiple signature
Minor ( MEIWC)
This certificate is to be used only for , ( minor work ) that do not include the provision of a new circuit . refer
The person reasonable for the Design .
The person reasonable for the Construction .
The person reasonable for the Verification . .. Inspection & Testing .
Initial verification . 2.1.
GN-3 . P/15 .
Appx 6 . it is important to recognise the responsibilities of the signatories for the Design . Construction & Verification .
While the inspector is responsible for verifying aspects of both design & construction , he/she cannot & is not meant to absolve responsibility for these elements ; indeed
This is why the inspector carries out the inspection & testing .... so far is reasonably practicable .
recap : GN-3 . P/16 ... Certificate(s) 2.2.
Appendix 6 of BS-7671: contains three model forms for the ( initial certification ) of a new installation
an addition or alteration to an Existing installation
• Multiple signature ( EIC )
• Single signature ( EIC )
• Minor ( MEIWC)
Multiple signature ( EIC )
allows different persons to sign for design , construction , inspection & testing . refer
Single signature ( EIC )
Where design , construction , inspection & testing are the responsibility of one person, a certificate with a single signature may replace the .. multiple signature
Minor ( MEIWC)
This certificate is to be used only for , ( minor work ) that do not include the provision of a new circuit . refer
A
amberleaf
Q/As 2394 , State what must be recorded on the Electrical Installation Certificate regarding the original electrical installation . ??
the contractor or other person reasonable for the new work . or a person authorised to act on their behalf , shall record on the Electrical Installation Certificate , or the Minor Electrical Installation Work Certificate , any defects found , so far is reasonably practicable in the existing installation BS-7671: 633.2.
the contractor or other person reasonable for the new work . or a person authorised to act on their behalf , shall record on the Electrical Installation Certificate , or the Minor Electrical Installation Work Certificate , any defects found , so far is reasonably practicable in the existing installation BS-7671: 633.2.
A
amberleaf
P/391 . Description and Extent of Installation ... ( EIC )
Describe the extent and limitation of the certificated work. Tick as appropriate, the box for either
New installation
Addition to an existing installation
Alteration to an existing installation
Signatories to the ( EIC ) Electrical Installation Certificate . ( 3 or 1 person ) Signatories
Designer .
Constructor .
Inspector .
Describe the extent and limitation of the certificated work. Tick as appropriate, the box for either
New installation
Addition to an existing installation
Alteration to an existing installation
Signatories to the ( EIC ) Electrical Installation Certificate . ( 3 or 1 person ) Signatories
Designer .
Constructor .
Inspector .
A
amberleaf
Periodic Inspection .. ( EICR )
for an Electrical Installation (BS 7671: 2011)
A report on the condition of an Existing electrical installation. " details of the Visual inspection "
Electrical Installation Certificate (BS 7671: 2011)
For initial verification of New electrical installations, including alterations and additions to existing installations, where the contractor has carried out the design, construction and inspection & testing. .. Domestic installation , Single Signatory
in Exams' : Stay focus
► Existing electrical installation .. ( EICR ) Report
► New electrical installations .. ( EIC )
for an Electrical Installation (BS 7671: 2011)
A report on the condition of an Existing electrical installation. " details of the Visual inspection "
Electrical Installation Certificate (BS 7671: 2011)
For initial verification of New electrical installations, including alterations and additions to existing installations, where the contractor has carried out the design, construction and inspection & testing. .. Domestic installation , Single Signatory
in Exams' : Stay focus
► Existing electrical installation .. ( EICR ) Report
► New electrical installations .. ( EIC )
A
amberleaf
On rant mode .
Earth fault loop impedance .
Determination of external (at the origin)
Methods of determining ( Ze ) " The pit falls "
Calculation ... calculation does not verify that the intended means of earthing is in fact present
Therefore, where ( Ze ) is determined by calculation, measurement of ( Ze ) is still required before the installation is put into service .
Enquiry
Regulation 28 of the Electricity Safety, Quality and Continuity Regulations 2002 (ESQCR) requires a distributor providing a low voltage supply to an installation to declare information, including the following, concerning that supply, on request:
- the maximum value of ( Ze )
- the maximum value of prospective short-circuit current (Isc) at the origin .. Regulations P/38 . ( Isc - short-circuit-current )
The designer of the installation must obtain the above information by direct enquiry ... ( DNO - Distribution Network Operator )
Typical maximum values of ( Ze ) & (Isc) declared by ( DNO ) for 230V single-phase and 230/400 V three-phase supplies are shown in the following table:
Characteristic : External earth-fault-loop-impedance ( Ze )
O.S.G. P/11. Type of system :- TN-S .. Maximum value 0.80Ω
O.S.G. P/11. Type of system :- TN-C-S ( Protective Multiple Earthing ) Maximum value 0.35Ω
Type of system :- TT- .. Important . The résistance of the installation earth-electrode & earthing conductor must be ( Added ) to this value which is for the source earth-electrode only .
recap . O.S.G. P/11. TT - arrangement ( 21Ω ) is the usual stated ( Maximum résistance ) of the ( DNO ) earth-electrode at the supply transformer .
The résistance of the consumer's installation earth-electrode should be as low as practicable & a value exceeding ( 200Ω ) may not be stable .
Measurement .
The measurement will verify that a means of earthing is present and also confirm that ( Ze ) is within the expected range.
Earth fault loop impedance .
Determination of external (at the origin)
Methods of determining ( Ze ) " The pit falls "
Calculation ... calculation does not verify that the intended means of earthing is in fact present
Therefore, where ( Ze ) is determined by calculation, measurement of ( Ze ) is still required before the installation is put into service .
Enquiry
Regulation 28 of the Electricity Safety, Quality and Continuity Regulations 2002 (ESQCR) requires a distributor providing a low voltage supply to an installation to declare information, including the following, concerning that supply, on request:
- the maximum value of ( Ze )
- the maximum value of prospective short-circuit current (Isc) at the origin .. Regulations P/38 . ( Isc - short-circuit-current )
The designer of the installation must obtain the above information by direct enquiry ... ( DNO - Distribution Network Operator )
Typical maximum values of ( Ze ) & (Isc) declared by ( DNO ) for 230V single-phase and 230/400 V three-phase supplies are shown in the following table:
Characteristic : External earth-fault-loop-impedance ( Ze )
O.S.G. P/11. Type of system :- TN-S .. Maximum value 0.80Ω
O.S.G. P/11. Type of system :- TN-C-S ( Protective Multiple Earthing ) Maximum value 0.35Ω
Type of system :- TT- .. Important . The résistance of the installation earth-electrode & earthing conductor must be ( Added ) to this value which is for the source earth-electrode only .
recap . O.S.G. P/11. TT - arrangement ( 21Ω ) is the usual stated ( Maximum résistance ) of the ( DNO ) earth-electrode at the supply transformer .
The résistance of the consumer's installation earth-electrode should be as low as practicable & a value exceeding ( 200Ω ) may not be stable .
Measurement .
The measurement will verify that a means of earthing is present and also confirm that ( Ze ) is within the expected range.
A
amberleaf
it is the Basic's that let you down .
Read GN-3 . Everything you need for the exams can be found in it.
You will need to know GN-3 inside out
You will also need to know the Regulations inside out
2394 : Introduction
Earth fault loop impedance ( Zs ) is a characteristic vital to the protective measure Automatic Disconnection of Supply (ADS), which is used for fault protection in most electrical installations.
Each circuit is required not to exceed the limiting (or maximum) value permitted by BS-7671:2011:
The meaning of earth fault loop impedance ?
( known as the earth-fault-loop ) .. comprises
GN-3 . P/52 . &
R/P26 .. refer
Earth fault loop impedance ( Zs ) is the impedance of the intended path of an earth fault current starting and ending at the point of the fault to earth.
This impedance is denoted by the symbol ( Zs )
Read GN-3 . Everything you need for the exams can be found in it.
You will need to know GN-3 inside out
You will also need to know the Regulations inside out
2394 : Introduction
Earth fault loop impedance ( Zs ) is a characteristic vital to the protective measure Automatic Disconnection of Supply (ADS), which is used for fault protection in most electrical installations.
Each circuit is required not to exceed the limiting (or maximum) value permitted by BS-7671:2011:
The meaning of earth fault loop impedance ?
( known as the earth-fault-loop ) .. comprises
GN-3 . P/52 . &
R/P26 .. refer
Earth fault loop impedance ( Zs ) is the impedance of the intended path of an earth fault current starting and ending at the point of the fault to earth.
This impedance is denoted by the symbol ( Zs )
A
amberleaf
Note : Earth fault loop impedance .
Consumer unit at the Origin . Zs = Ze + ( R[SUP]1[/SUP] + R[SUP]2[/SUP] )
Larger installations with consumer units , or distribution boards not at the Origin . Zs = Zdb + ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) in Exams , indicate Sub mains somewhere
GN-3 . P/53 . ( Zdb ) as , strictly speaking , this value is not external to the installation . Thus , the formula is denoted .
Consumer unit at the Origin . Zs = Ze + ( R[SUP]1[/SUP] + R[SUP]2[/SUP] )
Larger installations with consumer units , or distribution boards not at the Origin . Zs = Zdb + ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) in Exams , indicate Sub mains somewhere
GN-3 . P/53 . ( Zdb ) as , strictly speaking , this value is not external to the installation . Thus , the formula is denoted .
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