Hi all again. Got my hands on another past paper without answers again so I thought id put it up on here to get some feedback and to help others again.
Q1. List 3 installation details that must be recorded, as identified on a Minor Electrical Installation Works Certificate (3 Marks)
A1.
.Type of earthing arrangement
.Method of fault protection
.Prospective device for modified circuit
Q2. State, for each of the following, if the documents are statutory or non statutory.
a) BS 7671 (1 mark)
b) Guidance Note 3 (1 Mark)
c) Electricity at Work Regulation (1 Mark)
A2.
a) Non Statutory
b) Non Statutory
c) Statutory
Q3. State three items of information, relating to the incoming supply for an electrical installation, that must be recorded on a schedule of test results. (3 Marks)
A3.
.Type of earthing arrangement
.External earth fault loop impedance (Ze)
.Prospective fault current (PFC)
Q4. State three general requirements against which installed equipment must be confirmed when carrying out an initial inspection, as stated in BS7671. (3 Marks)
A4.
.All electrical material and equipment is of the correct type and complies with all relevant British standards
.All parts of the fixed installation are correctly selected and erected
.No parts of the fixed installation are visibly damaged or defective so as to impair safety
Q5. List three non compliances that may be identified during the inspection process using the sense of touch. (3 Marks)
A5.
.Boxes and enclosures not securely fixed
.Terminations of conductors arnt tight
.Conductors overheating because they are underrated
Q6. A test for continuity of protective conductors is required as part of a initial verification on an installation. State
a)What must be confirmed when testing a radial socket-outlet circuit (1 Marks)
b)How the recorded measured value is to be confirmed as satisfactory (1 Mark)
c)One factor that may affect the measured values obtained (1 Mark)
A6.
a)Polarity
b)Added to Ze (Zs=Ze + (R1+R2)) then compared to amended BS7671 values
c)Ambient temperature
Q7. A test is carried out to obtain an R1+R2 value at the furthest point of a two-way lighting circuit. Explain why it is necessary to operate the two way switching during the test. (3 Mark)
A7. To confirm polarity and to ensure there are no breaks in the switch wiring
Q8. A test for continuity of ring final circuit conductors is to be carried out on a circuit containing no spurs. State.
a)the expected value of R1+R2 for the circuit if the resistance of the line, neutral and cpc loops are 0.2ohms, 0.2ohms and 0.33 ohms respectively. (2 Mark)
b)The effect on the circuit R1+R2 value if a non fused spur supplying a socket-outlet was added to the circuit (1 Mark)
A8.
a)R1+R2 = (r1+r2)/4 = (0.2+0.33)/4 = 0.13
b)It would increase R1+R2 as the cabling supplying the spur would be added.
Q9. Following repairs to a motor and before its reconnection, an insulation resistance test is to be carried out on a securely isolated three phase motor circuit. State
a)The two tests to be carried out in order to complete the schedule of test results in BS7671
(2 Marks)
b)How the cable between the motor starter and the motor maybe included in the test in a)
(1 Marks)
A9.
a)Between live conductors (Live/Live) and between Live conductors and Earth (Live/Earth)
b)Link across the motor starter
Q10. An insulation resistance test is to be carried out to confirm electrical separation of one circuit from another circuit contained in the same conduit. State
a)test connections required to confirm electrical separation (2 Marks)
b)minimum acceptable value of insulation resistance (1 Mark)
A10.
a) Between separated circuit conductors connected together and other circuit conductors connected together. Between separated circuit conductors and earth
b) Tested at 500V DC and greater than 1Mohm
Q11. State three methods of providing protection against electric shock for a 16A socket-outlet circuit installed on a construction site (3 Marks)
A11.
.Insulation of live parts
.Automatic disconnection of supply
.Additional protection via a 30mA residual current device
Q12. State the IP codes for enclosures that provide protection against a
a)12.5mm diameter sphere (1 Mark)
b)British standard finger test only (1Mark)
c)1mm Diameter wire (1 Mark)
A12.
a)IP2X
b)IPXXB
c)IP4X
Q13. State the test carried out to confirm that
a)the outer screw contact of an Edison screw type lamp holder is connected to the neutral conductor (1 Mark)
b)a lighting circuit protective device will disconnect within 0.4s in the event of an earth fault
(1 Mark)
c)a fuse protecting an electrical installation will operate safely in the event of a short circuit fault
(1 Mark)
A13.
a)Polarity test
b)Earth fault loop impedance
c)Prospective fault current
Q14. A test is to be carried out on a earth electrode, using an earth electrode resistance tester. State
a)Why it is necessary to take readings with the centre electrode in three different positions (1 Mark)
b)How to determine the electrode resistance if the three readings in a) above are similar in value
(1 Mark)
c)Another type of test instrument that may be used to carry out this test when the electrode being tested forms part of a TT system and is protected by an RCD (1 Mark)
A14.
a)To ensure the resistance area doesn’t overlap
b)Take the mean of the three readings
c)Earth fault loop impedance tester
Q15. State, for each of the following, the type of system used for public supplies thathas an earth return path, external to the installation consisting of,
a)a PEN conductor (1 Mark)
b)the general mass of earth (1 Mark)
c)separate neutral and protective conductors (1 Mark)
A15.
a) TN-CS
b) TT
c) TN-S
Q16. An earth loop impedance test is to be carried out on a healthy ring final circuit consisting of nine socket-outlets connected directly in the ring. State the,
a)instrument to be used (1 Mark)
b)pattern of test results when carrying out the test at each socket outlet around the ring (1 Mark)
c)value to be recorded on the schedule of test results (1 Mark)
A16.
a)Earth loop impedance tester
b)Should increase slightly as you move closer to the middle of the ring and then decrease again
c)The highest reading taken
Q17. State,
a)one condition where BS7671 requires a 30mA RCD to provide additional protection to a circuit in a office (1 Mark)
b)the maximum permitted disconnection time of the RCD in a) above, when a current of 150mA flows to earth (1 Mark)
c)The maximum permitted earth loop impedance of a circuit forming part of a TT system if it is protected by a 300mA RCD (1 Mark)
A17.
a) Any socket outlet up to 20A that may be used by ordinary persons for general use
b) 40ms
c) Ra = 50/300mA = 167ohms
Q18. State the,
a)effect on the value of prospective fault current when it is measured within the installation at increasing distances from the origin (1 Mark)
b)two types of fault that must be considered on a single phase TN-S system when considering an installation PFC. (2 Mark)
A18.
a)It will decrease
b)Prospective earth fault current and Prospective short circuit current
Q19. State three factors that may affect the measured earth fault loop impedance value of a circuit, excluding final circuit conductor length and cross sectional area. (3 Mark)
A19.
.Ambient temperature
.Electrical Loading
.Being surrounded by insulation
Q20. State the maximum permitted percentage voltage drop for each of the following circuits supplied directly from a public low voltage distribution system.
a)230V lighting circuit (1 Mark)
b)Three-phase 400V motor circuit (1 Mark)
c)Distribution circuit supplying a single phase distribution board (1 Mark)
A20.
a)3%
b)5%
c)5%
The only thing I think im not sure about is in question 10 would you include a test between the separated circuits exposed conductive parts and the cpcs and exposed conductive parts of other circuit?
Thanks
r10ley