F
firemanowl
I've been having a sort out on the computer and have found some 2391 past papers with answers, the following are questions 1 - 10 short answer and I'll post 11 - 20 in another thread in a bit. Not sure if it's an actual paper or one that has been put together.
City & Guilds 2391-10 Inspection & Testing 1
a) Continuity Test using a low resistance Ohmmeter to determine R2 or (R1+R2).
b) A continuity test using an A.C. Ohmmeter to determine R2.
c) An Earth Fault Loop Impedance test to determine Zs for the circuit fed by the ferrous enclosure.
2 State the effect on the insulation resistance of an installation if:
a) additional circuits are added
b) circuits were disconnected / removed
c) the length of a 6A lighting circuit was extended. (3 marks)
a) the insulation resistance value decreases.
b) the insulation resistance value increases.
c) the insulation resistance value decreases.
3 State:
a) why it is deemed necessary to remove one end of a bonding conductor connection when verifying its’ continuity
b) the instrument used to verify continuity
c) a typical value of resistance when verifying the continuity of bonding conductors. (3 marks)
a)to avoid false or inaccurate reading caused by parallel paths.
b) A Low Resistance D.C. Ohmmeter.
c)Less than 0.05Ω or negligible.
4 State FOUR external influences that you would need to consider during the inspection process. (3 marks)
Any FOUR from; Ambient Temperature, heat, water foreign bodies, corrosion, impact, vibration, flora, fauna, radiation, building use and structure.
5 State why it is necessary to verify the continuity of cpc’s prior to undertaking:
a) polarity tests
b) insulation resistance test
c) earth fault loop impedance test. (3 marks)
It is necessary to verify the continuity of cpc,s to ensure that the earth is present at a particular part of the installation.
a)A ‘dead’ polarity test is achieved by using the cpc as R2 in the Method 1 continuity test. Also, a ‘live’ polarity test is always measured between Live and Earth (cpc).
b)An insulation resistance test requires that we test to an earth as a reference, i.e. L-E, N-E.
c)The cpc (R2) forms part of the earth fault loop impedance path as shown in the formula Zs = Ze + (R1 + R2).
6 State FOUR prerequisite checks that need to be applied prior to undertaking an insulation resistance test. (3 marks)
i) verify that the supply is isolated
ii) any current using equipment is disconnected (loads or lamps removed)
iii) all switches and MCB’s closed and fuses in place
iv) disconnect and voltage sensitive equipment that may be damaged by the test.
7 State THREE types of installation that would be subject to Part 7 of BS 7671:2008. (3 marks)
i) Swimming Pools
ii) Saunas
iii) Marinas (or ANY from BS 7671:2008 Part 7).
8 State FIVE methods of Basic Protection. (3 marks)
i) insulation of live parts
ii) barriers
iii) enclosures
iv) placing out of reach
v) obstacles
9 Name the THREE electrodes used when employing a proprietary tester to measure the resistance of a rod type electrode.
(3 marks)
i)electrode under test
ii)potential electrode
iii)current electrode.
10 State the necessary test to be applied to a non-standard piece of equipment, which has been insulated on-site? (3 marks)
Utilising a ‘Standard Test Finger’ to IP XXB, connect a SELV supply not exceeding 50 V in series with a suitable lamp and connect between the test finger and the live parts inside the enclosure. The protection is satisfactory if the lamp does not light. Accessible top horizontal surfaces should also be tested for protection utilising a ‘Standard Test Wire’ to IP 4X.
