Paper 4 Flashcards
State three practical situations where BS 7671 requires the use of an RCD with a maximum residual operating current of 30 mA.
1) Cables buried in wall less than 50 mm etc
2) Socket outlets rated at 20A or less for use by ordinary persons
3) Bathrooms
Any other suitable answer
1b tests to establish prospective fault current are to be carried out at a main distribution board, using a two lead, digital, prospective fault current tester, with only one range setting (no selector control knob) and a maximum working range of 250v. State;
i) The two tests to be carried out at the origin of the installation in order to determine the prospective fault current.
ii) Between Which terminals in the board would the tests be conducted, if it were a single phase board
iii) what value would be recorded on the generic schedule of test results, if this was a single phase installation.
iv) Between Which terminals in the board would the tests be conducted, if it were a three phase board
v) what value would be recorded on the generic schedule of test results, if this was a three phase installation.
vi) the condition which must be verified once the recorded value above is obtained.
i) PeFC and PSCC
ii) line to earth and Line to neutral
iii) The highest of the two readings above
iv) PeFC; Line to earth is noted but not used.
PSCC = Line 1 to neutral, line 2 to neutral and line 3 to neutral
v) Double the highest PSCC measured
vi) Breaking capacity of protective devices (fuse or circuit breaker)
1c Having arrived at an installation to conduct a periodic inspection; if the supply has been removed by the distributor,
i) can you complete the periodic inspection
ii) explain your reason for the decision
NO
Live testing is an essential part of establishing whether an installation is in a satisfactory condition for continued service, which is the purpose of a periodic inspection.It will be necessary for the live testing to be completed, and therefore for the supply to be available, before an Electrical Installation Condition Report can be issued.
When completing an electrical installation condition report,
2a state the categories of “classification of danger or non compliance” and briefly describe when each code would apply
C1 = immediate danger C2 = potential danger under fault conditions C3 = improvement required non compliances with safety implications
When completing an electrical installation condition report,
2a state the categories of “classification of danger or non compliance” and briefly describe when each code would apply
C1 = immediate danger C2 = potential danger under fault conditions C3 = improvement required non compliances with safety implications
give three different examples of each classification of danger or non compliance (C1, C2, C3)
C1 =
i) Broken face plate allowing access to live parts.
ii) Missing cover to busbar chamber
iii) Damaged cable where part of line conductor can be touched
C2 =
i) High Zs reading
ii) No earthing conductor
iii) No main protective bonding conductor
C3 =
i) Absence of warning labels
ii) Under sized Main protective bonding conductors
iii) Socket outlets for general use, not protected by a rcd providing additional protection but unlikely to supply portable equipment outside
Any other suitable answer
Define what is meant by a “Surge protection Device”
An SPD is a device that is intended to limit transient overvoltages and divert surge currents to earth
Identify two causes of surge currents
Any 2
Lightning strikes
Overvoltages caused by heavy equipment switching off
Overvoltages generated by
Identify three different categories of surge protection device
Type 1, type 2 and type 3
Identify where type 1,2 and 3 SPD’s would be used
Type 1, at the origin of the installation
Type 2, at distribution boards
Type 3, at location of equipment
(See appendix 16)
Name all of the documents that need to be filled after a periodic inspection and test
Electrical installation condition report, generic schedule of test results, condition report inspection schedule.
Who is responsible for recommending the period to the subsequent inspection and tests?
the inspector
State three items of information that are required by a person undertaking the inspection and test of this installation, excluding information contained on diagrams, charts or tables.
Max demand, number and type of live conductors, type of earthing arrangements, nominal voltage, nature of the load current and frequency, pfc at the origin, Ze, type and rating of the over current protective device at the origin.
Any 3 x 1
NB – type of earthing arrangement/type of supply system – only 1 mark if both given.
State three different practical situations that may require the use of the sense of touch during the inspection process.
To detect if something is loose / secure
To detect if something is running hot / overheated etc
To check if a barrier is correctly in place
To gently feel for sharp edges
