C&G 2391-52 flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Electricity at Work Regulations 1989

Statutory regulations applying to electrical systems at work in Great Britain; they require competent persons, safe systems of work and precautions for work on or near live conductors.

BS 7671 non-statutory status

BS 7671 is not law; compliance is accepted as evidence that duties under the Health and Safety at Work etc. Act 1974 and the Electricity at Work Regulations 1989 have been met.

Part P of Building Regulations

Applies to fixed electrical installations in dwellings in England and Wales; notifiable work must be certified by a registered competent person or inspected by building control.

Chapter 61 initial verification

BS 7671 Chapter 61 requires inspection and testing of new work during erection and on completion, before the installation is put into service.

Guidance Note 3

IET Guidance Note 3: Inspection and Testing is the non-statutory companion to BS 7671 Part 6, covering test methods, expected values, sampling and forms.

Three-point proving procedure

Prove the voltage indicator on a proving unit, test all live conductors at the point of work, then prove the indicator again to confirm it still works.

GS38 voltage detector requirements

HSE Guidance Note GS38 specifies two-pole detectors with fused leads, finger barriers, no more than 4 mm exposed tip, rated for the installation's overvoltage category.

Supply characteristics before testing

Establish the earthing system, nominal voltage, external loop impedance or electrode resistance, and prospective fault current before starting inspection and testing.

Instrument calibration and proving

Test instruments need a current calibration certificate, typically within 12 months, and should be proved against a known source before and after use.

EAWR Regulation 14 live work

Work on or near live conductors is permitted only where it is unreasonable in all circumstances to work dead and suitable precautions are taken.

Overvoltage category of instruments

Instruments and leads must be rated for the location, for example CAT III at distribution boards and CAT IV at the origin of an installation.

Purpose of initial verification

Initial verification confirms by inspection and testing that an installation complies with the design and BS 7671 before it is energised for use.

Schedule of Inspections

A BS 7671 Appendix 6 form listing the items to be visually inspected, ticked where satisfactory, with any departures or limitations recorded.

Ring final circuit R1+R2

After cross-connecting line and protective conductor of opposite legs, the resistance measured at each socket should be about one quarter of r1 plus r2.

Nulling continuity test leads

The resistance of the test leads is measured and either nulled on the instrument or subtracted from readings so results are not falsely high.

Insulation resistance pass values

For circuits up to 500 V apply 500 V DC with a minimum of 1 MΩ; for SELV and PELV apply 250 V DC with a minimum of 0.5 MΩ.

Equipment disconnected for IR test

Dimmers, electronic devices, surge protective devices and similar equipment are removed or isolated before insulation resistance testing to prevent damage and false readings.

Investigating low insulation resistance

A result below 1 MΩ fails BS 7671; subdivide the circuit and retest to locate moisture, damaged insulation or a connected load causing the low reading.

80% rule for maximum Zs

Tabulated maximum Zs values assume conductors at 70 °C; measured values at ambient temperature are compared with 80% of the tabulated figure.

Fall of potential electrode test

Two stakes are driven in line with the electrode; the potential stake sits at 62% of the distance to the current stake, and readings are repeated at moved positions.

TT system maximum RA

Earth electrode resistance must not exceed 50 V divided by the RCD rated residual current: 1667 Ω for 30 mA and 500 Ω for 100 mA.

RCD five times test

At five times rated residual current a general RCD to BS EN 61008 or 61009 must operate within 40 ms; the test is repeated at 0° and 180°.

RCD half rated current test

Applying half the rated residual operating current should not operate the RCD; operation at this level indicates an over-sensitive or faulty device.

Type S RCD operating times

Time-delayed Type S RCDs must operate between 130 ms and 500 ms at rated residual current, and between 50 ms and 150 ms at five times that current.

EICR observation codes

C1 means danger present and immediate action required; C2 potentially dangerous and urgent action needed; C3 improvement recommended; FI further investigation required.

Satisfactory condition report

An EICR is satisfactory only when it records no C1, C2 or FI observations; any one of these makes the report unsatisfactory.

Minimum periodic sampling

Periodic inspection typically samples at least 10% of circuits, including all circuits showing defects, and the sample is increased where the installation is poor.

Minor Electrical Installation Works Certificate

Used for minor work that does not extend or alter a circuit; it records the work, test results and the signatures of the designer, installer and tester.

EIC declaration signatures

An Electrical Installation Certificate requires declarations from the designer, constructor and the person responsible for inspection and testing, who may be the same competent person.

High Zs interpretation

A measured Zs above the 80% tabulated maximum suggests a loose termination, long circuit, undersized protective conductor or high external impedance; investigate before condemning.

Communicating a C1 defect

A C1 observation means danger is present; the client must be told immediately and the affected part isolated or otherwise made safe without delay.

Effect of limitations on conclusion

Limitations that prevent inspection of part of the installation must be recorded, and the report must state whether the overall conclusion is affected.