UNDERTAKING
The intention of this document is to provide an undertaking, the requirements of which are set down in the:
Electricity at Work Regulation 1989
British Standards No. 7671 2008 as amended
I.E.E. Guidance Note No. 3 2nd Edition Part 2
SCOPE OF WORK
The scope of the work is to give a professional opinion of the installations condition by carrying out visual inspections and instrument test of those parts of the Fixed Wiring Installation which are accessible.
The test and inspections would comprise:
 Characteristics
of supply at the origin of the installation.
Visual
inspection.
C.P.C.
continuity test.
Ring
Circuit Continuity
Insulation
resistance test.
Polarity
check.
Earth
fault loop impedance test.
Prospective
short circuit currents.
Operation
of residual current devices.
ASSESSMENT OF GENERAL CHARACTERISTICS (Reg 301)
301.1 An assessment shall be made of the following characteristics of the installation in accordance with the chapters indicated:
The purpose for which the installation is intended to be used, its general structure and its supplies (Chapter 31).
The external influences to which it is exposed. (Chapter 32).
The compatibility of its equipment. (Chapter 33).
Its maintainability. (Chapter 34).
Recognised safety services. (Chapter 35).
Assessment for continuity of service. (Chapter 36).
SUPPLY (Reg. 313.1)
The characteristics of supply at the origin of the installation would be determined and would include the following:
Nominal voltage.
Nature of current and frequency.
Prospective short circuit current.
External earth fault loop impedance. (Ze)
Type of rating of supplier's overcurrent protective device.
INSPECTION
Inspection comprising careful scrutiny of every installation, where required, shall be carried out in accordance with the requirements of this chapter.
The safety of the persons and livestock against the effects of electric shock and burns, in accordance with Regulations 120.1, and
Protection against damage to property by fire and heat arising from an installation defect, and
The identification that the installation is not damaged or deteriorated so as to impair safety, and
On a sampling basis, check that conductors are readily identified in accordance with Reg. 514.3, and tables 51.
No signs of overloading of conductors and accessories.
On a sampling basis, check correct connection of socket outlets and Lamp holders including: -
(a)
Protective conductors installed and sleeved green/yellow.
(b) Protective conductor installed between back box
and Socket earth terminal.
(c)
No sharp edges that may cause mechanical damage to Cable
insulation.
(d)
No undue mechanical strain on cables.
(e)
Conductors readily identifiable.
(f)
No excessive removal of insulation.
Presence
of fire barriers including:
(a)
Trunking is constructed of non-combustible material
and covers are securely fixed.
(b)
Fire barriers are fitted in vertical trunking and rising
bus-bar systems.
(c)
Holes surrounding cable, conduit and trunking are sealed
to an Appropriate degree of fire resistance.
Presence
of appropriate devices for isolation and switching as
follows:
(a)
Isolation.
(b) Switching off for mechanical maintenance.
(c) Emergency switching (where applicable).
(d) Functional switching.
Choice
and setting of protective devices to include:-
(a)
Fuses/MCB's/Circuit breakers are of correct type and
rating for intended use.
(b)
Tabulated current rating of cables is equal to or greater
than Setting of protection device.
Labelling
of circuits, fuses, switches, distribution boards, terminals
etc. to indicate its purpose.
Presence
of danger notices and other warning notices such as:
(a)
Warning notices on equipment where 250 volts is exceeded
(Reg. 514.10.1).
(b)
Warning notices on earthing and bonding conductors stating
"Safety Electrical Connection - Do Not Remove".
(Reg. 514.13.1).
Identifying
dangers, which might arrive during instrument testing.
Flexible
cables and cords (Reg 611.3). Where a flexible cable
or cord forms part of the fixed wiring installation,
the inspection should include:
(1) Examination of the cable or cord for damage or defects.
(2) Examination of the terminations and anchorage's for damage or defects.
(3) The correctness of its installation with regard to additional mechanical protection, heat resistant sleeving, etc.
Enclosures and Mechanical Protection (Reg. 612.4.5). The enclosure and mechanical protection of all electrical apparatus and equipment should be inspected to ensure that their condition remains adequate for type of protection needed.
External influences. (Reg. 611.3(xiii)) Note should be made of any known changes in external influences, building structure, and alterations or additions which may have affected the suitability of the wiring for its present load and method of
installation.
Note should be made of any alterations for additions of an irregular nature to the installation. If unsuitable material has been used the Report should indicate this together with reference to any evident faulty workmanship or design.
Presence of diagrams, instructions and similar information (Reg. 611.3(xvi)). Where sample inspections are carried out, these should include removal of luminaire covers, switch plates, socket outlets and covers of equipment.
It is neither practicable nor possible to inspect all parts of the Installation and a sampling process would be employed, normally in the order of 10% of all accessories, lighting fittings and control equipment.
The installation would not be dismantled in any other way other than opening equipment covers and the building structure would not be disturbed. This means that concealed cables and equipment would not be inspected.
TESTING (Reg. 612)
CONTINUITY OF PROTECTIVE CONDUCTORS INCLUDING MAIN AND SUPPLEMENTARY EQUIPOTENTIAL BONDING(Reg. 612.2.1)
A continuity test shall be made. It is recommended that the test be carried out with a supply having a no-load voltage between 4v and 24v d.c. or a.c. and a short circuit current of not less than 200mA.
The results of C.P.C. continuity tests shall be recorded in ohms.
CONTINUITY OF RING FINAL CONDUCTORS (Reg 612.2.2)
A test shall be made to verify the continuity of each conductor, including the protective conductor, of every ring final circuit.
INSULATION RESISTANCE (Reg. 612.3)
612.3.1 The insulation resistance shall be measured between live conductors and the protective conductor connected to the earthing arrangement. Where appropriate during this measurement, line and neutral conductors may be connected together.
612.3.2 The insulation resistance measured with the test voltages indicated in Table 61 shall be considered satisfactory if the main switchboard and each distribution circuit tested separately, with all its final circuits connected but with current using equipment disconnected, has an insulation resistance not less than the appropriate value given in Table 61.
Where surge protection devices (SPD) or other equipment are likely to influence the verification test, or be damaged, such equipment shall be disconnected before carrying out the insulation resistance test. Where it is not reasonable practicable to disconnect such equipment (e.g. fixed socket outlet incorporating an SPD) the test voltage for the particular circuit may be reduced to 250v d.c., but the insulation resistance shall have a value of at least 1MOhms
PROTECTION BY SELV (Reg. 612.4.1)
The separation of the live parts from those of other circuits and from Earth, according to Section 414, shall be confirmed by a measurement of insulation resistance. The resistance values obtained shall be in accordance with Table 61.
PROTECTION BY PELV (Reg. 612.4.2)
The separation of the live parts from other circuits, according to Section 414, shall be confirmed by a measurement of the insulation resistance. The resistance values obtained shall be in accordance with Table 61.
PROTECTION BY ELECTRICAL SEPARATION (Reg. 612.4.3)
The separation of the live parts from those of other circuits and from Earth, according to Section 413, shall be confirmed by a measurement of the insulation resistance. Values obtained shall be in accordance with Table 61. In the case of electrical separation with more than one item of current-using equipment, either by measurement or by calculation, it shall be verified that in case of two coincidental faults with negligible impedance between different line conductors and either the protective bonding conductor or exposed-conductive parts connected to it, at least one of the faulty circuits shall be disconnected. The disconnection time shall be in accordance with that for the protective measure automatic disconnection of supply in a TN system.
FELV Functional extra-low voltage circuits (Reg. 612.4.4)
Functional extra-low voltage circuits shall meet all the test requirements for low voltage circuits.
BASIC PROTECTION BY A BARRIER OR AN ENCLOSURE PROVIDED DURING ERECTION (Reg. 612.4.5)
Where basic protection is intended to be afforded by a barrier or an enclosure provided during erection in accordance with Regulation 416.2, it shall be verified by test that each barrier or enclosure affords a degree of protection not less than IP2X or IPXXB, or IP4X or IPXXD as appropriate, where that regulation so requires.
INSULATION RESISTANCE/IMPEDANCE OF FLOORS AND WALLS (Reg. 612.5)
Where it is necessary to comply with the requirements of Regulation 418.1, at least three measurements shall be made in the same location, one of these measurements being approximately 1m from any accessible extraneous-conductive-part in the location. The other two measurements shall be made at greater distances. The measurement of resistance/impedance of insulating floors and walls is carried out with the system voltage to Earth at nominal frequency. The above series of measurements shall be repeated for each relevant surface of the location.
POLARITY (Reg. 612.6)
A test of polarity would be carried out to verify that fuses and single pole control devices are connected in the phase conductor only.
The polarity on lighting circuits and equipment would be carried out on a 10% random sampling basis. The polarity on socket outlets on a 100% basis.
EARTH ELECTRODE RESISTANCE (Reg. 612.7)
Where the earthing system incorporates an earth electrode as part of the installation, the electrode resistance to Earth shall be measured.
PROTECTION BY AUTOMATIC DISCONNECTION OF THE SUPPLY (Reg. 612.8)
Where RCDs are applied also for protection against fire, the verification of the conditions for protection by automatic disconnection of the supply may be considered as satisfying the relevant requirements of Chapter 42.
612.8.1 General
a) TN system
1) Measurement of the earth fault loop impedance (see Regulation 612.9)
2) Verification of the characteristics and/or the effectiveness of the associated protective device. This verification shall be made:
- For overcurrent protective devices, by visual inspection (i.e. short-time or instantaneous tripping setting for circuit breakers, current rating and type for fuses)
- For RCDs, by visual inspection and test. The effectiveness of automatic disconnection of supply by RCDs shall be verified using suitable test equipment according to BS EN 61557-6 (See Regulation 612.1) to confirm that the relevant requirements in Chapter 41 are met.
b) TT system
1) Measurement of the resistance of the earth electrode for exposed conductive parts of the installation (see Regulation 612.7)
2) Verification of the characteristics and/or the effectiveness of the associated protective device. This verification shall be made:
- For overcurrent protective devices, by visual inspection (i.e. short-time or instantaneous tripping setting for circuit breakers, current rating and type for fuses)
- For RCDs, by visual inspection and test. The effectiveness of automatic disconnection of supply by RCDs shall be verified using suitable test equipment according to BS EN 61557-6 (See Regulation 612.1) to confirm that the relevant requirements in Chapter 41 are met.
The disconnection times required by Chapter 41 shall be verified.
c) IT system
Compliance with Regulation 411.6 shall be verified by calculation or by measurement of the current Id in case of a first fault at the line conductor or at the neutral. Where conditions that are similar to conditions of a TT system occur, in the event of a second fault in another circuit (see Regulation 411.6.4(ii)), verification is made as for a TT system (see point b) of this regulation.
EARTH FAULT LOOP IMPEDANCE (Reg. 612.9)
Measurements would be made of the earth fault loop impedance at the main intake, all switchboards, distribution boards and bus-bar systems.
On lighting circuits 10% (on a random basis) of all luminaries, with a minimum of one luminaire, preferably the furthest one from the distribution-board, for each circuit of the installation.
The earth fault loop impedance would be measure at all accessible 13 amp General purpose socket outlets and fixed equipment where visible. (See over).
Where final circuits comprise a number of different wiring systems from the original of the installation, an approximation of the loop impedance under fault conditions shall be carried out in accordance with I.E.E. Guidance No. 3, 'INSPECTION AND TESTING'.
If the measured value of loop impedance does not exceed 80% of the relevant values in Tables 41.2, 41.3, 41.4 and 41.5, this would be considered satisfactory and disconnection times will be achieved.
A satisfactory result is indicated on the appropriate test sheet by 'PASS' and an unsatisfactory result by 'FAIL'.
Should the approximation exceed the tabulated value, a full and more accurate calculation shall be carried out for that circuit.
In order that these maximum values can be directly compared with the actual test values, it is necessary to adjust the tabulated figures since these are based on a conductor temperature under fault conditions (70ºC for PVC) and the test results are based on a conductor temperature taken as the ambient temperature (20ºC).
The calculation is a follows:-
Zs = {F (Zs -Ze)} + Ze (max) (TAB)
WHERE Zs
(MAX) = Value indicated on test sheet 4 for direct comparison with the measured value.
Zs
(TAB) = Value given in I.E.E. Regs. Tables 41B1, 41B2 and 41D.
Ze = External earth fault loop impedance at origin.
F = Correction factor to adjust tabulated value to a Conductor temp of 'ambient' for direct comparison with test value.
The test sheet would include a column headed "Max E.F.L.I." in which is indicated maximum earth fault loop impedance for each circuit tested to achieve disconnection times of 5 sec. Or 0.4 sec. As applicable, this information is indicated.
These values should be based on Tables 41B1 and 41B2 and 41D of the I.E.E. Wiring Regulations and related to the time/current characteristics of the protective device in the circuit.
PROSPECTIVE SHORT CIRCUIT CURRENT (Reg. 612.11)
The prospective fault current, under both short-circuits and earth fault conditions, at every relevant point of the complete installation shall be determined. This shall be done by calculation, ascertained by enquiry or by measurement.
ADDITIONAL PROTECTION (Reg. 612.10)
Where protection against indirect contact is provided by a residual current device, its effectiveness shall be verified by a test simulating an appropriate fault condition and independent of any test facility incorporated in the device.
The test would be made on the load side of the device, between the phase conductor of the circuit protected and the associated C.P.C., so that a suitable residual current flows. All loads normally supplied through the device would be disconnected during the test.
General purpose rcds to Bs 4293
(a) with a fault current flowing equivalent to 50% of the rated tripping current of the rcd for a period of 2 s, the device should not be open
(b) with a fault current flowing equivalent to 100% of the rated tripping current of the rcd, the device should open in less than 200 ms.
General purpose rcds to BS EN 61008 or rcbo's to BS EN 61009
(a) with a fault current flowing equivalent to 50% of the rated tripping current of the rcd for a period of 2 s, the device should not open
(b) with a fault current flowing equivalent to 100% of the rated tripping current of the rcd, the device should open in less than 300 ms unless it is of "Type S" (or selective) which incorporates an intentional time delay. In this case it should trip within the time range of 130 ms and 500 ms.
RCD protected socket-outlets to BS7288
(a) with a fault current flowing equivalent to 50% of the rated tripping current of the rcd for a period of 2 s, the device should not open
(b) with a fault current flowing equivalent to 100% of the rated tripping current of the rcd, the device should open in less than 200 ms.
Additional requirements for supplementary protection (Ref. 412-06-02). Where the rcd is used to provide supplementary protection against direct contact in accordance with Regulation 412-06-02, with a test current of 150 mA the device should open in less than 40 ms. The maximum test time must not be longer than 50 ms.
Since some residual current devices are either partially desensitised or totally disabled by waveforms containing a pulsating D.C. component, the instrument used would have a D.C. test facility which should cause the device to trip within 200 ms.
All the above tests would be carried out at phase angles of 0º and 180º.
In no event should test currents be applied for periods exceeding two seconds.
The effectiveness of the test button or other test facility integral with the device would be tested after application of the externally applied tests described above.
CHECK OF PHASE SEQUENCE (Reg. 612.12) FUNCTIONAL TESTING (Reg. 612.13)
Where fault protection and/or additional protection is to be provided by an RCD, the effectiveness of any test facility incorporated in the device shall be verified.
Assemblies, such as switchgear and control gear assemblies, drives, controls and interlocks, shall be subjected to a functional test to show that they are properly mounted, adjusted and installed in accordance with the relevant requirements of the Regulations.
For multiphase circuits, it shall be verified that the phase sequence is maintained.
VERIFICATION OF VOLT DROP (Reg. 612.14)
Where required to verify compliance with Section 525, the following options may be used:
(i) The voltage drop may be evaluated by measuring the circuit impedance
(ii) The voltage drop may be evaluated by using calculations, for example, by diagrams or graphs showing maximum cable length v load current for different conductor cross-sectional areas with different percentage voltage drops for specific nominal voltages, conductor temperatures and wiring systems.
DOCUMENTATION (Chapter 63)
On completion, certified documentation would be provided including all instrument reading.
(a) Page 3 - Particulars of installation including supply characteristics and main earthing and bonding details.
The report shall be set out as follows:
All items individually numbered.
The location of the remedial item stated.
All items of remedial works shall include the I.E.E. Regulation Reference number of which they are in breach.
All items of remedial work shall be marked on site for ease of location with a sticker.
Each item of remedial works would be classified with a reference letter as follows:
Code 1 - REQUIRES IMMEDIATE ATTENTION
Code 2 - REQUIRES ATTENTION AS SOON AS IS PRACTICABLE
Code 3 - REQUIRES FURTHER INVESTIGATION
D – DOES NOT COMPLY TO BS 7671:2008 AS AMENDED
LABELS
All
distribution boards tested would be provided with an
adhesive label, fixed to the front cover indicating
the date tested.
Software
We have decided to create our own software for Fixed
Wiring inspections. This software will be available
to purchase.
PIRForm
is a new software package to provide electricians a
low cost, easy to use method of producing Periodic Installation
Reports for fixed wiring installations. For more
information, please visit the PIRform
website.
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