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
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.
CHARACTERISTICS
OF SUPPLY (Reg. 313-01-01)
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)
Maximum
demand in amps.
Type
of rating of supplier's overcurrent protective device.
VISUAL
INSPECTION (Reg. 731-01-02)
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
120-01, 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. 514-03, and tables
51A and 51B.
No
signs of overloading of conductors and accessories.
On
a sampling basis, check correct connection of socket
outlets and Lampholders 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. 514-10-01).
(b)
Warning notices on earthing and bonding conductors stating
"Safety Electrical Connection - Do Not Remove".
(Reg. 514-13-01).
Identifying
dangers, which might arrive during instrument testing.
Flexible
cables and cords (Reg 712-01-03). Where a flexible cable
or cord forms part of the fixed wiring installation,
the inspection should include:
(a)
Examination of the cable or cord for damage or defects.
(b)
Examination of the terminations and anchorage's for
damage or defects.
(c)
The correctness of its installation with regard to additional
mechanical protection, heat resistant sleeving, etc.
Enclosures
and Mechanical Protection (Reg. 713-07-08, 712-01-03).
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. 712-01-02, 712-01-03) 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.
514-09-01). Where sample inspections are carried out,
these should include removal of luminaire covers, switch
plates, socket outlets and covers of equipment.
Its
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.
C.P.C.
CONTINUITY (Reg. 713-02-01)
Protective
conductors would be tested to verify that the conductors
are Electrically sound and correctly connected.
This
test should include:
(a)
All bonding conductors.
(b)
All earth visible clamps.
(c)
All metal accessories and equipment within a height
of 3.5m above floor level.
(d)
The last lighting point on all lighting circuits.
The
results of C.P.C. continuity tests shall be recorded
in ohms.
RING
CIRCUIT CONTINUITY (Reg 713-03-01)
An
abbreviated ring circuit loop test would be carried
out which will only ascertain that there is a ring on
the outgoing cables from the distribution board and
shall not identify a bridged ring.
INSULATION
RESISTANCE (Reg. 713-04)
Insulation
resistance tests between phase conductors, neutral and
earth, and excepting any electronic equipment which
may be damaged by the test, would be carried out to
verify that the insulation of conductors, electrical
accessories and equipment is satisfactory and that electrical
conductors or protective conductors are not short circuited,
or show a low resistance which would indicate deterioration
in the insulation.
The
test would be carried out with all fuses in place, switches
and circuit breakers closed, and other equipment disconnected
as appropriate.
Where
the removal of lamps and/or the disconnection of current
using equipment is impracticable, the local switches
controlling such lamps and/or equipment would be open.
Insulation
resistance tests would be carried out from all main
switchboards and sub-main cables.
At
distribution boards, insulation resistance tests would
be carried out at the bus-bars and would include all
final circuits connected to the distribution board,
tested collectively.
POLARITY
(Reg. 713-09-01)
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 FAULT LOOP IMPEDANCE (Reg. 713-10-01)
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 dis-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
83% of the relevant values in Tables 41B1 and 41B2,
this would be considered satisfactory and disconnection
times will be achieved.
A
satisfactory result is indicated on the appropriate
test sheet by 'P' and an unsatisfactory result by 'F'.
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. 434-02-01)
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.
OPERATION
OF RESIDUAL CURRENT DEVICES (Ref. 713-12-01)
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.
DOCUMENTATION (Chapter 74)
On
completion, certified documentation would be provided
including all instrument reading.
(a)
SHEET A - 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:
A - REQUIRES IMMEDIATE ATTENTION
B - REQUIRES URGENT ATTENTION
C - REQUIRES ATTENTION AS SOON AS PRACTICABLE - COULD
DETERIORATE AND BECOME A DANGER
D - REQUIRED TO BRING INSTALLATION INTO LINE WITH CURRENT
STANDARDS OF GOOD WORKMANSHIP AND PRACTICES
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 out 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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