USSU Stage Crew
Level 2B Training Manual
STAGE CREW
Electrical Training
Manual
Level 2B:
Portable Appliance
Testing
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Revision Record:
This document is only to be reissued in its entirety.
Issue
0
1
Revision Comment
Initial Draft
First issue for training
Issue: 1
Revised By
R. White
R. White
Issue Date
Dec 2008
May 2009
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CONTENTS
1. LEGISLATION ............................................................................................................ 5
1.1 The Health & Safety at Work Act 1974 .................................................................. 5
1.2 The Management of the Health & Safety at Work Act Regulations 1999 ........... 5
1.3 The Provision & Use of Work Equipment Regulations 1998 .................................. 5
1.4 The Electricity at Work Regulations 1989 .............................................................. 5
1.4.1 Electrical System ............................................................................................. 6
1.4.2 Duty Holder ..................................................................................................... 6
2. BASIC ELECTRICAL THEORY .................................................................................. 7
2.1 Electrical quantities and units ................................................................................ 7
2.2
Relationship between voltage, current and resistance ..................................... 7
2.3 Resistance in series .............................................................................................. 7
2.4 Resistance in parallel ............................................................................................ 8
3. SHOCK RISK............................................................................................................ 10
3.1 Electric shock ...................................................................................................... 10
3.2 Protection against direct contact .......................................................................... 10
3.3 Protection against indirect contact ....................................................................... 11
3.4 What is earth and why and how we connect to it? ............................................... 11
4. EQUIPMENT UNDER TEST ..................................................................................... 13
4.1 Class 0 equipment or appliances ......................................................................... 13
4.2 Class 01 equipment or appliances ....................................................................... 13
4.3 Class I equipment or appliances .......................................................................... 13
4.4 Class II equipment or appliances ......................................................................... 13
4.5 Class III equipment or appliances ........................................................................ 14
4.6 Equipment types .................................................................................................. 15
4.6.1 Portable equipment/appliances ..................................................................... 15
4.6.2 Hand held equipment/appliances .................................................................. 15
4.6.3 Moveable equipment/appliances ................................................................... 15
4.6.4 Stationary equipment/appliances ................................................................... 15
4.6.5 Fixed equipment/appliances .......................................................................... 15
4.6.6 Built-in equipment/appliances ........................................................................ 16
4.6.7 Information technology (IT) equipment .......................................................... 16
4.6.8 Extension leads ............................................................................................. 16
5. INSPECTION ............................................................................................................ 17
5.1 User checks......................................................................................................... 17
6. COMBINED INSPECTION & TESTING .................................................................... 18
6.2 When To Test ...................................................................................................... 18
6.2 Testing ................................................................................................................ 18
6.2.1 Preliminary inspection ................................................................................... 19
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6.2.2 Testing .......................................................................................................... 20
6.3 Test Equipment ................................................................................................... 20
6.3.1 Portable appliance testers ................................................................................ 20
6.3.2 Continuity/insulation resistance testers ............................................................. 20
6.4 Earth continuity.................................................................................................... 20
6.5 Conducting the earth continuity test ..................................................................... 22
6.5.1 Portable appliance tester ............................................................................... 22
6.5.2 Continuity tester ............................................................................................ 22
6.6 Insulation Resistance Test................................................................................... 23
6.6.1 The applied voltage method .......................................................................... 24
6.6.2 The earth leakage method ............................................................................. 24
6.7 Functional checks ................................................................................................ 25
6.8 Testing cables ..................................................................................................... 25
7. RECORDING & LABELLING.................................................................................... 27
7.1 Test Labels....................................................................................................... 27
7.2 Recording Results ............................................................................................ 27
Appendix ...................................................................................................................... 28
Appendix A: USSU Risk Assessment – Electrical Safety ........................................... 29
Appendix B: USSU Risk Assessment – Cam-lok Connector ...................................... 32
Appendix C: USSU Risk Assessment – Loadstar Connector ..................................... 37
Appendix D: USSU PAT Test Manual – Quick Reference Test Procedure ................ 39
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1. LEGISLATION
There are four main sets of legislation that are applicable to the inspection and testing of
in-service electrical equipment:




The Health & Safety at Work Act 1974 (H&SWA)
The Management of the Health & Safety at Work Act Regulations 1999
The Provision & Use of Work Equipment Regulations 1998
The Electricity at Work Regulations 1989 (EAWR).
1.1 The Health & Safety at Work Act 1974
This applies to all persons (employers and employees) at work, and places a duty of
care on all to ensure the safety of themselves and others.
1.2 The Management of the Health & Safety at Work Act
Regulations 1999
In order that the H&SWA can be effectively implemented in the workplace, every
employer has to carry out a risk assessment to ensure that employees and those not in
his/her employ, are not subjected to danger.
1.3 The Provision & Use of Work Equipment Regulations 1998
Work equipment must be constructed in such a way that it is suitable for the purpose for
which it is to be used. Once again, the employer is responsible for these arrangements.
1.4 The Electricity at Work Regulations 1989
These regulations, in particular, are very relevant to the inspection and testing of inservice electrical equipment. There are two important definitions in the EAWR: the
electrical system and the duty holder.
Compliance with regulation 16 of EAWR 1989 is compulsory, this means no matter what
the time or cost involved, it must be done.
“No person shall be engaged in any work activity where technical knowledge or experience is
necessary to prevent danger or, where appropriate, injury, unless he possesses such
knowledge or experience, or is under such degree of supervision as may be appropriate
having regard to the nature of the work.”
This Regulation deals with the person being competent. One way, amongst others, to
prove to a court of law that you are a competent person is through regular training.
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1.4.1 Electrical System
This is anything that generates stores, transmits or uses electrical energy, from a power
station to a wrist-watch battery. The latter would not give a person an electrical shock,
but could explode if heated, giving rise to possible injury from burns.
1.4.2 Duty Holder
This is anyone who has ‘control’ of an electrical system. Control in this sense means
designing, installing, working with or maintaining such a system. Duty holders have the
legal responsibility to ensure their own safety and the safety of others whilst in control of
an electrical system. See the appendix of this document for some of USSU applicable
risk assessments which are the duty holders’ responsibility to carry out. A risk
assessment should always be carried out for any new situation for which there is not a
risk assessment already in place. Individuals should always be carrying out their own
risk assessments during the course of their work.
The EAWR do not specifically mention inspection and testing; they simply require
electrical systems to be `maintained' in a condition so as not to cause danger. However,
we only know if a system needs to be maintained if it is inspected and tested, and thus
the need for such inspection and testing of a system is implicit in the requirement for it to
be maintained.
Anyone who inspects and tests an electrical system is, in law, a duty holder and must be
competent to undertake such work.
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2. BASIC ELECTRICAL THEORY
This section gives a basic explanation of relevant electrical theory for those relatively
new to the subject and provides a refresher for others with more experience.
2.1 Electrical quantities and units
Quantity
Symbol
Units
Current
Voltage
Resistance
I
V
R
Ampere (A)
Volt (V)
Ohm (Ω)
Power
P
Watt (W)
Current:
This is the flow of electrons in a conductor.
Voltage:
This is the electrical pressure causing the current to flow.
Resistance: This is the opposition to the flow of current in a conductor determined by
its length, cross sectional area and temperature.
Power:
2.2
This is the product of current and voltage, hence P = I x V.
Relationship between voltage, current and resistance
Voltage = Current x Resistance
V=IxR
Current = Voltage/Resistance
I = V/R
Resistance = Voltage/Current
R = V/I
2.3 Resistance in series
These are resistances joined end to end in the form of a chain. The total resistance
increases as more resistances are added.
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Rtotal = R1 + R2 + R3 + R4
Hence, if a cable length is increased, its resistance will increase in proportion. For
example, a 100 m length of conductor has twice the resistance of a 50 m length of the
same diameter. This increase in length and therefore increase in resistance of a cable
causes problems. Earth loop impedance is the series resistance of a distribution system
from the earth point at the substation to the load and back. If the cable is made too long,
its resistance becomes too high to allow sufficient current to flow under fault conditions.
If this is the case and the high resistance limits the fault current, this current may not be
sufficient to cause an MCB to disconnect if a fault occurs. Larger cross sectional area
cable have low resistance resulting in lower voltage drops along the cables length and
lower earth loop impedances.
2.4 Resistance in parallel
These are resistances joined like the rungs of a ladder. Here the total resistance
decreases the more resistances there are. The overall resistance of two or more
conductors will also decrease if they are connected in parallel
The insulation between conductors is in fact countless millions of very high value
resistances in parallel. Hence an increase in cable length results in a decrease in
insulation resistance. This value is measured in millions of ohms, i.e. megohms (MΩ).
The total resistance will be half of either one and would be the same as the resistance of
a 2.0mm2 conductor. Hence resistance decreases if the conductor’s cross sectional area
increases.
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1 /Rtotal = 1 /R1 + 1 /R2 + 1 /R3 + 1 /R4
1 /Rtotal = 1/3 + 1/6 + 1/8 + ½
Rtotal = 1/1.125
Rtotal = 0.89
Parallel resistance also limits the length of a cable. The decreased insulation resistance
of a long cable causes high leakage current (current flowing from the live and neutral
conductors to the CPC through the cable insulation). This high leakage current can
cause nuisance tripping of RCD making very long cables unusable.
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3. SHOCK RISK
All those who are involved with electrical systems are `Duty holders' in the eyes of the
Law. For those who have only a limited knowledge of electricity, but are nevertheless
involved with appliance testing, an understanding of electric shock will help to give more
meaning and confidence to the inspection and test process.
3.1 Electric shock
This is the passage of current through the body of such magnitude as to have significant
harmful effects. The generally accepted effects of current passing through the human
body:
1 mA-2 mA Barely perceptible, no harmful effects
5 mA-10 mA Throw off, painful sensation
10 mA-15 mA Muscular contraction, can't let go
20 mA-30 mA Impaired breathing
50 mA and above Ventricular fibrilation and death
These are two ways in which we can be at risk:


Touching live parts of equipment or systems that are intended to be live. This is
called direct contact.
Touching conductive parts which are not meant to be live, but which have
become live due to a fault. This is called indirect contact.
The conductive parts associated with indirect contact can either be:
o
Exposed conductive parts: metalwork of the electrical equipment and
accessories and that of electrical wiring systems (e.g. metal conduit or
equipment cases), or
o
Extraneous conductive parts or other metalwork (e.g. pipes, trussing,
staging and girders).
3.2 Protection against direct contact
How can we prevent danger to persons and livestock from contact with intentionally live
parts? Clearly we must minimize the risk of such contact and this can be achieved by:


Insulating any live parts
Ensuring any uninsulated live parts are housed in suitable enclosures and/or are
behind barriers.
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The use of a residual current device (RCD) cannot prevent direct contact, but it can be
used to supplement any of the other measures taken, provided that it is rated at 30mA or
less and has a tripping time of not more than 40ms at an operating current of 150mA. It
should be noted that RCDs are not the remedy for all electrical ills, they can malfunction,
but they are a valid and effective back-up to the other methods. They must not be used
as the sole means of protection.
3.3 Protection against indirect contact
How can we protect against shock from contact with live, exposed or extraneous
conductive parts whilst touching earth, or from contact between live exposed and/or
extraneous conductive parts? The most common method is by earthed equipotential
bonding and automatic disconnection of supply.
All extraneous conductive parts are joined together with a main equipotential bonding
conductor and connected to the main earthing terminal, and all exposed conductive
parts are connected to the main earthing terminal by the circuit protective conductors.
Add to this, overcurrent protection that will operate fast enough when a fault occurs and
the risk of severe electric shock is significantly reduced.
3.4 What is earth and why and how we connect to it?
The thin layer of material which covers our planet - rock, clay, chalk or whatever - is
what we in the world of electricity refer to as earth. So, why do we need to connect
anything to it? After all, it is not as if earth is a good conductor.
It might be wise at this stage to investigate potential difference (PD). A PD is exactly
what it says it is: a difference in potential (volts). In this way, two conductors having PDs
of, say, 20V and 26V have a PD between them of 26 - 20 = 6V The original PDs (i.e.
20V and 26V) are the PDs between 20V and 0V and 26V and 0V So where does this 0V
or zero potential come from? The simple answer is, in our case, the earth. The definition
of earth is, therefore, the conductive mass of earth, whose electric potential at any point
is conventionally taken as zero.
Thus, if we connect a voltmeter between a live part (e.g. the phase conductor of a socket
outlet) and earth, we may read 230V; the conductor is at 230V and the earth at zero.
The earth provides a path to complete the circuit. We would measure nothing at all if we
connected our voltmeter between, say, the positive 12V terminal of a car battery and
earth, as in this case the earth plays no part in any circuit.
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So, a person in an installation touching a live part whilst standing on the earth would
take the place of the voltmeter and could suffer a severe electric shock. Remember that
the accepted lethal level of shock current passing through a person is only 50mA or
1/20A. The same situation would arise if the person were touching a faulty appliance and
a gas or water pipe.
One method of providing some measure of protection against these effects is, as we
have seen, to join together (bond) all metallic parts and connect them to earth. This
ensures that all metalwork in a healthy installation is at or near 0V and, under fault
conditions, all metalwork will rise to a similar potential. So, simultaneous contact with two
such metal parts would not result in a dangerous shock, as there would be no significant
PD between them.
Unfortunately, as mentioned, earth itself is not a good conductor, unless it is very wet.
Therefore, it presents a high resistance to the flow of fault current. This resistance is
usually enough to restrict fault current to a level well below that of the rating of the
protective device, leaving a faulty circuit uninterrupted. Clearly this is an unhealthy
situation.
In all but the most rural areas, consumers can connect to a metallic earth return
conductor, which is ultimately connected to the earthed neutral of the supply. This, of
course, presents a low-resistance path for fault currents to operate the protection.
In summary, connecting metalwork to earth, places that metal at or near zero potential
and bonding between metallic parts puts such parts at a similar potential even under
fault conditions. Add to this, a low-resistance earth fault return path, which will enable
the circuit protection to operate very fast, and we have significantly reduced the risk of
electric shock. We can see from this how important it is to check that equipment earthing
is satisfactory and that there is no damage to conductor insulation.
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4. EQUIPMENT UNDER TEST
It is not just portable appliances that have to be inspected and tested, but all in-service
electrical equipment. This includes items connected to the supply by 13A BS 1363
plugs, BS EN 60309-2 industrial plugs or hard wired to the fixed installation via fused
connection units or single or three-phase isolators.
4.1 Class 0 equipment or appliances
Equipment with a non-earthed metal case. The protection against electric shock
being provided by insulating live parts with basic insulation only. Breakdown of this
insulation could result in the metal enclosure becoming live and with no means of
disconnecting the fault. The Statutory Electrical Equipment Safety Regulations
introduced in 1975 effectively ban the sale of Class 0 equipment. It would be
reasonable to expect never to encounter a class 0 appliance but you should be
aware of the classification.
Class 0 equipment must not be confused with class II (See following sections).
4.2 Class 01 equipment or appliances
This is the same as Class 0. However, the metal casing has an earthing terminal but the
supply cable is twin and the plug has no earth pin. Class 0 and 0I equipment may be
used but only in special circumstances and in a strictly controlled environment. Generally
these classes should not be used unless connections to earth are provided on the item
and an earth return path via a supply cable that has a circuit protective conductor (cpc)
incorporated: this would convert the equipment to Class l.
4.3 Class I equipment or appliances
These items have live parts protected by basic insulation and a metal enclosure or
accessible metal parts that could become live in the event of failure of the basic
insulation (indirect contact). Protection against shock is by basic insulation and earthing
via casing the cpc in the supply cable and the fixed wiring. Typical Class I items include
toasters, kettles, washing machines, lathes and pillar drills.
4.4 Class II equipment or appliances
Commonly known as double-insulated equipment, the items have live parts
encapsulated in basic and supplementary insulation (double), or one layer of reinforced
insulation equivalent to double insulation.
Even if the item has a metal casing (for mechanical protection) it does not require
earthing as the strength of the insulation will prevent such metalwork becoming live
under fault conditions. The cable supplying such equipment will normally be two core
with no cpc.
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Examples of Class II equipment would include most modern garden tools such as hedge
trimmers and lawn mowers and also food mixers, drills, table lamps etc. All such items
should display the Class II equipment symbol:
Equipment with grills or openings, e.g. hair dryers, need to pass the standard finger
entry test. (There should be no gaps in the case sufficiently large to allow a ‘Standard
British Finger’ the enter the equipment)
4.5 Class III equipment or appliances
This is equipment that is supplied from a Separated Extra Low Voltage Source (SELV),
which will not exceed 50V and is usually required to be less than 24V or 12V. Typical
items would include telephone answer machines, and other items of IT equipment. Such
equipment should be marked with the symbol:
and be supplied from a safety isolating transformer to BS3535 which in itself should be
marked with the symbol:
These transformers are common and are typical of the type used for charging mobile
phones etc. Note there are no earths in a SELV system and hence the earth pin on the
transformer is plastic.
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4.6 Equipment types
The Code of Practice defines various type of equipment/ accessory that needs to be
inspected and tested and that are generally in normal use. Advice from the manufacturer
should be sought before testing specialist equipment. The equipment types are as
follows:
4.6.1 Portable equipment/appliances
These are items which are capable of easy movement whilst energised and/or in
operation. Examples of such appliances are:
 CD player
 Toasters
 Kettle
 Parcan
4.6.2 Hand held equipment/appliances
These items are of a portable nature that requires control/use by direct hand contact.
Examples Include:
 Drills
 Heat gun
 Soldering irons.
4.6.3 Moveable equipment/appliances
There is a thin dividing line between this and the previous two types, but in any case still
needs inspecting and testing. Generally such items are 18kg or less and have wheels or
are easily moved. Examples would include:
 tumble dryers
 Small amp racks
 UPS
 industrial/commercial kitchen equipment.
4.6.4 Stationary equipment/appliances
This is equipment in excess of 18 kg and which is not intended to be moved about, such
as:
 Ordinary cookers
 Air Compressor
 Dust Extractor.
4.6.5 Fixed equipment/appliances
These items are fixed or secured in place, typically:
 Tubular heaters
 Lathes and other industrial equipment
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Fixed work lights
4.6.6 Built-in equipment/appliances
This is equipment that is `built-in' to a unit or recess such as:
 An oven
 Install dimmer rack
4.6.7 Information technology (IT) equipment
In general terms, this is business equipment such as:
 PCs/Laptops
 Printers
 Scanners
 Lighting Desk
4.6.8 Extension leads
These include the multi-way sockets so very often used where IT equipment is present,
as there is seldom enough fixed socket outlets to supply all the various units. These
leads should always be wired with 3 core (phase, neutral and earth) cable, and should
not exceed:



12 m in length for a 1.25 mm2 core size
15 m in length for a 1.5 mm2 core size
25 m in length for a 2.5 mm2 core size.
The latter should be supplied via a BS EN 60309-2 plug, if any of the lengths are
exceeded, the leads should be protected by a BS7071 30mA RCD.
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5. INSPECTION
Inspection is vital, and must precede testing. It may reveal serious defects which may
not be detected by testing only. Two types of inspection are required:
5.1 User checks
All employees are required by the Electricity at Work Regulations to work safely with
electrical appliances/equipment and hence all should receive some basic
training/instruction in the checking of equipment before use. (This training need only be
of a short duration.) Generally, this is all common sense: nevertheless, a set routine or
pre-use checks should be established. Such a routine could be as follows:






Check the condition of the appliance/equipment (look for cracks or damage).
Examine the cable supplying the item, looking for cuts, abrasions, cracks etc.
Check the cable sheath is secure in the plug and the appliance.
Look for signs of overheating.
Check that it has a valid label indicating that it has been formally inspected and
tested.
Decide if the item is suitable for the environment in which it is to be used, e.g.
240 V appliances should not be used on a construction site.
If all these checks prove satisfactory, check that the appliance is working correctly.
If the user feels that the equipment is not satisfactory, it must be switched off, removed
from the supply, labeled `Not to be used' or words to that effect. That person will then
take the necessary action to record the faulty item and arrange remedial work or have it
disposed of.
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6. COMBINED INSPECTION & TESTING
Combined inspection and testing comprises preliminary inspection with electrical tests to
verify earth continuity, insulation resistance, functional checks and, in the case of cord
sets and extension leads, polarity as well.
6.2 When To Test
At USSU formal electrical testing is carried out at a maximum interval of 12 month, this
means that equipment should be tested at least once every year.
Testing should also be carried out after the equipment in question has undergone any
maintenance or repair that may affect the electrical safety of the equipment. Full testing
may also be carried out if it is suspected that an item of equipment may have
experienced conditions or treatment that may make the equipment unsafe.
All electrical equipment must be tested before it can be used at USSU. This includes
equipment bought by visitors/ acts that use the venue. If the equipment appears to be
in good condition, labelled with in date test labels or has appropriate
documentation/certification to say it is tested and is safe then there is no need to retest
the equipment. If however you are concerned about the safety of the equipment or the
owner/user cannot provide you with suitable proof of safety then it is necessary for their
equipment to be tested, with their permission, before it is used in the building. It should
be explained to any such person bringing equipment into the building that….
It is the responsibility of USSU to ensure safe practices and a safe working
environment for all those within its care. This includes staff, acts,
customers, visitors, the public (in fact anyone that may come into contact
with USSU). As part of this responsibility USSU cannot allow the use of any
potentially unsafe electrical equipment. Therefore USSU requests, with
given permission, to formally electrical test equipment bought into the
building before it is used. If we are denied access to the equipment for
testing we cannot allow the equipment to be used within USSU unless the
owner can provide proof that the equipment is safe. Equally we cannot
allow the use of any equipment that does not pass safety testing to be
used. USSU cannot take responsibility for any damage, although unlikely,
that may occur during test by a trained member of our Technical Services
team.
It can often be difficult to tell someone they cannot use something that is theirs but you
should tactfully explain to them the reason for this and that we are responsible to
provide a duty of care in the eyes of the law. You should be considerate and tactful
when doing this.
6.2 Testing
This has to be carried out with the appliance/equipment isolated from the supply. Such
isolation is, of course, easy when the item is supplied via a plug and socket, but presents
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some difficulties if it is permanently wired to, say, a flex outlet, a connection unit, or an
isolator etc. In these cases the tester must be competent to undertake a disconnection of
the appliance, if not, then a qualified/competent electrical operative should carry out the
work.
Additionally, the permission of a responsible person may be needed before
isolating/disconnecting business equipment.
6.2.1 Preliminary inspection
Before any equipment is subjected to electrical tests it should first be visually inspected.
The following items should be checked during a visual inspection. If the visual
inspection finds the equipment to be satisfactory then the electrical test may be carried
out.
Cables:
 Check the length of the cable for damage, nicks, exposed inner cores or exposed
copper.
Plugs and sockets:
 The plug is not cracked or broken in any way
 Open the plug or socket and check:
 The strain relief is clamped tightly on the outer sheath of the cable; there should
be no inner cores visible beyond the strain relief.
 The screw terminals are done up tightly.
 There is no copper visible outside the screw terminal
 The wire in the screw terminal has been twisted and fills the terminal (by doubling
back where necessary)
 There are no stray strands of copper
 The wires go to the correct terminals:
(Live - brown or black; neutral - blue; earth - green/yellow)
 There is a little slack in the cables between the strain relief and the terminals
 The correct rating fuse is fitted where relevant
 The cover can not be removed without the use of the correct tool
Cable entries to equipment:
 Grommet or gland present and not damaged / perished
 Cable firmly held by cable clamp with no inner cores visible (gently tug cable)
 Outer sheath not damaged under cable gland
Lanterns:
 Check for any burnt or damaged cables inside lantern
 Check as for plug or socket
Equipment:
 Vents and fans are clean, working and not clogged with dust
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6.2.2 Testing
This may be carried out using a portable appliance tester, of which there are many
varieties, or separate instruments capable of measuring continuity and insulation
resistance. See following sections.
6.3 Test Equipment
6.3.1 Portable appliance testers
These instruments allow appliances, fitted with a plug, to be easily tested. Some testers
have the facility for testing appliances of various voltage ranges, single and three phase,
although the majority only accept single phase 240V or 110V plugs (BS 1363 and BS EN
60309-2).
Generally, portable appliance testers are designed to allow operatives to `plug in' an
item of equipment, push a test button, view results and note a `pass' or `fail' indication.
The operative can then interpret these results and, where possible, make adjustments
which may enable a `fail' indication to be changed to a `pass' status.
Some portable appliance testers are of the GO, NO-GO type where the indication is
either a red (fail) or green (pass) light. As there are no test figures associated with this
type of tester, no adjustment can be made. This could result in appliances being rejected
when no fault is present. This situation will be dealt with a little later.
6.3.2 Continuity/insulation resistance testers
These are usually dual instrument testers, although separate instruments are in use.
Multimeters are rarely suitable for these tests. For earth continuity, the instrument test
current (a.c. or d.c.) should be between 20 and 200mA with the source having an open
circuit voltage of between 100mV and 24V For insulation resistance the instrument
should deliver a maintainable test voltage of 500V d.c. across the load. (Note: All test
leads should conform to the recommendations of the HSE Guidance Note GS 38.)
6.4 Earth continuity
This test can only be applied to Class I equipment and cables, and the purpose of the
test is to ensure that the earth terminal of the item is connected to the casing effectively
enough to result in the test between this terminal and the casing giving a value of not
more than 0.2Ω.
Clearly, it is not very practicable to have to access terminals inside an enclosure and
hence, it is reasonable to measure the earth continuity from outside, via the plug and
supply lead. This also checks the integrity of the lead earth conductor, or cpc.
Testing in this way will, of course, add the resistance of the lead to the appliance earth
resistance, which could result in an overall value in excess of the 0.2Ω limit, and the
tester may indicate a `fail' status. This is where the interpretation of results is so
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important in that, provided the final value having subtracted the lead resistance from the
instrument reading is no more than 0.2Ω, the appliance can be passed as satisfactory.
The use of a GO, NO-GO instrument prohibits such an adjustment as there are no test
values available.
The following table gives the resistance in ohms per metre of copper conductors, at
20°C for flexible cords from 0.5 mm 2 to 4.0 mm2.
Conductor size (mm2)
Resistance (Ω/m)
0.5
0.75
1.0
1.25
1.5
2.5
4.0
0.039
0.026
0.0195
0.0156
0.013
0.008
0.005
Hence the cpc of 5m of 1.0mm2 flexible cord would have a resistance of:
5 x 0.0195 = 0.0975Ω
It is unlikely that appliances in general use will have supply cords in excess of 1.25mm2
as the current rating for such a cord is 13A, which is the maximum for a BS1363 plug.
Example:
The measured value of earth continuity for an industrial floor polisher, using a portable
appliance tester, is 0.34Ω. The supply cord is 10m long and has a conductor size of 0.75
mm2. The test instrument also indicates a `fail' condition. Can the result be overruled?
Resistance of cpc of lead = 10 x 0.026 = 0.26Ω,
Test reading, less lead resistance = 0.34 - 0.26 = 0.08Ω
This is less than the maximum of 0.2Ω, so, yes the appliance is satisfactorily earthed,
and the test reading can be overruled to 'pass'.
The only problem with this approach is that most portable appliance testers have
electronic memory which can be downloaded to software on a PC, which would record
0.34Ω, and a `fail' status. Unless the instrument or the software includes the facility to
include lead resistance, the appliance still fails.
Having made the above comments, it must be said that only low power appliances with
very long cables having small size conductors, cause any problems.
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6.5 Conducting the earth continuity test
6.5.1 Portable appliance tester
Having conducted the preliminary inspection:
1. Plug the appliance into the tester and select, if possible, a suitable current. This
will be 1.5 times the fuse rating (if the correct fuse is in place) up to a maximum
of 25A.
2. Connect the earth bond lead supplied with the tester, to a suitable earthed point
on the appliance. (Remember that just because there is metal, it does not mean
that it is connected to earth.) A fixing screw securing the outer casing to a frame
is often the best place, rather than the actual casing, which may be enamelled or
painted and may contribute to a high resistance reading. If a high reading is
obtained, other points on the casing should be tried.
3. Start the test, and record the test results. Do not touch the appliance during the
test.
6.5.2 Continuity tester
The method is in general as for the portable appliance tester:
1. Zero the instrument.
2. Connect one lead to the earth pin of the plug.
3. Connect the other lead to the appliance casing.
4. Start the test and record the test results. Do not touch the appliance during the
test.
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Again, in the case of testing items of equipment that have to be disconnected from the
supply, special test accessories are useful to aid the testing process. Such an accessory
would be, for example, a plug, short lead and connector unit, to which a disconnected
item could be connected. This is especially useful when using a portable appliance
tester, whereas a continuity tester can be connected easily to the exposed protective
conductor of the equipment.
Multiway extension sockets and extension leads are to be treated as Class I equipment.
However, there is some difficulty in gaining a connection to the earth pin of socket
outlets and female plugs. Poking a small screwdriver into the earth socket is not good
working practice.
6.6 Insulation Resistance Test
Realistically, this test can only be carried out on Class I equipment. It is made to ensure
that there is no breakdown of insulation between the protective earth and live (phase
and neutral) parts of the appliance and its lead.
For Class II items, there are no earthed parts and one test probe would need to be
placed at various points on the body of the appliance in order to check the integrity of the
casing.
Items that have a cord set, e.g. a kettle, should have the cord set plugged into the
appliance and the appliance switch should be in the `on' position.
There are two tests that can be made, using either the applied voltage method or the
earth leakage method.
ITEMS
LIKE
DISTRIBUTION
UNITS
THAT
CONTAIN
RCD’S
AND
SOME
EQUIPMENT WITH MAINS FILTERS SHOULD NOT BE SUBJECTED TO THIS TEST
AS IRREPARABLE DAMAGE CAN BE CAUSED TO THESE DEVICES DUE TO THE
HIGH APPLIED VOLTAGES.
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6.6.1 The applied voltage method
This is conducted using an insulation resistance tester, set on 500Vd.c. The test is made
between the phase and neutral connected together, and the protective earth. (For threephase items, all live conductors are connected together.) This is best achieved using the
same arrangement as shown bellow.
Care must be taken when conducting this test to ensure that the appliance is not
touched during the process. Also, it should be noted that some items of equipment have
filter networks connected across phase and earth terminals and this may lead to unduly
low values. The values recorded should not be less than those shown bellow:
Appliance class
Class I heating equipment less than 3kW
General Class I equipment
Class II equipment
Class III equipment
Insulation resistance
0.3 MΩ
1 MΩ
2 MΩ
250 kΩ
Equipment containing Martindale neon indicators will fail this test unless the indicators
are isolated first. A lot of our equipment is fitted with either a key switch or a push button
which disconnects these neon indicators. Some equipment is provided with other
means of disconnecting these indicators. Information for this will normally be supplied
by the equipments manufacturer.
6.6.2 The earth leakage method
This is achieved using a portable appliance tester that subjects the insulation to a less
onerous voltage (usually 250V) than that delivered by an insulation resistance tester.
Here, the leakage current across the insulation is measured, and appliance testers
usually set the maximum value at 3.5mA.
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Whichever method is used, there is a chance of pessimistically low values occurring
when some heating or cooking appliances are tested. This is usually due to moisture
seeping into the insulation of the elements. In this case it is wise to switch such
equipment on for a short while to dry the elements out before testing.
NOTE: Many portable appliance testers have the facility to conduct a `dielectric strength'
or `flash' test, which is basically an insulation resistance test at 1250V for Class I
equipment and 3570V for Class II. Such voltages could cause damage to insulation and
should not be carried out for in-service tests.
6.7 Functional checks
If testing has been carried out using separate instruments, just switch the equipment on
to ensure that it is working. If a portable appliance tester is used, there is usually a
facility for conducting a ‘load test'. The equipment is automatically switched on and the
power consumption measured while the item is on load. This is useful as it indicates if
the equipment is working to its full capacity, e.g. a 2kW reading on a 3kW heater
suggests a broken element.
6.8 Testing cables
Cables can either be tested with the appliance tester and suitable adaptor leads or with
the dedicated cable tester. The cable tester unit is an automated unit specifically for
testing cables. This tester cannot however be used to test cables such as four ways
with built in neon indicators – these must be tested with the appliance tester.
The procedure for using the cable tester is as follows:
Earth bond test:
 Plug in both ends of the cable
 Select the number of cores in the cable using the up / down buttons
 Only cables with the same number of pins at each end can be tested (to test
spiders , join 2 together to form a "socapex").
 If the cable has a 13A plug or an IEC connector then select the 5A test
 For any other cable select the 25A test
 Select the pass value for the cable length and size from the chart provided
 Press the start button
 The green pass light will light up in turn for each core
 A red light indicates a fail
Insulation test:
 Unplug the female socket end of the cable from the tester
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Select the 500V test
Press the start button
The green pass light will light up in turn for each core
A red light indicates a fail
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7. RECORDING & LABELLING
7.1 Test Labels
Every item of electrical equipment should have two labels as follows:
1. USSU Barcode label (or similar label) – this provides each item of equipment
with a unique identification number.
2. A Test Label - similar to the following, it contains two pieces of information:
a. The date on which the item was last formally tested for electrical safety.
This should be in the format DD/MM/YY. If this date is more that 1 year
ago the item requires retesting
b. A unique identifying mark for the person that conducted the test on the
item. This is usually someone’s initials. You should check with the
Technical Manager that the identification you plan to use on your label is
not being used already and should agree with the Technical Manager
what identifier you will use when testing.
Labels should be filled in you using permanent pen that will not smudge or wear off
during use.
Example Label:
7.2 Recording Results
USSU uses a computer based database to record it’s test results. You will be shown
how to use this software as part of your practical introduction the testing equipment. The
technical manager should be able to provide information about the current system and
operating instructions.
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Appendix
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Appendix A: USSU Risk Assessment – Electrical Safety
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University of Surrey Students Union
Technical Services
Risk Assessment: Electrical Safety
Potential Hazards:


Electrocution; and
Fire.
Control Measures:
All electrical equipment and cable belonging to, or in the procession of, USSU Technical
Services is subject to strict electrical safety procedures.
All equipment is manufactured and maintained to, and all systems designed to, the
relevant standards (including BS 7671 and BS 7909) and is selected as safe and
suitable for it's intended purpose. Manufactures guidelines are followed at all times.
All equipment and cable is tested for electrical safety at least once a year, or more often
if deemed necessary by individual risk assessment. Further tests are done after
manufacture, purchase, repair or modification. Testing is done only by competent and
suitably trained staff.
After testing a sticker is attached to the equipment or cable. These stickers state the
date of the test and the name of the tester. Each item has a unique barcode identifier
and the test results for each item are logged in the electrical testing database.
Before an item is issued to a hire or a job the item is visually inspected and the barcode
is scanned. The system indicates whether or not the item is within the permitted test
period. On returning from the job all items are again visually inspected before being
returned to the stock.
Once the complete set of equipment for a particular job has been prepared and scanned
a spreadsheet is printed. This gives details of all items on the job. A copy of the
spreadsheet is included with the equipment. However, for environmental reasons,
individual certificates for each item are not usually printed but are available on request.
Items found to be suspect, faulty or damaged are immediately removed for use, labelled
as faulty and isolated until such a time as it has been tested, repaired and passes the
relevant electrical safety tests. Repairs are carried out only by competent and suitably
trained staff.
Items found to have out of date electrical safety stickers, or flagged as in need of testing
by the electrical testing database are immediately removed from use and isolated until
such a time as it has been tested and passes the relevant electrical safety tests.
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All Technical Services staff are trained in basic electrical safety. They are instructed
about the need to visually inspect all electrical equipment and cables before use and
immediately isolate any suspect, out of date and faulty equipment.
All equipment is fitted with (or provided with) suitable MCB or RCD devices.
For large or complex events a suitably trained and competent person will be appointed
to be in charge of the temporary electrical installation as recommended by BS 7909.
Their duties will include:




The design of a safe system, including: cable sizes, RCDs, MCBs and earthing
arrangements;
Overseeing the safe installation as outlined in the design;
Testing and inspecting the completed installation using simple plug in testers with
regards to polarity, earth fault loop impedance, correct MCB presence, RCD
operation, signage, voltage drop, equipotential, bonding
Recording the results of the testing and evaluating the results, including
completion of the certificate for the insulation.

C02 fire extinguishers are located wherever there are concentrations of electrical
equipment, such as near amplifiers, dimmers and where members of staff are
responsible for overseeing the safe operation of the equipment.
Where cables are running across areas open to public access the cables are mounted
above head height, covered by rubber matting, taped down or buried.
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Appendix B: USSU Risk Assessment – Cam-lok Connector
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Cam-lok Connector Risk Assessment
Issue Date: Feb 2004
This risk assessment is for the use of single pole connectors
commonly known in the industry as “Cam-Lok” when used with single
core or mutli-core cables or as fixed connectors on equipment for
stage lighting.
These are coloured green (earth), black
(neutral), red, yellow [or white] and blue phases. The single core cables used with these
connectors normally have black sheaths - See
Photograph
In a temporary distribution the colour of the
connector designates its circuit function. For a
given current rating “Cam-lok” connectors can
be interconnected no matter what their designated function may be –
See photograph
Colour Coded Connectors,
incorrectly interconnected
shown
Hazards
Identified by using previous professional experience to assess the
continuing use. Any eventuality that indicates a potential risk is
recorded in this document. All eventualities that have been
considered but deemed to present no significant risk are not
recorded.
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Severity
The severity of the outcome of any assessed hazard is allocated a
rating, denoted in the accompanying table by a numerical value (see
below).
Risk
The likelihood of a hazard occurring, assuming that no additional
measures are in place to prevent such an occurrence. Again, a
numerical value is used in the table.
Control Measures
Any further action taken by the equipment Managers or users, with
specific intention of reducing the risk of any hazard to low or zero. It
should be noted that in many cases the severity of a hazard cannot
be reduced (e.g. electrocution could always have a fatal outcome,
but the risk of it happening can be minimised by control measures).
Document Status
It is intended that this document is a working tool, and will be used to
record any additional hazards that are reported by user.
This assessment is designed to assess the risk to the following:
1. Members of the production crew
2. Performers
3. Members of the public
.
Severity
S
Risk
R
Minor injury
Injury requiring
first
aid
treatment
RIDDOR level
injury
Major
injury/fatality
Issue: 1
1
2
Very low / none
Low
0
1
3
Medium
2
4
High
3
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Hazard
1
Female
cam-lok Electric shock
large
enough
to
insert finger
2
Misconnection
phase cam-locks
3
Misconnection
of Single phase equipment 4
phase and neutral could remain live although
camlocks
the single pole mcb or
switches have been opened
or switched off.
Misconnection
of Equipment could overheat 2
phase and neutral and blow fuses, trip mcbs, or
camlocks
in worse cases, after
a period catch fire, if 400V is
applied instead of 230V.
4
Risk
Level 2B Training Manual
#
S R Control Measures
4
of Incorrect rotation of motors in 1
lifting equipment,
5
Misconnection
of Electric shock
phase and earth
cam-loks
4
6
Misconnection due Any of 2 to 5
to
change
in
electrical colour code
4
7
Potential
for Increased
potential
for 4
connection
of electric shock due to lack of
phases
before protective earth
connection of earth
Issue: 1
Notes
1 Female end always connected first
and disconnected last. Power never
switched on with female end not
connected. All supplies protected by
30mA RCD
1 Use
of
clearly colour
coded Direction of motors
connectors
always tested after
connection
and
before use
1 Use
of
clearly colour
coded Use of double pole
connectors and Neon indicators on mcb encouraged
equipment
to
indicate
correct
connection
1 Use
of
clearly colour
coded
connectors and Neon indicators on
equipment
to
indicate
correct
connection
1 Use
of
clearly colour
coded
connectors and Neon indicators on
equipment
to
indicate
correct
connection. All supplies protected by
30mA RCD
1 Continue using old red/yellow/blue At the present time
colours but promote awareness of cam-lock
new colour code
connectors
in
brown and grey are
not available.
1 Earth camlock always inserted first
and removed last
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CONCLUSION
Continued use of Cam-lok connectors is acceptable subject to
control measures specified in
Rows 1 to 7 above.
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Appendix C: USSU Risk Assessment – Loadstar Connector
USSU Technical Services
Lodestar Connector Risk Assessment
This risk assessment is for the use of 110v 16A Cee-Form plugs (to EN 60309-2)
when used in the control circuits of Lodestar theatrical hoists and similar products.
The risk assessment is prepared on the following basis, utilising advice provided by
the HSE:
Hazards
Identified by using previous professional experience to assess the continuing use.
Any eventuality that indicates a potential risk is recorded in this document. All
eventualities that have been considered but deemed to present no significant risk
are not recorded.
Severity
The severity of the outcome of any assessed hazard is allocated a rating, denoted in
the accompanying table by a numerical value (see below).
Risk
The likelihood of a hazard occurring, assuming that no additional measures are in
place to prevent such an occurrence. Again, a numerical value is used in the table.
Control Measures
Any further action taken by the equipment managers or users, with specific intention
of reducing the risk of any hazard to low or zero. It should be noted that in many
cases the severity of a hazard cannot be reduced (e.g. electrocution could always
have a fatal outcome, but the risk of it happening can be minimised by control
measures).
Document Status
It is intended that this document is a working tool, and will be used to record any
additional hazards that are reported by users
This assessment is designed to assess the risk to the following:
1. Members of the production crew
2. Performers
3. Members of the public
.
Severity
Minor injury
Injury requiring first
aid treatment
RIDDOR level injury
Major injury/fatality
Ref:
Electricity
Issue: 0.1
at
S
1
2
Risk
Low
Medium
R
1
2
3
4
High
3
Work
Act
1989,
Low
Voltage
Directive
(73/23/EEC).
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CONCLUSION
Continued use of 3-pole connectors is acceptable subject to control measures
specified in Rows 1-4, 6-9, & 11.
Use of 4-pole connectors removes the need to carry out the control measures as
above, but it is recommended that power is disconnected from all hoists when not in
use.
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Appendix D: USSU PAT Test Manual – Quick Reference Test
Procedure
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USSU Technical Services / Stage Crew
PAT test manual
It is a legal requirement to ensure the electrical safety of all electrical equipment and
cables. In order to achieve this USSU has an electrical safety testing scheme for
testing of portable appliances (PAT) by competent persons.
All equipment should be tested a minimum of once per year
Testing Procedure
Visual checks:
Cables:

Check the length of the cable for damage, nicks, exposed inner cores or
exposed copper.
Plugs and sockets:











The plug is not cracked or broken in any way
Open the plug or socket and check:
The strain relief is clamped tightly on the outer sheath of the cable; there
should be no inner cores visible beyond the strain relief.
The screw terminals are done up tightly.
There is no copper visible outside the screw terminal
The wire in the screw terminal has been twisted and fills the terminal (by
doubling back where necessary)
There are no stray strands of copper
The wires go to the correct terminals:
(Live - brown or black; neutral - blue; earth - green/yellow)
There is a little slack in the cables between the strain relief and the terminals
The correct rating fuse is fitted where relevant
The cover cannot be removed without the use of the correct tool
Cable entries to equipment:



Grommet or gland present and not damaged / perished
Cable firmly held by cable clamp with no inner cores visible (gently tug cable)
Outer sheath not damaged under cable gland
Lanterns:


Check for any burnt or damaged cables inside lantern
Check as for plug or socket
Equipment:

Vents and fans are clean, working and not clogged with dust
Cable PAT Tester
Do not test cables with neons such as 4 ways; use the equipment PAT tester.
Earth bond test:


Plug in both ends of the cable
Select the number of cores in the cable using the up / down buttons
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Level 2B Training Manual
Only cables with the same number of pins at each end can be tested (to test
spiders , join 2 together to form a "socapex").
If the cable has a 13A plug or an IEC connector then select the 5A test
For any other cable select the 25A test
Select the pass value for the cable length and size from the chart provided
Press the start button
The green pass light will light up in turn for each core
A red light indicates a fail
Insulation test:





Unplug the female socket end of the cable from the tester
Select the 5OOV test
Press the start button
The green pass light will light up in turn for each core
A red light indicates a fail
Equipment PAT Tester
Earth Bond test:
For class 1 (earthed equipment) only
 Plug the equipment into the PAT tester
 Attach the crocodile clip to an exposed metal (unpainted) part of the
equipment
 Select test 1 (earth bond)
 Press the test button
 Values of up to 0.2 ohms are considered a pass

For cables:
(It is ok to test cables with neons with this tester)
 Plug the cable into the PAT tester (possibly using an adapter)
 Plug a test lead with a suitable plug into the 4mm socket on the tester and
into the socket on the cable
 Select test 1 (earth bond)
 Press the test button
 Values of up to 0.2 ohms are considered a pass
 If the tester reads between 0.2 ohms and 0.5 ohms then check the cable size
chart to see if this is ok
Insulation test:
For class 1 equipment and cables:
 Plug the equipment into the tester
 Select test 2 (insulation)
 Press the test button
 Values of greater than 2Mohm are considered a pass
For class 2 equipment:
 Attach the test probe to the tester
 Touch the probe to an exposed metal part
 Test as for class 1 equipment
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RCD Tester
 Plug the RCD tester into the non RCD socket in workshop 1
 Plug the RCD into the tester
 Test at half the trip current - RCD should not trip
 Test at trip current - RCD should trip
 Test at twice the trip current - RCD should trip within specified time
NOTE
Equipment with the 3 neon "martindale" circuit will fail the insulation test, some
equipment has switch / key switch to disable the circuit and allow testing.
Equipment with mains filtering such as computers, lighting desks and some dimmer
racks will also fail the insulation test.
Test Label:





Fill in a test label with the date (O1/02/06 or Feb 06 not O1/02 or 02/06)
Fill in test label with your name or initials (choose so as uniquely identifiable)
Attach where possible to the plug end of a cable
Attach where possible to a piece of equipment near the electrical input
Ensure any old test labels are removed
Logging:






Scan the USSU Barcode
Enter the item description where necessary
Check the test date and re-enter if necessary
Select pass or fail
Enter your full name
Click ok
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