Periodic Electrical Testing of Installed and Semi-installed Audio Visual Equipment

Electroacoustic Systems Engineer

This document was originally written some time ago concerning problems that the AV industry experienced with substandard electrical testing in the equipment rooms and racks of AV installations, and the issues and equipment failures this created.

As things have developed in this field over the last 10 years, now is the best time to update this text to reflect the advances and improvements within the regulations and guidance.



1 Introduction.

Still to this day, there remains no single statutory instrument requiring or demanding that such installed systems and equipment racks are “PAT Tested”. While owners and operators are required under various statutory instruments to make sure the systems are safe to use, and that includes being electrically safe, none, to the point of writing says that installed equipment must be “PAT Tested” by an accredited “PAT Tester”, if we read the official guidance it is quite the opposite. Despite this, many of our customers are still being told by rogue operators in the “PAT Test” industry (Also local authorities, insurers, and fire safety professionals) that they must have all their electrical technical AV gear tested by a professional “PAT Tester” by law. This simply is not true, more to the point, to demand such a thing is fraudulent, and when considering the requirement for the electrical test operative to be competent it is often dangerous and in contravention of the regulations and guidance.

2 What the “law” says.

Duty holders have a legal requirement to ensure all aspects of the workplace, and public safety (including electrical) under the following statutory instruments.

  • Electricity at Work Regulations (EAWR) 1989;
  • Health and Safety at Work act 1974 (HSW1974);
  • Electricity at work act 1989;
  • Provision and Use of Work Equipment Regulations 1998 (PUWER 1998);
  • And under all statutory instruments implementing BS7671 (Requirements for Electrical Installations).

For “portable equipment” the new EN / CENELEC standard (BS) EN 50699 November 2020 sets out test methods that conform to the “PAT Test” methodology for “Recurrent Test of Electrical Equipment” but the scope of this standard does not encroach upon fixed specialist electro-technical systems such as racked AV equipment or other fixed items in control rooms.

Indeed, the IET Code of Practice “In-service Inspection and Testing of Electrical Equipment” (5th Edition) which generally follows EN50699 to the letter (Except for content relating to the use of non-polarised European “Schuko” type connectors) states very clearly in Appendix 7 the following, which must be carefully noted.

“Equipment racks and bays.
Items of equipment that could individually be considered mobile, which are used in a fixed location, are often installed in equipment racks or assemblies. Examples include IT servers, audio amplifiers and processors used for voice alarm and process control instrumentation equipment and similar.

This type of equipment is often mounted in 19-inch racks and individual items are often only removed for repairs or replacement. When considering the need for maintenance duty holders should consider the risk of equipment damage occurring if individual items are removed, undergo a formal inspection or test, and are then replaced. Damage could occur, for example to internal wiring if equipment is not located properly or faults could be introduced if terminations are not made correctly after replacement.

A duty holder may decide to treat such equipment as installed electrical plant, as they are not mobile and are not subject to the same risks of mechanical damage.

On that basis the equipment should be subject to ongoing test and inspection typical of an electrical installation.”

This guidance is very clear. Installed AV equipment is not to be treated as a portable appliance and should have its own risk assessed inspection regime carried out by specialist competent persons.

3 System labelling.

It is the duty of the installers to make abundantly clear that we now have clear guidance in Appendix 7 of the IET Code of Practice 5th Edition that the systems we install should not be interfered with by general “PAT Testers” and that by doing so they are in many ways in contravention of their own “Code of practice”, especially in regard to competence.

A Systems installer should also consider that venue ownership or management may change, or their own relationship with the owner of the equipment may end, and clear guidance on periodic inspection should be affixed to the equipment in regard to the periodic safety test and inspection by competent persons from our industry way beyond the foreseeable future.

In many circumstances if a system was interfered with by a “PAT Test operative” it may further invalidate other periodic safety inspection requirements, such as those related to the “certified” functioning of systems for the purpose they are installed. For example, were a life safety system recently inspected under the requirements of BS 5839 by a competent specialist and subsequently the amplifier system rack was taken apart and tested by a local electrician who felt it was their duty to “PAT Test” every electrical item in the building, it may well not function as expected when re-installed. If just one connector was misplaced it would be questionable whether it was now covered by any certification as to its functionality (for example under BS 5839) as technically the system or a large part of the system (or system wiring) has been removed and re-installed by the PAT test operative and should be treated as a freshly installed or re-installed system.

It has been noted in many cases where even entertainment equipment has been removed for periodic electrical testing in public venues and has been re-installed by the tester, they have failed to re-connect the fire alarm cut-out interface (technically the systems should have had break-to-mute contacts, (NC) but many did not) and the cut-out, and therefore the fire alarm, has been rendered ineffective. This system as installed now has not had any functional test by a designated person and no longer functions as a public evacuation system. Spotting this would rely on the venue manager actually playing music next time they do a routine fire alarm test, something that rarely happens.

The author has found this to have happened in at least 15 UK public venues subsequent to PAT testing being carried out, the cause of which was that the incompetent PAT Testing operative was ignorant of the function of the “extra” cable behind the equipment.

4 Competence.

It is incumbent upon all audio systems installers to clearly identify their equipment with regards to periodic testing requirements and to emphasise the need for it to be tested by a competent person.

Competence is clearly noted under section 5.4.2 of the IET Code of Practice In-service Inspection and Testing of Electrical Equipment 5th edition (Training and competence) it states, “The test operative should have an adequate understanding of the equipment to be worked on and practical experience of that system”. This is clear, a person not technically familiar with a system as a whole and not with a clear understanding of the consequences of their actions (or any errors) upon that system is not “competent” to test that system.

Section 10.8 of the IET Code of Practice In-service Inspection and Testing of Electrical Equipment 5th edition states that A functional check of the equipment under test should be carried out to see if the equipment is working correctly. Quite clearly in order to do this the person carrying out the test has to know what “correctly” means and be able to declare in a qualified manner that a system is working correctly. In a large-scale AV system such a check could be a very complex affair that involves running the system through all possible permutations of its functionality.
Section 10.8 goes on to require that the operative should understand the safe operation of the equipment and adopt suitable precautions to prevent damage or injury. To this degree if an operative were unable to understand the topology of multi-way audio systems, and the consequences of sending low frequencies to a high frequency driver then that operative would not be competent to carry out the task allocated to them and potentially damage the system under test. It is not adequate to assume each element of that system is an isolated unit and as such only requires to function in isolation, putting a low frequency amplifier on a high frequency driver is as destructive as mistakenly placing a 24-volt transformer back on a 12-volt lamp.

Testing examples.
Here follows some basic guidance on what aspects of system inspection we should routinely cover.

Further guidance of greater scope is provided by the IET in BS7671:2018 Guidance note 3 Inspection and Testing, and the IET Code of Practice – In Service Inspection and Testing of Electrical Equipment 5th Edition. (Also, in EN 50699)

What follows here is a basic outline of areas that generally need to be covered and how they apply to our industry equipment commonly used in commercial environments. Any specified numeric values are for generic example situations only and each user should refer to the relevant standards and their own assessments for actual values. All text is intended as a guide for an installer’s own procedures and in no way should ever contradict codes of practices or regulations published in regulatory documents. Examples are not exhaustive. Operational testing is not included here but should be included in any test visit or documentation.

5 Reasons for testing.

Any complex mechanical, electrical, or electronic system usually has a finite safe operating lifespan, and where it is subject to external influences will have a varying period of reliable safe operation before it requires some form of check by a skilled person to rectify any functional problems related to wear and remedy any faults. (Rather akin to the ongoing performance and safety of a well serviced and regularly inspected car compared to a badly serviced never inspected car) Most systems consist of a mix of consumable items, wear items, perishable items, and items that should last way beyond the foreseeable lifespan of the system.

There are many things which may influence these items such as the wear and tear of normal use, external human factors such as misuse, abuse, error, malicious interference, or unforeseen external factors such as attack by rodents, birds, or insects, and environmental issues such as flooding, dust, or extreme heat.

Additionally there are aspects where poor installation, such as inadequately secured terminals, over stressed cables, cables subject to mechanical abrasion, or items operating too close to their design limits may all cause premature occurrence of unsafe or fault conditions.

As a system progresses through its designed lifespan any of these, or other, aspects may change the system’s degree of operational safety from inherently safe to inherently unsafe.

In addition, when systems suffer day to day failures and in-the-field repairs are carried out (Often by persons other than those who supplied or installed the system) many dangerous fault states can be introduced by these supposed repairs. Repairs may often be unforeseen and expensive and there is always a tendency to opt for the fastest or cheapest methods just to get things running “now” rather than the safest or most compatible.

Periodic safety testing is a very effective way to reduce risk and prevent or remedy situations where users and people working upon a system can be put at risk of electrical harm. It is therefore essential as a duty under the statutory instruments listed above to carry out a fully effective risk assessment with an experienced and competent person who understands the possible fault situations and interference which a system may experience during its lifespan and implement the results of that risk assessment in full.

6 Electrical Safety Risk Assessment.

The original installer, or in the case of previously installed equipment by persons unknown, the first competent tester, should determine by means of experienced assessment the necessary test periodicity for various parts of the system.

Such assessments should be based upon the likelihood of physical damage, physical wear, physical or electrical degradation of connections, harsh environments, age of equipment and amount of user interaction.

Users themselves should be categorised into high-risk non-specialist persons, and low risk specialist persons, such as maintenance staff or specialist engineering staff and risk evaluated accordingly.

Electrical Safety testing frequency should be clearly displayed on, or inside the equipment enclosure and it should be clear to those responsible for the system when the period has expired. Many items which are enclosed, protected, and not part of any user interface would normally, if well installed in a correct environment, not degrade, or be damaged to any degree over the lifespan of the equipment. The majority of electrical cables and connections would receive no user contact, nor be exposed to physical damage. It would be more than adequate for these items to be inspected no more than once every 5 years, from the point of the first installation electrical safety test as long as the environment is good.

Items installed in user areas should be tested based on the frequency and nature of use. For example, a DJ style music playback console installed in a fixed position in a church hall that is used for half an hour a month by the vicar is not likely to be at as much risk as the same console brought out daily to an outdoor bar used by freelance DJs who are permitted to drink in the vicinity of the equipment. Common sense would dictate that the first example would be adequately served by maybe as much as 3-year testing, while the second example would be better served by 6 to 12 month testing (or less if the environment is deemed unusually harsh).

Additionally, quality and suitability of equipment and distribution components may have a bearing on expected longevity, components running close to their maximum capacity may well need more frequent monitoring. Older equipment may well require more frequent monitoring than new equipment due to simple ageing effects of plastics and wear components. Only a competent system designer or installer with adequate experience in the industry is capable of correctly specifying test intervals based on actual risk. Similarly, a competent field tester is able to recommend any alteration to test intervals based on any changes of circumstance, age, or wear they may see when performing tests.

7 System Definition.

All items interconnected to form a system which processes a signal, or in many cases, audio, video and effects lighting, constitute a single integrated item of equipment known as The Sound System, The Sound and Lighting System, or The AV system. Where these systems share audio, video, data or other similar cabling, they are electrically interconnected (often by means of cable screens or drain wires) so must be treated as single integrated systems. It is worth remembering that parts of the same system may not even be in the same building. In the example of conference centres and football stadia, the systems often spread from building to building yet remain electrically interconnected. No individual item of such a system would ever be considered an appliance in its own right and the perfect functioning of such an individual element is never to be deemed to be correctly functioning until it is tested in conjunction with the system as a whole.

8 Electrical Testing.

The purpose of electrical testing is to ensure that the users and their customers are kept safe from any risks associated with the use of electricity. These risks are principally electric shock where a person comes into contact with the mains current, fire where arcing of current between conductors causes a source of ignition (or where a conductor or connection is subject to excessive load so causes thermal failure of the insulation), and equipment failure through loss of electrical current when the system is performing a critical task.

Any electrical test should cover the safety of all these areas thoroughly without fail whilst ensuring minimum risk is encountered between testing intervals.

9 Equipment Type Classification.

Under portable appliance testing standards there are two main types of equipment under test which alter how a test is carried out. Before any test is carried out this MUST be identified to prevent damage or destruction of the item under test.

Firstly, the default standard item, which is general electrical plant and machinery, usually solely consisting of a plug, a cable, a switch a heating element, or a motor or light.

Then, there are other electronic-electrical items more complex and sensitive, which would be damaged by high current, high voltage, testing. This equipment was initially deemed to be computerised equipment and as such the test for this equipment was designated an IT test. This test is actually incorrectly named as rather than just IT equipment the majority of electronic processing and control equipment falls within this designation. This largely exposes the origin of the PAT test in offices, tool hire, and hospitality spaces as a true appliance test and shows how it has slowly expanded into regions filled with electronics where it was not originally envisaged it would be carried out. It is extremely unhelpful that the electronic item test is simply classified as “IT equipment” as millions of pounds of electro-technical equipment will have already been damaged because of this designation error. There was one point where the UK’s largest night entertainment chain was having thousands of pounds worth of system DSP processors rendered inoperative multiple times per week by this erroneous classification of “IT Equipment.

Electronic equipment is basically anything that includes semiconductors (or other very low voltage components) and often has filtering components between power line connections and chassis ground for the means of both surge protection and high frequency interference filtering. It is equally, and often more fragile with regard to excessive voltage and current through these filters as any IT equipment.

For this reason, everything we use in the audio installation business with the exception of passive power distribution units MUST be designated IT equipment for the purposes of testing from the very beginning unless we know for sure it is general purpose simple electrical equipment, or the manufacturer instructs that a standard “PAT” test can be carried out. This means that no item except a passive power distribution unit should be subject to a high voltage insulation “flash” test or provided with any voltage above that for which it was designed. Most modern equipment can withstand significant earth conductor test currents, certainly equipment made to modern standards, but care MUST be taken, still ,especially with older or more complex devices that may have had electronic components before carrying out such tests. Great care MUST be taken when using earth current probes that the earth current test is being carried out on the actual earthed chassis and not some other non-earthed metallic parts (Like an antenna) as this may destroy the equipment under test.

Many items, even class 1 equipment can contain exposed metallic parts that are not supposed to be connected to the protective earth conductor, and through which the passage of a high current earth continuity test current would destroy the equipment. Just because a piece of equipment is class 1 and just because a visible part is conductive does not always mean an earth conductor continuity test can be carried out safely from that part or is a valid test. The test operative MUST ensure that the earth continuity test is carried out from a designated probe point or find alternative methods of verifying the electrical safety.

10 Protective Bonding.

Where potentially conductive surfaces which may come into contact with live internal conductors in a fault situation, such as metal enclosures, are potentially exposed to the person, they should be bonded to earth as required in electrical regulations, or adequately isolated from potentially becoming live as required under Class 2 equipment standards. This bonding should be carried out under current electrical regulations at the time of manufacture or installation Each item of individual electrically supplied equipment must be connected to earth through its own power cable if it is not an item of class 2 equipment. Class 2 equipment must exhibit reinforced insulation or adequate separation of any conductive parts.

Signal cable screens and rack bolts are NOT acceptable forms of safety bonding and the installer should never consider this as an acceptable substitute for an electrical safety bond.

Enclosures, conduits, and other non-electrical metal items should be independently bonded to earth as stated within national or local codes and this bond should be periodically tested under the control of an effective risk assessment. Periodic testing must ensure that the integrity of the safety electrical bond is good, and that all bonding conductors are well connected.

Care MUST be taken to ensure that conductive parts that are not intended to be earthed such as antennae or control conductive touch keys are not subject to any electrical testing.

Where multiple earth paths are present through signal cables it is recommended to temporarily disconnect all signal cables that may supply additional grounding in order to perform an effective safety electrical conductor test.

It is not necessarily recommended to strip whole systems out of racks to individual components on the bench in order to test, as this is problematic in itself and will not increase system safety to any significant extent. However, if items such as power amplifiers and signal processors are inspected infrequently it will be necessary to periodically clean them and verify that fans are working. This in itself should be done by removing and opening each item to remove layers of dust or fluff from heat sinks and fans, prolonging component lifespan and reducing the chances of reduced performance. This is an ideal opportunity to perform a full electrical test in isolation on each unit and would certainly be recommended once every five years in all but filtered-air fed equipment rooms.

It is worth noting that many unscrupulous installers or repair technicians will lift the supply earth to the equipment chassis of various components to try to remove induced interference currents that cause a hum due to bad system design. This is not only contrary to electrical regulations, but it is potentially very dangerous (and has killed many musicians on stage) as fault currents may travel through signal screens to user held equipment, any equipment found to be in this condition MUST fail testing and be re-cabled or removed from service in a way that it cannot erroneously be re-used.

Whatever form of testing the operative sees fit to use, MUST effectively demonstrate a robust safety electrical connection to each piece of equipment that requires one.

It is at the discretion of the skilled and competent tester as to what degree of detail an earth bond test on a pre-assembled multi-item unit (such as a rack) is carried out. Whether a single whole system test from the main supply to chassis (or multiple places on that chassis such as each item) is adequate, or whether it is required to test each item in isolation, this can depend upon the possibility that individual earth connections to items may fail, or whether interference is likely and periodicity of the tests. It may be rather excessive to regularly wholly dismantle rooms full of racks to check earth continuity to each amplifier but there may be comparative value methods where a skilled operative can spot any anomalies to individual items and it be ensured that in any circumstance all measurements are well within the limits specified in the IET code of practice, BS 7671, or EN 50699.

11 Insulation integrity.

To detect any insulation breakdown and potential arcing, all cables and applicable appliances should be tested for leakage between conductors. In audio systems any significant leakage may be the cause of serious degradation of the audio signal. Often the system will become unusable long before it will become electrically dangerous such is the sensitivity to reference ground interference.

BS7671 very wisely recommends the use of AFDD (Arc Fault Detection Devices) on all new installations, this recommendation would be wise to follow as not only would an AFDD prevent potential system fires, it will also probably prevent any electrical borne interference from bad contacts or insulation breakdown developing and causing audible problems on AV systems many of which are in places subject to rodent damage or mechanical damage.

As no item of common AV equipment may be safely flash tested, only a low voltage low current test to chassis can be performed as with designated IT or surge protected equipment. It is recommended not to exceed 250V in most cases.

Due to the sensitive nature of most audio equipment to unwanted reference ground currents, it is likely that this test will never yield results on an item that is not already deemed to be malfunctioning in an audio or visual manner.

It should be noted that in unmonitored situations, such as induction loop systems, we may well see an electrical safety test picking up serious operational problems that may otherwise have gone unnoticed.

The testing operative should decide the most appropriate method of testing (if required) for the equipment before them. It should be remembered that various forms of interference filters inside equipment will normally conduct certain frequencies and currents between line and earth in normal use and may cause measurement error issues with certain methods. Even with functional testing these currents may indicate a possible fault where there is none.

Many switched mode power supplies can induce relatively high ground conductor currents of lower voltages at higher frequencies and the filtering circuits can sometimes even render insulation tests invalid despite being in a perfectly safe functional state.

It is recommended that tests for the presence of earth conductor leakage currents or touch current tests be used where higher voltage insulation tests are neither possible nor desirable.
In many cases, with items not containing electronic components, high voltage testing of the power distribution components and leads will be adequate.

The test operative should assess and decide the best form of verification to use which satisfies testing requirements in these circumstances, many better measurement devices offering a range of tests such as substitute leakage tests, touch current tests, or earth conductor leakage tests.

It can sometimes take a great deal of measurement and communication with manufacturers to establish if ground (earth) conductor currents are within design specifications.

12 Exposed terminals.

Enclosures and racks that are not both fully sealed against human contact AND are seen to carry high voltage warning labels, may not be allowed to have any form of exposed current carrying electrical terminals or connection blocks inside, such as “choc block” barrier strip, DIN rail power terminals or similar. This includes open DIN rail power terminals on the exposed rear panels of some sequential power-switching units. This is especially so when it may be expected for an engineer or operator to be required to fault-find inside the energised rack or enclosure in poor access or lighting conditions.

Any unit not designated as a 240V or 415V internal hazard AND secured from human contact by means of key or tool, which has exposed electrical terminals inside, MUST fail an electrical safety test based on the presence of exposed live terminals.

This is especially critical in instances such as DJ boxes or control rooms where a local “switcher” unit may be fitted in a rack where a less skilled operative may go fault finding and encounter such a unit. If a neutral conductor had fallen from such a unit and be hanging in the rack the operative may inadvertently come into contact with that now live cable and receive a significant shock. Thankfully such connections are now becoming consigned to history, but they were once common sight in older installations.

Any item of equipment that may be remotely energised or energised from a timer system should be clearly labelled as such and means of local isolation for maintenance be provided.

13 Cables and distribution.

Where power leads and passive power distribution systems are used, they should be subject to standard electrical testing. All BS1362 fuses should be correctly rated for cable and connector ratings only (Not the power consumption of the connected equipment). Leads and distribution strips should be tested for high current continuity and may also be high voltage insulation tested.

All items should be visually inspected for suitability and damage. It should be taken into consideration that originally installed items may have been substituted by others, equipment may have been upgraded, and items may have been removed from the system since original installation. Therefore, it should always be checked that the current capacity of supply cables, distribution strips, and supply breakers is adequate. Each individual outlet should be tested as poor contacts can develop when corrosion or heat affects the spring properties of some types of lower quality socket contacts. With cheaper items many BS1363 distribution strip sockets can become warm and thermally damaged well within their rated current capacity, especially when subject to distorted current and harmonics.

It is important that all such outlets are fully tested periodically and where poor-quality (Shall we say “cheaper”) components are used, it may be wise to shorten the test interval or replace them with a more suitable more robust item. Plugs and sockets with any kind of visual sign of thermal stress should be visually failed regardless of the results of electrical testing. Distribution systems with active or remote control should be tested carefully in accordance with their design and layout taking care to avoid any testing that may stress control circuits and items such as programmable logic controllers or solid-state relays.

Any manufactured (not custom components) power cables or connectors that are not correctly marked with the required standard mark (Such as CE or BS or similar) or are assumed to be “counterfeit” should be removed from service as they do not meet the legally required standards and may be prone to premature failure or even be a source of fire. Fake BS1363A plugs and sockets being a prime source of concern.

14 Supply.

Correct and safe operation of any complex and sensitive equipment, such as an audio system, is reliant upon a good clean electrical supply and as low resistance as possible earth path. It is pointless ensuring protective earth bonding within the system if the supply earth is poor or missing. In large commercial installations, the electrical supply systems often suffer far more modification and physical interference than fixed installed audio systems. It is imperative that when testing larger installations, the electrical supply integrity is verified as part of the system testing. The supply in every case should be checked to be compliant with BS7671;2018 and be tested in accordance with the requirements of BS7671;2018 guidance note 3 “Inspection and testing”

A system cannot be signed off as safe if there is no protective earth supplying the system as a whole, or the supply properties are inadequate.
Where different parts of interconnected systems are fed from different sources it is essential to have as similar as possible source impedance on the grounding path and insignificant potential difference between each system’s grounds. Significant variations in these parameters will cause a possible potential difference between equipment sections and allow current to flow through signal cable screens and often audio reference ground paths causing signal degradation.

It is most important in large installations to note any significant differences and ensure low supply earth loop impedance at all locations (or between locations). In large systems with mainly electro-magnetic amplifier power supplies, it is also imperative to ensure that the supply lines have very low L-N source loop impedance to prevent voltage drop and neutral shift with amplifier transient current demand. This often involves over sizing cables and using motor rated (Type D) circuit breakers. System electrical testing in such circumstances should involve powering up all items simultaneously as though recovering from a power failure (this is often best done using a main switch). No circuit protective devices should be tripped by the turn on surge if correctly specified. It is highly recommended that any electrical safety inspection of large-scale systems includes documenting and non-intrusive verifying of the system electrical supply at the system rack and console connection points in addition to any other test on these lines carried out by others. Values, which are cause for concern, should be discussed with the site electrical contractor and should, if out of usual range, constitute a test fail until rectified.

In smaller installations where only a few BS1363 connections are used it is important to inspect these for damage and ensure that rack or console supply leads are not routed as to be subject to damage or cause trip or fall hazards. It is required that systems should not be fed from extension reels.

15 Hardware.

All enclosures, consoles, and equipment should be visually inspected for electrical safety.

Inspection should look for open holes exposing live parts, missing covers, severe cracks, open panels, doors that should be locked, missing warning notices, and any bypassed interlock protection cut-off switches. All equipment should be well ventilated and well clear of flammable materials, all enclosure fans should be clean and fully working without any binding or rattling. Special attention must be paid to the use of skeleton racks, which have no sides and expose all internals. These racks may be far more prone to interference if located in anywhere other than a dedicated locked room, In such cases it is recommended that test frequency be increased or sides be fitted in this case.

16 Operation.

All equipment should be inspected for correct operation and functioning upon completion of the testing. Testing should include a full load test, which should be to maximum safe system output. It should be verified that no circuit protection device should activate here. The tester should ensure that all devices are powered from the intended source circuit and that no device has been wrongly reconnected in the process of testing. Sequential switching and zoned or timed power control should be verified to work as intended. Every input and output device should be verified as correctly working before the test is finally signed off.

It is highly recommended to combine system electrical safety inspections with a full system functionality test, and in many cases, it is diligent to fully test system functionality after any significant disassembly to reduce the embarrassing and expensive event of being called back after electrical tests to fix minor faults or omissions caused by the electrical test. It is recommended that this (system functional condition) be documented and presented to the customer.

17 Documentation.

Upon completion, the customer should be issued with a certificate issued by a competent person detailing the tests carried out, the results of the tests, and the duration to the next due test. The customer may well require these documents to produce for licensing, insurance, and fire inspection purposes.

18 Test operative accreditation, qualification, or proof of competence.

Within the scope of the regulations and guidance provided by the IET, and other bodies it, is required that in all circumstances the test operative is able to display competence in both the fields of electrical testing, and relative to the specialised nature of the equipment under test when that equipment requires specialist knowledge to operate, or work upon.

It would certainly be required that the requirements of the IET Code of Practice “In-service Inspection and Testing of Electrical Equipment” (5th Edition) Section 2 Page 19, “Competent Person” are met in full.


  • An adequate knowledge of electricity.
  • Adequate experience of electrical work
  • Adequate understanding of the system to be worked on and practical experience of that class of equipment.
  • An adequate understanding of the hazards that may arise during that work and the precautions that need to be taken.
  • The ability to recognise at all times whether it is safe for work to continue.

In addition to this IET requirement it is essential in demonstrating competence that the test operative has adequate ability to verify correct functionality of the system subsequent to testing, and to understand and ensure that all possible functions and configurations are operating correctly.

This may mean entering and using control configuration software to achieve these criteria, and so require the test operative to have adequate competence to do so without risk of misconfiguration or damage.

The IET Code of Practice “In-service Inspection and Testing of Electrical Equipment” (5th Edition) goes on to clarify in section 5.4.1 the levels of competency specified by The HSE in HSG107 Maintaining Portable Electrical Equipment.

Under Level 1 (pass-fail test device operative) and Level 2 (test system displaying numerical results which require interpretation) and elaborates that a Level 2 operative “must have an understanding of electrical and electronic principles, safe isolation procedures, and safe systems of work, which in some cases may only be derived from previous knowledge, training and/or installation of the equipment they are to inspect and test.”

From this it would be reasonable to require that a “Competent test operative” should be classed as “Level 2” and display training, education, or experience in electrical testing principles, (and the test equipment they are using) along with training, and experience in installation and operation of the systems they are working upon. Anything other than this is in contravention with the IET Code of Practice “In-service Inspection and Testing of Electrical Equipment” (5th Edition) and all statutory instruments that implement the code of practice.

Simply because a “PAT Test operative” who is a very fine expert in testing kettles, printers, vacuum cleaners, and TVs, has an amplifier, speakers, soundcard, Blu-ray player and “media centre” at home does not in any way shape or form display any form of competence under any statutory instrument or guidance to go testing the content of professional installed AV system racks or consoles.

However much pressure they are under from their employers to get as many paid tests done as possible in one visit for one customer they are definitely operating in contravention to the regulations and guidance, and probably fraudulently claiming to provide a service they are not competent to provide. Only if said operative were able to prove and display competence in the AV installation field related to the systems they are testing would they be defined as competent under the IET/HSE criteria.

The IET publications in general are on the side of the AV industry specialists as a whole (And other specialist installers) we just need to better communicate this to our customers.

There is a very important role for electrical safety testing in the correct environment but similarly we should not allow a financially incentivized mission-creep to cause that industry to incompetently encroach upon specialist equipment which requires specialist knowledge to test safely.

Furthermore, we need to prevent the fraudulent claims by some in the electrical testing industry that they must test the AV gear because “It’s the law”.

Clear labelling of equipment regarding test procedures, operator competence, and test intervals will go a long way to address this issue.  Nobody would ever let the “PAT Testers” PAT test the lift control gear in any building after all would they? Would they?