Test and tagging
It has been suggested that this article or section be merged into PAT Testing. (Discuss) Proposed since February 2010. |
Test and tagging is a generic name given to the process of visually inspecting and electrically testing in-service electrical equipment for personal use and/or safety. Colloquially, it is also referred to as; tagging, test tag, test and tag, electrical tagging, appliance testing, portable appliance test or lead tagging.
The aim of test and tagging is to determine if the appliance is electrically safe for personal use. The appliance undergoes a visual inspection for defects such as damage or missing components and a number of electrical tests to measure earth continuity, insulation resistance and polarity.
In Australia and New Zealand, this is done using the Standard; AS/NZS 3760:2003 “In-service inspection and testing of electrical equipment” as a reference document.
Because there is a document published on this topic by a reputable source, regulatory bodies that enforce State and Federal Occupational Health and Workplace Safety Acts and Electrical Safety Acts and Regulations within Australia and New Zealand, may list or encourage the use of this Standard as a minimum requirement.[1]
Test and Tagging is sometimes referred to as PAT Testing (UK). This terminology was first used in the United Kingdom A Portable Appliance Test or PAT, is a process by which electrical appliances are routinely checked to see whether they are safe. The term PAT - PAT Testing - more accurately describes the actual test equipment used by technicians (not the appliance being tested) as it is generally hand held and/or portable.
In the United Kingdom, the law requires is that the appliances are safe (as far as is reasonably practicable). Guidance from the Institution of Electrical Engineers (IEE) and the Health and Safety Executive (HSE) suggest initial intervals for combined inspection and testing that range from three months (for construction equipment) to five years for inspection and never for testing (certain types of appliance in schools, hotels, offices and shops). [2]
However the original United Kingdom term PAT (Portable Appliance Testing), is somewhat misleading as test and tagging can involve inspection and testing of fixed appliances, such as wall mounted air-conditioners that are not "hard wired" etc. Possibly a more accurate term for the whole process is In-service Inspection & Testing of Electrical Equipment.
Contents
Who can test and tag?
Test and Tagging shall be conducted by a “competent person”;
“A Competent Person is one who the Responsible Person ensures has the necessary practical and theoretical skills, acquired through training, qualification, experience or a combination of these, to correctly undertake the tasks prescribed by this Standard.”[3]
The Standard also notes a Competent Person is not required to be a registered or licensed electrical practitioner (ie electrician). However local Legislations, Industry Standards and/or Codes of Practice may have different requirements and therefore the better practice should be adopted.
Mandatory or optional
AS/NZS 3760:2003 In-service inspection and testing of electrical equipment as a stand-alone document is not mandated because it is not Legislation.
Why test and tag
Test and tagging because of what is printed in Occupational Health and Workplace Safety Acts and Electrical Safety Acts and Regulations around the Country[1] that require “an employer to provide and maintain a safe workplace”, which includes maintaining safety in the use of electrical equipment in an attempt to prevent hazards such as electric shock and damage to property and/or livestock.
Because there is a document published on inspection and testing of electrical equipment by a reputable source, regulatory bodies that enforce State and Federal Occupational Health and Workplace Safety Acts and Electrical Safety Acts and Regulations within Australia and New Zealand, may list or encourage the use of the Standard AS/NZS 3760:2003 In-service inspection and testing of electrical equipment as a minimum requirement.[4]
UPDATE: As of the 1st of April 2010 the New Zealand Electricity (Safety) Regulations 2010 require an organisations portable (not hard wired) electrical equipment (Low Voltage) to be tested or protected in accordance with the following:
1. Tested and tagged in accordance with AS/NZS3760, or 2. Protected by a portable Residual Current Device (RCD) that has been tested in accordance with AS/ZS3760, or 3. All sockets in final sub circuit are protected by an electrically safe RCD.
This change in legislation now requires either full RCD protection or equipment tested & tagged or a combination of both.
What needs testing?
The Standard specifies procedures for the safety inspection and testing of low voltage single phase and poly-phase (e.g. nominal 240V and 415V) electrical equipment, connected to the electrical supply by a flexible cord and/or connecting device, which is new equipment placed into service for the first time, is already in-service, has been serviced or repaired, is returning to service from a second-hand sale, or is available for hire.[5]
The Standard also specifies procedures for Residual Current Devices / Safety Switches.
The Standard notes a number of exemptions including;
1.1.1 This Standard does not apply to electrical equipment (such as suspended light fittings), at a height of 2.5m or greater above the ground, floor or platform, where there is not a reasonable chance of a person touching the equipment and, at the same time, coming into contact with earth or any conducting medium which may be in electrical contact with earth or through which a circuit may be completed to earth.
1.1.2 This Standard does not apply to equipment which would need to be dismantled to perform the inspection and tests specified in this Standard.
NOTE If, for some reason outside the scope of this Standard, equipment must be dismantled to verify safety, this action must be performed by a technically qualified person.
1.1.3 Functional checks are not considered part of a safety evaluation and therefore not included in this Standard.
1.1.4 This Standard only applies to equipment in-service at a place of work or public place, or offered for hire.
NOTE For example, this Standard does not apply to demonstration stock in retail or wholesale outlets.
1.1.5 This Standard does not apply to fixed or stationary equipment connected to wiring that forms part of the electrical installation and falls within the scope of AS/NZS 3000.
1.1.6 This Standard does not apply to equipment whose nature is that of a medical device as defined in AS/NZS 3551.
Examples of common electrical appliances that would require testing;
- Computers, printers, monitors, photocopiers, fax machines, power tools (drills, saws, grinders, compressors etc), battery chargers, desk-top lamps, vacuum cleaners, floor polishers, extension leads, power boards, TV's, radios, some air conditioners, refrigerators, portable flood lights, heaters, jugs, toasters, hand dryers, washing machines, radio transmitters, modems, CD players etc.
An anomaly exists between the treatment of new equipment depending on whether it is entering into service in Australia or New Zealand.
- In Australia, new equipment entering service for the first time does not need to be inspected and tested as the supplier is deemed responsible for the initial electrical safety of new equipment. Some users simply apply a generic "new to service" tag to the lead as a minor precaution / warning. Despite this exemption, the best practice would be to have new equipment inspected and tested.
- In New Zealand the same equipment shall be inspected and tested on entry to service.
Inspection
The Standard defines a number of checks that shall be made by visual and physical inspection of the appliance, including obvious damage or defects in the accessories, connectors, plugs or extension outlet sockets.
Experience has shown that greater than 90% of defects are detectable by visual inspection.[6] Typically this relates to damaged plugs/sockets, flexible supply lead, especially at flex point where lead enters plug/socket.
Testing
The tests an appliance is required to undergo will depend on the type of appliance, it's electrical Class and subject to a risk assessment by the technician. ie it may not be safe to perform a leakage current test which powers up the appliance, such as a grinder, if it can not be secured to a bench; an insulation resistance test may be a safe option.
Earth Resistance Test==
This test shows the resistance offered by the earthing rods with the connection leads.Various testing instruments are available for earthing resistance tests.The earthing resistance should be less than 1 Ohms.
Earth continuity test
The equipment shall have a measured resistance of the protective earth circuit, or the earthing conductor of an extension cord or appliance cord set, which does not exceed 1Ω.[7]
Testing is performed using an ohmmeter or PAT tester;
- Using the ohmmeter to produce a reading;
- Using a PAT tester under the following conditions;
- 12V maximum, test current range 100mA to 200mA - commonly known as "earth continuity test" or "screen test" and/or
- 12V maximum, test current 10A - commonly known as "routine test" and/or
- 12V maximum, 1.5 times rated current of appliance or 25A, which ever is greater - commonly known as "type test" or "bond test".
The choice of which test(s) to use is at the operator's discretion as there is merit in each test for given situations, however the "routine test" is seldom used by competent persons as it simply replicates existing conditions for the (240V/10A) appliance and therefore the results are regarded as being of little test value.
Insulation resistance test
A leakage current test performed at rated voltage with values not exceeding 5mA for Class I appliances or 1mA for Class II appliances.[8]
Alternatively, measure insulation resistance values do not exceed 1MΩ for Class I and Class II appliances at 500 V d.c. or alternatively, to avoid the equipment apparently failing the test because the metal oxide varistors (MOVs), or electro-magnetic interference (EMI) suppression has triggered, for equipment containing voltage limiting devices such as MOVs, or EMI suppression, at 250 V d.c.[9]
Leakage Current testing is performed using a PAT by applying a nominal voltage to the live conductors (active and neutral) of an appliance, and placing 0 volt reference on the earthed parts of a Class I appliance or the external metal parts of a Class II appliance;
- Nominal voltage is 230V AC. (therefore it can not be performed with a digital multimeter)
Insulation Resistance testing is performed using an ohmmeter or portable appliance tester by applying a nominal voltage to the live conductors (active and neutral) of an appliance, and placing 0 volt reference on the earthed parts of a Class I appliance or the external metal parts of a Class II appliance;
- Nominal voltage is 500V d.c (250 V d.c. may be used for equipment containing MOVs / EMI filtering)
A deficiency of the Insulation Resistance (500V/250V d.c) test is that the d.c voltage will not activate electromagnetic switches or internal relays etc that are common in many modern power tools, computers, TVs etc and therefore it can only test the appliance up to that point. Appliances with these components / design should be tested used the leakage current test.
Polarity check
Polarity testing is a simple test that can be carried out using a polarity tester to determine whether the active and neutral of the plug end are correctly connected to the corresponding terminals at the socket end. [10] Note: The earth is tested during the earth continuity test.As per BS7671, the phase(or Hot) cable should connect with right hand side terminal of the socket(if we face the socket outlet).
Plugs
- The order (polarity) of the pins of a three pin flat pin plug, to their connections, shall be Earth (radial pin – green/yellow wire), Neutral (light blue wire) and then Active (brown wire), in a clockwise direction, when viewed from the front of the plug looking at the pins.[11]
Cord extension sockets
- The order (polarity) of the socket apertures of a three pin flat pin socket, to their connections, shall be Earth (radial pin – green/yellow wire), Active (brown wire) and then Neutral (light blue wire), in a clockwise direction, when viewed from the front of the socket looking at the apertures.[12]
RCDs /ELCB's / Safety Switches
There are two tests methods to be used;
Press Button
This test requires specific test equipment RCD tester :
The RCD tester should be connected with the socket, with earth terminal(must !!) and 1)select the testing range 'delta' (10mA,30mA,100mA,300mA,500mA). 2)Select half delta range, and press TEST button - the RCD should not operate, this ensures from the nuisance tripping. 3)Select delta range, and press TEST button - The RCD should operate, with in m Sec for 50Hz,230V system( as per BS 7671)
Applied current
This test requires specialised test equipment, knowledge and training;
- A current, equal to the rated tripping current, shall be “suddenly” applied between active and protective earth and the operating time measured[13] with maximum trip time 40ms for Type I and 300ms for Type II.
In addition to this, many technicians also test;
- using 1/2 (half) the rated tripping current to detect nuisance tripping.
- using 5 times rated tripping current, with trip times reduced accordingly, to simulate high current exposure.
- under 0 degree and 180 degree phases
Best Practice is to test the RCD under 1/2, 1X and 5X rated tripping current, each at both the 0 degree and 180 degree phases.
Retest intervals
Table 4 of the Standard defines inspection and testing intervals for electrical equipment. In general, they range from 6 months to 60 months and are based on the type of appliance, Class and environment it is normally used in. However, these are guidelines only and subject to a risk assessment. Regulatory authorities, other Standards, workplace safety requirements or manufacturers’ instructions may specify intervals appropriate to particular industries or specific types of equipment ie construction and demolition sites require three monthly retest intervals for all electrical appliances used on-site.
Results from inspection and testing
Following testing, compliant equipment shall be fitted with a durable, non-reusable, non metallic tag or other indicator that shall include-
- (a) the name of the person or company who performed the tests;
- (b) the test or inspection date, and may also include a re-test date.[14]
Where in-service inspection or testing identifies equipment which fails to comply with the inspection and/or testing criteria, the equipment shall be appropriately labeled to indicate that the equipment requires remedial action and warn against further use, and withdrawn from service. The choice of remedial action, disposal or other corrective action shall be determined by the owner or the person responsible for the safety of the site.[15]
Most tags are applied approximately one hand span away from the plug end of the flexible supply cord to avoid handling damage and stress point loosening.
The tag can be applied to the body of an appliance if needed.
Record keeping
There is no specific requirement under the Standard to keep records of inspection and test results aside from the application of tags.
The Standard notes:[16]
2.5.1 Where records of test and inspection are kept, the following should be recorded:
- (a) A register of all equipment;
- (b) A record of formal inspection and tests;
- (c) A repair register;
- (d) A record of all faulty equipment showing details of services or corrective actions.
NOTE 1 Electrical and/or occupational health and safety regulators may require documentation to be kept in some or all cases.
NOTE 2 Where organizations perform voluntary additional inspections and tests, records of such should be kept.2.5.2 Where records are kept, they should be retained for seven years, or such period as required by the specific regulations.
2.5.3 Where a risk assessment has been performed in accordance with Clause 2.1.1, all documentation
shall be retained for seven years or such period as may be required by the relevant Regulator.
See also
References
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- Standard: AS/NZS 3760:2003 “In-service inspection and testing of electrical equipment” ISBN 0-7337-5758-8
- Best Practices in Testing & Tagging of Electrical Equipment to AS/NZS 3760:2003. (Zahra & Virieux 2007) ISBN 0-646-46140-0
External links
- Best Practice Standards
- Case Studies: Equipment status inspection tags
- PAT Info.co.uk
- Official HSE Publication Guidelines on Inspection
