ABN: 55 871 235 025
INFO SHEET 2
APPLIANCE TESTING – ELECTRICAL SAFETY TEST
Australian Standard AS/NZS 3760:2003 “In-service safety inspection and testing of electrical equipment”
In brief, the Standard specifies all equipment that is plugged into a 240 volt power outlet, has an Appliance Safety Test. This includes separate testing of the equipment’s power leads, as well as extension leads, power boards and double adaptors.
It specifies the frequency of testing – for most laboratory equipment it is normally every 12 months (as well as after any repairs).
A summary of the tests is;
1. Visual and physical inspection for obvious damage or defects
2. Earth Continuity (Class I equipment only) measures the resistance between the supply earth pin and any exposed metal parts, using a current of 25 amps. The resistance shall not exceed 1W.
3. Earth Leakage Current (insulation test, Class I equipment only) 500 V dc is applied the live supply connectors and the supply earth pin. The current shall not exceed 5 mA. This is performed with the equipment running.
4. Insulation Resistance (Class I & II equipment) 500 V dc (for equipment with MOV surge protection or EMI suppression, at 250 V dc) is applied the live supply connectors and exposed metal parts. The resistance shall not be less than 1 MW (equipment with ‘mineral insulated metal sheath heating elements shall be less than 0.01 MW).
5. Flexible cords are tested for earth continuity and insulation resistance, as above. The polarity of the Neutral (blue wire) and Active (brown wire) is checked (pHentron also checks the continuity of the Neutral and Active wires – to AS3199).
6. The standard also specifies tests for portable isolation transformers and RCDs (residual current device).
7. Test results should be kept on the premises where the equipment is used and need to be available if audited on the next working day.
Class I equipment – basic insulated, earthed equipment.
Class II equipment – double insulated equipment (labelled ‘DOUBLE INSULATED’ or )
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The major change introduced in AS3760:2003 is the need to be able to test equipment while it is turned ON and applies to equipment that have electronic switches (ie. touch, membrane or magnetic switches). A multi meter or ‘megger’ testers do not perform the tests required by AS3760. There are also some Portable Appliance Testers on the market that do not meet AS3760:2003 requirements.
Victorian WorkCover
Requires electrical equipment on all work premises (which includes research, testing & teaching laboratories) to be electrically safe, which normally means complying with AS3760 and their inspectors can issue infringement notices for equipment that is not correctly tested.
pHentron
Specialises in servicing scientific instruments and supports a number of instrument supply companies, providing their scientific and engineering requirements.
The principal Peter Henderson has qualifications in both science/chemistry and electronic engineering. Peter has over 17 years repairing scientific and medical instruments, this includes 6 years performing Appliance Safety Testing.
Typical Faults
From our experience, we known that with older instruments (more than 10 years), 1 ® 10 instruments per 100 will fail the safety test, there are several causes;
Ø Insulation ageing.
Ø General failure of an electronic components (eg ageing of capacitors).
Ø Poor maintenance of the instrument.
Ø Poor instrument design, some older instruments do not meet the current AS standards.
Newer instruments tend to have a failure rate of about 1 per 100 tested, often caused by poor assembly technique, such as a dry soldering joint and faults are usually easily rectified.
Old power leads often have faults that are easy to see, common faults include;
Ø Outer sheath is cut, abraded, twisted or damaged to such an extent that the inner cores are visible.
Ø Inner cores are exposed or twisted.
Ø Damaged plugs and exposed inner cores.
Ø Use of insulation tape to repair leads.
Even new power leads (depending upon the supplier) have a failure rate of 1 ® 5 per 100 tested, this is mainly due to poor crimping of the wires to the connectors in the moulded plug. Poor crimping of the earth wire can lead to potential electrocution. Poor crimping of the Neutral or Active wires can cause the plug to get hot and are also a safety hazard – this is not tested in AS3760 but is covered in AS3199.
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Warnings
Ø It is important that computers have a full data back up before performing the safety test. We have occasionally seen computers have a disc crash or power supply fail, during the safety testing – solely due to turning it on and off!!!
Ø There are many firms contracting to do Appliance Safety Testing;
¨ Most are electricians, (some have their apprentice perform the testing) – they do not understand laboratory equipment and we have been called to repair some instruments that have been damaged.
¨ Many use a test instrument that only gives a pass/fail result – although this is currently being accepted by WorkCover, there are discussions that it does not fully meet the requirements of AS3760.
¨ Many contractors do not give a written report, detailing the individual test results for each piece of equipment tested.
New 3 Pin Plugs
The Office of Chief Electrical Inspector (OCEI) (http://www.ocei.vic.gov.au/downloads/plugs.pdf) advises that from 3 April 2005, it is mandatory that all new plug in electrical equipment is supplied
with insulated pin plugs. There is no need to replace the old plugs that are now in use. Photos of the new plugs can be found at http://www.accesscomms.com.au/insulated-pins.htm
pHentron uses the Seaward Supernova XE Portable Appliance Tester. We tag all instruments and power leads, for traceability of test results and you will receive a written report listing all the test results – to fully meet AS3760:2003 & WorkCover requirements.
We are able to repair any equipment that fails the Appliance Safety Test, often when the testing is being performed;
· Saving you down time.
· Minimising repair costs.
· Saving the cost of re-testing.
pHentron is a consultant to several scientific instrument companies and we can help you setup your own in-house Appliance Safety Testing to meet the current and future regulations. We can also perform an audit for you – if you are doing in-house testing or using other contractors.
Please contact me if you require any other information on Appliance Safety Testing, AS3760 or WorkCover requirements. I am also happy to provide a free quote for any of our services, which include performing the Appliance Safety Testing, auditing your system, instrument repairs and preventive maintenance.
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Peter Henderson, Phone: 03 9397 8723
Proprietor, Fax: 03 9397 2732
pHentron, Mobile: 0408 305 325
232 Osborne St, E-mail:
PO Box 712, Williamstown, 3016 Web: www.phentron.com