General Appliance Testers

Overview

At Test and Tag Supplies we class General Appliance Testers as having the following test functions:

• Earth Continuity
• Insulation
• Current Leakage
• Polarity

These functions are what we would class as being the bare minimum specifications. In fact, we don't sell any appliance testers without this functionality.

Appliance Testers in this class may additionally have the ability to perform an RCD/Safety Switch Trip time test and may be battery operated.

However they will not have the following features:

• The ability to record and store resultsPrinting functions
• Programmable PASS/FAIL limits and test sequences
  

Help -> See recording testers for units with this functionality They may additionally have the ability to perform an RCD/Safety Switch Trip time test and may be battery operated.

Values/PASS and FAIL

All appliance testers can provide a PASS or FAIL result following a test. However some can additionally provide the values of each test.

In most organisations and according to most standards and regulation, it is not a requirement to record the values of each test. Providing the test has been carried out to the thresholds specified in the AS/NZS3760:2003, then a PASS or FAIL result is satisfactory.

Indeed many users prefer not to know the values. The key information they want to know is whether the appliance passed the test or not.

Therefore many appliance testers only give PASS/FAIL information. However, values can be useful in some circumstances.

Some users like to know, if an appliance failed a test, how much did it fail by? In some instances a poor earth continuity reading could be improved by moving a probe to a more appropriate part of the appliance. Without values it would be impossible to know how far out of the required result the value was.

The choice as to whether a business should purchase an appliance tester with or without values normally comes down to personal preference or the businesses own policies.A low cost example of an appliance tester with values in addition to the PASS/FAIL result is the Trio LCB. A low cost example of an appliance tester without values is the Seaward PAC3760. They are both excellent low cost choices.

Appliance 'off' warning

The appliance 'off' warning feature (found on many appliance testers) is very valuable - perhaps essential for novice users or nonprofessionals.

This function tests the resistance of the appliance across ACTIVE/NEUTRAL before the appliance test takes place. If the appliance appears to be in the 'off' position based on the results of this test, the appliance tester will not allow the test to proceed.

This is because appliances must be in the 'on' position to test them fully in accordance with the AS/NZS 3760:2003.

Some appliance testers such as the Seaward PAC3760 allow this test to be overridden which can be useful. Others, such as the Trio LCB do not allow the test to be overridden, and a current leakage test must be performed instead.

High Current Earth Bond Testing

During the earth continuity test, (the first electrical integrity test of an earthed appliance or extension lead), a resistance measurement of the earth is made from the pin of the plug, to the chassis of the appliance. This resistance measurement must be below 1 ohm.

When taking this measurement with an insulation and continuity meter, approximately 200mA of current is used (about the amount of current easily generated by several batteries).If earth core in the lead or appliance being tested was almost broken - perhaps holding together by 1 or 2 strands of copper, 200mA of current might pass through the connection and provide a PASS result - providing the level of resistance was below 1 ohm.

Although a PASS result might be achieved, the chances of that connection remaining intact for a reasonable amount of time are very slim.

Therefore, some appliance testers are fitted with higher current earth bond tests.

During a high current earth bond test, a much larger amount of current (10Amps or 25Amps) is applied to the earth. This tests not only the resistance of the connection, but also the physical strength of the connection. The theory is that if the connection was poor (as in the example above - held together by just 1 or 2 strands of copper), the high current applied would actually 'burn out' the connection (like a fuse), and a FAIL result would be achieved.

10 Amp testing is sometimes referred to as Routine Tests, while 25 Amps tests are referred to Earth Bond tests. Like wise 200mA tests are referred to as IT tests.While high current earth bond testing is a good feature it is worth considering the following:

• The AS/NZS3760 does not specify that high current earth bond testing is a specific requirement for appliance testingHigh current earth bond tests may not be suitable for some sensitive electronic equipment Some people believe that in some circumstances, high current earth bond testing can cause more damage than goodSome appliance testers can only test at 200mA, some only at 10A and some older units only at 25A.
• For a complete fusing of a poor connection to be acheived, the earth bond test would need to be carried out for a considerable length of time at a considerable current (eg 5 seconds at 25A).
• More sophisticated and programmable appliance testers can test at a range of test currents for different lenghts of time.

Many low cost appliance testers such as the Trio LCB or Seaward PAC3760 have fixed earth bond currents at 10A. Although this is a relatively high current for testing, it is highly unlikely that any damage would be caused to the equipment under test. In fact we've never heard of a single occurrence.

Many experts believe that the claim that appliance testing (when performed correctly) can damage some types of appliance - senseitive or otherwise, is a complete myth.

Help -> For more information on when high current testing is appropriate see Best Practices Guide to Testing and Tagging

Insulation tests

All reasonable appliance testers can carry out an insulation test. However some have variable insulation voltages of 250V DC or 500V DC. The 'theory' behind a 250V test is that 250V is less likely to cause damage to sensitive IT equipment and should be used if there is a chance that a surge protector (MOV) might cause an incorrect results (which activate at about 275V).

250V insulation tests are useful for testing MOV's for this reason and perhaps appliances with MOV's fitted such as some PC's. However, most good appliance testers have a 'run test' or current leakage test feature which can alternatively be used. See current leakage testing below. It is also highly unlikely that 500V would damage IT equipment for this reason in any event.

Current leakage testing

During a current leakage test 240V AC is applied to the appliance. This test is required if the appliance must be energised to be in the 'on' position. This is a slightly more dangerous test to the user for 2 reasons:240V AC will be used for the test - the currents used for testing will be much higher than that of an insulation test, so if a fault exists with the appliance, there is an increased chance of a dangerous or fatal electric shock.

During current leakage test, the appliance will operate normally. Particular care must be taken when testing appliances with moving parts. Particularly drills, power saws, angle grinder etc.

As a current leakage test powers the appliance in normal operating conditions, it is frequently used for IT equipment and surge protectors. And, to minimize the chances of electrical equipment being damaged by a 500V insulation test.

Help -> For more information on when current leakage testing is appropriate see Best Practices Guide to Testing and Tagging

RCD Testing

Only a handful of appliance testers have integrated RCD trip time testers. Of those with integrated RCD testers, only the Trio SafeTcheck includes an integrated isolation transformer to allow the testing of portable RCD's.

It is often cheaper to purchase a separate RCD trip time tester than it is to choose an appliance tester with an integrated RCD tester.

Help -> For more information on RCD testing see RCD testers

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