If you’ve got and Advanced Appliance Tester like the new Metrel Alpha PAT, 3309 or the Seaward Primetest Elite you might have seen a test called Substitute Leakage test. So what is this substitute test and when would you use it? Well in Australia it’s unlikely you will use it at all – here’s an explanation.
The Substitute Leakage Test applies a low voltage (typically around 40V AC) to the appliance and measures the actual leakage current, then scales the result to estimate what it would be at 230V AC. It allows for a leakage measurement without powering up the appliance, and is used in some countries where live testing may not be practical or safe in certain environments.
But in Australia, the AS/NZS 3760 standard doesn’t call for Substitute Leakage testing. We generally test appliances under actual operating conditions using the standard leakage or insulation resistance tests. Substitute leakage isn’t considered a compliant method here, because it doesn’t give a true indication of how the appliance behaves when it’s actually turned on. So, while it’s a feature that might pop up on your tester from time to time – in most Aussie workplaces, you’ll be skipping it. If you're unsure what test is required for a particular appliance, stick to what's outlined in AS/NZS 3760, and you'll be on the right track.
