RCD testing for commercial and industrial sites in NSW

Most commercial switchboards have safety switches in them, and almost nobody looks at those devices again once the board is energised. An RCD is a mechanical thing – a sensing coil, a tripping solenoid and a set of contacts – and like any mechanical thing it can seize, drift out of specification or fail without any sign from the front of the board. A device that no longer trips looks exactly like one that does.

RCD testing is a small line on a maintenance schedule and an easy one to get wrong, partly because two quite different tests share a name, and partly because the NSW rules say less about frequency than people expect. Here is what the regulator asks of a commercial or industrial site, and what should end up on file.

What the device is protecting

An RCD compares the current flowing out on the active with the current returning on the neutral. If some of it is going somewhere else – through a person, through damp insulation, through a frame that should not be live – it opens the circuit before the leakage lasts long enough to stop a heart. That is a different job from a circuit breaker’s, which is why a board full of breakers is not by itself evidence of shock protection.

The SafeWork NSW code of practice on managing electrical risks puts numbers on it. Where an RCD is required for equipment supplied through a socket outlet not exceeding 20 amps, it must have a tripping current no greater than 30 milliamps. The code also draws two device classes from AS/NZS 3190: Type I, up to 10 milliamps and tripping within 30 milliseconds, for equipment connected directly to a person; and Type II, up to 30 milliamps and tripping within 300 milliseconds, which it calls the most suitable choice for personal protection against electric shock.

Where RCD protection is required

The work health and safety duty is narrower than people assume. SafeWork NSW states that RCD requirements apply in relation to workplaces, and attach to plug-in equipment used in harsher conditions rather than to every outlet. The conditions it lists are:

• Equipment exposed to moisture, heat, vibration, mechanical damage, corrosive chemicals or dust.
• Equipment moved between locations in ways that make damage reasonably likely.
• Equipment frequently moved during its normal use, or moved while it is running.
• Equipment that forms part of an amusement device.

There are exceptions, including supply at 50 volts a.c. or less and supply through an isolating transformer giving at least equivalent protection. The regulator also notes that the wiring rules and other electrical safety laws may impose RCD requirements of their own, and that is the part worth holding on to: a warehouse or logistics facility wired to current rules usually carries far more RCD protection than the workplace duty alone would call for, and all of it needs to keep working.

Two tests, one name

The first is the push-button test. Pressing the trip test button operates the device’s own mechanism and confirms it opens and resets; the code describes doing exactly this on a new portable RCD to confirm it is effective. It needs no instrument and a site can run it as a routine task. What it does not tell you is how quickly the device tripped, and that is the number deciding whether the protection is still inside specification.

The second is the instrument test. A tester injects a measured residual current and records the time the device takes to open, read against the limits above. This is the test that produces a result worth keeping, and on a live commercial board it is electrical work. It is also the one most often missing from a compliance file that otherwise looks complete.

How often is “regularly”

The duty under the NSW work health and safety laws sits with the person with management or control of the workplace: take all reasonable steps to ensure the RCDs used at the workplace are tested regularly by a competent person. It covers all operating environments, fixed devices included, and a faulty device must be taken out of service and replaced as soon as possible. What the regulation does not give you is a single interval.

The code points to AS/NZS 3760 for indicative inspection and testing intervals, and sets out intervals for electrical equipment in particular settings: at least every twelve months in higher-risk environments, at least every six months for manufacturing and workshop equipment and for commercial cleaning equipment, and at least every three months for hire equipment, which should also be inspected at the start of each hire. Those are equipment intervals rather than RCD-specific ones, but they are a defensible starting point, and in practice RCD work lands on the same visit as the test and tag round, whose intervals we cover separately.

Who counts as a competent person

The code treats a competent person as someone licensed or registered to perform electrical work. It may also include someone who has completed a structured training course in visual inspection and the use of a pass-fail portable appliance tester, which covers portable equipment well enough. For the fixed devices in a commercial main switchboard it does not, because getting at them is electrical work on an operating installation.

The records that matter

A record of testing, other than push-button testing, must be kept until the device is next tested or disposed of. Treat that as the floor, not the target. The code’s record requirements for electrical equipment are a good shape to follow:

• The name of the person who carried out the testing.
• The date of the test.
• The outcome.
• The date the next test is due.

Tags should be durable, water resistant, non-metallic and incapable of re-use, and the code is clear that a logbook, database or register is the permanent backup for when tags go missing. Measured trip times held against a device schedule are the only way to notice one slowing down across visits.

Fixed RCDs are the ones that get missed

Portable RCDs and leads are usually in reasonable order, because the test and tag round picks them up and someone owns the equipment register. Board-mounted devices belong to the building rather than to any equipment list, so they fall between the facility manager, the tenant’s contractor and whoever holds the electrical maintenance – not deliberately skipped, just absent from every register. Two findings come up often enough to be worth checking for on an older board. The first is a single device upstream of a large number of circuits, so a fault anywhere drops far more of the site than it should and the temptation to leave that RCD untested is strong. The second is a board with no RCD protection on circuits that would attract it under current wiring rules. Both point to switchboard upgrades rather than to testing around the problem.

Building it into the site routine

RCD testing is not worth a visit of its own. It belongs with the other recurring electrical checks, which is how it ends up inside a maintenance contract with a named device schedule and an agreed report format. That schedule is usually the difference between a compliance file that holds up and one reconstructed the week an auditor asks.

Next steps

If you cannot tell from your records when the fixed RCDs in your boards were last tested, or whether they were tested with an instrument at all, that is the place to start. Our office hours are Monday to Friday, 7am to 5:30pm, and we offer after-hours call-outs for commercial and industrial sites. Call Eclipse on (02) 9832 9871 or send us your site details and we will work through what your boards hold and what schedule they need.

General information only. Requirements change and depend on your site, so confirm specifics with your certifier or insurer, or ask us.