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Posted By Topic: Double insulated tools/appliances

Jun 29 2018 20:59

Is there any point in using an RCD on double insulated power tools? Even if the phase wire came loose wouldn\'t a person holding it still be fully isolated from earth by the insulation of the casing meaning there would be no earth leakage to trip the RCD? Thanks

Jun 29 2018 21:34

All the job sites I have seen (more industrial) use some sort of Lifeguard RCD Power Outlets were the guys/girls will plug their power tools into.

The number the power tool leads (e.g. grinders are a classic) and ext leads that I have repaired because they have exposed live conductors would be in the hundreds. The welders burn thru the insulation, the grinder cut thru their power cord, someone runs over the ext lead, etc.

There are a lot of sites where you are outdoor and the power tools are exposed to water and there goes your double insulation.

RCD all the way!


Jun 29 2018 21:48

RCD just needs Active current to be out of balance with current flow in Neutral to trip, some DI tools coming out with a device (not certain RCD is the correct description)but the leads for these things are two core, have a trip button,if we could upload pictures of a worthwhile size I\'d post a pic

Jun 29 2018 23:10

If your using that appliance on a construction site then AS/NZS 3012 2.4.6 requires that all appliances are connected from an RCD protected supply. AS/NZS 3012 is referenced specifically as to comply with by AS/NZS 3000
If that appliance is at home or elsewhere then I’m sure you will appreciate the extra protection of a RCD when you come in contact with a phase wire on a worn out/damaged flex. Remembering that domestic plug sockets on new houses will also be RCD protected

Jun 30 2018 09:19

Yes because as others have pointed out most of the risk comes from users damaging the appliance lead while using it. The protection afforded by an RCD protected power point or portable RCD extends from the point of connection so will protect the user from anything that might cause a current imbalance between phase and earth. This could include a breakdown of components or insulation anywhere in the protected circuit.

The use of RCD protection is mandated in some areas and recommended in most others where there is a risk of electric shock.

Jun 30 2018 09:27

jave aread of ESR 2019 regulation 89 where the use of an RCD is mandated. It is law of the land which overrules any standard.

Jul 02 2018 16:47

Methinks Pluto is reading more into that Reg than is actually there.
RCD is just one of several acceptable options, for each of the two scenarios covered; and note that for building sites one of the other options is double insulated tools.

Jul 03 2018 23:56

Nope. AS/NZS3012 section 2.4.6 pretty much says if you want to plug in an appliance on a construction site it must be protected by a 30mA RCD exempts items like cranes, lifts SELV, PELV or a directly connected isolating transformer. allows an isolated inverter supply, no RCD. Otherwise plug the appliance in from a RCD protected outlet

Jul 05 2018 10:11

True, but don\'t forget that \"3012\" is not mandated by ESRs; just cited as an acceptable means of compliance (ESR 25 from memory)

Jul 05 2018 19:46

And there is nothing in Reg 89 that refers to construction and demolition sites.

The point is that for most users of appliances there is no mandated requirement for an RCD protected supply.

Most modern domestic installations provide the RCD by default.
Some commercial installations provide RCD protection due to the situation requiring one.
Other commercial and industrial installations have RCD protection as a risk management device.

There is an obvious safety benefit in using RCD protection for all appliances especially outdoors.


Jul 05 2018 22:48

So ESR 59(2) says you comply with 3000
And 3000 says comply with 3012
And 3012 says use a RCD

And ESR 89(2) says a hand-held appliance in “...a building or structure under construction, the appliance must be -...“ options (a) to (g) where (e) is use RCD

So RCD is compliant with both 59 and 89 for a building site

Jul 06 2018 08:01

ESR 59 says must comply with 3000 when installing, testing and inspecting. Nothing about operating and using.

Also worth noting ESR 60 does not pick up on AS/NZS 3012.

Jul 06 2018 19:37

Interesting that the only place where compliance with the requirements of 3012 is required is in Reg 78M Tourist mining.

As Aleck has pointed out 3012 like 3760 is offered up as a means to meet the “deemed to be safe“ if you follow them standards.

Reg 89 is for specific high risk situations (says it in the title) and does not mandate a requirement for RCD’s everywhere.


Jul 07 2018 16:22

Maybe the regs say double insulation is safe without other protection, but IMO I never trusted it for hand tools.
It can be okay when new but with a build-up of dust inside or a bit of moisture there is a conductive track right through the vent holes.
Also many shocks occur from damaged flex cables which would have been protected by an RCD or transformer.

Jul 07 2018 19:57

This was the original question:
“Is there any point in using an RCD on double insulated power tools?”

Most of the answers have been YES.

A few people have attempted to say it is mandatory and even offered their version of a reference.

The use of an RCD is optional except in a few specific circumstances.

My personal opinion is that the use of an RCD protected supply for most power tools especially in the workplace is a sensible thing to do.

I believe that there will be an increased requirement to provide RCD protection in the new version of AS/NZS3000 whenever it becomes referenced in the ESR’s.

Jul 09 2018 23:11

OwenK raises the issue of \"secondary citation\"; where a Standard not mandated by ESRs is indirectly mandated by \"3000\". \"3012\" is just one example of this.
I suspect that if a case came before the courts, secondary citation could be enforceable if there was no other obvious interpretation. But where ESRs make a clear distinction between some Standards being mandatory, and others deemed-to-comply; a secondary citation would not survive.

That said, I agree with Sarmajor; using RCDs as well as DI is a good idea, regardless of whether or not we have to.