I have just had a visit from Ken Matherson at Legrand ® (Perth W.A) who wanted to show me a new product on the market that can automatically reset an RCD safety switch . Legrand, a big player in the electrical field is a French owned company that recently brought the Australian electrical manufacturer HPM.

This new Legrand product is referred to as the Stop and Go Automatic Resetting Device for MCB, RCD and RCBO’s.  Cat number 07381 and 07382, the later having the ability to test an RCD Safety Switch every 56 days. The design has a selling point of reducing unwanted ‘nuisance tripping’ and as I understand it,  is designed to reset any 35mm din rail mounted circuit breaker or safety switch in a 2 pole module format. The RCD reset device itself occupies a space of 3 poles.  It therefore has some restrictions and would be applied best in  a pre design format or require a switchboard upgrade. To simply retro fit in many cases would not be practical as any electrician would know.

The 07381/2  really opens up a can of worms that’s for sure. The first thing that comes to mind is that it might be very useful for preventing the defrosting of valuable foods. The brochure points out that the product also has values in areas such as preventing power loss to swimming pools, alarm systems, watering and heating. The list could just go on and on when you think about it.

We all know what a hassle it is when you get to work or come home and find your power has been off all weekend or for that matter all week. So wouldn’t it be nice to have that little device automatically turn the power back on when your RCD has tripped and you weren’t around to notice it. But there lies the  devil. An automatic reset device could go about it’s business for ages whilst the potentially lethal  earth leakage fault remains unattended.

Some  actual examples of RCD tripping are;  the swimming pool remains live when the submerged pool light is turned on (it’s 24 volt transformer has shorted onto the 240 volt side) ; The bare electrical conductor from the garden pond pump remains bare and tripping the RCD every time it gets wet from rain or watering ; The pool pump is ‘down to earth’  on any given damp day;  The fridge which occasionally goes ‘down to earth’ during defrost cycle, etc, etc.  Now picture these faults going unattended simply because you don’t have the hassle of manually resetting the RCD.  It’s going to happen.

I can list numerous examples that I’ve come across from years of attending to RCD faults and the ones mentioned above are real incidents.  But would those faults be corrected in a timely manner with an automatic reset device?  Probably not.  That is to say the potential death trap remains in situ  as the automatic RCD reset device goes about it’s business.

It will be interesting to see how well accepted (and applied) these devices  become in the industry.  There would be an initial response to consider this product to be unsafe as once an RCD has tripped it might not be wise for it to be reset automatically as I’ve mentioned. On the other hand it could prevent a mishap costing  thousands of dollars and could be something the insurance industry might factor in.  But first the 07381 would have to cotton on and for what it’s worth, the nuisance of an RCD constantly tripping calls for concern,  not  convenience.

~ Rob Middleton     5th April 2011


 Safety Switches Western Australia