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AMD 2 - high protective conductor currents
2013 Posts
It looks like the DPC is suggesting a number of changes to section 543.7 - the bit about having to deal with protective conductor currents between 3.5mA and 10mA seems to have gone, likewise 543.7.1.202 (ii) (b) which allowed small c.p.c.s in flexes provided there were no smaller than that of the line conductor.

The bit I found most surprising though was the deletion of 543.7.1.204 - which required duplicate c.p.c.s to be terminated independently of each other - as I always thought that a very sensible requirement as terminations seem to be the source of the majority of problems and there seemed little point to me in having duplicate c.p.c.s if they can both be disabled by the same loose connection. Does anyone have any insight into why such a change is being proposed?

   - Andy.
3 Replies
352 Posts
Follow the money..............
1256 Posts
I guess it depends whether you were of the opinion that the original requirements were OTT for the most part, or rendered unnecessary.

Considering Regulation 411.3.3 (or 522.6.203) combined with 531.3.2 (ii), we're probably talking about very few circuits these days where two independent protective conductors are required - probably in the specialist arena, and many where other provisions to achieve the requirements (such as earthing to BS EN 50310).

Personally, I worry that the requirements for RCDs, and the protective conductor currents permitted by product standards, are not necessarily aligned. However, the evidence from years of using split-load CUs, is that perhaps I'm worrying unnecessarily for the most part - and of course use of RCBO's improves on that situation.
172 Posts
I suppose it is accepting that currents between 3.5 mA and 10mA are becoming the norm and that strengthening of the RCD requirement for all socket outlets up to 32A puts an upper limit on the amount of current permissible before tripping occurs.
The deletion of 543.7.1.204 could be viewed as being driven by manufacturers not wanting to put an extra terminal on their accessories. But connecting the two protective conductor circuits could be done using a couple of connectors in the enclosure and a couple of flyleads to the faceplate earth terminal, getting rid of the 1 point of failure for both circuits.


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