Regulation stating a type AC RCD can not be upstream from a type A RCD

So now a pump manufacturer has DC? leakage of 3.5mA or less but wants a type A? Please explain why that might be.

Because modern A-rated pumps are full of power electronics?

   - Andy.

Being full of electronics is not the reason for leakage is it? That is a get out of jail excuse with zero merit!

But just what is a DC COMPONENT? Is it a D.C. electronic component like a diode or transistor? Or is it a type of electrical current? AND does the regulation apply to a normal D.C. component if of an electrical type. OR just if one can appear under fault conditions?

Also, how do we measure the DC component if of an electrical supply type to see if it exists?

Z.

That's exactly it. The new electronic blinding appliances are dangerous. Then we have to be careful with the use of appliances and D.I.Y. work at home. If we can't rely upon R.C.D.s to be totally bombproof and effective under all reasonable conditions of use times are bad..  And run all cables in earthed steel conduit.

So show me one of these, i haven't seen one.

If the Wiring Regulations had required Type A RCDs or at least recommended them for as long as the rest of Europe has been installing them we would not have such a big issue with appliance manufacturers making appliances that require Type A RCDs.

Now we are in the situation where we need appliances specifically manufactured to allow them to be used within UK or millions of homes need their electrical installations upgraded.

The simple answer is that millions of homes really do need their electrical installations upgraded, but in the meantime people are going to end up having issues with RCDs that aren’t fit for purpose, on top of all the other issues.

It will be interesting to see if any social housing landlords decide they need to go through all their properties and replace any Type AC RCDs with Type A, that will keep their electricians busy.

And yes, I have seen 30 mA RCDs being blocked with a higher rated upfront RCD, the the downstream RCD failing to when tested.

One of what?

Z.

I am now going to reply to Andy J. The design of modern SMPS does not have a rectifier into a smoothing capacitor because the "rules" say they must achieve virtually perfect power factor.

But lots of devices don't have fully fledged SMPs - in the example I gave (LED lighting) it's usually far simpler and I've seen PF of 0.5 or below with some.

Being full of electronics is not the reason for leakage is it? That is a get out of jail excuse with zero merit!

I'm not sure I'm following your line of thought - I thought the type A requirement was to endure it tripped with a non-sinusoidal fault current (e.g. after the power electronics) - either on TT systems or on TN systems where there's significant impedance before the fault - e.g. a short to case part way along a winding - to avoid either an immediately dangerous situation (TT) or a persistent condition that may mean loss of all additional protection (TN).

I guess there will be some leakage - power electronics usually require a bit of filtering on the mains side - but I'm not seeing the connection...

   - Andy.

I could use an equally good argument, that the fact that single-phase LV supplies in the UK are "polarized", having a neutral conductor, rather than being "centre-tapped to Earth" as in a split-phase single-phase supply, exacerbates the situation for electronics designers.

This is because we have a "system" that includes the source of supply, the installation, and the connected product, and decisions made at any point in that "system" may well affect the design of other parts of the "system".

It's all very well arguing the technicalities, but that horse has bolted and the stable door is also well and truly bolted as well, so we are left in the position of having to comply with the new Wiring Regulations.