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NAPIT code breakers recommends a C3 for no RCD protecting socket circuits for internal use and a C2 for type Ac RCD that may be blocked.

Alan B

I can see that the no RCD could be justified because it complied with previous regulations, same could be said for a type AC RCD.
The type AC RCD is recommended C2 for supplying PV, EVCP's, SMPS, domestic appliances with VSD's.

I would take supplying PV and EVCP's as an automatic C2, no discussion and most agree.

But then also includes circuits supplying SMPS and appliances with VSD's, given that almost all domestic electrical equipment, other than most lights are likely to have a SMPS it's implying that for nearly all domestic installs a type Ac RCD is a CD, but no RCD is a C3.

In my opinion this just looks like an oversight that's causing confusion and no RCD should also now be a C2 for domestic installations, it's how I now code them. I take codebreakers to mainly be aimed at domestic installations.

There are of course a few exceptions like submains surface clipped where a 30mA RCD is not required.

I know this has been discussed a number of times in different forums, just wondering what opinions are in this group. If you feel the current position in code breakers is correct, what's the justification.

Is there anything published by IET, NAPIT or NICEIC that clarifies this

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  • It all seems rather inconsistent.

    Alan B said:
    no RCD should also now be a C2 for domestic installations, it's how I now code them.

    I have lived here for 29 years without RCD protection indoors (but shed-loads of supplementary bonding), so that seems a bit harsh. It also forces the hand of a landlord.

    If no RCD = C3, but an RCD which may not work with PV, EVCP, heat pump = C2, that is inconsistent.

    Surely, the risk which RCDs mitigate is a damaged appliance. Something which is plugged in (especially if it is used outdoors) seems to be more likely to fail than a hard-wired appliance.

    If a PV system, EVCP, or heat pump may "blind" a type AC RCD, there is a better argument for C2. However, I have no statistics to hand. Does anybody else?

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  • It all seems rather inconsistent.

    Alan B said:
    no RCD should also now be a C2 for domestic installations, it's how I now code them.

    I have lived here for 29 years without RCD protection indoors (but shed-loads of supplementary bonding), so that seems a bit harsh. It also forces the hand of a landlord.

    If no RCD = C3, but an RCD which may not work with PV, EVCP, heat pump = C2, that is inconsistent.

    Surely, the risk which RCDs mitigate is a damaged appliance. Something which is plugged in (especially if it is used outdoors) seems to be more likely to fail than a hard-wired appliance.

    If a PV system, EVCP, or heat pump may "blind" a type AC RCD, there is a better argument for C2. However, I have no statistics to hand. Does anybody else?

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