Solar Inverter RCD protection

[JamieP]

I recently made a post elsewhere that touched on this but thought this deserved a dedicated thread

4777.1:2016 allows such an arrangement and is common is Australia

But although looking to a more up to date standard is a good idea, you have to make sure you don't contradict any of the requirements of the version cited in Regulations as this is law

In NZ, 4777.1:2005 is the cited version

Does 5.3.4 of this standard prevent RCD protection on the inverter supply where it connects to the switchboard?

[AlecK]

I do not believe that there is any actual conflict between these clauses.

[JamieP]

Alec, I know you probably don't want to explain yourself twice but would you mind going a little more in depth into your reasoning, incase the response elsewhere isn't seen

Or shall I copy and paste the original here?

[TPower]

Why are they describing installing RCD protection as providing ‘mech protection’ in 4777.1:2016?

I’m guessing they’re referring to instances where cables are installed within 50mm of wall, ceiling or roof linings as described in 3000:3.9.4.2 & 3.9.4.3.2.

My understanding is it’s a protection method as per 3000:3.9.4.4(c).

Referring to it as mech protection doesn’t seem quite correct, and could be misleading for some. That’s if I’m understanding this correctly?

I’ve never actually seen an RCD fitted for an inverter AC output.

[JamieP]

You are correct, it's common over in Australia in those scenarios

But my question was in regards to 5.3.4 of 4777.1 2005 and the meaning behind this clause, whether it was permitted to have RCD protection on the supply to the inverter

[AlecK]

That's exactly what they're referring to.
And I agree, an RCD does not really protect cable against mechanical damage
However, "3000" does permit it as a means of such protection (in those circumstances listed in 3.9.4.2 or 3.9.4.3.2);
despite the fact that it doesn't prevent damage from happening to the wiring system, it really only protects people against (some) consequences of the damage.

Note that RCD is only acceptable in those limited circumstances; not anywhere else. For example; it doesn't count as protection where cables are draped across ceiling joists and might be damaged by people walking / crawling over them.

This set of clauses has been flagged for being clarified in next edition; as lots of readers get confused
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agree it's better here under a relevant heading than the other thread.
I'll go over the implied conflict, and why i don't think there's any real conflict; when i have more time.