electricalforum.nz

Do the rules around rcds in 3000 apply to transportable structures?

From the info in 3001 specific to rcds all I see mentioned is "sufficient" number of rcds used.

Not sure if that Overalls 3000 though

It does show in another diagram 3000 and additional rules of 3001.

Not if that part is additional of backing up 3000?

As per clause 1.2, rules of "3000" apply unless specifically modified by "3001".
Which particular RCD rule are you thinking of?

Arrangements of rcds

not more than three final subcircuits shall be protected by any
one RCD

It does say for residential though.?

Yes, clause 2.6.2.4 applies; because nothing in "3001" modifies any part of it.

So you have to apply (a); and distribute lighting over more than one subcircuit - IF there is more than one subcircuit
As you've note, (b) - the 3 subcircuit rule - only applies to "residential installations".
In 2018 edition; there's a definition for "residential electrical installation" ; but in (currently cited) 2007 there's just the explanation in the Note to 2.6.3.1
Based on the Note, some would argue that a caravan is "residential" because people live in it.
However while a caravan may be used for residential type purposes; there are two parts to the term, the other part being "electrical installation" And under NZ law it isn't any kind of "electrical installation"; it's a "connecatable installation" - which has a very different definition.
Remember the definitions in the Act and ESRs over-ride those in "3000" and companion Standards.
This could get very complicated working through the complexity of definitions.
But in practice the chances of actually having more than 3 subcircuits in a caravan / motorhome are minimal.

In practice a modern caravan / motorhome typically only has one final subcircuit.
There's no point having more, as there's only a 16 A supply available.
True you could build one with 20 A or 32 A supply lead & fittings, but caravan parks only have 16 A sockets.
So for those few units that need more than 16A; they are set up as 2 separate connectable installations within the same structure.
2nd point is that these days lighting is almost exclusively ELV, not powered from mains at all;
and even if not, you have to run cable with minimum 7 strands - which is generally 1.5 mm2 flex, or 2.5 mm2 TPS.

You have to limit total current; you have to provide overcurrent protection for the wiring, and you have to provide RCD protection.
There are several ways of meeting these requirements; but the simplest is a single 16 A RCBO, which does all three.
The RCBO also acts as a whole-of-installation isolating device; although currently there's no requirement for one.

With only one overcurrent device, there's only one subcircuit. And as long as all the cabling is good for 16A; it avoid a lot of pointless complication & expense.

Good to know.

So just to clarify as its a Connectable installation those rcd arrangement rules do not apply?

Not that they can't apply.
Just that in practice they seldom do; because caravans / motorhomes generally only have one subcircuit.

Other types of connectable installation (eg mobile shop / kitchen) may have more than one subcircuit, but are non-domestic.

If a caravan / motorhome ever did have more than 3 subcircuits; we'd have to have the discussion about whether or not they are a "residential installation". They are certainly used for a residential purposes; so it would come down whether they fit within the definition of "electrical installation" in the Electricity Act. But while that could be interesting for a few of us; it has little or no practical effect; so why bother?

Good point.

So why we are on the subject would I be correct in saying that for an EWOF rcd arrangement is not something that is a concern for appendix C or even part 1 if it were an import?

But not to get rcd arrangement confused with rcd type as rcd type is something that will need to be checked.

Correct; For a WoEF, only those matters covered in Part 1 or in AppC are relevant.
So the precise arrangement of any RCD protection that's present isn't a WoEF matter.

Thanks mate much appreciated