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Posted By Topic: Trailer House (Tiny House)

Mar 05 2019 15:35

Hi Gents, hope someone can shed some light on this.
I have just completed a new install for a friend on a trailer house or tiny house as they are calling them these days.
Im not sure what category this comes under probably a Caravan or mobile home.
Not sure what mandatory tests i am supposed to complete considering its on a caravan plug and lead. It consists of lights sockets and switch board, RCD, 10 & 6A MCB's (do I really need a main switch) cant the RCD act as the main switch? Any help would be appreciated!

Mar 06 2019 08:04

If the supply is connected by a plug and socket outlet arrangement, can use Warrant of Electrical Fitness every four years use AS/NZS 3001:2008 in conjubction with AS/NZS 3000:2007.

ESR 2010 regulations 76 to 78.

The socket oulet providing the supply is covered by AS/NZS 3000, but remember the additional requirement of AS/NZS 3001 section 2; the socket outlet should be protected by an MCB with a rating not exceeding the rating of the socket outlet it is supplying.

Mar 06 2019 09:05

The requirements for initial verification are in clause 3.10 of "3001. You should already have this, as you should have been working to it[ESR 60}. And if you haven't - and being unsure what rules apply at this end of the project suggests you haven't; chances are what you've assembled won't comply.

The verification required is as per section 8 of "3000" and the additional requirements of "3001"

That's way more than a simple WoEF test as per App C; which is a simplified system for ongoing in-service checks. The WoEF checks are based on the assumption that the connectable installation fully complied when first created.

And while ESR 78(1)(c) says you may issue the first WoEF; you first have to issue a CoC, which will have to cite both "3000" & "3001" (as per ESR 67).

Yes the RCD can act as the "main switch"; because all rail-mount RCDs approved for sale in NZ are isolating switches. In fact those who understand how the requirements work tend to use ONLY a 16 A RCBO; because if you set things up the right way that's all you need.
Too late now.
Can I suggest the best time to seek advice is before starting a project?


Mar 06 2019 10:28

Another point - You've managed to comply with overload protection of the incoming supply if you actually do have 1x10A and 1x6A MCBs (=16A) - but possibly that was by accident rather than design?

As you used the 6A MCB, what cable did you use on those circuits? Hope it wasn't 1mm2 TPS, as the minimum requirement is 7 strand, or flex.

As Alec said, most builds will only have one 16A RCBO as the main switch and RCD, which covers all the requirements.

And just to add, if you decide to get a WoEF at this point, the person doing the WoEF checks doesn't need to sight any COCs.

Mar 06 2019 16:14

True, but if it's me that;s asked to do a first WoEF for a new-build, I'm going to want to sight a CoC. I can't demand one as of right- but if I don't get one I won't be issuing the WoEF. it's my name & number on the WoEF, so it's me that'll get the blame if something goes wrong. I've seen too many that simply didn't comply, because the guys wiring them didn't bother to find out what the requirements were.

Mar 06 2019 18:04

I was recently asked to issue a WOEF for two caravans the had been imported from the good old USA.
They had done exactly zero research before spending a shit ton of money.

Weren’t happy about the prospect of scrapping all the appliances and wiring and starting again.

Mar 06 2019 18:30

So you telling me I have to change the 1.0 mmtps to seven strand cable? Reason being?

Mar 06 2019 21:41

Well let’s start with Reg 60 which says that your installation must comply with AS/NZS3000:2007 and then section (e) of Reg 60 which says that connectable installations ie; plug in tiny houses, are required to comply with AS/NZS3001.

So most everything that you have to get correct in a normal house applies.

And then you move into 3001 section 3.4 which directly addresses the wiring types allowed in your connectable installation.


Mar 06 2019 22:42

Note also that, as you have >1 final subcircuit, 3000 requires that you have minimum two RCDs. RCBOs and an MCB as main switch is likely to be the better choice.

And yes, seven strands is in 3001. 3.4.1.


Mar 07 2019 00:20

Someone - the more than one final subcircuit requiring more than one RCD only applies in residential installations.

Mar 07 2019 08:27

You need to read AS/NZS 3000:2007 + A1 +A2 clause (a) to get the correct context of the stetment being made.

Mar 07 2019 09:09 is not relevant; as there is only one RCD and only one lighting circuit; so neither condition is met and (a) does not apply.
And sarmajor is correct; (b) is limited to residential. However most caravans / motorhomes / tiny houses are residential; including under new definition 1.4.55 of 2018 edition.

So in OP's config, 1 x RCD + 2 x mcbs is 2 final subcircuits, so yes (b) says should have 2 x RCD. But only if it is a "residential installation"; and while it's residential in nature, it is not an installation (as defined). Among other factors, it plugs in.

Regardless; fitting a 16 A RCBO means only 1 final subcircuit, with all bases covered: fault protection, RCD protection, overcurrent protection, and an isolating switch.

And yes, that 1.0 mm2 will have to go. It was accepted years ago, in 1960s & 1970s;and those old units can still pass a WoEF (because Govt doesn't like being seen as forcing people to upgrade). But hasn't been allowed in new-build for a long time (2001 I think). The reason is simple; resilience to vibration etc for mobile equipment. In some states of Oz, single-strand 1.0 mm2 isn't accepted for PECs even on fixed installations. Most CIs today are wired using TPS flex.


Mar 07 2019 09:56

AlecK - I really appreciate your input on these matters explained really well.
Though I have a question just to finish off before I go and pull in new flex cable. I was reading the 3001:2008 section 3.2.1 and have noticed that for a movable unit that is now immobile that it comes under 3000 not 3001 if the supply is permanently wired/fixed? So then the 1mmTPS is ok?

Mar 07 2019 16:06

pretty much.
A "connectable installation" has to comply with both "3000" & "3001".
A key part of the definition o0f 'connectable installation" (in the Act) is that it is plugged in.
So if the unit is rendered immobil, and the supply is hard wired, then only has to comply with "3000" and doesn't need a WoEF.

Mar 09 2019 00:17

>"...But only if it is a "residential installation"; and while it's residential in nature, it is not an installation (as defined). Among other factors, it plugs in."

Where does that come from? The definition of 'connectable installation' in the Act says it is "an electrical installation of that vehicle (etc.)"

The definition of 'electrical installation' in the act seems to likely include it - it either has a point of supply or doesn't and is covered either way, it is not an appliance, and there's nothing to do with generation/transmission/transformation.

Having a plug might vary whether it is a connectable installation, but whether it is a connectable installation or not it is surely still an electrical installation?

Mar 09 2019 12:21

Yes there are two parts to definition of "electrical installation".
The second part, where there is no "point of supply" was added in order to include off-grid standalone installations.

But in both cases the definition refers to "a property", and a connectable installation isn't tied to any property; so doesn't conform to the definition, so cannot be an "electrical installation".
Just as well, 'cos if it was one, it would have to have MEN, earth electrode, etc.

A heart it's a collection of fittings.
So's an installation, and so's works.

I believe part of the problem is use of the term 'electrical installation' within the definition of "connectable installation"; which creates confusion