Feeding transportable installations from each other

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Feeding transportable installations from each other

Post by JamieP »

"I have a relative with two old caravans at a private camping ground with one caravan socket. One caravan is her living area and the other is the bedroom. Can I put a caravan socket on one caravan so she can plug in the other caravan? I would change the switchboards in both caravans over to RCBO 16A upgrade etc at the same time."

This post was made by another elsewhere and I have been looking into it but can't really decide what my view is so curious to hear what those on here have to say

I came across 3.4.3 (EDIT: MEANT TO SAY 4.3.4) of 3001 but seemed to be located in an odd location under "ELECTRICAL INSTALLATIONS IN TENTS AND NON-RIGID ANNEXES"
Last edited by JamieP on Thu Jan 06, 2022 11:53 am, edited 1 time in total.
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Re: Feeding transportable installations from each other

Post by AlecK »

Short answer:
connectable installations can be cascaded (one fed from another), but needs care.
And seldom worthwhile; as the available current is limited by the first one in the string.

If there's provision for only one connectable installation, then it isn't a "caravan park" under definition in ESR 4.
However ESR 60 still requires compliance with "3001".
That leads to clause 2.3 for locations other than caravan parks; so (slightly) different requirements apply than under 2.2 for caravan parks.
But in both cases the options for socket types are limited, the socket must have individual overcurrent protection,individual contrpl switch, and must be RCD-protected; plus provision for strain relief.

If wanting to connect more than a single connectable installations, the preferred method is to install another socket in the installation
- which then makes it a "caravan park" and moves back to clause 2.2.

If wanting to set up a cascade; first task is to establish exactly what requirements apply.
The socket is intended to supply a connectable installation, so at first glance ESR 60 (1)(f)(iv) appears to require compliance with 3001.
However because it isn't part of a "site installation", that's the wrong reference. The socket is part of a connectable installation, so the correct reference is (e) instead of (f). As a result, the applicable requirements are in Section 3 of "3001", and not Section 2.

That said; I would advise complying with both Sections in order to avoid the inconvenience of someone complaining to EWRB.
What they would make of it is anyone's guess.

Consider each requirement separately; before thinking about combining multiple functions in one device.
Just going with the usual 16 A RCBO to provide multiple functions may not be the best approach.
A key aspect of control & protection is current limitation of the incoming supply; and that has to control / protect everything in the CI.
This means the won't actually be 16 A available for the (external) socket for supply to the 2nd CI; there will be only 16A total.
You'll end up with (at least) 3 x 16 A overcurrent devices in series (the fixed socket, the current limiter for CI #1, and the current limiter for CI #2)
so there can be no discrimination.

I understand that site huts are being cascaded on some building sites, but the (limited) info suggests that these are not correctly set up.
They've set up the outgoing supply to hut 2 by simply looping from the Hut 1 inlet, or from the line side of the Hut 1 RCBO.
Which is non-compliant on several levels; and can't pass WoEF.

An argument could be made that the supply to the cascade socket should be considered as a submain, rather than as a final subcircuit.
This would be equivalent to using ACS system on a construction site. However for ACS there's a clear statement in "3012" that the backbone of an ACS system is deemed to be a submain.
I've also seen cascading done for trains; with each carriage plugged into the one ahead / behind (generator generally in the middle), and the swbd for each individual carriage tapped off the "backbone" supply. However trains are specifically excluded from ESRs [ESR 3].
Since we don't have any official statement in "3001" for cascaded CIs; in my view supply to any "cascade" socket must be treated as a final subcircuit.

You referred to clause 3.4.3, but this must be a typo. I think you are probably referring to clause 4.3.3
Note that while "3001" includes several provisions relating to how connectable installations are used; these are not directly enforceable under NZ law. That includes Section 4, in particular 4.3.3 that forbids connecting more than one supply lead to a socket outlet.
Good advice, but not legally enforceable.
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Re: Feeding transportable installations from each other

Post by JamieP »

Correct, was a typo, meant to be 4.3.4, I'll edit the above

Also noted that "Site" is a defined term in 3001

Thanks Alec, appreciate the information
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