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Posted By Topic: Stand alone system

Mar 16 2020 12:02

I've come across an installation that is a stand alone/off grid, PV set-up.

My question is, does any of the work here require inspection? I'm thinking it doesn't?

I've read through Worksafe's publication, dated 15/5/2014. It seems to imply the PV part of the install requires certification not inspection.

....'If the PV system is an independent supply and the inverter is not paralleled to a mains supply it will not require inspection'

I wondered whether anything here would fall under the category of 'mains work'?

Mains work (definition), DOES NOT INCLUDE (b)(i); work on fittings that are used or intended for use by any person in, or in connection with, the generation of electricity for that persons use and not for supply to any other person.

My head starts to spin a bit when I read this? Does anyone understand its meaning? Would a stand alone, off grid system supplying a domestic dwelling fall into this statement? And therefore not be considered 'mains work'

Any thoughts much appreciated. Thanks.

Mar 16 2020 13:20

Unfortunately by not being careful enough with their words; that ES advice is seriously misleading.

There are several aspects of a PV-sourced system that may require inspection.
Firstly the PV array requires inspection of it is above ELV (ESR 6A(2)(a)(iv)]
Secondly the inverter; which requires inspection if it is connected as /mains parallel [ESR 6A(2)(a)(iii)]- which of course for a standalone it can't be.

That's where the advice is misleading, because it correctly says an inverter 6that's not connected mains parallel doesn't need inspection; but forgets that the PV array can need inspection in its own right

Thirdly there's any mains work [ESR 6A(2)(b)]. True a standalone doesn't have any "mains"(because of that bit you've quoted from the definition in ESR 4); but there will still be "mains work" requiring inspection because mains work includes work on the installation's "main earthing system" - and even standalone systems have an MES.

Mar 16 2020 14:08

How about if the entire system is DC, panels, charger and load and no AC is involved?

Mar 16 2020 16:52

ESR 59 requires all installations / part installations to comply with "3000".
There's NO let-off for being d.c.
There's NO let-off for being ELV

There IS an escape for most ELV from being PEW, in Schedule 1; but while that means no PL required it still has to comply with Standards.

And there's an escape if what's constructed is not an "electrical installation" as defined in the act- but the definition is wide enough that not much is excluded (enforcement is a different story)

(Almost) all domestic installations must comply with Part 2.
ESR 60 requires all standalone systems that comply with Part 2 to to comply with 4509.1 - and that Standard requires a main earthing system.

A PV array with open-circuit voltage above ELV ALWAYS needs inspection, because it's ALWAYS high risk PEW; regardless of what it's connected to.


Mar 16 2020 20:44

Okay, Thanks Alec

Mar 17 2020 08:48

Hi AlecK - I have a different understanding to 4509.1 regarding whether earthing is required

Clause states "WHERE the stand alone system output is earthed". The word "where" suggests its not mandatory.

Also further down in 4.4.3 it covers separated supplies thereby implying that a separated setup is permitted.

Also see Figure 4.1 covering both options

Can you explain on what basis earthing is of necessity required

Mar 17 2020 09:04

Yes that "where" indicates that there is at least an option of a counter-condition. Just as "whether" always carries with it an "or not" and "if" carries an "if not".
But the heading of clause 4.4 is "standalone systems supplying a single a.c. load". So those possibilities ONLY occur where that's the case.

What we're talking about is not a single load, but an entire installation (domestic or otherwise) supplied by a standalone system; and that installation must comply with 3000. So it must have a switchboard.
Therefore the relevant clause is not 4.4 but 4.5; and the relevant Fig isn't 4.1, but Figs 4.2 - 4.4 - all of which show a main earthing system. Clause 4.5.3 refers.

For completeness; if the installation is non-domestic then not absolutely required to comply with part 2. Could be Part 1 - but if so must have a certified design that fulfills all requirements as per Part 1, and be no less safe than a design compliant with Part 2. Under those circumstances it may be possible to have an installation without a main earthing system, because ESR 60 would not require compliance with 4509.1.