Inverter in connectable installation

[JamieP]

Am I right in saying that an inverter must comply with AS/NZS 4763 to be used in a connectable installation?

I've had some debate around 3.4.4.4 lately

To me it reads as must comply with AS/NZS 4763 and be either an isolated or RCD protected type under this standard

But I've have others argue it's comply with AS/NZS 4763 as an isolated type or simply be RCD protected

Curious of others opinions around how they read it

[pluto]

I would use "comply with the safety requirements of AS/NZS 4763" due to wide range of inverters available form all parts of the world. Even in Aust. there are very few manufacturers who claim direct compliance with AS/NZS 4763.

[DougP]

The wording looks clear to me.

"it shall comply with the safety requirements specified in AS/NZS 4763 for an isolated inverter or an inverter protected by a residual current device."

it means both types of inverters, isolated or RCD protected, must comply with 4763

[JamieP]

This is also my thought Doug

[AlecK]

Exactly right.
Doesn't have to fully comply with that Standard - which covers portable inverters only.
But must comply with the safety requirements for one of the types listed.
The standard also includes a third type, and these are not permitted under "3001"

[Dan L]

1- assuming I'm looking at the correct standard "4763 safety of portable inverters" it's not very obvious to me the exact safety requirements it needs to comply with unless iv overlooked this.? You could argue most of the contents are for safety.

3010 is similar with only mentions of general requirements

What are the safety requirements?

2- for a EWOF I assume as long as its not a first ewof for a NZ TS checking for 3001 compliance them am I correct in saying these safety requirements with relevant inverter and generator standard does not need to be checked only The changeover switch and neutral to earth configurations (c 7.8.2.1, c. 7.8.2.2)?

[Dan L]

To add to that for a part 1 check on import in regards to generator and inverter what needs to be satisfied for part 1 compliance?

[AlecK]

Correct that safety assessment of WoEF of a NZ-built land-based CI only needs to look at the matters specified in App C of "3001"; not all the other matters specified in main body of the standard; which apply to constructing the CI.
That's on the basis that the CI has originally been installed to comply, and a WoEF check doesn't need to check all that stuff again.
However inverters may have been added since a previous WoEF, and often by people who don't know what they are doing and have never looked at the Standard; so always best to look a little bit harder.

When assessing an imported CI for issue of WoEF; checks have to be made for compliance with every aspect of Part 1.

WRT inverter & generating systems; the key aspects are that the output of the inverter / generator must be in one of the two accepteb configurations:
either an isolated output (ie NO connection between A or N of output & earth), or RCD-protected (ex-factory; with the RCD being an Approved type for NZ).
In "4763"; 3 types of inverters are defined in clauses 3.1.3 - 3.1.5, and illustrated in Fig 1.
A study of the definitions and the Fig should tell you all you need to know.

The wording used in "3001 means that the inverter installed must be as defined; even if the inverter itself is not claimed to comply with the Standard. In particular, the inverter may not be a 'portable' unit, in which case it can't claim full compliance with the Standard.

A point to watch is that many inverters claim to be "isolated", but in fact are "equipotentially bonded" - the type that is NOT permitted for use as part of a CI.
It's often necessary to find the data sheet for the particular unit, and even then it may not become clear.

However, as indicated in "3001", any isolated-output inverter compliant with "4763" will have the "double insulation" (square-within-sqare) sign;
and any inverter with RCD-protected output will be obvious.

[Dan L]

A common situation I'm hearing of is like this fig 2.10A exepet the isolated output goes direct to outlet
- no overcurrent /rcd protection (im not sure how protection upstream at sb would work)

-no N-E link at isolated output (floating earth)

Also another common situation is isolated inverter supplying one outlet off battery, no N-E link again)

Some inspectors tell me they test N-E and get voltage so the inverter must be non compliant. And it may be but from what I understand even if the inverter was compliant in the situation you will still get the N-E voltage because the N-E link is not there so no ref on earth.

In all the figures iv seen with isolated inverter / generator there is always a N-E connection in some form to give the earth ref.

So with that in mind I can see how if installed correctly in an installation they can be used safely.

But what confuses me is how the inverter comes with 230v outlet on the inverter. (not much dif then that supplying one other outlet)

There is nothing to stop you plugging in a multi box then plugging in a selection on of faulty class 1 appliances. If one appliance had a L- unearthed exposed part fault and another appliance has a N-unearthed exposed part fault. And both appliances where touched at same time.

Lastly it seems to me in most cases rcd protected type would be better suited but I assume they much more expensive.

As an alternative in the situation where I isolated inverter is supplying just 1 power outlet would it be acceptable install an mcb enclosure at isolated output with N-E link and rcbo similar to fig 2.10A

[Dan L]

See link at isolated output and inverter example attached

[AlecK]

The first thing to check is whether the inverter is used to supply fixed wiring.
If it's not fixed wiring, then there's no PEW; just plugging-in of appliances.
Therefore Wiring rules simply do not apply.
ESRs can apply to how things are used ( eg ESRs 88 & 89 , also ESR 15), but Wiring Rules only apply to fixed wiring.

Second thing is, if the inverter does supply fixed wiring, whether there is any connection between that fixed wiring and the wiring supplied from external supply.
If there is such a connection, eg via changeover switch; then there is only one system, and it falls within definition of CI.
In which case the entire system is
a) a connectable installation ; so must comply with 3000 & 3001 (as per ER 60); and
b) subject to WoEF inspection as per ESR 78
If there is no connection, then the wiring & fittings supplied from external supply is a CI, and the separate wiring / fittings supplied from inverter is not.
There are vehicles that come ex-factory with inverters supplying one or more LV outlets; but unless there is also an external supply they are not a CI.
Similarly a boat can have an LV wiring system supplied by inverter (or other source, but of no facility for poligging onto shore power; ESRs don't require compliance with any Standard, and no WoEF required
Remember also that a WoEF is only ever required when pligging into an external supplied;
If you have facility to plug in, and never use it; then the CU system mist comply; but no WoEF is required.


So assuming those 2 points don't cover the example you're talking about, and we have an inverter used to supply a connectable installation as alternative supply.
Only two types of inverter are permitted by "3001; either an isolated inverter, or an RCD protected inverter.
In both cases all final subcircuits are required to have RCD protection - regardless of which source is in use
Which means there has to be a N-E connection, and the only difference is where it is.
For RCD-protected; it's within the inverter itself (because it has to be upstream of the RCD).
For isolated-output, it's made by the changeover device (as per clause 3.4.4.3 & Fig 3.2 of 3001: 2008) and this switched connection must be checked as part of WoEF (clause C 7.8.2.1)

So any cases where the required N-E connection does not exist simply do not comply, have never complied, and can't be issued with a valid WoEF


You report that some believe any voltage between N & E on the inverter output means it is non-compliant (presumably on ground of not having an "isolated output" Probably correct if that's real voltage; but inverters by nature are electronic, and there will be trace / phantom voltage that will show up if using modern DMM or similar. For such a test to be relied on, you need to use a "ballast" resistor, or an old-fashioned analogue meter.
However checking compliance or otherwise of the generating equipment is not part of a WoEF check; so NOT grounds for not issuing WoEF.
All we have to check WRT alternative supplies is C 7.8.

Correct that if the (isolated output) inverter is used for direct supply to more than one item of equipment, there can be voltage between the items of the event of 2 simultaneous earth faults. Exactly the same as when using an isolating transformer. Dual earth faults is an unlikely event, and we don't regulate against all possible hazards, only against likely hazards. We do (strongly) advise against use of an isolated source to supply multiple items of equipment; but use is more an HSW matter; and well outside requirements for wiring of CIs or installations. But this is part of the reason the "3001" requires the N-E connection when installing an isolated source. A factor is that in the context of a CI, there is unlikely to be significant physical separation between the two faulty items; therefore increased likelihood of them being simultaniously accessible.

What people may do using EPoDs or similar is up to them, and not the responsibility of either the electrician wiring the CI or the inspector assessong for WoEF. We can only really control what is done as PEW.



Another option is that the CI simply plugs its supply lead into the inverter (or genset).
Doesn't matter whether the source is external or on-board; it's treated as an external supply. As a supply for a CI, it must comply with 3000 & 3001; but this time with Section 2 instead of Section 3. Clause 2.4.
However as there's no PEW involved, simply buying & using the generating equipment, ESRs apply differently.
The guidance is there; but there's not much ESRs can do to make users follow it.

[AlecK]

WRT your suggestion that RCD-protected are somehow better suited; not really true.

In a compliant CI installation, there's RCD protection for all final subcircuits; so it really doesn't matter whether the source is RCD-proected, oe isolated-output with switched N-E connection.

For direct supply to equipment, an isolated-output source eliminates risk of shock for single earth fault; while an RCD doesn't (it simply reduces the exposure time. So safety benefit of RCD over isolated only applies under multiple-earth fault conditions.

[Dan L]

Thank you so much that all finally makes sense.

I really appreciate you taking the time.

I checked out 2.4 3001.

Most common inverters iv seen including mine the outlet on inverter earth pin not connected to frame.

Struggling to see how having the frame of inverter connected to earthing of CI Makes any difference.

Thanks again really appreciate.