Section 4.5 - 4777.1-2016

[Slovett]

I have a question about section 4.5 in 4777.1-2016.(I know 4777.1-2016 is not sited in the regs, but I can't find the 2005 version).

4.5 States that an an Isolation device shall be provided between any energy source and the Inverter.

Therefore does that mean that PV installations with Micro Inverters installed at each Panel require an Isolator between every Panel and Micro Inverter? Or does this not apply in this situation because the DC portion of the Installation will never exceed Extra Low Voltage? (I can't find any exceptions)

Thanks

[JamieP]

"Where the energy source is a PV array, the isolation switches and isolation arrangements
shall comply with the requirements of AS/NZS 5033."

So you'd just follow what 5033 says in regards to this, problem is the cited version of 5033 which is the 2012 is more directed at string systems than micro systems

Reason you can't find the 2005 version of 4777.1 is because it's a AS standard not AS/NZS so it's not free for us, should definitely look at getting a copy of you're doing PV installs

[AlecK]

Can't "just" follow 5033; because that para is not written as an Exception but rather as an additional requirement.
So have to comply with both.

[JamieP]

I get what you're saying but I was reading it as 4.5 covers "Isolation Devices" in general, which it does but when the system is a PV system, that the requirements to follow are are specifically in 5033

[AlecK]

One Standard is not supposed to set requirements for matters outside its Scope, and within the Scope of another Standard.
But many do - as in this case.
4777 cannot actually impose a requirement for anything to do with the PV array.
It can however come close; by
(a) setting a conditional requirement for the installation of the PCE ; with the condition being the fact of something outside scope existing
In this case the requirement applies to the isolator for input to inverter (which is within Scope); and the condition would be that the source to be isolated happens to be a PV array.
(b) pointing to the fact that other rules are imposed by other documents.
In which case the proper wording would be a simple statement that the isolator required to an input to PCE from an array is, or may be, also required to satisfy requirements set by '5033".
Being purely advisory; this sort of warning is supposed to be a Note; is is not supposed to use the word "shall" (which imposes a requirement).

Problem is that Committees sometimes do things they are not supposed to do, and it isn't always picked up by the editors.
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So what we have in 477.1 is clause 4.5 setting a number of requirements for isolating devices.

Para 1 says every input from any source must have an isolation device.
Because it doesn't say "switch"; the requirement for being securable in open position is relevant (for isolating switches it goes without saying - as does all of 2nd sentence).

Para 2 covers location & accessibility;
2nd sentence relates to one-per-source; so expanding on para 1 (Another rule says "1 idea per para; so this sentence should actually be in para 1)

Para 3 says no semiconductors.
Didn't need to be said; because covered by para 1

Para 4 goes back to location; expanding on para 2 - and has an exception, so para 4 is switched off for any of the 3 stated conditions.

Para 5 is (additional / alternative) requirement(s) for input isolator where source is a PV array.

Para 6 is (additional / alternative) requirements where source is a battery

Para 7 again imposes a requirement that it has no right to impose; as above.

Point being you can't apply para 4 (or paras 6 & 7) by themselves.
Nothing anywhere in the clause switches off paras 1, 2,or 3.
Para 4 is only switched off for one of the stated conditions - and the source being an array or a battery are not listed as trigger conditions for the Exception.

So every source must comply with 1,2,3, & 4;
PV source must also comply with 5
and battery source must also comply with 6 & 7.

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I suspect the intent may have been that the same device could perform the functions of both PCE input isolator, AND PV / battery output isolator; rather than having 2 devices.
But presumptions of intent don't outweigh what the words actually say.

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[JamieP]

Thanks Alec, appreciated as always

[Slovett]

Thanks Jamie and Alec - I don't do Solar but Im Setting up a system at the workshop and trying to get my head around the relevant Standards. In this case Its a Enpahse Micro Inverter System. Its 1 Micro Inverter per PV Module - No Hazardous Voltages are present on the DC side when disconnected (ELV). Because it is ELV, does it then fall out of the scope of 4777.1?? Or would you expect that also to be included in 4777.1 as an exception?

EDIT - Im guessing it doesn't matter what the Input Voltage is therefore no exception in the case of it only bing ELV on the DC input side - the Standard sets out requirement for Grid Connections of Energy systems Via Inverters, which this is. Thanks

[AlecK]

Agree the input voltage level doesn't determine whether the Standard applies;
It applies due to the output being grid-connected.
And ESR 60 takes that another step, by making compliance with the Standard mandatory (if following Part 2 of 3000).

Unfortunately none of this helps with your original question WRT how to have an isolating device on the input of a micro-inverter.
I'd expect that to be covered by an Exception to 4.5, but like you I can't find any (yet).
May be coming in next revision - this is an area where advabnces on technology are proceeding faster than Standards can keep up.

[TPower]

I’ve never seen a dc isolator on an individual panel before supplying a micro inverter. Enphase installation instructions certainly don’t show them installed like this.

50334.4.1.2 may be relevant. There seems to be an allowance in this clause for the use of connectors for disconnection purposes with micro inverter installations.

Clause 5.4 of 4777.1:2005 says ‘an appropriately rated plug and socket may comply with this requirement’ with regards to isolation between energy source and inverter.

[AlecK]

So far we've been discussing the requirements set in 2016 edition; which is not the edition cited in ESRs.

Looking at cited 2005 edition; the relevant clause [5.4] is much simpler.
An isolation device (not necessarily a switch) must be provided between the energy source and the inverter, unless the inverter is physically integral with the source. The device has to comply as a device for isolation under "3000"; and also has to be capable of safely breaking voltage & current under both normal and fault conditions.
That's pretty clear as to intended purpose & required functionality; and the Exception covers the exact point originally asked about
( not written in the standard form of an Exception; but the word "unless" has same effect).

And yes, the Note following the clause explains that "a" plug and socket "may" comply.
Whether "a" can cover using a pair of connector sets (one for positive & one for negative) is arguable.
And "may" isn't as clear as "is deemed to"; because "may" used in this way carries the alternative of "or may not".
The intent was probably to grant permission; but all they've done is mention a possibility.

In re-writing the requirement for 2016; a lot of stuff was added in. Some of it adds new provisions.
But a lot simply isn't needed ; and/or fails to clearly express intent.
In the process, the exception for integrated source / inverter has been lost.

The revised wording "unless the energy storage and the inverter are physically integral" at first glance looks like carrying the old Exception forward.
But crucially this effective Exception now applies only to the accessibility of the isolation device; rather than to the need for having such a device.
It also applies only where energy storage is integral with the inverter; and not where the energy source is integral.
Given that micro-inverters integrated with PV modules are now common; while batteries integrated with PV modules are almost unheard of; this looks like a simple case of unintended word-swapping.

Also a requirement for being able to secure in open position (always required for isolating devices that are switches) has been added in a way that applies to all devices for isolation.

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This sort of thing is why there's a style guide for writing Standards, to minimise opportunity for misunderstanding.

Overall, with the number of editorial issues in the 2016 version of the clause, I'd have to mark this as an significant - almost epic - "fail" by the EL 042 Committee.
But it also represents a failure by regular users of the Standard; who had opportunity to comment on the draft of the revision - but clearly either failed to notice the changes or failed to suggest improvements to the wording.

[JamieP]

I was wondering if MIs could be used in situations like this in accordance with ESR14A and obviously following all instructions because of as you said, standards don't always keep up with technology but it seems nothing in ESR59 and 61 allows for the use as such as an alternative to 3000 and if to part 2 obviously 4777.1 as well, unless of course you did a design under ESR58 and claimed such as a part 1 solution? Simply stating on the design that all of 3000 part 2 was followed except for the inverter connection has followed MIs

Although that wouldn't work for anything that had to comply with part 2 under ESR59 (1), which is probably the case for most micro inverter installs

[AlecK]

Yes , could do a Part 1 CD - but as you say not for anything required to be fully Part 2