Posted by: @jamespa

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Posted by: @editor

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@jamespa I can answer this one now because I asked the country manager (and it will be included in the review) and the system does island, so it will continue to run the house. We only have a 4kWh stack to test, but the new version will be able to stack to 20kWh-is which makes it interesting.

Interesting, that raises quite a few questions on which I am sure @transparent will want to comment!  Whats the maximum output power in island mode?

I think it's 2.4kW as per the inverter, but I will confirm that. The app is actually really, really good and you can set input and output limits as you like, but I can't use it yet until I've 100% verified our RCBOs are OK. Also, once the smart meter is installed, that will allow me to fully put the kit and settings to the test.

@editor,

Very interested in balcony solar.

Regarding Bidirectional RCBO’s.

Am I correct in assuming you can fit it into a maximum 16A ring main ?

Would it be a type A, curve B or type A, curve C ?

Would the entire consumer unit need replacing with Bidirectional RCBO’s or just swap over the one for the ring main the balcony solar is plugged into ?

Would there be an issue fitting a fused spur into the 6A lighting circuit considering an 800 watt input is 3.4 amps and my property lighting circuit contains 7 led bulbs and a bathroom fan totalling less than 100watts ( 0.43 amps ) which are obviously not switched on during the daytime when the sun is shining ?

Thanks in advance.

@chrisbollo, @transparent will be best positioned to answer this. I’m hoping my electrician will come and see me this week, and I’ll produce some content on this to help explain this because there’s a lot of confusion surrounding RCBOs.

Oh wow...
... I'll need to start disassembling these comments and seek clarifications.

Plug-solar is a massive subject area., and Plug-in storage makes it all the more difficult to understand the regulatory and technical issues.

At the moment DESNZ is busy modifying regulations to accommodate Plug-in solar, which will take several months.
The IET and organisations representing electrical trades are anxious, and I can understand why.

There simply isn't enough knowledge amongst the British general public to understand the implications.

There are two sets of regulations which presently cover installation of solar panel inverters to the
electricity supply:

BS EN 7671 is the Wiring Regulations, as published by the IET. All qualified electricians apply this
standard, and their work is regulated by Profession Trade bodies such as NICEIC.

EREC G98/G99 is an Engineering Recommendation which applies to any generation or storage
equipment that connects to the electricity grid. It applies both to the physical apparatus and the
method by which it should be connected.

Both BS7671 and G98 are legally enforceable. The regional DNO can disconnect any generation
equipment which has been installed contrary to these regulations.

Posted by: @editor

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I asked the country manager (and it will be included in the review) and the system does island, so it will continue to run the house.

That's insufficient to describe what's happening.

'Islanding' is the term usually applied to devices which continue to supply the mains power in your house when the grid is 'down'. That's prohibited under G98 rules.

What is possibly being referred to here is an Indevolt battery which has two independent 240v AC outputs.

• one connects to the household mains power circuit, and will cease export if there's a power-cut
• the other output creates its own 50Hz 'mains frequency' and continues to run any connected devices during an outage

Posted by: @editor

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yes, it should work alongside your rooftop solar and existing battery bank. It’s an AC-coupled plug-in system, so you just fit a CT clamp on the export line and set it to charge only from excess PV. The app looks excellent too and you can fine tune import/export times with loads of other parameters.

I don't think it will directly charge your fixed batteries as it charges itself when it sees surplus solar, which is perfect for adding extra capacity on sunny days without messing with your main setup.

Which raises a technical issue:

How could the Indevolt Battery prevent another 'fixed main battery' from charging itself using power stored in the Indevolt Powerflex?

It can't.

It's a function in the other fixed battery which would have to prevent that, but I can't see how.

The Powerflex is 'ignorant' of any other fixed storage unit. It simply supplies its stored charge to the household mains when there is demand.

Posted by: @editor

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I can't use it yet until I've 100% verified our RCBOs are OK.

That depends on how you plug in the Powerflex unit.

The issue we've discussed elsewhere on this Forum relates to what happens in there is a fault with a plug-in inverter (solar or battery) and there's a power-cut.

If there's no fault, and the battery's inverter genuinely does work to the G98 Standard, then a uni-directional RCBO doesn't get damaged.

One day something will go wrong with a plug-in inverter

• but it might not be the Powerflex unit you're testing
• and it might not be this week

Posted by: @chrisbollo

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Regarding Bidirectional RCBO’s.

Am I correct in assuming you can fit it into a maximum 16A ring main ?

Would it be a type A, curve B or type A, curve C ?

Would the entire consumer unit need replacing with Bidirectional RCBO’s or just swap over the one for the ring main the balcony solar is plugged into ?

Let me explain this in a generic fashion.
We can then use this post as a reference point for other readers in future.

In the great majority of British homes, electrical protection is provided either by a Residual Current
Device (RCD) plus a Miniature Circuit Breaker (MCB), or a Residual Current Breaker with
Overload protection (RCBO).

When a qualified electrician installs a solar inverter, a new protection device is added to the
Consumer Unit to allow that connection.

If there’s an existing RCD, then it must be a Type-A or Type-B. Those will operate safely if there is
some Direct Current (DC) output exported by the inverter alongside the 240v AC.

If an RCBO is added as the new protection device, then not only must it be Type-A or Type-B, but
it must also be bi-directional.

That’s an amendment to the 18th Edition of the Wiring Regulations, issued in July’24. The more
common uni-directional RCBOs are no longer suitable for connecting an in-home appliance which acts as
a generator of electrical power.

Although it's an unlikely event, a uni-directional RCBO can be damaged by being connected to such a power-source.
It will still operate for over-current, but no longer trips if there is later an earth-leakage due to cable damage or
someone receiving an electric shock.

The householder is unlikely to know that earth-leakage protection is no longer present.

And that's what troubles the IET.
Because that risk exists, it wouldn't be permissible to add a generation/storage device to that household circuit.

Responsibility for electrical safety in the home has shifted.

Previously all protection against fire and electric shock has been delivered by devices in the
Consumer Unit. Installing those has been the exclusive preserve of qualified electricians.

Once you have Balcony Solar and Plug-in Storage being plugged into 13A sockets by the
general public, then it's no longer the case that electrical safety remains
in the hands of the IET, NICEIC and their qualified electricians.

With Plug-in Kits, the onus for safety protection shifts from the Consumer Unit to the
micro-inverter itself.

How is the choice of protection trip relevant to Plug-in Solar or Storage Batteries?

Balcony Solar Kits are being made legal for DIY installation at a time when there is already a
problem with RCBO protection being unsuitable for domestic solar inverters.

A high proportion of professionally-commissioned (rooftop) solar installations prior to July’24 are
connected to the mains using uni-directional RCBOs which are already compromised.

That matters much less if an RCBO supplies a circuit which is dedicated to the inverter.

But it does matter for 13A sockets on a ring main.

Very few householders would understand enough about protection trips
to know which types are in their Consumer Unit.

There is no common symbol for a bi-directional RCBO. Moreover, the relevant manufacturers’
markings aren’t usually visible unless the Consumer Unit is opened.

Householders will install Plug-In Solar or Storage kits without being able to know whether this increases the
risk of fire or electric shock at some point in the future.

RISK LEVELS
If the micro-inverter is a design which is tested and approved, then it will shut-down in the event of
a mains outage, and no damage will occur to it or any RCBOs in the Consumer Unit.

If the micro-inverter is unapproved and not G98-certified, then the level of risk increases. This risk
is greater if more than one micro-inverter is being used.

The question is not “Does this micro-inverter work?”,
but “What happens when this micro-inverter fails?”

The highest risk occurs when a micro-inverter fails during a power-cut, and is connected to a mains
circuit which is supplied from a common uni-directional RCBO in the Consumer Unit. The
householder won’t know if the earth-leakage protection is still effective. They won’t even consider
checking to see if it is by using the in-built test button.

The explanations I've given above are derived from a Technical Briefing document which I've sent to a few relevant elected Councillors.

As you'd expect, the document has been forwarded to the area Trading Standards Department, who are required to advise Councillors regarding the level of risk, and how it might be mitigated.

That doesn't necessarily mean that new legislation is required.

A public awareness campaign might be more effective!

Posted by: @transparent

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connected to the mains using uni-directional RCBOs which are already compromised.

I can only comment based on my knowledge and educational journey so far, but the biggest challenge will be for homeowners to look at their CU and identify if an RCBO is uni- or bi-directional without having to consult their electrician, and whether they need any upgrades. 

I think there are yet bigger challenges.

Whatever are the discussions going on in DESNZ, in practice the Secretary of State, the DNOs and the IET can do little to affect the present situation. Householders have been buying and plugging in Balcony Solar and Storage micro-inverters for the past couple of years. Kits are openly sold online, both in UK and from Far East suppliers, such as Alibaba.

The vendors' URLs are being deliberately omitted in this post.

Most of those micro-inverters have no G98 testing or certification. They may operate above the 800w limit, impose an incorrect waveform onto the mains, and have inadequate safety protection in the event of a fault.

Unaware of why the regulations exist, or why the IET and professional electricians raise objections, consumers purchase these DIY solar and storage kits and simply plug them into a 13A mains socket.

Some people will buy several such inverters, not considering whether the micro-inverters will interact – possibly each one causing the other to stay ‘live’ during a grid outage.

Consumers will use extension leads to make the mains connection, unaware if the cable-rating is adequate, or the earth-resistance low enough to cause a trip to operate under fault conditions. If the safety protection is inbuilt to the inverter (rather than in the distribution board) then this matters.

@transparent Thanks for the detailed explanation. 

Please forgive my density, im getting a bit lost in what may happen if you buy a microinverter from Alibaba, and what is inherent with plug in inverters.  Can you help me separate these cases and., for the avoidance of doubt, can you clarify whether or not a micro inverter that (as designed) meets the regulations (as opposed to one but on Alibaba that may not) poses a material risk?

Am I right in deducing from the above that a microinverter that does not meet the regulations, if it is faulty during a mains outage, may/will reduce the circuit protection to the same level that would have been present if the circuit were protected by and MCB only, or indeed a fuse (as many still are).  

Does the same apply to a micro inverter that does meet the regulations?

Many thanks

Posted by: @transparent

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Whatever are the discussions going on in DESNZ, in practice the Secretary of State, the DNOs and the IET can do little to affect the present situation. Householders have been buying and plugging in Balcony Solar and Storage micro-inverters for the past couple of years. Kits are openly sold online, both in UK and from Far East suppliers, such as Alibaba.

Which is a problem when almost anything that is desirable is outlawed - sometimes a good argument in itself for legalising things.

Posted by: @jamespa

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I'm getting a bit lost in what may happen if you buy a microinverter from Alibaba, and what is inherent with plug in inverters.  Can you help me separate these cases

Sure.

Let me first place my Alibaba reference back into context.

I commented that there are micro-inverters being sold online from both UK suppliers and on Alibaba, and that "Most of those micro-inverters have no G98 testing or certification".
I illustrated this by reproducing a screenshot of a micro-inverter offered for sale which operates above 800w.

G98 contains a number of requirements which must be met by devices that export to the 240v mains electricity system in your house.
Foremost amongst these requirements are:

a: if there is a power-cut, the inverter must stop exporting within one mains cycle (20mS).

b: when power is restored, the inverter must wait a randomised period of time before it starts exporting again

c: the 240v AC output from the inverter must conform to a clean sine-wave and reduce higher-frequency harmonics below a defined threshold.

d: whilst it is recognised that inverters also impose a DC component onto their 50Hz output, this must be below a defined threshold

e: if the inverter's output is 800w or below, then two of the G98 conditions do not apply, but the rest still do

f: the inverter must have a safety isolator between it and the grid

I have deliberately worded the above requirements in plain English. I'm hoping this makes them more accessible to readers here, rather than me simply reproduce the G98 technical terminology.

It follows that when a micro-inverter device (solar or storage) is deliberately being sold in breach of one of those G98 requirements then you can't expect it to have been tested to any of the others.

When you buy a plug-in inverter with its output rated at 1200w, then you can't have confidence that it will cease exporting when there's a power-cut.
Or, for example, the DC component of the output waveform may be more than 10mA, thereby preventing an earth-leakage trip from operating when there is a genuine fault.

Turning to your second point about "what is inherent with plug in inverters"...

1. they are being plugged in to a circuit which has an existing protective device in the Consumer Unit. That protection was defined by a qualified electrician, and the circuit tested (Building Regs Part-P) who gave no thought to it having a source of generation connected to it.
2. we have no criteria (Standards) which apply to the situation where more than one micro-inverter is plugged into the same circuit. In order for them both to cease exporting during a power-cut, does there need to be a detection-mechanism? Should a plug-in generation device run a check/test to see if another inverter is also present? If so, how could that work?
3. since the circuit protection must now be integral to the micro-inverter, what parameters should be capable of triggering its operation? If the household mains circuit is fed by an old-style fuse in a distribution board, should the inverter be designed so as to incorporate earth-leakage protection?

The above isn't exhaustive, but illustrative.

However fastidious the DESNZ is in trying to develop amendments to G98 and BS7671, their problem is being complicated by there already being uncertified micro-inverters widely installed. Is it possible or reasonable to expect a properly-certified new micro-inverter to operate correctly if it is plugged into a circuit which already has an uncertified generation device on it?

Posted by: @jamespa

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Am I right in deducing from the above that a microinverter that does not meet the regulations, if it is faulty during a mains outage, may/will reduce the circuit protection to the same level that would have been present if the circuit were protected by and MCB only, or indeed a fuse (as many still are). 

Yes. That's true.

But the householder won't expect that, of course.

If an electrician advised a mother to have RCBOs fitted for the Kitchen circuit and the 13A ring main in order to prevent her children being electrocuted, then that's what she expects will provide that protection.

Why would it occur to her that the plug-in solar or storage device she bought a year later might damage those RCBOs and prevent them offering earth-leakage protection.

If Freddy succeeds in sticking a knitting needle into the electric toaster and Freddy gets frazzled, who would think it has anything to do with an inverter bought at a reputable DIY outlet? That micro-inverter may not even be plugged in at the time.

Posted by: @jamespa

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Does the same apply to a micro inverter that does meet the regulations?

Yes, but the risk level is likely to be lower.

An inverter may fail to disconnect its export from the grid when there is a power-cut within the required timeframe.

Let's imagine that the inverter develops a fault. It remains 'live' for another 10secs or so.
That might be sufficient to burn out the tiny solenoid wire in a uni-directional RCBO.

The whole point of having these safety protection devices is that they cope when there's a fault.

Now the rules are shifting.
The fault itself might damage a protection device.

Yes, the probability of that occurring is very low.
But it's not zero.

The probability of a serious injury or a fatality occurring due to an inverter pranging a uni-directional RCBO is 1.0
It will happen somewhere and at some future point in time.

Holding those two apparently-contradictory statements to both be true is more than I expect 90% of the general public to understand.

The next question is... does @editor understand what I've just written?

... because if he doesn't, then I don't give much hope for the Secretary of State for Energy appreciating the issue.

Posted by: @transparent

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The next question is... does @editor understand what I've just written?

... because if he doesn't, then I don't give much hope for the Secretary of State for Energy appreciating the issue.

The honest answer is I had to read the posts several times and each pass was slower than the last, and now my lips are sore.

For someone like me, with a fairly limited understanding of domestic electrics (albeit learning quickly), there’s a lot to unpack there. And that, in itself, is a big problem IMO.

The risk isn’t people digesting G98 in detail, it’s someone buying a plug-in solar or battery kit from somewhere like Wickes or Aldi because it looks great, plugging it in and not giving a second thought to what’s sitting in their consumer unit, whether that’s RCBOs or anything else.

As for the Secretary of State for Energy, there’s no chance he’s getting into this level of detail. The hope has to be that the people around him (his @transparents) are properly advising and steering policy so these systems actually work safely and as intended in UK homes.

I’ve actually started working on a script to break this down into something far simpler, because if we can’t explain it clearly, we’ve got no chance of it being understood or addressed properly. I’ll run my final script past you @transparent just to make sure I have everything right.

@transparent 

Thanks.  I cant speak for @editor, for politicians or for the Secretary of State, but it would certainly help my understanding if the risks could be summarised in as few words as possible. 

I'm only really concerned with compliant devices used in accordance with the manufacturers/local instructions, as its entirely obvious that, if you buy a non compliant electrical device or fail to observe the instructions, whether it is a micro inverter or indeed anything else, there may be additional risks.  Im as yet unclear whether the rules (and thus presumably the instructions) for plug in solar will extend to the connection of multiple micro inverters, I had understood the answer to be 'no' but concede I may be wrong.  However before trying to think about multiple devices I would like to make sure I understand the one device case.

So let me try to summarise that case (based on what you say above) to check my understanding:

The risk with a single compliant device is that it develops a fault the consequence of which is that it fails to disconnect within the required time should grid power failure occur.  In this circumstance it may blow the solenoid in any unidirectional RCBO (or RCD?) protecting the circuit into which it is plugged, which will negate the residual current protection (but not the overcurrent protection) for the circuit(s) protected by that RCBO.  There is no way to tell that the RCBO has been damaged, the damage will not be detected when the test button is pushed.

This risk for any single installation/household has not currently been quantified to the best of your knowledge, but given that it exists at all, over time and many installations, it is more or less certain to occur 

Is this correct please? 

As a supplementary:  This risk, which in fact applies to any generating device, was recognised in regulations only in July 2024 and thus any solar or battery installation prior to that may also, depending on how it (and other circuits) have been wired into the CU, suffer from the risk.  Noting that these are generally higher power devices the risk may be higher, but at the same time it is mitigated if the inverter is on a circuit which does not share residual circuit protection with other circuits