@transparent 

Thanks. It's definitely safe, all according to 18th edition regulations.

@profzarkov why can’t you use an s-bend on boat drains/toilets, or are they there and it’s just because they don’t have a high enough stink pipe/ tank vent?

Posted by: @bash

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It's definitely safe, all according to 18th edition regulations.

A mains supply to an inverter can com,ply with 18th Edn, and yet still not have a bi-directional RCBO.

The issue was addressed in a separate addendum... and not all qualified electricians understand the necessity for the change.

That's why I'm reiterating it here for the benefit of a wider readership!

@transparent 

Thanks. A double pole RCBO was installed in readiness for our installation.

Thankfully we had an excellent electrician who installed our CU's. They were very helpful in giving some advice also and even popped back to check our batteries and inverter after I installed them. 

@papahuhu Thanks for that .. OvO was offering 15p/unit 24x7 with a cap at 6000 kWh as I recall. I'd love to be able to use solar but a maritime climate 7 degrees off the Arctic circle is not the best starting point. I reckon I'd dip into oil on at most some of 60 days per annum and circulating at 50-55 degrees it'll be a fraction of the CO2 output that it was. I'll keep looking at options but until the Government stops going backwards on affordable solutions then that is probably the least worst way forwards

@dr_dongle 

With panels so historically cheap don’t dismiss it. We are not as northerly as you but are at high elevation and have poor solar conditions because of mountains and trees. The difference in cost between putting 12 panels or 36 panels is only minor if you let installers aware that you understand the actual trade prices of the hardware. Batteries have started plummeting in price too. 
2 panels both outputting 60% of their peak is greater than one perfect panel at 90%. That’s how we did it, flood the property with panels and it is very profitable, of course depends on the direction of export tariffs. 

Posted by: @papahuhu

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flood the property with panels and it is very profitable, of course depends on the direction of export tariffs. 

Profitable perhaps...
... but not grid friendly unless you're on a 3-phase supply.

What export limit has your DNO allowed you to have?

Have a look at this discussion on losses due to phase imbalance at the local substation.

This issue isn't widely known about...
... including by those in the Dept of Energy. 🤦

The Secretary of State is about to launch a new strategy to encourage more rooftop-mounted PV panels.
But I expect it will be promoted for both in-home battery storage and for export.

When the Feed-in Tariff (FIT) scheme was started 1st April 2010, substation losses were at about 5%.
Now they're running at 10% for domestic properties.

That's unsustainable.

@transparent 

1P only. Wish I was on 3P, we have a long tarmac drive, didn’t want to dig it up.

My G99 application was for 11kWh, they only gave me 9 unless I would upgrade.
The installer forgot to set my export limit and for a couple of weeks it was peaking at 12 ish, it did cause some problem that I don’t understand and my installer got a slap on his wrist.

The DNO attitude was that I could have as many panels as I wanted, it was just the export that was limited. I’m on the octopus VPP, so they manage my system. Very little gets clipped as I actively manage my large loads, I waste a kW or 2 but only on the very highest solar intensity days, which isn’t often where we live. I get the real benefit of an oversized array in the shoulder months. 

Posted by: @papahuhu

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My G99 application was for 11kWh, they only gave me 9 unless I would upgrade.

[...]

The DNO attitude was that I could have as many panels as I wanted, it was just the export that was limited.

Aagh!

Guidance from the Electrical Networks Association (ENA) is that domestic export should be limited to 16A per phase by default.

So it's surprising to hear that your DNO is prepared to allow you as much as 9kW (not kWh !)
There must surely be particular circumstances which have affected the calculations in your favour.

This timeline from May'24 shows three Grid Monitors, Brown, Peach and Grey, at different locations about 5km apart.

Ignore the red-line. It's the output from an off-grid storage-inverter.

The underlying voltage fluctuations are normal, and due to regional supply & demand at 33kV and above.

Line voltages for the location of the Brown Monitor are above the other two because of high levels of local (rooftop) solar generation.

When the regional generation sources are changed by the DNO at 14:00, the voltage at the Brown location rise above the statutory 230v + 10% (253v).
Consequently, solar inverters in the area detect the over-voltage and cease export, causing a sudden voltage drop.

Every household with a solar inverter connected to substations near that location is no longer exporting... whilst householders remain oblivious.

This demonstrates one of the many reasons why DNOs don't want high levels of export, especially from single-phase properties. 

@transparent 

The AC output from the PW3 is 11.5kVA and input is upto 20kW of DC. I’ve heard of people getting approval for the full output, so I felt hard done by my restriction. I am within 200 yds of the substation, perhaps that helps and there’s only 2 houses with PV nearby, as I said, we aren’t in prime PV territory and that’s why I supersized to make it economically viable. I understand the math behind the climate models, being in the data profession, and know it’s bunkum, so my motivation is monetary. 

Hmm...

whereas I understand the physics behind grid topology and operation, and I know it's being threatened by political policies 😯 

We can't keep on being 'unfriendly' to the grid which supplies us, and expect to get away with it.
Spain is learning that the hard way as a result of their national outage on 28th April last year.

My motivation is resilience, rather than monetary.

@transparent Yes, but I went through and followed the correct procedures. If the procedures are wrong thats for the electrical engineers to remedy. 
I can’t remember the last time we had a power outage, must be more than 8 years ago. Whereas in the 70s and 80s there were many. So something is working very well as is.