Hi, just curious on whether you progressed your upgrade and what you chose?

I haven't, I still cant make the business case work with less than 10 years payback relative to just sticking with Octopus Go and loading as much as I reasonably can into the overnight period.  

I suppose if your pv inverter packs up, you have a plan? 

I must say I don't much care for the Solis instruction manual which does concern me, the Sunsynk one is much better.  On the other hand Solis have answered my questions, I have yet to ask any of Sunsynk.

Hi, just curious on whether you progressed your upgrade and what you chose?

I haven't, I still cant make the business case work with less than 10 years payback relative to just sticking with Octopus Go and loading as much as I reasonably can into the overnight period.  

Probably if I didn't already have solar panels (and a functioning solar inverter) it would make more sense, but I do!  Ho hum.

Hi, just curious on whether you progressed your upgrade and what you chose?

...

and you have to charge the PW3 (albeit at cheap rate). I reckon this saves about £1/day over a standard tariff for a cost of the order of at least £8k installed. I understand that the top end battery storage systems come with guarantees of up to 15 years but in most cases capacity losses at 10 years will be 10-20% - all of which adds up to at least £500 per annum in depreciation. Unless I've messed up my figures then I can't make it cost effective.

That makes sense. I thought better to comment in this thread. 

Modular systems like Fox seem to now be available including from big players like Octopus with installation included and at much lower price points. No endorsement intended.

And the DIY route that a site like RHH enables makes a system with 8kw hybrid inverter and 16kwh life04 battery (that even provides UPS capability), possible for less than £3k all included. Depending on your location, you may be on positive ground before year 3. In that type of scenario, unless the tariffs change very quickly and in unusual ways, the investment seemed fairly low risk. In my case, much faster payback and less headaches than PV.  

In this thread we were looking at ways to combine several inverters in the same installation, so potentially applicable. Even if the prospect of upgrading a PW based systems by using it to feed a Solax, Sunsynk or Solis may cause severe anxiety to Tesla salespeople..

I’m quite intrigued by sodium ion batteries over lithium.

See what I posted over on that other topic:

Prices are very similar to FePO4 but the nominal cell-voltage is slightly lower (3.1v instead of 3.2v)
and the operational range is much wider (1.5v - 4.1v).

Suppose your Na-ion battery was to supply a heat-pump which required 3kW (at 240v)...
and that you had 16 cells in series.

A fully charged sodium battery with cells at 4.1v would be operating at 65½v and delivering 45A to the inverter.

As it reaches 10% capacity, the battery voltage would've fallen to about 48v (3.0v per cell – see green curve below)

At 48v the inverter would now be drawing 62A current from the sodium battery.

Although the sodium battery would happily allow you to use that last 10% of capacity, the increased current you'd need means that it's unviable.
The cabling would need to be thicker to carry currents in excess of 100A, and the BMS capable of handling that too.

For that reason a system based on sodium ion chemistry requires inbuilt cut-offs to limit the current,
as opposed to Li-ion technology which has limits imposed to prevent damage to the cell electrodes.

The concepts are similar, but the approach is slightly different due to the wider voltage range.

We discussed this recently in the Sodium battle thread, @editor . There are very few systems available to consumers and they do not look very mature. Inverters able to handle sodium are significantly different, so the initially available systems are not modular (like commonly available lithium based systems).

The current low starting price for lifepo4 batteries and the expectation (given the relative cost of lithium vs sodium) that sodium based would be lower cost does not indicate a fast uptake...

The regulation mandates labels indicating that there are multiple generation sources in the site.

Would you care to say which regulation you're referring to?

When I was looking for the regs for labelling when introducing an inverter able to export, I started with some of the questions present in the G99 commissioning form like: 

• Generator’s Installation satisfies the requirements of BS7671 (IET Wiring Regulations). 
• Suitable lockable points of isolation have been provided between the PGMs and the rest of the Generator’s Installation. 
• Labels have been installed at all points of isolation in accordance with EREC G99. 

As I wanted to make sure the electrician would have the required labels, I purchased a set of labels of the type suitable for a PV installation. A subset of these were then applied in and around the consumer unit and inverter. Something like the below: 

For guidelines including an overview of labelling, this IET article seems relevant.  Ultimately, qualified electricians have access to the current regulations. 

On this forum I don't think we can conjecture all the possible fault scenarios which inverter wiring should provide a level of protection against.
But videos like this give me sufficient 'feel' for the subject that I find myself erring on the side of reducing risk.

That seems the right way to be going.

Yes and it can be very difficult to give advice without assessing all the site conditions. The video you shared seems to focus on risks related to earthing, but I appreciate it is not easy to find one describing specific islanding inverter topics.  

My approach has been that, given how few domestic electricians have extensive experience with inverters, etc, it helps readers to become informed owners. They may be able to do some of the planning. Whilst using an electrician is essential, more knowledge helps. I do not even envision trying to understand all the extensive considerations that MCS would impose on this type of installation work, in terms of ideal calculations of ROI, etc (mainly because, at the end of the day, MCS does not provide a guarantee themselves..).  

The regulation mandates labels indicating that there are multiple generation sources in the site.

Would you care to say which regulation you're referring to?

In my quest for safe practice I am often 'fed' relevant clips on YouTube.

This one from eFIXX about possible types of Neutral and Earthing faults is informative.

https://www.youtube.com/watch?v=2ksVI-ws1m0

On this forum I don't think we can conjecture all the possible fault scenarios which inverter wiring should provide a level of protection against.
But videos like this give me sufficient 'feel' for the subject that I find myself erring on the side of reducing risk.

That seems the right way to be going.

In your case @jamespa the Changeover Switch in a separate enclosure would also provide that functionality via a Centre-Off position.

That would make sense; the 2 off mcbs would need to go in the same enclosure so the challenge might be to find the right kit of parts!  A quick search didn't turn up any din mounted 4 pole 100A changeover switches with centre off other than an unbranded Chinese one.  Hopefully one exists!