@transparent

Spot on. The single phase inverter (my mistake  it's sofar not solax) was DNO'dand MCS'd and installed before going 3 phase.

Then the inverter ( SYNK-10k-SG04LP3)  and batteries (GSL 2* 10kw) were installed....without MCS as advised I wouldn't require it. 

So can I use the original set up MCS in this scenario? - I'm assuming I can't get retrospective MCS for the 3p inverter if that is required? 

The original solar set up remains for house use and excess is exported to the grid although I'd rather have it to the batteries because even though it's summer I'm still finding we use 20-50kw/day (on an overnight tariff) and that's with the heating off and the hot water on twice per day during the summer. Although ev charging also is added into that the batteries still get good use out of them so am also thinking of doubling the capacity of those but the quotes are equalling the same as the panels unless I go DIY.....which when I've added up what I want comes in significantly less than 4¹/² K!

@transparent will read it in bed tonight. We have been ranting off subject, but priceless I may say. May  I ask if the solar cables are polarity conscious, or can I connect any end of the string to any socket. And what is it that causes damage if the system is not shut down correctly.

Let me deal with @david999 's point first because it will take less time than what I have to write about the plant-room with @bretix ' heat-pump equipment, inverters and batteries.

Yes, solar cabling is extremely polarity conscious...
... to the extent that there are male and female versions of the MC4 connectors!

Nowadays it is usually the case that PV panels come equipped with flying leads that already have the correct connectors at the ends.

Inverters, similarly, are sold with chassis-mounted MC4 male and female connectors protruding from the base.

The MALE is positive, and its visible o-ring seal is often coloured red.

The FEMALE connector is negative.

Posted by: @david999

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And what is it that causes damage if the system is not shut down correctly.

If what isn't shut down correctly?

Any inverter installation is going to have more than one source of power available to run its internal electronics:

• mains-power in from the grid
• solar panel input(s)
• battery
• mains power output, which may been wired in parallel with other inverters and no isolator switch

So how do you imagine you are going to 'switch off' an inverter?
... randomly try a combination of the above?

The manufacturers will invariably state a preferred order in which you can safely stop the inverter for any maintenance work.

I'm unsure where you've read the idea that damage can be caused.
Give me a context and I'll try to interpret what's happening!  🤔 

@bretix I’m on the octopus go tariff and it’s 7p per kw from 11.30 through 5am my batteries discharge to grid 4pm to 5pm but during the winter my 10kw batteries were exhausted by midday.  My heating system was installed badly then but I doubt even now that my batteries will go beyond this. On this tariff the feedback is only 15p but I doubt during winter I will export anything.

@transparent I’m sure somebody mentioned damage by not shutting down properly earlier in the thread. I have a procedure document that details shut down but was curious in terms of what could go wrong doing it wrong.

Posted by: @david999

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it’s 7p per kw from 11.30 through 5am

Not quite.

There's a randomised delay in your Smart Meter.
The tariff periods aren't synchronised to UTC/GMT/BST, but delayed in an attempt to prevent surges on the grid.

If you switch on a high-power device like a battery charger or EV charger precisely at 11:30 pm, then you're still being charged at peak rate until your particular meter switches to the next tariff-period.

Further details are discussed here in the topic Incorrect Billing of Customers with Smart Meters.

Posted by: @david999

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I have a procedure document that details shut down but was curious in terms of what could go wrong doing it wrong.

Well you could end up damaging yourself, I suppose. 😱 

You wouldn't want to be re-plumbing electrical connections whilst unaware that the inverter was still passing power through them.

@transparent fairly good with electrics thankfully, can’t say I haven’t had a shock mind you. But I’m still alive, the important point is don’t play with something you don’t understand. 8 months ago I hadn’t a clue about heat pumps but I could install one now and credit to you guys. Been looking for some literature on solar installation but not much luck so far.

Yes @david999 -

@johnmo is correct. Failing to switch stuff in the right order can break things... such as your cardiac rhythm. 🤒 

It's also bad practice to make cable connections whilst those cables are still 'live'.
Clamping a 'live' battery cable into a connector is likely to cause an arc to flash across.
That can create pitting in the surface of the metal, and possibly oxidisation.

Cable connections carrying high currents will get hot if they're not being made with clean metal.

As a general rule, you're unlikely to have too many isolators, trips and fuses in a home storage installation.
I have three different points of isolation between my batteries and the inverters.

And I also have three between each solar panel array and an inverter.

That photo shows an 'old' arrangement.
But it shows the general idea just the same.

@transparent that looks like a bomb I saw in mission impossible. Wife says I have no heart so I’m safe.  Don’t worry, although the line connection guys do it live I don’t.  Just need to remember and switch meter from ac to dc though. But I’m intending on covering the panels during the installation to prevent shock or arcing issues. Probably run the cables to and from the panels etc and plug in at night thinking about it.

Before we discuss anything more about the inverters and batteries in @bretix 's plant room, please allow me to post this portion of a photo above.

This doesn't comply with Building Regulations Part-L "Conservation of Fuel and Power".

I've placed arrows pointing at

• a pipe that appears to go straight through a concrete-block wall. The hole should be sleeved and the insulation continues right through
• main isolation valves on the heating circuit without insulation around them
• insulation which is gaping open because it doesn't use a 45-degree bevel cut at the corner
• gaping insulation where it's been compressed too much due to holding it with a nylon tie
• uninsulated pipework within 1m of a thermal vessel

We already have a topic "Is this a bad installation...?" where all this has been discussed.

It's currently 30-pages long.
But I posted lots of graphics there which you can skip to and quickly assess what we're discussing at that point.

If you want more help, please join in with that existing topic and re-post the photo above to which I've added the arrows.
We can pick up the issues there and help you increase the system efficiency.

Posted by: @david999

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@transparent fairly good with electrics thankfully, can’t say I haven’t had a shock mind you. But I’m still alive, the important point is don’t play with something you don’t understand. 8 months ago I hadn’t a clue about heat pumps but I could install one now and credit to you guys. Been looking for some literature on solar installation but not much luck so far.

As you are aware, follow the prescribed shutdown procedure relating to the inverter.

As far as solar panels are concerned it may also be prudent to cover them with suitable material to effectively shade them if you are connecting and disconnecting the solar array wiring. Alternatively you could carryout this work after sunset.