@transparent can they all be on the same rail or require separate rails/enclosures?

Like this?

You're too fast for me @makia2023

I was just about to add this image to my previous post

You can place all the MCBs on the same rail, and there's no requirement to enclose the assembly in a box, although it would look neater than my layout!

Yes, your diagram looks good to me.
You have a separate MCB to isolate each battery if required,
and you have an MCCB to separately isolate the battery input from the inverter.

Theoretically, that MCCB is superfluous if you only have one inverter.
You could simply use all three of the battery MCBs.

A DIN-rail module width is calculated in units of 18mm.

Almost all double-pole DC-rated 125A MCBs are three units wide (54mm)
... except for those made by Geya, which are 36mm.

@makia2023 

It does BUT I'm certainly no expert or particularly experienced in any of the technical nuances of PV/Storage. I only know what I've read, which is different and to me not as good knowing from training and experience. 

Having said that, I do have experience with my own set up and the mistakes I've made along the way. Thankfully I've been able to sell on my Sofar inverter without losing too much money! 

1st mistake - not actually knowing what I need in order to achieve what I wanted. 

2nd mistake - not overspeccing what bought. I should have gone for the Sunsynk from the start but I didn't know enough at that stage. I didn't know anyone who had added battery storage to an existing FiT PV system that I could learn from. So I used YouTube, which was good but took me down a dead end without options to then add to my system. I am beginning to wonder if I should have gone for the 8kw, BUT I got the 5.5Kw at a very good price, so even if I sold it I would get close to what I paid.

I should also have gone for 304Ah cells, instead of 280Ah, minor issue I know, but as things moved on and the Seplos 280L case came on the market, it would have made more sense, even for the odd extra KW. 

3rd mistake - being in a hurry! If I had sat back and given myself time (which it appears you are doing!) I could have got what I wanted first time around. I am trying to do that now, I would like to get a few extra KW per day out of my battery, so I either need anither battery or more PV., or both if I can get S/H panels at a good price to go on either a car port (not built yet) or mounted vertically on a south facing gable end wall. 

The consideration though, is the extra investment of aroun £3k really going to repay itself? At the moment I do have the funds but is it worth it to save a few £100's per year. S/H panels installed by me will prob cost @£600 and the return on them would be quicker, and increasing storage from Fogstar would be @£2400 and would then allow that excess to be stored!!! 

We are on Octopus Go with a 4 hour cheap rate which is working really well, we have Dimplex Quantum storage heaters (not the WiFi ones sadly) and a mini split, the mini split will eat power when it gets cold, so the option of having enough cheap rate power in a larger battery is enticing.... Of course 4 hours at 5kw per hour isn't going to fill 28kw of battery (although allowing for 90% charge down to 10% discharge brings the useable capacity to @23kw so it's close, whereas an 8Kw inverter would be over specced! But I don't need 28kw for 12 months of the year .........!! 

So after all that (useless?) background info, my advice is take your time, work out the best option and then add some additional capacity to your initial purchases! 

PS yesterday with Octopus we got free power between 2 and 4pm so I got as much as I could into the battery, if I'd had a bigger inverter and battery I could have got a lot more for free ..... If this is going to be the norm during high winds then it would appear that that is something to put into the equation. 

Posted by: @transparent

↑

You're too fast for me @makia2023

I was just about to add this image to my previous post

-- Attachment is not available --

You can place all the MCBs on the same rail, and there's no requirement to enclose the assembly in a box, although it would look neater than my layout!

 

Yes, your diagram looks good to me.
You have a separate MCB to isolate each battery if required,
and you have an MCCB to separately isolate the battery input from the inverter.

Theoretically, that MCCB is superfluous if you only have one inverter.
You could simply use all three of the battery MCBs.

 

A DIN-rail module width is calculated in units of 18mm.

Almost all double-pole DC-rated 125A MCBs are three units wide (54mm)
... except for those made by Geya, which are 36mm.

Do I need type T fuses on both the +ve and -ve lines? Your pic only shows them on the +ve?

Kind regards

Stew

You only need to fuse one of each pair of battery cables.
It doesn't matter whether it's positive or negative.

Have a look on ebay.
There are sometimes Type-T fuses which get offered from 'excess stock' warehouses.
Frequently they have been acquired via receivers who are dealing with a business that's folded.

Ok. I've done all my buying. I've settled on where I am putting everything (internally to the house, right next to the board for ease of install and maintenance). I've also decided to go with an ATS with independent ground rod earth. I intend to do most of the install myself, with my electrician completing the AC install into the board. I do however have a few other questions:

Currently my battery/inverter are straight into the consumer unit. I assume this needs moving to a separate garage consumer with its own tails (otherwise backup load will feed back into the same board)? Surely causes issues?

 For the new I dependant earth do I just connect to the existing earthing block or will it need an independent block?

I take it the ATS will sit on just the tails of the board I wish to power with backup load? This creates an issue as my ASHP is on a separate Proteus board. Seems I can either have backup power to home, or backup power to ASHP, and no both? Any way around this?

My ATS is a 240v DPDT relay. It only feeds my 'outside' fridge and freezer, i dont see why you cant add one to your ASHP circuit - even though it may mean running an additional feed from your inverter. 

the inverter has (??) a time delay in both starting and stopping the supply to the ATS and by wiring it through the relay, only one power source can feed to the fridge/freezer at any one time 

Yes. My point is I want to run both the ASHP board and the main board.

@makia2023 

wouldnt my suggestion work?

run an additional cable to your ASHP - depending on power demands of course, and then add the relay to connect both supplies with just one cable then to the ASHP?

In case I haven explained myself clearly. Please see photo below. Two cables entering the enclosure, one is normal power supply, the other is feed from inverter emergency power supply. The relay inside the enclosure then allows power to pass as normal, but if there's a power cut, the relay closes allowing power from the inverter BUT only after the inverter actually supplies it, so there's a 5 second delay, determined by the inverter setting. 

Ah I see. I will talk to my electrician if he ever gets back to me

A few technical points:

1: The lower 'board' which I've shaded orange, should be solely for the equipment which belongs to the DNO and your Energy Supplier.
That's the Service Fuse, Meter and Henly-blocks.
Technically the backing board itself belongs to your DNO.

I don't think they'll mind you having the manual isolator switch on the left of that board,
but an electrician can insist that other items are relocated away from the lower board in order to satisfy DNO requirements.

2: It is up to the electrician to decide on earthing arrangements.
There are different regulations, depending on whether the supply to your house is PME (Protective Multiple Earth) or not.

A consumer can't just decide on their own to have an additional/separate earth installed.

My own house is not PME, and must therefore have its own earth stake, with a maximum resistance to ground of 200ohms.

Due to ground conditions, my electrician deemed it necessary to have two earth rods, linked with a 16mm2 wire.
Sometimes a longer rod is used, but in my case that wouldn't have been sufficient.
Local electricians understand the soil/ground conditions in the area, and are more likely to get this right.

As I also have a number of lightning/surge suppressors, they have their own earth wire...
... which connects them to the same pair of earth stakes.

The strategy is to minimise the likelihood of there being a potential difference if lightning were to strike nearby the house.

A direct strike usually isn't such a major problem.

3. During a grid outage the Neutral connection supplied by your inverter operating in 'off-grid' mode can differ in voltage from the DNO's Neutral feed.

An electrician would normally cater for this scenario by requiring circuits that can run appliances off-grid to be fed from a separate consumer unit.
There must be no possibility of those two neutrals becoming mixed/entangled across the house circuits.

I presently have three separate consumer units above each other for the 240v AC circuits.

That separation provides the flexibility to change the arrangements as I make decisions over time.

Note the copious use of labels and colours.
In future it should be apparent to any electrician which circuits are supplied by what!