@transparent 

I think your point is a valid one. It might be worth you contacting your local fire authority (not fire station) to start some dialogue. It may be that operational risk assessments have already been undertaken but I am doubtful and if course any safety feature that can be put into place rather than to rely on human recognition and subsequent actions is often the better option. 

Posted by: @transparent

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Posted by: @chickenbig

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There should not be a CT clamp around the cable to the inverter; it knows how much current it is pushing out.

Erm... that CT clamp is an input to the MP 3000-SE (Sofar's battery storage controller) rather than the pre-existing PV inverter.
According to the manual, it should be there.

-- Attachment is not available --

I have yet to understand why the 3000-SE has two further CT inputs which are unused. Let's come back to that later if we need to.

 

Posted by: @chickenbig

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your latest photos do not show which ethernet cable wires are used to convey the signal back to the Sofar box; I hope that only a single twisted pair is used.

I've zoomed in and had a closer look at an earlier photo.

-- Attachment is not available --

This doesn't appear to be correct.

It looks like Orange/Org-Wht and Brown/Brn-Wht twisted pairs are connected to the Wago block with the red wire.

Each CT clamp needs to have one twisted-pair connecting it right back to the MP 3000-SP.
By that we mean that the red/yellow wires should be twisted together, and then connected to one of the four twisted-pairs in the ethernet cable.

Are you saying that the red/yellow wire from each CT clamp should effectively be one wire? Yet +  and - connections for each CT clamp are required by the inverter? 

Posted by: @misterb

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it might be worth you contacting your local fire authority...

OK, will do.
I already have the right contacts in local government to make that approach to the area fire authority.

On this evening's BBC TV news I saw an interview with a Fire Authority Officer in Cambridgeshire which gave inaccurate information regarding hazards from re-charging batteries within the house overnight.
He really was trying to identify the type of battery which can burst into flames if left on charge. But unfortunately he gave it the incorrect name.

As technology advances, the public do need to be made ever more aware of how to handle particular materials. This includes recyclable plastics as well as batteries.
But the information obviously has to be correct.

I would hope that this Forum will continue to be viewed as a place where we can get the facts right... whether or not there is a legal requirement.

Posted by: @misterb

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Are you saying that the red/yellow wire from each CT clamp should effectively be one wire?

One pair of wires (a colour and its white dashed companion); within the Ethernet cable they are twisted together to reduce noise.

Posted by: @transparent

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We discussed adequately-sized DC breakers earlier on this topic. You can buy them on eBay or Amazon but note that some are directly shipped from China.

Indeed I've been going back-and-forth between using MCBs, MCCBs and fuse isolators. For my mother's system I've settled on fuses, just so I can point to official paperwork that these are DC rated to an appropriate level. I did go so far as to try testing a 160A Tomzn MCCB by shorting a couple of LF280K batteries, and managed to get it to slow and fast trip, but somehow my testing of particular currents and (low) voltage did not make me satisfied that it would safely disconnect at 56V and > 10kA.

As @chickenbig has replied in text, may I also do the same, but in graphics...

Here is the twisted-pair configuration we're discussing, which is the correct way to avoid picking up electrical noise on the wires.

I've shown the pair in the 'ethernet' cable being "blue and its white", but you can choose any of the four colours you wish, provided you also use its white.

@transparent 

thanks, that clears up a bit of confusion, mainly on my part .....

i actually ran two separate ethernet cables, so prob only needed to run one ! however if i go to the next stage, which seems likely i will need the other cable for CT comms with a second inverter.

i am already thinking of adding additional storage, another seplos mason case and potentially adding a second me3000sp. i want to increase my battery storage and the potential to charge the batteries at a higher rate than 3kw during off peak periods. 

i have (so far) 4kw of PV which was installed a few years ago under the second phase of the FiT scheme. so any inverter would need to compliment that as i dont want to lose/compromise those FiT payments. 

can anyone advise on a suitable replacement inverter please or offer guidance on whether i should just add a second sofar ?

Posted by: @chickenbig

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a 160A Tomzn MCCB [...]  but somehow my testing of particular currents and (low) voltage did not make me satisfied that it would safely disconnect at 56V and > 10kA.

I think that's the correct conclusion.

An MCB/MCCB is designed to trip at currents which are around 2x its rating.

To provide protection for a short circuit at thousands of amps, you require a fast-blow fuse (Type T).

On my inverter/battery combiner board, I therefore have both fuses and MCB trips.

The above photo shows a prototype, capable of linking together up to four batteries (connected at the bottom) and four inverters, connected to the MCBs at the top.

You might also see a row of four 500A contactors. These have either computer control to open/close them, or a manual override. That's the board at top-right with the red, green and white status LEDs.

There are two 'faults' with the above layout. It will be further adapted to overcome these.

Posted by: @misterb

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potentially adding a second me3000sp

This is where things get very complicated. Do the ME3000SP have parallel capability? How would they coordinate ramp up/down and share the power required between them.

Also we've skirted over the topic of notifying the DNO of the additional generator (i.e the first ME3000SP). The ENA web-site does not list the Sofar ME3000SP as being G100 approved for export limiting. For more power I think you might have to just upgrade your solar and battery setup with a nice hybrid inverter; something like a Sunsynk ECCO 5kW or 8.8kW would then simplify what you are getting permission for.

@chickenbig 

re the paperwork etc. i assume the electrician who installed it is dealing with this side of it, i did enquire as to whether he is qualified to undertake installs of battery storage systems prior to him installing it. my original install of PV was done a few years ago, i understood that as i was not exporting any more than already approved then fitting the ME3000SP would not affect that, they just needed notification via g99 - though i do admit to not knowing much about anything !!

Stuart Pittaway (you tube) fitted the sofar me3000sp after having had solar for quite some time and went through the notification process very easily, so i am not sure why mine is any different at this stage? my set up is identical to his ?

this is a question i posed to a seller re an additional inverter

@misterb if your chosen electrician has fitted the equipment with approval from your DNO, then you should have received a copy of the letter which gave permission for G99 (more than one device capable of exporting, with export-limitation).

You only require an MCS-qualified electrician if you are to claim the Smart Export Guarantee (SEG) income from your Energy Supplier.

Posted by: @misterb

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am not sure why mine is any different at this stage? my set up is identical to his

Export approval from your DNO is separately assessed for each location. The DNO uses a computerised input-form which checks about 20 factors. These include the spare capacity on your sub-station transformer, the cross-sectional area of the conductors which supply your house, and the number of dwellings between you and the transformer which are on the same phase.

Having the same equipment as Stuart Pittaway isn't something they look for  😉 

2: I don't like the sound of the dual 3000-SE connection system as proposed by your supplier.

a. Cascading the batteries in this fashion means that the 'master' is being charged/discharged to a greater extent than the 'slave'.

b. Despite have two 3kW battery controllers, only one is active at a time. You can't achieve 6kW output by using them in parallel, such as you describe.

You're asking all the right questions... so keep it up!

i am trying (VERY trying as my wife would say) - thanks for sticking with me ! 

i obviously need to speak to the electrician who said he has all the correct qualifications/certificates to do this type of work, to make sure i am within the rules/regulations required. i have no reason to doubt him, he has been doing work on our rental portfolio for almost four years now, so i see no reason why he would tell me has the competency and quals if he didnt. 

The stuart pittaway comment was really in relation to the inverter being an inverter on the approved list, which i assumed it must be for him to get approval and i fully take on board your comment re 'no two installations are the same' and just because someone else has done something, doesnt give carte blanche for everyone else to do it! 

i am not one to flout the rules or legislation, its not in my DNA, if something needs doing i like to have it done correctly. However i do like to get on and do things, sometimes too quickly, even before ive finished one 'task' (still in the middle of modding my starlink router to run off 12v for instance !!)

so i really do appreciate everyones comments, people are only trying to help and point me in the right direction, however frustrating i am to some LOL