Posted by: @astranger

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@transparent Thank you for your answer and I really appreciate your help. I was considering buying a growatt but they seem to be notoriously high idle power consumers from what I read, same for Sunsynk. What do you think of Victrons? I know they are a lot more expensive however I'm happy to pay a premium for extra efficiency. Cheers

 

Our Sunsynk 5kW uses 20w at idle.

Posted by: @vaugi

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Our Sunsynk 5kW uses 20w at idle.

That's a very low figure for an inverter with integral off-grid operation.

I wonder if that's because they have good monitoring with temperature sensors to modulate or switch off cooling fans.
Or perhaps they don't use large transformers, such as Growatt do.

Transformerless (TL) inverters are lighter, cheaper and more efficient.
But the electronic design is tricky to get right.

True TL circuitry:

• has no (galvanic) isolation between the mains side and the storage battery side
• can have residual DC remaining on the AC 240v output
• needs careful earthing to avoid current in the ground-loop; this can result in trips operating
• has difficulty driving inductive loads
• is more susceptible to damage from external spikes/surges

@transparent

Here are a few videos on it

https://www.youtube.com/watch?v=G2Ut1TYwyiU

@transparent when you say second device are you suggesting I don't need to swap out my existing inverter connected to the PV? I did get a quote from an installer who suggested putting a further array on and installing a hybrid inverter and keeping the existing connected just to the PV but at 10k can't justify that right now so just going through the buying separately and assumed the existing inverter would be swapped and sold or kept in storage in case I added further panels in the future?

Sorry it's a bit long winded!

You're quite right to ask for clarification, @bretix

My comment about a second device being installed was made in response to what @robl had just posted.

In your case you'll be replacing one inverter with another. You already have G98 approval from the DNO for a grid-tied inverter, so in theory you might choose not to reapply.
In practice I suppose a fresh G98 application should be made so that the DNO can check the model of inverter against the ENA's approved list.

However, this is also affected by what you are calling a 'hybrid inverter'.

I have four inverters working in my house at the moment.
But only one of those has the capability to export electricity back to the grid.
That has DNO approval.

The other three are off-grid hybrid inverters, and they connect to storage batteries.

When they operate in the reverse direction, that stored energy cannot be fed back to the grid.
As it is impossible to export, they can be installed without any DNO approval.

Personally I think that rule is wrong... but I don't write the regulations!

Posted by: @korwraith

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NH00 fuses for a DC fused disconnect led me to the following product: https://www.solartradesales.co.uk/keto-battery-disconnector-with-80a-fuses which I'm able to source for £47 delivered incl. fuses (£16 less than the Bimble Solar solution). The fuses are 80A rather than 125A but given my Solis inverter has a maximum charge/discharge current of 60A I believe that'll be sufficient.

What is the product code on these 80A fuses? It appears that not many Jean Mueller fuses are DC rated, so it would be good if we could cross-reference it with the list on the manufacturer website.

Posted by: @transparent

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Posted by: @robl

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My understanding is then that the bare minimum "official" thing I need to do is get a sparky to connect up a new circuit to our consumer unit.

Yes. 🙂 

Whilst I don't mind 'upsetting' MCS, there are good reasons why I always advocate staying the right side of the rules which apply to DNOs and qualified sparkys.

As you will be adding a second 'device' capable of export to the grid, you have rightly obtained the G99 approval from your DNO.
For the sake of others who will read this in future, that G99 application is required even if the new SunSynk inverter is to use their inbuilt zero-export technique.

which is why i have now had my sofar me300sp removed by my electrician. he was going to go down the process of informing re the installation (he is a qualified electrician but has little knowledge of this area) 

i will be submitting the correct approvals (G99??) and no doubt leaning heavily on those who have been through the process for guidance/advice.

he will be fitting a Sunsynk 5kw which is on the approved ENA list (and was recommended by a very knowledgable person on here (LOL) and it will be set to zero export as we have a 4kw PV system installed under the FiT scheme. I have discussed my install with Sunsynk and they have told me it will do what i want it to do, i.e. charge at a higher rate than my sofar did.

interestingly, when i contacted my DNO, i was told i must employ an MCS registered electrician and they will do all the necessary paperwork. i told them i would be using a competent and qualified electrician and we will be submitting the paperwork together as he has no experience in the 'paper trail', she didnt seem best pleased .....

PS my electrician (self employed) is often contracted to do the installation of heat pumps and inverters by 'companies' who then make their profit on top of his endeavours, so he is experienced and competent but just hasnt got his head around the approvals process.

any advice/suggestions are more than welcome ...

the install will be 

Sunsynk 5kw ECCO inverter (SYNK-5K-SG04LP1)

28.6kw of storage (i hope that the amount of storage isnt an issue as it wont feed to the grid?)

Existing 4kw PV installed under FiT - which wont be altered/ammended 

Posted by: @misterb

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she didnt seem best pleased

👍

Posted by: @misterb

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any advice/suggestions are more than welcome

I *think* the Sunsynk will do what you want.

• Leave the existing FiT system in place;
• get the CT clamp the right way around immediately house-side of the electricity meter;
• set "Zero Export" (and "Solar Export" or is this relevant only to the solar directly connected to the Sunsynk?), "Priority Load" check-boxes plus "Grid feed trickle" and "Export power limiter" on "System Mode 2" page;
• set up a charge/discharge schedule in the "System Mode 1" page;
• also double check the inverter firmware version (and label on the side of the inverter) and ensure G99 grid mode is set!

With this done you should be golden.

Posted by: @misterb

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he is experienced and competent but just hasnt got his head around the approvals process.

Sounds like they need to move up the food chain; just a few hours of tick-box exercises can increase their earning potential. I don't think competence has anything to do with MCS accreditation.

Posted by: @misterb

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when i contacted my DNO, i was told i must employ an MCS registered electrician and they will do all the necessary paperwork. i told them i would be using a competent and qualified electrician and we will be submitting the paperwork together as he has no experience in the 'paper trail', she didnt seem best pleased .....

That's a shame.

I don't which DNO you have, but it should be the case that their RIIO-ED2 'agreement' with Ofgem requires them to become DSO in nature.
In brief that means they become a service-based operation.
They must engage proactively with the general public (us!), Community Energy Groups and local Councils, in order to provide better access and use of the distribution grid (below 400kV).

The website for your DNO should already have all the information, guidance and forms which you require to apply for G98/G99 and G100.
Such a phone call shouldn't have been required any longer.

My DNO (NGED) are moving the process beyond even that level.
They are working on a system to provide approvals for most (common) applications for grid-connections within 24 hours (and often less than 1 hour).

Prior to Ofgem stipulating the DSO requirement, our DNOs were more likely to take a dominant role in stating the terms under which they were prepared to allow you to do something.
Those days should be over.
But I'm unsure how Ofgem are measuring the level of compliance.

Right now I'm having a problem with my 3 Phase Sunsynk using it as an AC-coupled battery system with an existing FIT system (30kWp).  

I can get it to discharge upto the CT clamps, but what I can't get it to do is to charge based on export.  I've fiddled with a lot of settings but still no go.  There are Sunsynk (Keith Gough) videos out there showing it as an AC-coupled inverter, however it's confused as one of the video shows a solar array feeding into the Gen port and using "micro inverter" settings - but this has a low maximum power, and not something I want to do with my FIT system.

My next step is to upgrade firmware and hope it's just an issues with that, and if not, will have to contact Sunsynk support.

Posted by: @vaugi

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this has a low maximum power, and not something I want to do with my FIT system.

Sorry to hear you are having issues integrating the systems together.

I think https://www.sunsynk.org/forum/technical-support/ac-coupling-causing-excess-energy-import shows there are (or at least were) issues with using the aux port and micro-inverter setting (leaving aside the 50% power limit and changing an existing FiT system which sounds wrong from a payments perspective).

https://youtube.com/watch?v=pez0ZlthRbQ makes it look so easy, although it is single phase and the load and PV look to be fairly static.

Posted by: @vaugi

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showing it as an AC-coupled inverter

At the risk of stating the obvious (or even non-obvious),

suggests that you need to set the microinverter check-box ("For micro inverter input"?) on the Aux page even if you are AC coupling (i.e. not putting the inverter on the Aux AC connection).