Upgrading Inverter on a FIT system

[cojmh]

After some advice if possible.

I was reading Openspaceman's recent thread and I am thinking of something similar but didn't want to hijack his thread so I am starting this one. My thoughts keep evolving and I am sure that some of this has been asked/answered before but I am putting it all in one place to make it easier for everyone to understand what I want to achieve overall without necessarily finding my other posts etc.

I will be adding to my existing FIT system and I am concerned that I will have inverters fighting each other plus there are other limitations I would like to rectify/achieve at the same time without affecting my FIT payments.

Currently I have a solax SKU5000E hybrid inverter with 4x Pylontech US3000C batteries. This is connected to 4.65KW of LG panels

I also have a solar diverter (Eddi) that will divert excess generation to the hotwater tank and then to a hot-tub.

All of this works reasonably well and my only issue is that the hybrid inverter can only supply 2.5KW from the batteries (batteries are capable of supplying 5KW). This system is paid FITs and I have permission to feed in up to 5KW to the grid.

I am looking to add a second hybrid inverter in an out building with 7KW of panels and another stack of Pylon tech batteries. However, I am not intending to use another Solax inverter. I have spoken with the DNO and they might be able to increase my export limit to 7KW (including the 5KW I already have) so I will need export limiting.

From Nowty's response to Openspaceman it looks like rather than just add another inverter and try to get it to work with the solax unit (which is 8 years old anyway out of an expected 10 year life) - it might be better to redesign the whole thing to work properly with what I now want to achieve.

So my questions are:

1. Can I replace my Solax inverter even though it is not broken and still keep my FIT payments. The panels, batteries and everything else will stay the same. I am assuming I can as I would need to do this if the inverter failed. There is a generation meter on this inverter so it should still be totally accurate for the FIT scheme. The only thing that would change is the ability to get 5KW from the battery stack as opposed to just 2.5KW currently.

2. Are there any inverter manufacturers that will allow multiple hybrid inverters to run at the same time without fighting each other and achieve all of things below:

• Increase my total PV generation to 12KW across two hybrid inverters (a 5KW and a 7KW) but to export limit to a maximum of 5KW across both inverters with a preference for the FIT system to generate if I need to curtail the overall generation

• Increase my total battery inverter supply to 10KW from the two battery stacks (across two inverters in two different locations each supplying 5KW each)

• Both hybrid inverters to work even during a power cut

From other posts I suspect SMA and Vitron might be able to do the above? - but are there any other special considerations I need to be aware of?

I still intend to have the Eddi solar diverter in place and I am sure in the next 5 years or so there will be a car charger (Zappi) in the mix too.

Thanks in advance for any help

[Marcus]

Luxpower do an a.c. coupled system that allows the battery inverters to be paralleled, but the installation I'm thinking of is a customers and i wasn't involved with installation or setting up so i don't know whats involved. Or how well it works TBH.

They do have 3 x 3.6kw luxpower battery inverters with 12 pylontechs split 3, 3, and 6 between the inverters. I haven't seen the solar inverters yet so can't say what they are.

[cojmh]

Luxpower do an a.c. coupled system that allows the battery inverters to be paralleled, but the installation I'm thinking of is a customers and i wasn't involved with installation or setting up so i don't know whats involved. Or how well it works TBH.

They do have 3 x 3.6kw luxpower battery inverters with 12 pylontechs split 3, 3, and 6 between the inverters. I haven't seen the solar inverters yet so can't say what they are.

Thank you for the information - I will have a look.

Do you know if this is a single phase setup (just thinking 3 inverters and therefore possibly 3 phase)

Thanks

[nowty]

@cojmh, does your current hybrid inverter not have facility to charge from the grid ?, or do you have a bi-directional FIT generation meter ?

I.e. I presume your not clocking up the generation meter from recycled grid leccy.

https://www.ofgem.gov.uk/sites/default/ ... idance.pdf

[cojmh]

@cojmh, does your current hybrid inverter not have facility to charge from the grid ?, or do you have a bi-directional FIT generation meter ?

I.e. I presume your not clocking up the generation meter from recycled grid leccy.

https://www.ofgem.gov.uk/sites/default/ ... idance.pdf

Hi Nowty,

No, my inverter cannot charge from the grid - so no recycling or FIT fraud going on

The batteries are all DC side on the hybrid inverter.

[Marcus]

Luxpower do an a.c. coupled system that allows the battery inverters to be paralleled, but the installation I'm thinking of is a customers and i wasn't involved with installation or setting up so i don't know whats involved. Or how well it works TBH.

They do have 3 x 3.6kw luxpower battery inverters with 12 pylontechs split 3, 3, and 6 between the inverters. I haven't seen the solar inverters yet so can't say what they are.

Thank you for the information - I will have a look.

Do you know if this is a single phase setup (just thinking 3 inverters and therefore possibly 3 phase)

Thanks

Yes single phase 60a supply on 16mm2 tails: i can't remember how many kw pv they have (12 or 15 possibly). I seem to recall another box in a different cupboard to the batteries that could be part of it - or maybe it's the solis box I'm thinking of.

[nowty]

@cojmh, does your current hybrid inverter not have facility to charge from the grid ?, or do you have a bi-directional FIT generation meter ?

I.e. I presume your not clocking up the generation meter from recycled grid leccy.

https://www.ofgem.gov.uk/sites/default/ ... idance.pdf

Hi Nowty,

No, my inverter cannot charge from the grid - so no recycling or FIT fraud going on

The batteries are all DC side on the hybrid inverter.

OK so the answer to question 1 is,
If you had just a PV FIT system, then nobody would notice you changing it to another PV inverter. The issue is that practically all new hybrid inverters will have some sort of grid charge capability but you can officially change it to a new hybrid with FIT provider approval if you change your generation meter to a bidirectional one, info is in the OFGEM doc I referenced.

Answer to question 2 is,
Yes, quite a few now allow paralleling up, the LUX Power Squirrel Pod is an example. An alternative is to add a more modern hybrid inverter with the new PV and replace your FIT based Solax with a PV only inverter, thus moving the existing Pylontech's to the new hybrid inverter.

[AGT]

I’m sure I read recently that you can update anything on your original FIT PV system, so if you had old 250 watt panels from 10 years ago, and had the space to go 400 watt you do this, but the fit still pays the same rate but for the original percentage

Sure this was on the buildhub forum

[openspaceman]

I was reading Openspaceman's recent thread and I am thinking of something similar but didn't want to hijack his thread

No worries about that, a bit of thread drift doesn't bother me and I will be following this.

It is good to see nowty's responses, I was not aware having an import-export meter for the FIT system could allow replacing my Solarmax inveter with a modern hybrid and battery was an option, should it fail.

[cojmh]

No worries, sometimes it is not clear who might get upset or not, so I tread as lightly as possible.

Something that has just occured to me ....

I think I am right in saying that you can opt out of the export payment part of the FIT payment and instead register with a company like Octopus that will pay for the energy exported.

The question then is ....

Can I replace the export only meter with an import/export meter with the permission of the FIT provider so that I can update the current hybrid inverter. This should then keep the FIT provider happy as a way to monitor what is generated on the original system.

Then to also have another overall export meter (or import/export meter) which is what I would use to say how much was exported for the purposes of claiming export payments from a company like Octopus.

If this was allowed then it would mean I keep my FIT payments for generation and update my inverter. But it would also mean potentially being paid for all exports by both systems (old and new) from whichever company I sign up to which will pay for PV export.

So .... have I made all that up in my mind or is that actually possible?