UK DIY Install

[RibbonFox]

Hi,

Sorry this may have been asked, but I'm not sure what to search for.

I'm in the UK and want to install solar and a battery, with the ability to charge from both the solar and grid. I get that I need a hybrid inverter. I've spec'd a system but I'm not sure of 2 things:

1. As it's DIY, it wont be MCS certified meaning I can't export. How does this impact the wiring/installation? Or doesn't it? Can I still do what I hope to?
2. Are there any schematics for this type of install that someone can point me to?

thanks

 

[1234enough]

To connect a grid tied system DNO permission is required in the UK, which what you describe it is.

 

[DIYrich]

On grid, and off grid with grid connection, can be done the same. With the exception that the off grid can't power anything before the ac input. With ct's you can use an on grid and not feedback the grid.

 

[ShaneC]

I built my system (off grid office shed) with separate components to give me compete control. I have a 24v charger I can use to charge the battery with overnight if solar isn't enough. There's no way that power can feed back into the grid. I wouldn't trust a lot of the cheap AIO devices out there to not accidentally feed back which could result in a big fine (or killing a linesman which is why these rules exist).

 

[kommando]

MCS is not required but a competent electrician can either do the wiring or sign off/correct your installation. G98 limits you to a 3.68kw system but is DNO inform only, no waiting for permission from the DNO, go over the 3.68kw and its G99/G100 where you apply in advance and wait for DNO permission before install can take place.

 

[RibbonFox]

Thanks guys. I probably should have called out what I'm planning to do as well.

• Sunsynk 8kw ecco hybrid inverter
• 3x 5.12kw sunsynk batteries
• 4kw solar (8/9 panels)

The reasoning is that my consumption peaks at about 7.5kw at any point in time, so the 8kw inverter covers that (or have I mi's understood here?). Also, it means I can charge the batteries quickly, which I'm considering as I may switch to Octopus Agile in future.

MCS is not required but a competent electrician can either do the wiring or sign off/correct your installation. G98 limits you to a 3.68kw system but is DNO inform only, no waiting for permission from the DNO, go over the 3.68kw and its G99/G100 where you apply in advance and wait for DNO permission before install can take place.

Interesting. Does this blow my ideal system above?

 

[kommando]

Interesting. Does this blow my ideal system above?

Depends on your DNO, you can approach them first and check what the local conditions are, if any of the local transformers your connection uses are overloaded then you may be left with a Fastrack G99 ie agreeing to limit export to 3.68kw or a G98 only. My reading of the Fastrack G99 is that you need to have two 3.68Kw inverters not 1 at 7.2kw but these do seem to be approved by some DNO's under the fastrack G99 so worth asking.

With only 4kw of panels then you need to look at your timing of usage vs production usage vs battery storage to see if its worth over sizing the inverter and then being refused for little real benefit. If like me the peaks are just for a few minutes it is pointless.

 

[RibbonFox]

Our current demand sees regular 5kw sustained load, with burst peaks of 7-8kw but just minutes at a time. This could be load shifted for the most part, but I'm indending on getting an ASHP within the next year or so. Doing that would push the base load up, though I need to research how much it uses normal/peak.

 

[kommando]

But 4kw of panels is not going to make much to start with, so you need to check not just peaks but also overall 24 hr usage.

I have 8kw of panels feeding 7kw of inverters and can only be self sufficient for 7 months of the year, with 4kw of panels I would only cover usage for 2 or 3 months.

Check what your 4kw of panels will produce from this site

JRC Photovoltaic Geographical Information System (PVGIS) - European Commission

Photovoltaic Geographical Information System (PVGIS)

re.jrc.ec.europa.eu

It uses historic sun emission data based on your location, angles of panels etc.

 

[RibbonFox]

I already have - it's an awesome resource ?

4kw is the max panels I can fit on the property right now, so the plan is fill batteries with cheap (7p/kw) electric overnight, then use over the day. Currently we use ~12kwh per day.

 

[kommando]

So look at those short peaks and see what the cost is over the self sufficient months then compare to the cost difference between a 3.6kw and 8kw inverter plus any opportunity costs of not being able to proceed until DNO agreement for G99/G100.

 

[SeaGal]

Few thoughts...

a) re DIY... electrical work in UK will need to be done to IET BS 7671 standards by a competent person. You will also need to meet building regulations part P compliance, which means some work, such as installing a new circuit will require a sparky to install or a friendly sparky to sign DIY work off.

b)

Our current demand sees regular 5kw sustained load, with burst peaks of 7-8kw but just minutes at a time. This could be load shifted for the most part, but I'm indending on getting an ASHP within the next year or so. Doing that would push the base load up, though I need to research how much it uses normal/peak.

I already have - it's an awesome resource ?

4kw is the max panels I can fit on the property right now, so the plan is fill batteries with cheap (7p/kw) electric overnight, then use over the day. Currently we use ~12kwh per day.

Not sure how a 5kW sustained load matches 12kWh / day? 12kWh sounds too low an estimate

But either way, you will need an inverter that can handle those loads from its battery power - be aware that battery supplied power may be less than the headline rating of the inverter. You will also need batteries capable of supply of over 150A to provide 8000W of output power. And enough time to charge them up fully.

Interesting. Does this blow my ideal system above?

Re your concern... not really - all it means is you need to get approval from your DNO via a G99 application before installation. If you propose using an 8kW Sunsynk, the DNO may limit your export power ability to less than the 8kW that the Sunsynk can provide - but - that is only the limit you export to the grid, not a limit of the size of the inverter (so you will still be able to power 7 to 8 kW within your house).

FYI; You are guaranteed to be able to export up to 3.6kW anyway, but depending on your local lines and other connected systems near you, you may need to configure the Sunsynk to use its G100 compliant grid-export limit feature.

 

[RibbonFox]

This is all really helpful, thank you.

Honestly, I'm not interested in exporting anything: Without this being fully designed/supplied/installed by an MCS approved installer, non of the energy companies will pay for the energy they receive from me. The cost of doing that is double the DIY route, so there's no ROI.

Not sure how a 5kW sustained load matches 12kWh / day? 12kWh sounds too low an estimate

5kw, for 10-30 mins isn't uncommon for me when I'm averaging 12kwh in a day. Do you think I'm missing/overlooking something?

As an example, here's a snapshot of my consumption from yesterday. There's ~30mins 4:30-5ish that sits above 5kw. Overall, the daily consumption is higher than the average 12kwh, but it's due to the washing machine/dryer was used a lot in the evening.

If you propose using an 8kW Sunsynk, the DNO may limit your export power ability to less than the 8kW that the Sunsynk can provide - but - that is only the limit you export to the grid, not a limit of the size of the inverter (so you will still be able to power 7 to 8 kW within your house).

Ideally, that's what I'd prefer ? ! I just want to consume all the energy I generate or buy off peak, rather than 50% of the energy come from a battery, and the rest from the grid, under heavy load at peak £ times.

You will also need to meet building regulations part P compliance, which means some work, such as installing a new circuit will require a sparky to install or a friendly sparky to sign DIY work off.

I have a good friend that's a Sparky, and (thankfully) I'm able to cash in a favour.

You will also need batteries capable of supply of over 150A to provide 8000W of output power

The plan is for 2x batteries that are capable of 100A continuous discharge, 200A burst, so I've assumed it should cover this? I've changed plans on the battery type a few times due to the ratio of storage density/throughput/cost. These seem to be the best I can currently lay my hands on. the first I looked at had great storage at a lower cost, but discharge was only 1.2kw, so most appliance would also draw from the grid too.

 

[SeaGal]

All sounds good... time to get your G99 application in to your DNO then

The comment about 12kWh was me interpreting 'sustained' as 'most-of-the-time', not just the 30 mins you've clearly monitored.

FYI, Octopus have recently announced they won't need MCS certification for export but, as you say, that's not your main concern. See...

Octopus Energy will no longer require MCS certification in the UK

https://gtec.co.uk/clause-5-8-octopus-opens-up-the-solar-pv-market-with-a-paragraph/ I'm not sure how exactly the UK's permitting and approval process works but this sounds like a major win for DIY.

diysolarforum.com

 

[RibbonFox]

All sounds good... time to get your G99 application in to your DNO then

? a job for this evening then

I did hear about that announcement, so emailed Octopus. They responded to say "..no..". It's interesting reading some of the content as some people have called it out to be a trial. I'll keep my ears open, to see how it develops given that I'm an Octopus customer, I may make manage to eventually recoup a few pence per year ?

 

[RibbonFox]

not just the 30 mins you've clearly monitored

I'm a lover of data. I picked up a Hildebrand Glow, so that I could connect my smart meter and output my electricity & gas usage real-time to home assistant via MQTT. It's borderline embarrassing how much happiness it's given me.

 

[Rickster1978]

? a job for this evening then

I did hear about that announcement, so emailed Octopus. They responded to say "..no..". It's interesting reading some of the content as some people have called it out to be a trial. I'll keep my ears open, to see how it develops given that I'm an Octopus customer, I may make manage to eventually recoup a few pence per year ?

Did you get your G99 application over to your dno? I’m just trying to work out if I can go down the G98 route with export limited to 3.68kwh. I don’t plan to export anything at all so not worried about it being limited.

 

[SeaGal]

Did you get your G99 application over to your dno? I’m just trying to work out if I can go down the G98 route with export limited to 3.68kwh. I don’t plan to export anything at all so not worried about it being limited.

No (to your question in bold).

The choice of G98 or G99 is determined by the maximum capacity of the inverter - in your case, your 5.5kW Sunsynk. You will need to apply for G99 approval. I got a response back within a week.

 

[dukeminster]

I'm a lover of data. I picked up a Hildebrand Glow, so that I could connect my smart meter and output my electricity & gas usage real-time to home assistant via MQTT. It's borderline embarrassing how much happiness it's given me.

Thanks for sharing, been looking for a product like this for soooo long.

 

[rpdom]

Thanks for sharing, been looking for a product like this for soooo long.

I looked at the Glow and was tempted. But then Octopus offered me their Home Mini. It won't give me accessible data yet, but MQTT access is something they are working on. At present I have to use their app to get the figures. There is an add-on for HA that can get the real-time usage figures that it sends to their server though.