Dillsue

Just looking at your figures, youre listing a 5kw SE inverter, a Victron 5.5kw charger and the 4kw existing system which totals up 14.5kw of potential export. Thats a fair bit of export to get approved so might be worth having an informal chat with your DNO to see what they think before you submit the G99??

Thats for 3 phase systems to declare there wont be more than 16A per phase difference in export on each phase

Other manufacturers may have different settings but the UK spec SE inverters we have are set to shutdown at 262v Yep spreading the array round will help but I guess a battery bank is going to put a fair load on the PV which should keep things in check. On an SE inverter there is supposed to be a power control feature that you can use to throttle production as voltage rises and so keep household voltage sensible. Im waiting to hear from SE as to where in the menu it is as Ive not been able to find it despite installing the latest software!!

Should be on the inverter spec sheet but 1 is likely to be accepted.

I think shutdown voltage is a fair bit higher than the UK max of 253v....262v? Our supply is at 250v and our existing PV pushes us over 253v on a sunny day, but inverter keeps churning out the kw.

With an SE Storedge system theres a CT on the grid connection so the charge controller knows if theres generation going to export and then diverts excess to battery charging. As far as I know any decent PV charge controller would need a CT to govern whether to charge or not?? The G99 need for installer details is a stupid requirement! Until you get your G99 approved you dont know what youll be installing... if approval needs an export limitation system with a commissioning demonstration thats likely a specialist system outside the abilities of your local part P spark whose details youve put on the application. I put TBA on our applicatiion and the DNO wouldnt process it. I then told them I was installing myself with a test and inspection carried out by our local Building Control department...that was accepted.

If youre happy with the SE system you have, Id be looking to install a Storedge system. They can charge from the grid or the AC output of another inverter like your existing FIT system. I think you can connect additional PV to the inverter doing the battery charging but thats worth double checking with SE. If you really want to add PV and storage but your DNO says no or upgrades are prohibitive, you could add export limitation to stay within the 16A limit you already have. With batteries and maybe a PV diverter youll not want to be exporting much anyway. The NW facing roof would help with late afternoon/ teatime production but if youve got batteries youre probably best getting max daytime production on the garage to charge the batteries and draw on the batteries later in the day

With a very large quantity of potentially toxic chemicals stored near me Id be wanting to know all the measures taken to deal with fire, chemical leaks etc. I know very little about battery chemistry but I doubt the contents are something you want drifting in the air or leaching into local ground water.

Outside of peak sunshine months, youll likely to be able to use everything a 12kw array will produce. Year round production is where bigger arrays come into their own. Youll always have an export limit. If you cap export at the 3.68kw G98 limit then you just notify the DNO. If you want to export more than 3.68kw then you need to apply for chargeable permission and that permission would come with an export limit determined by what the local grid can handle or what grid upgrades you want to pay for. How you limit the export is up to you but youll need to convince the DNO that you have an effective limitation system in place. Weve applied for 2 x G98 certified inverters in our G99 application so 2 x 3.68kw. You could have an inverter(s) without a certified limit and add an export limitation system. The export limitation system would need a G100 application in addition to the G99 application. Speak to your local DNO and they may be able to give you an informal indication of what you can connect, ours did and was very helpful.

With panels over a decade old it might be worth checking annual production hasnt dropped to much. With lucrative FIT payments it could be worth renewing the panels if output has dropped.

Is that because the neighbours septic tank runs into it🙈

Adding panels to a FIT accreditted install almost certainly increases the Total Installed Capacity so would need FIT payer approval and MCS install. If its a separate system within the house, then fill your boots, with DNO approval if needed.

As I understand things any alterations on the inverter side of the generation meter are alterations to the FIT accreditted system and risk loosing FIT payments. Any alterations to the consumer unit side of the generation meter and thats part of the house electrics which is nowt to do with the FIT accreditted system.

Having posted on an internet forum the suspicion that the meter may run backwards, Id hazard a guess that knowingly exporting anything through a backward running meter from now on would be fraud????

Or dont install a DC isolator on a SE system with safe shutdown?? Im not saying its the correct thing to do on every system, but on a SE system you remove the chance of a non techy person(householder) doing something detrimental. On a SE system switching off the AC isolator, flicking the on/off switch to off, switching off the inverter MCB, power cut will all shutdown the optimisers and kill the hazardous DC voltage.

Not sure how much space youve got on the east side but you can get 450+ watt panels so not far short of 1kw if you can get two x 2100 x 1050 panels in. Only you know if you can get them in and if its worth the effort. Maybe worth running the 2 panel set up through PVGIS to see how much theyll produce If I was in your place, Id speak to the local planning office and sound them out about panels on the flat roof. If they sound positive I design what you do now assuming that youll be adding to the system in the near(ish) future

3.68kw/16a or less is still notified rather than applied for. Personally Ive not found the G99 process complicated if youre clear on what you want to do. If youre installing a second system with a battery then I beleive you can get SEG if its an MCS install. I think you also have to give up the deemed element of your FIT payments so that all export is metered and paid for via SEG. Youll need a smart meter to do that. If you hoping not to export much then you probably want to have a good think about giving up the FIT deemed payment It wasnt quite clear to me if you were altering your FIT system but I think youre very restricted in what you can do and risk loosing your payments if you fall foul of the scheme rules!

As I understand it Solaredge inverters require a minimum of 8 optimisers so probably not an option anyway unless you go for one of the smaller optimiser integrated systems you mentioned previously. I beleive Solaredge produce a tool that allows you to disable the safe 1volt output feature when comms to the inverter is lost. This allows you to use their optimisers with any inverter so not locked to a Solaredge inverter. Im not suggesting you go for a Solaredge system but my experience of the 2 SE systems we have is nothing but positive....so much so a 3rd SE system is going on my daughters roof in the next few weeks. If youre thinking of changing to landscape orientation on account of the shading from snow, consider how much snow you get in Cambridge, how long the snow persists for and how much generation youll loose for a couple of days of snow cover when your panels are generating next to nothing in the winter anyway

If youre getting FITs the original system will have been MCS installed and met with all the regs. Assuming thats the case youll either have an export limited inverter with a 16 amp export limit, or there would have been a DNO application in 2014 to export more than 16 amp... the predecessor to a G99 application. If youre adding another array and /or AC coupled batteries youll need to put in a G99 application to export(or potentially export) more than the 16 amps?? you already have. If you want to throttle the new array youll need a G100 application aswell to cover the export limitation device/system. All gets complicated above the 3.68kw/16amp limit!!

Exactly as you say, work out loss for each room then add them up. Factor in ventilation/draught loss and thats it done. If you can use MS Excel its very easy to do, otherwise its long hand on paper with a calculator. Using Excel allows you to easily see the impact of changing materials/thickness. A while ago Which produced some very good books on building and this one on Ebay 144467667935 explains the calculation process and gives U values for lots of differing materials in use up to the publication date. If youre planning on using newer insulation youll get U values from the manufacturer online.

If youre looking to expand the system onto your flat roof you probably want to get a bigger inverter or check the inverter linked to can handle the power input you may end up with. My personal preference would be an optimiser per panel so that a single optimser failing doesnt take out to much generation.

With a relatively small PV array, thats probably the best strategy with an easily accessible timer to so can tweak times easily if theres a bright/dull period forecast. Remember that in the winter when you need the HP most youll be generating the least and vice versa in the summer. Nice weather in spring and autumn should see usage vs generation a bit more balanced

That statement is correct but what youre missing is that a bigger power input will be required to drive the larger ASHP.....COP remains the same but power input and power output both increase in the same proportion to maintain the COP. Put the insulation and triple glazing back in and youre back to a 5kw pump still with the same COP but lower power input, lower cost and lower emissions

Google "solamax manual" and you find a comprehensive manual on ST systems including schematic system drawings. No "r" in solamax!

A typical residential punter puts circa 4/5kw on their roof wired to a 3.68kw export limited inverter. All they have to do is fill in a G98 notification form and send it to their DNO. No fees, no drama, easy peasy. As has been mentioned the G98 notification is straight forward to complete. As its a notification and not an application, so long as youve used a G98 compliant inverter they can't stop you having your PV. They may ask for clarification if youve made a mistake but that's the worst that is gonna happen