Dillsue

Not sure that's right. It's not going to happen overnight but if it needs to happen, it will. Take the comments made about plumbers and ASHPs. I know 2 plumbers and they struggle with basic conventional heating system controls using a timer/room stat/zone valves. They've got little chance of being retrained in a field they already struggle with and theres next to no chance of the understanding the workings of a heat pump and associated control system. On top of that they have no chance of fixing a poorly specified system that needs a redesign. What we're going to have to do is wait for a generation of young trainees that cut their teeth on heat pumps and more complex controls to find their way into the market. That's years away but they will get out there in time.

If youre concerned about Perlight, what's stopping you using smaller JA panels.

Alterations are allowable and covered in OFGEMs updated FIT rules https://www.ofgem.gov.uk/publications/feed-tariffs-fit-decision-replacement-generating-equipment

Get a couple of panels or the same size sheets of wood, prop them up one in front of the other and see where the shadows fall at different times of the day. At a guess, 1 metre will be no where near enough to give year round generation from the rear rows. Setting the panels in landscape orientation will allow them to be closer but make the rows longer. If youve got the option to raise the rear rows, that would allow the rows to be closer together PVGIS will give you hourly generation figures so you can see how much an unshaded array should be generating at different times of the day throughout the year. You can then decide when and how much you want to generate and set your panels so there is no shading when youve chase to generate. Unless youve got the rows spaced far enough that theres no shading, It's almost certain that you want the front row on its own MPPT input and the rest of the panels on a separate input(s). Alternatively you can use optimisers or micro inverters which will both help maximise generation when theres some shading.

Probably best to speak to your DNO before you comit to anything to check you can add the extra export.

If youre looking to change to a Lux hybrid inverter, youll not be able to use micro inverters as they produce AC which isnt compatible with the DC PV input of the inverter. If you want to keep the inverter youve got now and use micro inverters for your PV, youll need to speak to your DNO and likely make a G99 application as your total potential output to the grid is over 16amp(3.68kw). One thing I noticed from the photo you posted is that if the West face of your bungalow isnt shaded you can add panels the that bit of the roof as well as the south face.

I'd disagree with you on that. Whoever installed it for you is likely a professional and should have run through options with you. As you wanted an inverter/batteries, fitting PV at a later date is a blindingly obvious thing to do so they should have asked about that. They're at fault, not you.

You should be able to get it circulating by manually venting the system. An auto vent will clear circulating bubbles and stop them accumulating but manual venting will get any big slugs of air out so an auto vent wont be required to get the system running. Is there a non return valve and has it been fitted the right way? Pump is fitted the correct way round? Have you followed the pipework from the filling point and checked theres no closed valves and that flow and return pipework rises from the lowest point to the highest point?

Youre frames look easily adjustable so no plans to change inclination seasonally??

Rock solid then. If youre not used to swinging a sledge hammer, get someone who is to do it!!!

With no bracing shown on the sides Im guessing the vertical tubes get knocked well into the ground??

I genuinely don't understand why you think theres going to be a 50% loss in generation for the new 1.5kwp of panels. Inverter losses are a few % so having a second inverter is going to have negligible impact. Putting half of the new panels on a flat roof will have an impact but not much. Running 1.5kwp of panels through PVGIS gives annual generation of 1376kwh at 35 degrees and 1251kwh at 10 degrees inclination, so a loss of under 10%. OP only has 2 out of 4 panels on a flat roof so under 5% loss. How much shading there is on the OPs 2 flat roof panels we dont know, but we have 3 out of 16 of our panels shaded til lunchtime and our array still generates significantly more than the MCS forecast year on year so the shading cant be too detrimental.

If youve had the system stripped it can take a while to get the slugs of air out of the system. An auto air vent will catch any bubbles circulating and stop them accumulating. I'm not sure what you define as the solar station but you definitely want to be venting the collector on the roof

Interesting stuff. I'd have thought that there would be more than 25% difference between identical shaded and unshaded panels so not sure how Tigo deal with that?? Solaredge dont seem to have the same restriction as you can have 250w and 500w optimisers in the same string. Probably not relevant to the OP unless he's gonna migrate the lot to SE

Why would adding 40% more generation capacity, in the same location, only give a theoretical 40% increase in generation? OP is putting 2 panels on a pitched roof and 2 on a flat roof which may or may not be angled but I dont think that gonna cost him a loss of half his additional generation which youre suggesting at quoting 20%. In terms of 'getting excited" I like people to see the bigger picture, which includes the risks in doing certain things, like breaching the FIT rules, as you suggested. We had our FIT payments suspended a few years ago due wholly to an admin error by our FIT payer, Scottish Power. Despite extensive dialogue with them the payments only got reinstated after 6 months following a formal complaint to OFGEM. If youd breached the rules and had payments suspended I could see that taking a very long time to sort out, based on my experience.

I cant see electricity suppliers not wanting to buy excess renewable generation so I'd be surprised if SEG or a similar system wasnt in place for a good while. If youre making a decision to install kit based on receiving payments its probably prudent to also consider the same project without payments.

Adding 1.5kw to a 4 kw system is around a 40% hike in generation. Factor in the new panels will almost certainly be more efficient that the old 250w panels and that's a blatantly obvious hike in generation. I'm not sure if FIT payers monitor that sort of thing but it would be very easy to do. Youd almost certainly get your FIT payments suspended and possibly loose them entirely for not notifying the system extension. I'm not sure how the FIT scheme is funded but likely we all contribute through eleccy bills/tax, so taking payments youre not entitled to is money out of everyone else's pockets!!

But that's exactly what optimisers are designed to deal with. There's no difference in varying panel outputs from a mix of shaded and unshaded panels compared to a mix of panel sizes/outputs. We have 310 and 320w panels on one string and 335 and 405w panels on a second string. Being able to use differing size panels is an often overlooked feature of optimisers that allow a system to be very easily expanded over time without having to source panels to match originals that may have been obsolete for years. Like the OP our original FIT system uses 250w panels and I doubt Id be able to easily find 250w panels if I wanted to expand that system. Fortunately that system uses optimisers so I can add pretty much whatever panels I want up to the inverters DC input limit😁

Run a beefy SWA as suggested and a run of blue alkethene water pipe with a draw wire in it and you can pull in whatever data cable you/your installer wants.

The 4000tl spec Ive just looked at has max DC input as 4.2kw so quite limited. It also seems to have 2 MPPT inputs so if only one is currently wired you could hang your new panels on the free input. PVGIS will give you hourly data which you can crunch in Excel. Put in all the panels facing the same direction AND inclination as a single array and down load the data for the best FIT generation year youve had. Repeat for the remaining panels grouping them in separate arrays by common direction and inclination. Once you've downloaded all the data put the date, time and kw from each dataset into a new sheet. Add all the kw values to give you total kw for every time period. Then sort the entire sheet by kw total column to see what your likely peak kw DC input is. If its 4.2kw or less then youre good to go, otherwise a bit more thinking. Bear in mind that if your max PVGIS input is close to the inverter limit, then over time you might have problems with changing weather. Despite the fact that panel output is supposed to drop off over time, we've just had our best annual generation since 2015 on our FIT system.... climate change or a one off???

Have a look at the spec for your existing inverter as you may well be able to have way more DC input from panels than the inverter rating. Our older 4kw inverter can accept 5.4kw of panels and our newer 3.68kw inverter can accept 5.7kw of panels. Extending the system rather than adding a second system keeps you within the OFGEM guidance for pro rata payments and no worries about export limitation. If you put a second system in with DIY export limitation, you probably dont want to declare that to Octopus as Id be surprised if they'd accept a casual limitation set up that you could easily remove or alter yourself........unless anyone has done this????

Not sure of your figures but if youve got a PV diverter wouldnt you be better off on deemed export??

The DNO has said the extra panels will be ok so no need to limit export

You were talking about a micro inverter solution so I assume that's what youve already got?? Solaredge optimisers deal with a mix of panel sizes and I assume micro inverters do too but that would be a question for the manufacturers tech support. It's the micro inverters that interact with each other, not the panels, so you can probably use whatever panels you want up to the limits of the micro inverters they are connected to. Plugging in 4 additional micro inverters into an existing loop shouldnt be a problem and if you use factory assembled and tested inverters/cables/plugs then its straight forward to connect up.

The FIT rules have changed and you can alter a FIT system without losing your payments- https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.ofgem.gov.uk/sites/default/files/2021-12/Feed-in%20Tariffs_Guidance%20for%20renewable%20installations_V16.pdf&ved=2ahUKEwi91OP77aT8AhVHTUEAHebpBEoQFnoECBIQAQ&usg=AOvVaw3i84Pu-SO0Ibm-lhEjzfaT