Dillsue

Just listening to the prophets of doom citing death as close to inevitable when connecting PV modules got me thinking of what seems a more realistic situation??? OP has 2 strings of 6 panels wired into separate isolators so max voltage on either string is around 6x40vdc=240v. That 240v will be contained within a pre wired isolator. The pre wiring has an IP2x MC4 connector on the end of whats probably double insulated cable. Panels are new almost certainly having a factory QA inspection for function and integrity. Remembering that the isolators arent connected to anything yet and are in the off position, theres no circuit that can carry any current so youre not connecting any load. When you plug the first panel in youre handling MC4 connectors with circa 40 volts across them inside IP2x connectors, IF you held both plugs at once, which you dont when connecting up When you connect the second panel to the first theres no voltage across the plugs as both panels arent referenced to earth or to each other. The same principle applies as you plug in subsequent panels. When you connect the last panel to the isolator cable, theres now 240v inside the isolator but as the array isnt tied to earth, youve got to touch both +ve and -ve at the same time to get a belt, after youve taken the cover off the isolator. Maybe Im missing something but it seems pretty benign to me???

Switch the AC isolator off and the inverter should shut down, then which terminals remain live with the isolator cover off?

What is important is that you get the live conductors in L1-3 and not in T1-3. L = Line which is the incoming live supply. Unless the interlock has been defeated, you can only remove the isolator cover in the off position. In the off position the only live terminals should be L1-3 so your incoming cables from the PV array would be in L1 and either L2 or N depending on where you want to put the incoming -ve. Unfortunately the same principle applies to the AC isolator!!

G98 allows the system you describe, in fact it allows up to 16amp export on top of what you pump into the battery. Its the householders choice if they want to use kit that doesnt meet G98. If your choice of kit doesnt meet G98 but is configured for zero export then youll get permission to connect, but youll need to prove to the DNO it is actually limited to zero.

Those following the advice given on page 2 of this thread, hence the discussion!!

For any particular section of the grid, say a large housing estate, the sun shines at the same time, save for the odd passing cloud on a sunny day. I dont think voltage rise nationally is problem as large generators can probably regulate that. The issue is if there was unregulated install of PV or no requirement to notify the DNO, then said section of the grid/housing estate could have problems

Not everyone cooks at the same time and even if they did not every element on every cooker would be on at the same time. Conversly, when the sun shines everyones PV will export at exactly the same time. Volt rise can be an issue....our house voltage rises to 255 when the sun shines with a single G98 system. If I connect up a second G98 system (for test purposes), one or other of the inverters will trip on grid overvoltage which is set at 262 volts. Grid limit is 253 volt. Hopefully, that will be resolved when our DNO upgrades our transformer, but you can hopelly see that uncontrolled connection of PV can easily lead to problems.

AIUI any cable assembly that is factory made and tested can be installed by anyone ie kettle or computer lead. That principle would cover all the panel MC4 connectors connecting the panels together If the cables from the array to the inverter are prefabricated then the same principle applies. If the same cables are site assembled, as in cut to length and MC4 connectors crimped on, then they need a test and inspection. Unless youve got an inverter and consumer unit with plug in connectors and can buy a factory assembled and tested connecting lead, then the AC connection from inverter to CU always needs a test and inspection. Just my take on things and not a statement of fact!!

And immediately following that para it refers the reader to the MCS web site, yet theres absolutely no requirement to use MCS installers which the para infers is a requirement! As with the addition of any circuit to a domestic install, a new PV connection needs to be tested and inspected by a part P accreditted spark or get your local building control to test and inspect.

I think theres a national concession to allow export up to 16amps, but part of that concession is to let your DNO know that you are able to export, via a G98 notification.......quite a reasonable arrangement and its beyond me why some people seem so averse to doing so

Thats not a correct comparison . We all cook at different times and individual cooker rings in all households will fire at differeing times giving a low diversified import load. If all households on a section of grid installed 16amp of PV export then first sunny day they will all export at exactly the same time and the local voltage could rocket. If the DNOs know in advance that those households have PV they can manage the grid in a timely way. I dont know if current PV install levels are unprecedented but they are certainly high and keeping your DNO informed about what youre doing can only help them keep abreast of things

Yes. For all the reasons others have stated and so the DNO can keep tabs on how much generation is connected to each section of the grid. If everyone connects 16amp of PV generation, its gonna get interesting on a sunny summers day. By everyone telling the DNO what theyve installed to DNO can manage the potential summer peak of generation.

Dont forget to notify your DNO with a G98 notification form

PVGIS

But youll import from the grid if theres demand from the house whilst ALL output is going to the immersion??

Isnt that what your diverter does now? Diverts excess PV to the immersion and when the stat cuts out all PV goes to the house and then to the grid if the house doesnt use it??

Ours was at SP Manweb. I emailed their contact for our area and they phoned back the next day having already looked at our property. We had informal agreement a day or two later so I could plan things from that point. I cant speak highly enough of the service so far. The one fly in the ointment is that all this was way back Feb/March time and they were busy then. I spoke to their engineer last week and he said for every application they send out they get 4 new enquiries come in. Service may have changed now.

If youve gone off grid to avoid DNO approval then you may still need DNO approval for the changeover mechanism to ensure that the off grid PV and batteries dont become on grid when you reconnect to the grid that you dont want to connect to🤔

Same boat as us but you have a more lucrative FIT deal with another 14 years to run so not worth loosing . First off speak to your DNO to see what the chance of upping export is. We had an in principle agreement to double export in a couple of days with formal approval being processed now. Once you know if you can increase export you can plan your next move.

Anyone habitually starting and binning companies every so often is dodging/hiding something whether its paying tax, avoiding warranty calls, inability to run a business, scamming suppliers or customers etc etc. No matter how knowledgeable they are, would you want them doing that to you or part way through your job?? If they take credit cards, pay the deposit on a card so at least youve got section 75 cover

In the sketch you show the vertical adjustment slot for the rail being cut off. If you loose that adjustment your rail has to follow the contour of the roof which could be all over the place. Might be worth running a string line across the roof in a few places to check its flat otherwise you might want to keep the adjustment?? Recently fitted an array to my daughters house and with the outer hooks set lowest and those on the middle of the roof set highest, there was still a sag in the rail. Fortunately it wasnt obvious from the ground but you could still see the sag. Not sure who built the roof but they should have gone to Specsavers!

When you chop the roof hook dont have it resting on the tile but a few mm clear of the tile. The hook transfers the weight of the array plus wind/snow load through to the rafters. If the hook rests on the tile or can flex onto it, all the load goes through the tile with a fair chance the tile will break.

What I call our DHW tank is open vented with 3 separate coils. I suppose thats storing heat so could be called a thermal store but I guess youre talking about a space heating TS??

Even if its a pressuried coil in an open vented cylinder??

And a thin diamond disc. Renusol do a good installation video on utube for PV mounts but the roof hook detail is the same