Dillsue

Early and late generation may not be so important if you've got batteries. Certainly in the winter you want as much generation while the sun is up to charge your batteries and there won't be much generation coming from an east/west array

I'd persevere with Octopus as they are only obliged to pay you SEG at circa 6p/ unit. The 15p Octopus Outgoing is their choice to pay it/not pay it and I'd be surprised if the Ombudsman can do anything other than insist they pay SEG rates

Have you asked your DNO if you can have either or both options?

If you don't want to go the temporary G98 route and you think your loosing a significant amount of export income, then you could add more battery capacity to capture any daytime excess and then export a steady 2kw when the sun goes down.

SPEN previously said- In cases such as yours where the earth loop impedance is relatively high (0.41 Ohms), putting 3.68kW in would cause a problem and it would be wrong of us to to knowingly do this. If you go for G98/3.68kw then it's hard to see SPEN doing nothing after youve sent in your G98 notification. Once they've remedied the problem then there shouldn't be a problem getting 3.68kw export via a G99. If you don't think any of the problems will happen then put in a 3.68 G98 inverter and get a qualified spark to test/witness there's no problems and let SPEN know the sparks findings. What's the issue with a 2kw limit?? Once you've charged your battery you may not actually have that much over 2kw to export for much of the year. If you're concerned about export payments then you may not be loosing out on too many £s over the year.

Seems to me your installer has been negligent in not advising you of the correct process. They've also broken the national rules by connecting to the grid without consent. I'd be looking for them to fit a G98 inverter for you FOC. If they are members of any trade bodies you probably want to make a complaint. Once you've got a G98 inverter fitted, if the DNO decide to do reinforcement works to handle your 3.6kw export, then once those works are done you can reapply for G99 with a 3.6kw G100 export limit. Shouldn't be any reinforcement cost for you

Are you sure about the building control approval? Using a part P spark dispenses with the need for the householder(Octopus customer) to get involved with BC, so why would Octopus ask for BC approval in respect of electrical works? The part P spark issues the installation cert so no BC involvement for the customer. As you're adding load to the roof you'd need BC approval for that, or an exemption process similar to using a part P spark. I beleive the MCS process involves structural assessment of the roof and negates the need for BC approval. If you go the non MCS route, who verifies the adequacy of the roof if its not BC approval??

If no one put a G99 application in and you've installed more than 3.68kw export capability then you probably want to take it up with your installer who should have done the application or advised you to do it. They shouldn't have connected without G99 approval. If they're a reputable outfit, take it up with them. If you or your installer have bypassed the proper process, then SSE are likely justified in their approach?? If you've got an 8kw system and your neighbours have a 20kw system, how do you know that network reinforcements aren't necessary?? If the original supply wasn't designed for 30kw+ of export then it may well need some tweaks(30kw+= 8+20+potential 3.68 from the 3rd property) If you go for a 3.68kw export limited system then you can use everything your system will produce, but just not export it all. As a professional and maybe reputable installer, if they've got you into this mess then ask them to sort out the export limitation. The system is well thought out and full of common sense!!

12 years ago there wasn't so many variants of manufacturer/panel compared to today. Im not saying its not out there but it would be a tall order to capture all of today's panels in one doc.

If you've got 150mm of high performance PIR insulating the room from the ground, why would anyone think half inch or so of cheapo pipe insulation would be good enough to insulate the HP flow and return from the ground. You wouldn't accept water slowly dripping from a pipe so there's no reason to accept heat slowly "dripping" from the pipes.

OK. The Rothenburger pump is quite a fancy bit of kit......compared to the garden sprayer I used. There's a user manual online that tells you how to use it.

Heres how I did our evac tube system. Put up access scaffold Cover panels/tubes with dark tarpaulin Open drain at the bottom to vent pressure Open vent on the roof to allow draining Once flow and return have drained, close drain and vent Refill with water Circulate water for an hour or so. Drain as above If fitted, check accumulator is still pressurised on gas side. Pump up with bike pump if needed Refill with solar fluid til it comes out of vent on roof. Circulate for an hour or so. Top up til fluid comes out of vent on roof Remove fill pump and seal up system Repressurise from mains Circulate for another hour or so. Vent any air out of roof vent and top up pressure if needed Remove tarpaulin Watch system work exactly as it did before, after a mornings work!!!

Depending on your roof covering, if you are wanting to install near to a ridge or gable verge, remember that the closer you go to the ridge to mount roof hooks to more disturbance you'll cause to any bedded tiles, if that's your build up. I stayed far enough away from our ridge/ verge to not disturb any mortar bedding and that was 4-500mm away

Did you do a G99 before you connected?? If you did then they would(should) have told you any costs to connect. If you didn't, then you've probably got to go with what they say???

From the doc linked to- "The incidence of fires involving PV systems is very low" so probably worth keeping things in perspective relative to other hazardous things in your house/life. AFAIK the majority of PV related fires are down to cable connections where cables haven't been terminated correctly so make sure things are tightened up and crimped correctly. Make sure MC4 connectors are crimped with the right size crimper for the cable size but that's down to whoever is doing the crimping. If there's cage clamp terminals in your inverter don't use crimps on the ends of stranded cable as cage clamps are intended to flatten the strands to get the biggest contact area.

If you've got/getting batteries then orientating panels for evening generation may not be necessary if you can orientate them for daytime generation where total generation will be higher, assuming your batteries can soak up all thats generated. Obviously if you've not got the spare space for optimum daytime orientation then put them where you can

You can have significantly more than that. If you stick within the G98 limit of 3,68kw inverter rating, then you can get inverters that allow 200% oversizing on the DC input so you can have 7.3kw of panels. If your panels are facing differing directions then you can have more still subject to sticking within the inverters max input limits. Panels are cheap and maxing your array gives useful generation year round.

Without knowing pipe diameter it's hard to comment on the insulation but personally I'd be wanting 25/32mm wall thickness to minimise heat loss and maximise frost protection. If you use 32mm wall thickness some of the insulation can be cut out of the inside to allow the insulation to fit over the nuts on compression fittings so you have some insulation over everything. Ideally the majority of insulation is unsplit so it gets slipped over the end of the pipework and there's way less gaps to worry about. Formed long radius bends allow the likes of Armaflex insulation to fit neatly over the bends without joins, and reduce flow resistance as a bonus.

Insulation looks like indoor wall thickness to me. The OD of standard outdoor stuff is way thicker than a compression fitting so It looks to me like it's thin indoor stuff they have used. For heated pipework that's going to spend many weeks of the year in single fugure air temps you need thick walls, no open joints and all fittings covered.

Yep and building control sign off and part P sign off. I reckon a grand all in

I asked Octopus before even applying for Outgoing and after a few weeks back and forth they said no, but may do in the future. They are trialling accepting non MCS export but theres a few hoops to jump through to get accepted. I applied for Outgoing 6 months later at the end of last year and supplied only details of our 4kw MCS system thinking I could sneak in the non MCS generation..... they haven't processed the application! Not sure why as they've not been in touch but I'm collating export figures to see if its really worth giving up our FIT deemed export before I chase them up

I'd be cautious about assuming Octopus will accept your export where there's a mix of generation from MCS and non MCS systems- they told me they wouldn't accept ours! IF the red bit on your graph is the actual clipped bit then you need to work out how many kwh that equates to then multiply by the number of days you realistically think clipping will happen multiplied by your unit import rate. You'll then see how much you'll likely loose and how that compares to the the cost of adding a second system. As PVGIS is based on historical figures you'd likely be more accurate using its prediction rather than as8ngle day snap shot from a few days ago??

If there's installation constraints to hooking up extra panels to the existing inverter then only you can weigh those up versus a G99 application, part P sign off and cost of a second inverter. We have a ground mounted 3kw array which is hooked up via a buried SWA cable which is straight forward to install to the inverter inside the garage. For the clipping, assuming you've not got batteries, do you need more/can you use more during a summers day than 3.68kw for the few weeks a year that you'd likely be clipping? With split arrays you can get a combined generation forecast from PVGIS by downloading hourly forecasts for each array and summing them in a spread sheet to see what the peak generation for each hour is. You can then see how many hours/days you'd be clipping in reality. Our second system has 8.5kw of panels spread between SE and NW to give day round generation and peak generation is 5.2kw. The 5.2kw forecast rarely happens and its probably even rarer for us to use the peak for the relatively short time it's there.

Just had a look at the spec for your inverter and it allows 200% oversizing on the DC input so theoretically you can hook up all your panels to the existing inverter so no DNO involvement and extended generation through the day. I didn't see if there was a max limit on each MPPT input so check with manufacturer if you can put 4kw on one and 3.2 on the other.

Keep things straight with your DNO as it helps manage the grid for everyone's benefit. No need for MCS. The OFGEM guidance for FIT payers requires them to actively monitor for unexpected over generation. You're not gonna be getting FIT payments but Octopus should already have mechanisms in place for monitoring unexpected FIT Generation so whether they apply those mechanisms to other export schemes is anyone's guess. Even if the did detect over generation they might not be bothered if youre not on a government regulated export scheme(FIT/SEG)?? The risk you run is they pull the plug on your outgoing payments. How big that risk is is anyone's guess!