Hi all
Finally a good sunny day, I ended up exporting from mid day, I peaked at 4800W export and was steady on or around there for a long while.
I understand I have G98 which caps my export at 3600W. So… is that cap enforced by my equipment? If so, is it the solaredge inverter or the AC3 where the export is recorded? If the equipment caps it, where does the excess go?
Exported over 12kWh today so far and still not got my export tariff enabled 🙁 but that’s another story…
pacemaker similar position re. export tariff.
Hoping Octopus will compensate me for the free electricity my system is sending them whilst I wait for them to sort it out.
Both the SolarEdge inverter and the AC3 will have their own grid power meter device wired back to them to measure the grid import and export instantaneous power.
They both should be configured with the 3.68 kW export limit, but certainly the SolarEdge should as it is clearly capable of more than 3.68 kW.
Why I say both, is because the AC3 could be set to forced discharge at 3 kW at the same time as the SolarEdge is generating excess for export. If the SolarEdge is not configured correctly then at least the AC3 will automatically back off to reduce the grid export below the 3.68 kW limit.
pacemaker If so, is it the solaredge inverter or the AC3 where the export is recorded?
As @Simon_C said, both inverters should be set to a 3.68kW limit by the installer or relevant manufacturer. When I spoke to Givenergy about the export limit setting on our inverters, they said it would exceed that for short periods as the inverter ramps up and down, but should be less than 3.68kWh each hour.
Tim how does that work then? The solaredge has no CT clamp, so no idea what the home is using or whats left to export … only the GE AC3 is aware of that
pacemaker , what is the rating of the SolarEdge inverter and your solar panels peak power?
It sounds like the SolarEdge installation is not compliant with the G98 allowed limit of 3.68 kW export (single phase), unless it is 3-phase when you can have 11 kW (3.68 per phase).
Simon_C it’s a SE5000, 5kW inverter, 5.6kW panels. My house is single phase.
pacemaker Not sure applies to yours but their webs site states:
"Export Limitation
SolarEdge offers an export limitation option, integrated in the SolarEdge inverter firmware, which dynamically adjusts PV power production. This allows you to use more energy for self-consumption when the loads are high, while maintaining the export limit also when the loads are low."
Maybe you need to check with the installer or manufacturer if the installer isn't known. I assume they can remotely check settings.
Tim SolarEdge offers an export limitation option, integrated in the SolarEdge inverter firmware, which dynamically adjusts PV power production.
I just wonder how the solaredge is even doing that, the inverter is not measuring export or energy usage in the home at all, that is entirely happening through the GE CT Clamp. The only measurement I get through my SE inverter dashboard is solar generation.
As you can see from this page: https://www.solaredge.com/uk/solutions/feed-in-limitation-and-metering-solution
The only thing going into my solaredge inverter is the solar panels. Then AC out to the home.
pacemaker what does the original DNO response to the G99 say? Maybe they agreed at 5kW export limit? If not the installer should have applied some means of limiting the export.
Whose responsibility is it to ensure any "kit" ( PV and battery ) does not exceed the G98 or G99 export limit ?
I have assumed it it the owner of the equipment rather than the installer. I (sort of) get that a responsible installer may ( or may be forced via MCS) to enable some sort of software limit. But the owner ought to be made aware of this, if this is the case.
out of interest does anyone know if and how they are enforced (I mean G98/99 export limits) - what I mean is if whoever is responsible for setting the limit does not do it then how will DNO even know that you are exporting over your limit?
alfwro , I guess if you are being paid for export with a smart meter and 30 minute interval reporting, then your supplier like Octopus could flag it up. They require a copy of the G98/99 document when you apply for export payments, so will have a record of what your limit is and what your metered export is historically.
alfwro As far as I know the DNO could survey your premises. Running gear attached to the grid you do not have dno approval for could lead to fines, having the equipment removed etc. You could also damage the local grid, guess they could bill you for all that repair work too.
THALL I get all that - I was just interested if they are actively checking exports against approved export limits. I bet there is whole bunch of cowboy electricians installing kit without proper paperwork (i.e. I have received all my paperwork day after the install, some people I know had to wait for months for the same)
alfwro My installer said no when I queried my install last October. I was export limited to 3.68kw and the CT clamp needed for the solis inverter to limit it was not available, he was going to add it later. I was getting worried as saw generation higher than 3.68kw and export. But he said unless they do a survey or something breaks they wont know and restricting systems after install is pretty common, as especially as DNO approval takes a while.
THALL as DNO approval takes a while.
G98 can be applied for retrospectively and a Fast Track G99 installation can be commissioned prior to agreement of DNO. However, both G98 and Fast Track G99 have a limit of 16A per inverter. G98 limits output from the premises to 16A whereas G99 Fast Track can be used for multiple inverter installations, but each inverter (along with ones that were already installed) must be a G98 Type Tested one, limiting output to a maximum of 16A each. This means that you could be exporting more than 16A if you had say an old FIT system and a new HY3.6. If the inverter is type tested to G99 (Givenergy HY5), a G99 Fast Track isn't applicable (a full application is required) and it should not be connected to the consumer unit and commissioned until the DNO agreement has been received. If installers choose to ignore this, they are taking a punt and could leave themselves open to sanctions from the DNO.
Roberto Whose responsibility is it to ensure any "kit" ( PV and battery ) does not exceed the G98 or G99 export limit ?
I think the answer to that is the owner of the premises. Most of us buy in the skill and knowledge from competent contractors who we rely on to advise us on what the right thing to do is to keep ourselves compliant with regulations. As they say, "ignorance (of the law) is not a defence".
Tim what does the original DNO response to the G99 say? Maybe they agreed at 5kW export limit?
Finally been able to confirm that my installer filed a G98, with a 3.68kWh limit. I can see on the Octopus side (as my export is finally working) that in some hour spans I am exporting greater than that (3.8kWh is my max so far in last 3 weeks).
I've pinged my installer but not got a response yet (multiple times.. trying again).
If my equipment isn't setup for export max, can they instead apply for an upper limit on the export, to say 5kWh, which is the theoretical max my equipment could ever export?
pacemaker Your installer can do a G99 up to the limit of your inverter.
On a side note does anyone know where a generation system monitors export? Is it per system? I will have 4 generation systems soon with a cap of 8kw but I don't understand how all of the systems monitor and agree who exports when.
THALL Your installer can do a G99 up to the limit of your inverter.
That's good news. Can they retrofit that? Is it just a case of them re-applying?
pacemaker Export limits can be challenged. The DNO can say no however, and there might be a cost involved for your installer to do the admin.
THALL well I guess it's the admin cost or the cost of them coming to fit the right equipment to ensure the export limit is set to the G98. I'll see what they say
pacemaker GivEnergy inverter? They can set it on the engineer portal or GE Support can do it remotely too.
See above for more details, solaredge inverter (no CT clamp so unable to see import/export/usage). AC3 - which can see the import/export/usage through its CT clamp. SE inverter just dumps the AC into the house. There's nothing "connecting" the SE and GE equipment that I can see.
My guess is they need to add some kind of monitoring equipment for the SolarEdge to ramp it down to hit the export limit. Or raise the limit...
If the SE inverter is internally limited to output 3.68kW then this would work with no other generation equipment on site.
Once more than one generator is on-site then an internal output limit won't work.
Not sure if G98 allows for a 5kW inverter to use an internal limit set to 3.68kW without a G100 compliant meter and external CT clamp ?????
The installer may have just limited the SE inverter output and bunged in a G998 declaration (as it is easy).
Worth checking with your installer if any further DNO communications were engaged when the AC3.0 was later installed.
However, if the GE inverter is set up with an export limit then it should back it's output off (with the accepted short term overshoot) if the SolarEdge inverter is exporting so could in theory still limit the site to 3.68Kw export, but pretty sure this should be a G99 Fast Track application.
This is what I keep saying... the SE inverter connected to the panels cannot see the export or home usage. So even if they set an export limit, its useless because the inverter is in ignorant bliss of what its exporting, its just generating.
The AC3 which is connected to the home usage/export etc is not able to "ramp down" (where does the excess go?), only the SE inverter connected to the panels can do that in order to generate less, and as I say above, it has no idea.
pacemaker
If the SolarEdge has no grid CT clamp then you are correct, it can't correctly export limit, all it can do is control it's own output level. It sounds like it's internal limit is set at 3.68kW, but if it is maxed out, any other other generation equipment on site will be added on, the SolarEdge will not know about it.
An internal limit will only work if it is the sole generation source on the site.
This is why additional DNO approval is required if an AC storage battery is added as it can add to the inverter output and go over the G98 3.68kW export limit. A G99 Fast Track + G100 would do this.
The AC3.0 doesn't have excess, it can discharge the battery up to 3kW, but for example if the the AC3.0 has a 3.68kW export limit set and the SolerEdge inverter is generation 2kW + there is 500W of home demand then if the AC3.0 is told to dump at max rate the AC3.0 wind it's output back to 2.18kW to meet the 3.68kW site export limit set (3.68Kw - 2Kw + 0.5kW).
There is no excess to get rid of with the AC3.0
athresuk So based on that, I have 3 pv's and 1 AC3. The AC3 has a meter to monitor grid flow, but each PV will need a ct clamp on the grid line to agree a 8kw export limit. I wish I understood how they negotiate who exports how much.
THALL I wish I understood how they negotiate who exports how much.
They don't negotiate! If there is a means of monitoring grid export (as Givenergy's does), then the individual inverters will output whatever they can get from PV but throttle back when the export limit is reached. Without a means of grid export monitoring, the inverters will output whatever they can harvest from PV which will either be consumed (house load or battery charging) or exported. If your plant has panels facing in different directions (eg W, S, E), the combined output would be limited by nature. If all the panels are the same orientation, output will only be limited by weather and time of year. If the installer commissioned plant that could exceed the DNO agreed limit, then they are outside the agreement.
pacemaker This is what I keep saying... the SE inverter connected to the panels cannot see the export or home usage. So even if they set an export limit, its useless because the inverter is in ignorant bliss of what its exporting, its just generating.
You haven't actually said how much PV you have, or their orientation and the rating of the SE inverter. It's feasible to have >3.68kWp PV installed E or W with a suitably sized inverter because with that orientation, the array is unlikely to exceed the 3.68kWh DNO limit. However, if you have 8kWp S facing and an 8kW SE inverter, the installation could exceed the G98 limit of 3.68kWh. If the inverter output exceeds 3.68kW, it will have been type tested to G99 and the DNO agreement would not have been done under G98. I get that you can't understand how the inverter is free to output whatever it can harvest from the PV array without any monitoring of export, but what is the array size and orientation and the inverter rating/type testing?
Tim I’m already clearly over exporting. Octopus is showing over 3.8kWh per hour as I mentioned above.
Anyway, I have 14 x 405W array into a 5kW inverter. 10 are south facing. 4 are east. Once my battery is charged my house runs at 200Wh. The rest gets exported if there’s enough sun (which there hasn’t been recently). I often see it running at its max but the sun hasn’t been out long enough to sustain it for an hour+
Tim My installer dropped me a voice note and explained a ct clamp will be placed on my 8kw solis inverter monitoring the grid to keep total export at 8kw. The 5kw and 2.5kw arrays will not produce enough to exceed my 8kw limit. Though one of my neighbours just had an 11kw export agreed so I am tempted to try a new DNO application. But as my new install is planned for 9th June I might not bother.
pacemaker From previous posts, it looks like your DNO application was under G98. I think your installer was either naive or pulling a fast one. Your inverter should have a manufacturer's data plate with either G98 or G99 on. At 5kW, it's not going to be G98 type tested, it's going to be G99. If I were you, I'd contact your installer and say that you don't think the paperwork is right for your installation. Did you get copies of the DNO agreement, MCS certificate and Electrical installation inspection from your installer? All of these will be necessary should you wish to apply for SEG or sell the property. If the inverter is capable of limiting its output (as @THALL's is), then the installer can comply with the DNO agreement by installing one, before they retrospectively reapply under G99 with a voluntary limit of 3.68kW, unless you want the limit to be increased. For G98 and fast track G99 (where all microgeneration devices are type tested to G98 and export is limited to 3.68kW), it's usually a formality to get the agreement processed. If your installation does not comply with G98 or G99 fast track, it's a full G99 requiring at least a desktop survey and will incur a cost. Your installer probably made a simple mistake but the paperwork is as important as the actual installation, especially when it comes to selling your property in the future.
THALL a ct clamp will be placed on my 8kw solis inverter monitoring the grid to keep total export at 8kw
Ideal!
THALL I am tempted to try a new DNO application
Why not give the DNO a call and have an informal chat with them? If they're giving away export rights to neighbours, they may for you too; you just need to know whether it's worth spending the £300 or whatever to get it.
Tim Hmm last time there was no charge. I certainly would not pay to have greater export, not worth it. But a phone call only costs time so might do that. If my installer's wife (she does the admin) has time she might do it...... Couple of free options might be worth looking into it. It would only be purely for money making reasons though, greed.
Yes the DNO confirmed G98 and the export cap of 3.68 (they told me "3.60 KW")
I don't have a copy of anything from the DNO other than the approval email from them saying that the application for Solar PV has been approved. This is what I provided Octopus (with the MCS cert) for the approval to then get the export MPAN. The MCS states "Total Installed Capacity (kW): 5.60" though I see no mention of the 5.0kW Solar Edge Inverter on MCS cert.
Unfortunately like many others, my installer is ghosting me as soon as you pay, so finding it really hard to move forwards.
Edit: And like magic my installer replies to another chaser saying they're applying for G99 for me...
pacemaker There was no numbers on the approval email? The last thing I got from my DNO was approval for my last install, a G99 which had 2 lines in it listing export limit of 8kw. Which makes sense, an 8kw inverter was installed. As for the MCS my installer says that is basically for permission to install on your roof rather than an important electrical document. When my 2.4kw PV was expanded last October I did not get a new MCS as it went on the same roof. However the MCS for my 4.6kw pv lists all the kit used, panels, inverter even the mounting system.
My installer is now doing another application for me (£50 admin charge this time) asking for export approval of 13.93kw of PV which is my 3 systems combined, or 15.5kw of inverters not including the battery. But will leave it to them! Leave it in the hands of the experts.
THALL no nothing on their approval email other than a reference number (DNO is UKPN). The limit I got was from another email I sent to the DNO, who confirmed "3.60 KW" limit.
Anyway seems like the installer is now hopefully going to rectify through a G99...
pacemaker my installer replies to another chaser saying they're applying for G99 for me...
Whatever the reason for this sudden awakening, it's got to be good. I had no idea what to expect from my DNO but what I received from them (via eMail) is a 7 page Agreement for Connection to the Distribution System. It's only on page 6 under technical details that the maximum export capacity is stated as 3.68kW and the total capacity is stated as 10kW (two HY5s).