Export limiting option

Hi, can anyone confirm if the gen 1, 5 kW hybrid has export limiting function built in. It looks like my installer has messed up and has installed beyond the DNO limit. Thanks

Jerry2604 Yes, it’s part of type-testing that inverters should be able to limit the output to ensure DNO limits are not exceeded. Your installer can set this remotely for you or you can ask Givenergy to do it for you.

How will the DNO know that you are installing beyond limits and what would it do to the network at a domestic scale.
Appreciate/apologies if you have a massive house/garden and acres of panels and the export is huge
Regards
Steve

SteveCook the whole point of G98/99/100 is that the DNO has opportunity to record the installation at your premises and only agree to the connection of the installation subject to compliance with regulations and them setting an export limit (usually 3.68kW but sometimes higher). If this isn’t done they can disconnect your non-compliant premises, which might suit some; to be off-grid. A competent installer would know all this and ensure that your installation was compliant before they connected and commissioned it.

Tim
Absolutely agree.
All I am saying is how would they know if you set the inverter to one max number and then later reset to export more.
Regards
Steve

SteveCook I agree that it is a relatively trivial act to modify an inverter register to adjust maximum export and contend that is why a competent installer should set It as part of their work. The setting is not available to end users, just manufacturers and installers. There are other ways which are available to end users in which you could pass an excess through your energy supplier meter without it being reduced by a correctly-configured inverter, if you really wanted to. However the DNO doesn't put limits on to prevent you from earning SEG import but to protect the integrity of the local distribution network for everyone connected.

I guess that if you exported at a max of 5kWh rather than 3.68kWh, they might never cotton on but if all of your neighbours also did this, then they'd soon have complaints of over voltage during peak solar and then they'd start looking. You might get away with a 5kWh setting, saying it was a mistake, but for the extra potential income from SEG, I'd say it's not worth it, just plan to maximise the generation by diverting to house battery, hot water, EV, hot tub etc. Nobody knows you're speeding on the road until someone reports you or you're caught by an unexpected camera.

Can the export limitation be dynamic? For example if an old fixed line inverter of 4kW on a FIT is at the same premises with a new 5kW hybrid. If the DNO only agrees 6kW export, can the hybrid be made to ramp down to this 6kW if the export might otherwise go higher?

Jerry2604 Yes. The EM115 CT should ideally be sited between the DNO fuse and the energy meter. If so, the inverter will be limited to whatever is flowing out of that cable irrespective of where the power is coming from.

Tim
Thanks for that Tim. By energy meter you mean the smart meter rather than anything else - generation meter for example. If so and the meter cupboard being a tricky route to the inverter does a wireless ct clamp exist to do the job?

Jerry2604 The connection between EM115 and the inverter is a twisted pair Modbus connection. Many installers use Cat5/6 ethernet cable and just use one of the pairs. If a cable run isn't possible, you can use a wireless LORA connection but that will need a power supply from the consumer unit, which you will need for the EM115 anyway. As long as you don't have a Henley block to skew the meter readings, you could site the CT and EM115 adjacent to the consumer unit rather than between DNO fuse and smart meter.

I think there might be a fly in the ointment. I also have a smart EV charger - a Zappi that adjusts the charge rate to match any outgoing export and effectively make sure there is no export. The Zappi is connected in the incoming mains meter cupboard. Presumably it has a ct measuring "export" in the cupboard to make its adjustments so if another ct was needed to modulate the Hybrid inverter's out put there could be a conflict of priorities.??

Jerry2604 They are separate systems. In ECO mode, the Givenergy EM115 (one per hybrid inverter or one per AC-coupled plant) CT monitors grid import/export and drives the inverter output to reduce energy flow to zero in both directions. If there is surplus PV, the inverter diverts that to charge the battery. If there is insufficient PV, the inverter pulls from battery to meet house load. Only when there is surplus PV and the battery is fully charged does the inverter export (up to the G98/99 maximum set in the inverter) and if the battery is flat, the inverter can't do anything about the grid import, other than measure it.

When your Zappi sees grid export (in ECO+ mode), it diverts the surplus to charge the EV. The minimum charge to EV allowed is 1.4kW, so your export will have to exceed that to start a charge (unless your Minimum Green Level is less than 100%). Our Zappi is set to ECO+ and 100% MGL and a time delay of 20 seconds. Using this setting diverts all surplus PV to charge the EV. From the end of March to the end of October, all the EV charge was from PV.

The two separate systems can work harmoniously and a time delay on the Zappi prevents stop/start on sunny but cloudy/windy days. The 100% MGL setting ensures that the Givenergy battery doesn't empty to EV. Due to the short days and lack of sun, we have been charging the EV overnight (and the Givenergy batteries).

Thanks for that Tim, that is pretty much how my settings are in the Zappi but I have also told it in its settings that it must see a 100W export before it can charge to further ensure the house battery isn't drawn on.
I also have an Eddi.
What I am trying to resolve is how the 5 kW hybrid inverter can be controlled to ramp down if grid export goes above 5kW.
I already have a 4kW line inverter on a 4kW array from 2011. My new array is also kW and has a 5kW hybrid with 16.4kWh of battery.
If say in summer my house battery was full, the EV was full, The hot water was at temperature and the house loads were minimal - such as away on holiday then I want to see how the Hybrid could cut it's output so as not to exceed 5kW to the grid. But it would have to be in such a way that the other energy saving devices get first dibs - ie the Zappi and the Eddi.
The reason I am exploring this is because I believe the installer has not obtained proper approval for my install and he has gone "dark" with no answers to my requests for G99 application copies etc

SteveCook There is an argument that they won't know.
BUT the entire reason for the DNO approval is so that they can ensure that the balance across all 3 phases of the supply from the local sub station is maintained.
From the sub station are 3 individual phases of electricity supply. These are then either split to the houses that sub station supplies on individual phases or sometimes a full 3 phase supply is installed to the properties.
The substation monitors and balances these 3 phases to make sure they stay in balance.
If they go out of balance several things can occur - from minor to major - the efficiency of the electricity supplied by the sub station can drop, this can result in extra heat and losses from the conversion.
The worst case situation is that the substation could actually "blow up" that doesn't mean that there will necessarily be a huge explosion, more likely you kill power to all the properties supplied by that sub station.
Ultimately they will trace that to your property and can disconnect you from the grid or charge you a massive fine.

Jerry2604 If all of your energy consuming/generating devices are connected to one consumer unit (ie no Henley blocks or additional consumer units), then if the Givenergy EM115 CT is situated somewhere between the DNO fuse and the consumer unit, the Givenergy inverter will control the its output to ensure that export does not exceed the value set in its internal register. That value can be set by your installer or by Givenergy themselves.

If you know what your G99 limit is, then (since your installer has gone "dark") ask Givenergy to set the inverter export limit to that value. If you don't know what it is, assume it's 3.68 and you should be on safe ground pending the G99 agreement letter from your DNO. Givenergy respond quickly to web chat available in office hours.

All of the energy from PV will be used by the Givenergy inverter to supply house load (including Eddi and Zappi, so you need to configure them to watch for export) and then its own battery. Only when PV exceeds house load and the battery is fully charged will it then export, adding to the export from the FIT installation.

I think the myEnergi system can monitor AC-coupled output as well as export and so it should be possible to configure the myEnergi devices to divert AC-coupled output to the Eddi, using the Givenergy output for house load and the GE battery charging. If the Zappi was set up as previously mentioned, (ECO+, 100%MGL, time delay and minimum export value), it would only be in the pecking order for energy once the Givenergy battery was fully charged and the Eddi wasn't calling for divert.

Tim I have a copy of a letter from the DNO saying output to the grid is limited to 5kW without any mods required to the grid.
That only gives a 1kW of additional headroom as I already have a 4kW string inverter on the FIT. If the Hybrid 5.0 was adjusted to only 1kW would it therefore be limited to 1kW in all situations?
So if the house had big cooking loads and the car needed charging and I want air-conditioning on etc and the sun was shining it would only provide 1kW?
If all the house loads were combined and for example they were 12kW then in theory the 2 PV systems could meet 9kW of that load with 3kW bought in.
If however the Hy5.0 was capped at 1kW then I would have to buy in 7kW from the grid??
Is that the case or can it ramp up and down to it's maximum but if it sees it going above a 1kw export will cut back?
Thanks

Jerry2604 Just set the inverter max grid export to 5kW. It will Dynamically adjust its own output to limit total export to 5kW irrespective of what the FIT system is doing, as long as the EM115 CT is measuring the energy flow in the grid connection (between any devices and the DNO fuse).

Tim Thanks for the reply. Since this is a feature to limit export rather than the size of the inverter being the limiting factor, would it be subjectvto a G100 rather than a G99? Hoping to get some meaningful discussion going with the installer to find a way forward without involving any agencies or legal if at all possible.

Jerry2604 you’ll see elsewhere that I’ve been having a debate about G98/G99. If you are installing an HY5, you will have to make a G99 application. In the past, my understanding was that if the export was limited to 3.68kW then it could be a fast track application but having read the fast track form, it only applies where total installed capacity is 16-32A and the inverters are G98 type tested (amongst other things). The HY5 is G99 type tested so a full application would need to be made (AFAIK). The issue of G98/99 vs G100 is a timing one as new installations after May 2023 need to be to G100 rather than the older standards but whatever you install will have to be to one of these standards which you will need for your MCS certificate and DNO agreement letter for your SEG tariff (new inverter) and if you ever sell the property.