16 amp 230v limit

[matthunt]

Hi guys, as we know the limit under G83 is 16 amps at 230v export, does anyone know if this is capped to export to the grid or limited from the inverter under the regulations? point being if a base load of say 320 watts for instance at a house and the inverter was generating 4.0kw then only 16 amps would be exported to the grid anyway, is this permitted?

 

[TedM]

Strictly the regulations talk about the "source of energy" and not the export. In practice the DNOs are worried about the export level but how they implement this seems to be something that varies from one DNO to another.

At the very least you will have to convince the DNO that the export is capped at 16A, but what evidence they will accept for this varies as well. Some, such as WPD, have generically accepted the EMMA diversion device and are in the process of accepting other similar devices. Others may limit you to 16A generated by the SSEG and will accept nothing else.

It is pretty unlikely that any DNO would simply take your word that the export would be limited, in the absence of an accredited diversion device, unless the output from the inverter was limited to 16A.

 

[sharpener]

if a base load of say 320 watts for instance at a house and the inverter was generating 4.0kw then only 16 amps would be exported to the grid anyway, is this permitted?

IIRC it is the declared net capacity of the inverter (after internal losses), the logic being that its own control system will limit the output to 16A whereas in the scenario you describe there is typically no way of ensuring the net export does not exceed 16A. So I have 2x2kW Steca inverters but setting the installation parameters to "UK" automatically put the G83 spec limit in place.

Interesting that WPD are now accepting the EMMA but if the hot water tank (or other diversionary load) is fully satisfied how does this device limit the current exported? (In my case a bit academic, I can't see WPD accrediting my immersion heater controller as I built it myself.)

 

[TedM]

There has to be a fail-safe dump load always available, such as space heating.

 

[sharpener]

I am surprised they are prepared to buy this argument.

Someone will turn off the heating "because it is summer". Or there will be a thermostat somewhere (to meet the requirement for energy-efficient controls!). Or the heater will have its own internal high temp cut-out to protect against a towel being put over it. Or the fuse will blow or the mcb will trip and not get fixed because it is not part of the normal heating setup.

It would be comparatively easy to deal with this problem if inverters had a way to modulate their output to follow a control signal from an EMMA-like device or net export current sensor. They often have frequency control but this won't work for a grid-connected system. Maybe a common interface like Opentherm will evolve. This would also help with storage systems, because currently you are told to have a charger/inverter which can handle the entire output of the solar inverter (in case the mains fails and the system goes into "island mode"), and this makes the storage system unnecessarily large and expensive.

Ideally I would have a 500W battery inverter to run the lights and TV in the evenings, but it does not meet my wife's investment criteria unless it also has an island capability which can use the solar output during power cuts.

 

[TedM]

The fail-safe I mentioned requires that the inverter is shut-down if the dump load is not available. It is matters like this that makes the DNOs require the use of accredited devices only and with their approval.

 

[sharpener]

Thanks for clearing up that point Ted, it covers not only the device then but also the way it is installed.

 

[matthunt]

IIRC it is the declared net capacity of the inverter (after internal losses), the logic being that its own control system will limit the output to 16A whereas in the scenario you describe there is typically no way of ensuring the net export does not exceed 16A. So I have 2x2kW Steca inverters but setting the installation parameters to "UK" automatically put the G83 spec limit in place.

Interesting that WPD are now accepting the EMMA but if the hot water tank (or other diversionary load) is fully satisfied how does this device limit the current exported? (In my case a bit academic, I can't see WPD accrediting my immersion heater controller as I built it myself.)

ok, so if at the point of common coupling was a device that limited the export to 16amps, could we utilise additional generation ? for example more panels etc, as we all know we don't get anywhere near this usually!

 

[Worcester]

You could, however your FiT rate is dependent upon the TIC of the panels irrespective of inverter output or any other controls..

See other threads for detailed discussion / reasons as to why, it's all covered there.

 

[Gavin A]

Hi guys, as we know the limit under G83 is 16 amps at 230v export, does anyone know if this is capped to export to the grid or limited from the inverter under the regulations? point being if a base load of say 320 watts for instance at a house and the inverter was generating 4.0kw then only 16 amps would be exported to the grid anyway, is this permitted?

hmm, we have one 8.4kWp east west split with around 10kWh daily cycling of battery storage available on a nedap power router, which is restricted to 3.68kW export levels under G83/2.

I'd put it as a grey area, the DNO would generally say no, but if the installer is confident in their competence to ensure that it won't exceed that limit and won't cause an issue, then the installer can opt to certify it as G83 / 16amp limited.

on this install it's on a standalone transformer, and in the last year has never exceeded the 3.68kW limit. I also viewed it as a bit of a test case.

Up here they've got a massive backlog in G59 applications so it takes 45 working days to get an application turned around, which to my mind means that it's better to use a bit of common sense with it than add to their workload.

I have had DNO engineers say they';re not bothered as long as the export level is below 16amps per phase.... and then others say different.