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Using an inverter as off grid (so no g98/g99g100) with 4 pole changeover contactor - does the DNO need to be involved


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Posted

Hello.

Here is a simple question,  Given that I am limited to 2kw export and  G100 application if I go down the grid tied inverter route.  Is there any legal issue with keeping the inverter purely off grid and using a 4 pole changeover contactor to switch some loads to grid if needed. The inverter would not then be connected to the grid at all. Do I even need to tell the DNO what I am doing? 

I'm only interested in the legal side of things, if we can keep strictly to the question. Whether it is a good idea or not is for a different thread perhaps?

Posted

You need to ask yourself do you need PV, what are you going to use it for. Then does your proposal make any sense?

 

Are you doing battery?

Posted

I was actually asking if bypassing the whole G100 limitation, and the costs involved, by keeping the inverter off grid is a good idea. I am installing 10.2k of solar and planning on as much battery storage as I can afford. To me, being able to choose whether to run things like the cooker, immersion, heat pump off the grid or off battery/solar gives me more choice. 4 pole contactors seem fairly cheap in the grand scheme of things, and easy to control. But the main thing is my pathetic G100 export limit. If I can avoid jumping through that hoop that is a win for me. 

I assume I don't even need to mention anything to the DNO? 

Posted

you would need more than just one changeover switch.

 

In the summer much of what you use could be supplied by off grid PV and battery, but in winter at times little more than the lighting could work from the solar and battery.

 

A lot of appliances e.g almost anything with a time clock, computers etc won't like the brown out each time you change over.

Posted
9 hours ago, jimseng said:

I was actually asking if bypassing the whole G100 limitation, and the costs involved, by keeping the inverter off grid is a good idea. I am installing 10.2k of solar and planning on as much battery storage as I can afford. To me, being able to choose whether to run things like the cooker, immersion, heat pump off the grid or off battery/solar gives me more choice. 4 pole contactors seem fairly cheap in the grand scheme of things, and easy to control. But the main thing is my pathetic G100 export limit. If I can avoid jumping through that hoop that is a win for me. 

I assume I don't even need to mention anything to the DNO? 

What would you do if you had the G98/3.68kw export limit?? If that would make a difference to your plans then throw in a secondhand G98 inverter, get the DNO to make any mods needed to accommodate that and you've upped your export limit

Posted

Why not just get an inverter that will allow you to generate and use the full extent of your solar array, but only export the small amount that is allowed. 
 

Make sure you have enough battery storage to keep you going for at least 24 hours with no generation and don’t wildly oversize the array if you can’t export much as it’ll only be of any (limited) use in the winter/low sun days. 

Posted
2 hours ago, Mattg4321 said:

Why not just get an inverter that will allow you to generate and use the full extent of your solar array, but only export the small amount that is allowed. 

I have been struggling to find one that suits my battery choice. I have been on the ENA database and for some reason I am having difficulty. I don't know if I am using the wrong search terms. I found a Growatt that seemed like a good fit but I can't track down a G100 certificate and the Growatt UK distributor neither answers the phone or responds to emails so far. It is proving harder than I thought it would be. It seems the G100 part of manufacturers literature is a low priority so they don't advertise it much.

Posted

I would look to keep this all simple.

 

Something like a Sunsynk hybrid inverter, set export to zero. The inverter will allow to charge battery from grid and or PV. Inverter will feed house when there is battery capacity and or PV, otherwise draw from grid.

 

This way you give nothing to the grid, but can charge from grid when no PV. Use a time of use tariff get all your electric on cheap rate or from PV.

Posted

I’ve actually got a Sunsynk. 5.5 I think it is. No complaints after a year. &nbsp
 

I’ve wired it to run some circuits in island mode when power goes out too

Posted

I'm trying to work out why you don't just get a hybrid inverter with the ability to export limit? Eg FoxESS, SolaX, Sigenstor etc.

 

As I understand it the DNO has to allow you 3.7kw export and, if the infrastructure isn't up to it, upgrade it at their cost. 

 

(my DNO has been monkeying about with the local transformers to resolve a high voltage issue I've had) 

 

I believe some of the brands can use other battery brands if you are concerned about battery "lock in"  -there's a guy out there running scrapped Tesla batteries from his setup (a fox inverter I think) and someone else has been using leaf batteries for the same. 

 

 

Posted
16 minutes ago, Beelbeebub said:

I'm trying to work out why you don't just get a hybrid inverter with the ability to export limit? Eg FoxESS, SolaX, Sigenstor etc.

 

You're right. There reason I asked the question is, first, I was feeling grumpy at the notion that we are supposed to be moving towards net zero and yet [insert political point about Britain, privatisation, consumers trying their hardest to do their bit by investing in energy efficient homes and still having to contribute their own limited finances towards the under invested national infrastructure], so I was thinking about ways round it. And the second is that actually, it is quite hard to find a hybrid inverter that ticks the G100 box and is compatible with  52v batteries (for instance, the three you mention above are all incompatible). I had struggled for a while to find anything that fitted my criteria (cross referencing the ENA database with datasheets can be a bit bewildering for a newbie like me). But I think I have found two candidates now, A Growatt and Sunsynk. I think I am favouring the Sunsynk at the moment simply due to the AC passthrough current, but they are a little bit more expensive. 

 

Quote

As I understand it the DNO has to allow you 3.7kw export and, if the infrastructure isn't up to it, upgrade it at their cost. 

I did ask the DNO how the 2k limit fitted in with a G98 application. His response was:

"The rules get a little complicated you are correct under G98 you can install up to 3.68kW per phase on a fit and inform basis, once you get into G99 things change NGED can restrict exportation to limits that don’t have an adverse effect to the network so effectively the 3.68kW rules does not necessarily apply."

Part of me wants to do a G98 application and see if they are forced to upgrade. I am actually writing a letter of grumpiness to Ed Milliband, but I doubt he'll even read it.

Posted
37 minutes ago, jimseng said:

G98 application

G98 is a notification, you do after the event, you are just telling them it has happened. There is zero option for them to say no.

Posted

Are you installing with MCS certification? 
If you are self installing outside of MCS then it’s not guaranteed you will get any return on the energy you export, so it makes any restriction less of an issue.

 

 

 

Posted (edited)

SunSynk 3.6kW AC ECCO, has a 7000W MPPT and a rated AC output of 3.68kW and is G98 approved. So no need to tick the G100 box, you have the G98 box ticked instead.

 

Solar Input - 3.6kW Ecco Hybrid Inverter
Max power input – 7000W
Max DC input – 500V
Max current input - 2 x 13A
MPPTS - 2
MPPT range - 150~425V

47 minutes ago, jimseng said:

And the second is that actually, it is quite hard to find a hybrid inverter that ticks the G100 box

 

Edited by JohnMo
  • Like 1
Posted (edited)

Another option is

Sunsynk LifeLynk X - 3.6kW hybrid inverter, 3.6kWh LiFePO4 battery & 4.5kW MPPT - SM3.6KWLL - G98 Approved

 

These are AC coupled inverter battery with PV input. The can be run in parallel configuration with one acting as master and others as slaves. So you can run any number of these and should keep the G98 certification. Each inverter battery will take 4500W PV input.

 

So for around £3k (+VAT) you get 10.8kWh battery storage and more than enough inverter capacity for you PV etc.

Edited by JohnMo
Posted
19 minutes ago, JohnMo said:

Another option is

Sunsynk LifeLynk X - 3.6kW hybrid inverter, 3.6kWh LiFePO4 battery & 4.5kW MPPT - SM3.6KWLL - G98 Approved

 

These are AC coupled inverter battery with PV input. The can be run in parallel configuration with one acting as master and others as slaves. So you can run any number of these and should keep the G98 certification. Each inverter battery will take 4500W PV input.

With more than 1 G98 device wouldn't you have moved into G99/G100 territory with the master inverter doing the G100 management??

Posted (edited)
16 minutes ago, Dillsue said:

With more than 1 G98 device wouldn't you have moved into G99/G100 territory with the master inverter doing the G100 management??

That is a question I have mused over. Passing the ac output of the G98 device to the ac input of a slave device set to zero export. Or a generator input. But in order to live with the system, a high ac passthrough is important to me. I don't want to split my loads into on and off grid if I can help it. That is why I am looking at a 10kw system for an all electric house. 3.6kw isn't enough for my long term ambitions.

I should add that grid export is not relevant to me as it is a a self install. Off peak battery charging and lots of battery capacity is important. 

Edited by jimseng
Posted
6 minutes ago, jimseng said:

should add that grid export is not relevant to me as it is a a self install.

I thought that for a long time, after doing a self installation. But in the ended paid out £250 to octopus to get paid for export. No off set my bills with export payments. You will be surprised by how much slips to the grid even with active management to prevent it.

Posted
21 minutes ago, Dillsue said:

With more than 1 G98 device wouldn't you have moved into G99/G100 territory with the master inverter doing the G100 management?

Not exactly sure, but you cannot have a G98 approved inverter that does G100 management - can you? If it's G98, it's G98, not something else as well. Otherwise it's a G99/G100?

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