UK Off-grid DNO advice

[FlakBlag]

Hi all, I'm new here.

I'll soon be installing my first solar system based around a Voltronic off-grid all-in-one inverter/charger. I'm in the UK. This inverter is capable of using grid as a back-up, but not feeding power into the grid. In this configuration I believe the ground/neutral bonding screw in the inverter is removed, and the system relies on the grid for it's earth. The people who sold me the inverter told be I don't need DNO approval for such a system since it doesn't feed back into the grid, but internet searches have returned various differing answers. My question is: do I need DNO approval for my system even though I won't be feeding into the grid? I figure I might since I'll be using the grid earth, and thought it best to ask here

I will say that I have no intention of seeking DNO approval. I will be installing a changeover switch to switch the house between grid and solar anyway. If I can't connect the inverter to the grid without DNO approval then I'll simply run the inverter truly off-grid and switch the house to the grid manually when required, though having the inverter do it automatically would be a useful convenience.

Thanks in advance for any answers.

 

[MichaelK]

I am not in the UK, so could you please explain what "DNO approval" is?

 

[Goboatingnow]

You do not need distribution network operator ( DNO ) permission if your system is below 3.6kwp per phase. However in all cases you are required to inform them within 28 days of any solar infrastructure that is grid tied

If you have battery systems, doing grid feedback , or have islanding facilities you must seek prior approval . Approval can take three months and maybe subject to inspection

 

[FlakBlag]

I am not in the UK, so could you please explain what "DNO approval" is?

The DNO is the "distribution network operator", basically the power company. In the UK you need to get their approval for any electricity generation system that is connected to the grid.

 

[FlakBlag]

You do not need distribution network operator ( DNO ) permission if your system is below 3.6kwp per phase. However in all cases you are required to inform them within 28 days of any solar infrastructure that is grid tied

If you have battery systems, doing grid feedback , or have islanding facilities you must seek prior approval . Approval can take three months and maybe subject to inspection

Thanks for your answer. I'm not sure if my system qualifies as grid-tied.

I have an 8KW inverter. The inverter has a built in transfer switch, it does not feed back into the grid in a conventional sense. If I make use of the grid as a fallback then the inverter does use the grid earth, which is bonded to the neutral where it enters the house. If it's run as a true off-grid system then it has a floating earth.

I have batteries on the DC side. As far as I'm aware only AC coupled battery systems need approval.

There's another thread on this forum that suggests approval is needed, but that's for an inverter that is capable of feeding into the grid, mine isn't.

The salesman said I don't need approval, but I don't trust sales people. I've seen some posts on the internet saying it counts as an appliance and therefore does not need approval. I have seen other things that suggest approval is needed since it is grid connected (even if there's no feed in) and is in effect a permanent island limited to zero export. My electrician told me that installing a crossover switch can evade DNO approval because it ensures the grid and solar are always electrically isolated from each other.

I suspect I need approval to use grid fallback, which is a problem because I don't think the inverter is certified. I think I can get around it by using the manual crossover switch. Next year I hope to double the size of the array, add another inverter in parallel and also add a small wind turbine to help in the dark winter months, this should allow me to go properly off-grid and the problem goes away.

 

[timselectric]

You do not need distribution network operator ( DNO ) permission if your system is below 3.6kwp per phase. However in all cases you are required to inform them within 28 days of any solar infrastructure that is grid tied

If you have battery systems, doing grid feedback , or have islanding facilities you must seek prior approval . Approval can take three months and maybe subject to inspection

Not a grid-tied inverter.

 

[timselectric]

Thanks for your answer. I'm not sure if my system qualifies as grid-tied.

I have an 8KW inverter. The inverter has a built in transfer switch, it does not feed back into the grid in a conventional sense. If I make use of the grid as a fallback then the inverter does use the grid earth, which is bonded to the neutral where it enters the house. If it's run as a true off-grid system then it has a floating earth.

I have batteries on the DC side. As far as I'm aware only AC coupled battery systems need approval.

There's another thread on this forum that suggests approval is needed, but that's for an inverter that is capable of feeding into the grid, mine isn't.

The salesman said I don't need approval, but I don't trust sales people. I've seen some posts on the internet saying it counts as an appliance and therefore does not need approval. I have seen other things that suggest approval is needed since it is grid connected (even if there's no feed in) and is in effect a permanent island limited to zero export. My electrician told me that installing a crossover switch can evade DNO approval because it ensures the grid and solar are always electrically isolated from each other.

I suspect I need approval to use grid fallback, which is a problem because I don't think the inverter is certified. I think I can get around it by using the manual crossover switch. Next year I hope to double the size of the array, add another inverter in parallel and also add a small wind turbine to help in the dark winter months, this should allow me to go properly off-grid and the problem goes away.

Not grid-tied. This inverter is just a load connection. Same as a vacuum cleaner or coffee maker.

 

[FlakBlag]

Not grid-tied. This inverter is just a load connection. Same as a vacuum cleaner or coffee maker.

Thanks. Does that mean I don't need to inform my DNO?

 

[timselectric]

I'm not familiar with your local regulations. But, I don't know why you would have to.

 

[Goboatingnow]

Thanks. Does that mean I don't need to inform my DNO?

You do not

 

[Goboatingnow]

I'm not familiar with your local regulations. But, I don't know why you would have to.

Anything grid tied , yes inform or seek permission

Not grid tied no information need be supplied

 

[Steve Fractals]

Thanks. Does that mean I don't need to inform my DNO?

No because you are not generating power to export back into the grid. You will still be consuming from grid but without any possible export back then it is akin to getting say an electric fire or other consuming type appliance and them expecting you inform them about that.

 

[FlakBlag]

Anything grid tied , yes inform or seek permission

Not grid tied no information need be supplied

That's great, thanks!

 

[Goboatingnow]

No because you are not generating power to export back into the grid. You will still be consuming from grid but without any possible export back then it is akin to getting say an electric fire or other consuming type appliance and them expecting you inform them about that.

In thd uk if you grid tie , irrespective , you must at a minimum inform the DNO, within 28 days.

If you grid tie over 3.6kwp you must seek prior permission

If you grid tie with a battery or islanding ability or feed back you must seek prior permission

The only situation you do not need to inform or seek permission is non grid tied.

 

[Steve Fractals]

In thd uk if you grid tie , irrespective , you must at a minimum inform the DNO, within 28 days.

If you grid tie over 3.6kwp you must seek prior permission

If you grid tie with a battery or islanding ability or feed back you must seek prior permission

The only situation you do not need to inform or seek permission is non grid tied.

His unit isn't grid tied, it's off-grid with grid or generator supply backup

 

[FlakBlag]

Thanks everyone for your input.

I know the DNO regulations are quite strict. I was concerned that by using the grid earth I would need DNO approval. If there was some catastrophic failure of my system (eg. it gets hit by a meteor) I was worried it might be possible to dump a lot of amps to the grid earth, regardless of the fact it's not capable of exporting under normal conditions. The consensus seems to be that the DNO does not need to be informed. I'll double check with my DNO anyway, but I wanted to go into that conversation with more information as off-grid with grid backup is quite an unusual configuration for the UK, the regulations aren't really written with such systems in mind.

 

[Goboatingnow]

His unit isn't grid tied, it's off-grid with grid or generator supply backup

If he has a grid tie backup he needs to inform

Essentially any form of any energy source that could be grid tied most be informed to the DNO.

As I said if there’s no grid tie ( invertor or generator. ) there’s no need to inform.

The whole point is the danger of unintentional feedback of power into the grid.

 

[Goboatingnow]

Thanks everyone for your input.

I know the DNO regulations are quite strict. I was concerned that by using the grid earth I would need DNO approval. If there was some catastrophic failure of my system (eg. it gets hit by a meteor) I was worried it might be possible to dump a lot of amps to the grid earth, regardless of the fact it's not capable of exporting under normal conditions. The consensus seems to be that the DNO does not need to be informed. I'll double check with my DNO anyway, but I wanted to go into that conversation with more information as off-grid with grid backup is quite an unusual configuration for the UK, the regulations aren't really written with such systems in mind.

There is no requirement to inform if using the protective earth

 

[Steve Fractals]

If he has a grid tie backup he needs to inform

Essentially any form of any energy source that could be grid tied most be informed to the DNO.

As I said if there’s no grid tie ( invertor or generator. ) there’s no need to inform.

The whole point is the danger of unintentional feedback of power into the grid.

He does not need to inform with an off-grid with grid backup. Grid backup essentially takes power from the grid on AC-IN but does not connect to feed back to the grid providing he has not connected the AC-OUT to a panel that is connected directly to the grid.

If he has connected is distribution panel directly to the grid and also to the AC-OUT of the inverter then yes you are correct but that's not really what he said. I fully understand the danger of unintentional export but these off-grid inverters by there very design cannot export back to grid unless you've somehow connected your distribution panel directly to the grid.

If I have this wrong then please accept my apologies.

 

[Goboatingnow]

He does not need to inform with an off-grid with grid backup. Grid backup essentially takes power from the grid on AC-IN but does not connect to feed back to the grid providing he has not connected the AC-OUT to a panel that is connected directly to the grid.

If he has connected is distribution panel directly to the grid and also to the AC-OUT of the inverter then yes you are correct but that's not really what he said. I fully understand the danger of unintentional export but these off-grid inverters by there very design cannot export back to grid unless you've somehow connected your distribution panel directly to the grid.

If I have this wrong then please accept my apologies.

I specifically referred to grid tie backup. We all agree no grid tie in any form ( even As an island ) does not need to supply information or seek permission.

 

[FlakBlag]

He does not need to inform with an off-grid with grid backup. Grid backup essentially takes power from the grid on AC-IN but does not connect to feed back to the grid providing he has not connected the AC-OUT to a panel that is connected directly to the grid.

If he has connected is distribution panel directly to the grid and also to the AC-OUT of the inverter then yes you are correct but that's not really what he said. I fully understand the danger of unintentional export but these off-grid inverters by there very design cannot export back to grid unless you've somehow connected your distribution panel directly to the grid.

If I have this wrong then please accept my apologies.

My preferred plan is to have both grid power and the inverter as the inputs to the crossover switch, and the main panel connected to the output. This will allow me to switch the house back to the grid if there is a fault with the inverter. The grid would also be connected to the AC-in on the inverter independently of the crossover switch (though with an isolator).

 

[FlakBlag]

There is no requirement to inform if using the protective earth

That's exactly what I need to know

 

[Phil.g00]

That's exactly what I need to know

great thread topic.

 

[billt1827]

No because you are not generating power to export back into the grid. You will still be consuming from grid but without any possible export back then it is akin to getting say an electric fire or other consuming type appliance and them expecting you inform them about that.

Actually, these days you do have to inform the DNO if you connect some consuming devices. You need to inform them if you connect a Level 2 EV charger or a heat pump, and your battery system could easily take as much energy from the grid a s a heat pump.

 

[FlakBlag]

Actually, these days you do have to inform the DNO if you connect some consuming devices. You need to inform them if you connect a Level 2 EV charger or a heat pump, and your battery system could easily take as much energy from the grid a s a heat pump.

Good point. The system will be configured to only charge batteries from solar. No reason to pay to charge them