Microgeneration 6kwh limit

buzz11

Question in relation to the 6kw single phase micro-generation limit: Can you have PV panels that would have a peak greater than 6kw but with some of it on different aspects and therefore should never reach the 6kw limit?

For example;
South facing panels 5.4Kwp
West facing panels 1.9Kwp

slave1

Yes, the limit is your Inverter so no problem hooking up 7.3kWp, that's what I have, 4.1SW and 3.3 NE hooked up to a 6kW Inverter.
Due to shading I'll never be generating 7.4kW

graememk

Also some have installed more but limited the export to 6kW

buzz11

graememk wrote: »

Also some have installed more but limited the export to 6kW

where you panels greater that 6Kw, I presume any excess is used onsite e.g by way of battery charging or to an immersion heater etc

graememk

buzz11 wrote: »

where you panels greater that 6Kw, I presume any excess is used onsite e.g by way of battery charging or to an immersion heater etc

No the inverters themselves can limit their generation. They physically won't export anymore than what they are set to.

quentingargan

You also have to stay within the limits of the inverter for warranty. Many 6kw string inverters are limited to 6.5kw of panels, even with different orientation. I know that is daft, but that's the warranty.

Some 6kw inverters, particularly battery hybrid ones, have a diffrerent topology and can take up to 8kw or more. Funny enough, one of the 3kw hybrid models can take 7kwP of panels under warranty, so even if you didn't bother with batteries, you could theoretically have 14kw of panels on two inverters. Your production would be much higher morning and evening and would flat-line at 6kw on sunny days, but that doesn't happen for as much time as you think, and panels are cheap...

ESB doesn't recognise export limiting standards such as G100. Their limit is based on fault currrent - what is the max current in the event of a fault.

buzz11

Thanks for the replies, I'm still a bit unclear...am I right in understanding it as follows;

• The 6Kwp limit applies to export situations only -- apart from planning permission restrictions, you can have as many panels as you wish.
  
• If you are not exporting to the grid, then you need an appropriately sized inverter to manage the panel output
  
• If you are exporting to the grid and have panel output greater than 6Kw then you really need two inverters, one to manage the export panel group and another to deal with the excess over 6kwp which cannot be exported

Have I got that right?

quentingargan

buzz11 wrote: »

Have I got that right?

'fraid not buzz. You can have a total of 6kw of inverters. Usually that will be a single one of 6kw. Many of these can take up to 8 or 9kw of panels, and to be honest, putting 9kw of panels on a 6kw inverter produces about 48% more than 6kw of panels would on the same inverter.

If your system is producing more power than you are using at a moment in time, you will export the surplus, but ESB does not currently accept any export limiting and allow you have more than 6kw of inverters.

If you really wanted more panels and had a battery system, you could build a system with only 6kw of inverters feeding the grid from a battery pack, but an infinite number of charge controllers charging the batteries that feed the inverter. But it'll cost yer!

unkel

quentingargan wrote: »

putting 9kw of panels on a 6kw inverter produces about 48% more than 6kw of panels would on the same inverter.

That figure of 48% doesn't seem to make sense. Would you mind explaining?

You would have a lot more useful electricity in winter or on a cloudy day by oversizing the array, 50% more. But obviously in full sunlight most of the year the extra production over 6kW would be completely lost (0%) instead of going to FIT / battery / diverter / EV / even to the grid for free

So overall I would expect the figure to be somewhere in the middle between 0% and 50%, not near one of these ends

quentingargan

unkel wrote: »

That figure of 48% doesn't seem to make sense. Would you mind explaining?

You would have a lot more useful electricity in winter or on a cloudy day by oversizing the array, 50% more. But obviously in full sunlight most of the year the extra production over 6kW would be completely lost (0%) instead of going to FIT / battery / diverter / EV / even to the grid for free

So overall I would expect the figure to be somewhere in the middle between 0% and 50%, not near one of these ends

In practice, a 6kwPV systems spends very little of its time at bang on 6kw. I used PV-Syst to do simulations of 6.5kw of panels and 8.91kw of panels on the same 6kw inverter, all based on 30 degree south facing in Dublin. This is the result. It shows a 1.9% loss in KwHrs per KwP

unkel

Any link to the site you use, Quentin? I've tried

Linky


But it doesn't let you limit the size of your inverter

Not that I don't believe you, but I like to see these things for myself It would solve a big problem that I thought I would have later on this spring / summer when I plan to install significantly more PV and would need to replace my inverter or add an inverter. Replacing my 3.6kW inverter with a 6kW one (easy enough to DIY) would be infinitely better than to have to get an electrician to install an additional inverter

quentingargan

unkel wrote: »

Any link to the site you use, Quentin? I've tried

Linky


But it doesn't let you limit the size of your inverter

Not that I don't believe you, but I like to see these things for myself It would solve a big problem that I thought I would have later on this spring / summer when I plan to install significantly more PV and would need to replace my inverter or add an inverter. Replacing my 3.6kW inverter with a 6kW one (easy enough to DIY) would be infinitely better than to have to get an electrician to install an additional inverter

PV-Syst isn't free I'm afraid (quite the opposite...).

Here is the simulation for 9kwP into 6kw inverter. You will see on the last page that inverter losses due to "over inverter nominal power" is 2.3% of total energy.

I also enclose a similar pair of simulations on 15KwP of PV into a 10kw and 15kw inverter. In this case, the industrial roof pitch is 15 degrees, so the lost power is lower.

mp3guy

quentingargan wrote: »

'fraid not buzz. You can have a total of 6kw of inverters. Usually that will be a single one of 6kw. Many of these can take up to 8 or 9kw of panels, and to be honest, putting 9kw of panels on a 6kw inverter produces about 48% more than 6kw of panels would on the same inverter.

If your system is producing more power than you are using at a moment in time, you will export the surplus, but ESB does not currently accept any export limiting and allow you have more than 6kw of inverters.

If you really wanted more panels and had a battery system, you could build a system with only 6kw of inverters feeding the grid from a battery pack, but an infinite number of charge controllers charging the batteries that feed the inverter. But it'll cost yer!

As usual, more confident misinformation around solar PV on boards, pervading and misleading countless people no doubt.

This is incorrect, source: I'm on a domestic single phase connection, have 10.24kWp of panels and 9.2kWp of inverter power across two inverters that dynamically limit the export to 6kWp. SEAI don't care and the ESB provided written confirmation via email that this was acceptable.

Coltrane

mp3guy wrote: »

As usual, more confident misinformation around solar PV on boards, pervading and misleading countless people no doubt.

This is incorrect, source: I'm on a domestic single phase connection, have 10.24kWp of panels and 9.2kWp of inverter power across two inverters that dynamically limit the export to 6kWp. SEAI don't care and the ESB provided written confirmation via email that this was acceptable.

I have the same situation as mp3guy.


But Quentin is I suspect also correct! In Ireland, two conflicting interpretations of the law are often practised at the same time.

mp3guy

Coltrane wrote: »

But Quentin is I suspect also correct! In Ireland, two conflicting interpretations of the law are often practised at the same time.

This is definitely true.

slave1

mp3guy wrote: »

As usual, more confident misinformation around solar PV on boards, pervading and misleading countless people no doubt.

This is incorrect, source: I'm on a domestic single phase connection, have 10.24kWp of panels and 9.2kWp of inverter power across two inverters that dynamically limit the export to 6kWp. SEAI don't care and the ESB provided written confirmation via email that this was acceptable.

Good stuff, I've just gone from 4.1kWp to 7.4kWp and therefore maxed out my inverter (6kW Solis). I have an idea for another ~4kWp and either micro inverters or another dual MPPT inverter so will probably end up like yourself and need to think about dynamic limiting export too....another thread

quentingargan

mp3guy wrote: »

This is definitely true.

There may indeed be multiple realities within ESB. My information comes from a number of discussions I had with the Head of Protection in ESB Networks. He was adamant that their current determining factor was fault current. What could go wrong if everything failed - if it meant more than 25A could be exported, that was that.

I know industry groups are lobbying for G100 standards of export limiting to be accepted, but I knew of no site where this had been accepted without witness testing, and usually a G10 relay to back up the grid limiting in the inverter.

I would be interested to know what was said in writing by ESB. It could be a useful precedent.

unkel

Is there any benefit in having more than one inverter? Quentingargan has stated that the overproduction of undersizing an inverter is barely lost at all. And I can see lots of cons of having more than one.

unkel

quentingargan wrote: »

I would be interested to know what was said in writing by ESB. It could be a useful precedent.

Aye, would be good if you could share that here, mp3guy. Maybe just a screenprint of their reply obviously with your personal details removed?

quentingargan

unkel wrote: »

Is there any benefit in having more than one inverter? Quentingargan has stated that the overproduction of undersizing an inverter is barely lost at all. And I can see lots of cons of having more than one.

Just if you have multiple orientations, or too many strings with mismatched panels.

On the 6kw limit, from HERE

Micro-Generator is a source of electrical energy which operates in parallel with ESB Networks LV System and rated up to and including:

25 amperes (6kW) at low voltage [230 volt] when the connection is single phase
16 amperes(11kW) at low voltage [230/400 volt] when the connection is three ph

If you wish to connect a generator with an output greater than that for micro-generation, go to ​connect a wind farm or other renewable generator.

mp3guy

unkel wrote: »

Aye, would be good if you could share that here, mp3guy. Maybe just a screenprint of their reply obviously with your personal details removed?

My installer did the communicating but forwarded me the email, I won't be sharing it publicly online. All it took was emailing the Network Services Bureau at networkservicesbureau@esb.ie, stating I'm putting in 9kW of inverters with an export limit of 6kW and will NC6 be accepted in this case (as opposed to having to go with NC5).

mp3guy

unkel wrote: »

Is there any benefit in having more than one inverter? Quentingargan has stated that the overproduction of undersizing an inverter is barely lost at all. And I can see lots of cons of having more than one.

Features really. If you could have one giant inverter with batteries, EPS, 4 MPPTs, huge peak output power you'd be laughing, but I don't think they exist. Oversizing on individual inverters is dead handy e.g. with east/west arrays where it won't explode in the Summer but you get that long tail of production in the Winter.

unkel

quentingargan wrote: »

Just if you have multiple orientations, or too many strings with mismatched panels.

Hope I'm not hijacking the OP, but it is kinda relevant here. I have 5 * 290W Amerisolar panels on my high roof and 5 * 355W Longi panels on my kitchen roof, all south facing and in series connected in one string. Would you consider that too mismatched, as the output would only ever be a max of 10 * 290W or so?

If I need to separate them out and I would add say a 12 * 360W Longi string (south facing on my shed that will be built soon), could I put that in series with the 5 * 355W Longi string, so I could use a dual MPPT 6kW inverter (7545kwp in total)

mp3guy wrote: »

My installer did the communicating but forwarded me the email, I won't be sharing it publicly online.

Any reason for not sharing, if you hide any personal / identifying details?

quentingargan

unkel wrote: »

I have 5 * 290W Amerisolar panels on my high roof and 5 * 355W Longi panels on my kitchen roof, all south facing and in series connected in one string. Would you consider that too mismatched, as the output would only ever be a max of 10 * 290W or so?

If I need to separate them out and I would add say a 12 * 360W Longi string (south facing on my shed that will be built soon), could I put that in series with the 5 * 355W Longi string, so I could use a dual MPPT 6kW inverter (7545kwp in total)

It is hard to say exactly how MPPT tracking will deal with different panels on one string, but Amerisolar 290 Max power point current is 9.07A. That would throttle back the Longi from 10.27A, losing about 12% of their power in the process.

Very little difference between 355 and 360 in the same type of panel. But you can't put 17 panels in series on most single phase inverters. Your limit there is

Open circuit voltage * No. of panels * 1.15 temperature coef <600V

unkel

So the max I could lose is 355W * 12% * 5 panels or just over 200W and that only at full output in full mid day sunshine, in summer. I can live with that loss

So keep those 10 panels on the one string and then all the new panels on the other string. Get a 6kW dual MPPT inverter. Paying even €100 extra for a triple MPPT inverter would not be worth my while.

mp3guy

unkel wrote: »

Any reason for not sharing, if you hide any personal / identifying details?

Just don't think a plain screenshot of a redacted email between a PV installer and ESB representative is actually more useful to anyone than being able to contact the ESB themselves. Also not interested in contacting the involved parties and asking can I post their email online, redacted or not.

quentingargan

unkel wrote: »

So the max I could lose is 355W * 12% * 5 panels or just over 200W and that only at full output in full mid day sunshine, in summer. I can live with that loss

Not just in full midday sunshine. Your smaller panels would always throttle back your larger ones. The current passing through would decrease on all panels proportionally, though the MPPT voltage shifts a bit as well.

If you already have a 3kw inverter for example, you can always add a second 3kw one and have four MPPTs altogether.

unkel

The issue is that I can replace my current inverter myself, quick and easy job, no costs involved, no materials needed. And to install a new one it's nearly impossible to find an electrician who would do it and then I'd be looking at €200 + materials, even if I did most of the work myself, so nearly €300 in all. I'll pass on that!

slave1

Numbers gotta make sense, glad to see this point being made.

Ubbquittious

In theory if the meter doesn't ever see less than -6kW going through it you should be alright. Doubt anyone will be calling to your house and inspecting your setup in any great detail.

Makes sense that there would be some limit to the size of the array for the inverter but once it isn't possible for the max current/voltage to be exceeded it should work whether the power is coming from an oversize array or from millions of hamsters running in hamster wheels. Though I'd guess it would be possible that certain times of the day on good sunny days too much current would be available for short periods when the sun is shining at just the right angle.

Should be possible to come up with some form of current limiting circuit to put between the inverter and panels. They probably put the warning on the inverter so they can skimp on panel-side current limiting circuit. I have a charge controller kicking about that has a similar warning not to exceed certain size panels even if it's within the voltage range. Must mean that it doesn't have any self-limiting feature built in or the manufacturer believes it's not reliable

graememk

quentingargan wrote: »

It is hard to say exactly how MPPT tracking will deal with different panels on one string, but Amerisolar 290 Max power point current is 9.07A. That would throttle back the Longi from 10.27A, losing about 12% of their power in the process.

Very little difference between 355 and 360 in the same type of panel. But you can't put 17 panels in series on most single phase inverters. Your limit there is

Open circuit voltage * No. of panels * 1.15 temperature coef <600V

So I currently have 20 longi 360w. On a dual string solis 6kw inverter.

Could that be pushed to 24 or even 28 panels?
12 or 14 on each string?

It's on low angle roof (walkable), split 50:50 north east/south west.

quentingargan

graememk wrote: »

So I currently have 20 longi 360w. On a dual string solis 6kw inverter.

Could that be pushed to 24 or even 28 panels?
12 or 14 on each string?

It's on low angle roof (walkable), split 50:50 north east/south west.

You can push it to 24 panels - 12 per string, but no more than that. Open circuit voltage is 40.8.

40.8x13x1.15 is 610V. Too high.

Doing it the hard way, for that panel type, temperature coefficient is 0.27% per degree. You have to allow 45 degrees between test conditions of 25c and lowest air temperature of -20c. Tolerance on Voc is 3%.

Worst scenario at -20 degrees is 40.8 x 13panel x 1.1215 temp coeff x 1.03 tolerance = 612V

The voltage is fairly steady - it is mostly current that is affected by light intensity.

unkel

Thanks Quentin for (indirectly) stating that 600V is the max per MPPT string, not for the inverter as a whole. Some of us were wondering about that and it is not that obvious from the inverter's spec sheets :-)

graememk

quentingargan wrote: »

You can push it to 24 panels - 12 per string, but no more than that. Open circuit voltage is 40.8.

40.8x13x1.15 is 610V. Too high.

Doing it the hard way, for that panel type, temperature coefficient is 0.27% per degree. You have to allow 45 degrees between test conditions of 25c and lowest air temperature of -20c. Tolerance on Voc is 3%.

Worst scenario at -20 degrees is 40.8 x 13panel x 1.1215 temp coeff x 1.03 tolerance = 612V

The voltage is fairly steady - it is mostly current that is affected by light intensity.

Thanks I did think 14 was too much. Will look into getting 4 more panels in total, (2 per string)

blue chuzzle

Hi all,

I have a slightly different situation along these lines

I originally had a 3kw Solis inverter and 3kwp of panels. I replaced 3kw inverter with a 6kw hybrid so I could add a battery and some more panels 2.5kwp

I've changed the inverter and have the batteries attached and now I'm going to add the new panels. The obvious thing to do is to put the new panels as a second string on the new inverter but at the moment, the 6kw inverter can put up to 6kw into the house when it's demanded by taking 3 from the batteries and panels at the same time.

Can i add the new panels to the 3kw inverter so that on a sunny day, i can cover higher demand between the two inverters (say, the electric shower) without having to draw from the grid, but I will never put more than 6 out to the grid because I have less than 6 kwp of panels

Is there anything I need to do to have a hybrid and a non hybrid inverter connected at the same time or will they just automatically work together?

idc

No idea if this is for real but on Irish solar Facebook group I've seen 2-3 people claim the 6kWh limit is going to be reduced. No idea if its true or if this is yet another scare tactic from some dodgy installers to push people into signing up! One mentioned may is the deadline? Anyone else heard this ?

UPDATE: thought i'd email ESBN about export limiting like mp3guy did and before i did i found this:

Micro-Generators (esbnetworks.ie)

Information note in relation to Microgeneration units which exceed the defined 25A limit

It has recently come to our attention that some Microgeneration units are being installed which have output currents in excess of the 25A limit allowable as per the ESB Networks document Conditions Governing the Connection and Operation of Micro-Generation (esbnetworks.ie). 

We acknowledge that units may have been inadvertently purchased and installed based on manufacturers model references as opposed to specific data sheet information. In order to address the issue in a reasonable manner and ensure there is absolute clarity, we are now highlighting that we will continue to accept applications for units referenced as 6kW, but with an output current of up to a maximum of 28A single phase, until 31st May 2023, however from that date on any units with an output current over 25A will not be eligible for connection under the NC6 Microgeneration connection application route.

buzz11

https://www.boards.ie/discussion/comment/120339403#Comment_120339403

I have 3 Solis inverters, one hybrid and two non hybrid. Solis told me that they don't communicate with each other and there is no way of doing so. In my case, I put a reduced export limit on the hybrid inverter to allow headroom for non hybrids to export and thereby not exceeding the 6kw limit

idc

Also reading more I expect mp3guy getting permission is unusual based on ESBN own documentation!

Conditions Governing the Connection and Operation of Micro-Generation (esbnetworks.ie)

This is literally in the foreword of that document !

Any installations with inverter capacity greater than Micro-Generation (6/11 kVA) are classified as MiniGeneration (up to 50kVA installed inverter capacity). There are no active Export Limitation Schemes available under the Micro-Generation ‘Inform and Fit’ process, as the inverter capacity itself, which shall be within the allowed Micro-Generation limits, is used to determine the export limits.

Active Export Limiting Schemes are, however, available under the Mini-Generation connection process.

blue chuzzle

https://www.boards.ie/discussion/comment/120339615#Comment_120339615

Thanks buzz, you have all three connected and the only thing you need to do was to limit the export?

Sounds like I won't have an issue then connecting the second inverter to the new panels as I described?

silver_sky

https://www.boards.ie/discussion/comment/120339562#Comment_120339562

I wonder how many will be caught out by installer not submitting the paperwork. Mine has still not been done (went from 1.2 to 6 last year) and chasing the installer again. ESBN suggested I get the completed form from them and send it on myself!

Here's the page on that the guy gave me https://www.esbnetworks.ie/help-centre/help-faq/generator-step-by-step-guide/step-2---make-an-application

"Email the completed form to NetworkServicesBureau@esb.ie or post it to:

ESB Networks DAC

NC6 Microgen Notifications

New Connections

Sarsfield Road

Wilton

Cork

T12E 367"

DC999

https://www.boards.ie/discussion/comment/120340527#Comment_120340527

Problem is it's only 'active' from day submitted to EBS afaik. Though you could certainly argue to get it approved from the date of commission on the NC6 form. No idea if ESB accept it being backdated. I thought that was a required of the grant for installer to submit that to the SEAI portal? If so, you can ask the SEAI to provide you a copy of you can't see in the portal.

ELM327

https://www.boards.ie/discussion/comment/120340280#Comment_120340280

Once you are not exporting more than 6kW peak ever - especially if you have a smart meter - you will never get caught on this. Strictly speaking having 3 inverters with potential export of combined greater than 6kW is breaking the rules and you should be under NC7 instead of NC6.

Reality though, if you're like a lot of folk on here with lots of storage and dump loads etc you will never export near 6kW anyway so nothing to worry about.

irishchris

https://www.boards.ie/discussion/comment/120339403#Comment_120339403

https://www.boards.ie/discussion/comment/120339615#Comment_120339615

If it is only one hybrid and other inverter is non hybrid the hybrid export limit will cover both. I have a 6kw hybrid and 2.5kw standard inverter.

Set the hybrid limit at 6kw and it will adjust the power it receives from its own panels down to make sure that combined power never exceeds 6kw being exported. It does this from it's CT clamp on the main esb feed.

Often would be exporting 6kw on a sunny day and if I put on a large load like kettle or washing machine the hybrid will up it's production to max available to cover it whilst maintaining 6kw export

silver_sky

https://www.boards.ie/discussion/comment/120340557#Comment_120340557

No SEAI grant in my case. Would have been great, but house doesn't qualify for it.

buzz11

https://www.boards.ie/discussion/comment/120341929#Comment_120341929

Thats not happening on my system and today I was exporting 6-7 kw for a few hours and for 30 min period it was sustained export of 7 to 9kw.

The inverter settings are Set Backflow Power 6,000w - which I assume is correct? Is there anything else I should check? TIA

irishchris

https://www.boards.ie/discussion/comment/120374693#Comment_120374693

What size and make are both of your inverters. Is only one of them a hybrid?

I currently have a sofar hybrid and when set up with export limit it drops it's production to make sure that combined there is never more than 6kw exporting. If turn on something with large load and it is a sunny day it will ramp up production whilst maintaining max 6kw exporting and ramp down when power is not required if producing more than 6kw.

I previously had a solis 5g hybrid and it also did the same. Are both of your inverters going through the same main consumer unit?

buzz11

All 3 inverters are Solis, 5G 6kW hybrid, mini 2.5Kw 4G and mini 1.5kw, no battery and export limit set as in pic below.

Where did you monitor the generation/load when you turning things on/off? via the solis cloud app?

All three go through the same consumer unit, the 6kw & 2.5kw are in the house and 2.5kw in the garage which is cabled back to the house fuse board. I can see all 3 on the app & via solis cloud website

Jonathan

https://www.boards.ie/discussion/comment/120375216#Comment_120375216

Have you turned on the Export Power Limiting function (not just set the Power Limit to 6kW as shown in photo above)? If you have it enabled, your status on the home screen should say LmtByEPM.

I'd also enable the failsafe option (shut down hybrid inverter if it loses the grid CT) to ensure that export never exceeds 6kW.

buzz11

https://www.boards.ie/discussion/comment/120375252#Comment_120375252

Yes the export limiting was/is set to ON, and I've just turned on the failsafe option.

I'm not seeing the Current Status like yours, my version is;

Inverter Version 330026-000000 Model F6

graememk

https://www.boards.ie/discussion/comment/120375282#Comment_120375282

The Current status only shows Limit by EPM when its limiting by EPM.

Does the backflow power setting go negative? If you set it at 0 and work from there.

irishchris

https://www.boards.ie/discussion/comment/120375216#Comment_120375216

Monitored mine via home assistant which updates every ten seconds and also via myenergi