Two Inverters

SE Galway

Hello folks,

Thanks for all this additional information, it's been a great read

Our MIC is 16kVA, excuse my ignorance but is this MIC capacity to our advantage regarding expanding our current PV solar system with a second inverter in an east West configuration?

With regards to throttling, this is something our installer suggested this evening.

What are our thoughts on our 16kVA MIC mentioned about and what this might mean for solar array expansion?

Thanks.

Regards,

SE Galway

unkel

https://www.boards.ie/discussion/comment/120954298#Comment_120954298

You can. But it would help if they were identical and they support connection of one as master and one as slave. And the only reason for that setup is to have more battery charging / discharging power than one inverter can give you. Personally I would just look for a more powerful inverter and buy a single one!

SE Galway

Hello Slave1,

We do have a NC6 which we filed before the tightening of exported electricity.

I had a look at our MIC and it's 16kva, does this help our case if we want to expand our solar array limiting one of the inverters to 6KW?

If we're already at a MIC of 16kva do we still need to submit an NC7 when we expand our solar PV system?

Thanks.

Regards,

SE Galway

Mr Q

https://www.boards.ie/discussion/comment/120959871#Comment_120959871

The MIC is for import. The NC6 is what will determine your export limit currently.

You would need a NC7 to have more than 25A of inverters connected to the grid.

SE Galway

Hello Mr. Q,

My PV Installer submitted our NC6 back in 2021 for our expiring 5kw system, how would I find out what our MEC currently is based on that NC6? Or is it the case that I need to submit another NC6 to determine my current export capacity?

Thanks.

Regards,

SE Galway

DC999

https://www.boards.ie/discussion/comment/120960262#Comment_120960262

Email networkservicesbureau@esb.ie explaining and asking them for a copy of the NC6 that was filed on your behalf, so you can see what inverter size was submitted. The NC6 shows the inverter limit. They are very helpful people here have said.

I didn't know what MEC was, Max Export Capacity (kVA) = Total Installed Inverter Capacity. I checked my NC6.

Buffman

https://www.boards.ie/discussion/comment/120959871#Comment_120959871

No, as other's have said, the only way to tick all of ESBNs boxes for even 'potentially' going over 25A export is to pay €977.85 for an NC7, even if the system is set up to not allow it.

https://www.boards.ie/discussion/comment/120960262#Comment_120960262

Your current available MEC is 6kVA (25A) because that's the max allowed under a NC6, and your existing 5kW install will take up most/all of that allowance.

You've a nice MIC of 16kVA, around 66A. So, if you did want to go down the NC7 box ticking route, with the €977.85 click of an ESBN computer mouse, your 'new' available MEC would equal your existing MIC of 16kVA. So that would roughly be around 15kW max inverter export.

I assume you're already receiving FIT based on the your existing NC6?

(MIC=Maximum Import Capacity, MEC=Maximum Export Capacity, to save anyone having to google)

graememk

https://www.boards.ie/discussion/comment/120961142#Comment_120961142

16kva is an 80 amp supply

For export esbn assume the highest end of the 230v allowance, and for import it's the lowest end (ie 200v)

Buffman

https://www.boards.ie/discussion/comment/120961164#Comment_120961164

Good to know, thanks.

SE Galway

Hello Buffman,

Thanks for your input.

Yeah, we're in receipt of a deemed payment for our solar export based on our 5kw inverter. We haven't gone the smart meter route yet but will considerate it if we can expand our current system. We'd be looking to expand by an additional 3 to 5kw.

One last question on the NC7 form. Is it the case that the solar array is expanded first followed by sending in the NC7 form to the ESB or is the NC7 application made first to the ESB before the solar array is expanded and an additional inveter added?

Keep in mind that we made a NC6 submission in 2021.

Thanks.

Regards,

SE Galway

Buffman

https://www.boards.ie/discussion/comment/120963102#Comment_120963102

Ye, been a while since I read it all but IIRC you have to do pay up and do NC7 first and have a connection agreement signed before construction, followed by installation confirmation cert within 12 months. Have a good read of the Mini-gen link I posted as there's a lot involved. Definitely do the sums as adding the fee will effect payback period, but on the plus side VAT on supply and install is gone since your got the first system installed.

Westfest

Hello everyone,

I’m reaching out to gain clarity on the recent regulations set by the ESB (Electricity Supply Board) regarding Micro Generation connections. I hope the community can shed some light on my queries.

1. Max Limit of 5KW Inverter: The new rules state that with a connection at a low voltage of 230 volts (single phase), the max permissible limit is 25 amperes (about 6kVA). This translates to a maximum inverter size of 5KW. My primary query is: Is this 5KW solely for export, or does it account for both export and internal consumption?

2. Installation of Two 5KW Inverters: Given that our annual energy requirement is between 10,000-12,000 kW, we are contemplating installing two 5KW inverters. Is this allowed under the new regulations?

3. Functioning of the Two Inverters: If we were to install two inverters, could one be set up primarily for exporting while the other manages the house load? Is it possible for one inverter to exclusively manage the load without exporting any surplus energy?

Just to mention, I’m based in Sligo, though I doubt that has any bearing.

Apologies in advance for my limited understanding. I’m a total novice in this area and any guidance would be highly appreciated.

Thank you for your time and insights!

championc

Who's to stop you installing extra inverters of any size.

Just make sure you have a mechanism to stop any exports exceeding 5kW.

Many inverters gave a limited function, to limit export to xkW

10-10-20

https://www.boards.ie/discussion/comment/121002994#Comment_121002994

1. That limit is the total for all grid-tied inverters, ie any inverters which are attached to the mains supply on the property which have the potential to export, even if not configured to do so. It would not count independent inverters such as a fully-isolated grid (such as on a shed) with zero connection to the ESB mains.
2. In theory that is possible but I have yet to see a split configuration which would allow greater than 25A to the letter of the NC6 regulations.
3. Again, in theory yes, but see answer 2.

BTW, you're confusing two terms in question 2 which is important to get right; it may be leading you into thinking that you need two inverters:

"Our annual energy requirement is between 10,000-12,000 kW" - It might seem trivial, but it should be kWh. That's the measure of energy over time (hours). So 1kW consumed over a period of 10 hours would equal 10kWh. With inverters then you measure the max instantaneous generation capacity and that's 5kW, but it doesn't tell you what duration that it can supply that wattage for. If you then put solar and a battery behind the inverter then you have storage potential - and that can be measured in kWh. So you can't divide the yearly consumption of 10,000kWh by the inverter's 5kW and size the system that way, you need to break down your usage per-day so that you can obtain a kWh figure.

An example would be by taking 12,000kWh and dividing that by 365 days to get roughly 33kWh consumed per day. Then you know that you'd ideally like your generation capability to beat that in the Summer months. For Winter you commonly would then take what you get and take the remainder off the grid, but your Summer should be paid-for.

Here's a Gary Does Solar to explain that in a graphical way:

https://www.youtube.com/watch?v=IzBHs4878BY&t=26s

https://www.boards.ie/discussion/comment/121005091#Comment_121005091

In fairness, that's not in the spirit of the rules, the rules are there to protect the electrical distribution network and the ESB are limiting the export potential so that in the event of a fault on your equipment (especially this limitation mechanisim) that it doesn't have the capability of sending excessive current into local distribution.

idc

Agree with @10-10-20 the ESBN rules for NC6 are quite clear that it excludes export limitation features and is the total max output of all inverters. but I expect people will/can ignore this given I don't expect ESBN to check every house! Also for some reason mp3guy has multiple inverters and export limitation without ESBN having any issue with it on just an NC6.

https://www.boards.ie/discussion/2058169884/my-16kwp-domestic-system

championc

Once we all have Smart Meters, that will most likely become the "policing" mechanism. If you export over 5kWh in any hour, you're likely to show up with red flags (if they create such reports to flag these)

graememk

https://www.boards.ie/discussion/comment/121006623#Comment_121006623

It was before they really "cared" or noticed

It was also before the nc7 was a thing.

That horse has already bolted but the rest in the stable are restrained

mp3guy

https://www.boards.ie/discussion/comment/121006985#Comment_121006985

Exactly. This is also what my original installer reckons. My system is "grandfathered in" so to speak. I put my NC7 on ice last December due to voltage concerns but things will be changing for my supply locally in the next few months so I'm going to resurrect it.

...Ghost...

https://www.boards.ie/discussion/comment/120176601#Comment_120176601

I assume one would run the dumb inverter to the CU either directly, or via a shed/garage mini CU?

If that is the case, and there is no communication between the dumb inverter and the main (hybrid) inverter, does this mean that any generation running through the dumb inverter simply offsets the the load potentially needed from the grid and would feed any batteries connected to the hybrid inverter?

Examples:

(a) House load is 8kW. Main solar generating 4kW. Extra solar generating 3kW.

Result = Importing 1kW from grid.

(b) House load is 6kW. Main solar generating 4kW. Extra solar generating 3kW.

Result = Sending 1kW to battery.

Would the above be correct with the setup below? If not, what is missing?

allinthehead

@...Ghost...

You can set the hybrid Inverter to either recognise the export/production of the dumb inverter and charge the batteries, or to ignore it and let it go to the grid. The dumb inverter will first feed the house load before exporting or charging the batteries.

Microinverters would work very well on your shed. You can get 4 port micro's. A string inverter might work out cheaper though.

graememk

https://www.boards.ie/discussion/comment/122074033#Comment_122074033

On the sunsynk/deye you can select it.

On the solis you can't, but will pick up the excess from other inverters

On givenergy it doesn't pickup the excess from other inverters

Have first hand experience on the first 2 but have been told about the third

allinthehead

https://www.boards.ie/discussion/comment/122074157#Comment_122074157

My mistake, I assumed they would all have the option.

That's poor enough, I wonder is this just a software limitation.

championc

https://www.boards.ie/discussion/comment/122073645#Comment_122073645

Yes

A Hybrid will see power going towards the grid, and grab it.

I doesn't know where it is coming from, neither does it care

...Ghost...

Hoping I don't need to start new thread, as this one is on topic with 2 inverters. Note that a RECI will be completing all relevant work, but I want to know what I am talking about.

I plan to have 30-45kWh of storage (2 or 3 batteries) with the first 15kWh being built this week hopefully. Currently have a 5kW Solis hybrid inverter with a 5.2kWp system on the house. Smart meter installed.

I plan to add about 5kWp to the shed and ground floor extension (2 strings). I know a dumb inverter can feed into a mini CU in the shed and from there to the main CU, or I could bypass the mini CU, set the dumb inverter up beside the hybrid inverter and then feed into the main CU, but I would like some help please, as I am not sure what direction is best to go. Here is my goal…

I want to be able to charge and discharge up to 10kW from the batteries if possible, which would almost eliminate any day rate grid import for me. Likewise, I would like to be able to charge the batteries up over a 3 hour window. What is the best way to do this assuming I have 2 x 15kWh Seplos batteries? The second (maybe 3rd) battery will be bought and ready by August.

From the thread, I see an upgraded hybrid inverter could be an answer, but I would prefer to add to what I have rather than replace, because I will have a total of 4 strings and I don't want to change out the new inverter so soon. Also I think I would still have a battery discharge limit of 5kW???

I currently avail of a standard night rate which I could use to fully charge a full compliment of 45kWh @ 5kW/h over the night, but then I can't take advantage of much cheaper boost rates, or advantageous peak dump rates. Help me out before I start buying stuff please 😊

10-10-20

Likewise, I would like to be able to charge the batteries up over a 3
hour window. What is the best way to do this assuming I have 2 x 15kWh
Seplos batteries?

But that's impossible without a 10kW inverter…? If the largest allowed inverter is ~5.5kW, then three times that is 16.5kW. So are you planning on going for NC7 or similar?

...Ghost...

https://www.boards.ie/discussion/comment/122199625#Comment_122199625

Only seeing this now. I'm not sure what is possible, or allowed. Would a second inverter with grid export switched off be possible? Could this let me me increase the battery charge/discharge limits from 5kW to 10kW? I'm putting it out there because I have seen inverters hooked up together to do this, but I don't know exactly how, or if it is allowed here. No plans to apply for NC7.

10-10-20

https://www.boards.ie/discussion/comment/122247941#Comment_122247941

Id love to tell you otherwise but it's not allowed under the rules and there isn't an inverter or solution on the market which offers a true 'zero export' option. I'd be riding that bus for sure if it was an option.

idc

https://www.boards.ie/discussion/comment/122247941#Comment_122247941

I expect your only option would be independent circuits - ie one connected to grid and others that have no connection to grid at all, but don't know if there electrical rules around that. Eg what happens in case of fire - they disconnect you at meter and have no idea half the house is still fully powered! Then again thats no different to inverters with a backup circuit. Firemen cut power to house but backup circuits are still live from battery!!

championc

You could parallel an external battery charger

slave1

https://www.boards.ie/discussion/comment/122247941#Comment_122247941

A second inverter can be CT clamped at the CU to stop exporting at whatever limit you want, so as an extreme example if Inverter A was exporting at 6kW then Inverter B would effectively shut down as it has no bandwidth to export.

Apparently some folk have this setup and working rock solid

idc

https://www.boards.ie/discussion/comment/122253773#Comment_122253773

The only issue is any such setup breaks rules of NC6. ESBN don't allow for export limitation on NC6 - it is entirely defined as max combined inverters can not exceed 25Amp on single phase. But honestly I don't see how they'll know.

championc

Which is why I am suggesting an external separate charger. Would be 100% compliant with NC6

idc

@championc yep no issue with your suggestion 😀 whereas @slave1 suggestion won't be 100% compliant, but no doubt plenty of people do that anyway!

Thewitheredowl

Hi All,

Just looking for some advice on my setup here:

Originally had a Sunsynk 3.6kW inverter in my attic. 2 x 5kWh batteries attached and 4kWp of panels on the roof. All worked fine, but decided I didn't really want the batteries in the attic, so I moved the Sunsynk inverter and batteries to my shed. Found a solution with the help of one of the guys on this forum for sending power meter (I have an inline power meter as opposed to CT) readings of my main incomer over ethernet which I then pick up in my shed and route it into the Sunsynk. The inverter can see my live power consumption and it's accurate.

I then installed a Huawei 5kW hybrid inverter in the attic to connect to the solar panels. I didn't connect a power meter/CT to this inverter (I can do this easily if it's needed), I just let it take power from the panels.

So, in theory, any excess generated by the panels by way of the Huawei should really be picked up by the Sunsynk in the shed in order to top up the batteries, but this is not happening. The batteries are consistently taking only 350w of the excess panel production, even at times when there is up to 3kW available. 350w will to to the batteries and 2650w will be exported.

I can see on the Sunsynk that it has a grid power reading of -3000w in the instance above, but it's not grabbing that and sending it to the batteries.

graememk

https://www.boards.ie/discussion/comment/122608422#Comment_122608422

Need to tick the box, Ac couple on grid side.

Thewitheredowl

Worked perfectly. Really appreciate the input