Two Inverters

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