How the solar cuts out in a power cut

Couple of different aspects to your question. The solar panels themselves have a spring loaded switch, which is held closed when there is grid power. When the grid drops, the spring opens the circuit and cuts the power coming from your panels into your inverter.

The inverter itself is a "grid-tie-in" inverter (general case here), and it's constantly looking at the voltage and frequency of the power coming in from the grid. It's not different from your telly, or oven in respect to that it's powered from the grid, not the solar panels themselves. So when the grid goes, it's got no power, so it shuts down.

100% mate - and that why I was saying there's a couple of different aspects to answering the question.....

The edge case is as you know the inverter can be powered in a limited capacity via the batteries etc, (EPS feed, or even the whole switchover that some people have to their consumer unit) but that's probably outside the scope of the question. The main thing is that it's powered by the grid itself, so when the grid is gone......it goes dark itself.

Ach, I didn't really want to get into the specifics......it was more just trying to answer the original question and I'm sort of sorry I attempted it now. But yeah, there are a couple of different "areas" for lack of a better word inside your inverter. Most hybrids have 2 inverters inside the box. When the grid goes down, a lot of the inverter box (as a unit) is dark. Yes, many of them as I mentioned have an EPS outlet, and people have hooked that into the consumer unit via a changeover, but it's an edge case.

95+% of people don't have a changeover switch that or use the EPS - so for them, when the gird is down, the inverter is effectively down as it's powered by the grid.

What surprised you? Don't half think about solar it's a no brainer. Best investment you will make unless you are aged 85+!

When the inverter shuts down either during a grid power outage or excess wind, does it power itself back up again automatically when power is restored or is manual intervention required?

I don't know for sure but what I was told by an installer, and I read it somewhere too, is that you shouldn't feed the fireman switch with the batteries.

Found it.

5. Shunt and battery back up  The shunt must isolate the solar panel array on loss of mains and cannot be re-energised from the battery backup. The shunt circuit must disconnect the solar array automatically when the AC power is removed and automatically reconnect when the AC is re-energized. The position of the shunt switch must be within 1.5M of the array. This also applies to external systems where the inverter is located outside and the shunt needs to be within 1.5m of the array, taking care to ensure the DC cable is appropriately protected from external forces i.e., use of conduit or SWA cable etc. Where a “back-up system” i.e., battery storage with auxiliary supply is in use, the shunt switch operation must not be compromised and cannot be re-energised from the back up supply. In the event emergency services are called to a property and the mains electricity supply has been disconnected the shunt switch must maintain the disconnection of the solar DC supply and must not be re-energised by the auxiliary output as this will lead to a health and safety risk to emergency services.  

I don't believe that's correct, my understanding is that it's to conform to Is10101 and Building Regs part B.

Through these requirements of Part B of the building regulations and I.S. 10101, all domestic PV installations installed under this Scheme must:

• Provide an automatic (i.e., automatically operated by disconnection of the main AC supply to the building) shunt (or interlocked) isolation of the circuit (whether AC or DC, and two pole) from the solar PV modules into the building, as close to the solar PV modules as possible, and a maximum of 1.5m internally from the point of cable entry to the building. 

• Where the circuit from the solar PV modules does not enter the building, this point of automatic isolation must be within 1.5m of the solar PV modules. • For ground mounted system the shunt (automatic isolator) must be within 1.5m of the solar PV modules.

• This system of isolation shall automatically isolate the circuit from the solar PV modules when the AC supply is disconnected to the building, i.e., a shunt or interlocked isolation function. 

• ‘Shunt’ or ‘interlocked’ isolation of the DC circuit is the only acceptable manner of meeting the Building Regulation TGD B – Fire Safety (2017) for the purposes of this Scheme. 

• For the avoidance of doubt the disconnection of the circuit from the solar PV modules must be automatic and operated by removal of AC supply to the building and must not be operated by means of a dedicated switch, pushbutton, ‘fireman’s switch’ or other manner. 

• For the avoidance of doubt an isolation of the supply from the PV modules is required in ALL cases, whether micro-inverters, DC optimised inverters, where the inverter is within 1.5m of cable entry or any other configuration is used.

• This system of isolation must automatically reconnect upon restoration of AC supply to the building. A warning label must be applied to the main external AC connection point to the building 

Ignorance is the best defense🤣

For the rest of the time you could have an extension lead to the neighbours keeping the battery topped up.

One neighbour could stump up the 300 a year standing charge for a dozen houses with solar. The powers that be are probably sharpening the feck out of their legal instruments to stop that kind of cord cutting situation arising

I know, I was joking. If ever you're asked plead ignorance.

Ignorance is the best defence! I just had to 😂

In fairness you are right though, we need some clarification on the rule with the fireman switches because I was under the impression it was just a requirement for the grant like most SEAI red tape box ticking requirements. I had a quick look but couldn't find anything 100% on it.

There must be another reason for Islanding prevention other than "protect ESB staff". How come a professional electrician will touch a public electric grid in a power cut assuming 100% sure there will be nothing on the line in the first place?

You only assume that when working in an installation you can physically see and verify there is nothing feeding the wires.

Even if you enforce PV systems to automatically disconnect from the grid there is nothing preventing someone connecting a generator to their mains...

In my case I have a Projoy Safety switch wired in such a way that without grid power it automatically disconnects the panels from the hybrid inverter. So I would have an off-grid inverter but powered by the battery alone, no panels.

Yes, specifically for Pv.

Agreed about off grid but building regs need to checked as it may be in that too.

Might be a bit of stretch with the changeover🤣

I think that this is somewhat related to rhe original question.

Is there a way of having societs that will work in the event of a power cut?

Hybrid inverter but no battery.