Hybrid inverter for small in roof 2kw array - help please!

[Dillsue]

11 hours ago, ProDave said:

My issue is a PV system with battery storage that is set to NEVER export and only supply the house needs should be allowed in any quantity without restriction.  As batteries come down in price this is becoming much more normal.  WHY do such systems still have to jump through all the hoops and be subject to power restrictions?  THIS is where the DNO's need to modernise their thinking.

G98 allows the system you describe, in fact it allows up to 16amp export on top of what you pump into the battery. Its the householders choice if they want to use kit that doesnt meet G98.

If your choice of kit doesnt meet G98 but is configured for zero export then youll get permission to connect, but youll need to prove to the DNO it is actually limited to zero.

[dpmiller]

I could've sworn I'd posted a while back on voltage monitoring but I can't seem to find it now. I had on loan (for a job) a Fluke VR710 voltage logger. While setting it and it's software up I had it logging down at the house for a few days. Conveniently these were very sunny days.

 

There are five properties on our pole transformer, four of which have 3-4kW solar. I'd need to hunt out the log files- they're on the computer down there- but I was surprised just how tight the voltage was clamped.

[SteamyTea]

17 minutes ago, dpmiller said:

There are five properties on our pole transformer, four of which have 3-4kW solar. I'd need to hunt out the log files- they're on the computer down there- but I was surprised just how tight the voltage was clamped.

You find those files and I shall see how it correlates with grid frequency.

[kommando]

The way to have your cake and eat it, ie adding batteries is a Fasttrack G99 application which is detailed here.

 

https://www.northernpowergrid.com/fast-track-electricity-storage-applications

 

is the combined capacity of your generation and electricity storage devices less than 32A per phase?

 

As they look at the total generating power eg inverters plus battery power then I doubt you can get away with 3.6kw of inverters plus some battery power even if its on a single 16A circuit.

 

Edited July 11, 2022 by kommando

[Radian]

6 minutes ago, SteamyTea said:

You find those files and I shall see how it correlates with grid frequency.

Which, with some joined-up thinking, could indicate to the distributed energy resources (our PVs EVs and BVs^*) how stressed the network is at source and adapt their export accordingly. With bottom-up network architecture some of the current problems become solutions.

 

^{*(I made up BVs to stand in for Battery storage)}

[SteamyTea]

24 minutes ago, Radian said:

Which, with some joined-up thinking, could indicate to the distributed energy resources (our PVs EVs and BVs^*) how stressed the network is at source and adapt their export accordingly. With bottom-up network architecture some of the current problems become solutions.

One of the problems I found when doing my ResM was that nearly all the research is either small scale, i.e. load reduction to take the load of a large diesel generator, or purely academic i.e. what would happen if we turned fridges on and off in response to grid frequency fluctuation.

 

We do have large scale grid modulation though load shedding, it is well managed and is based on historical scenarios i.e. kettles on at half time.

Our grid is based on predictions i.e. weather, time of day, marginal generation capacity, voltage and frequency tolerances.

If say a million automatic storage devices started to switch half a gig of power on and off in response to changes in parameters, when they decided it was right to do so, our grid would quickly become unstable. Case of tail wagging the dog.

This is why, even though we have the technology, it is not done.

Everything on our grid has to be controlled centrally, and the effects predictable. 

We have seen what happens when an unusual, but predictable event happens alongside another such event.

https://www.independent.co.uk/news/uk/home-news/uk-power-cut-cause-national-grid-wind-gas-energy-latest-a9051016.html

 

 

Edited July 11, 2022 by SteamyTea

[Nickfromwales]

4 hours ago, Dillsue said:

If your choice of kit doesnt meet G98 but is configured for zero export then youll get permission to connect, but youll need to prove to the DNO it is actually limited to zero.

Yup. I will dump into AGM’s or DHW preheat cylinder ( TS with a DHW coil feeding cold inlet of combi or diverting straight to hot network ( Caleffi valve to be fitted ))

[markocosic]

Why do that that rather than displacing gas fired electricity generation elsewhere @Nickfromwales?

 

Your cost to parity for the export tariff Vs gas as it stands.

 

[Timmyk]

Interesting discussion - thanks everyone. I think on balance I’ll just fill in the forms to be safe - regardless of it’s actually meaningful or not.

 

Quick question about wiring. I’ve taken everyone’s advice that despite this Solaredge inverter having a built in DC isolator, I’m going to put an external one in as well.

 

this is how it currently looks:

Question is simply - does one dc cable from the optimiser pass through the neutral port in the dc isolator and the other through a live port? If so does it matter +ve vs -ve way round? 
 

Not both through separate live ports, correct? 
 

thanks! 
 

tim

 

Edited July 12, 2022 by Timmyk
Photo added

[Timmyk]

Ac isolator:

 

[Nickfromwales]

6 hours ago, markocosic said:

Why do that that rather than displacing gas fired electricity generation elsewhere @Nickfromwales?

 

Your cost to parity for the export tariff Vs gas as it stands.

 

System sized for near zero dependency on grid, ergo nothing to export.

[Dillsue]

5 hours ago, Timmyk said:

 If so does it matter +ve vs -ve way round? 

What is important is that you get the live conductors in L1-3 and not in T1-3. L = Line which is the incoming live supply. Unless the interlock has been defeated, you can only remove the isolator cover in the off position. In the off position the only live terminals should be L1-3 so your incoming cables from the PV array would be in L1 and either L2 or N depending on where you want to put the incoming -ve.

Unfortunately the same principle applies to the AC isolator!!

[Timmyk]

7 hours ago, Dillsue said:

What is important is that you get the live conductors in L1-3 and not in T1-3. L = Line which is the incoming live supply. Unless the interlock has been defeated, you can only remove the isolator cover in the off position. In the off position the only live terminals should be L1-3 so your incoming cables from the PV array would be in L1 and either L2 or N depending on where you want to put the incoming -ve.

Unfortunately the same principle applies to the AC isolator!!

Thanks.

 

I think I’ve got the AC isolator the right way round. The live coming from the inverter is connected to L1, and T1 outputs to the consumer unit. Technically though I guess both sides of this are live as one is an input from the inverter and the other is an output to and input from the consumer unit. 

Regarding the DC isolator - understand that the live side (from the panels) goes into the L side. I will put one into L1 and the other into N for the sake of neatness. T side will output to the inverter. Which is annoying as it’s basically upside down! 
 

Am I all correct there? 
 

thanks again

[Dillsue]

Switch the AC isolator off and the inverter should shut down, then which terminals remain live with the isolator cover off? 

[Timmyk]

1 hour ago, Dillsue said:

Switch the AC isolator off and the inverter should shut down, then which terminals remain live with the isolator cover off? 

 

The terminals to the consumer unit. I’ve currently got T1 going to the consumer unit. So I’m upside down, correct?

 

Interestingly this is the wiring guide for the DC isolator, which shows input from the PV array and output to the inverter all in T1-3. Not the best quality photo but the lower side of this is T1-3.

Edited July 13, 2022 by Timmyk

[Dillsue]

Yes, your AC isolator wiring isnt best practice but you can see from the wiring guide of the DC isolator that best practice isnt always followed.

The DC isolator wiring is using 2 poles for +ve and 1 pole and N for negative, the thinking being that if 1 pole welds closed theres a second pole that should still break the circuit when the isolator is turned off. That wiring guide would have been better wiring +ve In into L1, a link fitted from T1 to L2 and +ve Out wired to T2. Same principle for -ve. Keeps the Line/live and the load on the correct sides of the isolator.

Having already wired your AC isolator I personally wouldnt rework it to best practice, but maybe put some tape over the terminals fed from the CU and write "Line/live" on it. Be a reminder for you if you ever have to go back in there

[Carrerahill]

On 10/07/2022 at 10:16, Omnibuswoman said:

 

I was taught that must indicates a legal requirement that is enforceable, can indicates a guideline, and will is ambiguous, and usually deliberately so to lead people to think that something is a requirement when it is not...

You want to read a copy of BS7671 (or any reg to that matter) - you'll not really be sure what you are meant to do in some cases! 

 

Interestingly some are written very well, some very poorly. I know several authors sitting on sever of the boards for standards & regs from lightening protection to emergency lighting, and you can see why some are clear and some are not. Basically it boils down to the author(s). One chap who has penned a lot of the lighting standards is very concise and can speak and write English very concisely with no dubiety surrounding his regulatory writing, the other is very good in his field but cannot communicate.

 

We wrongly assume these regs and standards and guides are written by some un-earthly force of experts but in actual fact most are just written by industry experts and who checks their work? More industry experts, who all understand what has been written in the first place. 

 

 

[Timmyk]

16 minutes ago, Dillsue said:

Yes, your AC isolator wiring isnt best practice but you can see from the wiring guide of the DC isolator that best practice isnt always followed.

The DC isolator wiring is using 2 poles for +ve and 1 pole and N for negative, the thinking being that if 1 pole welds closed theres a second pole that should still break the circuit when the isolator is turned off. That wiring guide would have been better wiring +ve In into L1, a link fitted from T1 to L2 and +ve Out wired to T2. Same principle for -ve. Keeps the Line/live and the load on the correct sides of the isolator.

Having already wired your AC isolator I personally wouldnt rework it to best practice, but maybe put some tape over the terminals fed from the CU and write "Line/live" on it. Be a reminder for you if you ever have to go back in there

Thanks again.

 

I can probably wire the DC isolator as you've suggested without much of an issue to be fair. Interesting they've shown it like they have though - everything coming in and out of the T side. There's also pre-fitted connectors between L1 & L2 then L3 & N which I'll have to remove to do it properly. Weird

[Timmyk]

Okay so this now runs:

 

1. Optimiser(+ve)-> L1 -> T1 -> L2 -> T2 -> inverter +ve

 

2. Optimiser (-ve) -> N -> N -> L3 -> T3 -> inverter -ve

 

Lots of wiring inside the isolator as you can see but I’ve taken your advice and gone for best practice so hopefully you approve of it!

 

AC I’ve left as it was. Not ideal I appreciate but as you said it’ll work.

 

Now I just need to test the panels and inverter are working and then get someone willing to wire it into the fuse box.

 

Anything I’ve missed/words of warning?

 

thanks again for all the assistance

 

Tim

[Dillsue]

2 hours ago, Timmyk said:

Now I just need to test the panels and inverter are working and then get someone willing to wire it into the fuse box.

If youre looking for a solar experienced spark you might be waiting a while!!

In the meantime, with a 2kw inverter, you could plug your inverter into the nearest 13amp socket to get it powered up for testing. Not that Im endorsing it, but you could then leave it plugged in to grab some generation while the sun shines:)

[Timmyk]

15 minutes ago, Dillsue said:

If youre looking for a solar experienced spark you might be waiting a while!!

In the meantime, with a 2kw inverter, you could plug your inverter into the nearest 13amp socket to get it powered up for testing. Not that Im endorsing it, but you could then leave it plugged in to grab some generation while the sun shines:)

No. Way. I did not know this was possible! That would be fantastic! There's a socket directly next to the fusebox so can I just plug it in there and get it going temporarily?! It's been driving me nuts waiting for someone to come and get it wired in!

 

One interesting problem has arisen this evening - I got everything wired into the optimiser and measured the voltage it was producing. 

My setup is total 6 panels with 2 panels per input to the optimiser. As the optimiser does 4-8 panels (4 inputs, max 2 panels per input) I am only using 3 of the available inputs. I kept the final one free for if/when I can add 2 more panels to the flat roof.

 

The manual says that when the optimiser is disconnected from the inverter or the inverter is off, the optimiser will only output 10V total. Any less than that and there is a polarity/some other issue elsewhere. I am getting 7.5V. I tried with just 2 panels connected to a single input and it produced 2.5V.

 

My interpretation of that is that I've 'lost' 2.5V by leaving one of the inputs to the optimiser empty with no PV input. I have no idea if this matters or not and appreciate it's probably quite a niche problem, if it even is a problem. 

 

I suppose the only ways of know are 1) emailing SolarEdge tech support or 2) plugging the inverter in as you've suggested and seeing what it produces

 

Any suggestions on that?

 

By the way - I am very very grateful for your help on this. Couldn't have got this far without it! Thank you!

 

 

 

 

[Radian]

45 minutes ago, Dillsue said:

If youre looking for a solar experienced spark you might be waiting a while!!

In the meantime, with a 2kw inverter, you could plug your inverter into the nearest 13amp socket to get it powered up for testing. Not that Im endorsing it, but you could then leave it plugged in to grab some generation while the sun shines:)

A good test of Anti-Islanding - if you grab the pins of the 13A plug and it kills you, then Anti-Islanding isn't working. 🤣

 

I think it's usually much better than the two-second limit currently imposed by IEEE Standard 1547-2003 but I'd be very careful all the same. Pretend the scary 13A plug is horribly and unusually live, especially when recently unplugged. Oh my, this is a nightmare!

[MikeSharp01]

8 hours ago, Carrerahill said:

un-earthly

Not a good starting place - every installation needs a good earth somewhere.

[SteamyTea]

11 minutes ago, MikeSharp01 said:

every installation needs a good earth somewhere

Aeroplane don't.

[MikeSharp01]

Just now, SteamyTea said:

Aeroplane don't.

Do they stay up for ever then - eventually the must come down to earth!