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

[SteamyTea]

Just don't use the DC isolator to disconnect the system when it is running.  Switch of the AC side first.

Ask my old electrician what happens.  Told the customer it was some 'dust on the contacts'.

[Dillsue]

9 minutes ago, SteamyTea said:

Just don't use the DC isolator to disconnect the system when it is running.  Switch of the AC side first.

Ask my old electrician what happens.  Told the customer it was some 'dust on the contacts'.

Or dont install a DC isolator on a SE system with safe shutdown?? Im not saying its the correct thing to do on every system, but on a SE system you remove the chance of a non techy person(householder) doing something detrimental. On a SE system switching off the AC isolator, flicking the on/off switch to off, switching off the inverter MCB, power cut will all shutdown the optimisers and kill the hazardous DC voltage.

[SteamyTea]

1 minute ago, Dillsue said:

but on a SE system you remove the chance of a non techy person(householder) doing something detrimental.

This is always a problem with technology.  I used to lecture in IT, and often met students that had a friend or relative that 'knew everything about computers', then then asked me how to fix something.

 

That incident with the DC isolator was actually caused by the module fitter adding an extra couple of modules, 'to do the customer a favour'.  Still think the sparky should have checked the numbers there first.  Bet he does now.

[Timmyk]

1 hour ago, SteamyTea said:

Just don't use the DC isolator to disconnect the system when it is running.  Switch of the AC side first.

Ask my old electrician what happens.  Told the customer it was some 'dust on the contacts'.

 

Maybe I’ll avoid the DC isolator in that case!

[SteamyTea]

10 minutes ago, Timmyk said:

 

Maybe I’ll avoid the DC isolator in that case!

NO. Just make sure it is the correct size, and you operate the system correctly.

[Timmyk]

44 minutes ago, SteamyTea said:

NO. Just make sure it is the correct size, and you operate the system correctly.

😬 Okay! Added one to the order.

 

When I looked at the order last night, there were 91 of the GSE frames available. This morning at 8am...22. Clearly popular right now!

 

Ordered:

6 x Qcells G9 345w all black

All the GSE kit needed to fit them + flashing

1 x DC isolator (2 pole 1 string)

1 x AC isolator (20A 4 pole)

25m 6mm2 DC wire

 

Total about £1800.

 

SolarEdge Compact 2kw Extended to be sorted later.

 

Next to work out how to get the DC wire from the 2 east facing panels at the back of the house to the optimiser on the west facing opposite side of the house. Within the roof maybe? Does it need to go in conduit? Will only be around 80V at 10A going through there I think.

 

[SteamyTea]

6 minutes ago, Timmyk said:

Does it need to go in conduit?

Pretty sure wiring regs say it must for mechanical damage protection.

@ProDave can check.

 

I seem to remember that 80V at 1/8th of an amp was enough to kill.

Same as 1 kg moving at 1 m/s.

Or 1 g moving at 1000 m/s, which is a bullet.

(May not be the actual numbers but you get the picture, I am more interested in the conversation on the next table, couple of Emmet that 'love the place' and want to buy a holiday home)

[Timmyk]

Hi all,

 

This project is (finally) nearly done.

 

I just want to check one thing. AC wiring from the  Inverter to the house simply goes:

 

Inverter -> AC isolator -> free space on consumer unit/fuse box.

 

There’s nothing more complex than that? Why does power come preferentially from the inverter rather than mains supply?

 

thanks!

tim

[SteamyTea]

3 minutes ago, Timmyk said:

Why does power come preferentially from the inverter rather than mains supply

Because the inverter supplies at a slightly higher voltage. Electricity takes the path of least resistance.

[Timmyk]

6 hours ago, SteamyTea said:

Because the inverter supplies at a slightly higher voltage. Electricity takes the path of least resistance.

Great, thank you.

 

So finishing it off is as straightforward  as I’ve described and nothing else needed? 

[SteamyTea]

Just now, Timmyk said:

Great, thank you.

 

So finishing it off is as straightforward  as I’ve described and nothing else needed? 

I think so.

 

Basically you need to be able to isolate the inverter from both the AC and the DC sides.  Just remember that if the inverter is working, isolate on the AC side first.

[Dillsue]

7 hours ago, Timmyk said:

So finishing it off is as straightforward  as I’ve described and nothing else needed? 

Dont forget to notify your DNO with a G98 notification form

[Timmyk]

On 07/07/2022 at 05:50, Dillsue said:

Dont forget to notify your DNO with a G98 notification form

Do I need to do that even if I don’t intend to sell the extra back to the grid? 

[Carrerahill]

5 minutes ago, Timmyk said:

Do I need to do that even if I don’t intend to sell the extra back to the grid? 

No. 

 

 

[SteamyTea]

8 minutes ago, Timmyk said:

Do I need to do that even if I don’t intend to sell the extra back to the grid

If it is physically connected i.e. NOT off-grid, then yes.

It is a safety thing, the DNO can physically check that all generation is off. It is why you have to tell them where the isolator is physically located.

[Radian]

DNO also needs to know that the inverter (that may push current back into the grid) is type approved and below the generation limit.

[Dillsue]

1 hour ago, Timmyk said:

Do I need to do that even if I don’t intend to sell the extra back to the grid? 

Yes. For all the reasons others have stated and so the DNO can keep tabs on how much generation is connected to each section of the grid. If everyone connects 16amp of PV generation, its gonna get interesting on a sunny summers day. By everyone telling the DNO what theyve installed to DNO can manage the potential summer peak of generation.

[Carrerahill]

The last 3 posts are all technically correct, but many don't bother.

 

All MCS approved inverters have anti islanding, in other words if the grid goes down they cannot continue to feed onto the LV network and potentially kill someone working on a line.

 

Yes they want to keep tabs, but under 16A they don't care, if the argument is so they can keep tabs, then we would need to submit a cooking schedule so they could work out when we are all importing 16A. They know we have PV generation, they know to expect a slight reduction in energy demand on a sunny day where PV is prevalent, but we are talking 16A or less here. 

 

You can always install it and just fill out the form, many MCS accredited installers have not been sending in the forms for <16A systems and it has become fairly well known that there are systems on the grid not registered.

 

If you do want to, install it all, the submit a G98 and put it in as self install - the ENA form doesn't mention MCS accredited. 

 

 

[Dillsue]

28 minutes ago, Carrerahill said:

Yes they want to keep tabs, but under 16A they don't care, if the argument is so they can keep tabs, then we would need to submit a cooking schedule so they could work out when we are all importing 16A. They know we have PV generation, they know to expect a slight reduction in energy demand on a sunny day where PV is prevalent, but we are talking 16A or less here. 

 

Thats not a correct comparison . We all cook at different times and individual cooker rings in all households will fire at differeing times giving a low diversified import load. If all households on a section of grid installed 16amp of PV export then first sunny day they will all export at exactly the same time and the local voltage could rocket. If the DNOs know in advance that those households have PV they can manage the grid in a timely way.

 

I dont know if current PV install levels are unprecedented but they are certainly high and keeping your DNO informed about what youre doing can only help them keep abreast of things

[Radian]

We all have a contract when we get power connected to our houses. It's all set out in the National terms of connection

 

Quote

“Maximum Export Capacity” means, in respect of a Connection Point (or the Connection Points collectively), the maximum amount of electricity (expressed in kW or kVA) which is permitted by the Company to flow into the Distribution System through the Connection Point (or the Connection Points collectively). The Maximum Export Capacity of the Connection Point shall be zero unless otherwise agreed;

 

Page 53 states that we shall not export a Watt without prior agreement. Now how much notice is taken and what enforcement is applied is anyon's guess.

But terms are terms.

 

I should mention that @Dillsue kindly pointed me in the direction of the contract a while ago.

Edited July 8, 2022 by Radian

[Nickfromwales]

I’ll be dialling my 2x hybrids back to absolutely zero export. 
24x 360w Solarwatt panels incoming. Getting twitchy now. My electricity meter is digital, but lately I can hear it grinding away as it continues to mock me and my delays in fitting my PV.

”My day will come, my flashy red-lighted friend”. 😈 

[Dillsue]

3 hours ago, Radian said:

Page 53 states that we shall not export a Watt without prior agreement. Now how much notice is taken and what enforcement is applied is anyon's guess.

I think theres a national concession to allow export up to 16amps, but part of that concession is to let your DNO know that you are able to export, via a G98 notification.......quite a reasonable arrangement and its beyond me why some people seem so averse to doing so

[Radian]

I'm not so sure anyone can just fill in a form though. In the  G98 guidance notes we have this paragraph on page 33:

Quote

Installation must be carried out by installers who are competent and have sufficient skills and training to apply safe methods of work to install a generating unit in compliance with EREC G98. This includes having recognised and approved qualifications relating to the primary energy source and  general electrical installations. There are companies who design, install and commission domestic generation. They can fully certify and sign off installations. 

 

And the legal mandate on the same page:

Quote

Your installer must notify the DNO within 28 days of commissioning the generating unit, and provide them with information on the installation. This is  legal requirement. 

 

[Dillsue]

12 hours ago, Radian said:

I'm not so sure anyone can just fill in a form though. In the  G98 guidance notes we have this paragraph on page 33:

And immediately following that para it refers the reader to the MCS web site, yet theres absolutely no requirement to use MCS installers which the para infers is a requirement!

 

As with the addition of any circuit to a domestic install, a new PV connection needs to be tested and inspected by a part P accreditted spark or get your local building control to test and inspect.

[joth]

12 minutes ago, Dillsue said:

12 hours ago, Radian said:

I'm not so sure anyone can just fill in a form though. In the  G98 guidance notes we have this paragraph on page 33:

And immediately following that para it refers the reader to the MCS web site, yet theres absolutely no requirement to use MCS installers which the para infers is a requirement!

 

(I found the text on page 25 not 33)

 

That guide has other mcs issues, it states MCS is the only approved scheme for getting SEG payments, but since Nov 2019 Flexi Orb has existed as an alternative.

https://www.solarpanelprices.co.uk/articles/solar-panels/flexi-orb/