Solar install with G99 fast track help (Phase/Neutral Loop Impedance)

[bullishbroker24]

Hi,

This is my first post on here and hopefully you guys will go easy on me.

I have installed 6.4kW solar on my roof and plan to add a Solis 6kW RHI 5G hybrid inverter with 4 Pylontech US5000 4.8kWh batteries.

I've messaged back and forth with my DNO (SSE) and they have told me that I can either limit it to 3.68kW and install my system and then notify them via SG-1 and hand in an A3-3 form once connected.

Or they could grant me 7.36kW export under SG-3 fast track application in my area. What they need is a Phase to Neutral Impedance Loop test.

 

I've looked up this test online and not much is available on how it's done. From what I've gathered its testing the Line and Neutral loop impedance before my consumer unit (Their side of the equipment). They are looking for a figure of 180 mOhmes maximum.

 

Has anyone actually done this or know how it's done?

 

I've added the form below and the relevant section is just page 2.

 

Looking forward to your responses. Thanks

FO-NET-CAB-008-Loop Impedance.docx

[Jenki]

Don't see why this couldn't be carried out at the consumer unit, using the Phase and Neutral of the main switch, unless the tails have been extended, if so the measurements could be taken at isolator / switch fuse.

It's a standard test using an earth fault loop impedance tester. Your electrician can sort this no problem.

Edited February 25, 2023 by Jenki
Clarity

[bullishbroker24]

Thanks Jenki

[Nickfromwales]

Hi @bullishbroker24 and welcome.

 

8 hours ago, bullishbroker24 said:

and plan to add a Solis 6kW RHI 5G hybrid inverter with 4 Pylontech US5000 4.8kWh batteries.

 

You should look for batteries where the entire pack is "balanced", as they are not in those batteries ( these are cheap batteries for a reason )   

Similar looking 'rack mount' batteries in this thread, which I currently have on the table in my list of battery options. But these are balanced. Have a quick read.

 

 Also, are you really going to be able to charge AND DISCHARGE 20kWh every 24hrs? Sounds like a LOT of storage to me?

[ProDave]

0.18 ohm loop impedance is a pretty low target.  You would have to be quite close to your substation to achieve that.  We only achieve 0.24 ohm and rural properties here I have seen as high as 0.4

 

This is a simple test that any electrician can do for you.  The trick with paying someone to do such a short test, is to find someone really really close to your home, or someone prepared to call in on his way to or from another job so you need to be flexible with your availability.

[bullishbroker24]

Interesting Nick, but for me price is key. The whole system is subsidised from my Solar install in Greece, so replacement wouldn't be a problem.

I can charge way over 20kW of battery within my 6 hr window overnight, plus the solar during the day...I want to have the maximum amount of battery storgage I can, as I use over 40kW per day without even charging the car. Others who use Pylontech batteries say they are ok for the years theyve used them.

 

Every person I follow with big systems installed at home say if they could change anything it's to add more battery storage for the winter.

 

Cheers.

[bullishbroker24]

That's what I was worried about, the 0.18 ohmes seemed like a very very low target. I doubt I'll get anywhere near that, but I'll have a go. Otherwise it will have to be limited export I guess.

I haven't even checked where the substation is, I was trying to see if I could rent a Loop tester just to save me the hassle as I can imagine its a very easy test to do from some videos I've watched.

 

I'll try and call the electrician and see if he'll do it on his way home.

 

Thanks for the reply ProDave

[Nickfromwales]

12 minutes ago, bullishbroker24 said:

The whole system is subsidised from my Solar install in Greece, so replacement wouldn't be a problem.

An odd ethic. I'd prefer money to go into my bank and then stay there.

 

Pylontech are difficult for ongoing soft / firmware updates also, so I'm offering advice based on experiences from installers in the industry whom I lean on for support for my own clients projects.

You get bronze, silver and gold standards with anything, but these are chrome plated plastic. These fail the same way my Makita 18v cordless power tool batteries do, with an unbalanced charged pack.

 

20 minutes ago, bullishbroker24 said:

Interesting Nick, but for me price is key.

Which usually gets calculated by adding together cost, longevity, reliability etc aka "value for money" vs "cheapest ones I can get, regardless". Value is perceived differently by different folk, as always.

 

21 minutes ago, bullishbroker24 said:

Others who use Pylontech batteries say they are ok for the years theyve used them.

Except the owners of the FUBAR one in that thread, and his fellow 'less than OK' customers with similar issues, plus the ones who cannot get any firmware updates, and so on.

[ProDave]

If you want to try yourself, you can get old loop testers for peanuts  https://www.ebay.co.uk/sch/i.html?_from=R40&_nkw=loop+tester&_sacat=0&_sop=15

 

But they will be out of calibration.  Question is, what paperwork do the DNO want?  Just a figure?  or a figure backed up by the instrument serial number and calibration certificate?

[bullishbroker24]

They want the figure with a photo of the test taking place. It's on page 2 of the document I posted on post 1.

[ProDave]

42 minutes ago, bullishbroker24 said:

They want the figure with a photo of the test taking place. It's on page 2 of the document I posted on post 1.

Best not show a picture of a vintage test meter then.

 

Wait until after April.  If your test comes out worse than 0.18 ohm, then they will likely say you need a network upgrade.  If you applied for that today, there would be a cost.

 

But it looks like after April you may not have to pay for network upgrades.  See this thread:

 

I will be watching for how people find this situation after April, I would like more PV myself but don't want to pay for a network upgrade that I don't think I actually need as I have no intention of exporting anything.

[bullishbroker24]

I'm not really interested in export anyway to be honest, I just thought it would make my life easier in the future if things change and I have a higher export ability. I might just install and go with the G98 and limit my inverter to the 16amp, in total honesty I'd probably set the inverter not to export anything as I have a 300l tank to heat and then a 75kW car battery to fill before I let them have any of it. Thanks for your help and I'll keep an eye on that post about the DNO connection charges.

 

Cheers

[ProDave]

4 minutes ago, bullishbroker24 said:

I'm not really interested in export anyway to be honest

Neither am I.  In nearly 4 years, I have exported a total of 334kWh which is just the times the inverter generates more than the house uses, even with dumoing to the immersion heater.

 

The point is the DNO are only interested in how much could be exported, not how much will be exported.  They take no notice of you actively trying not to export.   I will delve into this more after April when it becomes clear how the new system works in practice.

[joth]

39 minutes ago, bullishbroker24 said:

I'm not really interested in export anyway to be honest, I just thought it would make my life easier in the future if things change and I have a higher export ability.

Yeah you're not going to be eligible for paid export either way today, as it's a DIY rather than MCS install. But it is an interesting question: in 10 years time there will be a lot of installed solar where people have lost the paperwork (over house sale purchases etc) and will pressure mount to introduce payments for non-certified installs. 

[Nickfromwales]

10 minutes ago, joth said:

Yeah you're not going to be eligible for paid export either way today, as it's a DIY rather than MCS install. But it is an interesting question: in 10 years time there will be a lot of installed solar where people have lost the paperwork (over house sale purchases etc) and will pressure mount to introduce payments for non-certified installs. 

Any MCS job will immediately go onto permanent record with the MCS.

They’ll just type in your address and say yup or nope. End of.

 

If you can prove your AC coupled equipment is on the approved list ( so could be MCS approved ) then they should just let you get paid for export, afaic. 

[Radian]

I've got an MCS registered installation but not even bothered to apply to any utility company for SEG payments. So far, if I did, I'd have been paid a grand total of £1.45 @ 5p/kWh. Hardly worth the cost of the phone call.

[SteamyTea]

11 minutes ago, Radian said:

So far, if I did, I'd have been paid a grand total of £1.45 @ 5p/kWh. Hardly worth the cost of the phone call.

But is it worth the cost of a diverter?

[bullishbroker24]

I'd say on a self install, it's totally worth the cost of the diverter. My whole system works out less then 11k, all self installed. 17k MCS would maybe come close to my system, but that's an extra 6k for 2 days work and a piece of paper. I use Home Assistant to manage most things at the moment so I will install a diverter and then divert the rest to the pool heater. Consumption is not my problem it's production and cheap rates lol

[joth]

7 hours ago, Radian said:

I've got an MCS registered installation but not even bothered to apply to any utility company for SEG payments. So far, if I did, I'd have been paid a grand total of £1.45 @ 5p/kWh. Hardly worth the cost of the phone call.

Octopus are offering 15p. You don't mention system kWp or how long installed, which is pretty necessary to make sense of this factoid

[Nick Thomas]

21 minutes ago, joth said:

Octopus are offering 15p

Or ~37p at peak times with flux.

 

Each kWh exported then pays for ~1.85kWh electricity imported off-peak, which you can launder through your heat pump with CoP=3 for ~5.5x more heat than the PV diverter would have given. Or you can buy gas to burn for a similar-ish number.

 

As for the rest of the factoid, my 3.6kWp array with battery for load-shifting has still exported ~55kWh since the start of the year, which at the 15p rate is £8.25. But even at the 5p rate that's £2.75. Roughly comparable, but the real fun will come in summer where the export will permit me to shift power interseasonally. Battery can't really do that.

 

 

[Nickfromwales]

21 hours ago, bullishbroker24 said:

I will install a diverter and then divert the rest to the pool heater

Is that a heat pump or resistance heater?

[Radian]

16 hours ago, joth said:

factoid

🤣 You got me.

 

15 hours ago, joth said:

Octopus are offering 15p. You don't mention system kWp or how long installed.

 

Well, the only take-home message I wanted to convey is that the capacity of my PV system and level of self-use meant I have nothing to sell. No numbers necessary.

 

But this may change as I only had the 3.2kWp system installed late last year and I'm already seeing odd peaks of 3.3kW which can exceed my diverter and house load. I also get that at 15p for Octopus Outgoing Fixed, it could make sense to turn off the diverter for now. But gas is due to go up again in April with Cornwall insight Forecasting 17.05p for Q123 so unless Octopus respond in kind, that's a bust. Besides, at 80% boiler efficiency I have to buy 13.75p of gas to displace 1kWh of electric so turning off the diverter, and offsetting the gas bill with export payments may barely work anyway. 

[joth]

On 25/02/2023 at 11:37, Nickfromwales said:

Any MCS job will immediately go onto permanent record with the MCS.

They’ll just type in your address and say yup or nope. End of.

 

If you can prove your AC coupled equipment is on the approved list ( so could be MCS approved ) then they should just let you get paid for export, afaic. 

Which is crazy as in 10+ years time the system might have been  completely replaced, upgraded, anything, all with bootleg and DIY work, but the white mark still sits there in the MCS database for perpetuity indicating this is a blessed address that may receive export payments 

I'm sure there's some clause saying you should notify them if making non-certified alterations, but if you bought the house since the changes you'd have no idea at all of the actual provenance of the install.

 

Also: I'll laugh my socks off when MCS get held up to randomware and lose their DB.

 

Yes agree just showing the certificate of the equipment installed should be sufficient (although logically you should show that to the DNO when notifying them of connection, regardless of export payment)

 

Edited February 26, 2023 by joth

[Dan F]

On 25/02/2023 at 10:42, bullishbroker24 said:

I might just install and go with the G98 and limit my inverter to the 16amp,

You still need G99 SG-1 for that, not G98. AFAIU.

[Nickfromwales]

I've been looking into this ahead of my install, and the MCS for the panels ( MCS is about the generator btw not the inverter etc ) basically just means I have to use a recognised rail and a recognised clamp and that's about it. Equipment needs to be "on the list" also, but that's a given.

Just waiting for a man with a micro-digger and then the office / studio begins! Then 21 lovely new solar collectors atop, and with my electricity bills I cannot wait to see that meter grind to a halt. 11 more going on the gazebo ( after I rebuild it after having to rip it down to get the bloody digger in / facilitate the office build ). Gotta break a few eggs.....

Defo sold on the SunSync hybrid 8.8 Inverter, so I'll be off to the shops soon as. Also going to Tigo everything, but prob only one optimiser per 2x panels vs 1x per panel. The  arrays can then be loaded according to the capacity of the inputs rather than dual input from mono-array(s), and I'm going E/W split on office roof and new gazebo will be rebuilt S-ish. Will be satisfying to see the individual ( or pairs of ) panels on the app, albeit almost valueless, but satisfying.