I am a new PV householder - advice please. Unbalanced strings and wrong inverter

[Worcester]

OK guys, so 2 inverters are 2 SSEG's if you keeping to the STRICT interpretation, surely juniperz will need a G83/1-1 Stage 2 application, it might be one site, and the sum might be below 16A, however that is NOT the strict interpretation of G83/1-1 Stage 1

Surely a better implentation here would either be solaredge or enecsys.

Starting from scratch if you guys had a 12/4 to do what inverters/configurations would you have used?

 

[Noshocks]

I would have reccomended a 12 panel system, I am not convinced that the extra expense and hassle of the four panels are justified. Trouble is as we all know we may well lose the job as the next installer convinces the customer that 16 panels can be fitted, and then it ends in this situation.

 

[JulianC]

Would probably quote for the option of a 12 panels system using a 'traditional' inverter and a 16 panel system using Solar Edge

 

[juniperz]

If its aspare way on the rcd side you will have lots of inconvenience with tripping etc
if not just tell this company you will deduct the £150 as you don't require a new distribution board

Yes, I have already told them that.

Im concerned you should be using this company at all after all your concerns

I am concerned too - but given that I have paid a 20% deposit, my house is surrounded by their scaffolding, their rails are on the roof, all the wiring is in place and there is a inverter installed, I feel I have to give them the chance to propose a new configuration before I tell them they need to undo everything and give back my deposit. This may look worrying as an outsider - imagine being us!

 

[juniperz]

Would probably quote for the option of a 12 panels system using a 'traditional' inverter and a 16 panel system using Solar Edge

That's two votes for Solar Edge. Can someone explain why this is the best solution? I could suggest it to the installer. Let me guess - is it really expensive??

 

[JulianC]

That's two votes for Solar Edge. Can someone explain why this is the best solution? I could suggest it to the installer. Let me guess - is it really expensive??

Basically, the single or dual MPP tracker function is taken out of the inverter and individual MPP trackers (power optimisers) are fitted to each panel (usually mounted to the rail behind it). Therefore, the output of a particular panel is optimised, independently of what is going on with those around it. Such a system can accommodate different roof orientations and pitches and even different types of panel in the same string. The last job we did was the first time we fitted one but it was the only real option (3 panels SW facing on a main roof at 50 degrees and 7 panels W facing on a garage at 45 degrees, with added shading complications). Does cost more than a similarly sized Fronius or SMA inverter, but not massively so tbh. Dunno how much the cheap Chinese inverters cost....

 

[juniperz]

If this is the right inverter, it doesn't look much different in cost compared with the Growatt 3600 that they originally quoted.
Solar Edge Inverter 3680W 16A AC Clamped - SE-3680 at Swithenbanks Alternative Energy | Grid Tie Inverters | Solar Photovoltaic
Presumably it is the MPPTs for each panel that bump up the cost.

 

[JulianC]

One of these per panel: Solar Edge 250W Power Optimiser with MC4 Connectors at Swithenbanks Alternative Energy | Grid Tie Inverters | Solar Photovoltaic

 

[juniperz]

I couldn't resist downloading the Solar Edge Site Designer software

The software doesn't seem to include the UK-specific 3680W 16A AC Clamped - SE-3680 so I uesd the 4000

 

[juniperz]

With a conventional inverter, the wiring seems to be in series for each string, with the panels daisy-chained.
With a Solar Edge Inverter 3680W 16A AC Clamped - SE-3680 and 16 lots of Solar Edge 250W Power Optimiser + Panels, are they wired in parallel, so that 16 pairs of wires need to find their way from roof to inverter?

 

[JulianC]

Each panel is wired to an optimizer, then the optimizers are connected in series strings as per usual

 

[jason121]

Each panel is wired to an optimizer, then the optimizers are connected in series strings as per usual

reading these comments on the solar edge, i am thinking of using them on job with 2 roofs slightly different angles.
I know segen stock thems anywhere else ?
Also is there any other wiring to them besides the DC side ?
and can you excess information from any location thru the web.

 

[JulianC]

Got mine from Segen. No additional or unusual wiring required. However, the main inverter is transformerless so array frame bonding may be required depending on which version of the DTI guide you're working to! Didn't connect up the communications side of things on our job 'cos the customer didn't have an internet connection but as I understand it, you can access the monitoring through the interweb from anywhere (someone with more experience please correct me if I'm wrong)

 

[daytona600]

the best car made in china , would not compare to the worst car made in europe
get them to fit a real inverter suitable for the application ideally a poweredge due to string layout or dual MPPT sma/powerone

 

[juniperz]

I did manage to stand them down over the weekend, so nobody turned up yesterday. Apparently "senior management" are investigating. I had suggested something like a Solar Edge Inverter 3680W 16A AC Clamped - SE-3680 and 16 lots of Solar Edge 250W Power Optimiser + the 16 Suntech 245w panels that are in my garage. Though why I, the punter, has to suggest this {insert deity} only knows.

 

[daytona600]

you signed a contract with them they should supply exactly as ordered or equivalent or better in lieu
example girlfriend ordered a new kitchen , after fitting she noticed work tops where different you know what women are like with kitchens
she phoned to complain next day the MD of the company turned up with one of those huge amercian freezers
free as way of letting her down

 

[Worcester]

and Daytona600 is as good as his word too, he's not just saying it, he practices it as well.

 

[juniperz]

Busy week... The installer has come back saying they will install the quoted GroWatt inverter, use fire retardant board etc.
I am going to struggle to get out of a signed contract where they have offered to comply with the contract.
Whats the worst that could happen with
Growatt 3600MTL (2 MPPTs)
12 x 245w panels on a 30% roof
4 x 245w panels on a 35% roof
Could be wired 8+8 according to Growatt tech support, though that was before I knew about roof angle, and they haven't answered my recent question.

In another thread, FB said

As Gavin says: in summer it won't matter.
But with low sun in winter (or early/late in the day at other times of year), the difference in angle will make a big difference to panel output, so the bypass diodes will be working overtime.

By my reckoning, a 5-degree difference (35 v 30 degrees) in angle affects as follows:

Mid-day, June sun: 0.5%

Mid-day, March/Sept sun: 5%
(comparable to morning/afternoon summer sun)

Mid-day, December sun: 20%
(comparable to early-morning/late afternoon spring/autumn sun)

Will that amount to much over the year?
Is bypass diodes working overtime a big problem?
Thanks...

 

[sedgy34]

Busy week... The installer has come back saying they will install the quoted GroWatt inverter, use fire retardant board etc.
I am going to struggle to get out of a signed contract where they have offered to comply with the contract.
Whats the worst that could happen with
Growatt 3600MTL (2 MPPTs)
12 x 245w panels on a 30% roof
4 x 245w panels on a 35% roof
Could be wired 8+8 according to Growatt tech support, though that was before I knew about roof angle, and they haven't answered my recent question.

In another thread, FB said


Will that amount to much over the year?
Is bypass diodes working overtime a big problem?
Thanks...

When did you sign the contract as you have 7 days cooling off period

 

[juniperz]

When did you sign the contract as you have 7 days cooling off period

It's nearer a month ago.

 

[sedgy34]

Maybe you could say to them you are not happy with the equipment being installed
you want an power one inverter as you can alter the start up voltage on the mppt

 

[SolarCity]

Personally, I don't think installing the panels in this way is the right thing to do.

However, that is just an opinion. Because I don't install panels in this way, I'm not sure exactly what the real world effect would be. What I do know is that slight changes of pitch on my irradiance meter shows up quite different readings.

 

[juniperz]

Maybe you could say to them you are not happy with the equipment being installed
you want an power one inverter as you can alter the start up voltage on the mppt

Well they are supposed to be coming up with a quote for Solar Edge with 16 Optimisers by tomorrow. I will have to see what the difference is.

 

[pww]

Well they are supposed to be coming up with a quote for Solar Edge with 16 Optimisers by tomorrow. I will have to see what the difference is.

Accepting that Solaredge is probably the best solution, but if your installers did not offer it (or knew anything about it?) originally - do you want to be their first 'guinea pig' solaredge installation in these particular circumstances?

 

[juniperz]

Accepting that Solaredge is probably the best solution, but if your installers did not offer it (or knew anything about it?) originally - do you want to be their first 'guinea pig' solaredge installation in these particular circumstances?

A good point of course, but I am running out of time and options. But how hard can it be plugging 16 optimisers into the back of 16 panels and plugging them in one string into an inverter? OK, I was joking - that's why you are the experts and I am just the unfortunate punter! Is there any technical configuration to do in the inverter, or does it set itself up? I must say that having the Solar Edge transmitting data to the web is sounds interesting...

By the way, this was the Growatt Tech Support answer to my question "Our 2 roofs face in the same direction but they do NOT have the same angle - the 12 panels would be at 30% to the horizontal, and the 4 panels would be at 35% to the horizontal. Can we still use the 3600MTL wired 8+8?"

"5% should not be that much that affect the overall performance. In some instances 4 panels may be able to produce more that the 4 others, but limit their power production to the low ones. I am assuming this will be a 8+8 config using a 3600MTL".​

So if the extra for Solar Edge is too much, we just settle for the Growatt with 2 MPPTs wired 8 + 8, since that is the contract we have signed up to.
I just need to decide how much is too much... Answers on a postcard.

 

[wstevew]

A good point of course, but I am running out of time and options. But how hard can it be plugging 16 optimisers into the back of 16 panels and plugging them in one string into an inverter? OK, I was joking - that's why you are the experts and I am just the unfortunate punter! Is there any technical configuration to do in the inverter, or does it set itself up? I must say that having the Solar Edge transmitting data to the web is sounds interesting...

By the way, this was the Growatt Tech Support answer to my question "Our 2 roofs face in the same direction but they do NOT have the same angle - the 12 panels would be at 30% to the horizontal, and the 4 panels would be at 35% to the horizontal. Can we still use the 3600MTL wired 8+8?"

"5% should not be that much that affect the overall performance. In some instances 4 panels may be able to produce more that the 4 others, but limit their power production to the low ones. I am assuming this will be a 8+8 config using a 3600MTL".​

So if the extra for Solar Edge is too much, we just settle for the Growatt with 2 MPPTs wired 8 + 8, since that is the contract we have signed up to.
I just need to decide how much is too much... Answers on a postcard.

Perhaps you should look at the predicted generation of your options and look at the returns based on cost and monitoring facilities you require.

1. Growatt as above
2. 12 panel system with a single tracker inverter.
3. Solar edge.

 

[Gavin A]

Maybe you could say to them you are not happy with the equipment being installed
you want an power one inverter as you can alter the start up voltage on the mppt

I've just checked, and both inverters have the same MPPT lower voltage of 120V

120V simply isn't low enough for 4 x 30.5V panels, because as soon as the panels warm up even a little the voltage will go outside the MPPT voltage range and shut down that MPPT.

Combining the 4 panels on that roof with 1-4 from the other roof is the only viable option with this inverter (or power one / sma equivalents).

tbh there's not going to be a lot of difference between a 30 and 35 degree roof, and the dual MPPT will minimise this impact. It's not ideal, but then any losses from doing this are likely to be lower than the reduction in efficiency from swapping to a seperate smaller inverter for that roof, so I understand this companies reasoning.

They probably should have explained this better themselves though.

 

[juniperz]

I've just checked, and both inverters have the same MPPT lower voltage of 120V

120V simply isn't low enough for 4 x 30.5V panels, because as soon as the panels warm up even a little the voltage will go outside the MPPT voltage range and shut down that MPPT.

Combining the 4 panels on that roof with 1-4 from the other roof is the only viable option with this inverter (or power one / sma equivalents).

tbh there's not going to be a lot of difference between a 30 and 35 degree roof, and the dual MPPT will minimise this impact. It's not ideal, but then any losses from doing this are likely to be lower than the reduction in efficiency from swapping to a seperate smaller inverter for that roof, so I understand this companies reasoning.

They probably should have explained this better themselves though.

Thanks, though when you say this inverter, which did you mean??
Is this why 12 + 4 Physical but 8 + 8 Wired is best for the dual MPPT Growatt?

 

[wstevew]

You could probably get away with a 6 and a 10 string on a dual tracker to minimise losses, but still close to the lower end of the tracker voltage range.

 

[Gavin A]

growatt 3600MTL

I'd think 10 + 6 might be better in this situation to minimise the number of panels affected, but I don't know this inverter so there may be some reason why not.

 

[juniperz]

You could probably get away with a 6 and a 10 string on a dual tracker to minimise losses, but still close to the lower end of the tracker voltage range.

Even if split 12 panels at 30% to the horizontal, and 4 panels at 35% to the horizontal?

 

[wstevew]

4 panels at 35 and 2 panels at 30 wired in series to 1 string. Approximately 180v

Then 10 panels at 30 wired in series.

Each of the above to an isolator and its own tracker.

Losses minimal as you have 10 panels not affected by the pitch difference.

But the tracker on the inverter needs to be right for the string.voltage and current.

 

[wstevew]

Another possible alternative. Maybe someone knows.

Would 72 cell panels like the znshine have enough voltage for a string of 4 panels?

 

[babba]

Another possible alternative. Maybe someone knows.

Would 72 cell panels like the znshine have enough voltage for a string of 4 panels?

Even better get an installer who knows what they are doing. I dont understand how people can take such risks to save a few quid ????

 

[wstevew]

Even better get an installer who knows what they are doing. I dont understand how people can take such risks to save a few quid ????

Oh how hindsight is a wonderful thing.

 

[babba]

Oh how hindsight is a wonderful thing.

Is that what its called now ?

 

[Earthstore]

I do think Babba has a point, there have been so many threads recently where customers have come here for help because for whatever reason they have chosen an installer that is not competent, I have also noticed that the professionals are becoming less helpful, and I have to say I am included in this.
Maybe customers could choose more wisely, I know it can be difficult as it is quite technical, but I feel the public are buying on price only.
Remember, penny wise and pound foolish.

 

[SolarCity]

There does seem to be a lot of threads like this but I don't think it is fair to say to a customer "you are buying on price alone and you got what you deserved." We all know that paying more doesn't guarantee competence - we can all name firms which are useless yet charge ludicrous prices. As far as a customer is concerned, they see MCS and REAL badges and that should be enough.

My personal opinion is that training isn't good enough and the MCS isn't strict enough with regards to competence.

This is not the customer's fault.

 

[juniperz]

Even better get an installer who knows what they are doing. I dont understand how people can take such risks to save a few quid ????

I will try not to be offended :cool3: This wasn't about saving a few quid. I thought I had a competent installer, and signed a contract. I then chose to look at the installation half way through, and found a problem. They have offered to rectify their mistake (installing wrong inverter) and use fire retardant material for the board, so I can't void the contract (or whatever the expression is). The good people here on the forum have been extremely helpful while I try to get this sorted out. Without the internet I would have been stuffed.

 

[sedgy34]

When is your installation date