Correct Inverter Choice?

jupestar · Mar 27, 2012

interesting post and it's a tough call with out seeing the job it's hard to know. power one, or solar edge both good options. if you need a scaffold might as well do the solar edge, but without seeing it istough.

i will add this, my dad had one of the first fit eligible installs. and had a steca inverter which lasted less than a year, it completly stopped working. the installer replaced it with a fronius but changed it to single string mppt (despite there being a big chimney right in the middle). i suggested he complain that they changed a dual steca to a single mppt which was not suitable for his install. he did and now has a power one. he's been monitoring it a bit,not crazy, but just keeping an eye, and he swears blind he got best production from his fronius.... and looking as his scribblings, hes actually right. the higher voltage by having all the panels on one string was actually better.... no real point to that story other than you can do all the computer simulations you want in real life it doesn't always work out.

Glen Powell · Mar 27, 2012

I would check out the total tech spec of the optimum start up wattage before choosing solar edge, you may not be happy with the results, see if you can get a sale or return deal.

LightGEN · Mar 31, 2012

I haven't checked to see if the panels already installed are in their compatibillity list, but how about Enecsys Micro-Inverters? Enecsys had some production issues last year but these seem to have been resolved - we installed a system, based on these, at the beginning of December and we're happy with it so far.
SMA is launching a micro-inverter some time soon.

Dave-geo · Apr 1, 2012

A further update!

Since connected to one string to increase the voltage to suit the MPPT the increase in performance has been tremendous. The voltage is now fine at all times even when shading occurs however we still need to decide on a permanent solution.

I am really surprised at the problem the shading causes. I have placed below a picture of the complete roof and chimney to show our system. It is 14 Bosch 245w panels on a 50° roof facing due South.

[ElectriciansForums.net] Correct Inverter Choice?

With the three panels shaded as shown below the system will only generate 0.35Kwh

As soon as we reach the stage of shading shown below (less than 10 minutes after the previous photo) the generation shoots up to 1.95Kwh. Does that seem correct? I have been able to replicate this on every sunny day so it is not a one off occurrence.

There is a further progressive increase to a peak around solar noon of 2.85Kwh as the shade clears the final panel.

Is it possible to use any computer modelling to see which panels should be put in a separate string? It is ok looking at them now but more difficult for me to predict what will happen at other times of the year.

We are also still looking at SolarEdge as a way to overcome the problem but are concerned at the point Glen made earlier regarding the start-up wattage, I haven’t been able to find much information on this.

Any further help or comments would be really appreciated.

LightGEN · Apr 1, 2012

I've now checked and see four, apparently different, Bosch 245W panels listed in the Enecsys compatability list. All are model number c-Si M60 - M245 3BB followed by either 11, 13, 14 or 17 to differentiate the four different models.

Gary K · Apr 1, 2012

Do Bosch allow clamping on the short side? If not, I suggest you get your installer do do the job correctly so that you do not have warranty issues and whilst he has got the scaffold up( at his cost), you can fit the micro inverters as required.

Dave-geo · Apr 4, 2012

I have checked the specification sheet and as Gary says clamping is not allowed on the short side for these panels. What would be the reason for this and is it really something that should be corrected? To alter this now would be a large job and mean ripping the roof apart again which I am not keen on.

SolarCity · Apr 4, 2012

The reason is generally that the frame hasn't been designed to take the flex when clamped on the short sides. Some manufacturers have a stronger frame and they have passed their panels to be installed in this way - In reality, I doubt that you would have too much issue. However, I would say that if you left them this way then your warranty is effectively over.

Earthstore · Apr 4, 2012

I believe it is called fiscal loadings, ie will the panel break when it is covered with snow, also as pointed out it may well flex with the wind and break anyway.

The shading is not good to be honest, but as the sun gets higher in the sky the effects will be less, of course they will be worse all winter.
I hope this helps.

Gary K · Apr 4, 2012

I'm sure its a daft question but why couldn't you put the 2 panels that are on the right, to the right of the chimney under the solar water panels? The shading would then effect fewer panels as the shade obviously can't be to the left and right of the chimney at the same time.

Dave-geo · Apr 4, 2012

Gary K said:
I'm sure its a daft question but why couldn't you put the 2 panels that are on the right, to the right of the chimney under the solar water panels? The shading would then effect fewer panels as the shade obviously can't be to the left and right of the chimney at the same time.

Gary, Thanks for your reply. I had thought aout that but as the roof faces Due South this might give shading to these panels in the afternoon/evening. I could then end up with a problem at both ends of the day!

The installer is calling around tomorrow morning so I am hopeful of working out a solution then. I will let you all know how we get on.

Dave-geo · Apr 13, 2012

I am still working with the installer to find a satisfactory solution to the shading problem, looks like we are going down the SolarEdge route.

I am not sure what to do regarding the panels being clamped on the short side. I really don’t want my roof ripped apart again! Would it be possible to add additional rails vertically attached to the horizontal rails which would then allow the panels to be clamped in the correct positions? This would seem to be an easy and cost effective solution.

Any comments good or bad would be appreciated.

SolarCity · Apr 13, 2012

Dave-geo said:
I am still working with the installer to find a satisfactory solution to the shading problem, looks like we are going down the SolarEdge route.

I am not sure what to do regarding the panels being clamped on the short side. I really don’t want my roof ripped apart again! Would it be possible to add additional rails vertically attached to the horizontal rails which would then allow the panels to be clamped in the correct positions? This would seem to be an easy and cost effective solution.

Any comments good or bad would be appreciated.

Adding vertical rails is what we do on our installs. I don't know if your mounting system allows it but I'd be surprised if it doesn't. What is the make?

Dave-geo · Apr 13, 2012

Thanks for the reply Solar City.

I don't know the make but it is 40mm x 40mm and I have put a photo below of it. Do you reognise it?

Thanks for your help.

SolarCity · Apr 13, 2012

I could be wrong but that looks like Schuco to me. If it is then you will have no problem going for the cruciform method.

Correct Inverter Choice?

jupestar

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Glen Powell

LightGEN

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Dave-geo

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LightGEN

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Gary K

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Dave-geo

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SolarCity

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Earthstore

Gary K

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Dave-geo

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Dave-geo

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SolarCity

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Dave-geo

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SolarCity

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