Panel Performance Issue?

[lennyg]

I had 3.96Kw system installed along with a mastervolt K5500 inverter last November. We had various issues with performance and the system apparently tripping out the mains, which in the end was rectified by swapping to the non rcd side of my fuse board, but at the time, the electrician who came out to see us (the 4th different one in 4 visits) he told us that the input voltage into the inverter from the panels was 530V - the maximum input could be 600V, however the limit on its operating range was 450 per string. I am slightly lost with the next bit of information, however I understand that they split the array into 2 strings wheras previously it was a parallel configuration ??? I had an issue at the time that I could monitor 2 inputs into the invevrter and one was always generally showing an output of twice the other.

Today I look at the inverter for the first time in a couple of weeks, and with the sun at 90 degrees to the panel, i.e. full sun, blue sky, I am still getting a reading of nearly twice on one input compared to the other - the figures are in the region of Inout A 1950W Input B 1150 W. I know it seems obvious, but is there a problem and where is it likely to lie? A couple of panels not connected????

Thanks in advance for any help

 

[sedgy34]

Depends on how many modules are on each string your still generating 3kw from your system which is very good same as mine

 

[lennyg]

I understand that there are 8 panels on each string.

 

[Gavin A]

what panels, and what is the string voltage for each string?

 

[lennyg]

The panels are Solon blue 245w. As for string voltage, not sure really.

 

[Gavin A]

I don't know those inverters, but would be surprised if they didn't tell you what the operating voltage of each string was.

 

[poheZ]

It would be great to have all the details of your install. That model number for your inverter does not seem right either

If the installer has placed the pv circuit on a shared RCD then that is not a great sign!

 

[lennyg]

It would be great to have all the details of your install. That model number for your inverter does not seem right either

If the installer has placed the pv circuit on a shared RCD then that is not a great sign!

I got advice from this forum and everyone more or less said the same re the RCD, which was tripping out frequently. When the installer came out to try and rectify it I told him that I had a friend in the industry down south who had suggested not having it on a shared RCD - he started quoting 17th edition but then moved it anyway.

The Inverter is a strange one, it reports on its panel and was sold as a K5500, however when I use the mastervolt software, it shows it as 6500. I have 16 panels of Solon 245W Blue.

 

[poheZ]

Have you got a handover pack yet? All the system details would be in there

 

[Earthstore]

I can not find anything on a K5500 Inverter, are you sure it is not an XS?

 

[Del Boy]

Having looked at the specs... the XS6500 has a max input of 5500W and 600V.... so I think maybe it's this one. Also, I think the Solon Blue 245W is Solon Blue 230/07... handy how both of these are confusingly labelled!

Anyways, based off these assumptions, I plugged them into the MasterVolt tool and... you can have either:

a) 2 parallel strings of 8 panels (7 to 12 allowed, although 9 to 12 preferred) connected to one input or
b) A string of 8 panels connected to one input and a string of 8 panels connected to the other (5 to 13 allowed in this configuration, 9 to 12 preferred again)

I can't see how the DC input voltage could be 530V, the panels are 30V each, so this would imply a string size of 17 to 18 panels... as you have only 16 I can't see how this is possible!

The inverter is a little bit too big for your install. The tool is saying it's underdimensioned but acceptable. Seeing as one of the strings is much higher than the other I wouldn't worry about that at the moment.

Is there any shading (even something small like a tv aerial) on any of the panels on either string?

How did you monitor the different inputs to the inverter when they were parallel wired into one input?

 

[sedgy34]

I understand that there are 8 panels on each string.

im guessing you have a string of 10 and a string of 6, are both strings facing south or is a string south east??

 

[lennyg]

Having looked at the specs... the XS6500 has a max input of 5500W and 600V.... so I think maybe it's this one. Also, I think the Solon Blue 245W is Solon Blue 230/07... handy how both of these are confusingly labelled!

Anyways, based off these assumptions, I plugged them into the MasterVolt tool and... you can have either:Reply With Quote

a) 2 parallel strings of 8 panels (7 to 12 allowed, although 9 to 12 preferred) connected to one input or
b) A string of 8 panels connected to one input and a string of 8 panels connected to the other (5 to 13 allowed in this configuration, 9 to 12 preferred again)

I can't see how the DC input voltage could be 530V, the panels are 30V each, so this would imply a string size of 17 to 18 panels... as you have only 16 I can't see how this is possible!

The inverter is a little bit too big for your install. The tool is saying it's underdimensioned but acceptable. Seeing as one of the strings is much higher than the other I wouldn't worry about that at the moment.

Is there any shading (even something small like a tv aerial) on any of the panels on either string?

How did you monitor the different inputs to the inverter when they were parallel wired into one input?

I was going to call this post "Does my installer know what they are doing?" but didn't want to inflame anyone due to my rudimentary knowledge, however, I believe the assumptions that you make re the model & panels are correct. The electrician who did come out the 4th time did say 530V - and was explaining that by this figure the panels were performing well.

At the time of my reading, about 10am in the morning, the sun was at 40 degrees elevation, -60 degrees south, my roof pitch is 40 degrees. I can view the panels through a velux and they were 100% full sun.

My understanding of parallel & split strings is a little vague, so I just took at face value what the installers told me had happened. I took all my readings from the panel on the front of the inverter.

Both strings are on the same roof face -60

 

[Earthstore]

Lenneg, where do you live, maybe if you are close to one of the experts on here they may pop in and sort things out for you.
Just a thought.

 

[sedgy34]

I was going to call this post "Does my installer know what they are doing?" but didn't want to inflame anyone due to my rudimentary knowledge, however, I believe the assumptions that you make re the model & panels are correct. The electrician who did come out the 4th time did say 530V - and was explaining that by this figure the panels were performing well.

At the time of my reading, about 10am in the morning, the sun was at 40 degrees elevation, -60 degrees south, my roof pitch is 40 degrees. I can view the panels through a velux and they were 100% full sun.

My understanding of parallel & split strings is a little vague, so I just took at face value what the installers told me had happened. I took all my readings from the panel on the front of the inverter.

ingoth strings are on the same roof face -60

if you can touch the array from your velux the word "direct contact" springs to mind im assuming the array would have been earthed.

 

[lennyg]

Lenneg, where do you live, maybe if you are close to one of the experts on here they may pop in and sort things out for you.
Just a thought.

Between Prescot & St Helens Merseyside - Not looking for a freebie, I've paid the installers and they should really sort it. If I can glean information here then knowledge is power.

 

[lennyg]

if you can touch the array from your velux the word "direct contact" springs to mind im assuming the array would have been earthed.

Direct contact? I haven't touched them but could easily touch 2 maybe 3

 

[sedgy34]

Direct contact? I haven't touched them but could easily touch 2 maybe 3

just for peace of mind you might see an earth cable at the ac isolator too

 

[Del Boy]

im guessing you have a string of 10 and a string of 6

This makes more sense... it's almost perfectly a 5:8 ratio... a.k.a. 10:16, you should be getting very near to 1:1.

Not 100% sure what this means in real life terms, but MasterVolt tool says it's ok except the "orientation correction PV power"... I expect the 6 string will just run at a lower efficiency than 2 x 8 strings. Having said that the 10 string will be more efficient, but not enough to make up for it!

Pic of tool attached



Btw lennyg, didn't mean to shock you or potentially upset you with my initial findings, but wanted to show you what the tool was saying!

On a real positive note, the SOLON panels you have are really good!!! And you seem to have a good generation, having 2x8 should make it slightly more efficient, but the best thing is that you can easily spot problems over the long-term. The increase in efficiency is soooo little that you shouldn't be paying to do it but I think the installer should be putting it right for free anyways.

 

[lennyg]

Working all week so haven't been able to update. Yesterday again with full sun across all the panels my readings were c. 1900w on one string and 1100w on the other. The voltages at both were 325v & 140v respectively.

To confirm my spec, the master log software reports it as an xs6500 inverter and the panels are supposed to be Solon 245w of which I have 16.

Do my figures point to anything other than a difference in the amount of panels per string and if that is the only issue then at what point would I expect output greater than 3kw?

 

[Gavin A]

To me that looks from the outputs like they've run it in a string of 10 panels and a string of 6 panels, though the voltages more suggest 11 and 5 - is the bigger portion of the array shaded at all?

Both configurations would be within the range of the inverter, though I doubt it'd be operating very efficiently as it's massively over specced, which could partially explain the lower outputs.

Either way, it's clear that it's not 8 panels on each.

I'm assuming the voltage readings were taken from the inverter when it was operating?

 

[lennyg]

To me that looks from the outputs like they've run it in a string of 10 panels and a string of 6 panels, though the voltages more suggest 11 and 5 - is the bigger portion of the array shaded at all?

Both configurations would be within the range of the inverter, though I doubt it'd be operating very efficiently as it's massively over specced, which could partially explain the lower outputs.

Either way, it's clear that it's not 8 panels on each.

I'm assuming the voltage readings were taken from the inverter when it was operating?

Thanks for your reply - the array is not shaded at all when the readings were taken - the readings were in full sun. How much overspecced is the inverter and how much am I losing because of such?

 

[moggy1968]

How much overspecced is the inverter and how much am I losing because of such?

massively overspecced. I would use a 3.6kWinverter, although opinions vary

 

[lennyg]

For those not necessarily wanting to read the whole thread, my issue is that my 4kw system with 2 strings is producing max 3kw with one string producing about 1900w and the other 1100w all in unshaded direct sunlight, with the voltage ratios being the same (roughly 2:1) The theory is that the strings are split 10/6 however....

An interesting (or maybe not) further piece of information - This morning we had a very bright morning but with diffused high cloud so the panels were receiving a lot of light but not direct sunlight. Taking readings from the inverter, both strings were performing similarly producing about 500W each and similar voltages on both strings - this seems tome to negate previous posts of the array being split 10/6 as I would expect the ratio between the strings to be the same.