Question on solar PV chains

[TransAmDan]

Okay, I have a split system. I have 6 panes facing SE and 10 panels facing SW.
The inverter is a Growatt 3600mtl
When the Solar installation team connected it up, they said they would balance it out and have 8 panels per chain. So the 6 facing SE are chained to 2 facing SE.
So early mornings two of the panels are in the shade, would this bring down the efficiency of the 6 facing SE? I know if part of a panel is shaded it brings down the efficiency of that panel, but what if one panel in a chain is shaded, does it bring down the rest of the chain?

This was an install done by someone else, just wondered if it was wired correctly? I do seem to be generating less than someone within a few miles and they have a smaller system, although they have all their panels facing south.

[inMichigan]

Hello,

I looked at the manual for device. http://www.growatt.com/UpLoadFiles/2...1410390973.pdf I see in several places mentioned it has MPPT Channel A and B. I would expect all the "A" panels to be on the same roof direction, and all of the "B" to be on the other roof. However, I think from your description of the numbers, you're saying they're mixed up. I would not think that would work well.

You need to mention what kind of solar panels you have. This model is limited to 3600W in total, and, each MPPT channel is limited to 10A.

inMichigan

[TransAmDan]

Thanks for the reply.
I have 16 x 250w panels. They are called EVO+10, datasheet:- http://www.evolutionsolarpanels.co.u...AmeriSolar.pdf

So 8 panels are on channel A, and 8 panels on channel B.
Trouble is they are spread across two roofs. Channel B is fine as they are all on the same roof(south west), but channel A has 6 panels facing south east and the other 2 are on the same face as the channel B panels.

So Im not sure channel A will be working its best as buring the morning two if the panels are not getting as much sun as the rest. The panels are meant to be wide angle. Looking at my stats in Generaytor mine are a lot lower than people with a similar sized array.

So I wanted to get a good definition on the internet, that all panels on the same channel should be on the same face for best efficiency, or if one panel is shaded then all other panels in that string are reduced efficiency?. I got a Solar company to come and do the entire job, they selected the panels and inverter, chose quantity for each roof, limited to a max of 4kWh (government incentive in the UK to stay under 4kWh as you get paid more per unit of energy generated). So if there is something incorrect with the install I would need to email them explaining why I think it is wrong, and if they say it isn't wrong I have some info to back me up.

[Raul]

You are right to believe Chanel A will suffer from the 2 shaded panels . You can have the 6 on A and 10 on B and that will work . Your afternoon production will always be stronger than mornings . The hole meaning for to MPTT inputs is to split 2 separate orientations .

[TransAmDan]

You are right to believe Chanel A will suffer from the 2 shaded panels . You can have the 6 on A and 10 on B and that will work . Your afternoon production will always be stronger than mornings . The hole meaning for to MPTT inputs is to split 2 separate orientations .

I may be able to adjust the wiring myself, I work with electronics and work with high DC currents at work. Its just solar panels I'm new to. I can do the work at night.

Looking at the panels, I guess the addition of each panel gives you higher voltage. So 10 x panels at 27.9V will make under 300V and as the inverter can handle between 100V and 600V then its not beyond the inverters capability. Max of 10A current per input, I guess it will be below that?

[Raul]

The inverter is capable to take the hole 16 in one string easy, so 10 panels will be well under its limit. Before you pull any mc4 out to open a string I suggest you turn off both dc breakers first . That way there is no load to the string and no arching .

[TransAmDan]

The inverter is capable to take the hole 16 in one string easy, so 10 panels will be well under its limit. Before you pull any mc4 out to open a string I suggest you turn off both dc breakers first . That way there is no load to the string and no arching .

Brilliant, thanks for the info. you have been very helpful, much appreciated.

[bcroe]

The inverter is capable to take the hole 16 in one string easy, so 10 panels will be well under its limit. Before you pull any mc4 out to open a string I suggest you turn off both dc breakers first . That way there is no load to the string and no arching .

I shut down by opening the AC disconnect first; this stopes any DC current flow. Then I open
the DC disconnect. However, in reality I avoid shutting down a system in daylight all together.
If something must be fixed, I might shut everything down at night, then fix it the next day. I
am less hesitant to TURN ON the DC, then the AC days. Bruce Roe

[Wy_White_Wolf]

I may be able to adjust the wiring myself, I work with electronics and work with high DC currents at work. Its just solar panels I'm new to. I can do the work at night.

Looking at the panels, I guess the addition of each panel gives you higher voltage. So 10 x panels at 27.9V will make under 300V and as the inverter can handle between 100V and 600V then its not beyond the inverters capability. Max of 10A current per input, I guess it will be below that?

Is that VOC or VMP?

You need to use VOC for calculating maximum string voltage and then do a temperature adjustment.

You also need to verify if the 6 panel string will be enough to meet the minimum voltage needed for the inverter. That calculation would use VMP.

WWW

[TransAmDan]

Is that VOC or VMP?

You need to use VOC for calculating maximum string voltage and then do a temperature adjustment.

You also need to verify if the 6 panel string will be enough to meet the minimum voltage needed for the inverter. That calculation would use VMP.

WWW

Thanks for the info.

VOC is 35.2V
VMP is 27.9V

10 x 35.2V is under 600V(inverter max) so 10 on a string is okay.
6 x 27.9V is 167V which is greater than 100V (minimum for inverter)

It looks like its all good for the change over.

[TransAmDan]

Came across this on page 24 of the inverter manual.
This seems to be implying to get the same amount of panels on each string. I'm hoping this is just a suggestion, and that 10 panels on one string with 6 panels on the other string is still okay.

[TransAmDan]

Well I'm glad I took a look at the wiring.

I thought the first chain was 6 panels on the front of the house was wired to two on the side. The second chain was 8 on the side.

Measured the off load voltages. One pair was 67V, the other pair was 420V. Very odd indeed. These voltages indicate 2 panels on their own and 14 panels on the other chain.

Rearranged them to be correct now, voltage measures just before the sun was too weak, about 170V on one chain and 280V on the other, this works out about right for 6 panels on one chain and 10 on the other. So as successful modification.

It would have been fairly balanced with 8 panels on each chain apart from the mix of direction, but to have 2 panels and 14 panels, is just soo far out. I can see what they have done, as 6 wires come in, they got got two pairs muddled up. Good job they got the pos and neg correct.

Well I should get better solar results now with all panels on the front of the house wired to one chain and all panels on the side wired to the other chain.

[inMichigan]

Came across this on page 24 of the inverter manual.
This seems to be implying to get the same amount of panels on each string. I'm hoping this is just a suggestion, and that 10 panels on one string with 6 panels on the other string is still okay.

I would also interpret this diagram as 'all 6 must be facing the same sun together' and 'the other 10 must all be facing the same direction as their group'. Is that how you're wired?

inMichigan

[TransAmDan]

I would also interpret this diagram as 'all 6 must be facing the same sun together' and 'the other 10 must all be facing the same direction as their group'. Is that how you're wired?

inMichigan

Thanks, yes that is how they are wired now. I have posted what I've done, just waiting approval by admin.
I'm happier now that 6 are facing one way are on one string and the other string contains 10 panels facing a different way.

Thanks for everyone's comments on this, its great to bounce ideas around.