One string suddenly seems to have reduced output

[DickiePhitt]

On my newly commissioned system - 16x Sanyo HIT240 and SMA 4000TL - all has been going well, even to the extent of seeing over 4kW on the inverter dispay a couple of times yesterday and this morning. This afternoon, in good sunlight, I notice one of the strings will never get above 1.8A (about 380v) whereas the other one is regularly at 4 or 5A (around 330v). As a result I've not seen any output above 2.8kW.
The only shading is from the handrail of the scaffolding which is awaiting dismantling, otherwise the panels are S facing with no shade. Can a small amount of shading on about 3 panels cause this sort of differential or is it someone more serious?
Obviously I'm taking it up with the installer but this forum has been a font of wisdom in the past and I'd welcome any thoughts.

 

[jerriais]

Yes, I'd say that solid shading from a handrail would certainly cause losses of about that amount. I'd wait and check again after the scaffolding is down.

 

[Swithenbanks]

I'd check the results as soon as the offending handrail has been dismantled, if there is still an issue then you need to raise it asap

Nothing else that could be shading them I assume from your original post?

Regards

Ewan

 

[DickiePhitt]

There is a handrail on the scaffolding parallel with the line of the eve. This means that in the afternoon 3 PV panels have a neat line of shadow down their length about the width of an 'element'. Some other scaffold poles casting a little diagonal shadow, otherwise nothing. Will be amazed if this is indeed making the string operate at about 1/3 of the current of its partner.

 

[SolarCity]

Are you sure the strings have equal amount of panels on them?

EDIT: Oops, re-read the OP. I've had a long day. It seems to me that the handrail is the most likely culprit.

 

[DickiePhitt]

Oh yeah. 2x8. When commissioned & over the weekend everything seemed to be balanced whenever I checked. Seems to be a marked difference only this afternoon. Maybe because its first afternoon there's been loads of sun but 3x difference just seemed excessive.

 

[Graeme Harrold]

Highlights the problem with shading. to you it looks like a small shadow, and look what its done....Keep an eye on it as the scaffold is being dismantled, even go as far as setting up a laptop with Sunny Explored to watch as the rails are removed.