Please advice 16 or 12 panels to achieve close to 4 kW PV System

[Gavin A]

indeed. they're also a pretty pointless way of spending an extra grand on a system for most people.

The full scan function ensures that the inverter doesn't get stuck on a false voltage peak as the shading impacts on more strings of cells, and the optimum voltage moves to a point where the bypass diodes have cut out the shaded strings.

The new OptiTrac Global Peak makes sure that partially shaded solar power plants operate efficiently

 

[rdo]

Quite a feature. It's now a bit too late to switch to SMA, but although helpful, it won't benefit me that massively as it won't have such a big impact on my system I believe, because:

I've taken this photo yesterday at 11:15am. The shading edge is going down gradually, but a couple of hours later the sun hides completely behind another building (a bit of this approaching shadow can be seen close to the left edge of the photo) and will keep hiding like that until I think February, when it will stay higher above the horizon after that until November. Am I right thinking that there should be one string of six panels closer to the top of the roof and the second 6x string just beneath?

 

[The Solar King]

Several inverters have a full scan feature, or something very similar that does this without altering the settings. With regard to shading at this time of year, I wouldn't get too hung up about it. There is so little daylight as too make little difference.

If a proposed installation is properly modelled using simulation software, the true effects and impact on output quickly become clear.

 

[bath_ed]

Has anyone started to use Sunedison panels. They give a 25 year product warranty. Range from 275watt to 285 watt

I see they do up to 330W, but they are standard efficiency so are larger than the 330W high efficiency panels. Might be cheaper to use fewer larger panels, but you won't be able to squeeze the extra wattage onto small roofs like the high efficiency panels can.

Ed