help please reduced output on hot days

[Gavin A]

so are you saying Gavin that a 3kw install on a power one split 50/50 is not very suitable ?

no. I'm saying that this 3kW installation on 50/50 split on this inverter isn't very suitable, and should only be done if on different roof faces or there was significant shading to one of the strings that the bypass diodes and shading function couldn't sort out well enough.

if the installer had used 50V panels, then 6 of these per side would be much closer to the peak efficiency point of the inverter than using 6 x 30V panels. Alternatively they could have used 8 x 190Wp 36V panels etc.

using the 30V panels though single string is the only way to get the most out of the inverter.

 

[billybee]

so Gavin do you think it would be worthwhile when the electrician comes to put in the link wires, would it be better for me just asking him to do this possitive to negitive thingy and converting totally to one string straight away. thanks

 

[Gavin A]

so Gavin do you think it would be worthwhile when the electrician comes to put in the link wires, would it be better for me just asking him to do this possitive to negitive thingy and converting totally to one string straight away. thanks

Presuming the shading is as minimal as you say, I'd just ask him to wire it into a single string of 12 panels in series.

Only if he says he can't get on the roof to do it would I mention the idea of him doing it via the cables in the loft / isolators, as it may well be simple enough to do with a ladder / roof ladder on the actual roof, and this is the best option.

 

[billybee]

when i spoke to the installer about the bigger inverter he did some checking and said he would recommend that with a larger inverter he would recommend going to one string. he said then that to do this i would have to put the scaffolding beack up. the way the panels are on the roof theres nowhere for a roof ladder so i doubt he would go for the ladder idea. i had the back of my roof repaired 2 years ago (got a new roof now) and the roofer at the time wouldnt go on the front without scaffold and the electric lines sleeving. so without a lot of expense i think your internal idea may be best.

im just of southish facing bottom row is 6 vertical panels (1 string) next row up is one panel vertical then the top row is 5 vertical i think the chimly witch i think on the east end is about 3 feet hight and may or may not shade the top of the end panel i doubt it ever casts enough shadow to hit more than one panel or a full panel. to be hounest i dont think i have any shading looking at where the sun rises i think its just the hight diffrence in the panels and its only happering very earley morning when the suns very low.

 

[Worcester]

I've just run the system through Power-One's sizing and design tool and it recommends installing these as a single string of 12.

Since all the wring is in place, (the DC losses are minimal) then it would be fairly easy to reconfigure it as a single string of 12 at the inverter end.

If that works out, then it would be simple enough to go into the loft and just join string 2 to the end of string 1, the length of cable coming into and out of the loft would be minimal.

That change over is very simple.

 

[Gavin A]

a picture of the array would work wonders tbh

 

[billybee]

i will have a go

 

[billybee]

hope this helps

 

[Gavin A]

erm, these are A-Sun panels yes?

they only seem to have 240Wp full black panels listed on their website, which might explain your reduced output levels - on top of everything else discussed.

Download base A-SUNENERGY.COM

 

[billybee]

http://www.a-sun.co.uk/download/ASUN250-MB_EN.pdf

 

[billybee]

A-sun | Products

 

[Gavin A]

ok, sorry, I'm not sure why their .com website doesn't list them.

 

[billybee]

cos there crap lol essecally if the suns shinning

 

[jason121]

PV SOL produces a good output for ASUN, on paper look good

 

[billybee]

on the right day there peaks are impressive and i supose add that to an inverter that can run above its soposed max output you do hit over and above 3kws but they seem to be affected alot more than other panels by heat witch to my dismay i didnt know anything about. but once the string issue is sorted i should see some improvement on out put. i think part of my issue was to do with lack of info i expected after i got my first big day 17kw and it was pritty mixed clould and sun. i was expecting well into the 20kw's on full sunny days and when it didnt happen i was very suprised.

 

[Worcester]

A-Sun probably don't nescesarrily list them becasue they don't make them - they contract it all out, just read how they word it on their websites very carefully

 

[jason121]

i wonder if because all black panels, someone did say the black panels are affected more by heat

 

[Worcester]

Those panles look mighty high off the the roof - AHA they used hanger bolts on a slate roof... thread goes of at a tangent, think I'll shut up ...

 

[Worcester]

And is that a loose / unfixed DC cable I can see just to the left side of the right hand velux?

Those aren't your (unsecured) cables coming down on the very right hand side on next-doors roof are they?

 

[moggy1968]

it looks to me as though you will almost certainly get some shading off the mains cables (with the shrouds off!)
Those look as though they could well be more than 200mm off the roof.