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.

 

[billybee]

its not a slate roof its a compisite tile, pined at the front of each tile so they carnt be lifted up.

 

[billybee]

no shading at all from the mains cables, its just the angle of the pic there agood 8 to 10 feet from the roof and not much higher the sun wood have to rise direct south and by the time it got over the houses in front the shadow would be on the wall not the roof.

 

[Worcester]

The power cables fix to below the eaves so unless they go up at 20+ degrees, they should be OK,

Here's an interesting comaprison for you from two other DH postcodes Compare Multiple Systems | Normalised Energy

Looks like you guys up North have been having sunnier weather than us in the midlands as well!

 

[billybee]

And is that a loose / unfixed DC cable I can see just to the left side of the right hand velux? yes it is theres a lot of loose hanging cables under the panels

Those aren't your (unsecured) cables coming down on the very right hand side on next-doors roof are they? no next doors areals my cables go into the loft under the bottom right panel

​

 

[billybee]

Home Solar Durham is a diffrent orintation 2 mine south west.the other system is the main one i compaire with as he's quite close to me and very similar in other asspects.

 

[Gavin A]

personally I'd stick a harness on and go out of the skylights, using the top of the bottom row to stand on and swap the cables around.

what's the chances of their spark having or being trained for a harness though?

 

[billybee]

lol it have to be a pritty thin and small lecky to fit through one of those windows lol

 

[Earthstore]

Fault list so far in your system;
Hanger bolts ( not recommended for slate)
DC cables not secured
strings wired incorrectly
inverter boxed in
not the best panels
can not see any earth cables on array ( legal requirement with velux windows)
I am sure there many more, I feel you did not choose your installer wisely, I am sorry, but I do not have the answers for you to correct all of this.

 

[billybee]

Hanger bolts ( not recommended for slate) not slate compisite tile carnt be lifted for hooks
DC cables not secured, there is loose cable but they are rapped round the brackets
strings wired incorrectly. yes could be right but by some posts on here not the only installer to do this
not the best panels, i ask for them due to price and gurentees so carnt blame the installer and on mixed days they seem alright push over 3kw out and once the strings are sorted who knows.
can not see any earth cables on array ( legal requirement with velocity windows) carnt comment on that one as i dont know but he new enough that he couldnt cover them as the open so may have earths,
inverter boxed in, i did this to protect the wires from my daughters ferret, im already planing this week to make some smaller that just covers the wires and not the inverter so you carnt blame the installer for that one.
i went online on a site that recommends local installers and to be hounest one was hundreds of miles away and used contractors, one did so much for you that no other installer did and promised after 2 hours of explaning what the did i asked how the fixed to compisite tiles and didnt have a clue. the other two were simler apart from one had only been fitting a year. the other unlike the other 3 didnt try and tell me that i would get 3000kws a year out of a 3kw system and in the end gave me the inverter i wanted the panels i asked for at the best price.

​

 

[jason121]

Fault list so far in your system;
Hanger bolts ( not recommended for slate)
DC cables not secured
strings wired incorrectly
inverter boxed in
not the best panels
can not see any earth cables on array ( legal requirement with velux windows)
I am sure there many more, I feel you did not choose your installer wisely, I am sorry, but I do not have the answers for you to correct all of this.

why are they not the best panels and can you show the regs on velux windows earthing arrangement the world has gone mad with bond this bond that.

 

[Gavin A]

lol it have to be a pritty thin and small lecky to fit through one of those windows lol

the windows should be easily removable, there's a catch on each side, then you can just slot them out.

 

[Gavin A]

why are they not the best panels and can you show the regs on velux windows earthing arrangement the world has gone mad with bond this bond that.

there really is only any need to bond them if they are also an extraneous conductive part - ie if there is already conductivity to earth from the frame, which nobody can know for sure unless they're tested, otherwise no bonding is needed.

the problem is that the old guidance says you must bond the frame if it's a TL inverter, but that's 6 years out of date, and all TL inverters now come with inbuilt all pole RCD's that didn't exist back then. The new guidance that was supposed to be published last year says only bond if it's an extraneous conductive part and in the equipotential zone, but it's still not officially been published, so it's all a bit of a moot point about which guidance to follow.

We've been following the revised guidance since last Autumn, as it's the only version of the guidance that makes any sense, and the people who write that section of the guidance have stated that this is going to be the version of the guidance when it eventually gets published... no point just blindly following 6 year old guidance when the technology has changed massively since then.

 

[Earthstore]

If you think bringing 300-600DC into your daughters bedroom, along with her pet ferret is good practise, and you feel your installer has completed an excellent install, then there is nothing more I will add to this thread.

Maybe the Earthing of the array is a contentious point at the moment, if you can touch the array from a velux than there is potential, so for the small cost involved earthing would be good practice.

With these points made I am done with this thread.

 

[provr6]

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.

Slightly OT, but is the 200mm requirement before you need planning permission measured from the roof to the underside or top surface of the panel?

@billybee, slates cannot be lifted either to install brackets, they have to be ripped out, slots cut out, flashing installed and secured with hooks. Yours look like Eternit or silimar which tbh is the same principle as slate. The general concensus is that hanger bolts are not the best method for fixing to slate, primarily because they involve drilling a hole through every lap of slate which could lead to water ingress if over time the neoprene washer perishes or the nut beomes loose. They are designed for corrugated fibre roofs. I did try an experiment by fixing a hanger bolt to slate and running constant water over it. It didn't leak but wouldn't want to risk it over 25 years.

 

[moggy1968]

it's a planning requirement, 200mm from roof surface to top face of panels I beleieve.

 

[billybee]

Slightly OT, but is the 200mm requirement before you need planning permission measured from the roof to the underside or top surface of the panel?

@billybee, slates cannot be lifted either to install brackets, they have to be ripped out, slots cut out, flashing installed and secured with hooks. Yours look like Eternit or silimar which tbh is the same principle as slate. The general concensus is that hanger bolts are not the best method for fixing to slate, primarily because they involve drilling a hole through every lap of slate which could lead to water ingress if over time the neoprene washer perishes or the nut beomes loose. They are designed for corrugated fibre roofs. I did try an experiment by fixing a hanger bolt to slate and running constant water over it. It didn't leak but wouldn't want to risk it over 25 years.

i beleve my roof is corrugated fibre boards, i'm not a roofer but could see what the fitted and spook a to them about it and its not slate. as to the hight i can only reach the middle panel thats on its own and its 205 to 207 mm high to the top of the panel but i sopose if needed be theres about 30mm of adjustment on the bolts so the could be lowered slightly. i'm not a fitter and wouldnt no whats best with theses type of roof boards but at the time of fitting the roof was 6 weeks old and i'm happy with the system they used, yes i relized having rubber seals on the roof long term has some risk but its the chance you have to take.

anyway the electricans coming thurs or frid to make changes and i'm going to speak to him about the loose cable. and the best option on restringing, i spoke to my son inlaw whos a cooling and heating engernier and the first think he said was this wasnt he field thou he had done some bits on inverters and oftern worked with DC. he looked at the figures and understands why it would be better with one string. but when we spoke about linking outside the inverter he couldnt see what diffrence it would make to linking in the inverter. yes on the roof due to resistance there could be a saving on vaultage loose. but saving 4 or 5 feet of wire inside would be normanal. he did say though that you lads will know more than him and there could be other considerations for joining the strings before they hit the inverter.

thanks all

 

[scottliv]

What was the outcome on your string reconfiguration?

 

[billybee]

had it done on friday, restringed outside the inverter. problem is the desktop i have only saves watts output and as everyday is diffrent i have nothing apart from the systems ive been compairing with to compair with still.
no major signs of improvement yet. out of the four days since i can only count 3 as his system was down so useing the other 3 i'm looking at around 11% diffence in performance may and june were both 9%. but to early yet as there can be big diffrence over a week so will have to give it a couple at least and wait for some very hot days. but at the moment theres nothing jumping out. i will add that frid sat and sunday i had peaks of over 3200 on all three days. but i'll update results in a couple of weeks thanks

 

[billybee]

hi all just an update, been a few weeks know since the resring changes, that is the change in the inverter. as the only figures i have to compaire with is the ones i already was useing ive continued down that line. as there can be large diffrences from week to week im doing the comparison of may and june which i had and i'm happy to say at the moment i'm seeing around 3% improvement in the comparisons upto date this month.

so thanks for all of the help as some improvement is better than nothing. i could restring fully on the roof and gane somemore but the cost will probably out way the savings. but thanks all again for the help.

i havnt had a very hot day since the restring was completed so carnt comment on hot days yet, i have had a day where the panel reached 36c for a few hours and didnt experance any drop in out put still hit 3kw on that day.

 

[moggy1968]

june, month of the longest day?

 

[billybee]

well factoring that maybe a little more than 3% then. but not really as i'm compairing efficiency and if i have 10 minutes less daylight from june to july so does the other system. i canrt compaire each days outputs as no 2 days are the same. that last week in may i never saw a clood for 4 days and still daily outputs were diffrent. useing pv output in may and june the diffrence between the 2 sytems was 9% in july upto date 5.5% so looks like an improvement.

 

[moggy1968]

that hits the nail on the head. To draw real conclusions unless there are vast differences is extremely difficult. There are simply too many variables. Even year on year, this may wouldn't compare with the previous may and may not compare with next may because of the unusual weather.