help please reduced output on hot days

[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.