System peak

[crazygraham]

Hi all just a quick question.

I have a 6kw east west split on a 30• roof with two SMA-3000 inverters it's been in for about two weeks now. There has been some great days but have never seen either system go over the 2kw.
In total it has been over the 2kw but when looking at the east side when the sun is direct and on it can't seem to go above the 2kw and the west facing system is the same.

However since the inverter I got given was second hand it had data on it from whoever had it b4 me and rite up to a week b4 it was installed in my house it was peaking at 3kw at lots of points through the day

I would have thought it should be doing the same for me.

How can I know that everything is working ok is there any tests I can do I know the voltage is 380apx so 12 panels sharp 250w that works out about 30v each panel

Just can't see why they won't hit peak I just need to see it say 3GS to know it's all good

I'm in Bangor northern Ireland

Thanks for helping.

 

[dansk]

Hi Craztgraham, ive been following your problems, its a common mis conception about solar systems peaking, amd your questions are typical of that mis understanding. Solar systems dont always peak, it takes a number of circumstances in tandam to create peak generation, roof angle, time of yehar, tempreture, angle to the sun, irradiance to name a few.

The second hand inverter could have been on a south facing roof with 4kwp of panels connected for example, so to look at historic data without knowing anything about the set up is like saying my last car went 100mph but my new car will only do 60mph, what you forget is the last car had a turbo and the new doesnt, its not a comparison.

I would advice against testing the strings directly ad they carry dangerous DC voltage, so unless your trained in DC i would leave that alone.

I feel your paranoid about yuor system becuase of the problems you had and i can understand that.

East west systems dont generally peak as such, the east array suffers from low sun in a morning, and by 11 am the sun is passing over so the panels never really benefit from the direct sunlight.

Thats why having a south facing aspect is prime location.

hope this helps.

 

[crazygraham]

Hi thanks fir the replay. I think that I am just paranoid with it would just love to see each inverter hit it's peak at 3kw to put my mind to rest at the moment the sun us belting down not a cloud in the sky and the east inverter is sitting at 1.66kw I would have expected it to be a bit higher

 

[infinity]

1.66KW does seem a little low if the suns on it, but as Dansk says so many factors that can decide on the output. Best thing to do is contact installer get them out to check its all ok!

 

[FB.]

East/West split is going to suffer in winter time as the sun never managed to shine straight at the panels, and the sun will only be in one array's arc at any one time.
By the time the sun is at its highest and strongest, the sun is completely off to the side of East or West-facing panels, causing considerable reflection and angular losses.

So although the peak power sounds a bit low (and perhaps ask your installer to take a look of you're concerned), each array in direct sun shining straight at the panels would only achieve about 3kw each - and we're now well off peak sun.
In sunny summer mornings the East-facing panels will reach full capacity.

At the moment, my 3.7kW, SE-facing system (slightly better facing than East) only manages to hit three-quarters of maximum capacity mid-morning, and in the afternoons is less than a quarter capacity.
My daily generation in days with brilliant full sunshine is something like:

8am: 1kW
9am: 2kW
10am: 2.5kW
11am: 2.75kW (three-quarter potential)
12noon: 2.5kW
1pm: 2kW
2pm: 1.5kW
3pm: 1kW
4pm: 0.5kW
5pm: 0.1kW

So if I had a SE/SW split, at even the best moments of the day, I'd have one array at most at 75% of capacity, and ther other at about 25% capacity.

So achieving a maximum of 2kW at peak, from a 3kW East-facing array at this time of year isn't surprising.

 

[crazygraham]

hi there thanks for the info i seem to be also getting just under 3/4 of the ratted power so that will help put my mine to rest a bit i think i was wanting to see 3kw on the system on a good day.

however today when the sun went round to the east side i noticed that the west side was doing better than the east ?? got me thinking rire away that there had to be somthing wrong, So up to the inverter i went with multi meter in hand and found only one string to have any voltage 210v the other 0v !! so i went into the DC switch and found this SEE PHOTO like really how ! do u walk away from this ?

so i fixed it and made the panels into one string as the higher voltage will have less power loss,
he has used 4mm dc cable for the install if i was to upgrade it 6mm or 8mm would this help reduce the loss and improve the power output ?
Also From the inverter it could be wired using no more than 4 or 5 meters of cable in total if the string was started and ended above the inverter , Instead he has gone from the inverter to the other side of the roof to start the string using apx 7meters od cable and then another 7 to bring it back for each string ?? why would you do it that way ? total of about 30 meters when it could have been done in under 5m .
So i think that i will buy the cabe myself and redo it . do you think this would help ?

and the other thing as i have found that bad conection there could be more causing high restance so might have to check all conections now to be sure?

 

[crazygraham]

Forgot the Photo

 

[ktech]

Couldn't see the photo you uploaded so might have got this wrong:
You said 'made the panels into one string as the higher voltage will have less power loss'. Do you mean the east and west panels are now on one string? As i couldn't see the photo the only other thing i can think is the east side was split into two strings and paralled up in the isolator?

 

[ktech]

Is that a DC isolator?

 

[Earthstore]

As has been mentioned, leave the DC cables alone, it is high voltage and very dangerous, and you will be working on it live at some stage.
Your system will be no use to you at all if you are dead...
As to your output it seems OK, you have to remember that you are quite far north which makes a huge difference, if you lived in Cornwall that would be a different matter.
The beauty of an east/west split over south facing is even though your system will not peak so high, you tend to produce a steady power output for a longer period, which, in my view makes it more usable.
I hope this helps.

 

[crazygraham]

Hi guys the west system is on 1 string of 12 panels and the east side is on 2 strings 6 so i made it into one string of 12 at the inverter just,
that is the DC isolator there is 4 of them in total cable was hanging out of it causing one of the strings to go down ,
I am an electronic engineer so i have a wide experinace working with power however have never worked on any thing to do with solar.

 

[Earthstore]

It does appear that your installers have done some strange things, will they not put it right?
You do seem to understand it now, so I am sure you could point them in the right direction.
And it is good to ask on this forum, there are some great people on here that offer advice for no personal gain.
But as I put before, take care with the DC.

 

[sedgy34]

thats a nice loose connection you have

 

[crazygraham]

Yeah SURE IS lol

 

[sedgy34]

The links are for spreading the load across the switch your installer doesn't know that by your pic