Solar Panel Output cutting out

[Earthstore]

Could this be the same problem that sanyo/SMA had?
If the system is split on two strings, is it possible that just as the sun is coming around the inverter is searching the wrong power curve, maybe switching the optitrac on would cure it?
Just a thought.

 

[GaryM]

Cable is 4mm so I have been advised is suitable for the job.

Don't SMA recommend 6mm2 for the AC cable and not 4mm2 as the OP states he has?

 

[SolarCity]

I don't think this is a Sanyo/SMA compatibility issue as there are grid fault error messages. I would also doubt that the cable size is the issue.

 

[Earthstore]

Another suggestion then, put 2x24hr voltage monitors one on the incoming and one at the inverter, this will then show you what it is really happening and give you some accurate data to work with.
I am aware that the DNO have such a system, not sure where you can obtain them from though.
In my opinion it is normally an installation/design problem rather than the grid, but never say never.
Just another thought.

 

[Glen Powell]

I have found if more than one install is on the same line the the wire size does matter, I do not know the reason why this is, however we had an install of 2 x 3kw systems ground mount 15meters away from house, both properties were tripping, one was on other was off scenario. we changed the wire from 4mm to 10mm after DNO said no problems on grid.

After changing the wire both systems have worked perfectly well, the 10mm was a bit overkill but I do beleive there is a fundimental problem with feedback to inverters in close proximity, however that would not really explain how changing the wire size would help.

 

[Motters]

Hi
Thanks everyone for your replies. There would seem to be no obvious solution and I`m out of my depth.
I just cant understand why the system seems to work fine until midday and then the input voltage jumps to over 500V DC, knocks the system off and then its on and off for the rest of the day.
Thanks again everyone
Cheers
Motters

 

[Gavin A]

the voltage of the 2 strings is independent, you don't add them up when looking at the voltage limits.

I reckon you've got 2 issues going on here...

1 - System is running higher than it's rated capacity, so self limits by adjusting the voltage to a less efficient point on the voltage curve, which is why you're getting such odd voltage readings.

2 - At the same time, you're also trying to push too much power down too small a pipe, resulting in the AC voltage from the inverter going up significantly, probably past the 253 10 minute average limit. I'm almost certain it should be 6mm cable on the 4000TL for a 10m length precisely to stop this happening.

Suggest to your installer that they try swapping out the cable before swapping the inverter.

 

[sedgy34]

I agree i think at its peak at that particular time its knocking it out
u should change ac cable it will be cheaper also you should phone Sma first as the inverter might need tweaking on it's setting there are adjustments behind the cover
Not suggesting you do it, a sparky should whilst on phone to Sma tech

 

[GaryM]

As I mentioned above, SMA do not recommend anything less than 6mm2 conductors for the AC side of a 4000TL for a maximum length of 23.3 meters.

Have a look at the SMA manual here - PDF Download Section 5 - 5.3 - 5.31

Also stated there is:

Cable sizing

The grid impedance of the AC cable must not exceed 1 ohm. Otherwise, the inverter will disconnect at full feed capacity due to excessive voltage at the feed-in point.
The conductor cross-section should be dimensioned such that cable losses do not exceed 1 % at nominal power.

Installing a 4mm2 cable would actually be non compliant with BS7671 (Electrical Regulations) which states:

134.1.1 Good workmanship by competent persons or persons under their supervision and proper materials shall be used in the erection of the electrical installation. Electrical equipment shall be installed in accordance with the instructions provided by the manufacturer of the equipment.

OK, it's not dangerous but the installer has failed to know the installation requirements of the product he's supplied and installed. I'd contact him and point this out.

 

[provr6]

Hi

I had a solar panel system fitted 22 Feb 2012. The system includes a 15 panel sharp 245 array split into 2 strings of 9 and 6 running into a Sunny Boy 4000TL.

They system seems to produce consistently until about midday then cut out for periods if there is a decent amount of sunlight. I have been monitoring the system with Sunny Boy Explorer and noticed if the combined string voltages exceed 500v then the output drops to 0A and 0W. This remains the case until the voltage drops below 500v.
When running normally the volatges for each string are 280-290V and 170-180V. This can then jump to over 300V and 200V and knock the system out. I believe the inverter operates up to 550V. Would changing the inverter to the 4000TL with Reactive Power Control which has a 750V limit cure the problem or is there a more fundamental issue here.
I have also noticed recently that output power has sometimes been exceeding 4.2KWh which seems strange for a system with a stated output of 3.675KWh.
The installers have been around a couple of times and seem a little mystified but have suggested replacing the inverter as a first solution.
If anyone can offer me some advice I would be most grateful.
Cheers
Motters

As others have said the combined Voltage exceeding 500v is not a problem as each of the 2 trackers in your inverter are rated upto 550v each (1100 total). I have looked at the technical data and it states the max input power as 4200w and you state you are exceeding this at certain times. Could this be part of the problem? You would likely generate most power around noon if the panels are on different roofs and different orientations (thats the situation with mine).

 

[Motters]

Hi
Thanks again for all your replies. I have been monitoring the system this morning.Nice bright sunshine, copied these readings
Current [001] 8.014 A
Current (002) 8.556 A
Voltage [001] 263.52 V
Voltage (002) 175.07 V
Power [001] 2112 W
Power(002) 1497 W

Looks nice and healthy, I will be keeping an eye on it to see when the readings jump.
Cheers
Motters

 

[ktech]

Don't think this has been mentioned but have you checked the inverter is set for G83 ? Turn off AC isolator, wait a minute, turn back on and check the lcd display shows G83/1 during the power up procedure.

 

[Motters]

Hi

1143 -No really strong sunshine but this occurredC side readings

Current [001]

0.000 A

Current [002]

0.000 A

Voltage [001]

307.55 V

Voltage [002]

205.41 V

Power [001]

0 W

Power [002]

0 W

1146 - Came back on again
Cheers
Motters

 

[danesol]

Don't think this has been mentioned but have you checked the inverter is set for G83 ? Turn off AC isolator, wait a minute, turn back on and check the lcd display shows G83/1 during the power up procedure.

It has been mentioned and possibly a good time for the OP to try this as I'm sure even though the installer has been out twice, no confirmation has been stated yet.....

Do your DC tails go into the inverter separately...... if so I would be removing one set at a time to see what effect that has, but if you are NOT confident to do this, leave it to your installer as high DC voltages could hurt !

 

[sedgy34]

Don't think this has been mentioned but have you checked the inverter is set for G83 ? Turn off AC isolator, wait a minute, turn back on and check the lcd display shows G83/1 during the power up procedure.

it wouldnt work with g59 setting