Why I get a voltage drop from my solar panels on the early morning and late evening

[cham cham]

The voltage drop is causing the inverter to turn on and off like 50 times in the early morning and in the evening.

My grid tie Fronius IG 30 inverter is keep turning on and off like 50 times before it connects to the grid in the early morning because of the voltage drop. In the evening it turns on and off like 50 times before it shuts off completely because of the voltage drop.

I check the voltage at least 2 times.

In the early morning the voltage is reaching to the point of 150 volts that inverter is light up ready to start up but when the screen is barely lit up the voltage from the panel is suddenly dropped from 150 volt to under 90 volt and causes the inverter to turn off. After a few second it starts again. This is continues for like 50 times before the voltage is stabilize to stay at above 100 volt and when it gets brighter the voltage stays on above 150 then the inverter connects to the grid.

During the day light it has no problems it connects straight away. This is happing in the early morning and late evening time. The voltage dose drops during the daylight from 304 volt to 250 volt and it stays between 220 and 270 while in operation.

Could you let me know is this normal for the inverter to turn on and off constantly in the early morning and in the evening or is there something wrong with the panel or inverter, or if the inverter is design this way. The voltage is increased and decreased from the panel side I though it may the panel is faulty. But on the other hand during the day after the sun has risen there are no problems of this kind.

I move to this property about a month ago. So I don’t know much about the history of this system Apart from the inverter is the Fronius IG 30 and 8 panels of 245 watts connected to it.The DC cable length is about 25 meter from the panel to the inverter.
On a sunny day I get like 1600 watts from the panel. The panels are not on a true south facing, it’s slightly off to the south west side.

Thank you everyone

 

[whinmoor]

Re: Why I get a voltage drop from my solar panels on the early morning and late eveni

You've got 8 x 245w panels on a Fronius IG30? What brand of panels?

8 x 245 = 1.96kWp system.

We would have selected a smaller inverter.

How long has the system been there? It must be under-performing?

It sounds like your system has been poorly designed. Time for a discussion with the installer.

To answer the question, inverters don't normally stop and start during the day (except either during an eclipse or in particularly heavy clouds!). They wake up in the morning and switch off when it's going dark.

 

[whinmoor]

Re: Why I get a voltage drop from my solar panels on the early morning and late eveni

Oh, can you look at the writing on the DC cable running from the panels to inverter? For a 25m run, I'd much prefer 6mm cable to 4mm.

 

[cham cham]

Re: Why I get a voltage drop from my solar panels on the early morning and late eveni

Oh, can you look at the writing on the DC cable running from the panels to inverter? For a 25m run, I'd much prefer 6mm cable to 4mm.

Thank you for reply
The wire run from the panel to the inverter is 4mm
The brand of the panel is sharp
The inverter is not start and stop during the day. It only start and stopping first thing in the morning and late in the evening when it time to be shut off. I mean it should be turn on at once in the morning and turn off at once in the evening.
During the day light when I turn it off and on. It got no problem it start and connected straight to the grid. Just the first thing in the morning and late after the sunset is doing all starting and stopping. the system about 5 years old. i bought the house previous owner move abroad and i don't have a contact details. if i know any thing about it i will post it here
thank you

 

[cham cham]

Re: Why I get a voltage drop from my solar panels on the early morning and late eveni

The brand of the panel is sharp
The inverter is not start and stop during the day. It only start and stopping first thing in the morning and late in the evening when it time to be shut off. I mean it should be turn on at once in the morning and turn off at once in the evening.
During the day light when I turn it off and on. It got no problem it start and connected straight to the grid. Just the first thing in the morning and late after the sunset is doing all starting and stopping. the system about 5 years old. i bought the house previous owner move abroad and i don't have a contact details. if i know any thing about it i will post it here
thank you

 

[whinmoor]

Re: Why I get a voltage drop from my solar panels on the early morning and late eveni

1) Probable inverter mis-match.
2) Penny-pinching on the cable thickness.

I'd get the installer round for a chat...

 

[moggy1968]

Re: Why I get a voltage drop from my solar panels on the early morning and late eveni

4mm cable is fine (voltage drop around 0.71%).
the inverter is over rated for this installation.
Inverters have a higher start up requirement than switch off to stop this happening. I would say that because they have overspecced the inverter they have altered the settings to reduce the start up voltage. It is now too close to the switch off voltage so in marginal or changing conditions the inverter keeps switching on and off.

The problem will become worse as the panel output drops with age.

My Hilux does the same with it's auto headlights!!!

Your solicitor should have contact details for the former owners. The installer should, however, have left their contact details on site.

like!

 

[BruceB]

Re: Why I get a voltage drop from my solar panels on the early morning and late eveni

Assuming there is not a loose connection anywhere, then increasing the startup voltage on the inverter should sort the problem. It is trying to start too early at the moment before the panels are able to generate enough power to keep the inverter going.

 

[Energetic]

Re: Why I get a voltage drop from my solar panels on the early morning and late eveni

Was thinking start voltage also. If that doesn't resolve it fronius has good tech support, however i dont beilive they deal directly with the end user, you'll need the/an installer to do it. This inverter would have a 5 year warranty so might still be in warranty if there's other issues.

The DNO (grid operator in your area) would have a record of who installed it i believe, if you can't find it anywhere else.

 

[moggy1968]

Re: Why I get a voltage drop from my solar panels on the early morning and late eveni

BruceB
I don't think that will sort the problem. I don't know what the start up voltage is on this inverter but the specs I have certainly sugest you will struggle to achieve even operating voltage from this array. Thats why the inverter has been derated and why there is a problem.

It's the wrong inverter, period

 

[BruceB]

Re: Why I get a voltage drop from my solar panels on the early morning and late eveni

BruceB
I don't think that will sort the problem. I don't know what the start up voltage is on this inverter but the specs I have certainly sugest you will struggle to achieve even operating voltage from this array. Thats why the inverter has been derated and why there is a problem.

It's the wrong inverter, period

You might be right. I have not installed Fronius and based my answer on other (SMA & Power One) inverters. Having now had a look at the Fronius manual it appears that the startup voltage is 150V and is not alterable by the user or installer based on the settings available in the published manual. It is possible Fronius service partners who have done the course have access to more detailed settings. I'll leave that for others to pick up and bow out.

 

[moggy1968]

Re: Why I get a voltage drop from my solar panels on the early morning and late eveni

OK, thats good info Bruce. At 150V start up voltage it shouldn't have needed changing by the installer then. mY data sheet for the Fronius IG gives an operating voltage of 350-700V, which is much too much for this system.

Either way, it's the wrong inverter though. I would suggest a change to a smaller inverter will solve the problem but really the system needs checking out by a decent installer.

 

[cham cham]

Re: Why I get a voltage drop from my solar panels on the early morning and late eveni

OK, thats good info Bruce. At 150V start up voltage it shouldn't have needed changing by the installer then. mY data sheet for the Fronius IG gives an operating voltage of 350-700V, which is much too much for this system.

Either way, it's the wrong inverter though. I would suggest a change to a smaller inverter will solve the problem but really the system needs checking out by a decent installer.

I look at the manual on this inverter. The start-up voltage is 150v to 400v I check on the inverter total. It shows on the screen. The total maximum voltage comes from the array is 304 volts. The minimum recoded 271 volts. So it well above the start-up voltage of 150v
In the morning the voltage come to the point if 150v. The inverter is waked up. At the point of connection at 150v the voltage drop back to below 100v turn the inverter off. then in few second the voltage increase back again to the point of 150v it start the inverter again at that point the voltage drop again below 100v cause the inverter to turn off.
When it’s become brighter than the inverter is not dropping the voltage below 100v and stay connected until connect to the grid. At the last few minutes before connect to the grid. a message appear on the screen. Low DC power or DC power low. After a few second of that message then it connects to the grid.
The only problem I got is at early morning. And late afternoon. The voltage drop from 150 to below 100.
I think the inverter is wake up half an hour early it supposed to in the morning. And stay connected on for half an hour longer than supposed to. I don’t know if something wrong with panel for dropping the voltage or if something wrong with inverter.
When I turn on the inverter manually in the morning half an hour later then it supposed to wake up. It connects straight to the grid none of this problem of on and off.
I don’t want to change something that end up something else is wrong. I mean if the system is under power If add a few more panel to the system do you think it will fix this problem.

 

[whinmoor]

Re: Why I get a voltage drop from my solar panels on the early morning and late eveni

Do you have space on your roof for more panels? I wonder why the previous owner didn't max out?

I think you need to identify the original installer (if they are still trading) and politely request a site visit to discuss the issues. They should have registered the installation with Building Control at your local council. You should also have an official MCS certificate which gives their name. Surely you got some paperwork about the PV system when you bought the property? If not, it might be worth discussing with your solicitor/conveyancer.

If you tell us where in the UK you are located, someone from this forum might be able to offer assistance.

 

[Earthstore]

Re: Why I get a voltage drop from my solar panels on the early morning and late eveni

Your FIT provider should have a copy of your MCS certificate, the installer should be on there, of course it depends on how helpful your FIT provider is....