Correct DC volts but almost no Amps

[lucchase]

New DEYE 12K hybrid split-phase system, with Zero Export to CT. No battery yet. Green Normal light is on as are AC and DC green lights.
I had to extend the CT wires. I did that by adding (without cutting) about 4 m of twisted-pair network cable.

Problem: Plenty of DC Volts but almost no Amps.
Three strings of 8 x 585W PV modules, but maximum watts I've seen from each string is 52 Watts. Mostly just one string has any amps and generally about 25 Watts.
The Voc expected from each string should be about 46.6V * 8 = 372.8 and I'm getting about 330V

I guess in theory, I should check for poor MC4 connections, but all three strings are weak. Number 2 string consistently produces the most at about 25W only.
The other two string are mostly 0W but sometimes 1 or 2 watts. The most I've seen was 52 Watts from each string, at the same time. That lasted maybe a couple minutes.
I've checked all the connections except those on the roof.

What should I be doing to troubleshoot this?

 

[jorby]

Unless you try to run something with the inverter, it can't actually pull any power from the panels. There is no battery to charge. The 52w is just running the inverter.

 

[Gray17]

Ok first thing i'd check is if one of the panels is faulty on each string and pulling the current down, also as you say may well be a dicky connection on the MP4s. Did you check each panel before fitment to ensure producing ok. Remember V =I over R therefore you may get volts but no amps as once amps are produced the load increases therefore high resistance joints stop that happening.
Another thing at this time of the year the suns is quite low ( in UK at least) how are your panels fitted are they flat or tilted, is there any shadows, which way do they face?
All these can make a difference.
As an example i get full voltage on my strings from about 7am but only 0.1a current on each string, however by 10am they are producing about 4 to 5a per string, by 11am about 6a, that it until 3pm ish when it drops again, however in summer get full 8a from 7am but the sun is a lot higher.

 

[Quattrohead]

With no battery to charge and no AC load, you are probably seeing what the inverter needs to run itself.

 

[Q-Dog]

What should I be doing to troubleshoot this?

Turn on a big load and see if the numbers change.

 

[lucchase]

Unless you try to run something with the inverter, it can't actually pull any power from the panels. There is no battery to charge. The 52w is just running the inverter.

The whole house (on grid port) and the EV (on load port) are connected to the inverter; and working.

 

[lucchase]

Ok first thing i'd check is if one of the panels is faulty on each string and pulling the current down, also as you say may well be a dicky connection on the MP4s. Did you check each panel before fitment to ensure producing ok. Remember V =I over R therefore you may get volts but no amps as once amps are produced the load increases therefore high resistance joints stop that happening.
Another thing at this time of the year the suns is quite low ( in UK at least) how are your panels fitted are they flat or tilted, is there any shadows, which way do they face?
All these can make a difference.
As an example i get full voltage on my strings from about 7am but only 0.1a current on each string, however by 10am they are producing about 4 to 5a per string, by 11am about 6a, that it until 3pm ish when it drops again, however in summer get full 8a from 7am but the sun is a lot higher.

Unfortunately, I did not check each module before connection.
The location is Barbados, and even though the morning was overcast, by late morning, we had clear skies. MC4s still prime suspect, but surprising to see this on all three strings. How can I test each PV connector??

 

[lucchase]

With no battery to charge and no AC load, you are probably seeing what the inverter needs to run itself.

The house and back-up loads are connected; but I can't verify that the inverter isn't just passing the grid supply through. If I switch off the grid, the inverter goes into an alarm state. It says F47 'AC_OverFreq_Fault' .

But I'll try starting with only DC power and see what happens. It would still have the 'Back-up Load' connected.

 

[lucchase]

Turn on a big load and see if the numbers change.

Tried this and nothing happened. My impression is that it is just taking power from grid and passing it through.

 

[lucchase]

I have a multimeter with a clamp, but unfortunately it is an AC-only clamp. I guess I'll need a DC clamp meter to get much further with this.

 

[lucchase]

By the way, the LOAD settings page on the inverter has a quarter-circle option in the bottom left called 'Forced'.
If I tap it about ten times, it turns red, and the inverter clicks. Ten more taps, and it turns off. But I can't find any documentation about it. Does anyone know what it is?

 

[lucchase]

The whole house (on grid port) and the EV (on load port) are connected to the inverter; and working.

Can CT-1 and CT-2 cause the inverter to behave as though there is no load and the PV modules to behave as though there is an open circuit?

 

[Gray17]

Ok well i would have thought being in Barbados, Sun shouldnt be an issue.
CT clamps the wrong way can cause inverter issues so ensure they are facing correct way around and on the Live wire not Neutral.
I'm assuming with no documentation its not a new inverter, is it possible its faulty. Also check under the PV inputs sometimes theres an on/off switch makes sure its in the on position.
You should also have a power meter connected to the mains in, this will tell you if your drawing or producing energy. Also check your inverters not in Demo mode, it should be in self use mode. You would be advised to go onto manufacturer website online and download a user guide, have a good read to ensure correct settings used in setup.
Also most have an LCD display telling you what inverter is doing and even an app on your smartphone for monitoring

 

[crossy]

Eliminate your CTs by setting to "Zero Export to Load" - This uses internal CTs which (hopefully) are connected correctly. If it then works verify your CT wiring and direction.

Make sure the grid mode is set correctly for your local supply.

Check you have it set the "No Battery" mode.

And definitely download the manual if you don't have one.

 

[lucchase]

Ok well i would have thought being in Barbados, Sun shouldnt be an issue.
CT clamps the wrong way can cause inverter issues so ensure they are facing correct way around and on the Live wire not Neutral.
I'm assuming with no documentation its not a new inverter, is it possible its faulty. Also check under the PV inputs sometimes theres an on/off switch makes sure its in the on position.
You should also have a power meter connected to the mains in, this will tell you if your drawing or producing energy. Also check your inverters not in Demo mode, it should be in self use mode. You would be advised to go onto manufacturer website online and download a user guide, have a good read to ensure correct settings used in setup.
Also most have an LCD display telling you what inverter is doing and even an app on your smartphone for monitoring

New inverter. This particular feature just seems to be undocumented.
Although I don't want to export to the grid, today, it somehow got the option to sell surplus turned on. Then everything started working as expected. So, at least I now know the array is working fine. The prime suspect now is a CT fault. Will check my extension wiring and probably try to shorten it as much as possible.

 

[lucchase]

Eliminate your CTs by setting to "Zero Export to Load" - This uses internal CTs which (hopefully) are connected correctly. If it then works verify your CT wiring and direction.

Make sure the grid mode is set correctly for your local supply.

Check you have it set the "No Battery" mode.

And definitely download the manual if you don't have one.

Will do the above. I have the manual and know it nearly by heart now. But there are a few undocumented features, so maybe there's a manual online that is newer than the one that came in the box.