43 minutes ago, TaliaB said:

@DinoV Another way to test the panels is disconnect all the panels from each other. If your multimeter can measure amps normally max 10 amps dc. You need to change the pos probe to the current input. If your meter has 3 probe inputs it can measure amps. Then on amps put the leads across the pos and neg wire there is going to be a small arc so do it quickly and positively then check the amps on your reading and compare it with your panel spec ISC they sould be very close. Do this in full sunshine at around 11 am. I do this test as default before installing the panels i use 2 multimeters one for current(ISC) and then check the VMP to ensure the panels are close to STD values.

Good test is the short circuit for a few seconds if during peak PV. 

Just a heads up. One member tried it the other day and his meter blew. Not sure why. Can only speculate that the wrong scale was selected or the meter had 4 banana sockets and the positive was in the 200mA socket and not 10/20A?

There is only one tester and that is a FLUKE. On the mine we only use FLUKE because of there superior protection when doing something stupid like testing 11Kv with it🙄🤐. Don't ask how we know this😅

2 minutes ago, Jacques Ester said:

There is only one tester and that is a FLUKE. On the mine we only use FLUKE because of there superior protection when doing something stupid like testing 11Kv with it🙄🤐. Don't ask how we know this😅

🤣🤣 Yes i second that

On 2023/07/19 at 12:40 PM, DinoV said:

So I measured each panel this morning at 10:30am. Each one seems fine with the results ranging between 42V and 44V (It's partly cloudy today, mostly cloudy).

Back at the breaker (8m cable length to the neutral end of the PV series and 4m to the Live end of the series) the voltage measured 80V. The only thing between the DC circuit breaker and the panels is cabling.

If I understand this correctly, I should be getting ±160V across the panels but am only receiving 80V after the cable run to the breaker. That's a 50% drop in voltage over the distance. I'm not an electrician but this does seem extreme with my limited understanding.

The other thing that confuses me a little is that it is cloudy today and I appear to have a higher voltage reading compared to the 65V I had yesterday which was perfectly cloudless.

My eyesight is deteriorating rapidly but that's a topic for discussion with an ophthalmologist.

Back to the subject matter, are you sure you are reading V (volts) and not mV (millivolts) on an autoranging DMM?

You could be having a loose connection / poor termination somewhere and the meter is showing 65-80 mV at the breaker instead of a steady 0V. 

 

Edited July 20, 20232 yr by Kilowatt Power

Since you were measuring no load, that pretty much rules out the high resistance idea, at least until you get the voltage right. 

Now I'm thinking that you must have one panel reversed somehow. Since the connectors are presumably polarised, this would have to be a manufacturing error.

Did you pay close attention to polarity when testing individual panels? 

46 minutes ago, Coulomb said:

Since you were measuring no load, that pretty much rules out the high resistance idea, at least until you get the voltage right. 

Now I'm thinking that you must have one panel reversed somehow. Since the connectors are presumably polarised, this would have to be a manufacturing error.

Did you pay close attention to polarity when testing individual panels? 

I can't definitively say that I noted polarity of each panel. I was very methodical when installing by using the manufacturers labels, so that each panel "faces up" so to speak. So the labels of each panels are on the top high end. When I looked at polarity when finally connecting them together, the poles per panel are labelled as "+" and "-". The male and female connectors are identical across all panels and the "+" with a male connector joined perfectly to the "-" female of the next panel the whole way across. There were no hiccups in that regard.

Then when I tested voltage per panel, earlier this week, the leads of my multi-meter were used identically across panels - red lead to my right connecting with "+" and the black lead to my left connecting to the "-". I did this identically across all panels and all readings were in a positive range. I did not experience any negative readings during that process which may indicate reversed poles (I think). If there are reversed poles I haven't experienced anything directly related to each panel that has given me an indication that there might be a problem.

Out of interest, I opened the "+" terminal on one panel (it's a little black pop out and clip in cover) over the terminal and can report that on that one panel the manufacturer has completely sealed any access to wiring, terminals etc on the inside of the panel. It's sealed in white resin or epoxy or silicon of some sorts.

@Kilowatt Power yup the multimeter is pretty clear. Measuring Volts definitely.

On 2023/07/19 at 1:39 PM, DinoV said:

I was also wondering about that. The problem is that the "+" of the first panel is 4m away from the "-" of the last panel. My little multi-meter can't stretch that far.

Let's depict the 4 panels in series as +A-+B-+C-+D-, installed left to right from the inverter
String positive is on panel A (4m long cable) and string negative on panel D (8m long cable).

Reading 1: +A-+B-+C-+D- = 80Vdc

Now, by moving the longer negative lead inwards one panel at a time, record the following voltage readings:

Reading 2: +A-+B-+C- = 
Reading 3: +A-+B- =
Reading 4: +A- = 

NB: Voltage should be measured at the incoming terminals of the breaker in the off position i.e without load.

measured all 4 panels in series = 167V at 10am (partly cloudy today)

at the combiner box I disconnected the surge arrestor and had 147V at the breaker. The inverter had a reading of 117V I have left eh surge arrestor disconnected and had a mostly consistent 110V at the invertor even in complete shade.

16 minutes ago, DinoV said:

measured all 4 panels in series = 167V at 10am (partly cloudy today)

at the combiner box I disconnected the surge arrestor and had 147V at the breaker. The inverter had a reading of 117V I have left eh surge arrestor disconnected and had a mostly consistent 110V at the invertor even in complete shade.

Was the SPD the main cause for reduced string voltage?

All in all, I'm glad that you're now getting reasonable voltage and that you can now proceed with optimizing your PV setup by adding 2 or more panels. 

11 hours ago, DinoV said:

at the combiner box I disconnected the surge arrestor and had 147V at the breaker

Was the surge arrester getting hot, or was the sunlight suddenly different?

Greetings all. Just a quick reply to relate that I have been busy with other prioritites over the last 2 weeks and haven't done anything further about this situation. I have purchased 6mm solar dc cable (hopefully copper) and will look at changing my 4mm cable for the 6mm cable. The surge arrestor is still disconnected. I don't know how to test it. It's just one of those that has a green indicator that turns red once the arrestor has "burnt out". At present the indicator is still green.

Insulation resistance(IR) testing can be performed between + and - to ground at 250 V DC. However, regardless of the test voltage applied, the measured insulation resistance should be at least 1 MΩ. If the SPD window is still green it should still be functional but do the IR test anyway.

14 hours ago, TaliaB said:

Insulation resistance(IR) testing can be performed between + and - to ground at 250 V DC.

I would make sure that the inverter is disconnected from the panels for that test. It's also likely to fail if the inverter is still connected, as well as possibly damaging the inverter.

19 hours ago, DinoV said:

the surge arrestor is still disconnected

Yes i agree @Coulombthe spd should be taken completely out before doing the test so @DinoV remove it completely should you decide to do the IR test or either just replace it with a new one.

Hi all. Finally had some more time to tinker with my system and solve the problem. I installed a new 6mm solar DC cable and pulled out the old 4mm cable and connectors. When I opened the old male and female connectors I noted that the cable pulled out of the connectors VERY easily. On opening I noted that the cable had not been well crimped all those years ago. New cable + new connectors + good crimping means that I now have almost perfect voltage at my invertor (166V) with full sun. Today it is mostly cloudy and I am getting 135V at the invertor.

Thank you everyone for your kind input. I think we can close this topic as "solved".