0.5A difference between 2 identical inputs. Solarriver 4000TL-D

[pdixon]

I've been waiting for some suitable weather to do some tests.
I need some full on sun in mid-afternoon to get the output up to 4kW again but we haven't had that sort of weather since I first started this thread in September.
I'll then compare what the inverter says to what the generation meter says.

I suspect that the inverter is mis-reporting what's going on.
If that's the case then I'm not too bothered by it.

Let's hope for some good weather soon. Today was my best production day since I got the panels in with 24kWh but it only peaked at 3.6kW.

 

[Donk]

24kWh a day is pretty good, the sort of number you'd want to see on a standard 4kWp system. Was 3.6kW before inverter or after? (DC or AC side)

 

[Unregistered]

OK, the man at Samil is still pondering my request for a new inverter and is sending the data I have provided to China for evaluation.
Meanwhile, a pallet arrived today with a new inverter on it! My PV installer has either bitten the bullet and sent one or they have advised Samil of the error of their ways. Either way, it's being fitted tomorrow AM. We'll see if it's any better.

Incidentally, Samil's data sheet for the SolarRiver claims an MPPT efficiency of 99.90%. With a 0.5A or in my case 25% shortfall on one MPPT, this cannot be the case and would therefore come under the "Not as described" section of the Sale of Goods Act 1979 (as amended)?

 

[SibertSolar]

99.9% MPPT efficiency doesn't relate to the displayed differences between each MPP tracker's values on the LCD. It's related to the ability of the maximum power point tracker's algorithm to actually achieve the "maximum power point"....it's a bit of a useless metric tbh

 

[Unregistered]

Thanks for this. Maybe my understanding of MPPT is flawed.
With 2 strings of 6 panels, both with the same orientation (-5 degrees off South) and no shadow, should they not be producing the same power IF the MPPT's are working correctly at 99.9% efficiency?
The strings have been swapped to prove the panels are not at fault
Could it be just a display fault?

 

[pdixon]

I've done some tests with mine and I'm sure it's just the inverter displaying the wrong values.
It's been cloudless today so when the output was leveling out at its peak in mid afternoon I took 3 measurements.
1 Just string 1.
2 Just string 2.
3 both strings.

When I measured output at the generation meter (which I assume is properly calibrated) then String 1 gave 1756W (inverter read 1885W!), string 2 gave 1726W (inverter read 1728W) and together they gave 3420W.
So it looks like the inverter is reading high for string 1 but really both strings are giving out about the same power.

 

[Bladevane]

I have an indentical issue. A Samil Solar River 4000TL-D connected to 2x8 panel strings. PV1 always shows higher power output in all conditions by around 5%. installer diagnosed panels are OK by swapping inputs to inverter. New inverter arrived today so will see if there is a difference.

 

[gordontwist]

Was there a solution to this problem?
I'm on my 2nd Solar River 4000TL-D, both are reading consistantly low on PV2.
2 identical 2kw strings, due south facing - PV2 reads low even if strings are swapped round.
Low light (early morning and late evening) see PV2 reading around 45-50% lower than PV1, peak light sees around 10% lower.
Anyone got an answer?

 

[Pascaleto]

Because this inverter is with 1 solar tracker their always will be difference between two strings. This is not really the ideal type of inverter.
The stronger string always will inject energy to weaker string.
You can use a string diodes to block this energy flow. I such cases better all panels to be in one string. (if it is OK with voltage at open circuit) .
High voltage - less current - less power loss, the other thing to be designed in that way.

 

[Pascaleto]

Use inverters with two independent trackers in such cases.
It is always better.

 

[Gavin A]

that is a dual tracking inverter

 

[gordontwist]

Use inverters with two independent trackers in such cases.
It is always better.

My understanding is that the 4000TL-D is supposed to be a dual tracking inverter.

 

[bp1000]

Glad i found this thread, i noticed the exact same issue too.

4kW pv installed yesterday and i noticed string 2 performing around 0.5a less. The actual generation exceeded similar installs in the local area so i don't think there is any particularly wrong.

Have you concluded this is just an optimistic reading on string 1 or do we think the 2nd string is not a strong? Because it is cheap chinese kit?

 

[Bladevane]

A replacement Samil Solar River 4000TL-D was provided by Samil with firmware version 1.90 and the installer fitted it. The apparent difference between PV1 and PV2 output was still evident even when string swapped round so original inverter was refitted. Samil say they have a similar problem in Taunton and would get back to me. Have they?? No.

 

[gordontwist]

I'm on my 3rd inverter now and finally have one that is as close to working as I think I'm likely to get.

PV2 trails PV1 very slightly, but no where near as pronounced as the first two inverters.

This one is firmware V1.80 - the last one was V1.74, and the first one was V1.70.

Interestingly enough, the only firmware available of Samil's website is V1.70

I think it is string PV2 reading low, as opposed to PV1 reading high - simply because of startup and shutdown times. On my install, PV1 would "start" a good 45 minutes before PV2 and still be generating a good half an hour after PV2 had switched off..

This is my first day with inverter #3 so I'll post an update after a sunny day...