Does this mean my second string isn't working?

When my system was installed I understood I had two strings - one for the south facing part of my roof (5 panels) and 1 for the west facing part (3 panels). I've just been playing with the portal and found I could look at the current, voltage and power for each string. There is plenty of data for the south facing string, but the west facing one shows 0 for current, voltage and power and has done since day 1, even though in the afternoon , after about 2.30 pm,it should be churning out power. Does this mean that there is something wrong with the system? I was told commissioning was fine, so why does it look like my west facing roof is generating nothing? This probably explains why even though we have had incredible sunshine I have never generated more than 2.4 kw at any one time. What should I do - can Give Energy check this out remotely, or do I need to contact the installers?

There is a startup voltage required on each string for the inverter, that may not be met by the string with just 3 panels.

The Gen1 hybrid inverter (with white USB WiFi dongle) requires 120 Volts dc.
The Gen2 hybrid inverter (with built-in WiFi and a black antenna) requires 150 Volts dc.

Your installer may have provided a data sheet for your chosen model of solar panel, and it is the Voc value that you need , multiplied by 3 for the string with 3 panels. A solar panel Voc can be as high as 50 Volts dc in direct bright sunshine, but can drop away to 35 Volts dc or lower depending on the specific model and less bright conditions.

The installer needs to prove the string is working correctly.

Out of interest, what is the highest string voltage reported on the string that is working. The installer may have wired all 8 panels in one string, and not told you.
The cables from the solar panels are connected to the inverter on the bottom left hand side, so you could count the cables present. 2 cables means only 1 string connected, 4 cables means 2 strings connected.

Hi Simon,

I don't have a hybrid inverter. I have a Solis inverter (S6-GR1P3K) together with a GivEnergy 3.0AC and an 8 KW battery. My panels are Trina 400W. The Voc value is 41.2 STC and 38.8 NTOC. The solis inverter has a startup voltage of 60V. The highest output from String 1 today occurred at 14.29 and was 2286W (9.2A and 247.5V) If it is any help I have 4 cables going into the Solis inverter - so in theory I guess that means I should have two strings. The "My Inverter" data on the portal also suggests there are two strings, but the second one is reading zero for everything all the time.

Your 2 strings might well be combined on the DC side via the Solis inverter. Your GivEnergy system just sees the output from that (I had the same query with my similar setup). Neither individual string will be generating >2kW, so your peak numbers suggest both are operating.

I think you are right about the Solis combining the strings - it has 4 cables going in, but only one big cable connecting to the 3.0Ac box.
So although my panels 8 x 400w have the potential to generate 3.2 kw - due to the arrangement on two sides of the roof, it is unlikely that they will ever achieve this; because if the sun is shining on the south facing panels then the ones on the west side won't be at full capacity, and as the sun moves round and the west side powers up there will be a reduction on the south facing ones. But I should get a lower level of power for longer? OK! Panic over - these portals are dangerous things - the more information I see - the more confused i get!

Given the time of day of your peak output, and the current reading of 9.2 Amps, I would guess your panels were all operating around the maximum power point as indicated by the NOCT values from the Trina data sheet.
That is around 32 Volts per panel, giving around 252 Volts with 8 panels connected in series.
Although you have 4 cables from your panels, it seems like they are connected in such a way that all 8 panels are connected to 1 single string input on the inverter.
I would get in touch with your installer, and ask why they have configured it that way, and not as originally described to you. Normal wisdom with panels facing in 2 directions is to utilise each inverter string input for each direction in order to maximise the solar panel efficiencies and combined output.