FoxESS Community - Owners & Installers Forum

Hi there
I'm a new starter and would really welcome some advice!
We had 10 panels, a Fox H1-3.7-E-G2 invertor and a Fox 10kWh EP11 battery installed last Monday.
Our property is currently being refurbished. It is empty at the weekend, with no appliances switched on apart from internet/WiFi equipment drawing less than 40W.
Yesterday (Saturday), the total yield from the panels was about 7kWh. But we drew 19kWh from the grid, with the battery discharging, then charging, then discharging, then recharging again between 08:00 and 18:00. Hopefully the screenshots helps.
Surely the basic point is not to pay for power from the grid when you're generating more than enough yourself from the panels.
Any thoughts as to what I should do please? The installers told me nothing.
Many thanks.

Hello, looking at your traces and from what you have described the inverters CT clamp has been fitted incorrectly and is facing the wrong direction.

The CT clamp tells the inverter how much power is being drawn from the grid or exported to the grid and if fitted incorrectly the moment the sun comes up your batteries will discharge into the grid as you are seeing.

2 options, either contact your installer and ask them to come back and fit it correctly - or you can find the CT clamp, un-clip it and rotate it 180 degrees so that the arrow is facing in the opposite direction.

If you want to do it your self, in your meter cupboard you will find the CT clamp fitted on the live feed from the meter (it's usually a small white clip on), it has an arrow on one face so you know which direction it is facing, un-clip it, turn it round so it is facing the other way and close the clamp again.

That's really helpful, Dave - thank you.
In the circumstances, I think I'll ask the installers to come back and do it.

There seems to be another issue with our new installation.
The 10 solar panels are in two arrays of 5 panels - one facing SE and the other facing SW.
From the graphs, it looks to me as though one of the arrays is not working properly, typically generating less than 10% of the other one.
Is anyone able to offer any insight as to why this might be? Have I interpreted the graphs correctly?
Thank you.

They've been connected as 10 panels in series i.e. a typical 400 watt panel would be running at around 32Vmp and so 10 panels in series = 320V which is what you are seeing, PV2 would appear to be floating and is picking up induced voltage - it's likely not connected to anything.

As it is a H1-3.7 the recommended input power per MPPT is 3,400 watts and your 10 panels at full power would likely exceed that although it should still work ok as it is still within the single MPPT upper limit, the bigger issue is whether the panels are all facing the same way at the same elevation, if they are on different roofs they should be split, if they are all facing the same direction they should be ok.

As you have said one roof is facing SE and one SW I would suggest this is definitely a sub-optimal installation.

Thanks Dave - I really appreciate your insight.
Here's a photo of the panels, looking north.
I'm sure the installers said the two arrays were connected independently, but I could have got that wrong. They did talk about microinverters. Would they make a difference? Is there anything that could be done at this stage?

Rather than looking at PV voltage, go to the website and look at PV1Power - that will show you the power generated by the string across the day, can you post some traces of that as it will show any throttling effects if they are serious.

Micro-inverters would convert each panel at source into it's own inverter which would be the most efficient - but they clearly decided against that (price?) as this is DC connected and the Fox inverter is doing the conversion work.

They could also fit optimisers onto the panels, their job is to remove panels from the circuit if they are shaded or running at much lower power than the others, you would need them fitting on each panel which would add cost - *but* in your example the best way to achieve maximum power by a country mile would be to cable them as you suggested as 2 * 5 panel strings.

As we are in the winter months when the suns elevation is low, the SE panel will wake up first but will be held back because the SW panels are not receiving any direct light, at midday both sets of panels will receive light and will be at full power, then gradually as the SE panels loose direct sunlight they will start to throttle the SW array.

In the summer months the problem will be less noticeable as the suns much higher elevation will reduce the time at the start and end of the day where the panels on one roof panels restricts the other.

The PV cabling will be in the loft (i.e. this is not a scaffolding problem) and so it just needs the 2 panels to be terminated independently as 2 strings in the loft and then run to the inverter as 2 separate strings and you will have the ideal install.

Thanks again Dave.
Here are the traces for PW1 Power this week.
My invoice says I paid for ten "TIgo TS4 PV Module Advanced Add-On/Retrofit", which I assume are optimisers. If it helps, there are certainly two cables coming from the panels to the inverter, as shown in the photo.
As far as the CT clamp is concerned, I have a rather poor photo showing the installation around our electricity meter. There appear to be two clamps attached to one cable? One of them has an arrow visible.
Does any of that help?

ok the Tigo TS4 is an optimiser so they have fitted one to each panel, their job is to remove the panel from the circuit if they are shaded and they will help to manage the balance between the 2 arrays.

Your PV1 power traces don't look too bad (for this time of year) so best to monitor the performance on clear sunny days - although it's not likely we'll have many of those for a while - probably March before they start to get a work out.

The 2 cables you can see going into the DC isolator are the single arrays +ve and -ve and you can see on the bottom of the inverter it is plugged into PV1 (the PV2 connectors are unused).

The CT with the arrow on looks like a Myenergi CT (and the arrow is pointing in the correct direction) - do you have an EV charger or an EDDI for your hot water ?, it isn't the best photo to see but the other CT is likely the inverter clamp.

So that all sounds reasonably positive.
Yes, we had an EV charger installed at the same time. Should the CT for the inverter clamp be pointing in the same direction as the Myenergi clamp?
Thanks again.

LegacyJohn wrote: Sun Jan 26, 2025 5:10 pm Should the CT for the inverter clamp be pointing in the same direction as the Myenergi clamp?

Yes it should (as long as they got the polarity correct when they wired the connector) - what I can say for sure is that it should be pointed in the opposite direction to the one it is at the moment.

Thank you. I'll have a look when I'm back at the property tomorrow.
I really appreciate your time and help.

This is how the clamps are currently fitted.

Ok, if the system is still dumping the battery to grid when the solar starts generating, then although the CT clamp is fitted with the arrow pointing in the right direction it must have had it’s wires crossed in the inverters CT connector which case you will need to unclip it and turn it round.

(Leave the Myenergi clamp as it is)

Thanks again. I've notified the installers - I'd rather not tamper with electrical things I don't understand!
I don't know if the attached screenshot helps, but I was surprised to see a negative 'load' when we had a fan heater and lots of work tools running in the property the other day. Should there ever be a negative load?

Yes I don't blame you, best leave it to them.

You should never see a negative load, the load is calculated by ... you guessed it... 'the CT clamp' , and so if it is fitted the wrong way round you will get a negative house load.

Yes, I wondered if that might be the case. So this is more evidence of the issue being with the CT clamp.
Many thanks.