FoxESS Community - Owners & Installers Forum

Hi,

We've experienced our PV fuse tripping a few times recently which is slightly annoying as it wasn't something we initially spotted. From reading around it seems like one possible issue might be the rating of the fuse (I'm no electrician so my knowledge is limited!). I am also contacting our installer but it would be good to get some impartial input.

It happened 3-5 times previous, then I made a log of when it happened:
12/4/26 PV fuse tripped during day. Showery weather.
28/4/26 PV fuse tripped during night. Cloudy, damp weather.
2/5/26 PV fuse tripped around 5pm. Sudden showery. High battery charge, possibly 100%.

We are also getting fault codes 1, 26 and 27 on the inverter (see image). Resetting the fuse seems to sort the system out after a minute or so and it is back to working normally. However, this seems to happening more frequently now so it would be good to try and understand why that might be.

Our install was June 2025. We have 14 panels on the roof and a 10kW battery (2 x 5kw).

Thanks for any input,
Tom

What inverter size do you have ?

First observations are that your PV fuse is an RCD with 30mA, Fox recommend a 100mA RCD, although 30mA often works ok but it can lead to nuisance tripping similar to what you are seeing.

The errors 1,26,25 occur together and are symptomatic of grid (utility lost) which will be because the RCD is tripping.

I'm pretty sure it's 6kW. The image is from the side of the inverter.

Ok the breaker is well within it’s capabilities for a 6kw inverter, so it’ll be tripping on the RCD limit - it’s possible the RCD is going a bit soft which would see it trip early, but it would be wise to have the installation checked in case there is any arcing to any of the connectors and go from there.

What do you mean by tripping on the RCD limit? If it's easy to explain I would appreciate it as I'm not clear exactly what you mean. Thanks

tombuck wrote: ↑Wed May 06, 2026 9:11 pm What do you mean by tripping on the RCD limit? If it's easy to explain I would appreciate it as I'm not clear exactly what you mean. Thanks

It’s an RCBO which does 2 things, it protects for over current - 40A in this case, your inverters maximum power is only around 27A and so it could not trip the circuit breaker side.

The second function it has is the RCD, this is looking for an imbalance of 30mA (a standard domestic trip limit). This is a very small current but if it trips it is indicating possible leakage to earth - the problem here is that heavy appliances and large inverters such as this will on occasion trip a normal domestic RCD, particularly when the charger is on, and this is why Fox recommend a RCD that is 100mA for their equipment.

The problem with domestic RCD’s is that some are not particularly high quality and they may trip at half their rated limit and often get worse as they age (often referred to as going soft).

The first thing to rule out is that there are no electrical connection problems by getting an electrician to check the AC connection to the inverter, if the connections are ok then you could try changing the RCBO for the same rating to rule out it going soft, but it would be better to replace it with an RCD that is correctly rated (to 100mA).