Good day All,

I have a neighbor with an issue on his RCT Axking 5kw inverter. He had it for about 5 years now running only as a backup. He recently got 8x560W Panels installed. The system is running great, but every now and again the panels will produce 0W (and no, it is not during the evening. Hahaha). We came to the conclusion that most of the times it happens is when a "large load" 1500W is pulled and that load is switched off, the panels will then drop to 0W production and will never come up again.

The strange thing for me is, to fix it you either have to restart the inverter or more strange, pull the fuses and place them back again. During all this, the display is still showing the panels, the production itself is just 0W. The 0W will remain for what I think indefinitely if you do not perform the "reset" procedures.

Something tells me it's a software issue. What might be the issue here?

Thanks

Kind Regards

5 hours ago, JeremyJvR said:

Good day All,

I have a neighbor with an issue on his RCT Axking 5kw inverter. He had it for about 5 years now running only as a backup. He recently got 8x560W Panels installed. The system is running great, but every now and again the panels will produce 0W (and no, it is not during the evening. Hahaha). We came to the conclusion that most of the times it happens is when a "large load" 1500W is pulled and that load is switched off, the panels will then drop to 0W production and will never come up again.

The strange thing for me is, to fix it you either have to restart the inverter or more strange, pull the fuses and place them back again. During all this, the display is still showing the panels, the production itself is just 0W. The 0W will remain for what I think indefinitely if you do not perform the "reset" procedures.

Something tells me it's a software issue. What might be the issue here?

Thanks

Kind Regards

Give us a model number or picture of the side label on the inverter eg. SOL-I-AX-5K is one of the RCT 5k models. Also the connection configuration of the panels. Are they connected in 4 series 2 sets parallel 4S2P? The manufacturer or data sheet of the panels.

Edited September 30, 2025Sep 30 by TaliaB

17 hours ago, TaliaB said:

Give us a model number or picture of the side label on the inverter eg. SOL-I-AX-5K is one of the RCT 5k models. Also the connection configuration of the panels. Are they connected in 4 series 2 sets parallel 4S2P? The manufacturer or data sheet of the panels.

Hi, please see attached. Unfortunately I do not have any specs on the panels themselves, but you are correct. They are connected 4S2P. On the screen you can see that the inverter reads the panels, but the output from the panels are zero. This is in the middle of the day and as soon as the inverter is restarted or the fuses pulled the output changes to whatever the load is, on this day it was 950W.

1 hour ago, JeremyJvR said:

Hi, please see attached. Unfortunately I do not have any specs on the panels themselves, but you are correct. They are connected 4S2P. On the screen you can see that the inverter reads the panels, but the output from the panels are zero. This is in the middle of the day and as soon as the inverter is restarted or the fuses pulled the output changes to whatever the load is, on this day it was 950W.

Even though it displays zero, does it still supply the load from PV or is it pulling from the battery/eskom?

@JeremyJvR ,

Your neighbour can be very lucky he hasn't seen any smoke signals.!

4S2P PV configuration with 560W surely is a recipe for disaster. The typical Voc for a 560W panel is going to be around 50V. So 200V for the string. Way above the Voc Max of 145V, as can be seen on the label of the inverter.

Even at Vmp (normal operating voltage) of +-42V, 4S2 will give a good 164V @ 26A, enough to fry that MPPT. I surprised to see it didn't happen a long time ago. (when panels were upgraded).

The old panels from 5 years ago would most likely have been sub 300W panels, and the inverter would have been OK with that.

@Coulomb 's recommendation is always 2S max on these low voltage models when using these larger panels. Then parallel as many to stay within the current (or Wattage) spec of the MPPT.

14 minutes ago, Sidewinder said:

@JeremyJvR ,

Your neighbour can be very lucky he hasn't seen any smoke signals.!

4S2P PV configuration with 560W surely is a recipe for disaster. The typical Voc for a 560W panel is going to be around 50V. So 200V for the string. Way above the Voc Max of 145V, as can be seen on the label of the inverter.

Even at Vmp (normal operating voltage) of +-42V, 4S2 will give a good 164V @ 26A, enough to fry that MPPT. I surprised to see it didn't happen a long time ago. (when panels were upgraded).

The old panels from 5 years ago would most likely have been sub 300W panels, and the inverter would have been OK with that.

@Coulomb 's recommendation is always 2S max on these low voltage models when using these larger panels. Then parallel as many to stay within the current (or Wattage) spec of the MPPT.

Aha, so that will then explain why it only happens when higher loads are pulled, it then exceeds the specs. It still doesn't explain why it will keep pulling the load until the load is switched off.

The panels were only installed for the first time a few months ago. You know by one of these guys "that's been doing it for years". My neighbor asked him to come back and have a look, but he insists nothing is wrong.

1 minute ago, JeremyJvR said:

The panels were only installed for the first time a few months ago. You know by one of these guys "that's been doing it for years". My neighbor asked him to come back and have a look, but he insists nothing is wrong.

Rather avoid using that "installer".

It's a easy fix, but can be a schlepp, depending how and where the PV is installed.

1 minute ago, Sidewinder said:

Rather avoid using that "installer".

It's a easy fix, but can be a schlepp, depending how and where the PV is installed.

I agree, but something doesn't add up here. I am on my way to my neighbor to get onto the roof to confirm if this is the connection. I will revert back as soon as I can. Luckily it's a flat roof with tilted panels. So fairly easy to get to the connections.

Before you get up on the roof, just take a multimeter and measure the DC voltage at the PV disconnect/Inverter

51 minutes ago, Sidewinder said:

Before you get up on the roof, just take a multimeter and measure the DC voltage at the PV disconnect/Inverter

Ok I confirmed the connection. It is 2 strings made up of 2S2P each. Effectively giving 100V/28A (14A Panels) each, the 2 strings are then connected in Parallel again to bring it to 100V/56A. It is super cloudy today giving only about 80V