Why does my main house consumer unit trip when the inverter switched to AC backup?

[Tonyboy]

To observe a voltage between the PV input terminals when the array is disconnected from them and the inverter is producing an ac output using power form the battery is normal. The solar inverter is transformerless which means there is no air gap between the dc inputs (PV and battery) and the ac output. Due to the way the dc input is converted to a higher voltage and then switched in polarity at the mains frequency and also the earthed output neutral there is an alternating voltage waveform ( square wave shaped ) impressed across the PV+ and PV- inputs. It is usual and nothing to worry about but of course don’t touch live connections!

The 130V dc ( circa half the end to end array voltage) between array metal work and an earth rod is normal when the insulation resistance is uniformly distributed from the plus to minus side of the array and neither the pv+ nor the PV- is connected to earth which they should not be. They are left floating.

You should connect the array metal work to a local earth rod so that the touch potential between the metal work and local ground is small.

I will provide further advice on earthing arrangements for the SP5048 cabinet in a later email.

Regarding the F12 fault code - does it occur in battery only mode, PV only or both battery and PV? Does it occur when the inverter is not supplying the ac output Load ? Does it occur when the battery is fully charged and not supplying any ac output load? Does it occur on switch on of the inverter or some while later? Does it occur when PV only is supplying a small low wattage load? Does it occur battery only supplying small wattage load?

Hello Marconi and thanks for the reply

I will connect the earth from the pv rails and panels tomorrow, thanks for clearing up the question I posed.

Regarding the F12 fault. It originally occurred on Jan 29th when I had connected the batteries and the PV array as described in the V ltd directions. The batteries were at 49.0 vdc each and the array was producing 252 vdc if I remember correctly. It ran for a while producing about 400watts from the pv and then as far as I recall it went into the f12 fault.

I did not have any load connected as I was merely checking to see the inverter would charge the batteries from the PV.
This was at a point were I wanted to ensure the batteries were working and taking a charge etc.

The fault occurs whenever the inverter is in PV and battery mode I.e. I have the inverter set to provide power to the appliances from pv first then if not enough p.v the battery. That said I have not used the setup yet in any meaningful way as I am concerned about the issue of the inverter stopping on the F12 fault.

I can and have charged the batteries from the AC if I leave the solar consumer unit off and disconnect the ac out from the cabinet via the mcb/ rcd. (as we did in your experiment) I then just change the setup to USB and set the time to charge the batteries to full (so far this has only been 25%) as they were at about 75% when they arrived.

The fault seems to happen not long after I turn on the pv isolator and it shows the pv voltage and wattage on the front panel, soon after it starts to apply a charge to the batteries and then goes off on the fault. It seems to make a small bussing noise at the point it starts to charge and then soon after it goes to f12.
To clarify then, the inverter has not been charging the batteries when there has been an output load and the batteries are currently full. It did trip to F12 when charging the batteries and they were 75% and with no load applied.

It may be that I should try the charging again when we have some sunshine and I use some of the battery power beforehand and then turn on the pv with a small load applied to the solar output to the house? If this is a good idea I will probably need to wait a while as the weather here is overcast and forecast to be this week. I get very low wattage when it is like this so I will wait for a sunny day where I can apply a bit more to the inverter/batteries/load.

Many thanks and as ever I am very grateful.

Regards

Tonyboy

 

[marconi]

https://content.storefront7.co.za/s...56k48v/documents/rct-axpert-mks-iv-manual.pdf

see page 15 Program 2 - Maximum charging current (which is solar and utility currents). What do you have set? Try reducing maximum charging current. If it is set now to the default of 60A then reduce to 30A. If 40A then to 20A. ie whatever the max current set now then halve the current value. Then see if F12 happens when solar pv is charging battery.

 

[Tonyboy]

https://content.storefront7.co.za/s...56k48v/documents/rct-axpert-mks-iv-manual.pdf

see page 15 Program 2 - Maximum charging current (which is solar and utility currents). What do you have set? Try reducing maximum charging current. If it is set now to the default of 60A then reduce to 30A. If 40A then to 20A. ie whatever the max current set now then halve the current value. Then see if F12 happens when solar pv is charging battery.

Hello Marconi

I have had a look today and setting 02 is set to 10 amps by default for pylontech batteries setting number 05 .

I have the max ac charging current set to 10 amps as well. There is a note on setting 11 (ac charge current) regarding the setting in prog 2 stating that if setting in 2 is smaller than in 11 the inverter will apply charging current from 2 to the utility charger. There does not seem to be a way to reduce either of these settings further other than reduce the ac current to its minimum of 2 amps which seems like a very low setting for overnight charging. If this is an option I will surely try it if you think it will assist. At present the weather is overcast and no sun at all.

Many thanks as ever

Tonyboy

 

[marconi]

Thank you. As you say the charging current limits are already low at 10A so a very high charging current is not the cause of F12 as I mused it might be. I was 'hoping' you would say 60 to 120A!

Could you tell me the edition of software your Axpert inverter box is running please?

Are you or your wife musical? What frequency would you estimate the buzzing to be that you mentioned earlier? This site provides some tones to compare with:

 

[marconi]

Re: Program 13 page 19 'Setting voltage point back to battery mode when selecting “SBU” (SBU priority)' in program 01' of the manual reference in my #77 - what voltage do you have set as the threshold for point back?

 

[Tonyboy]

Re: Program 13 page 19 'Setting voltage point back to battery mode when selecting “SBU” (SBU priority)' in program 01' of the manual reference in my #77 - what voltage do you have set as the threshold for point back?

Hello Marconi

I have the voltage set to the default value of 54v I believe. I have been reluctant to alter too many things until I figure out their effect on the other settings and to be honest I have found the manual a bit hard work with the descriptions of some of the settings. I have noticed on other comments on this forum that Axpert call something one thing and then someone else says it is actually this or that or is described as a different parameter

I managed to get the inverter working yesterday while we had a bit of sun with the pv and a load out to a kettle. The kettle was only a 1 Kw but it allowed it to take some power from the batteries as well as the PV and then when the kettle had finished the pv added power to charge the batteries alone This is the first time for some time that the pv has put this much charge into the inverter and has over the period it was working 20 mins approx. charged the batteries to 100% albeit I got a number of f12 faults. The first occurred when I was getting 6.4 amps from the pv and after it occurred it re set and carried on charging. Once the batteries were fully charged and I had had a few more f12 faults I had to go out so I shut it all off.

I did video it, albeit the whole 20 minutes but I am trying to find a way that I could add it as an attachment that was not the 2 Gb it currently is.

I suppose it is some kind of progress to get the pv charging the batteries although the issue of the f12 fault seems to then stop any charging when it occurs. I am going to try to draw off more from the batteries over the coming week and see if when they are at 50% or so the pv will re charge them even with the f12 fault occurring.

Regards the noise from the inverter, it is not so much a tonal whine as such but more like the noise of an electrical connection being made, like a buzzing sound but it may be some part on the inverter kicking in to do a specific thing it just struck me as an odd sort of noise but it may be normal.

As ever I am grateful for the help and assistance

Regards

Tonyboy

 

[marconi]

Thank you. I will study what you have said. What do you have set for Program 12 page 18?

To attach a video you need to convert it to mp4. Dead easy once you know how. Try:

Online video converter to MP4 - https://video.online-convert.com/convert-to-mp4

 

[Tonyboy]

Thank you. I will study what you have said. What do you have set for Program 12 page 18?

To attach a video you need to convert it to mp4. Dead easy once you know how. Try:

Online video converter to MP4 - https://video.online-convert.com/convert-to-mp4

Hello Marconi

I Have program 12 set to the default values 46v and 5%, I think in the absence of any information from V ltd I decided to stick to the default values until I got some advice on the impact of any changes. Some are pre-set if you choose Pylontech in menu (5) p17

I have taken a video already on mp4 format but I get a message saying it is too large for the server to process, What is the file size limit for videos please?

Regards

Tonyboy

 

[marconi]

Hello Marconi

I Have program 12 set to the default values 46v and 5%, I think in the absence of any information from V ltd I decided to stick to the default values until I got some advice on the impact of any changes. Some are pre-set if you choose Pylontech in menu (5) p17

I have taken a video already on mp4 format but I get a message saying it is too large for the server to process, What is the file size limit for videos please?

Regards

Tonyboy

I will find out.

 

[marconi]

Those voltage checks for the two programs were to ensure there is some hysteresis between switching from utility to load in lieu of battery when battery voltage is 'low' and battery to load when its voltage is 'high' in lieu of utility. Without a voltage difference between the switch over thresholds there will be frequent changeovers perhaps at a high rate which would stress the electronics. The same hysteresis idea as employed in a room thermostat which you will be more familiar with.

I look forward to the results of your next trial with a more depleted battery being charged. That it does charge but stops on F12, resets and starts charging again only to be repeated suggests an instability of some sort perhaps of current or voltage. Or a defect which causes an instability in voltage level or current level.

Is there a date on the inverter box saying when it was manufactured? Electrolytic capacitors or which there are a few inside the box do not like being un energised for long periods and can fail or decay in value when they are after a long period dormant.

Quad Plus - https://www.quadplus.com/capacitor-reforming

 

[Tonyboy]

Those voltage checks for the two programs were to ensure there is some hysteresis between switching from utility to load in lieu of battery when battery voltage is 'low' and battery to load when its voltage is 'high' in lieu of utility. Without a voltage difference between the switch over thresholds there will be frequent changeovers perhaps at a high rate which would stress the electronics. The same hysteresis idea as employed in a room thermostat which you will be more familiar with.

I look forward to the results of your next trial with a more depleted battery being charged. That it does charge but stops on F12, resets and starts charging again only to be repeated suggests an instability of some sort perhaps of current or voltage. Or a defect which causes an instability in voltage level or current level.

Is there a date on the inverter box saying when it was manufactured? Electrolytic capacitors or which there are a few inside the box do not like being un energised for long periods and can fail or decay in value when they are after a long period dormant.

Quad Plus - https://www.quadplus.com/capacitor-reforming

Hello Marconi

the sticker on the inverter says 06/2022 so I am guessing the cabinet was assembled in the October of 2022 when we received it.
That said who knows how long the capacitors were in the factory before they were assembled into the inverter.

If the weather brightens up this weekend I will run the inverter in battery mode to deplete them to 50% or less and then see what happens when they are being charged from the PV.

Once I get an idea of how long it takes for the f12 fault to kick in and if it re sets and continues to charge how long before a repeat, I can go back to the supplier and sort out getting it changed or the money back. As it is within the first 6 months of taking ownership of it the supplier/manufacturer is obligated to prove it was working before I received it or they are likely to be told to change it or refund me.

Lets hope for a few bright days and a set of results to follow.

Regards and thanks as ever

Tonyboy