Error code 64

[Heather]

Apologies if this is a really basic question as I haven't managed to find the answer elsewhere.

My system was installed 2 weeks ago and yesterday I had an 'error code 64 - DC Bus high' in the afternoon.

Can anyone explain what this means please? What do I need to do about it? System is working normally. Do I need to panic???

Thanks

[Dave Foster]

I wouldn’t panic, it will recover from the error but i’d suggest you contact your installer and tell them.

It tends to happen when you have a large number of panels on a solar string when they are under full sun (around midday), if the power exceeds the string limits the inverter will cut the solar generation until the power drops again - ironically it happens more at this time of year because the sun is so strong but the ambient temperature is low, the panels derate as they get warmer in summer.

It’s frustrating as you lose a bit of solar generation but it does no harm - your installer should be able to re-configure your strings to avoid this.

[Heather]

Thanks for the reply, very helpful.

[MH2024]

Hello.
I wonder if someone would be able to give some advice please.

I have been getting these same error messages. “Error code 64 DC Bus volt is high”. Wondering if ok.

Apologies if I do not have the right terminology.
I had installed on Weds (scaffold is still up)
16x Longi 430W Panels 6.8kW system size.
Fox H1 5.0-E inverter
Fox mira HV25 batteries with total capacity of 7,370wh

(It was originally due to be 405W or 415W panels but I was told I was being provided 430W panels at no extra cost because i had a delay on my order)

I have had this error code show four times on two different days. Usually around the middle of the day when it is bright outside. All normal apart from this.

According to FoxCloud2.0
Days since commissioning
Day one: 17.6kWh solar produced no errors logged.
Day two: 22.5kWh solar produced. Four error code 64 middle of the day
Day three: 22.8kWh solar produced no errors logged.
Day four (today up to 4pm): 24.2kWh solar produced. Four error code 64 around middle of the day.

I noticed the inverter PV1 310.9v and PV2 310.5v around the time of the latest error log entry.

Is this clipping? (Something I saw mentioned when trying to search online for info).
It did last time switch to 0w solar production briefly so seemed to be akin to a reset rather than throttling back. But not sure.

Should I be worried at all?
I appreciate max PV peak will not be hit all day everyday. (Though we are April so not sure what happens in the summer).

Does this cause any problems for the inverter or warranty?

I am hoping the system has been designed within tolerances.

I read that greater solar production earlier in the day and later in the day more than offsets any clipping in the middle of the day.

Just a bit cautious as I understand that inverters are not a cheap component within a solar setup.

Thank you for sharing any thoughts.

[Dave Foster]

From what you have said and your string voltages, it sounds like you have 2 strings with 8 panels on each string.

Just to go slightly into technical territory to explain it, you have 8 Longi 430W panels which can output 430W at 33.16V (that is their maximum power point voltage), they are in series so the voltage will be multiplied by 8.

So to do the maths 8 * 430W = 3,440W and the voltage they will be providing that at is (33.16V * 8) = 265.28V, the current flowing will be ( A = W/V ) which is 12.97A and the maximum current the FoxESS inverter will allow is 13.5A peak (so in theory you are in limits).

The voltage of 310V you are seeing is the panels open circuit voltage (39.43V) which is what happens when the inverter powers off the string (it goes open circuit)

Whilst their maximum current is just below the inverters maximum limit, the problem occurs because the panels are rated at 430W at 25C with 1000M3 of solar irradiance - they actually reduce in power as the temperature increases, but equally they are slightly more powerful as the temperature falls and so on a summers day they won't get much past their maximum power, but on a cold day at this time of year their power is just a little bit too high.

What that means is that panels produce more than the 13.5A limit the inverter has, and so the inverter will raise an alarm and shut the string down, as soon as the inverter works out that the power has fallen below it's maximum limit it will turn the string back on again, which is what you are seeing.

Whilst it sounds the same as clipping, it is a different thing - with clipping your panels are generating more power than the inverter is allowed to output (as you have an H1 5.0, your max power is 5 kW) so if you exceed 5kW the inverter will reduce the power point so that it maintains it's maximum power. What you are seeing is it exceed the maximum string current which results in an alarm and it turning off the string temporarily until it can safely turn it back on.

Ironically had the lower powered panels been installed you probably wouldn't have seen this problem.

So a couple of things to run through -

• It's not dangerous, the inverter is protecting itself from the over power limit and it will recover as soon as the power drops again.

• I would normally say speak to your installer about this to re-configure your strings, but as they are both maxed out there are no simple options, ideally the smaller panels would have been the better solution.

• But if it doesn't happen very often, and recovers quickly you should find that the problem reduces as the weather warms up and it likely won't happen at all in summer - in winter it won't happen either, it is just the 'goldilocks' point you are in at the moment with brand new panels, high solar elevation, strong sun but cold air temp and panels - so only likely to occur in April or October.

• As your panels age their power will (slowly) reduce, they will also get debris and dust on them, all of which will gradually reduce the maximum power they can ever achieve.

A few things to think about there, but if it doesn't happen too much and it gets better as we head towards summer - I would say leave it as it is, given a bit of time the panels won't be as good as they were when they were new so it shouldn't happen at all.

I would definitely mention it to your installer, they need to know and there maybe something they can do to limit it - but for the reasons I mentioned i'm hoping that the problem will remove itself naturally over time.

[MH2024]

Thank you very much Dave.
Your knowledge and guidance is greatly appreciated.
I will keep an eye on things.

[inanckeskin]

Hello,

Last night, during heavy rain, the grid electricity was cut off. During this time, the inverter displayed a “DC Bus Volt is High” error. Immediately afterward, the lights connected to the battery in the house started turning on and off. They stayed on for a few seconds and then turned off again, repeating this cycle 7-8 times.

I switched off the four-pole Foxess breaker connected to the inverter from the fuse box and stopped all the lights and sockets connected to the battery. After 30-40 seconds, I turned it back on, and everything returned to normal.

Why might the inverter have given this error when the weather was completely dark and rainy? And at that moment, there is no electricity generation at all.
And why did the lights repeatedly turn on and off right after?

Thank you.

[Dave Foster]

Do you have any form of EPS installed? - it sounds as though when the grid was disconnected you lost your earth connection and the inverter was left floating and in an indeterminate state. I'm guessing you have mostly LED light bulbs as the flickering would only have needed a small sense current from the inverter. - i've seen this happen shortly after a firmware update but a full shutdown reset cures this (which you have now done) as it will not start up unless it can detect grid voltage.

[SunnyD]

Hi
I'm looking for some help/guidance please.
I had my inverter/batteries installed on 7 Nov 24.
I've set up a number of forced charge/self use times using the mode scheduler to marry up with the Octopus Cosy tariff but have noticed some anomalies, for example, when it flips to self use, the batteries have not discharged as expected. This is intermittent - maybe 3 times a week but really frustrating as it means i'm using peak rate electricity
I looked through the fault history, which shows daily (sometimes multiple times) error code 64.
I can't be sure the two are related as I haven't cross-referenced the flat spots and the error code timings. Today we had two flat spots, batteries were full at 6.24am and scheduled to flip to self use at 7am. They didn't discharge until 9.51am. This afternoon the batteries were scheduled to charge between 1pm and 3.59pm. They got to 90% soc at 2.21pm and discharged the surplus solar being generated (seriously, we had dazzling sunshine!) However, they continued to charge until 4.27pm which is odd. Even weirder is that they charged to 100% from the grid when they are set at 90% max soc. The batteries then failed to discharge until 5.57pm.
As for the code 64 error messages, these occurred as follows:-
6.41 (up arrow)
6.44 (down arrow)
6.48 (up arrow)
7.00 (down arrow)
15.27 (up arrow)
15.37 (down arrow)

Any guidance gratefully received.

[Dave Foster]

Error 64 is DC bus high i.e. it is reporting either the batteries or solar as being overvolt and that will result in erratic behaviour as you describe.

Can you describe your system in more detail please, I can see you have a T series (which doesn't support batteries), what model is the inverter with the batteries attached ? i.e. H, AC1, KH and what size 5, 6, 9kW - also you have listed solar panels with enphase but that is an ac converter and the t-series supports only dc inputs so they can't be connected there, what panels are on the T-series..

[SunnyD]

Hi Dave, thanks for the reply.

It looks like I actually have the AC3 10-E inverter connected to the panels and batteries.

We are south/south east facing hence the microinverters which were originally installed 18 months ago across all 3 phases.

We decided to retrofit an inverter/batteries late last year.

The inverter and batteries are all within the thermal envelope (plant room) which is constantly ~28C

Ive had two error code 64s this morning.

Cheers

[Dave Foster]

Can you go to the foxesscloud.com website, log in and go to the Inverter, Details screen - it’s the one that has the ‘Energy Flow’ under the ‘Device Status’ at the bottom of that screen is a blank graph with a drop down menu that allows you to select the sensors you want to view.

If you can select PV1Volt, PV2Volt, BatVolt and RVolt and click search.

If you can screen shot and attach the graph here and the approx times of your error 64 so I can cross check against those traces please.

[SunnyD]

Thanks Dave - I think this is what you are looking for.

[SunnyD]

the batteries received a full charge between 4-7am
I have set the cursor at just after 7am when the batteries were supposed to start discharging but you'll see that they didnt until much later.
I was about to confirm when the error code happened but there wasnt one today!
Ok, I'll try that again

[SunnyD]

ok, so here is the screenshot with the exact time when the error code 64 occurred

[Dave Foster]

Ok yes your inverter is dropping out when it has the fault and falling back to its checking state which is why you’re seeing the charge interrupted as the inverter has gone off-line in error.

There is nothing obvious in the traces, the voltages are in line with what you would expect but what they don’t show is fast changes that might cause an error but not be visible in the graphs.

You might want to ask your installer back as I would suggest a thorough check of all the dc connections between the inverter and the battery and that an earth is in place between the two. I think also worth making sure the inverter has the latest versions of Master/Manager firmware installed - Fox service can check and update the firmware for you if you email them with your inverter serial number.