meetyg

I have a 25A version and it is fairly silent. Also not running very hot. Around 42 degrees Celsius with thermal camera, after running for a few weeks.
I don't think that these take alot of current after initial power to the coil. Some of the better quality ones have an optimized circuit to reduce the current and heat to the coil after initial start up.
One advantage to using a 2NC and 2NO in the same unit, is that even if the coil fails, and the relay closes, you will not trip the input RCD because input AC will be disconnected.
I bought a few spare item of these relays, in case I get a failure.
I like your idea of indicators!

This is exactly what I have done with some other inverters:
It works well and is the best solution in my opinion. It disconnects AC Input to inverter so no chance of some kind of backfeed, and allows RCD to be used at output of inverter. Just remember that the N-G bond on the output needs to be before the output RCD (if you choose to install one on the output).

Thanks for your reply.
It sounds weird that they didn't include that AC board. I will have to check mine.
Anyways, I am using these cheap contactors from Aliexpress:
https://www.aliexpress.com/item/1005001339814821.html
So far no issues, running 24/7.
An industrial one should probably be even better.

So far I have i have finished the electrical installation but I don't have any panels to start normal operation :)
I do have 2 small 175W panels and an external mppt with which I am charging the battery (2x12V 300Ah) getting 1kWh on a good day..
I set it to operate in UTI mode meaning its an expensive UPS atm :)
But it does work nicely, even when I try to abuse it a little..
There are a few things to consider especially about battery and how much current you draw from it but so far I am more than happy with it
When I first got it I tried to plug it to grid to play with its menus etc but it didnt work.. I spoke with Anenji and they told me the units they sold last year didn't have an (AC UPS board) which they send me for free and once installed it works 100% as expected. Without it, if you don't have battery it will only work during the day
Then, once installed and wired I measured NG voltage but, with grid present it was always 0V regardless of power source.. when I disconnected grid though both L & N it showed 120V at its output N.
In Greece RCBO must disconnect both L & N so I cannot use a single pole one (I see those in UK?) and I must have one to comply with regulation.. but, with an RCBO at the input of the inverter in case it trips it will break NG bond so I came up with the solution of a relay with 2NO & 2NC ... someone just told me this might be "dangerous" and it is not safe to have the relays coil energized practically permanently etc.. which, to me is crap really when you use industrial grade relays ... the Metasol LG MC-32A is listed as relay for Power Plants FFS.. if its good for that use, its certainly good for mine!
Back to the Anenji, its 4kW only and I have set my battery to charge/discharge with only up to 1kW ... few days back I went to cook and turned on two appliances drawing 5.3kW! It simply went to bypass and worked for a few min without any problem, I then turned off one device to play safe.. the internal bypass relays are 40A rated though so nothing happened.. I plan repeating this "experiment" but with the inverter cover removed and having a thermal camera to see what is actually happening inside it. It should be fine ...
The other problem is that while you can set battery discharge current so you don't stress your battery this is problematic if there is no grid present at the time.. it simply ignores the setting so you must at least provide thick cables for the battery up to the inverter power rating to avoid them melting even if in normal use you only draw 1/4! I have installed a 63A fuse on the battery just to prevent this from happening.. this can be more elegant using current monitors and disconnecting part of the load if you can leaving only essentials..

This is exactly what I have done with some other inverters:
It works well and is the best solution in my opinion. It disconnects AC Input to inverter so no chance of some kind of backfeed, and allows RCD to be used at output of inverter. Just remember that the N-G bond on the output needs to be before the output RCD (if you choose to install one on the output).

@meetyg I did this preventive maintenance on my Axpert 5 years ago and sofar so good .

Circuit breakers have a trip curve for short circuit protection. This means that in order for them to open when a short circuit occurs, they need 3-5 times thier rated amperage to flow. This depends on the curve type. I think they most common curve type would be C, because B type, which is more sensitive, can cause nuisance tripping when power on large inductive loads (such as motors, compressors, etc...) because of the high initial inrush current needed to start up these loads.
Most HF inverters can sustain a load surge of 200% of thier continuous capacity, but only for a few seconds.
So it seems logical that the inverter tripped first, unless you have B curve breakers.

Circuit breakers have a trip curve for short circuit protection. This means that in order for them to open when a short circuit occurs, they need 3-5 times thier rated amperage to flow. This depends on the curve type. I think they most common curve type would be C, because B type, which is more sensitive, can cause nuisance tripping when power on large inductive loads (such as motors, compressors, etc...) because of the high initial inrush current needed to start up these loads.
Most HF inverters can sustain a load surge of 200% of thier continuous capacity, but only for a few seconds.
So it seems logical that the inverter tripped first, unless you have B curve breakers.

Circuit breakers have a trip curve for short circuit protection. This means that in order for them to open when a short circuit occurs, they need 3-5 times thier rated amperage to flow. This depends on the curve type. I think they most common curve type would be C, because B type, which is more sensitive, can cause nuisance tripping when power on large inductive loads (such as motors, compressors, etc...) because of the high initial inrush current needed to start up these loads.
Most HF inverters can sustain a load surge of 200% of thier continuous capacity, but only for a few seconds.
So it seems logical that the inverter tripped first, unless you have B curve breakers.

There are a few things to address here:
1. Unfortunately, it seems the MUST inverters are also plagued with the "premature float" bug, as in Axpert inverters. So you may be experiencing batteries thahaven'nit fully charged from solar during sun hours, a d therefore not lasting as long into the night.
I have played around with settings, but haven't had much success. A partial (not ideal) solution is to set the battery type as LI instead of USE. You can still change float and bulk voltages (set battery type to LI and then change voltage settings). It partially solves the problem, because the charging strategy is different: It charges up to float voltage first, holds this voltage for a while, then charges up to bulk. So it doesn't prematurely float. 
But there are downsides: First, being that while the lower float voltage is reached, it tends to hold it there for a certain time, taking less power from PV. 
Second, when it reaches bulk, it doesn't stop charging, it just keeps the battery at the voltage (forever ?) as long as solar power is sufficient.
But if you charge from solar only and have conservative float/bulk settings, I think it won't harm the battery too much. Lifepo4 doesn't like to be at high SOC for a long time, but since we are charging from solar, it shouldn't be more than a few hours (depending on how much solar you have).
2. Check setting #28, make sure it's enabled. This will allow you to make the most of your PV production.

3. I find setting #5 to be misleading: Its called "solar supply priority", but at least from my observations, it's not really prioritizing. It simply relies on different voltage thresholds (either setting #20  or #21, in regards to LBU/BLU respectively). 
So basically you need to choose how much you want to drain your battery, but via voltage settings. When in SBU mode, let's say you set #21 to 26.6v and setting #5 to BLU, it will drain the battery (when no solar) untill around 80% SOC (for Lifepo4) and then start powering loads from the grid. The next day, when solar power is available, it will continue powering the loads from the grid, until battery has reached setting #21. 
 
So in short, I find it hard to maximize PV usage with the MUST inverters.

My inverter doesn't have the float bug issue (That I'm aware), but I have been using some docker images from Github to make an MQTT and Node Red server where I can automatically read parameters from the inverter from a raspberry pi and push commands to the inverter automatically using Node Red and Mosquitto. Using a fork of the following software: https://github.com/ned-kelly/docker-voltronic-homeassistant. I haven't used the equalisation voltage parameter, but it must be in there if Watchpower can see it. I'm guessing you could use Node Red to switch on the inverter equalisation for a time in the morning and evening or even integrate over time how long the battery has been at equalisation voltage and switch based on that. Just make sure to synchronise docker with system time on the pi to make sure you get daylight savings time for your region.
 
Edit: Found the fork https://github.com/catalinbordan/docker-voltronic-homeassistant. Seems like no adaption I can find has found the equalisation parameter, but you could raise the float to the boost voltage for a time instead.

So just an update, I think I solved the problem.
As I suspected my N-G bond contactor de-energized (creating the N-G bond on the output) before inverter released its grid relay. Just enough to create two N-G bonds and therefore the output RCD tripped.
So I got a "true" delay off timer. They call these "true" because it has some sort of internal capacitor to hold a small current for the delay time, when power is lost. 
Other off-delay timers exist, but they need an external source of power for internal timer to work.
The off-delay timer holds the N-G bond contactor powered (open) for a few seconds, giving the inverter time to release it's grid relay.
Now the RCD doesn't trip anymore when I simulate a grid-down situation by turning off the grid breaker.
Here is the model I got (JSZ3F with DIN-rail backplate):
https://www.aliexpress.com/item/32969613011.html
The only downside is that it's a bit bulky for the DB, had to cut out some of the plastic for it to fit.

 
Thanks for all of your inputs.
I hope this helps others too.

So just an update, I think I solved the problem.
As I suspected my N-G bond contactor de-energized (creating the N-G bond on the output) before inverter released its grid relay. Just enough to create two N-G bonds and therefore the output RCD tripped.
So I got a "true" delay off timer. They call these "true" because it has some sort of internal capacitor to hold a small current for the delay time, when power is lost. 
Other off-delay timers exist, but they need an external source of power for internal timer to work.
The off-delay timer holds the N-G bond contactor powered (open) for a few seconds, giving the inverter time to release it's grid relay.
Now the RCD doesn't trip anymore when I simulate a grid-down situation by turning off the grid breaker.
Here is the model I got (JSZ3F with DIN-rail backplate):
https://www.aliexpress.com/item/32969613011.html
The only downside is that it's a bit bulky for the DB, had to cut out some of the plastic for it to fit.

 
Thanks for all of your inputs.
I hope this helps others too.

Interesting, I also have a PH-18 (3kw, 24v) and haven't noticed such an issue using SolarAssistant.
I'm using Raspberry Pi 4 also, with USB directly connected to the inverter USB port.
I have pulled the USB from the Pi and connected to PC, back and forth, never did I need to restart the Pi or the inverter.
Can you try to install SolarAssistant on your Pi (on a separate SD card) and see if it gives you problems ? 
You can install SolarAssistant with a trial license, so no need to buy just for this testing.
Have you tried using a different USB cable? Preferably one with a ferrite ring to decrease chance of interference.
Also, do you have a good stable power supply for the Pi 4? It's known to be power hungry (relatively that is...) and very finicky when it comes to power supply.
 

Interesting, I also have a PH-18 (3kw, 24v) and haven't noticed such an issue using SolarAssistant.
I'm using Raspberry Pi 4 also, with USB directly connected to the inverter USB port.
I have pulled the USB from the Pi and connected to PC, back and forth, never did I need to restart the Pi or the inverter.
Can you try to install SolarAssistant on your Pi (on a separate SD card) and see if it gives you problems ? 
You can install SolarAssistant with a trial license, so no need to buy just for this testing.
Have you tried using a different USB cable? Preferably one with a ferrite ring to decrease chance of interference.
Also, do you have a good stable power supply for the Pi 4? It's known to be power hungry (relatively that is...) and very finicky when it comes to power supply.
 

Sorry, I'm not from SA, rather from the Middle-East. But I found this forum very informative and it's members very educated and helpful.
So I hope it's OK that I'm participating here.
As opposed to other forums, where the majority of it's members are from the U.S.A, I find the information here more relevant to our local utility power system, including single-phase 220v systems. Also regulations are similar.

What modes are you running (output and charger source) ?
What do you have for parameters 20 and 21 (similar to Axpert 12 and 13 settings)?
I have a MUST too, but haven't tried to run it down fully. I did set my BMS cutoff lower than the inverter cutoff.
Anyways, I suspect that it will charge up the battery up to either setting 20 or 21 (depending on other settings, like LBU/BLU), and only then it will enable AC output from inverter. But I would also expect AC out to be in bypass mode during this charging, if grid is available.
 
But you got me thinking that I really need to check these edge cases with my setup, to make sure it can recover in case of a prolonged power outage and cloudy weather.
 

You don't have to set the equalisation voltage higher than the bulk voltage, so there is no contra-indication for equalisation just because you have an LFP battery that equalisation wasn't designed for. For working around the premature float bug, you use equalisation as essentially a way to prolong the bulk charge stage. But of course, a fixed time extension doesn't really solve the problem. It's just that for most people, that's all that there is.
It's not just in the first 50 seconds that the problem exists; it's any time that the charge power is reduced. In particular, when there is cloud or a large load robs the PV of spare charge current.
Think about the ideal charging situation. First, you charge the battery with as much current as you have available, up to the charge current limit. This is the bulk or Constant Current stage. Then there is an absorb stage: you limit the battery voltage so that you don't boil off the electrolyte, or cause bad reactions in a lithium battery. That's the Constant Voltage or absorb stage. Finally, the battery isn't taking much current, we declare it's full, and go to a different constant voltage stage, called the float stage. This is needed to keep a lead acid battery at 100% SoC, but it's also useful with lithium based batteries as an indication of the need for extra charge current. This extra charge current might be because the battery was called on to support the load, or because of losses. When the battery voltage falls below the float voltage, that's the signal to push current back into the battery, until the battery voltage reaches the float voltage setting again. If the battery voltage falls too low, we give up on the float stage and start a new bulk charge.
The transition from bulk to absorb is simple: has the battery voltage reached the bulk/absorb voltage setting. If so, we transition to the absorb stage. It's possible that the battery is called on to support the load and we fall below that voltage, in which case we're really back in bulk stage for a while. For that reason, Voltronic seem to call the absorb stage the bulk/absorb state. This transition is easy, and they don't screw that one up.
The problem is the transition from absorb to float stage. It's when the battery current falls below a threshold (for unpatched firmware, that's the maximum charge current divided by 5), BUT ONLY IF the battery voltage is near the bulk/absorb voltage setting. Otherwise, at the very first cloud, the battery would be declared full and solar charging would be completely useless. Here is the problem: they do check the battery voltage against the setting, but for reasons best known to the developers, they use the wrong setting! They use the float voltage setting, instead of the bulk/absorb voltage setting. In some firmwares, they compare the float and bulk/absorb settings, and choose the lowest of these, instead of the highest of these. It's that simple, and that's why the patch to fix it is so simple: we just change a branch if greater or equal to a branch if less. One byte. The problem is knowing which of the up to 256,000 bytes to change, and what to change it to.
No. As mentioned earlier, the problem can occur at any time, not just at the start of the charge, or at early times of the day. I suppose if you somehow paused charging when available PV power is low, that would work around the problem, while also wasting a fair bit of usable PV energy. It's also tricky knowing when available PV power is low. Is it low right now because there isn't any more to be had, or it it just that we don't have enough charging and/or AC-output load at present? You only know for sure when you need more than you can get.
I've wondered about this, not having a battery with a commercial BMS myself. But I don't think it helps; essentially, the BMS is adjusting the maximum charge current setting based on its knowledge of the instantaneous needs of the battery cells, rather than using a fixed value. The inverter's firmware still manages the stages, and hence the voltage threshold that it is aiming for.

Well, any inverter has a "no-load" consumption. Typically around 50w, some even as high as 100w.
Also, as you are using AGMs (as opposed to Lithium), they have a self discharge.
You are correct that in SUB mode, loads will only be powered by battery if Solar or Utility is unavailable. But, the self consumption of these inverters seems to always be taken from the batteries.
I see the same behavior on MUST 3K 24V AIO inverter, even in UTI mode, which is basically like a UPS.
What you need to do is to enable Utility charging in addition to solar charging.
You can set it as low as 1 or 2 amps of Utility charging, so that self consumption will be taken from the grid and not the batteries.
 

Actually, mine was connected through a socket. Not according to regulations, I know, but worked fine none the less. 
I would recommend connecting yours to a dedicated breaker in your consumer unit. I did not have any RCD tripping problems, but you might need to test your setup in order to decide if it should be before or after earth leakage/RCD.
 

I have this microinverter, bought from Aliexpress a few years ago. It's branded MarsRock, but is identical to the DEYE.
All I can say is that is has been working flawlessly for past 2.5 years or so.
However, I did not place it under the panels, rather in a shaded area.
The monitoring platform it uses is Solarman, which is a cloud platform.
It's OK, gives you the information you want, but the data is refreshed every 15 minutes or so, so not real-time monitoring.
The microinverter has a 60v input limit for each MPPT. My setup was 2 x 455w panels, each into a separate MPPT port, and another 4 x 100w (in 2s2p) to the third port.
My 455w panels are 144cells, half cut.
I think that as long as your panel is under the 60v input, you should be fine.
 
I recently took this microinverter out of service, because I wanted backup energy storage, so now my panels are connected to a hybrid All-in-one MUST inverter.

This model needs the RTU box:
https://wakedelectric.com/products/must-wifi-rtu
But a better solution is Solar Assistant:
https://solar-assistant.io/
It connects directly to the USB port on your Must Inverter. 
It runs on on a Raspberry Pi, so if you have one, you only need to buy the software. If not, you can buy the hardware from them too (or just buy a Raspberry Pi).
From then on, you can access Solar Assistant either from local wifi network, or remotely from the web.
I can confirm it works with my PH1800 Plus 3024.
BTW how did you handle the N-G bond with your inverter?  I'm still struggling with this issue, as the inverter doesn't bond automatically when in battery mode.

They seem to have a bug, where the entire charging cycle will not "reset" untill the battery is discharged enough.
As you mentioned, it seems the PV charger doesn't have this bug, but the utility charger does.
Some Axperts have this bug with PV too. 

@WillHza great informative post!
I'm not in SA, but I solved the N-G/N-E bond using an NC contactor.
As my MUST inverter internally connects the AC input N to AC out N whenever grid (AC IN) is available (no matter what mode it's running in, be it bypass or battery mode), it works perfectly.
When grid goes down, the contactor engages immediately and inverter supplies loads from battery/PV.
When grid come back, the contactor opens immediately, but the inverter takes a few seconds to return to grid. This causes the output to be floating (no N-G bond) for a few seconds. This is a compromise I'm willing to live with, since I have a 30mA  RCD on the output, which should sense any imbalance.
I have a manual transer switch, to switch the loads between inverter output and grid. But this is only for maintenance purposes, to bypass the inverter. In usual operation, the inverter takes care if the switching. I did have a problem at first, when I had the N-G bond done AFTER the transfer switch, BEFORE the output RCD: When grid came back, it took the contactor a second (probably less) to open, so I had two N-G bond for a short time. This short time was enough to make my main RCD break open. 
The solution to this was to do the N-G bond at the transfer switch INPUT from the inverter. This way, only if inverter output is being used by the loads, the N-G bond exists.
Another solution to handle this would be to bypass the main RCD, and connect AC IN from the main MCB, before the main RCD (of course it should have its own dedicated MCB, from the main MCB).
I hope this helps someone.
Disclaimer: I'm not a certified electrician, so do at your own risk.

Sorry for the late reply.
Just for some reference, here is a good explanation:
https://samlexamerica.com/differences-modified-sine-pure-sine-wave-power-inverters/