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High Bus Voltage Error on MUST 5KVA Inverter


Sheyn

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Hi there

I am having issues with my MUST inverter periodically showing error 8 - High Bus Voltage Error code. Herewith my setup below:

1. MUST 5KVA 
2. 12x 330W Canadian Solar Panels
3. 2x Pylontech US3000 batteries

We have had no power due to a fault for a few weeks, so have been running on panels during the day and batteries at night. I have noticed that if i turn over to generator at the end of the day, after the batteries are charged (needed to run my stove), the error comes up on the inverter after about an hour or two of running the generator. Yesterday we had our grid power restored in the afternoon after the fault was repaired. In the evening when batteries were fully charged and still on grid power, the error came up again. Had to restart the inverter and switch off grid power, so that batteries were no longer charging. 

Any suggestions as to what I can try?

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  • 1 year later...

Just installed a new  48V 5KVA inverter with 4x 100Ah gel batteries.  Backup DB has 25A input and output breakers with 3-way bypass switch and 125A DC circuit breaker. When testing the system I switch off main switch on main DB to activate the backup system. The changeover from ESKOM to inverter is faultless BUT the lights does a short flick every 10 - 20 seconds. A typical relay click is heard from the inverter. Red light on screen shows code 08 - Bus voltage to high. How can I fix this problem. Thanks Johan.

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3 hours ago, JLER3 said:

Just installed a new  48V 5KVA inverter

Hopefully it's not a Must brand (as per the topic title), as these are mostly clones of dubious quality.

3 hours ago, JLER3 said:

Red light on screen shows code 08 - Bus voltage to high.

This can be caused by electrical leakage to earth from the PV panels. Does it happen more often after rain or hosing the panels?

You haven't mentioned panels, so if you don't have any, that rules out my theory.

If you do have panels, there are various workarounds, like disconnecting the panels at night via a relay. Pretty inconvenient, but more convenient than replacing your panels.

It's also possible that you simply have a faulty inverter. Since it's new, if it's not the panels leaking, then you should be able to get it replaced or repaired under warranty.

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Coulomb. No PV panels installed yet. Just want to use the system as a backup during load shedding. Switchover from Utility to Inverter very smooth.  Code 08 - Bus voltage to high. What I noticed is that during while running in backup mode the frequency is only 41Hz instead of 50 Hz. 

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23 hours ago, JLER3 said:

What I noticed is that during while running in backup mode the frequency is only 41Hz instead of 50 Hz. 

Do you mean during load shedding, when there is no AC input?

And it's close to 50 Hz when AC-in is present?

Is this 41 Hz from the inverter (via monitoring software), or via a multimeter?

If from the inverter, can you confirm with a multimeter that can measure frequency?

Edit: Running at 41 Hz sounds serious, and may be a big clue to what's going on.

Edited by Coulomb
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  • 9 months later...

In my case the bus voltage overload error was because my "Bulk Charging Voltage" was too high.

I lowered mine to 27.1 v and never had the problem again.

This will of course be different for your setup.

Basically the   Battery Cutoff voltage is the lowest you want your battery to go, and the Bulk Charging voltage the highest.

I don't have BMS in my batteries - LifeP04, so I have to manage overvoltage form inverter.

 

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