On Wednesday, October 28, 2020 at 11:42:01 PM UTC-4, Daniel Fynn wrote:
My 'MUST' solar 3 phase Energy Storage Inverter(12KW, 48VDC) can charge alright but is not transferring power to the output (AC ). It shows an error code of 80 which says CAN fault in the manual i downloaded. I removed and re-fix all the communication cables but the problem persist.
Will happy with any help on how to go round the problem. Thanks.

I get two interpretations of an "80" fault code". The first is directly from MUST, the second from the International Standard for Inverter Fault Codes:

1.
Communication fault
CPU communication fault
1.Restart inverter.
2.If error message still exists, contact
the installation contractor or supplier.

2.
80 Derating occurred
The power supplied by the inverter was reduced to below the nominal power due to high temperature for more than10 minutes.
Check ventilation
Check heat dissipation

Trusting the first over the second, and expecting that this is a grid-tie device, and that connecting to the grid requires good synchronization, which is managed by a CPU - I suspect that it it is not a physical problem (per your re-securing the communication cables), I expect that the Grid-Tie CPU is fried. But, before admitting to that catastrophe, have you checked the 'other end' of the communication cables? In general, it would be useful to know where you are, the age of the unit, and other niceties. For the purposes of this reply, I am assuming (always dangerous):

Input Voltage: 48 VDC
Output Voltage: 230 VAC x 3; Y; Pure Sine Wave; H/N = 230 VAC
50 - 60 HZ to match utility

For the most part, these CPUs are EEPROMs, and if not under warranty, you may be able to get a "fix" directly from the supplier at a reasonable cost. Good to have anyway, and probably delivered to you in the form of a memory card.

Peter Wieck
Melrose Park, PA