The 7621 / 7620 fault is typically associated with a communication disturbance in the inverter stacks and often shows a 6422 to indicate the stack is in an unknown state.
Common reasons for this alarm are:
- Firmware mismatch
- Fiberoptic cables or ports dirty/damaged
- Failed DST board or related connection
- Failed Stack or internal components to the stack
- Failed SC30Cont
- Failed SC30ACC board or related connection
- Failed or improperly timed Q30 relay
This is common if you've recently replaced a part or done work the inverter that resulted in an unsuccessful firmware load or a part which had a different version pre-installed. Typically, your inverter will hold the firmware so you can simply reinstall and this should update all of the boards. To check the firmware, navigate to the configuration menu, click "Update" and view the "Device Status" window which shows all of the relevant firmware versions. Please see the screenshot.
Once you've identified a firmware mismatch, you can update the firmware using the service login and navigating to the "Update" tab within the "Update" section of the interface. Please see screenshot below. Ensure the inverter is in stop, has been power cycled, and we recommend performing another power cycle once the inverter successfully updates the firmware.
Fiberoptic Cables or Ports Dirty/Damaged
Consider cleaning out the fiberoptic ports on all of the DST boards and the SC30Cont. This can be done by using isopropyl alcohol and a gentle applicator or by carefully using compressed air to blow dust out of the ports. Please see the image below of the ports located on the SC30Cont and one of the three DST boards in the stacks. There is also one more fiberoptic cable which goes to the ACC board, but is not in the image below.
Furthermore, the fiber cables can be tested - tools can be very expensive - or just jumpered out with a known good set from a bulkhead ready spare. If only one stack is causing the problem, consider swapping cables between stacks. DO NOT SWAP ONE END OF A CABLE. The entire cable should be moved.
Failed DST Board or Related Connection
Please see the image of the DST board above with the single fiberoptic connection. We recommend checking all related connections - the ribbon cables, the power cables on the left and right, the fiberoptic port, and check the board for signs of damage. If this fails to resolve the problem, consider replacing the board entirely, or exchanging with a neighboring cube to review the data/characteristics to see if the fault follows the board to the new stack.
Failed Stack or Internal Components to the Stacks
It is possible that the stack has suffered an internal failure. If this is determined to be the case, then consider replacing the entire stack. Please contact Solar Support if you'd like help in procuring a more robust stack with warranty for the future, or if you'd like to consider refurbishment.
This is a relatively simple component to replace, therefore it can be exchanged prior to the more laborious parts, however there are typically other symptoms associated with an SC30Cont failure. However, if all other components have not yielded results, it is possible that the SC30Cont has had a port failure or other related internal failure. Consider replacing this board, but be sure to update the firmware. See image above of the board with four (4) fiberoptic ports outlined.
Failed SC30ACC Board or Related Connection
This is also a relatively simple component to replace, therefore this can be exchanged prior to the more laborious parts. Typically, you may find other fault codes or symptoms with a failed ACC, but it possible to have a 7620/7621 fault generated from a loss in the fiber port to the ACC. Be sure to check the fiberoptic cable and port prior to replacing the board.
Failed or Improperly Timed Q30 Relay
The Q30 relay helps protect components from the voltage spikes which could trigger a protection mode that requires a reset. The timing and coordination is set via firmware. This is a very uncommon fault to have. If you think you may have a problem with the Q30 relay, consider jumpering a single phase directly to the coil input on A1 so that relay remains closed permanently when control power is applied. This could occasionally cause the buffer module to enter protect mode, but this will likely be far more infrequent than the 7620 faults. Once this is temporarily bypassed, contact Solar Support for help in understanding how to resolve permanently.
We genuinely hope this article was helpful. Now, help us stay sharp! Please share any notes you have so that we can keep supplying you with the most up-to-date information. Thanks and stay safe!