Complete MUST Inverter Error Code & Troubleshooting Guide
At Solar Options Zimbabwe, we believe that an informed customer is an empowered customer. Knowing how your MUST, SVolt, or Evolt inverter operates is essential for maintaining energy independence and avoiding costly downtime.
Faults: Fan & Temperature (01-02)
Error 01: Fan is locked when inverter is off
Meaning: The inverter's cooling fan is obstructed, jammed, or has failed. It performs this check for safety before starting up.
Error 02: Inverter transformer over temperature
Meaning: The main transformer is too hot. This is often caused by sustained heavy loads, poor ventilation around the inverter, or high ambient temperatures in Zimbabwe.
Faults: Voltage & Output (03-08)
Error 03: Battery voltage is too high
Meaning: The battery voltage has exceeded the safe charging limit. This could be due to incorrect settings for your battery type.
Error 04: Battery voltage is too low
Meaning: The batteries are depleted. This is a protective shutdown to prevent damage and is very common during extended load shedding.
Error 05: Output short circuited
Meaning: The inverter has detected a dangerous short circuit in your house wiring or a connected appliance and has shut down to prevent a fire.
Error 06: Inverter output voltage is high
Meaning: The AC voltage being produced by the inverter is too high, likely due to an internal fault.
Error 07: Overload time out
Meaning: You have been drawing more power than the inverter's rated capacity for too long. This is a common fault when using multiple high-power appliances.
Error 08: Inverter bus voltage is too high
Meaning: The internal DC voltage has exceeded its safe limit, often due to a sudden drop in load while solar input is high.
Faults: System & Relay (09-22)
Error 09: Bus soft start failed
Meaning: An internal power-up sequence has failed, indicating a component issue.
Error 11: Main relay failed
Meaning: A critical internal switch has failed. This requires professional repair.
Error 21 & 22: Voltage sensor error
Meaning: An internal sensor measuring the AC output (21) or grid voltage (22) is faulty.
Faults: Sensor Errors (23-26)
Error 23, 24, 25: Current sensor error
Meaning: A fault with the internal sensor that measures the output (23), grid (24), or load (25) current.
Error 26: Inverter grid over current error
Meaning: The inverter has drawn too much current from the grid, possibly due to an external short or internal failure.
Faults: Temp & Current (27-42)
Error 27: Inverter radiator over temperature
Meaning: The inverter's heatsink is too hot. Ensure the unit has adequate ventilation and the fans are clean.
Error 31: Solar charger battery voltage class error
Meaning: There is a mismatch between the detected battery voltage and the inverter's settings (e.g., set to 48V but a 24V battery is detected).
Error 32 & 33: Solar charger current error
Meaning: The internal solar charge controller has a faulty sensor (32) or cannot control the charging current (33). This is a critical internal fault.
Error 41 & 42: Grid voltage low or high
Meaning: The incoming utility voltage from ZESA is outside the safe operating range, either too low (41) or too high (42).
Faults: Grid & Frequency (43-58)
Error 43 & 44: Grid frequency low or high
Meaning: The frequency of the utility supply is unstable and outside the safe range.
Error 51-58: Internal System Errors
Meaning: Codes in this range (e.g., Over current protection, Bus voltage too low, DC voltage in AC output, Battery connection open) all point to significant internal hardware or connection failures.
Understanding Warning Codes (61-77)
Warnings are pre-emptive alerts. They inform you of a condition that, if not addressed, could lead to a fault shutdown.
Warning 61 & 62: Fan is locked
Meaning: A fan is blocked or has failed while the inverter is running.
Warning 64: Low battery
Meaning: This is your chance to reduce your load before the system shuts down with an `Error 04`.
Warning 67: Overload
Meaning: You are drawing too much power. The inverter will beep to alert you before shutting down with `Error 07`.
Warning 70: Output power derating
Meaning: The inverter is getting hot and is automatically reducing its power to cope.
Warning 72 & 73: Solar charger stops
Meaning: Solar charging has paused because the battery is too low to accept charge safely (72) or the PV voltage is too high (73).
Your Options When You See a Fault Code
Option 1: User-Actionable Faults
For codes like Overload (`Error 07`) or Low Battery (`Error 04`), the solution is in your hands. Reduce the number of heavy appliances you are running or allow your batteries sufficient time to recharge from the sun. For overheating faults (`Error 02`, `Error 27`), ensure the inverter's fans are not blocked and the unit has clear space around it.
Option 2: System Check Faults
For codes related to grid voltage (`Error 41, 42`) or frequency (`Error 43, 44`), the issue is often with the utility supply. The inverter is simply protecting itself. Once the grid supply stabilizes, the inverter should return to normal operation.
Option 3: Professional Service Required
For most other codes, especially those indicating internal sensor (`21-26`), relay (`11`), or connection (`56`) failures, your best option is to contact a certified solar technician. Do not attempt to open the inverter or fix these issues yourself; it is dangerous and will likely void your warranty.
Need Expert Advice on Your Solar Options?
Understanding your system is the first step. If you're facing a persistent fault or planning a new installation, making the right choice is crucial. Contact Solar Options Zimbabwe for a professional consultation. We provide the expert advice you need to ensure your solar investment is reliable and perfectly suited to your needs.
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David (Sales)