Inverters are designed to convert the direct current (DC) provided by a solar array or battery bank into alternating current (AC) for powering AC loads or feeding the AC into the power grid.
Inverters are designed with shut-off features to prevent damage to the battery bank or unsafe conditions in the power grid or overheating, low or high voltage input, or too-high power demand. The inverter has an LCD, error lights, and an audible alarm to signal the shutdown causes.
An inverter is designed to shut down or, in extreme situations, before any damage can be done to the input or output components of the system: The reasons for shutdown may be due to:
- Grid power outage
- Battery state of charge too low
- Over or Under Voltage condition on inverter input
- Inverter overheating due to being overloaded with AC loads
- Inverter overheating due to cooling fan failure
- Inverter component failure
Let’s review all the potential reasons your inverter may be shutting down.
Inverter Shutting Down Continually – Potential Reasons
Inverters are the sacrificial components in grid-tied and off-grid solar power systems. The inverter trip is due to a condition that may cause damage upstream or downstream or when the power input is unstable or interrupted.
Inverters work very hard in converting direct current from a solar array or battery bank to alternating current, and as a result, they generate heat that will deteriorate the components and circuitry over time, leading to a lifespan of typically ten years.
If your inverter is continuously shutting down, check for one or more of the following conditions:
- Sufficient sunlight to power the inverters as they can only work when they receive sufficient DC input current and voltage to power the connected AC loads. If the solar energy generated by the solar panels is insufficient to charge the battery bank or allow the inverter to generate AC compliant with the grid input parameters, the inverter will shut down.
The number of Productive Solar Hours per day in the US averages about five hours. Look up the PSH for your area and use this number to calculate how much solar power can be generated per day.
- Grid Power Supply Outage – In a grid power outage, the inverter must shut down to stop AC from being fed into the grid and endangering the technicians working to repair the grid supply.
The inverter continuously senses the grid power’s presence by measuring the grid’s voltage and frequency and adjusting the AC generated to match. The inverter must be UL certified to signify that it can shut down in the event of a power outage.
- The battery back may be discharged to a state of discharge that is below the programmed disconnect voltage. Lead-acid batteries should not be discharged below 50% of their maximum state of charge. Li-ion batteries can be discharged to almost 0% SOC, but keeping the SOC between 20% and 80% is recommended for the best battery life and recharge time.
- An inverter failure is seldom without prior warning. The inverter will run a self-test sequence when switched on to sense abnormal input conditions or an overload on the output side. Modern inverters are fitted with liquid crystal displays that indicate the error code.
A red LED will indicate an error mode and be accompanied by an audible beeping signal. The user can correct most such error messages, but in case of the inverter fails, it will have to be repaired or replaced.
- An overload of the inverter on the AC output side is the most likely cause of the inverter shutting down. Check that the sum of the power demand of the appliances connected to the inverter does not exceed 80% of the maximum rated output.
- The inverter may also shut down when it senses that the load demand on the output side is too high and will cause damage to the connected AC loads. Over and under-voltage protection on the inverter’s output side is required to protect the connected AC appliances from damage.
- Overheating the inverter components and circuitry will also result in a shutdown to prevent the inverter from burning out. The inverter cooling fans running continuously or becoming noisy is a sign that the inverter is overheating or overloading.
Check that the cooling fans’ air intakes are not blocked with dust and lint and that the fan blades are clean and running quietly. Ensure that the inverter has sufficient space around the heat sink housing to dissipate heat and is not close to other heat sources.
- Poor cable connections between the battery bank and the inverter or between the solar array and the inverter will also result in a shutdown. Cables of sufficient gauge must be selected and must be as short as possible to limit voltage drop.
Inverters are designed to shut down to protect the entire system from damage or unsafe conditions. Most household fires have their origin in failed electrical installations, and inverters that fail to shut down will overheat and may lead to a short circuit.
If your inverter continually keeps shutting down and you cannot find the root cause contact the installer or a qualified electrician to investigate the installation and test the inverter.
The risk of electrocution with an inverter is very high, and the current is sufficient to cause a fatal shock.
Continual Inverter Shut-Down Is A Protection Mode
An inverter is a central point connecting the DC power source to the AC loads. DC power supply can be a battery bank, solar panel array, wind power generator, or hydropower generator. All these DC power sources are variable in output as their ability to supply power is limited.
To protect them from damage due to voltage drops or spikes, the inverter senses their state of power supply and will shut down operation if:
- The battery state of charge (SOC) or depth of discharge (DOD) drops too low;
- When the sunlight intensity is insufficient to generate solar power from the panels;
- When the wind speed drops too below the generator’s ability to generate enough wind power;
- When the water flow is insufficient to drive the hydro-generator to produce hydropower.
The inverter also has built-in protection systems to protect it from overheating due to:
- Insufficient cooling due to poor heat dissipation;
- Cooling fans not providing sufficient cooling airflow;
- Inverter overheating due to excessive AC load demand.
The inverter will shut down when it detects any overheating or overloading conditions. It may also shut down due to defective internal components. If your inverter fails to startup, there must be a valid reason.
Start by checking the DC inputs like the battery SOC or the cable connections. Then check the inverter cooling fans and whether there is sufficient cooling space around the inverter. Finally, check that you do not have too many AC loads connected to the inverter.
If all your checks fail to get the inverter going again, it may be that you have some internal damage. Have the inverter checked out by a qualified technician and repaired or replaced if it is beyond repair.