Most solar systems used in everyday life are grid-connected and hybrid. As a result, many people do not know much about off-grid systems and are even more confused about whether an AC transfer switch is needed for off-grid systems. Here we will first briefly introduce off-grid systems and then answer the questions.
Transfer switch is a kind of low-voltage switch that can switch multiple circuits, and it can generally work normally at 50 Hz AC, voltage below 380V, and DC voltage below 220V. There are discrete and integrated types, which can switch the circuit from one group to another group of connected appliances.
Since some areas cannot be connected to the grid, they commonly choose to use off-grid solar systems, using solar panels as the main energy supply system. However, there are times when people may add a generator to power their home while using an off-grid system. So there are many people who want to know if an off-grid system needs an AC switch at this time.
It needs to be analysed according to the specific situation.
3.1 An off grid inverter is essential in an off-grid system. When solar panels are used to charge the batteries, a transfer switch is usually needed, but usually the inverter can act as the transfer switch. The transfer switch inside most inverters will have a selection of input and output AC power.
Most of the time the inverter is in inverter mode, in which the entire off-grid system chooses to use the power stored in the solar cells to provide the home’s electrical needs. When AC current is present in the inverter, the inverter switches to another mode. In this state, it will power the household loads directly from the AC current and store the excess power in the solar panels. If your inverter can accept two AC power sources and can also be interconverted with the inverter output, then there is no need to add an AC transfer switch under an off-grid system.
3.2 But if your inverter can only be connected to one AC power source and you want to make any of the AC power sources switch inputs with each other. Then you need to install an AC transfer switch in your solar off-grid system. This is a situation that people often encounter when using their RV.
But apart from this, there is another situation where you need to use an AC transfer switch. When we want to load some higher power equipment, using a high power generator, and the power of the generator exceeds the maximum power that the inverter can convert, then we need an AC transfer switch. For example, the maximum conversion power of the inverter is 6.6kw (30A*220VAC=6600W), while we use the generator to supply power to the load is 7.2kw (30A*240VAC==7200W). At this time the power of the generator exceeds the maximum conversion power of the inverter, and if you want the load appliances to work properly, you need to install an AC transfer switch. But overall, this situation is not as common as the first one.
