I have two mains power inputs (in case one fails, the other is likely to still work), but the device only has one power supply, so I decided to use a relay to switch between the inputs (the device should be able to cope with a momentary interruption during the switching), like this:
In theory and for low voltages this should work just fine. When the primary input fails, the relay switches to the backup input. Is there any potential problem I should be aware of when using this for 230V?
Connected to this: is there a way to add a fuse to this circuit so if something (the relay or the device) shorts out that fuse blows instead of tripping the circuit breaker? Maybe some resistor to limit the short circuit current?