AnalogKid, I'm using the highest rated relay, but I have no control on the user side and the user might decide to connect an oversized load.
Diver300 yes, I assume the powered device is designed to meet the safety standards (both live and neutral insulated), but if only one pole of the relay disconnects the user might think there is no power as long as the device is not running and he might decide to disassemble the device. For example, the user might decide to control a bulb and he sees that the bulb is not emitting any light so he believes there is no power and decides to change the bulb. Although the bulb is insulated and meets the safety standards, once he decides to unscrew it, he creates a hazardous situation. Usually, domestic light commutators are installed on the live wire and once you put the commutator in the off position the bulb is not powered any more, but in my case I don't know which wire will be live or neutral (the European plug can be connected in any position), so the only solution I came with is a double pole relay which is still hazardous if one pole gets stuck.
Tony Stewart, I am using a 40A relay, but if the user decides to connect an inductive load, the relay can be damaged no matter how big it is. Just a fuse is not a solution because it should be installed on the live wire, but I have no control over wires, live can be swapped with neutral at any time.
Of course, the user would be blamed for changing a bulb without being sure there is no power or plugging an oversized load, but I think the best approach would be to design the device with some sort of protection and not blame the user.
If this situation can be anticipated, I think the best approach would be to design some sort of protection.