I'm working on a switching device and I'm thinking of switching a hotel room lights + aircon + heater + tv, this is my my project for school. The Main Switch says 100A.. can a solid state relay of 40A sufficient to control that? I'm wondering why others sells 25A magnetic key car switch. Please help
The size of main fuses is always for protection of the supply chain and is chosen far over the maximum requirements of your local system. In case something goes very wrong with your local circuits the main fuse blows to prevent a supply problem with adjacent users not connected to your circuit.
Example: The mains fuse of your house prevents that in case something goes wrong in your house does not cause a problem in the house of your neighbours.
Now back to the hotelroom situation. Keycards are used in hotels, etc. and are layed out for mostly a little more then the requirements.
So if the hotel keycard has a switching capacity of 30A then an SSR of 40A could handle it as well. But a warning here is relevant. The SSR loses about 2V. Therefore the power dissipation could become 60 or 80W so the use of a large heatsink is needed.
A standard keycard system remains therefore much less expensive then a system with an SST in the power chain.