In an electrical installation should the circuit breaker automatically trip when hot and neutral touch or only when hot and ground touch?

100% current flow between hot and neutral or ground will trip a breaker. That's because the current flow will exceed the ampacity of the breaker. You always need something in between-lights, motor, heater etc. In older panels, ground and neutral were conneced to the same bar so it didn't make any difference, any contact would trip the breaker.

100% current flow between hot and neutral or ground will trip a breaker. Thats because the current flow will exceed the ampacity of the breaker. You always need something in between-lights, motor, heater etc. In older panels, ground and neutral were conneced to the same bar so it didn't make any difference, any contact would trip the breaker.

Thank you for your help