Hager NCN463N C63 MCB Temperature Derating MCBs are designed and calibrated to carry their rated current and to operate within their designated thermal time/current zone at 30°C. Testing is carried out with the breaker mounted singly in a vertical plane in a controlled environment. Therefore if the circuit breaker is required to operate in conditions which differ from the reference conditions, certain factors have to be applied to the standard data. For instance if the circuit breaker is required to operate in a higher ambient temperature other than 300 C it will require progressively less current to trip within the designated time/current zone,
