de-rating

[derekleffew]

(Alternatively spelled as "derating." Setting an artificial upper limit less than the actual capacity. For example, in some uses a circuit breaker may have a de-rating factor of 80%, thus a 20A breaker is only loaded to 16A (1920W).

From http://www.theriac.org/DeskReference/viewDocument.php?id=194 :

The practice of limiting electrical, thermal and mechanical stress on parts, in a given design application, to levels that are below their specified ratings or their proven capabilities in order to enhance reliability.