Which short-time delay (tsd) scale do we use for in and out settings from coordination study?

Circuit breaker test reports and coordination study reports often use the terms “IN” and “OUT” when referring to short-time or ground fault delay settings.  When the report indicates “OUT,” then it is referring to definite (fixed) time delay settings.  Likewise, when the report indicates “IN,” then this is referencing the i²t delay or i⁴t delay settings.

For more information about properly setting your WL circuit breakers, check out Chapter 9 of the WL Operator’s Manuals.  The latest versions of the WL Operator's Manuals can be found at: 

UL 1066 WL Circuit Breakers:  Click here

UL 489 WL Circuit Breakers:  Click here