Literature

Technical Tips & FAQs

L8 and L9 Trip Curves and Trip Times on DC Applications

Question:

Are there trip curves and documentation for trip times when using L8 UL1077 supplemental protectors or L9 circuit breakers in DC applications?

Answer:

When using these products on DC applications or DC loads, refer to the published trip curves and times for AC applications as show in the current catalog or the UL Application Guide. Use a factor of 1.5 for the magnetic instantaneous trip X the continuous current rating (In).

The thermal trip times remain the same for both AC and DC applications. Refer to the table to calculate trip times for DC applications.

L8 Supplemental Protectors Instantaneous Trip Times

	multiple for AC Current (I/In)	becomes	multiple for DC Current (I/In)
B Trip Curve	3 to 5		4.5 to 7.5
C trip curve	5 to 10		7.5 to 15
D trip curve	10 to 20		15 to 30