Frequently asked questions
Can you reset an Ap LED light on the ComPacT NS micrologic trip unit?
FAQ000282472
16 June 2026
Product Line: Micrologic Trip units for ComPacT NS & MasterPact NW fixed and drawout types
Environment: Micrologic 2.0 A & E, Micrologic 5.0, 6.0, 7.0 A E & P types
33532, 33526, 33533, 33534
Resolution:
The AP LED is a self-protection/self-diagnostic indicator. The following are possible causes for Ap LED to lit up:
- The 24 VDC power supply voltage may not be stable. Sudden voltage drops and recovery can cause communication loss between the internal ASIC protection chip and the MCU.
- Presence of an EMC-generating source nearby, such as large capacitor switching (reactive power compensation systems) or frequency converters.
- Loose connections between the Micrologic unit and the current rating sensor lug, or at the rear-side trip unit base terminals.
Important point about clearing Ap LED
- If there is no tripping and the AP LED remains lit, the protection function is still operational. Pressing the reset button can clear the AP LED indication without compromising any protection features on the breaker.