An Auxiliary Holding Contact (Seal-In) on a typically NEMA starter is indicated by the terminal marking:

• A. A1 & A2
• B. 1 & 2
• C. S1 & S2
• D. K1 & K2

Answer: (A)

The holding (seal-in) circuit is a normally open auxiliary contact that, once the coil is energized, closes to provide a path that keeps current flowing to the coil after the start button is released. The terminal marking A1 and A2 identifies the coil terminals, and the auxiliary contact used for the seal-in is wired around those same terminals. So, when the coil is energized, the seal-in contact closes and a parallel path across A1–A2 keeps the coil energized, producing the latch effect. Other markings correspond to different parts of the starter or its contacts (main power paths, signaling contacts, or separate coil designs), not the hold-in path, which is why A1 and A2 is the correct indicator for the auxiliary holding contact.