What is the primary function of a seal-in circuit in relay logic?

• A. Provides self-holding to keep load energized after switch release
• B. Introduces a timing delay
• C. Remains continuously off until power cycled
• D. Short-circuits the circuit

Answer: (A)

Seal-in circuits provide a self-holding path so the coil stays energized after the control switch is released. When the relay is momentarily energized (for example by a start pushbutton), one of the relay’s contacts closes and forms a parallel path that bypasses the momentary switch. This allows current to continue flowing to the coil, keeping the load energized even after you let go of the start button. The circuit remains latched until a stop condition opens the path (often a normally closed stop button or an interlock), at which point the relay coil de-energizes and the latch releases. This behavior is precisely why a seal-in circuit is used: to maintain energized state without continuous operator action. It does not introduce a delay, it does not keep the circuit off, and it is not a short circuit.