The scenario
A 24V control relay starts a ventilation fan through a seal-in circuit; an on-delay timer enables automatic fan start after a preset time, while a manual selector overrides the timer for immediate operation.
What is in this drawing
Read the decisions behind it.
01
Use a seal-in contact CR1 to maintain the control relay after the start button is released
02
Apply a TON timer to delay fan start in auto mode
03
Place manual and auto paths in parallel so either condition can energize the fan relay
Reusable for any small motor or fan control where an automatic delay and manual override are required under 24V DC control.
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