I'm trying to run two fans when there is a call for heat but I want fan 2 to shut off a few minutes later. I don't have an off delay timer however I do have an on-delay timer and a relay. I know it can work I just can't seem to figure it out.

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    \$\begingroup\$ (1) Mains? (2) Is the on-off switch a double-throw type (NO and NC contact)? (3) Is the timer NO, NC or changeover? Hit the edit link. \$\endgroup\$
    – Transistor
    Commented May 4, 2020 at 19:16
  • \$\begingroup\$ There's no need to edit the title after it's solved. Marking an answer as accepted marks the question as solved. \$\endgroup\$
    – Hearth
    Commented May 6, 2020 at 22:14

1 Answer 1



simulate this circuit – Schematic created using CircuitLab

Figure 1. Timing diagram and circuit schematic.

How it works:

  • TIMER1 is normally energised but when power is first switched on at the mains FAN2 will run until the timer times out.
  • When SW1 is closed FAN1 will run, RLY1 will be energised and power off TIMER closing its NC contact causing FAN2 to run.
  • When SW1 is opened FAN1 will switch off and RLY1 will drop out.
  • TIMER will begin timing and when the set time has elapsed the TIMER contact will switch to the NO position switching off FAN2.

This pre-supposes that both the relay and timer have changeover contacts (but you gave no details or datasheet links).

  • \$\begingroup\$ Nope, This is exactly what I have! I apologize for the vagueness because I wasn't sure at first either. \$\endgroup\$
    – Bigpaa
    Commented May 5, 2020 at 19:11
  • \$\begingroup\$ Good. If it works then please accept the answer to indicate that it has been solved. \$\endgroup\$
    – Transistor
    Commented May 5, 2020 at 19:31
  • \$\begingroup\$ @Bigpaa: The "accept" button is located with the up/downvote buttons. When you accept the answer is marked in green on this page and the question is marked in green on the questions index. No need for "[solved]" in the title. \$\endgroup\$
    – Transistor
    Commented May 7, 2020 at 6:18

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