Film-Tech Forum ARCHIVE: Time delay relay for a fan

This is topic Time delay relay for a fan in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Brandon Boutte (Member # 7843) on 02-15-2019, 04:36 PM:

I built a system to delay the shut down of a roof exhaust fan 10 minutes after the projector shut down using a time delay relay . https://www.valinonline.com/products/tdb24dl Either I cannot figure out the wiring diagram on it, or it's not made to do what I want it to do.

Any suggestions would be greatly appreciated.

Posted by Arnold Chase (Member # 7988) on 02-16-2019, 02:00 AM:

What you want is a classic "off-delay" setup. The key is that you need to find a 24 volt DC projector output that goes on and off with the projector fan(s). If you feed that to the relay control input (S1), then the TD relay trigger input will properly start the delay cycle. If you supply the delay relay power input with the same power that's feeding the fan(s), it will not work. The TD relay power input needs to be connected to an always-on power source.

Posted by Dave Macaulay (Member # 813) on 02-18-2019, 04:22 PM:

That is an odd choice for a fan delay relay but it will work.
To make it work you need a 24vdc supply to it all the time, and a "fan on" switch that switches the 24vdc to the initiate terminal. The delay starts when you switch off.
Usually we use a 120vac delay relay that works the same... saves providing the 24vdc.
This would be good if you use gpo triggered by lamp on to automate the exhaust fan though, the gpo can switch 24vdc safely.

Posted by Carsten Kurz (Member # 5396) on 02-18-2019, 04:50 PM:

Also an expensive choice. There are commodity mains supply delayed-off relays available for bathroom fans, staircase lighting etc. that can be bought for a fraction of that price.

- Carsten

Posted by Barry Floyd (Member # 385) on 02-18-2019, 07:57 PM:

I built our system here at the drive-in that do exactly what you describe you want to do.

Ours is set up to be triggered "ON" as soon as the playlist starts. At the end of the playlist, I have another cue which triggers the "Delay OFF" relay. Our Delay off relay can run up to 15 minutes after the playlist ends and shuts off the exhaust fans.

I used a "Schneider Electric TIME DELAY RELAY 211ACPSRX-6440. 24V AC/DC OFF DELAY"

I also have a 15 minute "Intermatic" spring wound mechanical timer wired into the same circuit that does the same thing IF our other one ever craps out on us.

Shoot me a private message with an email address, and I'll send you a PDF of the wiring schematic of how ours is done.

Have a look at this thread from several years ago...
Exhaust Fan Delay OFF Relay