Relay Logic Design

[Kilowatt#76]

Hi, I'm designing a lift station for a waster water treatment plant and originally there was a PLC but now it will be controlled with relay logic. I have a power fail relay that will be used in conjunction with a time delay relay. They do not want the pumps to start up right away after power is restored, there needs to be a 15 second delay. Any ideas on how the best way to do this? The coil of the power fail relay will be energized all the time when there is power(120VAC), once the power goes out the coil is de-energized. I just can't figure out which set of contacts to use? (N.O./N.C.) with the on delay relay(15 sec.) Any help would be much appreciated. Thanks!

Kilowatt#76

 

[OldBroadcastTech]

Well, I'm not an electrician by trade, nor do I portray one on TV, and I did NOT sleep at a Holiday Inn Express last night, but.....

I would make a S W A G that you use the N.O. contacts, which would close after the 15 second delay.

Get out you Grandpa's Simpson 260 and set it to R x 1 and connect it to the N O contacts and see what happens after 15 seconds (after unhooking the 120 V wires, of course).

just my $ 0.02...............

 

[gar]

230302-0739 EST

Kilowatt#76:

I will assume you have time delay relay with a NO ( normally open ) contact that when no power is applied to the time delay relay coil that the NO contact will remain open. After power is applied to the TD coil this contact remains open during a time delay period relative to when power is first applied to the time delay relay coil. At the end of that time delay period the the time delay relay contact closes, and remains closed so long as adequate power is applied to its coil..

At any time power is lost to the TD relay coil the relay output contact will immediately open, and not close again until power is again applied to the TD relay coil, and close only after this new TD period is ended.

.

 

[ptonsparky]

You only need the one timer.

 

[Kilowatt#76]

230302-0739 EST

Kilowatt#76:

I will assume you have time delay relay with a NO ( normally open ) contact that when no power is applied to the time delay relay coil that the NO contact will remain open. After power is applied to the TD coil this contact remains open during a time delay period relative to when power is first applied to the time delay relay coil. At the end of that time delay period the the time delay relay contact closes, and remains closed so long as adequate power is applied to its coil..

At any time power is lost to the TD relay coil the relay output contact will immediately open, and not close again until power is again applied to the TD relay coil, and close only after this new TD period is ended.

.

Thank you, I was over complicating it with trying to use another relay with the time delay and I just need the time delay relay.

 

[Kilowatt#76]

You only need the one timer.

Thanks!