Control schematic help

[IamJon]

I have a controls schematic 99% done for the electrician. We have a pump and a valve. On run, the Pump starts, then the Valve openes. On stop, the Valve closes, then the pump shuts off. I've programmed myself into a corner so that whatever shuts the pump off will keep it from running when it wants to start again. I can't figure out how to reset my time delay relay. I'm trying to keep it simple, but it's got to function properly See attached. ETA: for a description of each line in the schematic we have: 1) motor start coil 2) valve close coil 3) time delay relay for motor shut off 4) valve opened limit switch 5) valve closed limit switch Obviously not a complete schematic, but I figured it would be enough. Thanks for looking. Schematic.pdf Edited November 30, 2010 by IamJon

[michael G]

In the TDR for the motor Add the Normally Closed of the Valve Open Coil - (You do not show it in your diagram but I think that you have it) I would also think about the valve limits - the outputs are turned off immediately when they reach the limit If the valve drifts off the limit it could cause you operational problems - passing product when it should not (Off State) or the opposite

[IamJon]

^ That won't work. I didn't show enough on the start. The pump will start, there's a time delay, then the valve opens. If I put the NC for the Valve Open coil, the motor won't latch until the valve starts opening. That would mean the operator would have to hold the Start button until the time delay was exceeded.

[JRoss]

Is there a time delay starting and stopping? Do you want to do that with only one timer? It would be easier to use two.

[IamJon]

We have two. I just didn't put the start logic in what I posted here.

[michael G]

Here's a solution Need N/C on the Stop PB and one extra relay I could not do it without the extra relay - Someone else can have a go

[BobLfoot]

Is it just me being cynical or does this mean. We start and dead-head the pump then open the valve. We Dead-head the pump by closing the valve and then turn it off?

[BobLfoot]

I think this does what the original poster asked for in 4 rungs, but Caveat Emptor I wouldn't use this code on my pump station.

[IamJon]

Yes, the pump dead heads for a second or two. We ended up changing the TDR to a delay on operate, and put contacts for the motor running and a new relay in front of it. See attached. Schematic-1.pdf

[Sleepy Wombat]

Its funny, as what you call a schematic I would call a "mud map". Once drawn up properly ie with a drawing package then it becomes a schematic.... Also, for the price these days I would have used a "smart relay" aka omron zen, ab ----, what ever as the flexibility is fantastic.

[BobLfoot]

If it works good enough. Your "napkin sketch" is beyond my ability to follow. I don't see how open waits for motor running for one thing.

[IamJon]

I apologize for the confusion. I was heading out of the office when I posted it, so I was in a hurry, but didn't want to scan and post the entire thing.

[sammy]

Use a float switch..