Relay wiring assistance

[dconner2230]

I have 3 locations that have a relay controlling a pump, each site is several miles from each other and when my SCADA system calls for RUN all three relays energize at the same time. What I need is a local control that allows only 2 pumps to run at the same time but they need to alternate, (example) 1&2 when called then 1&3 on next call then 2&3 then back to beginning. Each site has a 12vdc relay interrupting the Auto of a selector switch, I was thinking of alternating relays for the control circuit but would like help in a wiring diagram showing this solution.

 

[Megawatt]

I have 3 locations that have a relay controlling a pump, each site is several miles from each other and when my SCADA system calls for RUN all three relays energize at the same time. What I need is a local control that allows only 2 pumps to run at the same time but they need to alternate, (example) 1&2 when called then 1&3 on next call then 2&3 then back to beginning. Each site has a 12vdc relay interrupting the Auto of a selector switch, I was thinking of alternating relays for the control circuit but would like help in a wiring diagram showing this solution.

dconner since it’s pumps I’m assuming that you have motor starters which should have 2 sets of dry contacts with 1 being NC and the other NO. Having said that you could use the auxiliary contacts to stop any motor from starting. I can’t draw you a wiring diagram on my phone. I would see if you can do that without adding another relay. Good luck

 

[dconner2230]

dconner since it’s pumps I’m assuming that you have motor starters which should have 2 sets of dry contacts with 1 being NC and the other NO. Having said that you could use the auxiliary contacts to stop any motor from starting. I can’t draw you a wiring diagram on my phone. I would see if you can do that without adding another relay. Good luck

I failed to mention the control relays come on from a Digital Out on my RTU, this being said I need to locally make each location skip a command on cycle thus the need for a alternating relay. In essence each location has a wireless controller that all receive the command on. The issue is how can I make the sites come on in this sequence. 1&2 2&3 1&3

 

[Megawatt]

I failed to mention the control relays come on from a Digital Out on my RTU, this being said I need to locally make each location skip a command on cycle thus the need for a alternating relay. In essence each location has a wireless controller that all receive the command on. The issue is how can I make the sites come on in this sequence. 1&2 2&3 1&3

So you are controlling 3 motors off of one output and with a wireless command and I’m guessing you can’t change the logic on your RFU. It can be done with external relays and possibly a timer but I have to see if I can come up with a wiring diagram for you

 

[Megawatt]

I have 3 locations that have a relay controlling a pump, each site is several miles from each other and when my SCADA system calls for RUN all three relays energize at the same time. What I need is a local control that allows only 2 pumps to run at the same time but they need to alternate, (example) 1&2 when called then 1&3 on next call then 2&3 then back to beginning. Each site has a 12vdc relay interrupting the Auto of a selector switch, I was thinking of alternating relays for the control circuit but would like help in a wiring diagram showing this solution.

What size pumps and voltage are we talking about. Is these 3 phase motors?

 

[Lucien Nunes]

Two out of three pumps running simultaneously means that each pump has to miss every third start. The sequence has to be 'launched' with each pump's counter at a different point in the cycle and one has to rely on them always receiving the start commands to avoid them getting out of step. If one counter misses a start, one, two and then three pumps will start at each successive command until the cycle is corrected manually.

Thought: Does the pump duty rota have to change every start or can it be time-controlled, so that each pump misses every third day or hour? Does it matter if there is occasionally some overlap, e.g. if a pump is already running at duty changeover time? How frequent are the starts? Is the SCADA output momentary or is it active all the time there is demand?

If the sequence needs to advance at every start, then yes it can be done with a couple of relays or electronic counters or all sorts of different ways.

 

[Megawatt]

Two out of three pumps running simultaneously means that each pump has to miss every third start. The sequence has to be 'launched' with each pump's counter at a different point in the cycle and one has to rely on them always receiving the start commands to avoid them getting out of step. If one counter misses a start, one, two and then three pumps will start at each successive command until the cycle is corrected manually.

Thought: Does the pump duty rota have to change every start or can it be time-controlled, so that each pump misses every third day or hour? Does it matter if there is occasionally some overlap, e.g. if a pump is already running at duty changeover time? How frequent are the starts? Is the SCADA output momentary or is it active all the time there is demand?

If the sequence needs to advance at every start, then yes it can be done with a couple of relays or electronic counters or all sorts of different ways.

Thanks for your help Lucien ?