Pump Feedback PLC

Newbie2016 · Oct 24, 2016

How can you confirm the pump started from a plc is running in the field without relying on the fact the contact has closed.

Would you say get feedback from the pump to close a limit switch connected to a digital input?

RonJohn · Oct 24, 2016

Generally speaking, you could use either a pressure switch or a flow switch installed downstream of the pump discharge.

keithkyll · Oct 24, 2016

Current sensing switch.

isiah_s · Oct 24, 2016

RonJohn said:
Generally speaking, you could use either a pressure switch or a flow switch installed downstream of the pump discharge.

One trick I saw with this is if you use a filter put a pressure switch on inlet and outlet of filter. Take differential. If there is a non-zero reading between the two your filter is clogged.

jraef · Oct 24, 2016

Use a solid state overload relay, VFD or Soft Starter that provides a current feedback signal, either serially via a comm port or with an analog signal. You need an OL no matter what, so just take the next step and make it smart. If current is flowing, the pump is running. You can even use threshold values to determine flow is taking place.

jkerekes · Oct 24, 2016

Zero speed switch.

boneless · Oct 25, 2016

If you want to make sure the pump is actually pumping, you will need flow or diff. pressure measurement. This can be a digital contact, usually fairly easy to install (depending on your piping, medium, pressure etc.)

If you are happy if the motor is running, check current, or speed pick up on motor.

Yes you could do this with frequency drive, but if you have no need to control speed, I personally think this might be overkill..

Tom Jenkins · Oct 25, 2016

Your choice depends to some extent on the fluid being pumped and the system being pumped into. If clean water something intrusive like a flow switch or a direct tapped pressure switch will do the job. If you are pumping sewage flow switches will soon show you how many rags the system moves, and pressure taps will need isolation diaphragms to avoid plugging. I personally like current monitoring.

redbarron55 · Oct 25, 2016

We use minimum current settings on smart overload.
Current too low not pumping.
You could put a CT in or a current sensing switch in as well and tell the same things.
We have Square D overloads that can be programmed to indicate a failure with too low motor load.

Pump Feedback PLC

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