Long distance pump control

[kwired]

I always thought 4-20ma was best in long run scenarios due to the fact voltage drop is not that big of deal and can be overcame easily and loop current change due to distance/resistance can be fixed with programming to an extent?

Probably is better as a general rule as a controller sending current signal is maintaining a specific current for whatever conditions it is responding to to so that whatever it is interfacing with sees what was intended. I would guess there is still some maximum as to how far this will work, though it may be more dependent on individual devices capabilities more so than a general rule across all 4-20 mA signals. Increased conductor size you would think would also work as compensation if there is issues with this.

A device that is outputting say a 0-10 volt signal will put out it's signal, but the longer the run is the more risk there is for some voltage drop that will give undesired input to the receiving device, to compensate the sending device would need to know what the circuit resistance is and have an ability to account for that. Three wire RTD temperature probes do this, the third wire is parallel to one of the other two. The measuring device measures the resistance of those parallel conductors and uses it to compensate the reading it receives across the RTD and therefore there is no manual calibration necessary for varying cable lengths or for differences in ambient temperature of the cable.

 

[Electromatic]

The pumps are on VFDs which are controlled by a small PLC (Micrologix1000 I think). The PLC gives a speed reference to the drives from a local pressure sensor. The problem with this current setup is that the local pressure doesn't accurately reflect what's going on at the bladder tank which is ~2,000ft away and ~200ft higher.
I think I'm going to recommend a pressure transducer and a 4-20 loop.
To somewhat future-proof things, I'm thinking of #14 STP--probably 4 pair. I'm further thinking that we contract to bury HDPE for the cable. Any things to look out for with that stuff?

 

[ptonsparky]

The pumps are on VFDs which are controlled by a small PLC (Micrologix1000 I think). The PLC gives a speed reference to the drives from a local pressure sensor. The problem with this current setup is that the local pressure doesn't accurately reflect what's going on at the bladder tank which is ~2,000ft away and ~200ft higher.
...

Including these small details in your OP or even the second might have changed some responses.

Radio is a good option. There are companies that specialize in it.

 

[tortuga]

To somewhat future-proof things, I'm thinking of #14 STP--probably 4 pair. I'm further thinking that we contract to bury HDPE for the cable. Any things to look out for with that stuff?

about 2,000ft from the pumps.

If your ruling out wireless/radio, I'd suggest running fiber between the sites, and use two simple 4~20mA signal converters for now, or leverage the MicroLogix 1000's other capabilities such as DF1 Full-Duplex Protocol.
I'd run standard 6-pair (12 core) ITU-T G.652.D OSP Armored Fiber Optic Cable, 2000' is probably right at a spool, your future self will thank you.

 

[Electromatic]

My OP was pretty much the basic description I was given for what needed to be done. The existence of VFDs, PLC, etc. was after my site visit.

I haven't ruled out radio, but the water/sewer engineer said he didn't like it, and I am a little skeptical for this application. The two sites are across a forested mountainside with about a 200' elevation change between them--absolutely no line of sight. I did look at Ubiquiti briefly as I think it's been mentioned on the forum before. I couldn't quite get a good sense of the exact gear needed. If there's a better source for radio equipment and layout, let me know.
Thanks as always

 

[tortuga]

My OP was pretty much the basic description I was given for what needed to be done. The existence of VFDs, PLC, etc. was after my site visit.

I haven't ruled out radio, but the water/sewer engineer said he didn't like it, and I am a little skeptical for this application. The two sites are across a forested mountainside with about a 200' elevation change between them--absolutely no line of sight. I did look at Ubiquiti briefly as I think it's been mentioned on the forum before. I couldn't quite get a good sense of the exact gear needed. If there's a better source for radio equipment and layout, let me know.
Thanks as always

The publicly owned utility here created a spec for fiber in the 1980's-1990's, a multi pair cable, as roads were dug up a spare duct was laid for the fiber, by the end of the 90's about 70 miles was installed linking about 25 substations and various other sites, originally most of the 96 pairs were used for various serial / sensor data now it all uses just one pair. People were skeptical of the cost but now looking back it was the best investment they ever made now they rent out spare pairs on the fiber.

 

[kwired]

The pumps are on VFDs which are controlled by a small PLC (Micrologix1000 I think). The PLC gives a speed reference to the drives from a local pressure sensor. The problem with this current setup is that the local pressure doesn't accurately reflect what's going on at the bladder tank which is ~2,000ft away and ~200ft higher.
I think I'm going to recommend a pressure transducer and a 4-20 loop.
To somewhat future-proof things, I'm thinking of #14 STP--probably 4 pair. I'm further thinking that we contract to bury HDPE for the cable. Any things to look out for with that stuff?

Guessing there still will be some delayed response if the transducer is 2000 feet away from the pump it is controlling. PID control and correct tuning could maybe work though.

Did you already compensate settings as is because of the elevation change? pressure should be higher at the low end by whatever 200 feet of water column amounts to.