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.

 

[readydave8]

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.

Around 84 psi?

 

[kwired]

Around 84 psi?

Google said 86.6 for 200, but yes one should be able to add that to what is desired at the far and and use that for the setting if measuring near the pump. Pressure drop because of flow can likely complicate this method though, might still be able to be done, just not sure how to calculate it.

 

[readydave8]

Google said 86.6 for 200

I was close, multiplied by .42 (assumed that if 42 is the answer, .42 would be at least 1% correct)

 

[tom baker]

Where is the pressure being measured. At the bottom of the tank or pump?

 

[ptonsparky]

Or bottom of hill?

 

[Electromatic]

Currently, the pressure is being measured at the bottom of the hill where the pumps are via a PT plumbed in to the piping. Because of the distance, change of elevation, and the nature of the bladder tank, this doesn't work very well, and the drives don't really respond to what's happening in the tank. We are going to install a whole new tank 'station' with a larger tank and will want to control the drives/PLC straight from the pressure/level of the new tank.
I've told our water/sewer engineer to plan on burying 1 or 2 HDPE conduits between the pump site and the tank site with at least 1 pull box between them. My numbers show we could do a 4-20mA signal at that distance with #14 or maybe #16 STP. I told the engineer that fiber would definitely future-proof things even more. I don't know if that will happen, but it's why I suggested a second, spare conduit.

 

[hillbilly1]

Currently, the pressure is being measured at the bottom of the hill where the pumps are via a PT plumbed in to the piping. Because of the distance, change of elevation, and the nature of the bladder tank, this doesn't work very well, and the drives don't really respond to what's happening in the tank. We are going to install a whole new tank 'station' with a larger tank and will want to control the drives/PLC straight from the pressure/level of the new tank.
I've told our water/sewer engineer to plan on burying 1 or 2 HDPE conduits between the pump site and the tank site with at least 1 pull box between them. My numbers show we could do a 4-20mA signal at that distance with #14 or maybe #16 STP. I told the engineer that fiber would definitely future-proof things even more. I don't know if that will happen, but it's why I suggested a second, spare conduit.

On one water tower I worked on, they did not use a bladder tank, they used mercury pressure switches, but that was used for tower water level control, so I don’t think it would be good for a booster pump.

 

[SceneryDriver]

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.

I strongly second this. Run multi-strand fiber. You can use it for whatever you want to now and in the future. For less than the cost of a pair of those signal converters, you can drop a small PLC at the remote site and do local conversion from your pressure transducer(s) to fiber Ethernet to send back down the hill.

I believe you said the remote end is getting independent power, so you shouldn't need anything else.

If you have no remote power, run a pair of 10awg conductors, plus a ground wire with the fiber. If your remote loads are really light, you can probably send 208V single phase to power a small power supply. If you have slightly more power needs, you might consider a step up / step-down transformer arrangement and sent 600V to the remote site.

With the cost of copper, the fiber and associated protocol converters might very well be cheaper than shielded twisted pair cable at that distance. Polyethylene conduit is ideal for this application. You can likely get the fiber (and copper conductors if needed) already in the conduit on a continuous spool, and trench it in.

Dura-Line Cable-in-Conduit (HDPE CIC)

Save time and labor with cable in conduit. Power and communications cables already installed inside HDPE conduit mean no wire pulling needed.

shop.chapmanelectric.com

SceneryDriver

 

[hillbilly1]

No need for a TVSS with fiber is a plus too. Pre terminated is available too for an easy install.

 

[ptonsparky]

for Cable in Conduit

 

[herding_cats]

Wireless signal. I use the Pelican Wireless system. DM me for more info and what controllers to use.