Long 2120' 4-20ma Control Cable - Options and Suppliers

[wwsmith]

My application has a VFD controlled pump located 2120 feet away from the building. I want to send a 4-20ma signal from the building to the VFD to control the pump speed and resultant water flow. I want a cable suitable for direct burial. No other cables will run alongside this cable (although maybe I should have some spare unused wire pairs since this is such a long run?).

What cable type and size is the best value for this run and what suppliers do you recommend? Looking over the web, I haven't found many suppliers advertising 2500' spools of suitable cable for this application, but maybe that is an option you have to call them about.

 

[Lancie1]

I suggest shielded 4/c #16 AWG. Get whatever max length is available (500', 1000'), and buy some waterproof underground cable splices. If you cannot find them anywhere else, waterproof splice kits are widely available for submersible water-well pump cables. An alternate (if you don't like underground splices) is to install some "handhole" boxes (buried boxes with cover exposed) and make the splices inside the handhole boxes.

Alpha Wire #M8706020 is a 2-pair (4/C) #16 AWG with shield, in a direct-burial jacket, available in 500' or 1000' rolls.

http://www.alphawire.com/en/Products/Cable/Manhattan-Electrical-Cables/Instrumentation/M8706020.aspx

Alpha also has the Xtra-Gard 3 Direct-Burial cables, but I don't think any of those cables have shields.
http://www.alphawire.com/en/Products/Cable/Xtra-Guard-Performance-Cable/Xtra-Guard-3.aspx

 

[Rixter78]

Your best bet is to go with a wireless system. That distance would be a problem and splicing a 4-20 loop requires special connectors.

 

[rdrast]

Your best bet is to go with a wireless system. That distance would be a problem and splicing a 4-20 loop requires special connectors.

The distance isn't so much of a problem.

Special connectors? Not at all. Where did you come up with that?

 

[wwsmith]

I suggest shielded 4/c #16 AWG. Get whatever max length is available (500', 1000'), and buy some waterproof underground cable splices. If you cannot find them anywhere else, waterproof splice kits are widely available for submersible water-well pump cables. An alternate (if you don't like underground splices) is to install some "handhole" boxes (buried boxes with cover exposed) and make the splices inside the handhole boxes.

Your best bet is to go with a wireless system. That distance would be a problem and splicing a 4-20 loop requires special connectors.

I don't have any problem doing splices for something like direct burial irrigation wire, but splicing a 4-20 loop sounds problematic and would definitely require special connectors to have a chance at being reliable. I have thought about wireless, but since I am trenching to this location anyway for the water pipe, I thought why not drop some cable in that same trench?

Does anyone know of a supplier of a 2500' spool of 4/c #16 or #18 AWG direct burial cable?

 

[Lancie1]

Yes, but it will cost you, and take awhile to get it. Go with two 1000' rolls and one 500' roll, add two spicle kits. You don't need anything special for the shield, just a water-proof splice.

Alpha Wire #M8706020 is a 2-pair (4/C) #16 AWG with shield, in a direct-burial jacket, available in 500' or 1000' rolls, OR THEY WILL MANUFACTURE WHATEVER LENGTH YOU WANT.

http://www.alphawire.com/en/Products.../M8706020.aspx

 

[wwsmith]

Yes, but it will cost you, and take awhile to get it. Go with two 1000' rolls and one 500' roll, add two splice kits. You don't need anything special for the shield, just a water-proof splice.

Alpha Wire #M8706020 is a 2-pair (4/C) #16 AWG with shield, in a direct-burial jacket, available in 500' or 1000' rolls, OR THEY WILL MANUFACTURE WHATEVER LENGTH YOU WANT.

http://www.alphawire.com/en/Products.../M8706020.aspx

Lancie, no doubt, what you describe above is the most expeditious and cost effective way to go. I just need to convince myself that I can make good splices and protect them sufficiently. Like you said before, junction boxes that would allow easy access to the splices would be helpful and allow quick repair if ever needed.

Only thing easier would be if a 2500' spool could be found "off the shelf" at a reasonable price. No doubt, special high price orders can be made, but 2500' is a common stock length for a lots of different cable types so maybe there is one out there already. I'll keep checking, but if I can't find such a spool, I will go the splice route as you suggest.

 

[bce123]

call elloitt electrical supply talk to bob nixon 979-779-6630

 

[wwsmith]

call elloitt electrical supply talk to bob nixon 979-779-6630

Hey BCE, thanks for that tip. I'll give Bob a call right now. His shop is just a few miles away from me. The only thing though about my local suppliers is that they can rarely give me as good of prices as I can find on the internet. A little bit of premium is ok with me, but not hundreds of dollars. But you never know, sometimes they can do nearly as well.

 

[Lancie1]

I just need to convince myself that I can make good splices and protect them sufficiently.

WW,
You don't have to be an expert to do this kind of waterproof splicing.

There are thousands of people in the US who use submersible well pumps. I have replaced 5 or 6 of these pumps for family and friends over the years. These pumps fail for many reasons - pump sucks in mud or gravel, casing corrodes and leaks, lightning runs down the wires, motor burns out, and so on. The pumps come with a stainless steel sealed motor housing, and 2 wires coming out of a sealed fitting. At first, when a pump would fail and someone would ask for help getting the old one out of the well, and a new one installed, I always looked at the splice between the factory wiring and the user wiring (which is completed submerged under 30 to 40 feet of water for years and years). I never have seen a pump fail because the waterproof splice failed.

Here is the way these are made. They take a heavy-duty clear plactic tube (sleeve) about 4 inches long, and 1/2" diameter (depending on wire size), and install rubber grommets (doughnuts) on the ends. These rubber doughnuts are not to keep out water, but serve two other functions. They help center the wire inside the tube, and hold in the epoxy filling until it hardens. You insert one wire into the tube, push it out the other end, make the splice using the supplied crimp terminal, then pull the splice back into the center of the plastic tube. Then you squeeze the epoxy into the tube, completely filling all the space until all the air is out of the tube, and there are no voids, and the spliced wire is centered in the tube. Then you let it harden for 5 or 10 minutes. I would bet money that the wire insulation will fail before this type of splice leaks.

A handy person could make their own splices like this - I am sure that is how they first were invented. All you need is a good heavy-wall transparent tube, some 2-part epoxy glue, and maybe some rubber or cork stoppers for the ends. You could just tape the ends up with electrician's tape. The epoxy is the seal, all else is for convenience to get the epoxy in place.

 

[Cow]

Lancie, have you ever tried adhesive lined heat shrink? I'd think it would be a great alternative for your epoxy and tube method in this instance. We use it all the time on DB aluminum feeders that fail and need to be spliced. I've tried cutting one apart after it had cooled down and that definitely made me a believer!

My personal opinion would be to source a 2500' reel though, I'm a big believer in NO unnecessary splices if at all possible on new construction. Late night repairs are a different story...

 

[OkiePC]

I agree with Lancie about the pump splices. I have only worked on a handful of them...never had a problem I also had no trouble installing them in my well a few years ago.

With that said, that distance will cause some voltage drop, so you may end up having to bump up the voltage supplied to the loop.

I also would use Banner Surecross or other wireless I/O for this. It will be so much cheaper and easier to deal with in the long run. We demo'd the surecross to add an alarm to our guard shack from the main plant. The demo unit with stock antenna worked fine through two brick walls to the shack about 150' away, and was updating very quickly, although it really isn't deterministic, we were told that about 50ms update times were typical.

 

[bce123]

My two cents i never use direct burriable cable always use conduit espically in the soil condutions in c.s texas. But yes splices work. Without knowing more about the app i can't say on this one wireless sounds good to me with the low cost of micro plcs and hmis there are lots of options out there

 

[Lancie1]

Lancie, have you ever tried adhesive lined heat shrink? I'd think it would be a great alternative for your epoxy and tube method in this instance.

Cow, I have seen it used, and it would be a good choice.

If a 2500' roll can be found, then by all means go that route. I have tried looking for long lengths in the past, with success at times, but most of the time having to settle for shorter lengths. I have wasted a lot of time looking for long lengths, so it is not an efficient way to get on with the job. The problem is that small direct-burial shielded signal cable is not often needed in such long runs. It would be luck to find a suitable piece. The phone companies use long runs, but their cable is not usually shielded, and now most long phone runs are being replaced with optical fiber.

Houston Wire and Cable might be a place to check for long rolls.

 

[bce123]

houston wire and cable might be a place to check for long rolls.

wholesale only i think? Fiber is cheap and a good option