Anyone use VFD designed cable in water wells?
Anyone use VFD designed cable in water wells?
(OP)
I have done the design work required for municipal drinking water wells for a about 30 years now. The trend, lately, is to use a VFD to power the well pump. I have always used steel conduit from the controller to the well head and the driller/installer has used individual wires down the well, connecting to the flying motor leads with waterproof connectors. These wires are secured, with some slack, to the drop pipe with Scotch #88 tape at about 15-foot intervals. The slack allows for some drop pipe lengthening. I also install a pressure transmitter just above the pump in order to determine the depth of water in the well, at least the depth of pump submergence. On very deep wells I have seen some VFD noise on the 4-20 mA signal of the pressure transmitter. The signal cable is installed alone in a steel conduit from the well-head to the controls. As this cable is only near to the VFD wiring in the well, I have to assume that that is the source.
So, has anyone used VFD designed cable inside a well? How would the deep end be sealed? Often the pump has 4-foot flying leads and is under 200-300 feet of water. Any comments or thoughts?
Thanks
Steve
So, has anyone used VFD designed cable inside a well? How would the deep end be sealed? Often the pump has 4-foot flying leads and is under 200-300 feet of water. Any comments or thoughts?
Thanks
Steve





RE: Anyone use VFD designed cable in water wells?
As a side note, please only use a VFD when it is necessary. I hate explaining to customers that their use of a VFD is why their motors that easily work for 10+ years direct-on-line are now failing much sooner (even just using a good filter can get the life span back where it belongs). Water filled motors are different than other motors, and those difference are a major pain once VFDs are added.
RE: Anyone use VFD designed cable in water wells?
Our hydro guy insists on ramping the flow up and down, on starting and stopping, for about 30 min, sometimes 60 min.. I usually set the VFD up to start and run at 30 Hz min, usually about 45 Hz , zero flow, and then ramp to the desired flow. I have found that a VFD is the best way to get this ramping of flow.
Steve
RE: Anyone use VFD designed cable in water wells?