Single Phase Submersible Motor Repeated Burning

The smart money is on <...Might be motor starter is connected to two phase in place of P & N at ELCB...>.

The title says "single phase" yet you have a 3 phase ELCB incoming? Yes if the phase to phase voltage is being used, a higher current will be the result.

Make sure the applied voltage is the same as the rated voltage. This would give you trouble at any HP which seems to be the case. The common failure must come from a common source (i.e. power source). Don't assume it is correct. Measure the applied voltage.

Is there a back pressure?

You are either applying the electrical power to these motors incorrectly (a short is present somewhere, or a highly resistive lead, results in motor attempting to run on lower voltage, and it burns out) OR whatever the motor is coupled to is not spinning freely and is a mechanical resistor that is above the power output of the motor.

You're asking us to troubleshoot with little information. What's the applied voltage? What is the voltage measured from the ELCB? Why is it not dedicated for the well pump? Could one of the other devices (the lift, UPS & lighting) be causing a voltage drop? The pump is being switched on and off with a pressure switch. Is the pressure switch making and breaking line voltage? If so, is there a voltage drop across the pressure switch? If pressure switch is switching a control circuit for a motor starter, what is the output voltage from it? Does the output voltage match the name plate rating of the pump?

If there is a malfunctioning float switch involved here, it is possible that the pump might continue to run after the liquid level has fallen too low to keep it cooled.

So what brand of pumps are these that don't have a built in thermal protection device to prevent total winding burndown from happening to begin with?

"So what brand of pumps are these that don't have a built in thermal protection device to prevent total winding burndown from happening to begin with?"

It's a valid point, but here's what I've seen happen, on more occasions than I like to think. The Potential Relay fails, the pump never goes into "run" mode and over heats, the thermal cut-outs kick in and shut it down, but the pressure / float switch calling for the pump is not satisfied, so it stays in a state calling for the pump. The thermal cutout cools quickly (because the pump is in cool water), resets, the pump restarts, the cycle repeats, over and over and over in as rapid a succession as the thermal switch cooling time constant allows. all of this is taking place deep under ground, nobody knows it's happening. Each cycle does incremental damage to the motor winding insulation and eventually it fails.

Possible, but unlikely given those types of motors are purpose built to work in suich and environment it would seem plausible that the manufacturers would have taken that into account.

It's not like they are repurposed above ground normally air cooled motors.

I know how to pull a deep well submersible pumps with basic equipment and have been called in to help pull at least a dozen now due to pump issues of which the only burned out motors I have ever came across were due to known lighting strikes having taken them out. The rest were silted in and locked up or simply worn out impeller stack related problems.

Of which my own is now on that list to be pulled again for being silted in up to the intake this time so if ran for more than 20 - 30 minutes the motor overheats and shuts down for about 5 minutes. Been that way for over a year now. ~ 180 feet down on 1" line is a hard pull to do by myself so I have been putting it off.

Seems like down-hole well technology could stand to be improved upon, but the silt has to go somewhere. You (and everyone else) needs a pump that can handle the silt without allowing any of it to accumulate at the pump, or elsewhere in the casing, well tubing, etc.

I think this must be the Achilles heel of submersible multi-stage well pumps, based upon the very mature centrifugal turbine design.

Has anyone ever really investigated pumping with a truly axial flow well turbine?

What about a boundary flow turbine (disc, or Tesla) Turbine? I have seen some Tesla turbine pumps used in utility type plants for condensate transfer, and they do apparently have sufficient durability. Remains to be seen in a well bore, where one particle the wrong size could really mess up the flow pattern between adjacent discs.

I suppose in designing such a disc pump, the well screen (hopefully at the bottom of casing) should be just smaller than the largest silt (sand) particle that does not stick between adjacent discs. In such a case, the silt should transport cleanly along with the water, and properly be separated at the surface. Not sure about any silt that is still entrained with flow when the well temporarily shuts down at the end of a cycle.

The biggest problem I have seen in the pumps I have already collected over the last 10 or so years, since I figured out how to pull a deep well pump, is the overall quality changes that have taken place and not for the better.

The oldest pump I have in my collection was the original unit that came out a well drilled sometime around 1970 putting the pump at ~ 45 years old when I pulled it. It still works fine actually! The guy who had me pull it thought it had shorted out and bought a new one plus new cable before I arrived and it turned out that just the cable was bad but being I had everything out he had all the new stuff go in back in.

Anyway, That pump was all heavy stainless steel with steel impellers whereas the new pump despite being the same Goulds brand, HP rating and flow curve specs weighed about 15#'s less. The motor was smaller in diameter and the impeller stack was all plastic just like the cheap foreign brand units found at the local homebuilding centers for half the price this guy paid for his.

Still cost the guy something like $600 for the pump and $100 or so for the wire or thereabouts, which I thought was high given how it was made, but being I agreed to help pull his pump on a trade for stuff deal VS the local well driller wanting something on the high side off $2000 to do the job he really didn't mind!

Kind of thinking I might use it to suck the slit out of my well casing being its all metal impeller stack, despite being some 45+ years old, is not worn to any bad degree so it should handle sucking the silt out of the bottom 20 feet of my 6" well casing without damage that I would be more concerned about with my all plastic pump that in the well now. And even fit does chew it up it's a free pump anyway!

For me this are too many open questions and reasons possible. Call a specialist or service man from the pump manufacturer as all answers from the forum are only speculations... I would also consider overload of the pump as apossibility.