Craigpump
In the Trades
You're pumping the well dry, all the new wire in the world won't fix that.
You're pumping the well dry, all the new wire in the world won't fix that.
Scott, Valveman and Craigpump,
I really do not know how submersible pumps are configured, so I may be totally off base with my assumptions. I am trying to explain Scotts measurement of 7.7 amps and 4.5 amps. Why the difference may exist.
But, if it were like my shallow well pump motor, it would have an internal centrifugal switch and at least one capacitor, a START cap. It may also have a second capacitor, a RUN cap.
When the pump first turned on, the power would be applied to the START capacitor and the motor windings. During the initial startup the motor RPMs are low and the contacts of the centrifugal switch would be pulled closed by a set of springs. These contacts connect the START cap which allows a high inrush current to provide high starting current and torque.
As the motor RPMs increase, the contacts of the switch would be thrown outwards by the centrifugal forces until they overcome the strength of the springs and the set of contacts open which disconnects the START cap. Now the motor does not require the extra current or torque from the START cap because it is up to near full speed.
If there is a RUN cap, then the switch would make a second set of contacts to engage that cap. Otherwise, it would just be the motor windings alone, with no cap at all. In this condition, the motor whirs along at full RPM and a much lower current. Once it has the water pumping and the inertia of the motor's rotor going along, it doesn't need much assistance to keep on turning at this speed.
Therefore, when it initially starts up, there should be a higher current measurement. Once it is up to full speed, the current should drop back substantially.
So, when you measure the start up current at 7.7 amps and then it drops down to 4.5 amps, this is actually a normal and desired operation for an external, above ground pump motor like mine. I am not sure if a SUBMERSIBLE pump motor is set up this way, although I can't speculate how it would work if it were not.
Now, if there were a wiring problem (high resistance due to numerous broken conductors), there may be a LOW VOLTAGE condition at the pump motor. If this were the case, then the motor would turn slower, maybe so slow that it could never build up enough speed to activate the centrifugal switch and hence the current would always measure high (7.7 amps) because the START cap is always in the circuit.
My problem now with my theory of the broken conductors in a multi-conductor cable is that the 7.7 amp start up current sure sounds about right to me. If there were enough broken conductors to affect the motor RPMs, I would expect the current to be lower. So I am now unsure of the diagnosis. Something is not adding up here, and it sounds like Scott is pretty sure of the water level in the well.
Do submersible pumps have centrifugal switches? I can understand that they must be constructed with extreme attention to size and weight. I have used pumps that do not have such switches, but they usually are not very robust and do not pump a great deal of volume or pressure.
RADAR
There is no controller. OP has "2-wire" pump.However, we are assuming that the controller output is stable
There is no controller. OP has "2-wire" pump.
Your theory is that there is an intermittent resistive connection. I believe the experinced people are not saying that is impossible, but they are saying that there are more likely explanations.
OP's wife is probably saying that the water needs to work, and that should be a priority. A call to a well person if symptoms com back will probably be money well spent.
A submersible pump does not have a foot valve.
This is awkward, but...
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