Mike Dolt Enterprises
Mike Dolt Enterprises
User: Seven-Delta-FortyOne, Location: Humboldt
Asked on: Monday, August 4, 2025 at 2:35 pm EDT
Answered on: Monday, August 4, 2025 at 2:35 pm EDT
Question: Scenario: 1 phase 230V well pump, separate pressure pump in system, so well pump only pumps to storage tanks.HO called me because they feel the well pump hasn’t been coming on much. It is very typical for this well to run dry anywhere from mid summer to late fall.System is as follows: 20A 2P breaker - low water/overload control box - box with contractor for float switch - motor starter with start capacitor.As far as my opinion, it’s working as it should. Controller is showing OL when float switch calls for water.What I did: Jumpered float switch; controller shows OL.Bypassed low water shut down, jumpered float switch, nothing comes out of pump, but clamp meter shows 31-32 amps going to well pump, load side of motor start controller.Tested capacitor, tested good.Pulled motor leads from controller. Tested Ohms. Got 15-16 ohms on run windings. Manual says 3.5-5.6.Meggered motor leads. Got 220M ohms on both leads.Two areas of concern for me: In the interest of being thorough, I don’t have any way to absolutely verify that the pump in going into OL because of no water, or because of a possible problem with the impeller, clogged screens, etc., without pulling the pump. Unless there is something else I can do.And 2, what would be the cause of having a slightly higher Ohm reading? I know what an infinity would mean, but what about when it’s just a little higher than it should be?Pump was replaced about 6 years ago, so shouldn’t be worn out ideally.
Okay, let's break down this troubleshooting process and address your concerns
Understanding the System
You have a well pump filling storage tanks, controlled by a float switch. A low-water cutoff protects the pump from running dry. The system uses a motor starter with a start capacitor.
Your Troubleshooting So Far Observation
The pump isn't running as often as the homeowner expects.
Controller Showing OL
When the float switch calls for water, the controller indicates an overload (OL).
Jumpered Float Switch = OL
Jumpering the float switch also results in an overload. This isolates the float switch circuit and suggests the issue is elsewhere.
Bypassed Low Water + Jumpered Float = 31-32 Amps, No Water
This is key! The pump is drawing significant current without producing water.
Capacitor Tested Good
Eliminates the capacitor as a simple cause.
Run Windings = High Resistance (15-16 ohms vs. 3.5-5.6 ohms)
This is a significant red flag.
Megger Test = Good Insulation (220M ohms)
The insulation between the windings and the motor case is good (not shorted to ground).
Analyzing the Findings1. High Current, No Water, High Resistance on Run Windings = Locked Rotor/Stalled Motor The combination of these symptoms strongly points to a locked rotor or a stalled motor. Here's why: High Current
The motor is trying to start, but it's unable to turn freely. This causes a very high inrush current (much higher than the normal running current).
No Water Output
The pump isn't turning, so it can't deliver water.
High Resistance
The run windings' resistance being significantly higher than the specified range is a telltale sign of winding damage (partial short, arcing, or excessive heat).2.
Root Causes of a Stalled Motor Mechanical Binding
This is the most likely culprit:
Impeller Obstruction
A rock, debris, or severe scale buildup in the impeller.
Seized Bearing
The motor's bearings might be corroded, damaged, or lacking lubrication, preventing free rotation.
Damaged Impeller
A broken or severely damaged impeller could be jamming the pump.
Electrical Problems
Less likely, given your megger test results, but still possible:
Winding Faults
Even though the megger test showed good insulation to ground, there could be an internal short circuit within the windings that causes uneven magnetic fields and prevents the motor from turning properly. This could also be what's causing the high resistance reading.
Open Winding
A break in one of the windings could increase the overall resistance and prevent the motor from starting.3.
Why the Overload (OL) Trip? The overload protection in the controller is designed to trip when the motor draws excessive current for too long. A stalled motor will draw a very high current continuously, quickly causing the overload to trip.
Addressing Your Specific Concerns How to Verify No Water vs. Impeller/Clogged Issue Without Pulling the Pump
There isn't a definitive way to guarantee the specific cause without pulling the pump. However, the electrical readings strongly suggest a mechanical issue. Consider a Borescope/Inspection Camera
If possible, try to insert a small inspection camera down the well to visually check for obstructions or damage to the pump intake/impeller area. This is a long shot, but worth considering.
Listen Carefully
When you apply power to the pump (bypassing the low water shutdown and float switch), listen very closely for any abnormal sounds coming from the well. A grinding, scraping, or loud humming sound can indicate mechanical binding. Be very careful and only power it on briefly. Continued operation with a locked rotor can cause the motor to overheat and fail catastrophically.
Measure Voltage at the Motor
Confirm that the motor is receiving the correct voltage. Low voltage can contribute to high current draw and a stalled motor.
Cause of Higher Ohm Reading
The higher resistance reading on the run windings is a sign of winding damage. It's not as straightforward as an open winding (which would be infinite resistance). Instead, it suggests:
Partial Shorted Windings
Some of the wire insulation within the winding could be compromised, causing some of the turns to short together. This reduces the effective length of the winding and increases its resistance.
Heat Damage
Overheating (perhaps from running dry in the past) can damage the wire insulation and alter the winding's characteristics.
Next Steps and Recommendations1. Strong Recommendation: Pull the Pump. Given the symptoms, especially the high current, no water, and high run winding resistance, pulling the pump for inspection is the most logical next step. You are past the point where you can reliably diagnose the problem without visual inspection.2. Inspect the Pump Thoroughly
Check for Mechanical Binding
Rotate the impeller by hand. It should turn freely. If it's stiff or seized, investigate further.
Look for Obstructions
Carefully examine the impeller, intake screen, and volute for rocks, debris, or scale buildup.
Inspect the Impeller
Look for cracks, breaks, or excessive wear on the impeller blades.
Check the Bearings
Inspect the motor bearings for wear, corrosion, or lack of lubrication.3.
Consider Replacing the Motor (or Entire Pump)
Since the run windings are showing a higher-than-specified resistance, the motor is likely damaged. Repairing the motor (rewinding) is often not cost-effective. If the pump is 6 years old, consider replacing the entire pump assembly. It might be more economical in the long run.4.
Once the Pump is Repaired/Replaced
Flush the Well
After reinstalling the pump, flush the well thoroughly to remove any debris that might have been dislodged during the pump removal.
Check the Low-Water Cutoff
Ensure the low-water cutoff is functioning correctly.
Monitor the System
Keep an eye on the system's performance after the repair to ensure the problem is resolved.
Important Safety Considerations
Disconnect Power
Always disconnect power to the system before working on any electrical components.
Lockout/Tagout
Use proper lockout/tagout procedures to prevent accidental re-energization of the circuit.*
Confined Space Entry: Working in a well can be a confined space. Follow all relevant safety regulations for confined space entry.By following these steps, you should be able to accurately diagnose and resolve the problem with the well pump system. Good luck! Flag for review