Water Pump Wiring Troubleshooting & Repair
How to detect & fix damaged well pump wiring circuits
WATER PUMP WIRING DAMAGE - CONTENTS: how to check voltage, current, resistance to help diagnose well pump problems such as tripping breakers, blown fuses, weak pump performance or no water delivery from a well water pump
POST a QUESTION or READ FAQs about checking electrical wiring to diagnose well pump problems such as tripping breakers, blown fuses, weak pump performance or no water delivery from a well water pump
Electrical Wiring Damage Causing Water Pump Malfunctions: breaker or fuse trip/blow, poor or weak pump performance
4/12/2014 Reader Comments on diagnosing weird well pump behavior:
My home well is doing some weird stuff. First of all, I have 25 amp breakers going to my 1.5 HP pump that is 160 feet down. in the last few days, it has tripped the breakers 5 times. I ohm ed out the motor and it is open (infinite resistance) to ground both legs and 3.2 ohms between the 2 leads going to the motor.
[Click to enlarge any image]
The symptoms that I am seeing is that it it taking my well about 7 to 10 minutes to fill up ( I have a 120 gallon galvanized tank with no bladder). When the water pressure in the tank gets to about 30 psi, the water in the house starts discharging air and water combined.
I have changed the starter cap. because the pump sounds as if it is working extra hard at start up, but smooth out as the pressure increases. changing the caps did not help. I was thinking that the caps may be bad and it was pulling too much current at start up and tripping the breakers. I'm not sure if the system is water logged or not. Any ideas?
Joe, Tripping breakers on the pump circuit often mean that the pump is drawing high current [or that there is an actual short circuit].
If we don't have a short in the circuit then unfortunately that makes us suspect a failing pump motor. Keep in mind that motor tests are tricky because once parts start spinning an internal winding can move, changing the electrical properties of the device.
If it might help you, take a look at our electric motor diagnostics at
I'm speaking beyond my competence but from what I've been studying just recently, there are useful relationships between motor current draw and other conditions besides a failing motor.
Illustration at above-left: orange extension cord wiring used to hook up the pump pressure control switch is an improper and unsafe electrical installation.
Abnormally-low pump circuit current draw: a water pump that is running in a dry well will draw lower than normal current.
Abnormally-high pump circuit draw: a pump running against unusual resistance (blocked outlet) may draw higher than normal current, as would a pump with a binding impeller or rotor or a bad bearing. If you could see the pump operating (which you can't under water very easily) you might see an abnormal temperature rise too.
Abnormal resistance on pump circuit wires (with POWER OFF so we don't get fried) an indicate a shorted or grounded wire (zero or abnormally low resistance) or an open circuit (broken wire, high or infinite resistance)
So we could argue that a pump running against a waterlogged pressure tank might see higher than normal pressure but I doubt it. A water logged pressure tank will quickly if not immediately reach cut-out pressure and turn off the pump (unless the pressure control switch is itself faulty and not sensing that the tank is up to pressure). Anyway it's easy enough to check for a waterlogged tank, as we discuss in this article series.
I think I'd pull the pump and check for binding bearings, damaged impeller that's binding, and if those looked good I might take it to an electric motor repair shop for more expert testing.
Reader follow-up: successful well pump diagnosis traced to damaged wiring
I've got this thing working. I went to go on vacation the last couple of days but had issues so I had to come home.
Image at left, not from Joe's home, illustrates un-protected 240V wiring entering the well casing at the casing top of a water well located in a building basement.
I spent all day with it, watching it, listening to it. Here is what I found:
I was showing 238V at the cut off box at the control box. when the pump kicked on, I was loosing one leg and this was tripping the double pole breaker
. I tested this theory (I actually seen the leg go off with the meter) by taking my generator and hooking the 230V side up to the pump. I have a 7000 watt generator, so there was no issue running the pump. It took about 5 minutes to fill the 120 gallon tank.
It took forever [for the water tank pressure] to get past 25 psi, but once it hit 30 psi it took about 2 minutes for it to reach the cut off pressure of 68 psi (my pump and tank are quite a ways from my house and I adjusted the pressure). I had my wife and kids take showers, run the washing machine, and even used the sprinkler in the yard for a couple of hours and watched the pressure gauge and everything worked as normal.
With that being said, my power wire from the breaker box to the well is buried underground. I dug it up today and found a burned spot in the insulation. I cut the insulation back and found that the leg I was loosing when the pump came on was damaged.
I guess there was a nick in the wire when I buried it and didn't notice it. When the pump was not running, there was no current being pulled even though the voltage was still there. when current started passing through the wire, there was enough missing insulation to trip the breaker - like a ground fault on a 480V system.
I am an industrial electrician and I'm very familiar with 480V-2300V systems. I wasn't sure in my original post if I was seeing an issue with the air pressure in the tank or something along those lines.
Final fix: repaired bad wire going to the pump control box.
Well Pump Wiring & Electrical Circuit Diagnostic Table
Pump Trouble Cause
Pump Won't Start
Blown fuse, tripped breaker
Replace fuse or breaker - does the pump run and keep running normally?
Be sure proper breaker or fuse size in ampacity is installed
Low voltage to the pump
Check with VOM at the pressure control switch or at the pump wiring
Be sure the proper size of wire is used for the ampacity and length of circuit; Test for low voltage to the building.
Loose or broken pump wire
Check wiring against the pump installation manual diagram, check all connections for tightness, shorts, burns, damage
A loose wire can cause intermittent pump or other electrical device failiures as well as a hard failure that means no power or blown fuses.
Rewire or repair or replace wiring
Burned out pump motor
Check that the pump pressure control switch is trying to turn on the pump and that there is voltage at the pump wiring
Repair or replace the pump motor
Bad pump pressure control switch
Check the switch contacts for burning or wear
Adjust or replace the pressure control switch. Temporary emergency repair by cleaning the switch contacts may be possible.
Bad pump pressure control switch
Check the tubing connecting the pressure switch to the pump housing for clogging
Clean or replace the tubing and be sure the connections are not leaky - an air leak will prevent the switch from sensing pressure properly
Bad pump impeller or impeller seal leak
Turn off electric power to pump, see if you can move the impeller or motor - if it won't turn it is jammed or damaged
A bad impeller can jam the pump, causing it to draw high current.
Remove obstruction in impeller housing, inspect for and replace damaged impeller or frozen motor.
Bad pump motor starting capacitor
Use a VOM in ohms setting to check resistance across the capacitor. If the meter does not move (no current flows) the capacitor is "open". If there is zero resistance the capacitor is shorted.
Replace the starting capacitor
Pump motor shorted out, jammed, burned up
Fuse blows or breaker trips as soon as the pump tries to turn on. If the external wiring is ok (no short circuits) the motor is shorted internally
Replace the pump motor
Things to Check if the Pump Motor Starts but Overheats and Trips its Reset Button
Use a VOM to check the voltage level at the pressure control switch
If voltage is too low, check voltage at the electrical panel and check that the proper size wiring was used for the ampacity and length of run and that there are no partial shorts or damaged wires or connectors
Incorrect motor wiring
Check the actual electrical wiring against the motor wiring diagram or the installation manual for the equipment
Reconnect wiring properly
Motor is too hot due to surroundings - inadequate ventilation
Check the air temperature where the motor is located. If the air temperature is over 100 degF, the pump may be too hot and its thermal overload switch tripping because of the environment, not a pump problem.
Install adequate ventilation, or if needed, shading, or relocate the motor/equipment to a cool location
Pump operates too long at low water pressure
If the well recovery rate is too poor and the pump is operating at low water pressure, possibly because a tailpiece is installed to prevent air injection and pump burn up, the pump may be overheating.
Install a valve on the water discharge line and reduce water flow to increase water pressure inside the pump itself.
What to do if the well pump runs continuously or runs too often
If the Well Pump Motor Runs Too Often
If the pump runs too often the cause may be a control problem, water tank problem, piping problem, or a well problem.
my deep well pump has a concentric pipe running from the well to the pump. is the outer pipe just a sleeve for the inner pipe, or is there another reason for it?
Tinner, some installers run a larger diameter pipe to make it easier to replace a supply pipe or wiring in the future. The new lines can be snaked through the larger diameter plastic line. But I can't know for sure what you've got with no other description than your note. Take a look at the fittings, wiring, and water piping involved.
(May 8, 2014) james said:
what is the problem if on/off switch wont function?
James :if you mean the pump won't turn off, in the More Reading links just above see the article titled WATER PUMP WONT STOP RUNNING
Look for an open wire, shorted wires, or if your problem is a wall switch, replace it.
Question: dig up the holding tank?
(Oct 21, 2014) bryab said:
Should I dig up the holding tank ?
Bry - I'm baffled by the question.
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Class 9013 Square D Commercial Pressure Switches: Water Pump Pressure Control Switch Class 9013, Type F, G, Manual, Square D Company, 8001 Highway 64 East, Knightdale, NC 27545-9023, USA, (919) 266-3671, www.squared.com,
web search 02/24/2011, original source: stevenengineering.com/tech_support/PDFs/45COM.pdf. Quoting:
The Type FSG, FYG, FRG - PUMPTROL® Water Pump Pressure Switches are used to control Water Pump Pressure Switches are used to control
electrically driven water pumps and have the following features:
The Type FSG is the standard water pump switch, suitable for all types of pumps: jets, submersible,
The Type FYG is designed to meet higher horsepower and pressure requirements.
The Type FRG is reverse acting: the contacts open on falling pressure.
All are diaphragm actuated.
The Type G - PUMPTROL® Commercial/Light Industrial Pressure Switch is used to control electrically
driven water pumps and air compressors. It has higher electrical ratings for direct control of motors in
pump and compressor applications. The Type G switch is diaphragm actuated and has contacts that
open on rising pressure.
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