Well pump wiring diagnosis & repair:
this article describes troubleshooting a submersible well pump that was causing tripped circuit breakers and that pumped water only at a slow, reduced rate and pressure.
Ultimately using some simple electrical tests the homeowner traced the water pump problems to a nicked well pump wiring circuit wire.
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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.
For readers who are qualified and know how to use electrical test instruments, for safety and completeness also see
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.
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.
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
|Diagnostic Procedure||Repair Procedure|
|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|
|See ELECTRIC MOTOR OVERLOAD RESET SWITCH for how to find and reset this button|
|Bad line voltage||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.||
See INTERMITTENT CYCLING WATER PUMPS if the pump runs at odd times for no apparent reason.
See WATER PUMP SHORT CYCLING CAUSES if the pump is turning on and off too frequently.
|If the Well Pump Motor Keeps Running & Won't Stop||If the pump won't turn off the cause may be a damaged pump control, a plumbing or fixture leak, or a well problem.||
Watch out: If the pump motor won't shut off you should turn off electrical power to the pump to avoid damaging it, then diagnose the problem.
Some of the well pump troubleshooting suggestions in this list can be found at the Betta-Flo Jet Pump Installation Manual from the National Pump Co. Page top illustration courtesy of Carson Dunlop Associates.
Also see our other diagnostic guides for water pumps, wells, motors, in table form:
(Feb 2, 2014) tinner65 said:
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.
Continue reading at WATER PUMP ELECTRICAL SWITCHES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES.
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(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.
(Oct 21, 2014) bryab said:
Should I dig up the holding tank ?
Bry - I'm baffled by the question.
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