How to Test a 3 Wire Submersible Well Pump

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In this guide, you’ll learn how to test a 3 wire submersible well pump step by step. 

It doesn’t matter if you know very little about plumbing or if it’s your first time to experience a technical problem with your 3 wire submersible well pump. This guide will give you the information you need to do the troubleshooting the right way. 

And let’s be honest: 

A strange noise from or near your well pump isn’t a small problem. It’s even worse if you’re experiencing an abnormal water pressure in your house. 

Of course, you could call a plumber over to diagnose and fix the problem, but that comes at a cost, which you may not have been prepared to cover. 

That’s why it’s important to learn how to do the testing yourself, so you can easily troubleshoot the well pump on your own in case you ever have an issue with it in the future. 

The Right Way to Test a 3 Wire Submersible Well Pump 

There are at least four steps to testing a 3 wire submersible well pump. This process will require an ohmmeter, so buy one if you don’t have it yet. You’ll need to check whether the ground wire is in line with the three wires. Then, you’ll use the manual that comes with the ohmmeter to determine the voltage and resistance requirements. If the test result between each wire matches what’s on the manual, your testing was successful. 

Step #1: Check the voltage of your well motor 

The first step to testing a 3 wire submersible well pump is to set the set voltage in the ohmmeter. To do this, check the recommended voltage of your well motor from the manual. The reading display on the ohmmeter should be exactly the same as what’s in the manual. 

Step #2: Turn off power to your well motor 

Because an ohmmeter only reads the resistance of devices that don’t have power flowing through them, you need to make sure that your well motor doesn’t have a currently active power supply. An attempt to test the well pump with the power on won’t cause electric shock per se, but it will cause the ohmmeter to malfunction and eventually get you incorrect readings. 

Step #3: Hooking the cords 

Here, you’ll have to hook one cord to a colored one and the other one to the ground. Because the electric codes standard varies from country to country, or where you purchased the well pump, you should check the user manual to know which cable should go to the ground. If you’re in the US, for example, the color code for the ground cable is green. 

If, during testing, the resistance between the ground cable and power lead reads OL (Open Lead), your motor is in good condition and therefore working well. 

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Step #4: Checking the Insulation Resistance 

The final step is to use a standard digital ohmmeter to determine the insulation resistance between lead and ground wires. You’ll need to check your well pump’s manual to know where to put the lead and the ground wires for testing. 

Don’t freak out if the insulation resistance reads above normal. That’s something to expect in the case where there’s a combination of giant cables stretching further feet. Again, you can check this information in your user manual.  

You can use the formula R = ρL/A to calculate the insulation resistance of your cable. Or you can use this wire resistance calculator to make your work easier.  

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How to Troubleshoot Your Well Pump  

Troubleshooting a well pump isn’t something you have to do often. If your water system is in good condition, you may never even have to bother with this. 

However, if you run into some issues such as constant clicking noise from the well, inconsistent water pressure, or abnormal power bills, you may need to check if your well’s motor is in good condition. 

Below are some troubleshooting tips that you can use: 

Replacing the well pump’s pressure switch

Look at the pressure switch closely for about 10 seconds. If you see some burnt section on it, try to clean the stain with a standard nail file. However, since this solution is only temporary and not any better than buying a new pressure switch, consider getting a replacement right away. 

Test the pressure switch by tapping the screwdriver handle. If it creates a spark and if the pump starts, it’s a sign that it’s time to replace the pressure switch.  

Check if the pump has power issues

If the well pump is turning off unexpectedly, there’s a high chance it has an issue. If the pump switch is in the off position, push it back on. Observe it for a few minutes to see how it behaves. If the pump happens to turn the switch back off, the pump could be faulty. 

Check the condition of your tank 

There’s a high chance that your tank, not the pressure switch, is the problem. Try shaking it to determine how it feels. If it’s too heavy, it’s likely the problem.  Again, if water pushes out of the air valve close to the top, probably the tank needs a replacement. 

Replacing the pump controller 

You did a 3-wire submersible well pump test to determine if your setup is working correctly. The expectation is that if you get matching readings, the motor is in good working condition. However, if the ohms reading you go for the insulation resistance are somewhat off, there’s a high chance that some components in the control box need to be replaced. It’s also possible that you may need to get a replacement for the pump controller. 

Keep in mind that there’s no easy way to know if the problem is the pump controller other than with some energy tests. 

The replacement won’t cost you a lot of money. You may end up spending around $100, which should be enough to contract a professional to help with the replacement of the pump controller. 

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