How Do I Protect My Submersible Pump From Dry Run?

When you use a submersible pump, you can rest assured that the motor and other parts of the unit are hermetically sealed from water damage. This helps to increase efficiency and ensure a longer life span for your investment.

These pumps are designed to function underwater without the need for priming. This reduces the need for setup and maintenance, resulting in more efficient operations with better results.

Install an External Conductivity Probe

Dry run is a serious concern for submersible pumps because it can cause irreparable damage to the pump. It can lead to a complete loss of suction, damaging major components including the shaft, rear casing, pump cover and impeller.

One way to protect a submersible pump from dry run is to install an external conductivity probe. These sensors have an electrical potential to ground and are designed to alert the pump controller when the water content in the sample changes to a level that will trigger an alarm.

Most conductivity probes consist of a metal conductor surrounded by an insulator. Some use a single sensor, while others have a pair of sensors connected in series by an electrical connection between the probe terminals (figure 2).

The moisture content in a sample will decrease the resistance between the conductivity sensor terminals, indicating that there is a problem with the circuit and prompting the pump controller to send an alarm. The pump controller can be programmed to recognize a certain value of resistance between the two probe terminals that will trigger an alarm when the water content in the sample exceeds a set point.

A submersible pump will also have some type of electrical switch or control that will tell the controller when the temperature rises to a certain threshold. This can include a float switch, a proximity sensor or an infrared thermometer.

When a submersible pump is disassembled, it is important to disconnect the sensor leads before removing the stator. Attempting to remove the stator without disconnecting the leads can break them or damage the sensor, which may cause problems in future.

In addition to the moisture sensor, some submersible pumps may have a temperature sensor and a vibration transducer. These types of sensors will not be immediately noticeable when disassembling the pump, but can cause trouble later on if they are not replaced in time.

Most submersible pumps will have a power cable seal housing at the top of the stator, with the leads entering the pump from that area. Typically, the incoming cables will have extra control leads that connect to the starter or controller.

Install a Low Cut-Off Pressure Switch

A low cut-off pressure switch is used to control the power to an air bladder based water pump that pressurizes your home's plumbing system. The switch opens a set of electrical contacts when the desired pressure is reached, and closes them to stop the pump once the pressure falls below the preset level.

Depending on your needs, there are a number of different types of switches available to meet your requirements. Most of them are standard duty, designed for small electric pumps and compressors up to 2 horsepower on 120 volt motors or up to 3 horsepower on 240 volt motors.

If you have a larger pump, there are heavy duty air or water pressure switches that are rated for up to 250 PSI and can operate as high as 5 horsepower on 240 volt motors. These switches are available with an auto/off lever and unloader valves to unload the pump and air line after the motor is shut off.

Some switches have a differential, which means that they can be adjusted to allow a wider or narrower spread between the cut-in and cut-out pressures. However, some switches have fixed, non-adjustable differentials that cannot be changed.

To adjust your switch, use a gauge in your system to make accurate adjustments. You will need to run the pump a few times to see how your settings affect your pump performance.

In some cases, a pump can dry out over time because of leaks in the system or because it runs too long. When this happens, it can cause a buildup of water in the bladder, which can eventually lead to failure.

One of the best ways to prevent this is to install a low cut-off pressure switch on your pump. This will keep your pump from running dry, and can protect the air bladder from damage by lowering the pressure of the bladder when the pump is not operating.

When installing your low cut-off pressure switch, it is important to use a quality switch that will not fail because of the excessive strain. This is why most commercial reverse osmosis systems and some high-end residential ro systems use Boshart's low cut-off pressure switches.

Install an Electric Pump Protection Control

Dry running is one of the most common causes of pump failure. When a submersible pump runs without water for a prolonged period, the pump and motor can get seriously damaged. If you can protect your pump from dry running, it will last longer and work better.

The most effective way to protect a pump from dry run is to install an electric pump protection control. These devices shut off the pump and start it up again as soon as the level of water rises to a safe operating point.

Some of these devices also offer a feature that allows the operator to set a restart delay, which allows the water well to recover after a short amount of time before power is again turned back on to the motor. This is important because it prevents the pump from being restarted while the well is still in a low-water condition.

In addition to protecting against dry running, many of these devices also monitor the motor load and power line conditions. This provides complete system status and helps identify possible problems with the motor and the power line, such as low-flow wells, abnormal line voltage conditions or water logging in the tank.

A relay can sense when the current or power draw of a pump is lower than expected (see Image 1 below). This may happen when a low-flow well reduces the intake fluid or when a mechanical problem such as a bad drive coupling or belts increases the load on the motor.

Other common underload conditions that can be detected by these devices include a loss of pump flow due to a restriction in the intake or a closed discharge valve on the motor, which will cause a significant decrease in current or power draw.

When this occurs, a relay will switch off the motor until the problem is repaired and the motor can operate again. This will prevent the motor from overheating and damaging itself.

Franklin Electric offers a range of electric pump protection controls that are specifically designed to extend the life of submersible pump motors. They are available for a variety of sizes and types of motors, from 1/3HP to 5HP.

Install a Prime Plug

One of the best ways to protect your submersible pump from dry run is to install a prime plug. This will prevent air from entering the pump and causing damage to the electrical components.

First, find a suitable prime plug for your pump, which is often located on the top of the unit. This plug is usually made of plastic or rubber. Apply a little bit of pipe dope or teflon tape to its threads. Then, locate a hose and fill it with water until it reaches the base of the pump.

Next, switch on the power supply and run it for several minutes to remove any remaining air from the system. Then, you can replace the prime plug and precharge the pressure tank to get the pump back up and running again.

If the pump still has trouble, you should check if there is an air leak in the pipe leading from the pump to your home. If so, this can cause the pump to lose its prime and subsequently shut down.

In addition, you should check to see if the pressure relief valves in the pump are open or closed. If they are closed, you may have air trapped in the pump and this can also lead to a loss of prime.

Another option is to manually prime the pump. This is not as effective as a dry run protection device, but it can be helpful if the water pump has been turned off for a period of time or is having problems due to a power outage.

If you don’t have a priming plug available, you can prime your pump with garden hose (if you have a nearby independent water source). This is the easiest way to do it. The key is to make sure you are using clean water and don’t have any dirt or debris in the hose. You should repeat this process several times to ensure that the pump has successfully primed itself. If the priming process doesn’t work, you might need to have a professional plumber inspect your water pump and replace any parts that are causing the problem.