One of the most common reasons for damaging your pump is dry running. It's a situation where the pumped liquid does not flow through the pump and air is sucked into it. Lack of water will increase internal temperature, which can have destructive consequences for some parts of the pump.
We recommend the installation of a level sensor to protect your pump.
Conductivity probes operate on the principle of a closed electrical circuit and are a cheap and reliable protection against dry running. The advantage of this solution is that the pump is switched off before it runs dry or sucks in air. For the control unit and the control unit with frequency converter, the pump is only switched off after a few seconds of dry running.
1. Protection of the pump against dry running
Conductivity probes protect submersible and drainage pumps against dry running when draining flooded areas.
This set consists of two SHR-2 probes, an HRH 7 switch and a certified cable for use in drinking water installations. One probe determines minimum level, the other probe then serves as a reference, so it must always be immersed. As soon as the water rises above the set minimum level, the HRH-7 switch runs the pump, which will pump the water.
2. Level monitoring in the well
To control the pump in the well, we install three SHR-2 probes, an HRH 7 switch and a certified cable for use in drinking water installations. We install two of the probes to the required minimum and maximum level. The third probe serves as a reference and is located below the one for minimum level. By pumping, water level in the well decreases. When the minimum level is reached, the pump switches off. On the other hand, when the maximum level is reached by naturally resetting, the pump switches on and starts pumping again. We recommend level monitoring for all borehole pumps.
3. FIlling of tanks
In this case we recommend the installation of two SHR-3 probes and the HRH 7 switch. The probes are installed using a weld-on piece or a fastening nut to the minimum and maximum level, either in the tank wall or its lid. The probes can be placed horizontally, vertically or in oblique position. The HRH-7 switch is connected to the probes by a certified two-core cable for use in drinking water installations. If the water falls below minimum level, probe opens the valve and tank gets filled to reach the maximum level, when it closes the valve. We recommend monitoring fluid leakage by installing a flood sensor on the floor nearby. In case of leakage, the switch signals GSM Communicator to send a text to your mobile phone.
More information about conductivity probes can be found here.
The electronic flow switch automatically switches the pump on and off. When the pressure drops (as you open the tap for example), the pump is switched off until 1/3 of the water in the pressure vessel is depleted. At this point, the pressure switch turns on the pump, which begins to fill up the tank with water. After water intake is finished (or the tap is closed), the pump does not switch off until it has refilled the water into the pressure vessel to the original volume. If there is no water in the pump, the flow switch switches it off, thus protecting it against dry running.
From the range of flow switches, we recommend the Wilo HiCONTROL 1 automatic flow and pressure monitor, which maintains a constant pressure, protects the pump from dry running and is noiseless.
More information about the product can be found here.
Control unit with frequency converter automatically switches the pump on and off. The device switches on the pump when the pressure in the distribution system drops (when the tap is opened and water consumed) and gradually fills water in. When the water draw-off is completed (tap is closed), the unit switches off the pump again.
For lower water consumption, the frequency converter starts the pump at a lower power, thus reducing energy consumption.
When the pressure drops due to air intake, the control unit switches off the pump and thus protects it from running dry.
We recommend the Wilo SIRIO 3x230 control unit with frequency converter, thanks to which you will not notice a drop in pressure with increased water consumption.
More information about the product can be found here.
On our site, it is also possible to get the Grundfos SCALA2 pump with built-in frequency converter, which constantly monitors values of the discharge pressure. If pressure falls below the required level, SCALA2 immediately increases its power and thus compensates for the pressure losses.
You can find more about SCALA 2 here.
The control unit measures and calibrates the energy consumption (overload protection) and the motor power factor (COS φ), and saves the data itself after approx. 15 seconds.
The response of the dry-running protection is very fast, switch box switches off the pump after approx. 5-10 seconds of air suction. The unit then signals a fault on the display. In this mode, the unit performs the first restart after 10 minutes (if there is still no water in the pump, then after 20, 40, 80 and 120 minutes). If the water column is refilled during restarts and the pump starts pumping normally, the system will return to normal mode. If there is not enough water even after 5 restarts (120 minutes), the system will go into fault and the pump must be restarted manually.
Cannot be used with drainage, vibration and screw pumps.
We recommend the CU 301 control unit, which has directly been developed for SQE submersible pumps in applications where constant pressure must be maintained.
More information can be found here.
Float switches are mainly used to monitor the level of fluid. The float is connected directly to the pump and is fitted with a toggle switch. If the pump is sufficiently submerged and the float is floating in a vertical position (ON), the contacts in the float are signaling that the pump can perform its function. As soon as the level drops to a certain level (OFF) during pumping, the weight in the flipped switch splits the contacts and the power supply to the pump is interrupted and immediately switched off.
Installation is only recommended if the space around the pump is large enough so that nothing prevents the float from moving.
It can be used with all types of pumps.