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Switching units for pumps

Switching units control and in some cases regulate the operation of your pump. Correctly selected pressure switch, flow switch or float switch will not only ensure the correct operation of the pump, but will also extend its life, prevent dry running or even reduce energy requirements.

For domestic waterworks, self-priming and submersible pumps in wells and boreholes, it is necessary to install a switching unit. This device ensures that when the tap is opened the pump starts pumping immediately and ensures that the required pressure is maintained. In the same way, the switch switches off the pump when the intake is finished. This will also happen in the case of dry running, which could damage the pump.

Types of switching units

There are several ways to control pumps and domestic waterworks. On our site you will find Grundfos and Wilo pressure, flow, combined, as well as float switches. Their use differs according to the following requirements and parameters:

  • Switching unit combining pressure and flow switch

The most sold and most complex option in terms of pump control is a switch combining a flow and pressure sensor. When the tap is opened, the pressure drops first and the switch turns on the pump. When the tap closes, the second sensor detects a stop in the flow and switches off the pump before the pressure in the system rises.

  • Pressure switching unit

Pressure switches are mainly used for water supply sets in combination with a pressure vessel. They switch on the pump so that pressure in the vessel remains within the set range. During water intake pressure drops, the switch detects it and switches on the pump. When the water draw-off is finished, the pump runs until the pressure in the tank reaches the required value again. In practice, pumping by thirds of the volume of the pressure vessel is usually used. By default the pressure vessel is full by two thirds of the volume and the pump is switched off. After opening the tap, water starts to flow, but the pump does not start again until the switching unit detects a drop below ⅓ of the volume. The pump runs until the volume is re-pumped to two thirds.

  • Flow switching unit

Flow switching units are used mainly in waterworks, where there is only a hose in the well and it is not possible to install a float sensor. For this reason, flow is monitored directly at the pump. The pump's ON function itself is then similar to the switching unit combining a flow and pressure sensor.

  • Float switching unit

Float switching units are mainly used for submersible pumps, where they are installed directly on the pump, and they switch off the pump in case of lack of water. Float switches are therefore only suitable as dry-running protection.

  • Electronic fully automatic float switch
  • Switching pressure 1 - 3.5 bar
  • Electronic automatic pressure guard
  • Switching pressure 1.5 bar

How to choose a switching unit?

Selection of the switching unit should be based mainly on:

  • Application
  • Maximum flow,
  • Switching pressure: can be fixed, but is adjustable for most products,
  • Fitted with dry-running protection and automatic restart,
  • Fitted with a non-return valve,
  • Fitted with a frequency converter,
  • Method of installation (horizontal, vertical) and connection dimension.

Do switching units also have another functions?

For example, built-in protection against dry running, when the unit runs the automatic restart function after a given time. Advanced control units can maintain a constant pressure thanks to continuous speed control by a frequency converter. They also manage to delay the shutdown of the pump to prevent it from cycling, and they also don't lack motor current protection.

At the same time, it is possible to set ON and OFF switching pressures for selected products. A built-in display in combination with LEDs shows the current operating status and ongoing activities. A leak sensor also serves for better protection of the pump. Some switches are also equipped with a manometer.

How to prevent your pump from cycling?

For minor leaks in the piping or other negligible pressure losses, the solution may be to install a Wilo BRIO 2000 TANK flow switch equipped with a 0.4 liter pressure vessel, which is especially suitable for domestic waterworks. This way it is possible to prevent cycling (repeated switching of the pump) and thus extend its life.

How to install a switching unit?

Installation is easy. It is usually sufficient to connect the power cable, which is usually part of the switching unit, and connect the switch to the water pipe in any location between the pump itself and the first supply point. The operation of these units is usually completely noiseless, depending on the purpose and method of construction, they are often also equipped with an integrated non-return valve.