Grundfos SQ/SQE Protection features: Soft Start

Find out how the soft start feature of the SQ/SQE brings an improved alternative to conventional 4” submersible pumps, offering quicker installation and increased pump reliability.

The Grundfos SQ/SQE submersible pump range comes equipped with three unique protection features. In this video, we’ll focus on soft-start and show how this feature benefits both installer and homeowner.To illustrate our point, we’ll compare the SQ/SQE range with a 4” submersible pump with a conventional one- or three-phase motor.

Let’s begin with the 4” pump.

The most commonly used starting method for motors in 4” conventional pumps is called Direct On Line (DOL). In layman’s terms: Full speed ahead. Single-phase motors are unable to start unassisted when using DOL. They require a device called a motor starter to get the motor up and running. The motor starter can be integrated in the motor but often it is mounted externally between the drop cable and the power supply cable, demanding extra installation work. Three-phase motors do not need a motor starter a DOL start-up. So why is this an issue? Well, when a pump motor is started using DOL, the nominal speed is reached almost immediately. During the first milliseconds of the start the motor current can reach a level of up to seven times higher than the nominal value.

This method has several drawbacks:

1) The abrupt start-up can lead to disruptions of other electrical devices connected to the same power supply, for instance lighting.

2) It can also produce a burst of water, causing a liquid hammer effect. These bursts may reduce the lifetime of the installation.

3) Lastly, it can cause the pump to shift in the well as a physical counter-reaction to the acceleration of the rotating parts.

This will also contribute to reduced system lifetime.

Now, let’s have a look at the SQ/SQE range. All the pumps in this range have an integrated frequency converter and do not require a motor starter. Due to the features of the integrated frequency converter, the pump offers a smooth start-up. The motor speed increases slowly and reaches the nominal value within a period of 2 seconds.

This slow increase in speed keeps the motor current low and eliminates the risk of electrical disruptions. On top of this, the flow rate increases proportionally to the motor speed, which means that there are no sudden bursts of water at the taps. While keeping pump movements at an absolute minimum.

So, let’s recap the benefits. Overall, the soft start reduces the load on the electrical and mechanical installation. For the installer, the soft start feature means a quick and simple installation, with no need for motor contactors. For the homeowner, the soft start feature means no disruptions of electrical appliances and no sudden water bursts when the pump starts. It also means that the pump will run reliably for years, with minimum wear to the system.

Course overview

Modules: 7
Completion time
Completion time: 40 minutes
Difficulty level
Difficulty level: Intermediate