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Grundfos Pumps - Handy Pump References

Pump Curves - QH-Curve - Power Consumption - Pressure Differential

Useful information to help you make better pump selections

Grundfos deliver a wide range of products that encompass a huge number of applications. Our pumps are designed to provide excellent reliability and meet or exceed current energy efficiency regulations. To deliver a complete solution, we offer a comprehensive range of drives, controls, energy-efficient motors and sensors, which are combined to offer seamless functionality and integration.

This page has been compiled to identify some of the basics that will help you to understand the various options and therefore make better pump selection choices.

Pump curves - explained

The pump performance curve shows the correlation between media flow (Q) and the pressure differential or head (H) that the pump creates.

Flow is normally given in m³/h or l/s. Pressure differential or head is given in kPa or mwc (meter water column). For variable-speed pumps, the performance curve is given at minimum and maximum RPM.

The QH-curve

The QH-curve shows the head, which the pump is able to perform at a given flow. Head is measured in meter liquid column [mLC]; normally the unit meter [m] is applied. The advantage of using the unit [m] as the unit of measurement for a pump’s head is that the QH-curve is not affected by the type of liquid the pump has to handle.

Efficiency - the η-curve

The efficiency is the relation between the supplied power and the utilised amount of power. In the world of pumps, the efficiency ηP is the relation between the power, which the pump delivers to the water (PH) and the power input to the shaft (P2).

Power within the pump

Power consumption (P)

Pumps are made of several components. The power consumption of the different components is designated in the following way:

P1 - The power input from the mains or, put in another way, the amount of power the consumer has to pay for.

P2 - The power input to the pump or the power output from the motor. Often referred to as shaft power.

PH - Hydraulic power – the power that the pump transfers to the liquid in the shape of flow and head.

For the most common pump types, the term “power consumption” normally refers to P2. Power is measured in W, kW.

Power Consumption

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Grovebury Road
Leighton Buzzard
Bedfordshire
LU7 4TL

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Tel: 01525 850000

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