Grundfos helps you understand efficiencies for wastewater pumps

Increasing concerns about CO₂ emissions and energy costs has led to greater focus on energy use worldwide. Grundfos is uniquely positioned to ensure a correct understanding of efficiencies and how these combine with hydraulic free passage and constructional robustness in state-of-the-art wastewater pumps.

Environmental issues have led to legislation that places new requirements on wastewater handling. Pumping wastewater through the collection network or around the treatment plant already accounts for a substantial part of the energy bills faced by municipalities and water utilities.

By choosing state-of-the-art wastewater pumps with the highest total efficiency, no compromise on hydraulic free passage and constructional robustness, you are well on the way to bringing down CO₂ emissions and reducing operating costs for wastewater pump systems.

Below you will find how Grundfos talks efficiencies on wastewater pumps. Unfortunately there is as yet no minimum efficiency standard for wastewater pumps, unless they are driven by fan-cooling electrical normmotors. At Grundfos, we have vast experience working with efficiency standards, and we also set our own standards to ensure optimum motor efficiency for our customers. We have prepared the following guide about wastewater pump efficiency, which will help you make the correct pump selection and avoid the most common pitfalls.

Total efficiency

What matters to your energy bill is the total efficiency — meaning the total wire-to-water efficiency defined in the ISO 9906:2012 — and ANSI/HI 11.6 standards to which all wastewater pumps are tested. In a wastewater pump there will be electrical, mechanical, and hydraulic losses. A pump manufacturer needs to master all of these without compromising reliability. Grundfos does precisely this and can therefore supply high efficiency products.

Electrical efficiency

The IEC 60034-30 - Part 30 (Ed.1.0) standard defines the minimum efficiency classes (IE codes) for electrical motors, single-speed, three-phase, cage-induction fan-cooled motors. When Grundfos states that a wastewater pump is made from IE3 motor components, it means that the motor components (i.e. stator and rotor), if built into a fan-cooled electrical norm motor, will meet and pass the IE3 efficiency class mentioned in the IEC 60034-30 standard.

Why not mark the wastewater pump with an IE3 label?

This cannot be done based on two points: First of all the IEC 60034-30 standard does not apply to other motors than single-speed, three-phase cage-induction motors i.e. not motors integrated in wastewater pumps. Secondly the constructional differences between a norm motor and a wastewater pump with integrated motor adds additional mechanical efficiency losses to the wastewater pump motor (e.g. angular contact bearings, shaft seal, etc.).

Mechanical efficiency

Pump efficiency is only interesting if reliability is not compromised. Pump maintenance is costly, whether planned or unplanned, and Grundfos does not compromise on reliability with our products. For constructional robustness with key components, Grundfos for example, uses:

• Angular contact bearings: Even though angular contact bearings have higher friction losses compared to ordinary roller bearings, we have decided to keep these types of bearings to gain longer lifetime in heavy-duty operation.
• Shaft seal: Grundfos pumps come with double mechanical shaft seals in a cartridge solution. This robust construction consumes additional energy, but ensures longer operational time and less downtime. Replacement is easily done in the field without the use of special tools.

Hydraulic efficiency

Traditionally there has been a trade-off between free passage in hydraulics for reduced clogging, and high efficiency. Grundfos has resolved this traditional compromise and is able to supply wastewater pump systems that offer superior hydraulic efficiency over a wide operating range without compromising free passage.

Reading curve charts and technical information

When reading curve charts and technical information the following needs to be observed. First of all one needs to be sure that the information given is according to the international performance acceptance test standards ISO 9906:2012 or ANSI/HI 11.6. Otherwise it will not be possible to compare the different pump manufacturers’ products against each other.

Secondly always make sure to use the total efficiency as reference. Only by learning about the total efficiency can you be sure that all internal losses due to friction developed in bearings, shaft seals, etc. are included.

An example of this can be seen below. In the curve chart the pump performance curves are shown. The upper efficiency curve (Eta2) is the pump efficiency curve (eta pump). The lower efficiency curve (Eta1) is the total efficiency curve (eta pump + motor), taking all electrical, mechanical, and hydraulic losses into consideration.

The difference between the two efficiency curves is the sum of all other losses (electrical and mechanical), and includes hereby also friction losses from e.g. angular contact bearings and shaft seal that is needed to make a robust wastewater pump.

Many companies publish “motor efficiency” as well, often as one figure valid for the best efficiency point (BEP). When using the motor efficiency, always pay attention to what is included, as some include only the electrical losses, and hereby ignore the mechanical losses.

So — once again — always compare total efficiency during pump selection, as it is the only efficiency figure defined by international standards, and what matters to your energy bill.

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To realise the hidden savings in your pumps, we offer a Grundfos Energy Check. By simple inspection of your pump installation, we calculate potential savings and make suggestions for high performing, energy efficient solutions. A free report is included with every Grundfos Energy Check detailing your current pump installation and operation costs and how you can improve it to realise the savings. Find out more here: www.expertenergycheck.com

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The Grundfos Product Center is an online search and sizing tool that helps you choose the right pump for installation or replacement, or find information about pumps you already have. Go to www.grundfos.com.au and follow the links.