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Demystifying the MEI pump efficiency index

This year sees the introduction of the Minimum hydraulic Efficiency Index for pumping equipment. Gary Wilde warns of the implications
Over the past few years, the European Commission has developed a methodology to determine mandatory minimum efficiency levels for some electronic product groups sold within the European Union, known as 'European Minimum Energy Performance Standards' (EU MEPS). That list of products now includes clean water pumps.

Because 80 per cent of a product's energy efficiency is defined during its design stage, it is precisely this part of the production process that is targeted by the EU MEPS. Influencing the design of products sold in the EU is therefore crucial; hence the name of the Eco-Design Directive for these new standards.

While pumps were originally exempt from the Directive, they were later included when their full energy efficiency potential was identified as a major area of improvement for the domestic and commercial sectors. Pumps that now fall within the Eco-Design Directive are end suction own bearing pumps and end suction close coupled pumps, close coupled in-line pumps, multi-stage vertical pumps, and multi-stage submersible pumps.

To ensure that any design changes made across the pumping industry can deliver maximum hydraulic efficiency standards, the European Commission conducted a regular evaluation of existing pumps on the open market to identify those which are not performing in line with the new criteria.

The Minimum Efficiency Index (MEI) identifies a minimum efficiency cut-off for those pumps performing under the new hydraulic efficiency levels. The first cut-off point got reinforced on 1 January 2013, while the second one, more stringent yet, will come into force on the same date in 2015. Products with lower efficiency levels than the new requirements will not be eligible to carry a CE mark, making it illegal to place them on the open market anywhere within the European Union.
The MEI outlines the minimum efficiency levels that manufacturers must meet. For a specific pump design and size, the minimum efficiency is a value determined by the head, flow, speed and a constant that depends on the design of the pump being measured.

Many industries assume that, if a product performs well at the point of maximum output, it can be deemed environmentally friendly. In reality though, a product should be designed to perform at its most energy efficient throughout its entire cycle and this is especially true for pumping equipment.

The minimum hydraulic efficiency must be calculated at three different points on the pump curve. Those manufacturers who succeed in meeting the minimum efficiency levels at all three points can achieve an overall high efficiency rating. The first point on the curve is the best efficiency point (BEP).

This is the operating point at which the pump runs at maximum hydraulic efficiency. The second point is the part load (PL) which is when the pump is operating at 75 per cent of the flow at BEP. The final point is the over load (OL) which describes the point at which the pump is running at 110 per cent of the flow at BEP.

This year, all pumps placed onto the market in Europe must perform at a minimum level of efficiency, calculated at the BEP, PL and OL operating points in order to meet or exceed the MEI Index of 0.1. This index value, multiplied by 100, corresponds to the percentage of pumps currently in the market which do not meet the 2013 regulation - MEI 0.1 therefore indicates that 10 per cent of pumps available for purchase do not meet the standards set by the European Commission.

In 2015, the standards become more restrictive with the MEI requirement increasing to a rating of 0.4 meaning 40 per cent of purchasable pumps today will fall below European standards.

Pumps placed onto the market by the manufacturer prior to the enforcement of the new European Directive can be sold by the distribution chain and put into service by the end user legally. Despite this flexibility, contractors and installers should be looking to bring their business practices in-line with the new laws as soon as possible in order to hit the ground running when the legislation becomes mandatory.

The easiest way to prevent being caught unprepared by the change in law is to start purchasing and installing compliant pumps straight away. To make the switch over as simple as possible for its customers, Xylem has ensured that all of its pumps affected by the legislation already meet the 0.1 MEI rating. Xylem customers therefore, can rest assured that the pumps they are purchasing meet the exacting requirements of the European Commission.

// The author is business development and marketing manager for Xylem Lowara UK //
13 May 2013

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