{"id":5522,"date":"2022-02-28T16:53:00","date_gmt":"2022-02-28T15:53:00","guid":{"rendered":"https:\/\/www.idro-elettrica.it\/esperto-risponde\/ive-noticed-that-the-centrifugal-pump-catalog-lists-the-mei-value-can-you-clarify-what-this-refers-to\/"},"modified":"2026-07-01T09:47:38","modified_gmt":"2026-07-01T07:47:38","slug":"ive-noticed-that-the-centrifugal-pump-catalog-lists-the-mei-value-can-you-clarify-what-this-refers-to","status":"publish","type":"esperto-risponde","link":"https:\/\/www.idro-elettrica.it\/en\/esperto-risponde\/ive-noticed-that-the-centrifugal-pump-catalog-lists-the-mei-value-can-you-clarify-what-this-refers-to\/","title":{"rendered":"MEI Index: What It Means and When It Is Required"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\"><em>MEI Index<\/em>: This is the value listed in centrifugal pump catalogs that indicates the minimum efficiency requirement mandated by regulations for certain categories of clean-water pumps.<\/p>\n\n<div class=\"wp-block-rank-math-toc-block\" id=\"rank-math-toc\"><h2>Table of Contents<\/h2><nav><ul><li class=\"\"><a href=\"#perche-oggi-trovi-il-mei-nel-catalogo-delle-pompe\">Why You&#8217;ll Find the MEI in the Pump Catalog Today<\/a><\/li><li class=\"\"><a href=\"#direttiva-er-p-e-regolamento-547-2012-lotto-11-il-contesto\">ErP Directive and Regulation 547\/2012 (Lot 11): The Context<\/a><\/li><li class=\"\"><a href=\"#cosa-significa-mei-minimum-efficiency-index-e-perche-e-importante\">What Does MEI (Minimum Efficiency Index) Mean, and Why Is It Important?<\/a><\/li><li class=\"\"><a href=\"#a-quali-categorie-di-pompe-si-applica-lindice-mei\">To which categories of pumps does the MEI index apply?<\/a><\/li><li class=\"\"><a href=\"#date-di-applicazione-e-valori-mei-indicati\">Effective dates and MEI values listed<\/a><\/li><li class=\"\"><a href=\"#indice-mei-ed-efficienza-cosa-misura-davvero-e-cosa-esclude\">The MEI Index and Efficiency: What It Really Measures (and What It Excludes)<\/a><\/li><li class=\"\"><a href=\"#come-si-determina-la-minima-efficienza-richiesta-algoritmo-e-parametri\">How to Determine the Minimum Required Efficiency: Algorithm and Parameters<\/a><\/li><li class=\"\"><a href=\"#verifica-della-conformita-i-3-punti-bep-pl-e-ol\">Compliance Check: The 3 Points\u2014BEP, PL, and OL<\/a><\/li><li class=\"\"><a href=\"#conclusione\">Conclusion<\/a><\/li><\/ul><\/nav><\/div>\n\n<h2 id=\"perche-oggi-trovi-il-mei-nel-catalogo-delle-pompe\" class=\"wp-block-heading\">Why You&#8217;ll Find the MEI in the Pump Catalog Today<\/h2>\n\n<p class=\"wp-block-paragraph\">In recent years, the European Commission has taken steps to establish mandatory minimum efficiency levels for certain product groups sold within the European Union. This initiative also includes <strong>clean water pumps<\/strong>, to which these standards have been applied <strong>since January 1, 2013<\/strong>. <\/p>\n\n<p class=\"wp-block-paragraph\">The key point for anyone reading a technical catalog is that the value listed (MEI) is not merely \u201cadditional information\u201d: it is an indicator linked to <strong>efficiency requirements<\/strong> that affect the product\u2019s marketability within the European Union.<\/p>\n\n<h2 id=\"direttiva-er-p-e-regolamento-547-2012-lotto-11-il-contesto\" class=\"wp-block-heading\">ErP Directive and Regulation 547\/2012 (Lot 11): The Context<\/h2>\n\n<p class=\"wp-block-paragraph\">The European Commission has issued (in the text) the <strong>ErP Directive 2009\/125\/EC<\/strong>, which establishes the legislative framework governing the energy consumption of energy-using products. In the same context, it is noted that, for many years now, attention has been focused on mandatory minimum efficiency levels for certain categories, including: <\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong>Electric Motors<\/strong><\/li>\n\n\n\n<li><strong>Wet-Rotor Circulators<\/strong><\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">For pumps, the document resulting from the ErP Directive is <strong>Regulation 547\/2012 (Lot 11)<\/strong>, which introduces<strong>the MEI index<\/strong> for specific Pump Types.<\/p>\n\n<h2 id=\"cosa-significa-mei-minimum-efficiency-index-e-perche-e-importante\" class=\"wp-block-heading\">What Does MEI (Minimum Efficiency Index) Mean, and Why Is It Important?<\/h2>\n\n<p class=\"wp-block-paragraph\"><strong>MEI = Minimum Efficiency Index<\/strong>. In practical terms, the MEI corresponds to a <strong>minimum threshold<\/strong>: products <strong>that fall<\/strong> below this threshold cannot be placed on the market. <\/p>\n\n<p class=\"wp-block-paragraph\">The value listed in the catalog, therefore, serves to clarify the pump\u2019s performance relative to this minimum efficiency requirement. And this is a point that directly impacts compliance: the text specifies that, since the MEI is one of the parameters that must be met in order to affix the <strong>CE marking<\/strong> to the product, pumps that do not meet the required efficiency levels <strong>cannot legally be placed<\/strong> on the European Union market. <\/p>\n\n<h2 id=\"a-quali-categorie-di-pompe-si-applica-lindice-mei\" class=\"wp-block-heading\">To which categories of pumps does the MEI index apply?<\/h2>\n\n<p class=\"wp-block-paragraph\">Regulation 547\/2012 (Lot 11) introduces the MEI index for the following categories of pumps (as listed):<\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong>Standardized single-impeller horizontal pumps with a base (ESOB)<\/strong><\/li>\n\n\n\n<li><strong>Vertical Multistage Pumps (MS-V)<\/strong><\/li>\n\n\n\n<li><strong>Single-impeller Monobloc Pumps (ESCC)<\/strong><\/li>\n\n\n\n<li><strong>4\u201d and 6\u201d Multistage Submersible Pumps (MSS)<\/strong><\/li>\n\n\n\n<li><strong>In-line Monoblock Pumps (ESCCi)<\/strong><\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">The text also includes a brief key to the abbreviations:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>ESOB End-Suction Self-Supporting Bearing Pump<\/li>\n\n\n\n<li>ESCC End-Suction Close-Coupled Pump<\/li>\n\n\n\n<li>ESCC Inline End-Suction Close-Coupled Pump<\/li>\n\n\n\n<li>MS Multistage Pump<\/li>\n\n\n\n<li>MSS Submersible Multistage Pump<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">This classification is useful because the efficiency requirement (and the related verification) begins with identifying the pump within the specified Pump Types.<\/p>\n\n<h2 id=\"date-di-applicazione-e-valori-mei-indicati\" class=\"wp-block-heading\">Effective dates and MEI values listed<\/h2>\n\n<p class=\"wp-block-paragraph\">The text lists two operational deadlines along with their corresponding values:<\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong>Effective January 1, 2013: MEI = 0.1<\/strong><\/li>\n\n\n\n<li><strong>Effective January 1, 2015: MEI = 0.4<\/strong><\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">These dates are intended to provide a framework for when the required levels take effect, serving as a timeline for the application of the regulation to the affected pumps.<\/p>\n\n<h2 id=\"indice-mei-ed-efficienza-cosa-misura-davvero-e-cosa-esclude\" class=\"wp-block-heading\">The MEI Index and Efficiency: What It Really Measures (and What It Excludes)<\/h2>\n\n<p class=\"wp-block-paragraph\">Here is a point that often causes confusion:<strong>the MEI index<\/strong> is presented as a measure of a pump\u2019s quality in terms of its efficiency, but it is specified that it refers to<strong>the pump\u2019s HYDRAULIC efficiency<\/strong>.<\/p>\n\n<p class=\"wp-block-paragraph\">The text also clarifies what is not included in the MEI: <strong>the engine is not part of this discussion in any way<\/strong>. Engine efficiency is referred to as \u201canother matter,\u201d distinct from the issue of hydraulic efficiency as assessed by the MEI index. <\/p>\n\n<h2 id=\"come-si-determina-la-minima-efficienza-richiesta-algoritmo-e-parametri\" class=\"wp-block-heading\">How to Determine the Minimum Required Efficiency: Algorithm and Parameters<\/h2>\n\n<p class=\"wp-block-paragraph\">The minimum required hydraulic efficiency is determined using an <strong>algorithm<\/strong> that takes into account:<\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong>prevalence<\/strong><\/li>\n\n\n\n<li><strong>Flow rate<\/strong><\/li>\n\n\n\n<li><strong>speed<\/strong><\/li>\n\n\n\n<li><strong>a constant<\/strong> directly related to the Pump Type being evaluated<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">In other words, the requirement is not a \u201csingle\u201d number that is the same for all pumps: it depends on the performance parameters and the pump family (ESOB, ESCC, MS-V, MSS, ESCCi).<\/p>\n\n<h2 id=\"verifica-della-conformita-i-3-punti-bep-pl-e-ol\" class=\"wp-block-heading\">Compliance Check: The 3 Points\u2014BEP, PL, and OL<\/h2>\n\n<p class=\"wp-block-paragraph\">The minimum hydraulic efficiency is verified by calculating the efficiency at <strong>three points<\/strong> within the pump&#8217;s performance range:<\/p>\n\n<ol class=\"wp-block-list\">\n<li><strong>BEP (Best Efficiency Point)<\/strong>: the point at which the pump operates with maximum hydraulic efficiency<\/li>\n\n\n\n<li><strong>PL (Part Load)<\/strong>: where the pump operates at <strong>75% of the flow rate<\/strong> measured at BEP<\/li>\n\n\n\n<li><strong>OL (Over Load)<\/strong>: when the pump operates at <strong>110% of the flow rate<\/strong> measured at BEP<\/li>\n<\/ol>\n\n<p class=\"wp-block-paragraph\">The pump is <strong>certified<\/strong> when the efficiency calculated at these three points falls within the limits set by the Regulation.<\/p>\n\n<h2 id=\"conclusione\" class=\"wp-block-heading\">Conclusion<\/h2>\n\n<p class=\"wp-block-paragraph\">The <strong>MEI index<\/strong> value listed in the catalog tells you whether (and how) a pump meets the minimum efficiency requirements introduced by <strong>Regulation 547\/2012 (Lot 11)<\/strong> under the ErP Directive. It is an indicator related to<strong>the pump\u2019s hydraulic efficiency<\/strong>, not the motor\u2019s efficiency, and is measured at three points (BEP, PL, OL) across the performance range. <\/p>\n\n<p class=\"wp-block-paragraph\"><\/p>\n","protected":false},"excerpt":{"rendered":"<p>MEI Index: In centrifugal pump catalogs, this indicates the minimum efficiency level required for a product to be placed on the EU market. Let\u2019s take a look at what this means, which pumps it applies to, and how compliance is verified. <\/p>\n","protected":false},"featured_media":5523,"parent":0,"template":"","meta":{"_acf_changed":false,"_angie_page":false,"footnotes":"","_members_access_role":[],"_members_access_error":""},"tags":[1305,1302,1253,1304,1301,1303,1298,1297,1299,1300],"class_list":["post-5522","esperto-risponde","type-esperto-risponde","status-publish","has-post-thumbnail","hentry","tag-bep-pl-ol","tag-ce-marking","tag-centrifugal-pumps","tag-clean-water-pumps","tag-erp-directive","tag-hydraulic-efficiency","tag-mei","tag-mei-index","tag-minimum-efficiency-index","tag-regulation-547-2012"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/esperto-risponde\/5522","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/esperto-risponde"}],"about":[{"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/types\/esperto-risponde"}],"version-history":[{"count":0,"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/esperto-risponde\/5522\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/media\/5523"}],"wp:attachment":[{"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/media?parent=5522"}],"wp:term":[{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/tags?post=5522"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}