{"id":7902,"date":"2020-07-07T15:46:00","date_gmt":"2020-07-07T13:46:00","guid":{"rendered":"https:\/\/www.idro-elettrica.it\/esperto-risponde\/diesel-engine-power-for-fire-pumps-uni-en-12845-guide\/"},"modified":"2026-07-01T09:46:00","modified_gmt":"2026-07-01T07:46:00","slug":"diesel-engine-power-for-fire-pumps-uni-en-12845-guide","status":"publish","type":"esperto-risponde","link":"https:\/\/www.idro-elettrica.it\/en\/esperto-risponde\/diesel-engine-power-for-fire-pumps-uni-en-12845-guide\/","title":{"rendered":"Diesel Engine Power for Fire Pumps: UNI EN 12845 Guide"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\"><em>Diesel engine power for fire pumps<\/em>: This is the key issue when determining whether a diesel engine is truly suitable for driving a main pump. In this response, we review the criteria set forth in UNI EN 12845 and explain how to apply them in practice.* <\/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=\"#da-dove-partire-nella-uni-en-12845-punti-10-1-e-10-9-1\">Where to start with UNI EN 12845 (sections 10.1 and 10.9.1)<\/a><\/li><li class=\"\"><a href=\"#curva-caratteristica-della-potenza-cosa-devi-guardare-davvero\">Power Characteristic Curve: What You Really Need to Look For<\/a><\/li><li class=\"\"><a href=\"#motore-diesel-requisito-di-potenza-secondo-curva-na\">Diesel engine: power requirement according to the \u201cNA curve\u201d<\/a><\/li><li class=\"\"><a href=\"#caso-1-pompe-con-curva-di-potenza-senza-sovraccarico-es-vtp\">Case 1: Pumps with a power curve without overload (e.g., VTP)<\/a><\/li><li class=\"\"><a href=\"#caso-2-pompe-con-curva-di-potenza-crescente-es-centrifughe-monogiranti\">Case 2: Pumps with an increasing performance curve (e.g., single-impeller centrifugal pumps)<\/a><\/li><li class=\"\"><a href=\"#continuita-a-pieno-carico-e-quota-di-installazione-iso-3046\">Continuity at full load and installation altitude (ISO 3046)<\/a><\/li><li class=\"\"><a href=\"#checklist-rapida-di-verifica-coerente-con-i-criteri-citati\">Quick Verification Checklist (in accordance with the criteria mentioned)<\/a><\/li><li class=\"\"><a href=\"#conclusione\">Conclusion<\/a><\/li><\/ul><\/nav><\/div>\n\n<h2 id=\"da-dove-partire-nella-uni-en-12845-punti-10-1-e-10-9-1\" class=\"wp-block-heading\">Where to start with UNI EN 12845 (sections 10.1 and 10.9.1)<\/h2>\n\n<p class=\"wp-block-paragraph\">The UNI EN 12845 standard addresses the issue of the power required by the engine, clarifying in section <strong>10.1<\/strong> that the engine power must be calculated by considering the <strong>points on the<\/strong> pump\u2019 <strong>s power characteristic curve<\/strong> (this applies to both diesel and electric engines).<\/p>\n\n<p class=\"wp-block-paragraph\">For <strong>diesel engines<\/strong>, compliance with section <strong>10.9.1<\/strong> is also required; this section specifies a particular method for delivering the required power.<\/p>\n\n<h2 id=\"curva-caratteristica-della-potenza-cosa-devi-guardare-davvero\" class=\"wp-block-heading\">Power Characteristic Curve: What You Really Need to Look For<\/h2>\n\n<p class=\"wp-block-paragraph\">The criterion is not to \u201cchoose an engine based on gut feeling\u201d or to look at just a single value: the operational reference is the <strong>power curve<\/strong>.<\/p>\n\n<p class=\"wp-block-paragraph\">In other words, the <strong>points on the curve<\/strong> that represent the pump\u2019s power consumption levels are the ones that determine how much power the motor driving the pump (diesel or electric) must be capable of delivering.<\/p>\n\n<p class=\"wp-block-paragraph\">This step is essential because it shifts the focus from the \u201crated power\u201d to <em>where and how<\/em> the pump draws power during operation.<\/p>\n\n<h2 id=\"motore-diesel-requisito-di-potenza-secondo-curva-na\" class=\"wp-block-heading\">Diesel engine: power requirement according to the \u201cNA curve\u201d<\/h2>\n\n<p class=\"wp-block-paragraph\">To be consistent with the requirements for diesel engines, the engine must deliver the required power according to the <strong>NA curve<\/strong>, specified as:<\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong>Continuous power with 10% overload capacity<\/strong><\/li>\n\n\n\n<li><strong>DIN 6271 \u2013 ISO 3046-1<\/strong><\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">This is the performance profile in question: it\u2019s not enough to \u201creach it once\u201d; rather, the goal is to maintain a continuous power output in line with the curve shown.<\/p>\n\n<h2 id=\"caso-1-pompe-con-curva-di-potenza-senza-sovraccarico-es-vtp\" class=\"wp-block-heading\">Case 1: Pumps with a power curve without overload (e.g., VTP)<\/h2>\n\n<p class=\"wp-block-paragraph\">In the case of <strong>pumps with a power characteristic curve without overload<\/strong>, the criterion is clear: the <strong>diesel engine<\/strong> must have a power rating <strong>higher<\/strong> than that required by the pump, specifically:<\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong>greater than the maximum power consumption at the peak of the power curve<\/strong><\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">In the original text, this case is attributed\u2014for clarity\u2019s sake\u2014to <strong>VTPs<\/strong>. The practical point is that the \u201cpeak\u201d of the curve serves as the benchmark for the test: if the engine does not reach that maximum, it is not adequate. <\/p>\n\n<h2 id=\"caso-2-pompe-con-curva-di-potenza-crescente-es-centrifughe-monogiranti\" class=\"wp-block-heading\">Case 2: Pumps with an increasing performance curve (e.g., single-impeller centrifugal pumps)<\/h2>\n\n<p class=\"wp-block-paragraph\">In the case of <strong>pumps with an increasing power characteristic curve<\/strong>, the comparison is not based on the \u201cpeak\u201d in a general sense, but on the condition under which the pump requires a specific NPSHr to operate.<\/p>\n\n<p class=\"wp-block-paragraph\">The specified requirement is that the diesel engine must have a power output of:<\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong>greater than the power consumed by the pump when it requires an NPSHr of 16 m<\/strong><\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">In the original text, this is associated\u2014to clarify\u2014with <strong>single-stage centrifugal pumps<\/strong>. Here, the operational concept is as follows: identify that operating point (linked to the specified NPSHr) and verify that the motor power is greater than the power consumption under those conditions. <\/p>\n\n<h2 id=\"continuita-a-pieno-carico-e-quota-di-installazione-iso-3046\" class=\"wp-block-heading\">Continuity at full load and installation altitude (ISO 3046)<\/h2>\n\n<p class=\"wp-block-paragraph\">In addition to the \u201cgreater than\u2026\u201d requirement, there is a performance requirement: the engine must be capable of delivering that power:<\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong>continuously at full load<\/strong><\/li>\n\n\n\n<li><strong>at the installation level<\/strong><\/li>\n\n\n\n<li><strong>in accordance with ISO 3046<\/strong><\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">This part is often what makes the verification more a matter of \u201cdocumentation\u201d than of intuition: it is not enough to identify the correct point on the curve; one must also verify that the motor is certified to deliver that power <strong>continuously<\/strong> under the conditions related to the installation altitude, as specified.<\/p>\n\n<h2 id=\"checklist-rapida-di-verifica-coerente-con-i-criteri-citati\" class=\"wp-block-heading\">Quick Verification Checklist (in line with the criteria mentioned)<\/h2>\n\n<p class=\"wp-block-paragraph\">If you need to check the <em>power of a diesel fire pump engine<\/em> in an orderly manner, you can follow this sequence:<\/p>\n\n<ol class=\"wp-block-list\">\n<li>Refer to section <strong>10.1<\/strong> and identify the <strong>points on the power curve<\/strong> to be considered.<\/li>\n\n\n\n<li>For diesel engines, verify that the criterion is consistent with the <strong>NA curve<\/strong> (10% continuous overload capacity, <strong>DIN 6271 \u2013 ISO 3046-1<\/strong>).<\/li>\n\n\n\n<li>If the pump does <strong>not<\/strong> have <strong>an overload protection<\/strong> feature, compare it to the <strong>maximum power at the peak of the curve<\/strong>.<\/li>\n\n\n\n<li>If the pump has <strong>increasing<\/strong> head, compare it to the head when the pump requires <strong>an NPSHr of 16 m<\/strong>.<\/li>\n\n\n\n<li>Confirm that the power can be supplied <strong>continuously at full load<\/strong> and <strong>at the installation altitude<\/strong>, in accordance with <strong>ISO 3046<\/strong>.<\/li>\n<\/ol>\n\n<h2 id=\"conclusione\" class=\"wp-block-heading\">Conclusion<\/h2>\n\n<p class=\"wp-block-paragraph\">UNI EN 12845 guides the selection of motor power based on <strong>the power characteristic curve<\/strong> (section 10.1) and, for diesel engines, requires consistency with the <strong>NA curve<\/strong> (section 10.9.1), distinguishing between pumps without overload (peak of the curve) and pumps with increasing power (a condition linked to NPSHr 16 m). The final requirement is the ability to deliver this power <strong>continuously<\/strong> at full load and at the installation elevation in accordance with <strong>ISO 3046<\/strong>. <\/p>\n","protected":false},"excerpt":{"rendered":"<p>Diesel Engine Power for Fire Pumps: What Specifications Must They Meet According to UNI EN 12845? Let\u2019s look at the points on the power curve to consider and the main scenarios depending on the pump. <\/p>\n","protected":false},"featured_media":7904,"parent":0,"template":"","meta":{"_acf_changed":false,"_angie_page":false,"footnotes":"","_members_access_role":[],"_members_access_error":""},"tags":[634,551,552,554,639,641,637,635,549],"class_list":["post-7902","esperto-risponde","type-esperto-risponde","status-publish","has-post-thumbnail","hentry","tag-diesel-engine","tag-engineering-insights","tag-fire-pumps","tag-fire-safety-regulations","tag-motor-sizing","tag-npshr","tag-power-curve","tag-sprinkler-pump-unit","tag-uni-en-12845"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/esperto-risponde\/7902","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\/7902\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/media\/7904"}],"wp:attachment":[{"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/media?parent=7902"}],"wp:term":[{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/tags?post=7902"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}