{"id":100057,"date":"2026-02-15T20:09:42","date_gmt":"2026-02-15T20:09:42","guid":{"rendered":"https:\/\/vibromera.eu\/?post_type=calculator&#038;p=100057"},"modified":"2026-07-11T23:16:52","modified_gmt":"2026-07-11T23:16:52","slug":"circuit-breaker-selection","status":"publish","type":"calculator","link":"https:\/\/vibromera.eu\/hr\/calculators\/circuit-breaker-selection\/","title":{"rendered":"Circuit-Breaker Preliminary Checks | No Device Selection"},"content":{"rendered":"\r\n<script type=\"application\/ld+json\">{\"@context\":\"https:\/\/schema.org\",\"@type\":\"WebApplication\",\"name\":\"Circuit-Breaker Preliminary Input Checks\",\"description\":\"Evaluate three explicit overload and short-circuit inequalities for a user-selected protective device without recommending a rating, trip curve, breaker type or selectivity.\",\"url\":\"https:\/\/vibromera.eu\/calculators\/circuit-breaker-selection\/\",\"applicationCategory\":\"Engineering Calculator\",\"operatingSystem\":\"Any\",\"offers\":{\"@type\":\"Offer\",\"price\":\"0\",\"priceCurrency\":\"EUR\"},\"creator\":{\"@type\":\"Organization\",\"name\":\"Vibromera\",\"url\":\"https:\/\/vibromera.eu\/\"},\"dateModified\":\"2026-07-12\",\"inLanguage\":\"en\",\"isAccessibleForFree\":true}<\/script>\r\n<script type=\"application\/ld+json\">{\"@context\":\"https:\/\/schema.org\",\"@type\":\"FAQPage\",\"mainEntity\":[{\"@type\":\"Question\",\"name\":\"Does this calculator select a circuit breaker?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"No. It only evaluates three supplied-value inequalities. Product standard, voltage, poles, trip characteristics, fault protection, coordination and national installation rules still require competent design.\"}},{\"@type\":\"Question\",\"name\":\"Does passing the breaking-capacity comparison prove short-circuit protection?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"No. Minimum fault current and disconnection, conductor thermal withstand, current limitation, backup protection, voltage and device configuration also have to be verified.\"}},{\"@type\":\"Question\",\"name\":\"Can load type automatically determine a B, C or D curve?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"No. Starting\/inrush profiles and fault-loop conditions must be compared with the exact device time-current data and applicable disconnection requirements.\"}}]}<\/script>\r\n<script 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li{margin-bottom:3px}\r\n.vc-related{display:flex;flex-wrap:wrap;gap:10px;margin-top:16px}.vc-related-link{display:inline-block;padding:8px 16px;font-family:var(--vc-font);font-size:13px;font-weight:600;background:var(--vc-surface-alt);color:var(--vc-ink-secondary);border:1px solid var(--vc-border);border-radius:var(--vc-radius);text-decoration:none;transition:all .15s}.vc-related-link:hover{border-color:var(--vc-accent);color:var(--vc-accent);background:var(--vc-accent-light)}\r\n.vc-promo{margin-top:24px;padding:20px;background:linear-gradient(135deg,var(--vc-accent-light),var(--vc-surface));border:1px solid var(--vc-border);border-radius:var(--vc-radius-lg);display:flex;align-items:center;gap:16px}.vc-promo-text{flex:1;font-size:14px;color:var(--vc-ink-secondary)}.vc-promo-text strong{color:var(--vc-ink)}.vc-promo-link{padding:8px 20px;font-size:13px;font-weight:700;color:#fff;background:var(--vc-accent);border-radius:var(--vc-radius);text-decoration:none;white-space:nowrap;transition:background .15s}.vc-promo-link:hover{background:var(--vc-accent-hover)}\r\n.vc-footer{text-align:center;padding:32px 16px;font-size:13px;color:var(--vc-ink-muted)}.vc-footer a{color:var(--vc-accent);text-decoration:none}.vc-footer a:hover{text-decoration:underline}.vc-footer-links{margin-top:8px;font-size:12px}.vc-footer-links a{margin:0 8px}\r\n@media print{.vc-section-body{max-height:none!important}.vc-faq-a{max-height:none!important}.vc-results{max-height:none!important;padding:24px!important}.vc-copy-btn,.vc-section-chevron,.vc-faq-chevron,.vc-presets,.vc-promo{display:none!important}}\r\n<\/style>\r\n<div class=\"vc-calculator\" id=\"vc-breaker-checks\"><header class=\"vc-header\"><p class=\"vc-header-eyebrow\">Supplied-value arithmetic only<\/p><h1 class=\"vc-header-title\">Circuit-Breaker Preliminary Input Checks<\/h1><p class=\"vc-header-subtitle\">Check three basic inequalities for an already selected overcurrent protective device. This page does not choose a rating, MCB\/MCCB type, B\/C\/D curve, trip settings, breaking category or selectivity.<\/p><div class=\"vc-badges\"><span class=\"vc-badge\">No automatic defaults<\/span><span class=\"vc-badge\">No device selection<\/span><span class=\"vc-badge\">IEC scopes stated<\/span><\/div><\/header>\r\n<div class=\"vc-card\"><form class=\"vc-form\" id=\"vc-form\" autocomplete=\"off\"><div class=\"vc-form-grid\"><div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-ib\">Design current I<sub>B<\/sub> <span class=\"vc-label-hint\">(A)<\/span><\/label><input class=\"vc-input\" type=\"text\" id=\"vc-ib\" inputmode=\"decimal\"><\/div><div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-in\">Selected rated\/setting current I<sub>n<\/sub> or I<sub>r<\/sub> <span class=\"vc-label-hint\">(A)<\/span><\/label><input class=\"vc-input\" type=\"text\" id=\"vc-in\" inputmode=\"decimal\"><\/div><div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-iz\">Corrected conductor current capacity I<sub>z<\/sub> <span class=\"vc-label-hint\">(A)<\/span><\/label><input class=\"vc-input\" type=\"text\" id=\"vc-iz\" inputmode=\"decimal\"><\/div><div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-i2\">Declared conventional operating current I\u2082 <span class=\"vc-label-hint\">(A)<\/span><\/label><input class=\"vc-input\" type=\"text\" id=\"vc-i2\" inputmode=\"decimal\"><\/div><div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-ik\">Maximum prospective short-circuit current I<sub>k,max<\/sub> <span class=\"vc-label-hint\">(kA at device location)<\/span><\/label><input class=\"vc-input\" type=\"text\" id=\"vc-ik\" inputmode=\"decimal\"><\/div><div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-break\">Applicable declared breaking capacity <span class=\"vc-label-hint\">(kA at actual voltage\/configuration)<\/span><\/label><input class=\"vc-input\" type=\"text\" id=\"vc-break\" inputmode=\"decimal\"><\/div><div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-basis\">Device-data basis<\/label><select class=\"vc-select\" id=\"vc-basis\"><option value=\"iec60898\">IEC 60898-1 device data<\/option><option value=\"iec60947\">IEC 60947-2 device data<\/option><option value=\"other\">Other applicable product data<\/option><\/select><\/div><\/div><p id=\"vc-error\" role=\"alert\" style=\"margin:.75rem 0 0;color:#b42318\"><\/p><div class=\"vc-warning-box\"><p style=\"margin:0\"><strong>Input provenance required:<\/strong> I<sub>z<\/sub> must already include the actual installation method, ambient\/grouping, conductor, insulation and harmonic corrections. I\u2082 and breaking capacity must come from the exact device data at the actual voltage, AC\/DC and pole\/configuration conditions. Do not substitute guessed defaults.<\/p><\/div><\/form>\r\n<div class=\"vc-results\" id=\"vc-results\"><div class=\"vc-results-head\"><h2 class=\"vc-results-title\">Three preliminary comparisons<\/h2><button type=\"button\" class=\"vc-copy-btn\" id=\"vc-copy-btn\">Copy<\/button><\/div><div class=\"vc-result-grid\"><div class=\"vc-rcard vc-rcard-primary\"><div class=\"vc-rcard-label\">Load \/ device \/ conductor<\/div><div class=\"vc-rcard-value\" id=\"vc-r-chain\">\u2014<\/div><\/div><div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Conventional overload operation<\/div><div class=\"vc-rcard-value\" id=\"vc-r-overload\">\u2014<\/div><\/div><div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Breaking-capacity comparison<\/div><div class=\"vc-rcard-value\" id=\"vc-r-breaking\">\u2014<\/div><\/div><\/div><p id=\"vc-r-summary\" style=\"margin:0;color:var(--vc-ink-secondary)\"><\/p><\/div><\/div>\r\n<div class=\"vc-section vc-open\"><button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"true\"><span class=\"vc-section-toggle-text\"><span class=\"vc-section-icon\">\ud83d\udcd8<\/span><span class=\"vc-section-title\">Equations, editions and missing checks<\/span><\/span><\/button><div class=\"vc-section-body\"><div class=\"vc-section-inner vc-theory\"><h3>Arithmetic evaluated<\/h3><div class=\"vc-formula-box\">I<sub>B<\/sub> \u2264 I<sub>n\/r<\/sub> \u2264 I<sub>z<\/sub>; &nbsp; I\u2082 \u2264 1.45I<sub>z<\/sub>; &nbsp; applicable breaking capacity \u2265 I<sub>k,max<\/sub><\/div><p>The public <a href=\"https:\/\/www.electrical-installation.org\/enwiki\/Practical_values_for_a_protective_scheme\" target=\"_blank\" rel=\"noopener\">Schneider Electrical Installation Guide<\/a> explains these IEC-based overload and breaking-capacity comparisons and also notes the special tested backup\/cascading case. This page requires every quantity explicitly and only reports whether the numerical inequalities hold.<\/p><h3>Current IEC product and installation scopes<\/h3><p><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/28432\" target=\"_blank\" rel=\"noopener\">IEC 60364-4-43:2023<\/a> is the current fourth edition for protection against overcurrent and coordination of overcurrent-protection measures. <a href=\"https:\/\/webstore.iec.ch\/en\/publication\/21972\" target=\"_blank\" rel=\"noopener\">IEC 60898-1:2015 with Amendment 1:2019 and Corrigendum 1:2020<\/a> applies to specified a.c. circuit-breakers for household and similar installations up to 440 V, 125 A and 25 kA. <a href=\"https:\/\/webstore.iec.ch\/en\/publication\/66277\" target=\"_blank\" rel=\"noopener\">IEC 60947-2:2024<\/a>, sixth edition, applies to low-voltage circuit-breakers intended for instructed or skilled persons within its voltage scope. These standards use different product contexts and short-circuit ratings; a current threshold alone cannot choose between them.<\/p><h3>What is not checked<\/h3><div class=\"vc-warning-box\"><p style=\"margin:0\"><strong>Passing all three boxes is not approval.<\/strong> Still verify system voltage\/frequency and AC\/DC duty, poles and neutral, maximum and minimum fault currents, automatic-disconnection time and earth-fault loop, conductor short-circuit thermal withstand and energy limitation, protective conductor and RCD\/additional protection, inrush\/start and nuisance tripping, adjustable settings, ambient\/installation derating, isolation, coordination\/selectivity\/backup using tested manufacturer data, upstream\/downstream equipment, local law and inspection\/testing.<\/p><\/div><p>B\/C\/D letters are not selected from a load name. The exact starting-current envelope and required fault\/disconnection performance must be checked against the selected device time-current bands. Likewise, selectivity cannot be established by a universal current ratio; use verified manufacturer tables\/curves or a validated coordination study.<\/p><h3>Checked example<\/h3><div class=\"vc-example-box\"><p style=\"margin:0\">I<sub>B<\/sub>=28 A, I<sub>n<\/sub>=32 A, I<sub>z<\/sub>=41 A, I\u2082=46.4 A, I<sub>k,max<\/sub>=10 kA and applicable breaking capacity=15 kA pass all three numerical comparisons; the missing checks above still remain.<\/p><\/div><\/div><\/div><\/div>\r\n<div class=\"vc-section\"><button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\"><span class=\"vc-section-toggle-text\"><span class=\"vc-section-icon\">\u2753<\/span><span class=\"vc-section-title\">Frequently Asked Questions<\/span><\/span><\/button><div class=\"vc-section-body\"><div class=\"vc-section-inner\"><div class=\"vc-faq-list\" id=\"vc-faq-list\"><\/div><\/div><\/div><\/div><footer class=\"vc-footer\"><p>\u00a9 2024\u20132026 <a href=\"https:\/\/vibromera.eu\/\">Vibromera<\/a><\/p><p>Three preliminary inequalities only; competent electrical design and verification required. Scientific review: July 2026.<\/p><\/footer><\/div>\r\n<script>(function(){'use strict';function $(i){return document.getElementById(i)}function pos(raw){var s=String(raw).trim().replace(\/\\s+\/g,'');if(!\/^[+]?(?:\\d+(?:[.,]\\d*)?|[.,]\\d+)$\/.test(s))return NaN;var n=Number(s.replace(',','.'));return Number.isFinite(n)&&n>0?n:NaN}function f(n){return n.toFixed(9).replace(\/(\\.\\d*?)0+$\/,'$1').replace(\/\\.$\/,'')}function mark(ok,text){return '<span style=\"color:'+(ok?'var(--vc-green)':'var(--vc-red)')+'\">'+(ok?'PASS':'FAIL')+'<\/span><br><span class=\"vc-rcard-unit\">'+text+'<\/span>'}function calc(){var ib=pos($('vc-ib').value),inn=pos($('vc-in').value),iz=pos($('vc-iz').value),i2=pos($('vc-i2').value),ik=pos($('vc-ik').value),br=pos($('vc-break').value);if(![ib,inn,iz,i2,ik,br].every(Number.isFinite)){$('vc-error').textContent=[$('vc-ib').value,$('vc-in').value,$('vc-iz').value,$('vc-i2').value,$('vc-ik').value,$('vc-break').value].some(function(x){return x.trim()})?'Enter every required quantity as a positive finite number. 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')+'This is not a selection, coordination, disconnection or safety verdict.';$('vc-results').classList.add('vc-visible');var u=new URL(location),v={design_current_a:ib,selected_current_a:inn,corrected_conductor_capacity_a:iz,conventional_operating_current_a:i2,max_prospective_short_circuit_ka:ik,applicable_breaking_capacity_ka:br,device_data_basis:$('vc-basis').value};Object.keys(v).forEach(function(k){u.searchParams.set(k,v[k])});history.replaceState(null,'',u.toString())}$('vc-form').addEventListener('input',calc);$('vc-form').addEventListener('change',calc);$('vc-copy-btn').addEventListener('click',function(){if(navigator.clipboard)navigator.clipboard.writeText($('vc-results').innerText)});document.querySelectorAll('.vc-section-toggle').forEach(function(b){b.addEventListener('click',function(){var s=this.closest('.vc-section');s.classList.toggle('vc-open');this.setAttribute('aria-expanded',s.classList.contains('vc-open'))})});var q=[['Does PASS mean the breaker is safe and compliant?','No. It means only that the three supplied numerical inequalities hold; all listed electrical, product, installation and legal checks remain.'],['Can load type choose B, C or D automatically?','No. Compare measured or specified inrush and fault-loop conditions with exact device curves and disconnection requirements.'],['Can a current ratio prove selectivity?','No. Use tested manufacturer selectivity\/backup tables or a validated coordination study for the exact devices and settings.']];var l=$('vc-faq-list');q.forEach(function(v){l.innerHTML+='<div class=\"vc-faq-item\"><button type=\"button\" class=\"vc-faq-q\">'+v[0]+'<\/button><div class=\"vc-faq-a\"><div class=\"vc-faq-a-inner\"><p>'+v[1]+'<\/p><\/div><\/div><\/div>'});l.addEventListener('click',function(e){var b=e.target.closest('.vc-faq-q');if(b)b.closest('.vc-faq-item').classList.toggle('vc-open')});var z=new URLSearchParams(location.search),map={design_current_a:'vc-ib',selected_current_a:'vc-in',corrected_conductor_capacity_a:'vc-iz',conventional_operating_current_a:'vc-i2',max_prospective_short_circuit_ka:'vc-ik',applicable_breaking_capacity_ka:'vc-break',device_data_basis:'vc-basis'};Object.keys(map).forEach(function(k){if(z.has(k))$(map[k]).value=z.get(k)});calc()})();<\/script>\r\n","protected":false},"excerpt":{"rendered":"<p>Evaluate three explicit overload and breaking-capacity inequalities for a user-selected device; no MCB\/MCCB rating, curve, selectivity or safety verdict.<\/p>","protected":false},"featured_media":0,"template":"","meta":{"ai_generated_summary":"","footnotes":""},"categories":[],"tags":[],"class_list":["post-100057","calculator","type-calculator","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/hr\/wp-json\/wp\/v2\/calculator\/100057","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/hr\/wp-json\/wp\/v2\/calculator"}],"about":[{"href":"https:\/\/vibromera.eu\/hr\/wp-json\/wp\/v2\/types\/calculator"}],"version-history":[{"count":2,"href":"https:\/\/vibromera.eu\/hr\/wp-json\/wp\/v2\/calculator\/100057\/revisions"}],"predecessor-version":[{"id":102347,"href":"https:\/\/vibromera.eu\/hr\/wp-json\/wp\/v2\/calculator\/100057\/revisions\/102347"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/hr\/wp-json\/wp\/v2\/media?parent=100057"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/hr\/wp-json\/wp\/v2\/categories?post=100057"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/hr\/wp-json\/wp\/v2\/tags?post=100057"}],"curies":[{"name":"radni list","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}