{"id":1792,"date":"2026-07-27T10:33:15","date_gmt":"2026-07-27T02:33:15","guid":{"rendered":"https:\/\/jutrion.com\/?page_id=1792"},"modified":"2026-08-07T10:56:20","modified_gmt":"2026-08-07T02:56:20","slug":"calculadora-de-caja-combinadora-fotovoltaica","status":"publish","type":"page","link":"https:\/\/jutrion.com\/es\/tools\/pv-combiner-box-calculator\/","title":{"rendered":"PV Combiner Box Rating Calculator"},"content":{"rendered":"\n<!-- ===== JUTRION PV Combiner Box Rating Calculator \u2014 paste into a WordPress \"Custom HTML\" block ===== -->\n<div class=\"jt-calc\">\n  <p class=\"eyebrow\">Solar &amp; DC<\/p>\n  <h1>PV Combiner Box Rating Calculator<\/h1>\n  <p class=\"tool-lede\">Aggregate the string currents and voltage into the reference ratings a PV array combiner box needs: the per-string input fuse, the combined output current, the output disconnector or breaker, the busbar, and the SPD operating voltage. A system-level starting point \u2014 ratings still depend on enclosure temperature and the device datasheets.<\/p>\n\n  <div class=\"jt-card\"><div class=\"jt-grid\">\n    <div class=\"jt-inputs\">\n      <div class=\"jt-two\">\n        <div class=\"jt-field\"><label for=\"jt-n\">Number of strings<\/label><input type=\"number\" id=\"jt-n\" value=\"8\" min=\"1\" step=\"1\" inputmode=\"numeric\"><\/div>\n        <div class=\"jt-field\"><label for=\"jt-isc\">String I<sub>sc<\/sub> (A)<\/label><input type=\"number\" id=\"jt-isc\" value=\"13.8\" min=\"0.1\" step=\"0.1\" inputmode=\"decimal\"><\/div>\n      <\/div>\n      <div class=\"jt-field\"><label for=\"jt-voc\">String cold V<sub>oc<\/sub> (V)<\/label><input type=\"number\" id=\"jt-voc\" value=\"1000\" min=\"1\" step=\"10\" inputmode=\"numeric\"><\/div>\n      <div class=\"jt-note\"><span>\u24d8<\/span><span>Enter the cold-temperature string V<sub>oc<\/sub> (from the string-voltage calculator), not the STC value \u2014 it sets the voltage rating for every DC device in the box.<\/span><\/div>\n    <\/div>\n    <div class=\"jt-readout\">\n      <div><div class=\"jt-rl\">Combined output current<\/div><div class=\"jt-big\"><span id=\"jt-out\">\u2014<\/span> <span>A<\/span><\/div><\/div>\n      <div class=\"jt-rec row\"><div class=\"k\">Input fuse per string<\/div><div class=\"v\" id=\"jt-fuse\">\u2014<\/div><\/div>\n      <div class=\"jt-rec row\"><div class=\"k\">Output disconnector \/ breaker<\/div><div class=\"v\" id=\"jt-dev\">\u2014<\/div><\/div>\n      <div class=\"jt-rec row\"><div class=\"k\">Busbar &amp; device U<sub>e<\/sub><\/div><div class=\"v\" id=\"jt-ue\">\u2014<\/div><\/div>\n      <div class=\"jt-rec row\"><div class=\"k\">SPD U<sub>cpv<\/sub><\/div><div class=\"v\" id=\"jt-spd\">\u2014<\/div><\/div>\n      <button type=\"button\" class=\"jt-copy\" id=\"jt-copy\">Copy result<\/button>\n    <\/div>\n  <\/div><\/div>\n\n  <div class=\"jt-content\">\n    <h2>What the box has to rate for<\/h2>\n    <div class=\"jt-eq\">Output current = N \u00d7 I<sub>sc<\/sub> \u00d7 1.25\nInput fuse (each string) : 1.5 \u00d7 I<sub>sc<\/sub> \u2264 In \u2264 module max series fuse\nVoltage rating U<sub>e<\/sub> \u2265 string cold V<sub>oc<\/sub>\nSPD U<sub>cpv<\/sub> \u2265 1.1 \u00d7 string cold V<sub>oc<\/sub><\/div>\n    <p>Every string feeds the common busbar, so the output current is the sum of all string currents with the 1.25 continuous-duty factor. The output disconnector, breaker, busbar, and cable are sized to that current, while every DC component \u2014 fuses, isolator, SPD, busbar clearances \u2014 must be rated for the cold-temperature string voltage.<\/p>\n\n    <h2>The building blocks<\/h2>\n    <ul>\n      <li><b>Input string fuses<\/b> \u2014 one gPV fuse per string (per polarity as required) once enough strings are combined to drive a damaging reverse current.<\/li>\n      <li><b>Output disconnector or DC breaker<\/b> \u2014 isolates and protects the combined output; rated for the output current and the string voltage.<\/li>\n      <li><b>Busbar<\/b> \u2014 carries the summed current continuously at the enclosure temperature.<\/li>\n      <li><b>Type 1 or 2 SPD<\/b> \u2014 protects the array and the downstream inverter; U<sub>cpv<\/sub> set above the cold string voltage.<\/li>\n    <\/ul>\n    <div class=\"jt-note\"><span>\u26a0<\/span><span><b>Enclosure temperature derates the ratings.<\/b> A combiner box in full sun runs hot inside, reducing device and busbar capacity. Apply the manufacturer&#8217;s temperature derating to the current ratings before finalising.<\/span><\/div>\n\n    <h2>Frequently asked questions<\/h2>\n    <div class=\"jt-faq\">\n      <details><summary>Why the 1.25 factor on the output?<\/summary><p>PV is a continuous source and can exceed its STC current under high irradiance. The 1.25 factor sizes the busbar and output device for sustained duty above the nominal string current.<\/p><\/details>\n      <details><summary>Does every string need an input fuse?<\/summary><p>Only when the number of parallel strings is large enough that the reverse current from healthy strings could exceed a faulted module&#8217;s withstand \u2014 commonly three or more strings. Below that, string fuses may be omitted per IEC 62548.<\/p><\/details>\n      <details><summary>Type 1 or Type 2 SPD in the box?<\/summary><p>Type 2 is usual for array and inverter protection. Where the site has an external lightning protection system or high exposure, a Type 1 (or Type 1+2) is used. The U<sub>cpv<\/sub> requirement is the same in both cases.<\/p><\/details>\n    <\/div>\n\n    <div class=\"jt-cta\">\n      <h2>Build the combiner box<\/h2>\n      <p>Match the fuses, disconnector, busbar, and SPD to a combiner box rated for the array voltage and current.<\/p>\n      <div class=\"jt-cta-btns\">\n        <a class=\"jt-btn\" href=\"https:\/\/jutrion.com\/pv-combiner-box\/\">Explore PV combiner boxes<\/a>\n        <a class=\"jt-btn ghost\" href=\"https:\/\/jutrion.com\/contact\/\">Get a free quote<\/a>\n      <\/div>\n      <p class=\"jt-related\">Related products: <a href=\"https:\/\/jutrion.com\/pv-combiner-box\/\">PV combiner box<\/a> \u00b7 <a href=\"https:\/\/jutrion.com\/fuse\/\">Fuse<\/a> \u00b7 <a href=\"https:\/\/jutrion.com\/spd\/\">SPD<\/a><\/p>\n    <\/div>\n\n    <div class=\"jt-std\"><strong>Standards referenced<\/strong>IEC 60364-7-712 (PV systems) \u00b7 IEC 62548 (PV array design) \u00b7 IEC 61439-2 (assemblies) \u00b7 IEC 61643-31 (PV SPD).<\/div>\n    <p class=\"jt-fine\">System-level estimate for guidance only. Final combiner-box ratings must account for enclosure temperature, device datasheets, and the array topology, verified by a qualified person.<\/p>\n  <\/div>\n<\/div>\n\n<script>\n(function(){\n  var $=function(id){return document.getElementById(id);};\n  var n=$('jt-n'),isc=$('jt-isc'),voc=$('jt-voc'),\n      outEl=$('jt-out'),fuseEl=$('jt-fuse'),devEl=$('jt-dev'),ueEl=$('jt-ue'),spdEl=$('jt-spd');\n  var GPV=[1,2,3,4,5,6,8,10,12,15,16,20,25,30,32,40,50],\n      DEV=[16,20,25,32,40,50,63,80,100,125,160,200,250,320,400,500,630,800];\n  function nextIn(arr,x){for(var k=0;k<arr.length;k++){if(arr[k]>=x)return arr[k];}return null;}\n  function calc(){\n    var N=parseInt(n.value,10),I=parseFloat(isc.value),V=parseFloat(voc.value);\n    if(!(N>0&&I>0)){outEl.textContent='\u2014';fuseEl.textContent=devEl.textContent=ueEl.textContent=spdEl.textContent='\u2014';return;}\n    var out=N*I*1.25;\n    outEl.textContent=out.toFixed(1);\n    var f=nextIn(GPV,1.5*I);fuseEl.textContent=f?(f+' A gPV'):'special';\n    var d=nextIn(DEV,out);devEl.textContent=d?(d+' A'):'> 800 A';\n    ueEl.textContent=(V>0)?('\u2265 '+V+' V DC'):'\u2014';\n    spdEl.textContent=(V>0)?('\u2265 '+Math.ceil(V*1.1)+' V'):'\u2014';\n  }\n  [n,isc,voc].forEach(function(el){el.addEventListener('input',calc);el.addEventListener('change',calc);});\n  $('jt-copy').addEventListener('click',function(){var b=$('jt-copy');var txt='Strings: '+n.value+' \u00d7 '+isc.value+' A, string cold Voc '+voc.value+' V\\nOutput current: '+outEl.textContent+' A\\nInput fuse\/string: '+fuseEl.textContent+'\\nOutput device: '+devEl.textContent+'\\nVoltage rating Ue: '+ueEl.textContent+'\\nSPD Ucpv: '+spdEl.textContent;navigator.clipboard.writeText(txt).then(function(){var o=b.textContent;b.textContent='Copied \u2713';setTimeout(function(){b.textContent=o;},1500);}).catch(function(){b.textContent='Press Ctrl+C';});});\n  calc();\n})();\n<\/script>\n<!-- ===== end block ===== -->\n\n","protected":false},"excerpt":{"rendered":"<p>Solar &amp; DC PV Combiner Box Rating Calculator Aggregate the string currents and voltage into the reference ratings a PV array combiner box needs: the per-string input fuse, the combined output current, the output disconnector or breaker, the busbar, and the SPD operating voltage. A system-level starting point \u2014 ratings still depend on enclosure temperature [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1778,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1792","page","type-page","status-publish","hentry"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/jutrion.com\/es\/wp-json\/wp\/v2\/pages\/1792","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jutrion.com\/es\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/jutrion.com\/es\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/jutrion.com\/es\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jutrion.com\/es\/wp-json\/wp\/v2\/comments?post=1792"}],"version-history":[{"count":1,"href":"https:\/\/jutrion.com\/es\/wp-json\/wp\/v2\/pages\/1792\/revisions"}],"predecessor-version":[{"id":1793,"href":"https:\/\/jutrion.com\/es\/wp-json\/wp\/v2\/pages\/1792\/revisions\/1793"}],"up":[{"embeddable":true,"href":"https:\/\/jutrion.com\/es\/wp-json\/wp\/v2\/pages\/1778"}],"wp:attachment":[{"href":"https:\/\/jutrion.com\/es\/wp-json\/wp\/v2\/media?parent=1792"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}