{"id":30642,"date":"2026-07-30T15:48:40","date_gmt":"2026-07-30T07:48:40","guid":{"rendered":"https:\/\/www.cnspd.com\/?p=30642"},"modified":"2026-07-30T15:48:40","modified_gmt":"2026-07-30T07:48:40","slug":"ac-spd-for-main-distribution-board-selection-guide","status":"publish","type":"post","link":"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/","title":{"rendered":"AC SPD for Main Distribution Board Selection Guide"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"30642\" class=\"elementor elementor-30642\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-e468232 e-flex e-con-boxed e-con e-parent\" data-id=\"e468232\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-b9d8934 elementor-widget elementor-widget-html\" data-id=\"b9d8934\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"html.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<style>\r\n#leeyee-mdb-ac-spd-guide {\r\n  --leeyee-blue: #004898;\r\n  --leeyee-blue-dark: #00356f;\r\n  --leeyee-blue-light: #eef5ff;\r\n  --leeyee-blue-lighter: #f7fbff;\r\n  --leeyee-text: #26323d;\r\n  --leeyee-heading: #15212c;\r\n  --leeyee-muted: #617080;\r\n  --leeyee-border: #d8e2eb;\r\n  --leeyee-warning: #a65d00;\r\n  --leeyee-warning-bg: #fff8ed;\r\n  width: 100%;\r\n  max-width: 860px;\r\n  margin: 0 auto;\r\n  color: var(--leeyee-text);\r\n  font-family: Arial, Helvetica, sans-serif;\r\n  font-size: 17px;\r\n  line-height: 1.72;\r\n  text-rendering: optimizeLegibility;\r\n  overflow-wrap: normal;\r\n  word-break: normal;\r\n  hyphens: none;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide,\r\n#leeyee-mdb-ac-spd-guide * {\r\n  box-sizing: border-box;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide p {\r\n  margin: 0 0 18px;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide strong {\r\n  color: var(--leeyee-heading);\r\n  font-weight: 700;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide a {\r\n  color: var(--leeyee-blue);\r\n  text-decoration: underline;\r\n  text-underline-offset: 3px;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide a:hover,\r\n#leeyee-mdb-ac-spd-guide a:focus {\r\n  color: var(--leeyee-blue-dark);\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide h2 {\r\n  margin: 52px 0 20px;\r\n  color: var(--leeyee-heading);\r\n  font-size: clamp(28px, 3.4vw, 34px);\r\n  line-height: 1.28;\r\n  letter-spacing: -0.02em;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide h3 {\r\n  margin: 34px 0 14px;\r\n  color: var(--leeyee-blue);\r\n  font-size: clamp(22px, 2.7vw, 26px);\r\n  line-height: 1.35;\r\n  letter-spacing: -0.01em;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide h4 {\r\n  margin: 25px 0 10px;\r\n  color: var(--leeyee-heading);\r\n  font-size: 19px;\r\n  line-height: 1.4;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide ul,\r\n#leeyee-mdb-ac-spd-guide ol {\r\n  margin: 0 0 22px;\r\n  padding-left: 25px;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide li {\r\n  margin: 0 0 9px;\r\n  padding-left: 3px;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-intro {\r\n  margin-bottom: 24px;\r\n  font-size: 18px;\r\n  line-height: 1.7;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-quick-answer,\r\n#leeyee-mdb-ac-spd-guide .mdb-note,\r\n#leeyee-mdb-ac-spd-guide .mdb-warning,\r\n#leeyee-mdb-ac-spd-guide .mdb-checklist,\r\n#leeyee-mdb-ac-spd-guide .mdb-cta {\r\n  margin: 28px 0;\r\n  padding: 24px 26px;\r\n  border: 1px solid var(--leeyee-border);\r\n  border-left: 5px solid var(--leeyee-blue);\r\n  border-radius: 10px;\r\n  background: var(--leeyee-blue-lighter);\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-warning {\r\n  border-color: #f1d7ad;\r\n  border-left-color: var(--leeyee-warning);\r\n  background: var(--leeyee-warning-bg);\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-quick-answer h2,\r\n#leeyee-mdb-ac-spd-guide .mdb-note h3,\r\n#leeyee-mdb-ac-spd-guide .mdb-warning h3,\r\n#leeyee-mdb-ac-spd-guide .mdb-checklist h3,\r\n#leeyee-mdb-ac-spd-guide .mdb-cta h2 {\r\n  margin-top: 0;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-quick-answer h2 {\r\n  margin-bottom: 14px;\r\n  color: var(--leeyee-blue);\r\n  font-size: 25px;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-answer-line {\r\n  margin: 0 0 14px;\r\n  color: var(--leeyee-heading);\r\n  font-size: 18px;\r\n  line-height: 1.62;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-small {\r\n  color: var(--leeyee-muted);\r\n  font-size: 14px;\r\n  line-height: 1.6;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-key-point {\r\n  margin: 22px 0;\r\n  padding: 18px 20px;\r\n  border-left: 4px solid var(--leeyee-blue);\r\n  background: var(--leeyee-blue-light);\r\n  color: var(--leeyee-heading);\r\n  font-weight: 700;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-meaning {\r\n  margin: 17px 0 22px;\r\n  padding: 15px 18px;\r\n  border-radius: 8px;\r\n  background: #f3f7fa;\r\n  color: #344554;\r\n  font-size: 15px;\r\n  line-height: 1.65;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-meaning strong {\r\n  color: var(--leeyee-blue);\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide figure {\r\n  width: 100%;\r\n  margin: 34px 0 38px;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide figure img {\r\n  display: block;\r\n  width: 100%;\r\n  max-width: 100%;\r\n  height: auto;\r\n  margin: 0;\r\n  border: 1px solid #e0e8ef;\r\n  border-radius: 10px;\r\n  background: #fff;\r\n  box-shadow: 0 8px 24px rgba(26, 55, 82, 0.07);\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide figcaption {\r\n  margin-top: 11px;\r\n  color: var(--leeyee-muted);\r\n  font-size: 14px;\r\n  line-height: 1.55;\r\n  text-align: left;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-table-wrap {\r\n  width: 100%;\r\n  margin: 24px 0 30px;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide table {\r\n  width: 100%;\r\n  border-collapse: separate;\r\n  border-spacing: 0;\r\n  table-layout: fixed;\r\n  border: 1px solid var(--leeyee-border);\r\n  border-radius: 9px;\r\n  background: #fff;\r\n  font-size: 15px;\r\n  line-height: 1.55;\r\n  overflow: hidden;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide thead th {\r\n  padding: 14px 15px;\r\n  border-right: 1px solid rgba(255, 255, 255, 0.2);\r\n  background: var(--leeyee-blue);\r\n  color: #fff;\r\n  font-weight: 700;\r\n  text-align: left;\r\n  vertical-align: top;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide thead th:last-child {\r\n  border-right: 0;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide tbody td {\r\n  padding: 14px 15px;\r\n  border-top: 1px solid var(--leeyee-border);\r\n  border-right: 1px solid var(--leeyee-border);\r\n  color: var(--leeyee-text);\r\n  vertical-align: top;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide tbody tr:first-child td {\r\n  border-top: 0;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide tbody td:last-child {\r\n  border-right: 0;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide tbody tr:nth-child(even) td {\r\n  background: #f8fafc;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-table-note {\r\n  margin: -17px 0 28px;\r\n  color: var(--leeyee-muted);\r\n  font-size: 14px;\r\n  line-height: 1.55;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-steps {\r\n  margin: 25px 0 30px;\r\n  padding: 0;\r\n  list-style: none;\r\n  counter-reset: mdb-step;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-steps li {\r\n  position: relative;\r\n  margin: 0 0 17px;\r\n  padding: 19px 20px 19px 64px;\r\n  border: 1px solid var(--leeyee-border);\r\n  border-radius: 9px;\r\n  background: #fff;\r\n  counter-increment: mdb-step;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-steps li::before {\r\n  position: absolute;\r\n  top: 18px;\r\n  left: 18px;\r\n  display: flex;\r\n  width: 30px;\r\n  height: 30px;\r\n  align-items: center;\r\n  justify-content: center;\r\n  border-radius: 50%;\r\n  background: var(--leeyee-blue);\r\n  color: #fff;\r\n  content: counter(mdb-step);\r\n  font-size: 14px;\r\n  font-weight: 700;\r\n  line-height: 1;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-steps strong {\r\n  display: block;\r\n  margin-bottom: 4px;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-scenario {\r\n  margin: 22px 0;\r\n  padding: 20px 22px;\r\n  border: 1px solid var(--leeyee-border);\r\n  border-radius: 9px;\r\n  background: #fff;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-scenario h3 {\r\n  margin: 0 0 10px;\r\n  font-size: 21px;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-scenario p:last-child,\r\n#leeyee-mdb-ac-spd-guide .mdb-note p:last-child,\r\n#leeyee-mdb-ac-spd-guide .mdb-warning p:last-child,\r\n#leeyee-mdb-ac-spd-guide .mdb-checklist p:last-child,\r\n#leeyee-mdb-ac-spd-guide .mdb-cta p:last-child {\r\n  margin-bottom: 0;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-check-grid {\r\n  display: grid;\r\n  grid-template-columns: repeat(2, minmax(0, 1fr));\r\n  gap: 12px 24px;\r\n  margin: 18px 0 0;\r\n  padding: 0;\r\n  list-style: none;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-check-grid li {\r\n  position: relative;\r\n  margin: 0;\r\n  padding: 0 0 0 25px;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-check-grid li::before {\r\n  position: absolute;\r\n  top: 2px;\r\n  left: 0;\r\n  color: var(--leeyee-blue);\r\n  content: \"\u2713\";\r\n  font-weight: 700;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-cta {\r\n  margin-top: 42px;\r\n  padding: 28px;\r\n  background: var(--leeyee-blue-light);\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-cta h2 {\r\n  margin-bottom: 13px;\r\n  font-size: 28px;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .leeyee-site-popup-btn {\r\n  display: inline-flex;\r\n  min-height: 48px;\r\n  margin-top: 8px;\r\n  padding: 12px 22px;\r\n  align-items: center;\r\n  justify-content: center;\r\n  border: 1px solid var(--leeyee-blue);\r\n  border-radius: 7px;\r\n  background: var(--leeyee-blue);\r\n  color: #fff;\r\n  cursor: pointer;\r\n  font: inherit;\r\n  font-size: 16px;\r\n  font-weight: 700;\r\n  line-height: 1.3;\r\n  text-align: center;\r\n  text-decoration: none;\r\n  transition: background-color 0.2s ease, border-color 0.2s ease, transform 0.2s ease;\r\n  -webkit-appearance: none;\r\n  appearance: none;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .leeyee-site-popup-btn:hover,\r\n#leeyee-mdb-ac-spd-guide .leeyee-site-popup-btn:focus {\r\n  border-color: var(--leeyee-blue-dark);\r\n  background: var(--leeyee-blue-dark);\r\n  color: #fff;\r\n  transform: translateY(-1px);\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .leeyee-site-popup-btn .w-btn-label {\r\n  display: block;\r\n  color: inherit;\r\n  white-space: normal;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-faq {\r\n  margin: 22px 0;\r\n  padding-bottom: 21px;\r\n  border-bottom: 1px solid var(--leeyee-border);\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-faq:last-child {\r\n  border-bottom: 0;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-faq h3 {\r\n  margin: 0 0 10px;\r\n  color: var(--leeyee-heading);\r\n  font-size: 21px;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-ref {\r\n  font-size: 12px;\r\n  font-weight: 700;\r\n  line-height: 1;\r\n  text-decoration: none;\r\n  vertical-align: super;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-references {\r\n  margin-top: 26px;\r\n  padding-left: 24px;\r\n  color: #465767;\r\n  font-size: 14px;\r\n  line-height: 1.65;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-references li {\r\n  margin-bottom: 13px;\r\n}\r\n\r\n#leeyee-mdb-ac-spd-guide .mdb-references a {\r\n  overflow-wrap: break-word;\r\n  word-break: normal;\r\n}\r\n\r\n@media (max-width: 1024px) {\r\n  #leeyee-mdb-ac-spd-guide {\r\n    max-width: 820px;\r\n  }\r\n}\r\n\r\n@media (max-width: 820px) {\r\n  #leeyee-mdb-ac-spd-guide {\r\n    padding-right: 20px;\r\n    padding-left: 20px;\r\n  }\r\n}\r\n\r\n@media (max-width: 700px) {\r\n  #leeyee-mdb-ac-spd-guide {\r\n    padding-right: 16px;\r\n    padding-left: 16px;\r\n    font-size: 16px;\r\n    line-height: 1.7;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide .mdb-intro {\r\n    font-size: 17px;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide h2 {\r\n    margin-top: 42px;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide .mdb-quick-answer,\r\n  #leeyee-mdb-ac-spd-guide .mdb-note,\r\n  #leeyee-mdb-ac-spd-guide .mdb-warning,\r\n  #leeyee-mdb-ac-spd-guide .mdb-checklist,\r\n  #leeyee-mdb-ac-spd-guide .mdb-cta {\r\n    padding: 21px 19px;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide .mdb-check-grid {\r\n    grid-template-columns: 1fr;\r\n    gap: 10px;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide table,\r\n  #leeyee-mdb-ac-spd-guide thead,\r\n  #leeyee-mdb-ac-spd-guide tbody,\r\n  #leeyee-mdb-ac-spd-guide tr,\r\n  #leeyee-mdb-ac-spd-guide th,\r\n  #leeyee-mdb-ac-spd-guide td {\r\n    display: block;\r\n    width: 100%;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide table {\r\n    border: 0;\r\n    border-radius: 0;\r\n    background: transparent;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide thead {\r\n    position: absolute;\r\n    width: 1px;\r\n    height: 1px;\r\n    margin: -1px;\r\n    padding: 0;\r\n    overflow: hidden;\r\n    clip: rect(0 0 0 0);\r\n    border: 0;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide tbody tr {\r\n    margin-bottom: 14px;\r\n    overflow: hidden;\r\n    border: 1px solid var(--leeyee-border);\r\n    border-radius: 9px;\r\n    background: #fff;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide tbody td,\r\n  #leeyee-mdb-ac-spd-guide tbody tr:first-child td {\r\n    display: grid;\r\n    grid-template-columns: minmax(112px, 0.8fr) minmax(0, 1.35fr);\r\n    gap: 12px;\r\n    padding: 13px 14px;\r\n    border-top: 1px solid var(--leeyee-border);\r\n    border-right: 0;\r\n    background: #fff;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide tbody td:first-child {\r\n    border-top: 0;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide tbody tr:nth-child(even) td {\r\n    background: #fff;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide tbody td::before {\r\n    color: var(--leeyee-blue);\r\n    content: attr(data-label);\r\n    font-weight: 700;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide .mdb-table-note {\r\n    margin-top: -10px;\r\n  }\r\n}\r\n\r\n@media (max-width: 480px) {\r\n  #leeyee-mdb-ac-spd-guide {\r\n    padding-right: 14px;\r\n    padding-left: 14px;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide .mdb-steps li {\r\n    padding: 18px 17px 18px 55px;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide .mdb-steps li::before {\r\n    left: 14px;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide tbody td,\r\n  #leeyee-mdb-ac-spd-guide tbody tr:first-child td {\r\n    grid-template-columns: 1fr;\r\n    gap: 4px;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide .leeyee-site-popup-btn {\r\n    width: 100%;\r\n  }\r\n}\r\n\r\n@media (max-width: 390px) {\r\n  #leeyee-mdb-ac-spd-guide {\r\n    padding-right: 12px;\r\n    padding-left: 12px;\r\n  }\r\n\r\n  #leeyee-mdb-ac-spd-guide .mdb-quick-answer,\r\n  #leeyee-mdb-ac-spd-guide .mdb-note,\r\n  #leeyee-mdb-ac-spd-guide .mdb-warning,\r\n  #leeyee-mdb-ac-spd-guide .mdb-checklist,\r\n  #leeyee-mdb-ac-spd-guide .mdb-cta,\r\n  #leeyee-mdb-ac-spd-guide .mdb-scenario {\r\n    padding-right: 16px;\r\n    padding-left: 16px;\r\n  }\r\n}\r\n<\/style>\r\n\r\n<article id=\"leeyee-mdb-ac-spd-guide\">\r\n  <p class=\"mdb-intro\">\r\n    Selecting an AC surge protective device for a main distribution board is not simply a matter of choosing the largest kA value. The correct MDB surge protection solution depends on where lightning current may enter, the earthing system, the required protection modes, the operating voltage, the available short-circuit current and the equipment located downstream.\r\n  <\/p>\r\n\r\n  <p>\r\n    This guide is written for distribution-board manufacturers, electrical contractors, consultants, project procurement teams and OEM buyers who need to approve an AC SPD configuration before panel production or site installation.\r\n  <\/p>\r\n\r\n  <section class=\"mdb-quick-answer\" aria-labelledby=\"mdb-quick-answer-title\">\r\n    <div id=\"ez-toc-container\" class=\"ez-toc-v2_0_85 counter-hierarchy ez-toc-counter ez-toc-custom ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#quick-answer\" >Quick Answer<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#why-the-mdb-is-a-critical-surge-protection-point\" >Why the MDB Is a Critical Surge Protection Point<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#mdb-ac-spd-selection-decision-table\" >MDB AC SPD Selection Decision Table<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#how-to-choose-type-1-type-2-or-type-12\" >How to Choose Type 1, Type 2 or Type 1+2<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#how-to-judge-3p-4p-and-3pn-configurations\" >How to Judge 3P, 4P and 3P+N Configurations<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#tt-tn-s-and-tn-c-s-system-differences\" >TT, TN-S and TN-C-S System Differences<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#which-parameters-must-an-mdb-buyer-confirm\" >Which Parameters Must an MDB Buyer Confirm?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#eight-step-selection-workflow-for-an-mdb-project\" >Eight-Step Selection Workflow for an MDB Project<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#three-realistic-mdb-selection-scenarios\" >Three Realistic MDB Selection Scenarios<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#backup-fuse-or-mcb-how-to-confirm-it\" >Backup Fuse or MCB: How to Confirm It<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#installation-position-and-connection-length\" >Installation Position and Connection Length<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#when-is-a-remote-signal-contact-worth-specifying\" >When Is a Remote Signal Contact Worth Specifying?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#what-happens-when-the-wrong-mdb-spd-is-selected\" >What Happens When the Wrong MDB SPD Is Selected?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#oem-and-bulk-order-confirmation\" >OEM and Bulk-Order Confirmation<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#need-an-mdb-spd-configuration-review\" >Need an MDB SPD Configuration Review?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-16\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#frequently-asked-questions\" >Frequently Asked Questions<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-17\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/#references\" >References<\/a><\/li><\/ul><\/nav><\/div>\n<h2 id=\"mdb-quick-answer-title\"><span class=\"ez-toc-section\" id=\"quick-answer\"><\/span>Quick Answer<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <p class=\"mdb-answer-line\">\r\n      <strong>Use a Type 1 SPD at the origin when the installation may carry partial lightning current, such as a building with an external lightning protection system or another confirmed direct-lightning-current exposure condition.<\/strong>\r\n    <\/p>\r\n\r\n    <p class=\"mdb-answer-line\">\r\n      <strong>Use a Type 2 SPD when the MDB requires protection against induced or switching surges but the project assessment does not require Type 1 lightning-current capability.<\/strong>\r\n    <\/p>\r\n\r\n    <p class=\"mdb-answer-line\">\r\n      <strong>Use a tested Type 1+2 SPD when the main board requires both lightning-current and voltage-limiting performance in one coordinated device.<\/strong>\r\n    <\/p>\r\n\r\n    <p>\r\n      After selecting the SPD type, confirm the earthing arrangement, protection modes, Uc, Iimp, In, Imax, Up, temporary overvoltage behaviour, short-circuit capability, backup protection and remote signalling requirement. The final model should be approved from the single-line diagram and the SPD manufacturer's installation data, not from a product label alone.\r\n      <a class=\"mdb-ref\" href=\"#mdb-ref-1\" aria-label=\"Reference 1\">[1]<\/a>\r\n      <a class=\"mdb-ref\" href=\"#mdb-ref-2\" aria-label=\"Reference 2\">[2]<\/a>\r\n      <a class=\"mdb-ref\" href=\"#mdb-ref-3\" aria-label=\"Reference 3\">[3]<\/a>\r\n    <\/p>\r\n  <\/section>\r\n\r\n  <figure>\r\n    <img src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/mdb-ac-spd-protection-architecture.webp\" alt=\"Main distribution board AC SPD protection architecture showing the incoming supply, MDB installation point, earthing path and downstream distribution\" fetchpriority=\"high\" decoding=\"async\">\r\n    <figcaption>\r\n      Typical AC surge protection architecture. The MDB SPD limits surges at the supply origin, while coordinated downstream protection may still be required for remote or sensitive equipment.\r\n    <\/figcaption>\r\n  <\/figure>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"why-the-mdb-is-a-critical-surge-protection-point\"><\/span>Why the MDB Is a Critical Surge Protection Point<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    The main distribution board is normally located at, or close to, the supply origin of the low-voltage installation. A surge entering at this point can be distributed through several outgoing circuits before it reaches control systems, drives, communication equipment and other sensitive loads.\r\n  <\/p>\r\n\r\n  <p>\r\n    Installing an SPD at the MDB creates the first surge-limiting stage. It does not automatically complete the protection design. When downstream equipment is remote, has a lower impulse withstand level or requires a lower residual voltage, additional coordinated Type 2 or Type 3 protection may be necessary.\r\n    <a class=\"mdb-ref\" href=\"#mdb-ref-3\" aria-label=\"Reference 3\">[3]<\/a>\r\n    <a class=\"mdb-ref\" href=\"#mdb-ref-5\" aria-label=\"Reference 5\">[5]<\/a>\r\n  <\/p>\r\n\r\n  <div class=\"mdb-key-point\">\r\n    The MDB decision is therefore not \u201cWhich AC SPD has the highest discharge current?\u201d It is \u201cWhich SPD type, connection arrangement and protection level match this supply origin and its downstream equipment?\u201d\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"mdb-ac-spd-selection-decision-table\"><\/span>MDB AC SPD Selection Decision Table<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    Use the following table as an engineering screening tool. It provides a selection direction, not a substitute for lightning risk assessment, local wiring rules or project approval.\r\n  <\/p>\r\n\r\n  <div class=\"mdb-table-wrap\">\r\n    <table aria-label=\"Main distribution board AC SPD selection decision table\">\r\n      <thead>\r\n        <tr>\r\n          <th style=\"width: 30%;\">MDB condition<\/th>\r\n          <th style=\"width: 29%;\">Selection direction<\/th>\r\n          <th style=\"width: 41%;\">What must be confirmed<\/th>\r\n        <\/tr>\r\n      <\/thead>\r\n      <tbody>\r\n        <tr>\r\n          <td data-label=\"MDB condition\"><strong>External lightning protection system is installed<\/strong><\/td>\r\n          <td data-label=\"Selection direction\">Evaluate Type 1 or a tested Type 1+2 SPD at the supply origin.<\/td>\r\n          <td data-label=\"What must be confirmed\">LPS class, expected lightning-current distribution, supply arrangement, required Iimp and coordination with downstream SPDs.<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"MDB condition\"><strong>Overhead incoming supply or another direct-lightning-current exposure is identified<\/strong><\/td>\r\n          <td data-label=\"Selection direction\">Type 1 capability may be required.<\/td>\r\n          <td data-label=\"What must be confirmed\">Risk assessment, local installation rules and whether partial lightning current can enter the board.<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"MDB condition\"><strong>No Type 1 condition is identified, but surge protection is required at the origin<\/strong><\/td>\r\n          <td data-label=\"Selection direction\">A Type 2 SPD may be suitable.<\/td>\r\n          <td data-label=\"What must be confirmed\">Supply system, Uc, Up, In, Imax, protected equipment withstand level and backup protection.<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"MDB condition\"><strong>One device must provide both Type 1 and Type 2 performance<\/strong><\/td>\r\n          <td data-label=\"Selection direction\">Use a device tested and declared as Type 1+2.<\/td>\r\n          <td data-label=\"What must be confirmed\">Do not assume that any Type 1 product provides the required Type 2 protection level. Check the complete declared test data.<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"MDB condition\"><strong>Critical electronic equipment is supplied far downstream<\/strong><\/td>\r\n          <td data-label=\"Selection direction\">Coordinate the MDB SPD with additional downstream protection.<\/td>\r\n          <td data-label=\"What must be confirmed\">Cable route, separation distance, equipment impulse withstand, Up at the equipment terminals and manufacturer coordination guidance.<\/td>\r\n        <\/tr>\r\n      <\/tbody>\r\n    <\/table>\r\n  <\/div>\r\n\r\n  <p class=\"mdb-table-note\">\r\n    Procurement conclusion: the same 400\/230 V MDB can require different SPD types when lightning exposure, supply entry and downstream protection requirements are different.\r\n  <\/p>\r\n\r\n  <figure>\r\n    <img src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/type-1-type-2-type-1-plus-2-spd-selection-flow.webp\" alt=\"Type 1 Type 2 and Type 1 plus 2 SPD selection flow for a main distribution board\" loading=\"lazy\" decoding=\"async\">\r\n    <figcaption>\r\n      Type selection should begin with the surge environment and installation position. It should not begin with a preferred kA rating or a supplier's standard stock model.\r\n    <\/figcaption>\r\n  <\/figure>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"how-to-choose-type-1-type-2-or-type-12\"><\/span>How to Choose Type 1, Type 2 or Type 1+2<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <h3>Type 1: When Lightning Current May Enter the MDB<\/h3>\r\n\r\n  <p>\r\n    Type 1 SPDs are tested with a 10\/350 \u00b5s lightning impulse current. They are selected where the device may need to conduct partial lightning current at the origin of the installation.\r\n    <a class=\"mdb-ref\" href=\"#mdb-ref-1\" aria-label=\"Reference 1\">[1]<\/a>\r\n    <a class=\"mdb-ref\" href=\"#mdb-ref-2\" aria-label=\"Reference 2\">[2]<\/a>\r\n  <\/p>\r\n\r\n  <p>\r\n    A building with an external lightning protection system is a common reason to evaluate Type 1 protection at the MDB. The required Iimp should be derived from the lightning protection design and current distribution, not copied from another project.\r\n  <\/p>\r\n\r\n  <div class=\"mdb-meaning\">\r\n    <strong>Buyer meaning:<\/strong> Request the declared Iimp per protection mode or per pole, the total lightning-current capability where relevant, the connection diagram and the applicable certificate or test-report scope.\r\n  <\/div>\r\n\r\n  <h3>Type 2: When the Main Requirement Is Transient Overvoltage Limitation<\/h3>\r\n\r\n  <p>\r\n    Type 2 SPDs are tested with an 8\/20 \u00b5s current waveform and are commonly used to limit induced lightning surges and switching overvoltages. A Type 2 device can be suitable at the MDB when the installation assessment does not require Type 1 lightning-current capability.\r\n    <a class=\"mdb-ref\" href=\"#mdb-ref-1\" aria-label=\"Reference 1\">[1]<\/a>\r\n    <a class=\"mdb-ref\" href=\"#mdb-ref-5\" aria-label=\"Reference 5\">[5]<\/a>\r\n  <\/p>\r\n\r\n  <p>\r\n    The word \u201cmain\u201d in main distribution board does not automatically mean that every project needs Type 1. The decision depends on whether partial lightning current is expected at that location.\r\n  <\/p>\r\n\r\n  <div class=\"mdb-meaning\">\r\n    <strong>Buyer meaning:<\/strong> A supplier should explain why Type 2 is suitable for the specified supply origin. \u201cThis is our standard MDB model\u201d is not enough technical justification.\r\n  <\/div>\r\n\r\n  <h3>Type 1+2: Combined Performance in One Tested Device<\/h3>\r\n\r\n  <p>\r\n    A Type 1+2 SPD has declared performance for both test classes. It is often considered at an MDB where the project requires lightning-current discharge and a lower voltage protection level in one unit.\r\n  <\/p>\r\n\r\n  <p>\r\n    Type 1+2 does not mean that downstream coordination can always be omitted. The final voltage at sensitive equipment is affected by the SPD's Up, conductor inductance, installation layout, cable distance and any additional protective stages.\r\n    <a class=\"mdb-ref\" href=\"#mdb-ref-3\" aria-label=\"Reference 3\">[3]<\/a>\r\n    <a class=\"mdb-ref\" href=\"#mdb-ref-6\" aria-label=\"Reference 6\">[6]<\/a>\r\n  <\/p>\r\n\r\n  <div class=\"mdb-warning\">\r\n    <h3>Do Not Select by Type Marking Alone<\/h3>\r\n    <p>\r\n      Two SPDs marked Type 1+2 can have different Uc, Iimp, In, Up, short-circuit behaviour, protection modes, module widths and backup-protection requirements. The complete datasheet and project conditions must be compared.\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"how-to-judge-3p-4p-and-3pn-configurations\"><\/span>How to Judge 3P, 4P and 3P+N Configurations<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    Pole labels are not always used consistently across suppliers. \u201c4P\u201d may describe four modules, four terminals or a specific protection circuit. \u201c3P+N\u201d may refer to a three-phase arrangement with a dedicated neutral-to-earth protection element. The buyer should therefore verify the internal protection modes and wiring diagram instead of approving the model from the pole name alone.\r\n  <\/p>\r\n\r\n  <div class=\"mdb-table-wrap\">\r\n    <table aria-label=\"3P 4P and 3P plus N SPD configuration comparison\">\r\n      <thead>\r\n        <tr>\r\n          <th style=\"width: 24%;\">Market description<\/th>\r\n          <th style=\"width: 35%;\">What it may describe<\/th>\r\n          <th style=\"width: 41%;\">Approval question<\/th>\r\n        <\/tr>\r\n      <\/thead>\r\n      <tbody>\r\n        <tr>\r\n          <td data-label=\"Market description\"><strong>3P<\/strong><\/td>\r\n          <td data-label=\"What it may describe\">Three phase-related protection paths, often used where there is no separate neutral conductor at the installation point.<\/td>\r\n          <td data-label=\"Approval question\">Is the system TN-C before PEN separation, or is neutral protection being omitted for another documented reason?<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Market description\"><strong>4P or 4+0<\/strong><\/td>\r\n          <td data-label=\"What it may describe\">Four similar protection paths involving L1, L2, L3 and N, commonly connected toward PE according to the declared circuit.<\/td>\r\n          <td data-label=\"Approval question\">What are the exact L-PE, N-PE or L-N protection modes, and are they suitable for the earthing system and temporary overvoltage conditions?<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Market description\"><strong>3P+N or 3+1<\/strong><\/td>\r\n          <td data-label=\"What it may describe\">Three L-N protection paths plus one dedicated N-PE element, often a different technology from the phase modules.<\/td>\r\n          <td data-label=\"Approval question\">Is the N-PE element correctly rated for total discharge current, follow current and the selected TT or TN-S arrangement?<\/td>\r\n        <\/tr>\r\n      <\/tbody>\r\n    <\/table>\r\n  <\/div>\r\n\r\n  <p class=\"mdb-table-note\">\r\n    Procurement conclusion: specify the required protection circuit, not only \u201c3P,\u201d \u201c4P\u201d or \u201c3P+N\u201d in the purchase order.\r\n  <\/p>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"tt-tn-s-and-tn-c-s-system-differences\"><\/span>TT, TN-S and TN-C-S System Differences<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    The earthing arrangement determines which conductors are present at the MDB and how surge current should be diverted. It also changes the temporary overvoltage conditions that the SPD may experience.\r\n  <\/p>\r\n\r\n  <figure>\r\n    <img src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/tt-tn-s-tn-c-s-ac-spd-selection-flow.webp\" alt=\"TT TN-S and TN-C-S earthing system AC SPD configuration selection flow for main distribution boards\" loading=\"lazy\" decoding=\"async\">\r\n    <figcaption>\r\n      The selected protection circuit must match the actual earthing arrangement at the SPD installation point. The system name alone is not sufficient without knowing where N, PE or PEN are separated.\r\n    <\/figcaption>\r\n  <\/figure>\r\n\r\n  <h3>TT System<\/h3>\r\n\r\n  <p>\r\n    In a TT system, the installation protective earth is not the same conductor as the supply neutral. A 3+1 arrangement, with phase-to-neutral protection and a dedicated neutral-to-earth element, is commonly evaluated because it can provide a defined N-PE discharge path while addressing TT-system temporary overvoltage considerations.\r\n  <\/p>\r\n\r\n  <p>\r\n    This is not a universal instruction to use every product marketed as \u201c3+1.\u201d The N-PE element, Uc values, protection modes, disconnection arrangement and TOV performance must all match the project and local installation rules.\r\n    <a class=\"mdb-ref\" href=\"#mdb-ref-3\" aria-label=\"Reference 3\">[3]<\/a>\r\n    <a class=\"mdb-ref\" href=\"#mdb-ref-6\" aria-label=\"Reference 6\">[6]<\/a>\r\n  <\/p>\r\n\r\n  <h3>TN-S System<\/h3>\r\n\r\n  <p>\r\n    In a TN-S system, neutral and protective earth are separate throughout the relevant part of the installation. The MDB solution may use a four-path arrangement or a 3+1 circuit, depending on the protection concept and the manufacturer's declared wiring.\r\n  <\/p>\r\n\r\n  <p>\r\n    The correct choice is determined by protection modes, Uc, TOV behaviour, Up and system coordination. \u201cTN-S means 4P\u201d is too broad to use as an approval rule.\r\n  <\/p>\r\n\r\n  <h3>TN-C-S System<\/h3>\r\n\r\n  <p>\r\n    A TN-C-S installation uses a PEN conductor upstream and separate N and PE conductors after the separation point. The SPD configuration depends on whether it is installed before or after that point.\r\n  <\/p>\r\n\r\n  <p>\r\n    Before PEN separation, the installation conditions resemble TN-C. After separation, the protected conductors resemble TN-S. The supplier must receive the single-line diagram and the exact SPD location to avoid an incorrect neutral or earth connection.\r\n  <\/p>\r\n\r\n  <div class=\"mdb-warning\">\r\n    <h3>Critical Wiring Boundary<\/h3>\r\n    <p>\r\n      Never approve a TN-C-S SPD configuration without identifying the PEN separation point. An incorrect assumption can create the wrong protection path or an unacceptable N-PE connection.\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"which-parameters-must-an-mdb-buyer-confirm\"><\/span>Which Parameters Must an MDB Buyer Confirm?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    The following parameters answer different engineering questions. None should be used alone as proof that one SPD is better than another.\r\n  <\/p>\r\n\r\n  <div class=\"mdb-table-wrap\">\r\n    <table aria-label=\"Main distribution board SPD parameter confirmation table\">\r\n      <thead>\r\n        <tr>\r\n          <th style=\"width: 20%;\">Parameter<\/th>\r\n          <th style=\"width: 37%;\">What it means<\/th>\r\n          <th style=\"width: 43%;\">What the buyer must confirm<\/th>\r\n        <\/tr>\r\n      <\/thead>\r\n      <tbody>\r\n        <tr>\r\n          <td data-label=\"Parameter\"><strong>Uc<\/strong><\/td>\r\n          <td data-label=\"What it means\">Maximum continuous operating voltage for the declared protection mode.<\/td>\r\n          <td data-label=\"What the buyer must confirm\">Nominal voltage, maximum normal operating voltage, earthing system, voltage tolerance and TOV conditions.<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Parameter\"><strong>Iimp<\/strong><\/td>\r\n          <td data-label=\"What it means\">Lightning impulse current capability used for Type 1 classification, tested with a 10\/350 \u00b5s waveform.<\/td>\r\n          <td data-label=\"What the buyer must confirm\">Required value per pole or mode, total current distribution and the lightning protection design basis.<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Parameter\"><strong>In<\/strong><\/td>\r\n          <td data-label=\"What it means\">Nominal discharge current, generally associated with repeated 8\/20 \u00b5s testing.<\/td>\r\n          <td data-label=\"What the buyer must confirm\">Declared Type 2 performance and whether the rating applies per mode or per module.<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Parameter\"><strong>Imax<\/strong><\/td>\r\n          <td data-label=\"What it means\">Maximum discharge current declared for an 8\/20 \u00b5s event under the applicable test method.<\/td>\r\n          <td data-label=\"What the buyer must confirm\">Do not use Imax alone. Compare In, Up, Uc, test class and short-circuit performance.<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Parameter\"><strong>Up<\/strong><\/td>\r\n          <td data-label=\"What it means\">Voltage protection level declared during surge testing.<\/td>\r\n          <td data-label=\"What the buyer must confirm\">Equipment impulse withstand, lead length and the resulting protection level at the actual equipment terminals.<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Parameter\"><strong>TOV<\/strong><\/td>\r\n          <td data-label=\"What it means\">Behaviour under a temporary power-frequency overvoltage rather than a short surge impulse.<\/td>\r\n          <td data-label=\"What the buyer must confirm\">Earthing-system faults, neutral conditions and whether the SPD withstands or safely fails under the declared test.<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Parameter\"><strong>SCCR or short-circuit withstand<\/strong><\/td>\r\n          <td data-label=\"What it means\">The SPD's ability to be safely applied at a point with a specified prospective short-circuit current under declared protection conditions.<\/td>\r\n          <td data-label=\"What the buyer must confirm\">Prospective fault current at the MDB, required fuse or breaker, and certificate scope for the complete combination.<\/td>\r\n        <\/tr>\r\n      <\/tbody>\r\n    <\/table>\r\n  <\/div>\r\n\r\n  <p class=\"mdb-table-note\">\r\n    Procurement conclusion: a high Imax does not compensate for an unsuitable Uc, an excessive Up, a missing Type 1 rating or inadequate short-circuit coordination.\r\n  <\/p>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"eight-step-selection-workflow-for-an-mdb-project\"><\/span>Eight-Step Selection Workflow for an MDB Project<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <ol class=\"mdb-steps\">\r\n    <li>\r\n      <strong>Confirm the supply data.<\/strong>\r\n      Record nominal phase-to-phase and phase-to-neutral voltage, frequency and maximum normal operating voltage.\r\n    <\/li>\r\n    <li>\r\n      <strong>Identify the earthing arrangement at the exact SPD location.<\/strong>\r\n      State TT, TN-S, TN-C or TN-C-S and mark the PEN separation point where applicable.\r\n    <\/li>\r\n    <li>\r\n      <strong>Determine whether Type 1 capability is required.<\/strong>\r\n      Review the external LPS, overhead supply, lightning-risk assessment and the possibility of partial lightning current entering the installation.\r\n    <\/li>\r\n    <li>\r\n      <strong>Define the protection circuit.<\/strong>\r\n      Specify the required L-N, L-PE, N-PE or L-PEN modes instead of relying only on 3P, 4P or 3+1 terminology.\r\n    <\/li>\r\n    <li>\r\n      <strong>Select the voltage-related parameters.<\/strong>\r\n      Confirm Uc, TOV behaviour and Up against the actual system and protected equipment.\r\n    <\/li>\r\n    <li>\r\n      <strong>Confirm discharge-current performance.<\/strong>\r\n      Check Iimp for Type 1 and In\/Imax for Type 2 according to the project requirement.\r\n    <\/li>\r\n    <li>\r\n      <strong>Coordinate short-circuit and backup protection.<\/strong>\r\n      Compare the MDB prospective short-circuit current, upstream protective device and the manufacturer's maximum backup fuse or approved MCB data.\r\n    <\/li>\r\n    <li>\r\n      <strong>Approve installation and documentation.<\/strong>\r\n      Check connection length, conductor route, DIN-rail space, remote contact, replacement module, wiring diagram, datasheet and model-specific certificate scope.\r\n    <\/li>\r\n  <\/ol>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"three-realistic-mdb-selection-scenarios\"><\/span>Three Realistic MDB Selection Scenarios<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <div class=\"mdb-scenario\">\r\n    <h3>Scenario 1: Commercial MDB, 400\/230 V TN-S, No External LPS<\/h3>\r\n    <p>\r\n      A Type 2 SPD may be suitable when the project assessment does not identify partial lightning current at the supply origin. The engineer still needs to confirm the protection circuit, Uc, Up, In, Imax, short-circuit current and downstream equipment requirements.\r\n    <\/p>\r\n    <p class=\"mdb-small\">\r\n      Selection boundary: the absence of an external LPS does not by itself prove that Type 1 is unnecessary. Overhead supply and other exposure conditions must also be reviewed.\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <div class=\"mdb-scenario\">\r\n    <h3>Scenario 2: Industrial MDB, TN-C-S, External LPS Installed<\/h3>\r\n    <p>\r\n      Type 1 or Type 1+2 protection should be evaluated at the origin. The designer must identify whether the SPD is before or after PEN separation and calculate or specify the required Iimp from the lightning protection concept.\r\n    <\/p>\r\n    <p class=\"mdb-small\">\r\n      Selection boundary: do not automatically copy 12.5 kA or 25 kA per pole from another project. LPS class, current distribution and system configuration can change the requirement.\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <div class=\"mdb-scenario\">\r\n    <h3>Scenario 3: Three-Phase TT Main Board Supplying Sensitive Controls<\/h3>\r\n    <p>\r\n      A 3+1 protection circuit is commonly evaluated, with phase-to-neutral modules and a dedicated N-PE element. The final model must be checked for Uc, TOV, total N-PE discharge duty, Up and coordination with downstream control-panel SPDs.\r\n    <\/p>\r\n    <p class=\"mdb-small\">\r\n      Selection boundary: \u201c3P+N\u201d on a quotation is insufficient. Request the circuit diagram and declared ratings for every protection mode.\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"backup-fuse-or-mcb-how-to-confirm-it\"><\/span>Backup Fuse or MCB: How to Confirm It<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    The SPD's internal thermal disconnector is not automatically a substitute for external short-circuit backup protection. Its purpose and operating conditions are different.\r\n  <\/p>\r\n\r\n  <p>\r\n    The required external fuse or MCB depends on the SPD design, prospective short-circuit current, upstream protective device and the manufacturer's tested coordination. Some SPDs include integrated backup protection. Others specify a maximum permissible backup fuse or an approved breaker characteristic.\r\n    <a class=\"mdb-ref\" href=\"#mdb-ref-3\" aria-label=\"Reference 3\">[3]<\/a>\r\n    <a class=\"mdb-ref\" href=\"#mdb-ref-5\" aria-label=\"Reference 5\">[5]<\/a>\r\n  <\/p>\r\n\r\n  <div class=\"mdb-note\">\r\n    <h3>Information Required for Backup-Protection Approval<\/h3>\r\n    <ul>\r\n      <li>Prospective short-circuit current at the MDB installation point<\/li>\r\n      <li>Upstream fuse or circuit-breaker type and rating<\/li>\r\n      <li>SPD maximum backup fuse or approved MCB data<\/li>\r\n      <li>Required discrimination or selectivity with upstream protection<\/li>\r\n      <li>SPD short-circuit withstand or SCCR under the declared protective arrangement<\/li>\r\n      <li>Conductor cross-section and terminal capacity<\/li>\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"installation-position-and-connection-length\"><\/span>Installation Position and Connection Length<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    An MDB SPD is normally connected close to the incoming section, either near the incoming isolator or at the closest suitable outgoing connection point permitted by the panel design. The objective is to create a short, direct path from the live conductors through the SPD to PE or PEN.\r\n  <\/p>\r\n\r\n  <p>\r\n    Long conductors add inductive voltage during a fast surge. This additional voltage appears in series with the SPD's declared Up and can materially increase the voltage reaching the equipment.\r\n  <\/p>\r\n\r\n  <p>\r\n    IEC-based application guidance commonly targets a combined active-conductor-to-SPD and SPD-to-PE\/PEN connection path of no more than approximately 0.5 m where the selected installation arrangement permits it. Local rules, panel construction and the manufacturer's instructions remain the final authority.\r\n    <a class=\"mdb-ref\" href=\"#mdb-ref-3\" aria-label=\"Reference 3\">[3]<\/a>\r\n    <a class=\"mdb-ref\" href=\"#mdb-ref-5\" aria-label=\"Reference 5\">[5]<\/a>\r\n  <\/p>\r\n\r\n  <div class=\"mdb-warning\">\r\n    <h3>Common Panel Layout Mistake<\/h3>\r\n    <p>\r\n      Installing the SPD in an available DIN-rail space far from the incoming busbar can produce long phase and earth leads. The product may have a low declared Up, but the complete installed path can deliver a much higher residual voltage.\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"when-is-a-remote-signal-contact-worth-specifying\"><\/span>When Is a Remote Signal Contact Worth Specifying?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    Remote signalling is useful when the MDB is unattended, difficult to inspect or connected to a building-management, SCADA or maintenance system. A volt-free changeover contact can report the SPD status without requiring a technician to open the panel for every inspection.\r\n  <\/p>\r\n\r\n  <p>\r\n    It is not mandatory for every MDB. The project should confirm the contact logic, terminal rating, normal and alarm states, cable interface and whether the alarm indicates module end-of-life, disconnection or another condition.\r\n  <\/p>\r\n\r\n  <div class=\"mdb-meaning\">\r\n    <strong>Buyer meaning:<\/strong> Add \u201cremote contact required\u201d to the purchase specification and request the terminal diagram. Do not assume that the standard model and remote-signal model share the same width or model code.\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"what-happens-when-the-wrong-mdb-spd-is-selected\"><\/span>What Happens When the Wrong MDB SPD Is Selected?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <div class=\"mdb-table-wrap\">\r\n    <table aria-label=\"Consequences of incorrect MDB SPD selection\">\r\n      <thead>\r\n        <tr>\r\n          <th style=\"width: 31%;\">Selection error<\/th>\r\n          <th style=\"width: 34%;\">Possible consequence<\/th>\r\n          <th style=\"width: 35%;\">Required correction<\/th>\r\n        <\/tr>\r\n      <\/thead>\r\n      <tbody>\r\n        <tr>\r\n          <td data-label=\"Selection error\"><strong>Type 2 used where Type 1 lightning-current capability is required<\/strong><\/td>\r\n          <td data-label=\"Possible consequence\">The SPD may not be suitable for the expected 10\/350 \u00b5s lightning-current duty.<\/td>\r\n          <td data-label=\"Required correction\">Review the lightning protection design and select a correctly tested Type 1 or Type 1+2 device.<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Selection error\"><strong>Uc is too low for the real operating and TOV conditions<\/strong><\/td>\r\n          <td data-label=\"Possible consequence\">Accelerated ageing, thermal stress, disconnection or premature failure.<\/td>\r\n          <td data-label=\"Required correction\">Confirm maximum continuous voltage, earthing system and TOV performance.<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Selection error\"><strong>Uc is raised without reviewing Up<\/strong><\/td>\r\n          <td data-label=\"Possible consequence\">The voltage protection level may no longer be suitable for downstream equipment.<\/td>\r\n          <td data-label=\"Required correction\">Evaluate Uc and Up together with equipment impulse withstand.<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Selection error\"><strong>Wrong 3P, 4P or 3+1 circuit<\/strong><\/td>\r\n          <td data-label=\"Possible consequence\">Missing protection mode or incorrect N, PE or PEN connection.<\/td>\r\n          <td data-label=\"Required correction\">Approve the protection circuit from the earthing system and single-line diagram.<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Selection error\"><strong>Backup protection is not coordinated<\/strong><\/td>\r\n          <td data-label=\"Possible consequence\">Nuisance tripping, failure to clear a fault safely or non-compliance with the tested SPD combination.<\/td>\r\n          <td data-label=\"Required correction\">Follow the manufacturer's fuse or MCB coordination data and verify fault current.<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Selection error\"><strong>Connection leads are too long<\/strong><\/td>\r\n          <td data-label=\"Possible consequence\">The installed residual voltage can exceed the product's declared Up.<\/td>\r\n          <td data-label=\"Required correction\">Rearrange the panel connection to shorten and straighten the surge-current path.<\/td>\r\n        <\/tr>\r\n      <\/tbody>\r\n    <\/table>\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"oem-and-bulk-order-confirmation\"><\/span>OEM and Bulk-Order Confirmation<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    An OEM order should freeze the complete electrical configuration before the label, packaging or production batch is approved. A model name alone is not enough to control technical consistency.\r\n  <\/p>\r\n\r\n  <div class=\"mdb-checklist\">\r\n    <h3>Information the Buyer Should Send<\/h3>\r\n    <ul class=\"mdb-check-grid\">\r\n      <li>Single-line diagram<\/li>\r\n      <li>Nominal and maximum operating voltage<\/li>\r\n      <li>Frequency<\/li>\r\n      <li>TT, TN-S, TN-C or TN-C-S arrangement<\/li>\r\n      <li>PEN separation point<\/li>\r\n      <li>External LPS and lightning-risk information<\/li>\r\n      <li>Required Type 1, Type 2 or Type 1+2 class<\/li>\r\n      <li>Required protection modes<\/li>\r\n      <li>Iimp, In, Imax and Up requirements<\/li>\r\n      <li>Prospective short-circuit current<\/li>\r\n      <li>Backup fuse or MCB arrangement<\/li>\r\n      <li>Remote signal requirement<\/li>\r\n      <li>DIN-rail space and terminal direction<\/li>\r\n      <li>Quantity and spare-module quantity<\/li>\r\n      <li>Required standards and target market<\/li>\r\n      <li>OEM label, model code and packaging files<\/li>\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <div class=\"mdb-checklist\">\r\n    <h3>Information the Supplier Should Return<\/h3>\r\n    <ul class=\"mdb-check-grid\">\r\n      <li>Full model code<\/li>\r\n      <li>Protection-circuit diagram<\/li>\r\n      <li>Complete technical datasheet<\/li>\r\n      <li>Uc, TOV and Up by protection mode<\/li>\r\n      <li>Iimp, In and Imax declarations<\/li>\r\n      <li>Short-circuit and backup-protection data<\/li>\r\n      <li>Installation and torque instructions<\/li>\r\n      <li>Module dimensions and panel width<\/li>\r\n      <li>Remote-contact terminal diagram<\/li>\r\n      <li>Replacement-module reference<\/li>\r\n      <li>Model-specific certificate scope<\/li>\r\n      <li>Approved OEM label artwork<\/li>\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <div class=\"mdb-cta\">\r\n    <h2><span class=\"ez-toc-section\" id=\"need-an-mdb-spd-configuration-review\"><\/span>Need an MDB SPD Configuration Review?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n    <p>\r\n      Send the system voltage, earthing arrangement, single-line diagram, external lightning protection information, prospective short-circuit current and required protection class. LEEYEE can use these details to review a suitable AC SPD configuration for panel, project or OEM approval.\r\n    <\/p>\r\n\r\n    <button type=\"button\" class=\"leeyee-about-btn-light leeyee-site-popup-btn\" aria-label=\"Request Model Recommendation\">\r\n      <span class=\"w-btn-label\">Request Model Recommendation<\/span>\r\n    <\/button>\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"frequently-asked-questions\"><\/span>Frequently Asked Questions<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <div class=\"mdb-faq\">\r\n    <h3>Does every main distribution board require a Type 1 SPD?<\/h3>\r\n    <p>\r\n      No. Type 1 is selected where partial lightning current may enter the installation. A Type 2 SPD may be suitable at an MDB when the project assessment does not require Type 1 capability. The external LPS, supply route, lightning exposure and local rules must be checked.\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <div class=\"mdb-faq\">\r\n    <h3>Can a Type 1+2 SPD replace every downstream Type 2 SPD?<\/h3>\r\n    <p>\r\n      Not automatically. Additional coordinated protection may be needed when sensitive equipment is far from the MDB, has a lower impulse withstand level or requires a lower voltage protection level at its terminals.\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <div class=\"mdb-faq\">\r\n    <h3>Is a 4P SPD the same as a 3+1 SPD?<\/h3>\r\n    <p>\r\n      No. A 4P or 4+0 arrangement and a 3+1 arrangement can use different protection paths and component technologies. Compare the internal circuit, protection modes, Uc, TOV and N-PE element instead of relying on the number of modules.\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <div class=\"mdb-faq\">\r\n    <h3>Which SPD should be used for a 400\/230 V TN-S MDB?<\/h3>\r\n    <p>\r\n      The voltage and TN-S label are not enough to select one model. Confirm whether Type 1 capability is required, then select the protection circuit, Uc, Up, discharge-current ratings, short-circuit coordination and backup protection. Both four-path and 3+1 solutions may exist, depending on the engineering design.\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <div class=\"mdb-faq\">\r\n    <h3>Is a higher Imax always better for an MDB?<\/h3>\r\n    <p>\r\n      No. Imax is only one Type 2 performance value. A suitable SPD must also have the correct test class, Uc, In, Up, protection modes, TOV behaviour and short-circuit capability.\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <div class=\"mdb-faq\">\r\n    <h3>Can an MCB always replace the SPD backup fuse?<\/h3>\r\n    <p>\r\n      No. An MCB should be used only when its type, rating and operating characteristic are accepted by the SPD manufacturer for the available short-circuit current. Otherwise, use the declared fuse arrangement or obtain written technical confirmation.\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <div class=\"mdb-faq\">\r\n    <h3>Should an OEM MDB include remote signalling?<\/h3>\r\n    <p>\r\n      Remote signalling is useful for critical, unattended or centrally monitored panels. Confirm the alarm logic, terminal rating, BMS or SCADA interface and additional panel space before fixing the OEM model.\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"references\"><\/span>References<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <ol class=\"mdb-references\">\r\n    <li id=\"mdb-ref-1\">\r\n      International Electrotechnical Commission, <em>IEC 61643-01:2024 \u2014 Low-voltage surge protective devices \u2014 Part 01: General requirements and test methods<\/em>.\r\n      <a href=\"https:\/\/webstore.iec.ch\/en\/publication\/65315\" target=\"_blank\" rel=\"noopener noreferrer\">Official IEC publication page<\/a>.\r\n    <\/li>\r\n    <li id=\"mdb-ref-2\">\r\n      International Electrotechnical Commission, <em>IEC 61643-11:2025 \u2014 Low-voltage surge protective devices \u2014 Part 11: Surge protective devices connected to AC low-voltage power systems \u2014 Requirements and test methods<\/em>.\r\n      <a href=\"https:\/\/webstore.iec.ch\/en\/publication\/65314\" target=\"_blank\" rel=\"noopener noreferrer\">Official IEC publication page<\/a>.\r\n    <\/li>\r\n    <li id=\"mdb-ref-3\">\r\n      International Electrotechnical Commission, <em>IEC 60364-5-53:2019+AMD1:2020+AMD2:2024 \u2014 Low-voltage electrical installations \u2014 Selection and erection of electrical equipment<\/em>.\r\n      <a href=\"https:\/\/webstore.iec.ch\/en\/publication\/104394\" target=\"_blank\" rel=\"noopener noreferrer\">Official IEC consolidated-version page<\/a>.\r\n    <\/li>\r\n    <li id=\"mdb-ref-4\">\r\n      International Electrotechnical Commission, <em>IEC 62305-4:2024 \u2014 Protection against lightning \u2014 Part 4: Electrical and electronic systems within structures<\/em>.\r\n      <a href=\"https:\/\/webstore.iec.ch\/en\/publication\/29590\" target=\"_blank\" rel=\"noopener noreferrer\">Official IEC publication page<\/a>.\r\n    <\/li>\r\n    <li id=\"mdb-ref-5\">\r\n      DEHN, <em>Surge Protection in Low-Voltage Switchgear Assemblies<\/em>, application white paper covering supply-point SPDs, backup protection, coordination and conductor length.\r\n      <a href=\"https:\/\/www.dehn-international.com\/sites\/default\/files\/media\/files\/surge-protection-low-voltage-switchgear-assemblies-wpx004-e.pdf\" target=\"_blank\" rel=\"noopener noreferrer\">Official technical document<\/a>.\r\n    <\/li>\r\n    <li id=\"mdb-ref-6\">\r\n      ABB Furse, <em>Mains Power Protection \u2014 Type 1 and Type 2 Surge Protection Series Product Guide<\/em>, including MDB applications, earthing-system diagrams, remote signalling and installation guidance.\r\n      <a href=\"https:\/\/library.e.abb.com\/public\/e365a493461041e48f8a0f487f885197\/Furse_ESP_T1_T2_Surge_Protection_Series_Product_Guide_211021.pdf\" target=\"_blank\" rel=\"noopener noreferrer\">Official ABB technical document<\/a>.\r\n    <\/li>\r\n  <\/ol>\r\n\r\n  <script>\r\n  (function () {\r\n    if (window.leeyeeMdbPopupHandlerAdded) {\r\n      return;\r\n    }\r\n\r\n    window.leeyeeMdbPopupHandlerAdded = true;\r\n\r\n    document.addEventListener(\"click\", function (event) {\r\n      var button = event.target.closest(\".leeyee-site-popup-btn\");\r\n\r\n      if (!button) {\r\n        return;\r\n      }\r\n\r\n      var article = document.getElementById(\"leeyee-mdb-ac-spd-guide\");\r\n\r\n      if (!article || !article.contains(button)) {\r\n        return;\r\n      }\r\n\r\n      event.preventDefault();\r\n\r\n      var realPopupTrigger = document.querySelector(\".w-popup.ush_popup_1 .w-popup-trigger\");\r\n\r\n      if (realPopupTrigger) {\r\n        realPopupTrigger.click();\r\n      } else {\r\n        window.open(\"https:\/\/www.cnspd.com\/contact\/\", \"_blank\", \"noopener\");\r\n      }\r\n    });\r\n  })();\r\n  <\/script>\r\n<\/article>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>Selecting an AC surge protective device for a main distribution board is not simply a matter of choosing the largest kA value. The correct MDB surge protection solution depends on where lightning current may enter, the earthing system, the required protection modes, the operating voltage, the available short-circuit current and the equipment located downstream. This&#8230;<\/p>","protected":false},"author":18,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-30642","post","type-post","status-publish","format-standard","hentry","category-news"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.1 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>AC SPD for Main Distribution Board: Selection Guide<\/title>\n<meta name=\"description\" content=\"Select the right AC SPD for an MDB by Type 1, Type 2, Type 1+2, earthing system, pole configuration, parameters and backup protection.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/\" \/>\n<meta property=\"og:locale\" content=\"id_ID\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"AC SPD for Main Distribution Board: Selection Guide\" \/>\n<meta property=\"og:description\" content=\"Select the right AC SPD for an MDB by Type 1, Type 2, Type 1+2, earthing system, pole configuration, parameters and backup protection.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.cnspd.com\/id\/main-distribution-board-ac-spd\/\" \/>\n<meta property=\"og:site_name\" content=\"Surge Protector, Surge Arrestor, Isolating Switch - 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