{"id":30017,"date":"2026-07-14T12:57:20","date_gmt":"2026-07-14T04:57:20","guid":{"rendered":"https:\/\/www.cnspd.com\/?p=30017"},"modified":"2026-07-14T14:32:37","modified_gmt":"2026-07-14T06:32:37","slug":"tn-s-system-spd-wiring-guide-3p-4p-and-3pn-selection","status":"publish","type":"post","link":"https:\/\/www.cnspd.com\/pt\/tn-s-system-spd-wiring\/","title":{"rendered":"TN-S System SPD Wiring Guide: 3P, 4P and 3P+N Selection"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"30017\" class=\"elementor elementor-30017\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-e0025a4 e-flex e-con-boxed e-con e-parent\" data-id=\"e0025a4\" 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-4706392 elementor-widget elementor-widget-html\" data-id=\"4706392\" 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\/* =========================================================\r\n   LEEYEE \u2014 TN-S SYSTEM SPD WIRING GUIDE\r\n   Article page for Impreza + WPBakery Custom HTML\r\n   WP page title provides the H1\r\n   ========================================================= *\/\r\n\r\n.ly-tns-page,\r\n.ly-tns-page *,\r\n.ly-tns-page *::before,\r\n.ly-tns-page *::after {\r\n  box-sizing: border-box;\r\n}\r\n\r\n.ly-tns-page {\r\n  --ly-blue: #004898;\r\n  --ly-blue-dark: #00366f;\r\n  --ly-blue-soft: #edf5ff;\r\n  --ly-blue-line: #c9ddf3;\r\n  --ly-text: #172234;\r\n  --ly-muted: #58677a;\r\n  --ly-border: #dce4ed;\r\n  --ly-bg: #f6f8fb;\r\n  --ly-white: #ffffff;\r\n  --ly-green: #167c4b;\r\n  --ly-green-soft: #ebf8f1;\r\n  --ly-orange: #a85508;\r\n  --ly-orange-soft: #fff6e9;\r\n  --ly-red: #b42318;\r\n  --ly-red-soft: #fff1f0;\r\n  --ly-shadow: 0 12px 32px rgba(22, 49, 78, 0.08);\r\n\r\n  width: 100%;\r\n  max-width: none;\r\n  margin: 0;\r\n  padding: 0;\r\n  overflow-x: hidden;\r\n  background: var(--ly-white);\r\n  color: var(--ly-text);\r\n  font-family: inherit;\r\n  font-size: 17px;\r\n  line-height: 1.72;\r\n}\r\n\r\n.ly-tns-page a {\r\n  color: var(--ly-blue);\r\n  text-decoration: underline;\r\n  text-decoration-thickness: 1px;\r\n  text-underline-offset: 3px;\r\n}\r\n\r\n.ly-tns-page a:hover,\r\n.ly-tns-page a:focus {\r\n  color: var(--ly-blue-dark);\r\n}\r\n\r\n.ly-tns-page p {\r\n  margin: 0 0 18px;\r\n}\r\n\r\n.ly-tns-page strong {\r\n  color: var(--ly-text);\r\n  font-weight: 750;\r\n}\r\n\r\n.ly-tns-shell {\r\n  width: calc(100% - 48px);\r\n  max-width: 1180px;\r\n  margin: 0 auto;\r\n  padding: 24px 0 72px;\r\n}\r\n\r\n.ly-tns-section {\r\n  margin-top: 64px;\r\n  scroll-margin-top: 110px;\r\n}\r\n\r\n.ly-tns-section > h2 {\r\n  margin: 0 0 18px;\r\n  color: var(--ly-text);\r\n  font-size: 34px;\r\n  line-height: 1.22;\r\n  letter-spacing: -0.025em;\r\n}\r\n\r\n.ly-tns-section > h3 {\r\n  margin: 32px 0 14px;\r\n  color: var(--ly-text);\r\n  font-size: 24px;\r\n  line-height: 1.3;\r\n}\r\n\r\n.ly-tns-lead {\r\n  max-width: 920px;\r\n  margin-bottom: 25px;\r\n  color: var(--ly-muted);\r\n  font-size: 19px;\r\n  line-height: 1.72;\r\n}\r\n\r\n.ly-tns-eyebrow {\r\n  display: inline-flex;\r\n  align-items: center;\r\n  gap: 9px;\r\n  margin-bottom: 14px;\r\n  color: var(--ly-blue);\r\n  font-size: 13px;\r\n  font-weight: 800;\r\n  line-height: 1.4;\r\n  letter-spacing: 0.1em;\r\n  text-transform: uppercase;\r\n}\r\n\r\n.ly-tns-eyebrow::before {\r\n  width: 28px;\r\n  height: 3px;\r\n  border-radius: 999px;\r\n  background: var(--ly-blue);\r\n  content: \"\";\r\n}\r\n\r\n\/* =========================================================\r\n   INTRO AND QUICK ANSWER\r\n   ========================================================= *\/\r\n\r\n.ly-tns-intro {\r\n  padding: 10px 0 4px;\r\n}\r\n\r\n.ly-tns-intro h2 {\r\n  max-width: 900px;\r\n  margin: 0 0 18px;\r\n  color: var(--ly-text);\r\n  font-size: 39px;\r\n  line-height: 1.17;\r\n  letter-spacing: -0.034em;\r\n}\r\n\r\n.ly-tns-intro-text {\r\n  max-width: 940px;\r\n  color: var(--ly-muted);\r\n  font-size: 19px;\r\n  line-height: 1.72;\r\n}\r\n\r\n.ly-tns-direct-answer {\r\n  margin-top: 28px;\r\n  padding: 29px;\r\n  border: 1px solid var(--ly-blue-line);\r\n  border-left: 6px solid var(--ly-blue);\r\n  border-radius: 16px;\r\n  background: linear-gradient(135deg, #f8fbff 0%, #edf5ff 100%);\r\n  box-shadow: var(--ly-shadow);\r\n}\r\n\r\n.ly-tns-direct-answer h2 {\r\n  margin: 0 0 14px;\r\n  color: var(--ly-blue-dark);\r\n  font-size: 28px;\r\n  line-height: 1.28;\r\n}\r\n\r\n.ly-tns-direct-answer > p {\r\n  max-width: 970px;\r\n  margin-bottom: 20px;\r\n  color: #31465d;\r\n  font-size: 17px;\r\n  line-height: 1.72;\r\n}\r\n\r\n.ly-tns-answer-grid {\r\n  display: grid;\r\n  grid-template-columns: repeat(2, minmax(0, 1fr));\r\n  gap: 13px;\r\n}\r\n\r\n.ly-tns-answer-item {\r\n  position: relative;\r\n  min-width: 0;\r\n  padding: 15px 15px 15px 46px;\r\n  border: 1px solid rgba(0, 72, 152, 0.13);\r\n  border-radius: 10px;\r\n  background: rgba(255, 255, 255, 0.86);\r\n  color: #34465b;\r\n  font-size: 15px;\r\n  line-height: 1.62;\r\n}\r\n\r\n.ly-tns-answer-item::before {\r\n  position: absolute;\r\n  top: 16px;\r\n  left: 15px;\r\n  display: flex;\r\n  align-items: center;\r\n  justify-content: center;\r\n  width: 21px;\r\n  height: 21px;\r\n  border-radius: 50%;\r\n  background: var(--ly-blue);\r\n  color: #fff;\r\n  content: \"\u2713\";\r\n  font-size: 12px;\r\n  font-weight: 800;\r\n}\r\n\r\n\/* Safety *\/\r\n.ly-tns-safety {\r\n  display: flex;\r\n  align-items: flex-start;\r\n  gap: 12px;\r\n  margin-top: 21px;\r\n  padding: 15px 17px;\r\n  border: 1px solid #efd5ae;\r\n  border-radius: 11px;\r\n  background: #fffaf2;\r\n  color: #684a21;\r\n  font-size: 14px;\r\n  line-height: 1.65;\r\n}\r\n\r\n.ly-tns-safety-icon {\r\n  flex: 0 0 auto;\r\n  display: flex;\r\n  align-items: center;\r\n  justify-content: center;\r\n  width: 24px;\r\n  height: 24px;\r\n  border-radius: 50%;\r\n  background: #f4ddb7;\r\n  color: #704700;\r\n  font-weight: 800;\r\n}\r\n\r\n\/* =========================================================\r\n   IMAGES\r\n   ========================================================= *\/\r\n\r\n.ly-tns-figure {\r\n  width: 100%;\r\n  margin: 31px 0;\r\n  padding: 11px;\r\n  overflow: hidden;\r\n  border: 1px solid var(--ly-border);\r\n  border-radius: 16px;\r\n  background: var(--ly-white);\r\n  box-shadow: var(--ly-shadow);\r\n}\r\n\r\n.ly-tns-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: 0;\r\n  border-radius: 10px;\r\n  object-fit: contain;\r\n}\r\n\r\n.ly-tns-figure figcaption {\r\n  margin: 0;\r\n  padding: 13px 10px 3px;\r\n  color: var(--ly-muted);\r\n  font-size: 14px;\r\n  line-height: 1.6;\r\n  text-align: center;\r\n}\r\n\r\n.ly-tns-figure.is-primary {\r\n  border-color: var(--ly-blue-line);\r\n  background: #f8fbff;\r\n}\r\n\r\n\/* =========================================================\r\n   DECISION TABLE\r\n   ========================================================= *\/\r\n\r\n.ly-tns-decision {\r\n  margin-top: 30px;\r\n}\r\n\r\n.ly-tns-decision h3 {\r\n  margin: 0 0 14px;\r\n  color: var(--ly-text);\r\n  font-size: 23px;\r\n  line-height: 1.3;\r\n}\r\n\r\n.ly-tns-table-note {\r\n  margin-top: -10px;\r\n  color: var(--ly-muted);\r\n  font-size: 14px;\r\n}\r\n\r\n\/* =========================================================\r\n   TABLE OF CONTENTS\r\n   ========================================================= *\/\r\n\r\n.ly-tns-toc {\r\n  margin-top: 34px;\r\n  padding: 24px 27px;\r\n  border: 1px solid var(--ly-border);\r\n  border-radius: 14px;\r\n  background: var(--ly-bg);\r\n}\r\n\r\n.ly-tns-toc-title {\r\n  margin-bottom: 14px;\r\n  color: var(--ly-text);\r\n  font-size: 18px;\r\n  font-weight: 800;\r\n}\r\n\r\n.ly-tns-toc ol {\r\n  display: grid;\r\n  grid-template-columns: repeat(2, minmax(0, 1fr));\r\n  gap: 8px 32px;\r\n  margin: 0;\r\n  padding-left: 22px;\r\n}\r\n\r\n.ly-tns-toc li {\r\n  padding-left: 3px;\r\n  color: var(--ly-muted);\r\n  font-size: 15px;\r\n  line-height: 1.55;\r\n}\r\n\r\n.ly-tns-toc a {\r\n  color: #314158;\r\n  text-decoration: none;\r\n}\r\n\r\n.ly-tns-toc a:hover,\r\n.ly-tns-toc a:focus {\r\n  color: var(--ly-blue);\r\n  text-decoration: underline;\r\n}\r\n\r\n\/* =========================================================\r\n   TABLES\r\n   ========================================================= *\/\r\n\r\n.ly-tns-table-wrap {\r\n  width: 100%;\r\n  margin: 25px 0;\r\n  overflow-x: auto;\r\n  border: 1px solid var(--ly-border);\r\n  border-radius: 13px;\r\n  background: var(--ly-white);\r\n  -webkit-overflow-scrolling: touch;\r\n}\r\n\r\n.ly-tns-table {\r\n  width: 100%;\r\n  min-width: 820px;\r\n  border-collapse: collapse;\r\n  border-spacing: 0;\r\n}\r\n\r\n.ly-tns-table th,\r\n.ly-tns-table td {\r\n  padding: 15px 16px;\r\n  border-right: 1px solid var(--ly-border);\r\n  border-bottom: 1px solid var(--ly-border);\r\n  text-align: left;\r\n  vertical-align: top;\r\n  font-size: 15px;\r\n  line-height: 1.58;\r\n}\r\n\r\n.ly-tns-table th:last-child,\r\n.ly-tns-table td:last-child {\r\n  border-right: 0;\r\n}\r\n\r\n.ly-tns-table tbody tr:last-child td {\r\n  border-bottom: 0;\r\n}\r\n\r\n.ly-tns-table thead th {\r\n  background: var(--ly-blue);\r\n  color: #fff;\r\n  font-weight: 750;\r\n}\r\n\r\n.ly-tns-table tbody tr:nth-child(even) {\r\n  background: #f8fafc;\r\n}\r\n\r\n.ly-tns-table strong {\r\n  display: block;\r\n  margin-bottom: 3px;\r\n}\r\n\r\n\/* =========================================================\r\n   CALLOUTS\r\n   ========================================================= *\/\r\n\r\n.ly-tns-callout {\r\n  margin: 24px 0;\r\n  padding: 21px 23px;\r\n  border-radius: 13px;\r\n  font-size: 16px;\r\n  line-height: 1.68;\r\n}\r\n\r\n.ly-tns-callout h3 {\r\n  margin: 0 0 8px;\r\n  font-size: 20px;\r\n  line-height: 1.35;\r\n}\r\n\r\n.ly-tns-callout p:last-child {\r\n  margin-bottom: 0;\r\n}\r\n\r\n.ly-tns-callout.is-blue {\r\n  border: 1px solid var(--ly-blue-line);\r\n  background: var(--ly-blue-soft);\r\n}\r\n\r\n.ly-tns-callout.is-green {\r\n  border: 1px solid #bee5d0;\r\n  background: var(--ly-green-soft);\r\n}\r\n\r\n.ly-tns-callout.is-orange {\r\n  border: 1px solid #efd2a9;\r\n  background: var(--ly-orange-soft);\r\n}\r\n\r\n.ly-tns-callout.is-red {\r\n  border: 1px solid #efc6c2;\r\n  background: var(--ly-red-soft);\r\n}\r\n\r\n\/* =========================================================\r\n   CONNECTION STEPS\r\n   ========================================================= *\/\r\n\r\n.ly-tns-connection-grid {\r\n  display: grid;\r\n  grid-template-columns: repeat(2, minmax(0, 1fr));\r\n  gap: 15px;\r\n  margin-top: 25px;\r\n}\r\n\r\n.ly-tns-connection-card {\r\n  position: relative;\r\n  min-width: 0;\r\n  padding: 20px 20px 20px 64px;\r\n  border: 1px solid var(--ly-border);\r\n  border-radius: 12px;\r\n  background: #fff;\r\n}\r\n\r\n.ly-tns-connection-number {\r\n  position: absolute;\r\n  top: 20px;\r\n  left: 18px;\r\n  display: flex;\r\n  align-items: center;\r\n  justify-content: center;\r\n  width: 31px;\r\n  height: 31px;\r\n  border-radius: 8px;\r\n  background: var(--ly-blue);\r\n  color: #fff;\r\n  font-size: 14px;\r\n  font-weight: 800;\r\n}\r\n\r\n.ly-tns-connection-card h3 {\r\n  margin: 0 0 7px;\r\n  font-size: 18px;\r\n  line-height: 1.35;\r\n}\r\n\r\n.ly-tns-connection-card p {\r\n  margin: 0;\r\n  color: var(--ly-muted);\r\n  font-size: 14px;\r\n  line-height: 1.63;\r\n}\r\n\r\n\/* =========================================================\r\n   CHECK AND ERROR LISTS\r\n   ========================================================= *\/\r\n\r\n.ly-tns-check-list,\r\n.ly-tns-error-list {\r\n  display: grid;\r\n  gap: 11px;\r\n  margin: 22px 0 0;\r\n  padding: 0;\r\n  list-style: none;\r\n}\r\n\r\n.ly-tns-check-list li,\r\n.ly-tns-error-list li {\r\n  position: relative;\r\n  padding: 14px 16px 14px 49px;\r\n  border: 1px solid var(--ly-border);\r\n  border-radius: 10px;\r\n  background: #fff;\r\n  color: #38485c;\r\n  line-height: 1.62;\r\n}\r\n\r\n.ly-tns-check-list li::before,\r\n.ly-tns-error-list li::before {\r\n  position: absolute;\r\n  top: 15px;\r\n  left: 16px;\r\n  display: flex;\r\n  align-items: center;\r\n  justify-content: center;\r\n  width: 23px;\r\n  height: 23px;\r\n  border-radius: 50%;\r\n  font-size: 13px;\r\n  font-weight: 800;\r\n}\r\n\r\n.ly-tns-check-list li::before {\r\n  background: var(--ly-green-soft);\r\n  color: var(--ly-green);\r\n  content: \"\u2713\";\r\n}\r\n\r\n.ly-tns-error-list li::before {\r\n  background: var(--ly-red-soft);\r\n  color: var(--ly-red);\r\n  content: \"!\";\r\n}\r\n\r\n\/* =========================================================\r\n   ORDERING CARDS\r\n   ========================================================= *\/\r\n\r\n.ly-tns-card-grid {\r\n  display: grid;\r\n  grid-template-columns: repeat(3, minmax(0, 1fr));\r\n  gap: 17px;\r\n  margin-top: 25px;\r\n}\r\n\r\n.ly-tns-card {\r\n  min-width: 0;\r\n  padding: 22px;\r\n  border: 1px solid var(--ly-border);\r\n  border-radius: 13px;\r\n  background: #fff;\r\n  box-shadow: 0 8px 22px rgba(22, 49, 78, 0.05);\r\n}\r\n\r\n.ly-tns-card-label {\r\n  display: inline-flex;\r\n  margin-bottom: 12px;\r\n  padding: 5px 9px;\r\n  border-radius: 999px;\r\n  background: var(--ly-blue-soft);\r\n  color: var(--ly-blue);\r\n  font-size: 12px;\r\n  font-weight: 800;\r\n  line-height: 1.3;\r\n  letter-spacing: 0.04em;\r\n  text-transform: uppercase;\r\n}\r\n\r\n.ly-tns-card h3 {\r\n  margin: 0 0 9px;\r\n  font-size: 20px;\r\n  line-height: 1.35;\r\n}\r\n\r\n.ly-tns-card p {\r\n  margin: 0;\r\n  color: var(--ly-muted);\r\n  font-size: 15px;\r\n  line-height: 1.65;\r\n}\r\n\r\n\/* =========================================================\r\n   RFQ\r\n   ========================================================= *\/\r\n\r\n.ly-tns-rfq {\r\n  margin-top: 28px;\r\n  overflow: hidden;\r\n  border: 1px solid var(--ly-border);\r\n  border-radius: 14px;\r\n  background: #fff;\r\n  box-shadow: var(--ly-shadow);\r\n}\r\n\r\n.ly-tns-rfq-head {\r\n  padding: 19px 22px;\r\n  background: var(--ly-blue);\r\n  color: #fff;\r\n}\r\n\r\n.ly-tns-rfq-head h3 {\r\n  margin: 0 0 5px;\r\n  color: #fff;\r\n  font-size: 22px;\r\n  line-height: 1.35;\r\n}\r\n\r\n.ly-tns-rfq-head p {\r\n  margin: 0;\r\n  color: rgba(255, 255, 255, 0.84);\r\n  font-size: 14px;\r\n}\r\n\r\n.ly-tns-rfq pre {\r\n  max-width: 100%;\r\n  margin: 0;\r\n  padding: 23px;\r\n  overflow-x: auto;\r\n  background: #f7f9fc;\r\n  color: #26384d;\r\n  font-family: Consolas, Monaco, \"Courier New\", monospace;\r\n  font-size: 14px;\r\n  line-height: 1.72;\r\n  white-space: pre-wrap;\r\n  word-break: break-word;\r\n}\r\n\r\n\/* =========================================================\r\n   CTA\r\n   ========================================================= *\/\r\n\r\n.ly-tns-cta {\r\n  margin-top: 64px;\r\n  padding: 35px;\r\n  border-radius: 17px;\r\n  background: linear-gradient(135deg, #003d82 0%, #0061bb 100%);\r\n  color: #fff;\r\n  box-shadow: 0 18px 42px rgba(0, 72, 152, 0.22);\r\n}\r\n\r\n.ly-tns-cta-grid {\r\n  display: grid;\r\n  grid-template-columns: minmax(0, 1fr) auto;\r\n  gap: 28px;\r\n  align-items: center;\r\n}\r\n\r\n.ly-tns-cta h2 {\r\n  margin: 0 0 9px;\r\n  color: #fff;\r\n  font-size: 29px;\r\n  line-height: 1.28;\r\n}\r\n\r\n.ly-tns-cta p {\r\n  max-width: 730px;\r\n  margin: 0;\r\n  color: rgba(255, 255, 255, 0.86);\r\n  font-size: 16px;\r\n  line-height: 1.68;\r\n}\r\n\r\n.ly-tns-btn,\r\n.ly-tns-page .ly-tns-btn {\r\n  display: inline-flex !important;\r\n  align-items: center !important;\r\n  justify-content: center !important;\r\n  min-width: 240px;\r\n  min-height: 51px;\r\n  margin: 0;\r\n  padding: 13px 21px !important;\r\n  border: 2px solid #fff !important;\r\n  border-radius: 8px !important;\r\n  background: #fff !important;\r\n  box-shadow: none !important;\r\n  color: var(--ly-blue) !important;\r\n  cursor: pointer;\r\n  font-family: inherit !important;\r\n  font-size: 15px !important;\r\n  font-weight: 800 !important;\r\n  line-height: 1.3 !important;\r\n  text-decoration: none !important;\r\n  white-space: nowrap;\r\n  opacity: 1 !important;\r\n  visibility: visible !important;\r\n  appearance: none;\r\n  -webkit-appearance: none;\r\n}\r\n\r\n.ly-tns-btn span,\r\n.ly-tns-page .ly-tns-btn span,\r\n.ly-tns-page .ly-tns-btn .w-btn-label {\r\n  display: inline-block !important;\r\n  color: var(--ly-blue) !important;\r\n  font-size: inherit !important;\r\n  font-weight: inherit !important;\r\n  line-height: inherit !important;\r\n  white-space: nowrap !important;\r\n  opacity: 1 !important;\r\n  visibility: visible !important;\r\n}\r\n\r\n.ly-tns-btn:hover,\r\n.ly-tns-btn:focus {\r\n  background: #eaf3fe !important;\r\n  color: var(--ly-blue-dark) !important;\r\n  transform: translateY(-1px);\r\n}\r\n\r\n.ly-tns-btn:hover span,\r\n.ly-tns-btn:focus span {\r\n  color: var(--ly-blue-dark) !important;\r\n}\r\n\r\n\/* =========================================================\r\n   RELATED LINKS\r\n   ========================================================= *\/\r\n\r\n.ly-tns-related {\r\n  display: grid;\r\n  grid-template-columns: repeat(3, minmax(0, 1fr));\r\n  gap: 14px;\r\n  margin-top: 23px;\r\n}\r\n\r\n.ly-tns-related a {\r\n  display: block;\r\n  min-height: 100%;\r\n  padding: 18px;\r\n  border: 1px solid var(--ly-border);\r\n  border-radius: 10px;\r\n  background: #fff;\r\n  color: var(--ly-text);\r\n  font-size: 15px;\r\n  font-weight: 750;\r\n  line-height: 1.52;\r\n  text-decoration: none;\r\n}\r\n\r\n.ly-tns-related a:hover,\r\n.ly-tns-related a:focus {\r\n  border-color: var(--ly-blue);\r\n  color: var(--ly-blue);\r\n  box-shadow: 0 8px 18px rgba(0, 72, 152, 0.08);\r\n}\r\n\r\n\/* =========================================================\r\n   FAQ\r\n   ========================================================= *\/\r\n\r\n.ly-tns-faq {\r\n  display: grid;\r\n  gap: 11px;\r\n  margin-top: 24px;\r\n}\r\n\r\n.ly-tns-faq details {\r\n  overflow: hidden;\r\n  border: 1px solid var(--ly-border);\r\n  border-radius: 10px;\r\n  background: #fff;\r\n}\r\n\r\n.ly-tns-faq summary {\r\n  position: relative;\r\n  padding: 16px 50px 16px 18px;\r\n  color: var(--ly-text);\r\n  cursor: pointer;\r\n  font-size: 16px;\r\n  font-weight: 750;\r\n  line-height: 1.5;\r\n  list-style: none;\r\n}\r\n\r\n.ly-tns-faq summary::-webkit-details-marker {\r\n  display: none;\r\n}\r\n\r\n.ly-tns-faq summary::after {\r\n  position: absolute;\r\n  top: 50%;\r\n  right: 17px;\r\n  color: var(--ly-blue);\r\n  content: \"+\";\r\n  font-size: 23px;\r\n  font-weight: 500;\r\n  transform: translateY(-50%);\r\n}\r\n\r\n.ly-tns-faq details[open] summary::after {\r\n  content: \"\u2212\";\r\n}\r\n\r\n.ly-tns-faq-answer {\r\n  padding: 0 18px 17px;\r\n  color: var(--ly-muted);\r\n  font-size: 15px;\r\n  line-height: 1.67;\r\n}\r\n\r\n.ly-tns-faq-answer p:last-child {\r\n  margin-bottom: 0;\r\n}\r\n\r\n\/* =========================================================\r\n   REFERENCES\r\n   ========================================================= *\/\r\n\r\n.ly-tns-references {\r\n  margin-top: 23px;\r\n  padding: 24px 27px;\r\n  border: 1px solid var(--ly-border);\r\n  border-radius: 12px;\r\n  background: var(--ly-bg);\r\n}\r\n\r\n.ly-tns-references ol {\r\n  margin: 0;\r\n  padding-left: 22px;\r\n}\r\n\r\n.ly-tns-references li {\r\n  margin-bottom: 11px;\r\n  padding-left: 4px;\r\n  overflow-wrap: anywhere;\r\n  color: var(--ly-muted);\r\n  font-size: 13px;\r\n  line-height: 1.65;\r\n}\r\n\r\n.ly-tns-references li:last-child {\r\n  margin-bottom: 0;\r\n}\r\n\r\n.ly-tns-ref {\r\n  font-size: 0.75em;\r\n  vertical-align: super;\r\n}\r\n\r\n.ly-tns-ref a {\r\n  font-weight: 750;\r\n  text-decoration: none;\r\n}\r\n\r\n\/* =========================================================\r\n   RESPONSIVE \u2014 DESKTOP 1440\r\n   ========================================================= *\/\r\n\r\n@media screen and (max-width: 1440px) {\r\n  .ly-tns-shell {\r\n    max-width: 1140px;\r\n  }\r\n\r\n  .ly-tns-intro h2 {\r\n    font-size: 38px;\r\n  }\r\n\r\n  .ly-tns-figure {\r\n    margin-top: 30px;\r\n    margin-bottom: 30px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   RESPONSIVE \u2014 DESKTOP 1366\r\n   ========================================================= *\/\r\n\r\n@media screen and (max-width: 1366px) {\r\n  .ly-tns-shell {\r\n    max-width: 1100px;\r\n  }\r\n\r\n  .ly-tns-section {\r\n    margin-top: 61px;\r\n  }\r\n\r\n  .ly-tns-section > h2 {\r\n    font-size: 33px;\r\n  }\r\n\r\n  .ly-tns-intro h2 {\r\n    font-size: 37px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   RESPONSIVE \u2014 DESKTOP 1280\r\n   ========================================================= *\/\r\n\r\n@media screen and (max-width: 1280px) {\r\n  .ly-tns-shell {\r\n    width: calc(100% - 42px);\r\n    max-width: 1050px;\r\n  }\r\n\r\n  .ly-tns-intro h2 {\r\n    font-size: 36px;\r\n  }\r\n\r\n  .ly-tns-card {\r\n    padding: 20px;\r\n  }\r\n\r\n  .ly-tns-table th,\r\n  .ly-tns-table td {\r\n    padding: 14px 15px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   RESPONSIVE \u2014 TABLET 1024\r\n   ========================================================= *\/\r\n\r\n@media screen and (max-width: 1024px) {\r\n  .ly-tns-page {\r\n    font-size: 16px;\r\n  }\r\n\r\n  .ly-tns-shell {\r\n    width: calc(100% - 38px);\r\n    padding-bottom: 62px;\r\n  }\r\n\r\n  .ly-tns-intro h2 {\r\n    font-size: 34px;\r\n  }\r\n\r\n  .ly-tns-intro-text {\r\n    font-size: 18px;\r\n  }\r\n\r\n  .ly-tns-section > h2 {\r\n    font-size: 30px;\r\n  }\r\n\r\n  .ly-tns-card-grid {\r\n    grid-template-columns: repeat(2, minmax(0, 1fr));\r\n  }\r\n\r\n  .ly-tns-card-grid .ly-tns-card:last-child {\r\n    grid-column: 1 \/ -1;\r\n  }\r\n\r\n  .ly-tns-related {\r\n    grid-template-columns: repeat(2, minmax(0, 1fr));\r\n  }\r\n\r\n  .ly-tns-figure {\r\n    padding: 10px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   RESPONSIVE \u2014 TABLET 912\r\n   ========================================================= *\/\r\n\r\n@media screen and (max-width: 912px) {\r\n  .ly-tns-shell {\r\n    width: calc(100% - 34px);\r\n  }\r\n\r\n  .ly-tns-direct-answer {\r\n    padding: 25px;\r\n  }\r\n\r\n  .ly-tns-cta {\r\n    padding: 31px;\r\n  }\r\n\r\n  .ly-tns-cta-grid {\r\n    grid-template-columns: 1fr;\r\n  }\r\n\r\n  .ly-tns-btn,\r\n  .ly-tns-page .ly-tns-btn {\r\n    justify-self: start;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   RESPONSIVE \u2014 TABLET 820\r\n   ========================================================= *\/\r\n\r\n@media screen and (max-width: 820px) {\r\n  .ly-tns-intro h2 {\r\n    font-size: 32px;\r\n  }\r\n\r\n  .ly-tns-section {\r\n    margin-top: 55px;\r\n  }\r\n\r\n  .ly-tns-section > h2 {\r\n    font-size: 28px;\r\n  }\r\n\r\n  .ly-tns-answer-grid,\r\n  .ly-tns-connection-grid {\r\n    grid-template-columns: 1fr;\r\n  }\r\n\r\n  .ly-tns-toc ol {\r\n    grid-template-columns: 1fr;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   RESPONSIVE \u2014 TABLET 768\r\n   ========================================================= *\/\r\n\r\n@media screen and (max-width: 768px) {\r\n  .ly-tns-shell {\r\n    width: calc(100% - 30px);\r\n    padding-top: 18px;\r\n  }\r\n\r\n  .ly-tns-intro h2 {\r\n    font-size: 30px;\r\n  }\r\n\r\n  .ly-tns-intro-text,\r\n  .ly-tns-lead {\r\n    font-size: 17px;\r\n  }\r\n\r\n  .ly-tns-direct-answer {\r\n    padding: 22px;\r\n    border-left-width: 5px;\r\n  }\r\n\r\n  .ly-tns-direct-answer h2 {\r\n    font-size: 25px;\r\n  }\r\n\r\n  .ly-tns-card-grid,\r\n  .ly-tns-related {\r\n    grid-template-columns: 1fr;\r\n  }\r\n\r\n  .ly-tns-card-grid .ly-tns-card:last-child {\r\n    grid-column: auto;\r\n  }\r\n\r\n  .ly-tns-table th,\r\n  .ly-tns-table td {\r\n    padding: 13px 14px;\r\n  }\r\n\r\n  .ly-tns-figure {\r\n    padding: 9px;\r\n    border-radius: 13px;\r\n  }\r\n\r\n  .ly-tns-figure img {\r\n    border-radius: 8px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   RESPONSIVE \u2014 MOBILE 600\r\n   ========================================================= *\/\r\n\r\n@media screen and (max-width: 600px) {\r\n  .ly-tns-page {\r\n    font-size: 15.5px;\r\n    line-height: 1.68;\r\n  }\r\n\r\n  .ly-tns-shell {\r\n    width: calc(100% - 26px);\r\n    padding-bottom: 52px;\r\n  }\r\n\r\n  .ly-tns-intro h2 {\r\n    font-size: 28px;\r\n  }\r\n\r\n  .ly-tns-section {\r\n    margin-top: 49px;\r\n  }\r\n\r\n  .ly-tns-section > h2 {\r\n    font-size: 26px;\r\n  }\r\n\r\n  .ly-tns-section > h3 {\r\n    font-size: 21px;\r\n  }\r\n\r\n  .ly-tns-toc {\r\n    padding: 20px;\r\n  }\r\n\r\n  .ly-tns-cta {\r\n    padding: 26px;\r\n  }\r\n\r\n  .ly-tns-btn,\r\n  .ly-tns-page .ly-tns-btn {\r\n    width: 100%;\r\n    min-width: 0;\r\n    white-space: normal;\r\n  }\r\n\r\n  .ly-tns-btn span,\r\n  .ly-tns-page .ly-tns-btn span,\r\n  .ly-tns-page .ly-tns-btn .w-btn-label {\r\n    white-space: normal !important;\r\n    text-align: center;\r\n  }\r\n\r\n  .ly-tns-figure {\r\n    margin: 25px 0;\r\n    padding: 8px;\r\n  }\r\n\r\n  .ly-tns-figure figcaption {\r\n    padding-top: 11px;\r\n    font-size: 13px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   RESPONSIVE \u2014 MOBILE 540\r\n   ========================================================= *\/\r\n\r\n@media screen and (max-width: 540px) {\r\n  .ly-tns-shell {\r\n    width: calc(100% - 24px);\r\n  }\r\n\r\n  .ly-tns-intro h2 {\r\n    font-size: 27px;\r\n  }\r\n\r\n  .ly-tns-direct-answer {\r\n    padding: 19px;\r\n  }\r\n\r\n  .ly-tns-answer-item {\r\n    padding: 14px 13px 14px 43px;\r\n  }\r\n\r\n  .ly-tns-card {\r\n    padding: 19px;\r\n  }\r\n\r\n  .ly-tns-rfq pre {\r\n    padding: 19px;\r\n    font-size: 13px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   RESPONSIVE \u2014 MOBILE 480\r\n   ========================================================= *\/\r\n\r\n@media screen and (max-width: 480px) {\r\n  .ly-tns-shell {\r\n    width: calc(100% - 22px);\r\n  }\r\n\r\n  .ly-tns-intro h2 {\r\n    font-size: 26px;\r\n    line-height: 1.21;\r\n  }\r\n\r\n  .ly-tns-intro-text {\r\n    font-size: 16.5px;\r\n  }\r\n\r\n  .ly-tns-section > h2 {\r\n    font-size: 24px;\r\n  }\r\n\r\n  .ly-tns-direct-answer h2 {\r\n    font-size: 23px;\r\n  }\r\n\r\n  .ly-tns-callout {\r\n    padding: 18px;\r\n  }\r\n\r\n  .ly-tns-connection-card {\r\n    padding: 18px 17px 18px 59px;\r\n  }\r\n\r\n  .ly-tns-connection-number {\r\n    top: 18px;\r\n    left: 15px;\r\n  }\r\n\r\n  .ly-tns-cta {\r\n    margin-top: 53px;\r\n    padding: 23px;\r\n  }\r\n\r\n  .ly-tns-cta h2 {\r\n    font-size: 24px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   RESPONSIVE \u2014 MOBILE 430\r\n   ========================================================= *\/\r\n\r\n@media screen and (max-width: 430px) {\r\n  .ly-tns-page {\r\n    font-size: 15px;\r\n  }\r\n\r\n  .ly-tns-shell {\r\n    width: calc(100% - 20px);\r\n  }\r\n\r\n  .ly-tns-eyebrow {\r\n    font-size: 11.5px;\r\n    letter-spacing: 0.08em;\r\n  }\r\n\r\n  .ly-tns-intro h2 {\r\n    font-size: 25px;\r\n  }\r\n\r\n  .ly-tns-safety {\r\n    padding: 13px;\r\n  }\r\n\r\n  .ly-tns-direct-answer {\r\n    padding: 17px;\r\n  }\r\n\r\n  .ly-tns-table {\r\n    min-width: 760px;\r\n  }\r\n\r\n  .ly-tns-references {\r\n    padding: 19px;\r\n  }\r\n\r\n  .ly-tns-figure {\r\n    padding: 6px;\r\n  }\r\n\r\n  .ly-tns-figure figcaption {\r\n    padding: 10px 5px 2px;\r\n    font-size: 12.5px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   RESPONSIVE \u2014 MOBILE 414\r\n   ========================================================= *\/\r\n\r\n@media screen and (max-width: 414px) {\r\n  .ly-tns-intro h2 {\r\n    font-size: 24.5px;\r\n  }\r\n\r\n  .ly-tns-section > h2 {\r\n    font-size: 23.5px;\r\n  }\r\n\r\n  .ly-tns-direct-answer h2 {\r\n    font-size: 22px;\r\n  }\r\n\r\n  .ly-tns-toc {\r\n    padding: 17px;\r\n  }\r\n\r\n  .ly-tns-related a {\r\n    padding: 16px;\r\n  }\r\n\r\n  .ly-tns-figure {\r\n    border-radius: 10px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   RESPONSIVE \u2014 MOBILE 390\r\n   ========================================================= *\/\r\n\r\n@media screen and (max-width: 390px) {\r\n  .ly-tns-shell {\r\n    width: calc(100% - 18px);\r\n  }\r\n\r\n  .ly-tns-intro h2 {\r\n    font-size: 23.5px;\r\n  }\r\n\r\n  .ly-tns-intro-text {\r\n    font-size: 16px;\r\n  }\r\n\r\n  .ly-tns-section {\r\n    margin-top: 45px;\r\n  }\r\n\r\n  .ly-tns-rfq-head {\r\n    padding: 17px;\r\n  }\r\n\r\n  .ly-tns-figure {\r\n    margin: 21px 0;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   RESPONSIVE \u2014 MOBILE 375\r\n   ========================================================= *\/\r\n\r\n@media screen and (max-width: 375px) {\r\n  .ly-tns-intro h2 {\r\n    font-size: 23px;\r\n  }\r\n\r\n  .ly-tns-section > h2 {\r\n    font-size: 22.5px;\r\n  }\r\n\r\n  .ly-tns-direct-answer,\r\n  .ly-tns-card,\r\n  .ly-tns-callout {\r\n    padding: 15px;\r\n  }\r\n\r\n  .ly-tns-answer-item {\r\n    padding-left: 41px;\r\n  }\r\n\r\n  .ly-tns-answer-item::before {\r\n    left: 12px;\r\n  }\r\n\r\n  .ly-tns-cta {\r\n    padding: 20px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   RESPONSIVE \u2014 MOBILE 360\r\n   ========================================================= *\/\r\n\r\n@media screen and (max-width: 360px) {\r\n  .ly-tns-shell {\r\n    width: calc(100% - 16px);\r\n  }\r\n\r\n  .ly-tns-intro h2 {\r\n    font-size: 22.5px;\r\n  }\r\n\r\n  .ly-tns-faq summary {\r\n    padding: 14px 43px 14px 14px;\r\n    font-size: 15.5px;\r\n  }\r\n\r\n  .ly-tns-faq-answer {\r\n    padding: 0 14px 15px;\r\n  }\r\n\r\n  .ly-tns-figure {\r\n    padding: 5px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   RESPONSIVE \u2014 MOBILE 320\r\n   ========================================================= *\/\r\n\r\n@media screen and (max-width: 320px) {\r\n  .ly-tns-page {\r\n    font-size: 14.5px;\r\n  }\r\n\r\n  .ly-tns-shell {\r\n    width: calc(100% - 14px);\r\n  }\r\n\r\n  .ly-tns-intro h2 {\r\n    font-size: 21px;\r\n  }\r\n\r\n  .ly-tns-section > h2 {\r\n    font-size: 21px;\r\n  }\r\n\r\n  .ly-tns-direct-answer h2 {\r\n    font-size: 19.5px;\r\n  }\r\n\r\n  .ly-tns-eyebrow::before {\r\n    width: 20px;\r\n  }\r\n\r\n  .ly-tns-cta h2 {\r\n    font-size: 21px;\r\n  }\r\n\r\n  .ly-tns-btn,\r\n  .ly-tns-page .ly-tns-btn {\r\n    padding-right: 11px !important;\r\n    padding-left: 11px !important;\r\n    font-size: 14px !important;\r\n  }\r\n}\r\n<\/style>\r\n\r\n<div class=\"ly-tns-page\">\r\n  <article class=\"ly-tns-shell\">\r\n\r\n    <!-- =====================================================\r\n         INTRO\r\n         ===================================================== -->\r\n    <section class=\"ly-tns-intro\">\r\n      <div class=\"ly-tns-eyebrow\">\r\n        TN-S System \u00b7 Three-Phase Distribution \u00b7 OEM Selection\r\n      <\/div>\r\n\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\/pt\/tn-s-system-spd-wiring\/#tn-s-spd-wiring-at-a-glance\" >TN-S SPD Wiring at a Glance<\/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\/pt\/tn-s-system-spd-wiring\/#quick-answer-how-should-an-spd-be-wired-in-a-tn-s-system\" >Quick Answer: How Should an SPD Be Wired in a TN-S System?<\/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\/pt\/tn-s-system-spd-wiring\/#what-is-a-tn-s-earthing-system\" >What Is a TN-S Earthing System?<\/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\/pt\/tn-s-system-spd-wiring\/#l1-l2-l3-n-and-pe-in-a-tn-s-wiring-diagram\" >L1, L2, L3, N and PE in a TN-S Wiring Diagram<\/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\/pt\/tn-s-system-spd-wiring\/#how-to-wire-an-spd-in-a-three-phase-tn-s-panel\" >How to Wire an SPD in a Three-Phase TN-S Panel<\/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\/pt\/tn-s-system-spd-wiring\/#3p-vs-4p-vs-3pn-spd-for-a-tn-s-system\" >3P vs 4P vs 3P+N SPD for a TN-S System<\/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\/pt\/tn-s-system-spd-wiring\/#40-vs-31-protection-in-a-tn-s-system\" >4+0 vs 3+1 Protection in a TN-S System<\/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\/pt\/tn-s-system-spd-wiring\/#does-a-tn-s-system-need-n-pe-surge-protection\" >Does a TN-S System Need N-PE Surge Protection?<\/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\/pt\/tn-s-system-spd-wiring\/#tn-s-system-spd-selection-process\" >TN-S System SPD Selection Process<\/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\/pt\/tn-s-system-spd-wiring\/#parameters-to-confirm-before-ordering\" >Parameters to Confirm Before Ordering<\/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\/pt\/tn-s-system-spd-wiring\/#rcd-position-and-spd-backup-protection\" >RCD Position and SPD Backup Protection<\/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\/pt\/tn-s-system-spd-wiring\/#common-tn-s-spd-wiring-and-selection-errors\" >Common TN-S SPD Wiring and Selection Errors<\/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\/pt\/tn-s-system-spd-wiring\/#tn-s-spd-oem-and-bulk-ordering-checklist\" >TN-S SPD OEM and Bulk Ordering Checklist<\/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\/pt\/tn-s-system-spd-wiring\/#need-to-confirm-a-tn-s-spd-before-ordering\" >Need to confirm a TN-S SPD before ordering?<\/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\/pt\/tn-s-system-spd-wiring\/#related-technical-guides\" >Related Technical Guides<\/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\/pt\/tn-s-system-spd-wiring\/#tn-s-system-spd-wiring-faq\" >TN-S System SPD Wiring FAQ<\/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\/pt\/tn-s-system-spd-wiring\/#technical-references\" >Technical References<\/a><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"tn-s-spd-wiring-at-a-glance\"><\/span>TN-S SPD Wiring at a Glance<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p class=\"ly-tns-intro-text\">\r\n        In a three-phase TN-S system, the surge protective device is connected\r\n        in parallel with L1, L2, L3, N and PE according to the approved internal\r\n        circuit of the selected SPD. Neutral and protective earth remain separate\r\n        during normal operation.\r\n      <\/p>\r\n\r\n      <div class=\"ly-tns-direct-answer\">\r\n        <h2><span class=\"ez-toc-section\" id=\"quick-answer-how-should-an-spd-be-wired-in-a-tn-s-system\"><\/span>Quick Answer: How Should an SPD Be Wired in a TN-S System?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <p>\r\n          Where neutral is present, use a manufacturer-approved 4+0 \/ CT1 or\r\n          3+1 \/ CT2 arrangement. Connect the SPD close to the incoming busbars,\r\n          use the specified branch protection, and keep the SPD-to-PE connection\r\n          as short and direct as practicable. Do not select the device from pole\r\n          count alone.\r\n        <\/p>\r\n\r\n        <div class=\"ly-tns-answer-grid\">\r\n          <div class=\"ly-tns-answer-item\">\r\n            L1, L2, L3, N and PE remain separate conductors in the downstream\r\n            TN-S installation.\r\n          <\/div>\r\n\r\n          <div class=\"ly-tns-answer-item\">\r\n            A 3P SPD is normally considered only where no neutral conductor is\r\n            present or where the approved project design specifically requires it.\r\n          <\/div>\r\n\r\n          <div class=\"ly-tns-answer-item\">\r\n            A 4P device may use 4+0 \/ CT1, while a 3P+N device may use\r\n            3+1 \/ CT2. Check the internal circuit diagram.\r\n          <\/div>\r\n\r\n          <div class=\"ly-tns-answer-item\">\r\n            N-PE surge protection does not mean installing a permanent copper\r\n            link between the neutral and PE bars.\r\n          <\/div>\r\n        <\/div>\r\n      <\/div>\r\n\r\n      <figure class=\"ly-tns-figure is-primary\">\r\n        <img fetchpriority=\"high\"\r\n          src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/tn-s-system-spd-wiring-architecture.webp\"\r\n          alt=\"TN-S system SPD wiring architecture with separate L1 L2 L3 N and PE conductors\"\r\n          width=\"1600\"\r\n          height=\"900\"\r\n          loading=\"eager\"\r\n          decoding=\"async\"\r\n          fetchpriority=\"high\"\r\n        >\r\n        <figcaption>\r\n          <strong>Three-phase TN-S SPD wiring architecture:<\/strong>\r\n          the SPD is connected in parallel, N and PE remain separate, and the\r\n          PE connection is kept short and direct.\r\n        <\/figcaption>\r\n      <\/figure>\r\n\r\n      <div class=\"ly-tns-decision\">\r\n        <h3>Fast Selection by TN-S Panel Condition<\/h3>\r\n\r\n        <div class=\"ly-tns-table-wrap\">\r\n          <table class=\"ly-tns-table\">\r\n            <thead>\r\n              <tr>\r\n                <th>TN-S Panel Condition<\/th>\r\n                <th>Common Selection Direction<\/th>\r\n                <th>What the Buyer Must Confirm<\/th>\r\n              <\/tr>\r\n            <\/thead>\r\n\r\n            <tbody>\r\n              <tr>\r\n                <td>\r\n                  <strong>L1 \/ L2 \/ L3 without N<\/strong>\r\n                  Three-phase, three-wire circuit\r\n                <\/td>\r\n                <td>\r\n                  A project-specific 3P SPD may be used.\r\n                <\/td>\r\n                <td>\r\n                  Confirm that neutral is genuinely absent and check the exact\r\n                  product wiring diagram.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td>\r\n                  <strong>L1 \/ L2 \/ L3 \/ N \/ PE<\/strong>\r\n                  Project specifies CT1\r\n                <\/td>\r\n                <td>\r\n                  4P \/ 4+0 \/ CT1 may be selected.\r\n                <\/td>\r\n                <td>\r\n                  Confirm L-PE and N-PE protection modes, Uc, Up, TOV behaviour\r\n                  and permitted RCD position.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td>\r\n                  <strong>L1 \/ L2 \/ L3 \/ N \/ PE<\/strong>\r\n                  Project specifies CT2\r\n                <\/td>\r\n                <td>\r\n                  3P+N \/ 3+1 \/ CT2 may be selected.\r\n                <\/td>\r\n                <td>\r\n                  Confirm L-N protection, the N-PE component, I<sub>total<\/sub>,\r\n                  Up and manufacturer-approved TN-S application.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td>\r\n                  <strong>The enquiry only says \u201cfour-pole SPD\u201d<\/strong>\r\n                  Internal circuit not provided\r\n                <\/td>\r\n                <td>\r\n                  Do not approve the model yet.\r\n                <\/td>\r\n                <td>\r\n                  Request the single-line diagram, internal SPD circuit and\r\n                  required protection modes.\r\n                <\/td>\r\n              <\/tr>\r\n            <\/tbody>\r\n          <\/table>\r\n        <\/div>\r\n\r\n        <p class=\"ly-tns-table-note\">\r\n          The market descriptions \u201c4P\u201d and \u201c3P+N\u201d do not always provide enough\r\n          information to confirm the internal protection circuit.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"ly-tns-safety\">\r\n        <span class=\"ly-tns-safety-icon\">!<\/span>\r\n        <div>\r\n          <strong>Safety and scope:<\/strong>\r\n          Final wiring must follow the project single-line diagram, local\r\n          installation rules and the exact SPD manufacturer instructions.\r\n          Electrical installation work must be performed by qualified personnel.\r\n        <\/div>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <!-- =====================================================\r\n         CONTENTS\r\n         ===================================================== -->\r\n    <nav class=\"ly-tns-toc\" aria-label=\"TN-S SPD wiring guide contents\">\r\n      <div class=\"ly-tns-toc-title\">Contents<\/div>\r\n\r\n      <ol>\r\n        <li><a href=\"#what-is-tns\">What Is a TN-S System?<\/a><\/li>\r\n        <li><a href=\"#tns-conductors\">L1, L2, L3, N and PE<\/a><\/li>\r\n        <li><a href=\"#how-to-wire\">How to Wire the SPD<\/a><\/li>\r\n        <li><a href=\"#3p-4p-3pn\">3P vs 4P vs 3P+N<\/a><\/li>\r\n        <li><a href=\"#4plus0-3plus1\">4+0 vs 3+1<\/a><\/li>\r\n        <li><a href=\"#npe-protection\">N-PE Protection<\/a><\/li>\r\n        <li><a href=\"#selection-process\">Selection Process<\/a><\/li>\r\n        <li><a href=\"#parameters\">Parameters to Confirm<\/a><\/li>\r\n        <li><a href=\"#rcd-backup\">RCD and Backup Protection<\/a><\/li>\r\n        <li><a href=\"#wiring-errors\">Common Errors<\/a><\/li>\r\n        <li><a href=\"#oem-checklist\">OEM Ordering Checklist<\/a><\/li>\r\n        <li><a href=\"#faq\">FAQ<\/a><\/li>\r\n      <\/ol>\r\n    <\/nav>\r\n\r\n    <!-- =====================================================\r\n         WHAT IS TN-S\r\n         ===================================================== -->\r\n    <section class=\"ly-tns-section\" id=\"what-is-tns\">\r\n      <h2><span class=\"ez-toc-section\" id=\"what-is-a-tn-s-earthing-system\"><\/span>What Is a TN-S Earthing System?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p class=\"ly-tns-lead\">\r\n        In a TN-S system, the source neutral is earthed, while the neutral conductor\r\n        and protective earth conductor remain separate from the source to the loads.\r\n      <\/p>\r\n\r\n      <p>\r\n        A typical three-phase TN-S supply uses five conductors: L1, L2, L3, N and PE.\r\n        The neutral carries normal return current from phase-to-neutral loads. The PE\r\n        conductor provides protective bonding and the fault-current path and should\r\n        not carry normal load current.\r\n      <\/p>\r\n\r\n      <p>\r\n        This differs from TN-C, where neutral and protective functions are combined\r\n        in a PEN conductor, and TN-C-S, where a PEN conductor is separated into N and\r\n        PE at a defined point.\r\n      <\/p>\r\n\r\n      <div class=\"ly-tns-callout is-orange\">\r\n        <h3>Do not identify TN-S from conductor colours alone<\/h3>\r\n        <p>\r\n          Colours can vary by country, installation age and local practice. Confirm\r\n          the system from the project single-line diagram, supply documentation and\r\n          the actual N\/PE arrangement.\r\n        <\/p>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <!-- =====================================================\r\n         CONDUCTORS\r\n         ===================================================== -->\r\n    <section class=\"ly-tns-section\" id=\"tns-conductors\">\r\n      <h2><span class=\"ez-toc-section\" id=\"l1-l2-l3-n-and-pe-in-a-tn-s-wiring-diagram\"><\/span>L1, L2, L3, N and PE in a TN-S Wiring Diagram<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <div class=\"ly-tns-table-wrap\">\r\n        <table class=\"ly-tns-table\">\r\n          <thead>\r\n            <tr>\r\n              <th>Conductor<\/th>\r\n              <th>Normal Function<\/th>\r\n              <th>SPD Selection Meaning<\/th>\r\n              <th>Common Mistake<\/th>\r\n            <\/tr>\r\n          <\/thead>\r\n\r\n          <tbody>\r\n            <tr>\r\n              <td>\r\n                <strong>L1 \/ L2 \/ L3<\/strong>\r\n                Phase conductors\r\n              <\/td>\r\n              <td>\r\n                Carry the three-phase supply voltage and load current.\r\n              <\/td>\r\n              <td>\r\n                Each phase requires the protection mode defined by the project\r\n                and SPD circuit.\r\n              <\/td>\r\n              <td>\r\n                Choosing a 3P SPD merely because the supply is described as\r\n                \u201cthree-phase.\u201d\r\n              <\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td>\r\n                <strong>N<\/strong>\r\n                Neutral conductor\r\n              <\/td>\r\n              <td>\r\n                Carries return current from phase-to-neutral loads.\r\n              <\/td>\r\n              <td>\r\n                Confirm whether the device provides L-N protection, N-PE\r\n                protection, or a combination of both.\r\n              <\/td>\r\n              <td>\r\n                Assuming all four-module SPDs protect neutral in the same way.\r\n              <\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td>\r\n                <strong>PE<\/strong>\r\n                Protective earth\r\n              <\/td>\r\n              <td>\r\n                Provides protective bonding and the surge discharge path.\r\n              <\/td>\r\n              <td>\r\n                The SPD-to-PE conductor should be short, direct and sized\r\n                according to the product instructions.\r\n              <\/td>\r\n              <td>\r\n                Mounting the SPD far from the PE bar and using a long looped lead.\r\n              <\/td>\r\n            <\/tr>\r\n          <\/tbody>\r\n        <\/table>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <!-- =====================================================\r\n         HOW TO WIRE\r\n         ===================================================== -->\r\n    <section class=\"ly-tns-section\" id=\"how-to-wire\">\r\n      <h2><span class=\"ez-toc-section\" id=\"how-to-wire-an-spd-in-a-three-phase-tn-s-panel\"><\/span>How to Wire an SPD in a Three-Phase TN-S Panel<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p class=\"ly-tns-lead\">\r\n        The SPD is connected in parallel with the incoming supply. Normal load\r\n        current does not pass through the SPD.\r\n      <\/p>\r\n\r\n      <div class=\"ly-tns-connection-grid\">\r\n        <div class=\"ly-tns-connection-card\">\r\n          <span class=\"ly-tns-connection-number\">1<\/span>\r\n          <h3>Confirm the supply arrangement<\/h3>\r\n          <p>\r\n            Verify L1, L2, L3, N and PE from the single-line diagram and confirm\r\n            that the system is TN-S at the SPD installation point.\r\n          <\/p>\r\n        <\/div>\r\n\r\n        <div class=\"ly-tns-connection-card\">\r\n          <span class=\"ly-tns-connection-number\">2<\/span>\r\n          <h3>Connect the SPD in parallel<\/h3>\r\n          <p>\r\n            Take the required phase and neutral connections from the incoming\r\n            conductors or busbars according to the SPD terminal diagram.\r\n          <\/p>\r\n        <\/div>\r\n\r\n        <div class=\"ly-tns-connection-card\">\r\n          <span class=\"ly-tns-connection-number\">3<\/span>\r\n          <h3>Install the specified branch protection<\/h3>\r\n          <p>\r\n            Use the fuse, MCB or other backup protection stated in the SPD\r\n            datasheet after checking the available short-circuit current.\r\n          <\/p>\r\n        <\/div>\r\n\r\n        <div class=\"ly-tns-connection-card\">\r\n          <span class=\"ly-tns-connection-number\">4<\/span>\r\n          <h3>Connect directly to the PE bar<\/h3>\r\n          <p>\r\n            Keep the earth path short, direct and free from unnecessary loops\r\n            or bends that increase inductive voltage.\r\n          <\/p>\r\n        <\/div>\r\n\r\n        <div class=\"ly-tns-connection-card\">\r\n          <span class=\"ly-tns-connection-number\">5<\/span>\r\n          <h3>Keep N and PE separate<\/h3>\r\n          <p>\r\n            Do not add a permanent copper link between the neutral bar and PE\r\n            bar in the downstream TN-S distribution board.\r\n          <\/p>\r\n        <\/div>\r\n\r\n        <div class=\"ly-tns-connection-card\">\r\n          <span class=\"ly-tns-connection-number\">6<\/span>\r\n          <h3>Complete the panel verification<\/h3>\r\n          <p>\r\n            Check terminal torque, lead length, backup protection, remote contact,\r\n            replacement module and the final approved drawing.\r\n          <\/p>\r\n        <\/div>\r\n      <\/div>\r\n\r\n      <div class=\"ly-tns-callout is-blue\">\r\n        <h3>Installation dimensions are product-specific<\/h3>\r\n        <p>\r\n          Do not copy terminal positions, conductor sizes or backup-device ratings\r\n          from a generic internet diagram. Use the exact installation instructions\r\n          for the ordered SPD model.\r\n        <\/p>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <!-- =====================================================\r\n         3P VS 4P VS 3P+N\r\n         ===================================================== -->\r\n    <section class=\"ly-tns-section\" id=\"3p-4p-3pn\">\r\n      <h2><span class=\"ez-toc-section\" id=\"3p-vs-4p-vs-3pn-spd-for-a-tn-s-system\"><\/span>3P vs 4P vs 3P+N SPD for a TN-S System<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p class=\"ly-tns-lead\">\r\n        Pole count describes the physical arrangement. It does not fully define\r\n        the internal surge protection paths.\r\n      <\/p>\r\n\r\n      <div class=\"ly-tns-table-wrap\">\r\n        <table class=\"ly-tns-table\">\r\n          <thead>\r\n            <tr>\r\n              <th>Market Description<\/th>\r\n              <th>Common Circuit Logic<\/th>\r\n              <th>Possible TN-S Use<\/th>\r\n              <th>Buyer Confirmation<\/th>\r\n            <\/tr>\r\n          <\/thead>\r\n\r\n          <tbody>\r\n            <tr>\r\n              <td>\r\n                <strong>3P SPD<\/strong>\r\n                Three-pole device\r\n              <\/td>\r\n              <td>\r\n                Protects three phase conductors without a dedicated neutral path.\r\n              <\/td>\r\n              <td>\r\n                A three-phase three-wire circuit or an approved project-specific design.\r\n              <\/td>\r\n              <td>\r\n                Confirm that neutral is absent at the SPD location.\r\n              <\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td>\r\n                <strong>4P SPD<\/strong>\r\n                Four-pole device\r\n              <\/td>\r\n              <td>\r\n                Often uses 4+0 \/ CT1, with L1, L2, L3 and N protected toward PE.\r\n              <\/td>\r\n              <td>\r\n                May be suitable where the manufacturer approves the device for TN-S.\r\n              <\/td>\r\n              <td>\r\n                Confirm the circuit symbol, protection modes, Uc, Up, TOV behaviour\r\n                and RCD arrangement.\r\n              <\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td>\r\n                <strong>3P+N SPD<\/strong>\r\n                Three phases plus neutral\r\n              <\/td>\r\n              <td>\r\n                Often uses 3+1 \/ CT2, with L-N protection plus a separate N-PE path.\r\n              <\/td>\r\n              <td>\r\n                Commonly available for TN-S systems.\r\n              <\/td>\r\n              <td>\r\n                Confirm the N-PE component, I<sub>total<\/sub>, Up and the exact\r\n                certified model.\r\n              <\/td>\r\n            <\/tr>\r\n          <\/tbody>\r\n        <\/table>\r\n      <\/div>\r\n\r\n      <div class=\"ly-tns-callout is-blue\">\r\n        <h3>This page is about TN-S wiring, not only product comparison<\/h3>\r\n        <p>\r\n          For a deeper comparison of product structures, see the\r\n          <a\r\n            href=\"https:\/\/www.cnspd.com\/3pn-spd-vs-4p-spd\/\"\r\n            target=\"_blank\"\r\n            rel=\"noopener\"\r\n          >3P+N SPD vs 4P SPD guide<\/a>.\r\n          This TN-S page focuses on how system type, conductor arrangement and\r\n          installation conditions affect the final wiring decision.\r\n        <\/p>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <!-- =====================================================\r\n         4+0 VS 3+1\r\n         ===================================================== -->\r\n    <section class=\"ly-tns-section\" id=\"4plus0-3plus1\">\r\n      <h2><span class=\"ez-toc-section\" id=\"40-vs-31-protection-in-a-tn-s-system\"><\/span>4+0 vs 3+1 Protection in a TN-S System<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p class=\"ly-tns-lead\">\r\n        Both protection arrangements may be available for TN-S systems, but they\r\n        create different surge paths.\r\n        <sup class=\"ly-tns-ref\"><a href=\"#ref-3\">[3]<\/a><\/sup>\r\n      <\/p>\r\n\r\n      <figure class=\"ly-tns-figure is-primary\">\r\n        <img loading=\"lazy\"\r\n          src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/tn-s-spd-4plus0-vs-3plus1-comparison.webp\"\r\n          alt=\"4 plus 0 vs 3 plus 1 SPD protection paths for a three-phase TN-S system\"\r\n          width=\"1600\"\r\n          height=\"900\"\r\n          loading=\"lazy\"\r\n          decoding=\"async\"\r\n        >\r\n        <figcaption>\r\n          <strong>4+0 \/ CT1 versus 3+1 \/ CT2:<\/strong>\r\n          check the internal protection circuit instead of relying only on the\r\n          number of poles or modules.\r\n        <\/figcaption>\r\n      <\/figure>\r\n\r\n      <div class=\"ly-tns-table-wrap\">\r\n        <table class=\"ly-tns-table\">\r\n          <thead>\r\n            <tr>\r\n              <th>Comparison<\/th>\r\n              <th>4+0 \/ X+0 \/ CT1<\/th>\r\n              <th>3+1 \/ X+1 \/ CT2<\/th>\r\n            <\/tr>\r\n          <\/thead>\r\n\r\n          <tbody>\r\n            <tr>\r\n              <td><strong>Phase protection path<\/strong><\/td>\r\n              <td>Commonly L1-PE, L2-PE and L3-PE<\/td>\r\n              <td>Commonly L1-N, L2-N and L3-N<\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td><strong>Neutral protection path<\/strong><\/td>\r\n              <td>N-PE protection element<\/td>\r\n              <td>Dedicated N-PE switching path<\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td><strong>Typical market description<\/strong><\/td>\r\n              <td>4P SPD<\/td>\r\n              <td>3P+N SPD<\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td><strong>Main purchasing check<\/strong><\/td>\r\n              <td>\r\n                L-PE and N-PE modes, TOV behaviour, Uc, Up and installation position\r\n              <\/td>\r\n              <td>\r\n                L-N mode, N-PE technology, I<sub>total<\/sub>, combined Up and\r\n                installation position\r\n              <\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td><strong>Can it be used in TN-S?<\/strong><\/td>\r\n              <td>\r\n                Yes, when approved by the manufacturer and project specification\r\n              <\/td>\r\n              <td>\r\n                Yes, when approved by the manufacturer and project specification\r\n              <\/td>\r\n            <\/tr>\r\n          <\/tbody>\r\n        <\/table>\r\n      <\/div>\r\n\r\n      <div class=\"ly-tns-callout is-green\">\r\n        <h3>There is no universal winner<\/h3>\r\n        <p>\r\n          The correct arrangement depends on the project specification, SPD type,\r\n          protection modes, voltage protection level, TOV performance, RCD\r\n          coordination, lightning-current duty and the manufacturer-approved\r\n          application.\r\n        <\/p>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <!-- =====================================================\r\n         N-PE\r\n         ===================================================== -->\r\n    <section class=\"ly-tns-section\" id=\"npe-protection\">\r\n      <h2><span class=\"ez-toc-section\" id=\"does-a-tn-s-system-need-n-pe-surge-protection\"><\/span>Does a TN-S System Need N-PE Surge Protection?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        Where neutral is present, the selected SPD assembly normally requires a\r\n        clearly defined neutral-related surge protection arrangement. Depending\r\n        on the circuit, this may be part of a 4+0 \/ CT1 or 3+1 \/ CT2 design.\r\n      <\/p>\r\n\r\n      <p>\r\n        In a CT1 device, N may have a protection path toward PE. In a CT2 device,\r\n        the phase protection normally operates from L to N, with a separate N-PE\r\n        switching path.\r\n        <sup class=\"ly-tns-ref\"><a href=\"#ref-4\">[4]<\/a><\/sup>\r\n      <\/p>\r\n\r\n      <div class=\"ly-tns-callout is-red\">\r\n        <h3>N-PE surge protection is not a permanent N-PE connection<\/h3>\r\n        <p>\r\n          The SPD protection element is designed to respond under defined\r\n          overvoltage conditions. It does not justify installing a permanent\r\n          neutral-to-earth bridge in a downstream TN-S board.\r\n        <\/p>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <!-- =====================================================\r\n         SELECTION PROCESS\r\n         ===================================================== -->\r\n    <section class=\"ly-tns-section\" id=\"selection-process\">\r\n      <h2><span class=\"ez-toc-section\" id=\"tn-s-system-spd-selection-process\"><\/span>TN-S System SPD Selection Process<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <ul class=\"ly-tns-check-list\">\r\n        <li>\r\n          <strong>Confirm the earthing system.<\/strong>\r\n          Verify that the protection point is genuinely TN-S and not TN-C-S\r\n          before or after an uncertain PEN separation point.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>Confirm the conductor arrangement.<\/strong>\r\n          Check whether neutral is present at the SPD location.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>Select Type 1, Type 2 or Type 1+2.<\/strong>\r\n          Base this on lightning exposure, external lightning protection,\r\n          incoming supply and project risk\u2014not only the earthing system.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>Confirm CT1 or CT2.<\/strong>\r\n          Review the internal circuit diagram and protection-mode table.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>Check voltage and discharge ratings.<\/strong>\r\n          Confirm Uc, Up, In, Imax, Iimp and I<sub>total<\/sub> where applicable.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>Check short-circuit coordination.<\/strong>\r\n          Verify Isccr, prospective short-circuit current and permitted backup protection.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>Check the installation position.<\/strong>\r\n          Confirm conductor lengths, RCD coordination, PE connection and panel layout.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>Check the exact certificate scope.<\/strong>\r\n          Ensure the ordered model, voltage and configuration are covered.\r\n        <\/li>\r\n      <\/ul>\r\n    <\/section>\r\n\r\n    <!-- =====================================================\r\n         PARAMETERS\r\n         ===================================================== -->\r\n    <section class=\"ly-tns-section\" id=\"parameters\">\r\n      <h2><span class=\"ez-toc-section\" id=\"parameters-to-confirm-before-ordering\"><\/span>Parameters to Confirm Before Ordering<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <div class=\"ly-tns-table-wrap\">\r\n        <table class=\"ly-tns-table\">\r\n          <thead>\r\n            <tr>\r\n              <th>Parameter<\/th>\r\n              <th>Why It Matters<\/th>\r\n              <th>Buyer Question<\/th>\r\n            <\/tr>\r\n          <\/thead>\r\n\r\n          <tbody>\r\n            <tr>\r\n              <td><strong>Uo \/ Un<\/strong>System voltage<\/td>\r\n              <td>Defines the normal phase-neutral and phase-phase voltage.<\/td>\r\n              <td>Is the system 230\/400 V, 240\/415 V or another voltage?<\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td><strong>Uc<\/strong>Maximum continuous voltage<\/td>\r\n              <td>Must suit the continuous voltage and expected system conditions.<\/td>\r\n              <td>Is the Uc approved for the exact TN-S system and market?<\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td><strong>Up<\/strong>Voltage protection level<\/td>\r\n              <td>Indicates the limiting performance under the defined test condition.<\/td>\r\n              <td>What are the relevant L-N, L-PE and N-PE protection levels?<\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td><strong>In \/ Imax<\/strong>Type 2 discharge ratings<\/td>\r\n              <td>Describe nominal and maximum impulse-current performance.<\/td>\r\n              <td>Are the stated ratings per mode, per pole or for the assembly?<\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td><strong>Iimp<\/strong>Type 1 impulse current<\/td>\r\n              <td>Required where lightning-current duty is specified.<\/td>\r\n              <td>What is Iimp per mode and for the complete multipole assembly?<\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td><strong>I<sub>total<\/sub><\/strong>Total discharge current<\/td>\r\n              <td>Important for multipole Type 1 devices and N-PE discharge paths.<\/td>\r\n              <td>Can the N-PE path handle the required total current?<\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td><strong>Isccr \/ Isc<\/strong>Short-circuit capability<\/td>\r\n              <td>Must coordinate with the available fault current at the panel.<\/td>\r\n              <td>What backup protection is required at the stated fault level?<\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td><strong>CT1 \/ CT2<\/strong>Protection circuit<\/td>\r\n              <td>Defines the internal protection paths.<\/td>\r\n              <td>Can the supplier provide the internal circuit diagram?<\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td><strong>Remote contact<\/strong>Status signalling<\/td>\r\n              <td>Allows monitoring through PLC, BMS or alarm systems.<\/td>\r\n              <td>What are the NO\/NC logic and contact ratings?<\/td>\r\n            <\/tr>\r\n          <\/tbody>\r\n        <\/table>\r\n      <\/div>\r\n\r\n      <p>\r\n        IEC 61643-11 covers requirements and test methods for SPDs connected to\r\n        AC low-voltage power systems. Installation and selection must also follow\r\n        the applicable electrical installation requirements.\r\n        <sup class=\"ly-tns-ref\"><a href=\"#ref-1\">[1]<\/a><\/sup>\r\n        <sup class=\"ly-tns-ref\"><a href=\"#ref-2\">[2]<\/a><\/sup>\r\n      <\/p>\r\n    <\/section>\r\n\r\n    <!-- =====================================================\r\n         RCD AND BACKUP\r\n         ===================================================== -->\r\n    <section class=\"ly-tns-section\" id=\"rcd-backup\">\r\n      <h2><span class=\"ez-toc-section\" id=\"rcd-position-and-spd-backup-protection\"><\/span>RCD Position and SPD Backup Protection<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        RCD coordination cannot be decided from the labels \u201cCT1\u201d or \u201cCT2\u201d alone.\r\n        Check the SPD\u2019s TOV behaviour, N-PE technology, permitted installation\r\n        position and the exact manufacturer wiring instructions.\r\n      <\/p>\r\n\r\n      <p>\r\n        Some products have specific requirements for installation upstream or\r\n        downstream of residual-current protection. The final position must also\r\n        comply with the local installation rules and project design.\r\n        <sup class=\"ly-tns-ref\"><a href=\"#ref-4\">[4]<\/a><\/sup>\r\n      <\/p>\r\n\r\n      <div class=\"ly-tns-callout is-orange\">\r\n        <h3>Do not specify a universal backup breaker<\/h3>\r\n        <p>\r\n          The backup fuse or circuit breaker must be selected from the SPD\r\n          datasheet after checking the maximum permitted backup protection,\r\n          conductor size, prospective short-circuit current and selectivity.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <ul class=\"ly-tns-check-list\">\r\n        <li>Confirm the manufacturer\u2019s maximum permitted backup protection.<\/li>\r\n        <li>Check the prospective short-circuit current at the installation point.<\/li>\r\n        <li>Confirm Isccr or the stated short-circuit coordination arrangement.<\/li>\r\n        <li>Check selectivity with upstream protective devices.<\/li>\r\n        <li>Verify the required means of isolation and maintenance access.<\/li>\r\n      <\/ul>\r\n    <\/section>\r\n\r\n    <!-- =====================================================\r\n         ERRORS\r\n         ===================================================== -->\r\n    <section class=\"ly-tns-section\" id=\"wiring-errors\">\r\n      <h2><span class=\"ez-toc-section\" id=\"common-tn-s-spd-wiring-and-selection-errors\"><\/span>Common TN-S SPD Wiring and Selection Errors<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <ul class=\"ly-tns-error-list\">\r\n        <li>\r\n          <strong>Choosing 3P only because the supply is three-phase.<\/strong>\r\n          A TN-S panel containing neutral loads may require a neutral-related\r\n          protection path.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>Treating 4P and 3P+N as identical.<\/strong>\r\n          Similar module counts can contain different protection circuits.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>Describing L-PE paths as a conventional 3+1 circuit.<\/strong>\r\n          A conventional CT2 arrangement normally uses L-N paths plus N-PE.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>Reconnecting N and PE downstream.<\/strong>\r\n          Neutral and protective earth must remain separate in the TN-S installation.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>Using long SPD conductors.<\/strong>\r\n          Added inductance increases the effective voltage seen by the protected equipment.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>Using a generic backup-device rating.<\/strong>\r\n          Backup protection must match the exact SPD and panel fault level.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>Selecting Type 1 or Type 2 only from the earthing system.<\/strong>\r\n          The SPD type depends on lightning exposure, supply and installation level.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>Checking only Imax.<\/strong>\r\n          Uc, Up, In, Iimp, I<sub>total<\/sub>, Isccr and protection modes also matter.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>Approving a certificate without checking the model scope.<\/strong>\r\n          Confirm the exact voltage and configuration listed in the certificate.\r\n        <\/li>\r\n      <\/ul>\r\n    <\/section>\r\n\r\n    <!-- =====================================================\r\n         OEM CHECKLIST\r\n         ===================================================== -->\r\n    <section class=\"ly-tns-section\" id=\"oem-checklist\">\r\n      <h2><span class=\"ez-toc-section\" id=\"tn-s-spd-oem-and-bulk-ordering-checklist\"><\/span>TN-S SPD OEM and Bulk Ordering Checklist<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p class=\"ly-tns-lead\">\r\n        Send complete system and project information before requesting a final\r\n        model, sample or bulk-order price.\r\n      <\/p>\r\n\r\n      <figure class=\"ly-tns-figure\">\r\n        <img loading=\"lazy\"\r\n          src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/tn-s-spd-oem-ordering-checklist.webp\"\r\n          alt=\"TN-S system SPD selection and OEM ordering checklist for panel builders\"\r\n          width=\"1600\"\r\n          height=\"900\"\r\n          loading=\"lazy\"\r\n          decoding=\"async\"\r\n        >\r\n        <figcaption>\r\n          <strong>TN-S SPD OEM ordering checklist:<\/strong>\r\n          confirm the electrical system, internal circuit, installation conditions,\r\n          certificate scope and private-label requirements.\r\n        <\/figcaption>\r\n      <\/figure>\r\n\r\n      <div class=\"ly-tns-card-grid\">\r\n        <div class=\"ly-tns-card\">\r\n          <span class=\"ly-tns-card-label\">System<\/span>\r\n          <h3>Electrical Information<\/h3>\r\n          <p>\r\n            TN-S confirmation, conductor arrangement, Uo\/Un, frequency,\r\n            installation point and prospective short-circuit current.\r\n          <\/p>\r\n        <\/div>\r\n\r\n        <div class=\"ly-tns-card\">\r\n          <span class=\"ly-tns-card-label\">Protection<\/span>\r\n          <h3>SPD Configuration<\/h3>\r\n          <p>\r\n            Type 1, Type 2 or Type 1+2; CT1 or CT2; Uc, Up, In, Imax,\r\n            Iimp, I<sub>total<\/sub> and backup protection.\r\n          <\/p>\r\n        <\/div>\r\n\r\n        <div class=\"ly-tns-card\">\r\n          <span class=\"ly-tns-card-label\">OEM<\/span>\r\n          <h3>Commercial Requirements<\/h3>\r\n          <p>\r\n            Exact model, quantity, sample approval, logo, label, packaging,\r\n            certificate scope and replacement-module requirement.\r\n          <\/p>\r\n        <\/div>\r\n      <\/div>\r\n\r\n      <div class=\"ly-tns-rfq\">\r\n        <div class=\"ly-tns-rfq-head\">\r\n          <h3>Copy-Ready TN-S SPD RFQ Template<\/h3>\r\n          <p>Replace the bracketed information before sending it to the supplier.<\/p>\r\n        <\/div>\r\n\r\n        <pre>Application: [Main distribution board \/ sub-distribution board \/ control panel]\r\nEarthing system: TN-S\r\nSupply conductors: [L1 \/ L2 \/ L3 \/ N \/ PE]\r\nSystem voltage: [___ V phase-to-phase \/ ___ V phase-to-neutral]\r\nFrequency: [50 \/ 60 Hz]\r\nNeutral available at SPD point: [Yes \/ No]\r\nProspective short-circuit current: [___ kA]\r\n\r\nRequired SPD type: [Type 1 \/ Type 2 \/ Type 1+2]\r\nRequired protection circuit: [CT1 \/ 4+0] or [CT2 \/ 3+1]\r\nRequired Uc: [___ V AC]\r\nRequired Up: [___ kV]\r\nRequired In \/ Imax: [___ kA \/ ___ kA]\r\nRequired Iimp \/ Itotal: [___ kA \/ ___ kA]\r\nBackup protection: [Please recommend from the exact datasheet]\r\n\r\nRCD position or project requirement: [___]\r\nRemote indication: [Required \/ Not required]\r\nPluggable module: [Required \/ Optional]\r\nCertificate required: [IEC \/ EN \/ T\u00dcV \/ CB \/ CE \/ project-specific]\r\nOEM logo and label: [Yes \/ No]\r\nPackaging language: [___]\r\nEstimated quantity: [___ units]\r\nRequired delivery date: [___]\r\n\r\nPlease provide:\r\n1. Exact model number\r\n2. Internal protection circuit\r\n3. Wiring diagram\r\n4. Datasheet\r\n5. Backup protection requirement\r\n6. Certificate and model scope\r\n7. Product and label drawing\r\n8. Sample and bulk-order lead time<\/pre>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <!-- =====================================================\r\n         CTA\r\n         ===================================================== -->\r\n    <section class=\"ly-tns-cta\">\r\n      <div class=\"ly-tns-cta-grid\">\r\n        <div>\r\n          <h2><span class=\"ez-toc-section\" id=\"need-to-confirm-a-tn-s-spd-before-ordering\"><\/span>Need to confirm a TN-S SPD before ordering?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n          <p>\r\n            Send LEEYEE your single-line diagram, system voltage, required SPD type,\r\n            short-circuit level and preferred protection circuit. We can help confirm\r\n            the model, wiring logic, backup protection and OEM requirements.\r\n          <\/p>\r\n        <\/div>\r\n\r\n        <button\r\n          type=\"button\"\r\n          class=\"ly-tns-btn leeyee-site-popup-btn\"\r\n          aria-label=\"Request a TN-S SPD recommendation\"\r\n        >\r\n          <span class=\"w-btn-label\">\r\n            Request TN-S SPD Recommendation\r\n          <\/span>\r\n        <\/button>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <!-- =====================================================\r\n         RELATED\r\n         ===================================================== -->\r\n    <section class=\"ly-tns-section\">\r\n      <h2><span class=\"ez-toc-section\" id=\"related-technical-guides\"><\/span>Related Technical Guides<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <div class=\"ly-tns-related\">\r\n        <a\r\n          href=\"https:\/\/www.cnspd.com\/three-phase-spd-wiring-diagram\/\"\r\n          target=\"_blank\"\r\n          rel=\"noopener\"\r\n        >\r\n          Three-Phase SPD Wiring Diagram Guide\r\n        <\/a>\r\n\r\n        <a\r\n          href=\"https:\/\/www.cnspd.com\/3pn-spd-vs-4p-spd\/\"\r\n          target=\"_blank\"\r\n          rel=\"noopener\"\r\n        >\r\n          3P+N SPD vs 4P SPD\r\n        <\/a>\r\n\r\n        <a\r\n          href=\"https:\/\/www.cnspd.com\/tt-system-spd\/\"\r\n          target=\"_blank\"\r\n          rel=\"noopener\"\r\n        >\r\n          TT System SPD and 3+1 Wiring Guide\r\n        <\/a>\r\n\r\n        <a\r\n          href=\"https:\/\/www.cnspd.com\/spd-uc-selection-guide\/\"\r\n          target=\"_blank\"\r\n          rel=\"noopener\"\r\n        >\r\n          SPD Uc Selection Guide\r\n        <\/a>\r\n\r\n        <a\r\n          href=\"https:\/\/www.cnspd.com\/spd-up-voltage-protection-level\/\"\r\n          target=\"_blank\"\r\n          rel=\"noopener\"\r\n        >\r\n          SPD Up Voltage Protection Level\r\n        <\/a>\r\n\r\n        <a\r\n          href=\"https:\/\/www.cnspd.com\/spd-selection-guide\/\"\r\n          target=\"_blank\"\r\n          rel=\"noopener\"\r\n        >\r\n          Complete SPD Selection Guide\r\n        <\/a>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <!-- =====================================================\r\n         FAQ\r\n         ===================================================== -->\r\n    <section class=\"ly-tns-section\" id=\"faq\">\r\n      <h2><span class=\"ez-toc-section\" id=\"tn-s-system-spd-wiring-faq\"><\/span>TN-S System SPD Wiring FAQ<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <div class=\"ly-tns-faq\">\r\n        <details>\r\n          <summary>Can a 3P SPD be used in a TN-S system?<\/summary>\r\n          <div class=\"ly-tns-faq-answer\">\r\n            <p>\r\n              It may be used where the protected circuit has no neutral conductor\r\n              or where the approved project design specifically requires three-pole\r\n              protection. It should not be selected automatically for a five-conductor\r\n              TN-S panel.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>Is a 4P SPD the same as a 3P+N SPD?<\/summary>\r\n          <div class=\"ly-tns-faq-answer\">\r\n            <p>\r\n              Not necessarily. A 4P device often uses 4+0 \/ CT1, while a 3P+N\r\n              device often uses 3+1 \/ CT2. Check the internal circuit diagram.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>Can both 4+0 and 3+1 be used in TN-S?<\/summary>\r\n          <div class=\"ly-tns-faq-answer\">\r\n            <p>\r\n              Yes, manufacturer documentation shows that both arrangements may be\r\n              available for TN-S systems. The final choice must match the project,\r\n              local rules and the approved application of the exact SPD.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>Should the SPD be installed before or after the RCD?<\/summary>\r\n          <div class=\"ly-tns-faq-answer\">\r\n            <p>\r\n              There is no universal answer for every SPD. Check the product\u2019s TOV\r\n              behaviour, N-PE technology, permitted position, local installation\r\n              rules and manufacturer instructions.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>What backup breaker should be used?<\/summary>\r\n          <div class=\"ly-tns-faq-answer\">\r\n            <p>\r\n              Use the fuse or circuit breaker specified for the exact SPD after\r\n              checking the short-circuit current, Isccr, conductor size and\r\n              coordination with upstream protection.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>What should an OEM buyer request before approval?<\/summary>\r\n          <div class=\"ly-tns-faq-answer\">\r\n            <p>\r\n              Request the internal circuit diagram, wiring diagram, datasheet,\r\n              backup-protection requirement, certificate scope, product drawing\r\n              and label drawing.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <!-- =====================================================\r\n         REFERENCES\r\n         ===================================================== -->\r\n    <section class=\"ly-tns-section\">\r\n      <h2><span class=\"ez-toc-section\" id=\"technical-references\"><\/span>Technical References<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <div class=\"ly-tns-references\">\r\n        <ol>\r\n          <li id=\"ref-1\">\r\n            IEC 60364-5-53: Low-voltage electrical installations \u2014 Selection and\r\n            erection of electrical equipment.\r\n            <a\r\n              href=\"https:\/\/webstore.iec.ch\/en\/publication\/104394\"\r\n              target=\"_blank\"\r\n              rel=\"noopener nofollow\"\r\n            >Official IEC publication<\/a>.\r\n          <\/li>\r\n\r\n          <li id=\"ref-2\">\r\n            IEC 61643-11: Low-voltage surge protective devices connected to AC\r\n            low-voltage power systems \u2014 Requirements and test methods.\r\n            <a\r\n              href=\"https:\/\/webstore.iec.ch\/en\/publication\/65314\"\r\n              target=\"_blank\"\r\n              rel=\"noopener nofollow\"\r\n            >Official IEC publication<\/a>.\r\n          <\/li>\r\n\r\n          <li id=\"ref-3\">\r\n            Legrand, Modular Surge Protective Devices, technical sheet F04648EN-00.\r\n            Includes CT1 \/ X+0 and CT2 \/ X+1 protection modes and applicable\r\n            earthing systems.\r\n            <a\r\n              href=\"https:\/\/assets.legrand.com\/pim\/NP-FT-GT\/F04648EN-00.pdf\"\r\n              target=\"_blank\"\r\n              rel=\"noopener nofollow\"\r\n            >Official PDF<\/a>.\r\n          <\/li>\r\n\r\n          <li id=\"ref-4\">\r\n            Legrand, Surge Protective Devices Technical Guide. Explains CT1 and\r\n            CT2 circuits, N-PE components, TOV behaviour and RCD coordination.\r\n            <a\r\n              href=\"https:\/\/assets.legrand.com\/pim\/NP-FT-GT\/EXB20026_TG_Surge_Protective_Devices_EN.pdf\"\r\n              target=\"_blank\"\r\n              rel=\"noopener nofollow\"\r\n            >Official PDF<\/a>.\r\n          <\/li>\r\n\r\n          <li id=\"ref-5\">\r\n            ABB Furse, ESP 240CDT2 installation instructions for three-phase\r\n            TN-S, TN-C-S and TT supplies.\r\n            <a\r\n              href=\"https:\/\/library.e.abb.com\/public\/51773fd8b59d41fb8d61ab96db3d53af\/ABB-ESP-240CDT2-Surge-Protection-Series-Instructions_231121.pdf\"\r\n              target=\"_blank\"\r\n              rel=\"noopener nofollow\"\r\n            >Official PDF<\/a>.\r\n          <\/li>\r\n\r\n          <li id=\"ref-6\">\r\n            Phoenix Contact, selection guide for lightning and surge protection\r\n            in industrial buildings, including five-conductor TN-S systems.\r\n            <a\r\n              href=\"https:\/\/assets.phoenixcontact.com\/file\/58692c24-b52d-477f-991b-873f57813f1d\/media\/original?1351957_EN_UESS_Auswahlhilfe_LoRes.pdf=\"\r\n              target=\"_blank\"\r\n              rel=\"noopener nofollow\"\r\n            >Official PDF<\/a>.\r\n          <\/li>\r\n\r\n          <li id=\"ref-7\">\r\n            DEHN, Surge Protection in Low-Voltage Switchgear Assemblies.\r\n            Includes modular SPD solutions for TN-S installations.\r\n            <a\r\n              href=\"https:\/\/www.dehn-international.com\/sites\/default\/files\/media\/files\/surge-protection-low-voltage-switchgear-assemblies-wpx004-e.pdf\"\r\n              target=\"_blank\"\r\n              rel=\"noopener nofollow\"\r\n            >Official PDF<\/a>.\r\n          <\/li>\r\n        <\/ol>\r\n      <\/div>\r\n    <\/section>\r\n\r\n  <\/article>\r\n<\/div>\r\n\r\n<script>\r\ndocument.addEventListener('DOMContentLoaded', function () {\r\n  var popupButtons = document.querySelectorAll('.leeyee-site-popup-btn');\r\n\r\n  popupButtons.forEach(function (button) {\r\n    if (button.getAttribute('data-leeyee-popup-bound') === 'true') {\r\n      return;\r\n    }\r\n\r\n    button.setAttribute('data-leeyee-popup-bound', 'true');\r\n\r\n    button.addEventListener('click', function (event) {\r\n      event.preventDefault();\r\n\r\n      var realPopupTrigger = document.querySelector(\r\n        '.w-popup.ush_popup_1 .w-popup-trigger'\r\n      );\r\n\r\n      if (realPopupTrigger) {\r\n        realPopupTrigger.click();\r\n      } else {\r\n        window.open(\r\n          'https:\/\/www.cnspd.com\/contact\/',\r\n          '_blank',\r\n          'noopener'\r\n        );\r\n      }\r\n    });\r\n  });\r\n});\r\n<\/script>\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>TN-S System \u00b7 Three-Phase Distribution \u00b7 OEM Selection TN-S SPD Wiring at a Glance In a three-phase TN-S system, the surge protective device is connected in parallel with L1, L2, L3, N and PE according to the approved internal circuit of the selected SPD. Neutral and protective earth remain separate during normal operation. Quick Answer:&#8230;<\/p>","protected":false},"author":18,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1,488,422],"tags":[],"class_list":["post-30017","post","type-post","status-publish","format-standard","hentry","category-news","category-surge-protection","category-industry-news"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.9 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>TN-S System SPD Wiring: 3P, 4P or 3P+N? | LEEYEE<\/title>\n<meta name=\"description\" content=\"See how to wire an SPD in a three-phase TN-S system. 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Compare 3P, 4P, 3P+N, 4+0 and 3+1, and confirm N-PE protection before ordering.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.cnspd.com\/pt\/tn-s-system-spd-wiring\/\" \/>\n<meta property=\"og:site_name\" content=\"Surge Protector, Surge Arrestor, Isolating Switch - LEEYEE\" \/>\n<meta property=\"article:published_time\" content=\"2026-07-14T04:57:20+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2026-07-14T06:32:37+00:00\" \/>\n<meta name=\"author\" content=\"Devin Ling\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Escrito por\" \/>\n\t<meta name=\"twitter:data1\" content=\"Devin Ling\" \/>\n\t<meta name=\"twitter:label2\" content=\"Tempo estimado de leitura\" \/>\n\t<meta name=\"twitter:data2\" content=\"12 minutos\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/tn-s-system-spd-wiring\\\/#article\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/tn-s-system-spd-wiring\\\/\"},\"author\":{\"name\":\"Devin Ling\",\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/#\\\/schema\\\/person\\\/f49dbafe62c5b47100ad2d9f88af92d3\"},\"headline\":\"TN-S System SPD Wiring Guide: 3P, 4P and 3P+N Selection\",\"datePublished\":\"2026-07-14T04:57:20+00:00\",\"dateModified\":\"2026-07-14T06:32:37+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/tn-s-system-spd-wiring\\\/\"},\"wordCount\":2509,\"articleSection\":[\"News\",\"Surge Protection\",\"Technical Guides\"],\"inLanguage\":\"pt-PT\"},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/tn-s-system-spd-wiring\\\/\",\"url\":\"https:\\\/\\\/www.cnspd.com\\\/tn-s-system-spd-wiring\\\/\",\"name\":\"TN-S System SPD Wiring: 3P, 4P or 3P+N? | LEEYEE\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/#website\"},\"datePublished\":\"2026-07-14T04:57:20+00:00\",\"dateModified\":\"2026-07-14T06:32:37+00:00\",\"author\":{\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/#\\\/schema\\\/person\\\/f49dbafe62c5b47100ad2d9f88af92d3\"},\"description\":\"See how to wire an SPD in a three-phase TN-S system. 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