{"id":31089,"date":"2026-09-16T09:13:04","date_gmt":"2026-09-16T01:13:04","guid":{"rendered":"https:\/\/www.cnspd.com\/?p=31089"},"modified":"2026-09-16T09:13:33","modified_gmt":"2026-09-16T01:13:33","slug":"automatic-transfer-switch-sizing-what-size-ats-do-i-need-63a-3200a-guide","status":"publish","type":"post","link":"https:\/\/www.cnspd.com\/pt\/automatic-transfer-switch-sizing-guide\/","title":{"rendered":"Dimensionamento do comutador autom\u00e1tico de transfer\u00eancia: Que tamanho de ATS preciso? Guia de 63 A a 3 200 A"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"31089\" class=\"elementor elementor-31089\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-dd44e6f e-flex e-con-boxed e-con e-parent\" data-id=\"dd44e6f\" 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-3feeee7 elementor-widget elementor-widget-html\" data-id=\"3feeee7\" 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.ly-ats-sizing{\r\n  --ly-blue:#004898;\r\n  --ly-blue-dark:#00386f;\r\n  --ly-pale:#eef5ff;\r\n  --ly-pale-2:#f7fbff;\r\n  --ly-text:#263442;\r\n  --ly-muted:#5e6b76;\r\n  --ly-border:#d7e2ec;\r\n  --ly-warning-bg:#fff8e8;\r\n  --ly-danger-bg:#fff5f4;\r\n  --ly-green:#246c4b;\r\n  --ly-green-bg:#f1faf5;\r\n  --ly-radius:12px;\r\n  width:100%;\r\n  max-width:840px;\r\n  margin:0 auto;\r\n  color:var(--ly-text);\r\n  font-size:17px;\r\n  line-height:1.72;\r\n  box-sizing:border-box;\r\n  overflow-wrap:anywhere;\r\n}\r\n\r\n.ly-ats-sizing *,\r\n.ly-ats-sizing *::before,\r\n.ly-ats-sizing *::after{\r\n  box-sizing:border-box;\r\n}\r\n\r\n.ly-ats-sizing p{\r\n  margin:0 0 18px;\r\n}\r\n\r\n.ly-ats-sizing h2{\r\n  margin:52px 0 18px;\r\n  color:#172737;\r\n  font-size:32px;\r\n  line-height:1.22;\r\n  letter-spacing:-.02em;\r\n}\r\n\r\n.ly-ats-sizing h3{\r\n  margin:34px 0 14px;\r\n  color:#1c3043;\r\n  font-size:24px;\r\n  line-height:1.3;\r\n}\r\n\r\n.ly-ats-sizing h4{\r\n  margin:24px 0 10px;\r\n  color:#263c50;\r\n  font-size:19px;\r\n  line-height:1.4;\r\n}\r\n\r\n.ly-ats-sizing a{\r\n  color:var(--ly-blue);\r\n  text-underline-offset:2px;\r\n}\r\n\r\n.ly-ats-sizing a:hover{\r\n  text-decoration-thickness:2px;\r\n}\r\n\r\n.ly-ats-sizing strong{\r\n  color:#182a3a;\r\n}\r\n\r\n.ly-ats-sizing sup{\r\n  position:relative;\r\n  top:-.1em;\r\n  font-size:.72em;\r\n}\r\n\r\n.ly-ats-sizing sup a{\r\n  text-decoration:none;\r\n}\r\n\r\n.ly-ats-sizing ul,\r\n.ly-ats-sizing ol{\r\n  margin:12px 0 22px;\r\n  padding-left:24px;\r\n}\r\n\r\n.ly-ats-sizing li{\r\n  margin:7px 0;\r\n}\r\n\r\n.ly-ats-sizing .ly-intro{\r\n  margin:0 0 22px;\r\n  font-size:18px;\r\n  line-height:1.7;\r\n  color:#344657;\r\n}\r\n\r\n.ly-ats-sizing .ly-context-link{\r\n  margin:0 0 28px;\r\n  padding:13px 16px;\r\n  background:#fff;\r\n  border:1px solid var(--ly-border);\r\n  border-radius:8px;\r\n  color:#536270;\r\n  font-size:14px;\r\n  line-height:1.55;\r\n}\r\n\r\n.ly-ats-sizing .ly-kicker{\r\n  display:inline-block;\r\n  margin:0 0 10px;\r\n  color:var(--ly-blue);\r\n  font-size:13px;\r\n  line-height:1.3;\r\n  font-weight:700;\r\n  text-transform:uppercase;\r\n  letter-spacing:.08em;\r\n}\r\n\r\n.ly-ats-sizing .ly-quick{\r\n  margin:28px 0 32px;\r\n  padding:26px 28px;\r\n  background:var(--ly-pale-2);\r\n  border:1px solid #cadced;\r\n  border-left:4px solid var(--ly-blue);\r\n  border-radius:var(--ly-radius);\r\n}\r\n\r\n.ly-ats-sizing .ly-quick h2{\r\n  margin:0 0 14px;\r\n  font-size:27px;\r\n}\r\n\r\n.ly-ats-sizing .ly-quick p:last-child{\r\n  margin-bottom:0;\r\n}\r\n\r\n.ly-ats-sizing .ly-keyline{\r\n  margin:22px 0 0;\r\n  padding:14px 16px;\r\n  background:#fff;\r\n  border:1px solid var(--ly-border);\r\n  border-radius:8px;\r\n  font-weight:600;\r\n  color:#20364a;\r\n}\r\n\r\n.ly-ats-sizing .ly-scope{\r\n  margin:22px 0 30px;\r\n  padding:16px 18px;\r\n  background:#fafcfe;\r\n  border:1px solid var(--ly-border);\r\n  border-radius:9px;\r\n  color:#536270;\r\n  font-size:14px;\r\n  line-height:1.6;\r\n}\r\n\r\n.ly-ats-sizing .ly-buyer-meaning{\r\n  margin:20px 0 24px;\r\n  padding:15px 18px;\r\n  background:var(--ly-pale);\r\n  border-left:3px solid var(--ly-blue);\r\n  border-radius:0 8px 8px 0;\r\n}\r\n\r\n.ly-ats-sizing .ly-buyer-meaning strong{\r\n  display:block;\r\n  margin-bottom:4px;\r\n  color:var(--ly-blue-dark);\r\n}\r\n\r\n.ly-ats-sizing .ly-note{\r\n  margin:22px 0;\r\n  padding:18px 20px;\r\n  border:1px solid var(--ly-border);\r\n  border-radius:10px;\r\n  background:#fff;\r\n}\r\n\r\n.ly-ats-sizing .ly-note p:last-child{\r\n  margin-bottom:0;\r\n}\r\n\r\n.ly-ats-sizing .ly-warning{\r\n  margin:24px 0;\r\n  padding:20px 22px;\r\n  background:var(--ly-warning-bg);\r\n  border:1px solid #efd7a5;\r\n  border-left:4px solid #c47b13;\r\n  border-radius:10px;\r\n}\r\n\r\n.ly-ats-sizing .ly-warning strong{\r\n  display:block;\r\n  margin-bottom:6px;\r\n  color:#6e4307;\r\n}\r\n\r\n.ly-ats-sizing .ly-danger{\r\n  margin:24px 0;\r\n  padding:20px 22px;\r\n  background:var(--ly-danger-bg);\r\n  border:1px solid #efd1cd;\r\n  border-left:4px solid #bd4a42;\r\n  border-radius:10px;\r\n}\r\n\r\n.ly-ats-sizing .ly-danger strong{\r\n  display:block;\r\n  margin-bottom:6px;\r\n  color:#7e2929;\r\n}\r\n\r\n.ly-ats-sizing .ly-engineering{\r\n  margin:24px 0;\r\n  padding:20px 22px;\r\n  background:var(--ly-green-bg);\r\n  border:1px solid #cde5d7;\r\n  border-left:4px solid var(--ly-green);\r\n  border-radius:10px;\r\n}\r\n\r\n.ly-ats-sizing .ly-engineering strong{\r\n  display:block;\r\n  margin-bottom:6px;\r\n  color:#1f5a40;\r\n}\r\n\r\n.ly-ats-sizing .ly-three-defs{\r\n  display:grid;\r\n  grid-template-columns:repeat(3,1fr);\r\n  gap:15px;\r\n  margin:20px 0 28px;\r\n}\r\n\r\n.ly-ats-sizing .ly-def{\r\n  padding:19px;\r\n  border:1px solid var(--ly-border);\r\n  border-radius:10px;\r\n  background:#fff;\r\n}\r\n\r\n.ly-ats-sizing .ly-def h3{\r\n  margin:0 0 8px;\r\n  color:var(--ly-blue-dark);\r\n  font-size:18px;\r\n}\r\n\r\n.ly-ats-sizing .ly-def p{\r\n  margin:0;\r\n  font-size:14px;\r\n  line-height:1.58;\r\n}\r\n\r\n.ly-ats-sizing .ly-formula-grid{\r\n  display:grid;\r\n  grid-template-columns:1fr 1fr;\r\n  gap:16px;\r\n  margin:20px 0 26px;\r\n}\r\n\r\n.ly-ats-sizing .ly-formula{\r\n  padding:19px;\r\n  border:1px solid var(--ly-border);\r\n  border-radius:10px;\r\n  background:#fff;\r\n}\r\n\r\n.ly-ats-sizing .ly-formula h3{\r\n  margin:0 0 10px;\r\n  font-size:19px;\r\n}\r\n\r\n.ly-ats-sizing .ly-equation{\r\n  display:block;\r\n  margin:10px 0;\r\n  padding:12px 14px;\r\n  background:var(--ly-pale-2);\r\n  border:1px solid #d8e5f0;\r\n  border-radius:7px;\r\n  color:#173e60;\r\n  font-family:ui-monospace,SFMono-Regular,Menlo,Monaco,Consolas,\"Liberation Mono\",monospace;\r\n  font-size:15px;\r\n  line-height:1.55;\r\n  white-space:normal;\r\n}\r\n\r\n.ly-ats-sizing .ly-table-wrap{\r\n  width:100%;\r\n  margin:20px 0 28px;\r\n}\r\n\r\n.ly-ats-sizing 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(--ly-border);\r\n  border-radius:10px;\r\n  overflow:hidden;\r\n  background:#fff;\r\n}\r\n\r\n.ly-ats-sizing caption{\r\n  padding:0 0 10px;\r\n  color:var(--ly-muted);\r\n  text-align:left;\r\n  font-size:14px;\r\n  line-height:1.5;\r\n}\r\n\r\n.ly-ats-sizing th,\r\n.ly-ats-sizing td{\r\n  padding:13px 14px;\r\n  border-right:1px solid var(--ly-border);\r\n  border-bottom:1px solid var(--ly-border);\r\n  vertical-align:top;\r\n  text-align:left;\r\n  line-height:1.5;\r\n}\r\n\r\n.ly-ats-sizing th{\r\n  background:var(--ly-blue);\r\n  color:#fff;\r\n  font-size:14px;\r\n  font-weight:700;\r\n}\r\n\r\n.ly-ats-sizing td{\r\n  font-size:15px;\r\n  color:#334556;\r\n}\r\n\r\n.ly-ats-sizing th:last-child,\r\n.ly-ats-sizing td:last-child{\r\n  border-right:0;\r\n}\r\n\r\n.ly-ats-sizing tr:last-child td{\r\n  border-bottom:0;\r\n}\r\n\r\n.ly-ats-sizing .ly-rating-table th:nth-child(1),\r\n.ly-ats-sizing .ly-rating-table td:nth-child(1){\r\n  width:17%;\r\n}\r\n\r\n.ly-ats-sizing .ly-rating-table th:nth-child(2),\r\n.ly-ats-sizing .ly-rating-table td:nth-child(2){\r\n  width:31%;\r\n}\r\n\r\n.ly-ats-sizing .ly-rating-table th:nth-child(3),\r\n.ly-ats-sizing .ly-rating-table td:nth-child(3){\r\n  width:52%;\r\n}\r\n\r\n.ly-ats-sizing .ly-example-table th:nth-child(1),\r\n.ly-ats-sizing .ly-example-table td:nth-child(1){\r\n  width:27%;\r\n}\r\n\r\n.ly-ats-sizing .ly-example-table th:nth-child(2),\r\n.ly-ats-sizing .ly-example-table td:nth-child(2){\r\n  width:38%;\r\n}\r\n\r\n.ly-ats-sizing .ly-example-table th:nth-child(3),\r\n.ly-ats-sizing .ly-example-table td:nth-child(3){\r\n  width:35%;\r\n}\r\n\r\n.ly-ats-sizing .ly-procurement-conclusion{\r\n  margin:-12px 0 28px;\r\n  font-size:15px;\r\n  color:#44586a;\r\n}\r\n\r\n\/* Correct image display size:\r\n   images stay inside the article reading width instead of expanding beyond it *\/\r\n.ly-ats-sizing .ly-tech-figure{\r\n  width:100%;\r\n  max-width:760px;\r\n  margin:30px auto;\r\n}\r\n\r\n.ly-ats-sizing .ly-tech-figure img{\r\n  display:block;\r\n  width:100%;\r\n  height:auto;\r\n  max-width:760px;\r\n  margin:0 auto;\r\n  border:1px solid #dce5ed;\r\n  border-radius:12px;\r\n  background:#fff;\r\n  object-fit:contain;\r\n}\r\n\r\n.ly-ats-sizing .ly-tech-figure figcaption{\r\n  margin:10px auto 0;\r\n  padding:0 4px;\r\n  max-width:760px;\r\n  color:#687783;\r\n  font-size:14px;\r\n  line-height:1.5;\r\n}\r\n\r\n.ly-ats-sizing .ly-example{\r\n  margin:22px 0;\r\n  padding:22px;\r\n  border:1px solid var(--ly-border);\r\n  border-radius:10px;\r\n  background:#fff;\r\n}\r\n\r\n.ly-ats-sizing .ly-example h3{\r\n  margin:0 0 13px;\r\n  font-size:21px;\r\n}\r\n\r\n.ly-ats-sizing .ly-example .ly-result{\r\n  margin:14px 0;\r\n  padding:12px 14px;\r\n  background:var(--ly-pale);\r\n  border-radius:7px;\r\n  font-weight:700;\r\n  color:#153f61;\r\n}\r\n\r\n.ly-ats-sizing .ly-step-list{\r\n  margin:22px 0 30px;\r\n  padding:0;\r\n  list-style:none;\r\n  counter-reset:ly-step;\r\n}\r\n\r\n.ly-ats-sizing .ly-step-list li{\r\n  position:relative;\r\n  margin:0;\r\n  padding:17px 0 17px 54px;\r\n  border-bottom:1px solid #e3eaf0;\r\n  counter-increment:ly-step;\r\n}\r\n\r\n.ly-ats-sizing .ly-step-list li::before{\r\n  content:counter(ly-step);\r\n  position:absolute;\r\n  left:0;\r\n  top:15px;\r\n  width:34px;\r\n  height:34px;\r\n  border-radius:50%;\r\n  display:flex;\r\n  align-items:center;\r\n  justify-content:center;\r\n  background:var(--ly-pale);\r\n  border:1px solid #bfd4e8;\r\n  color:var(--ly-blue);\r\n  font-weight:800;\r\n  font-size:15px;\r\n}\r\n\r\n.ly-ats-sizing .ly-step-list li:last-child{\r\n  border-bottom:0;\r\n}\r\n\r\n.ly-ats-sizing .ly-step-list li strong{\r\n  display:block;\r\n  margin-bottom:3px;\r\n}\r\n\r\n.ly-ats-sizing .ly-two-col{\r\n  display:grid;\r\n  grid-template-columns:1fr 1fr;\r\n  gap:18px;\r\n  margin:22px 0 28px;\r\n}\r\n\r\n.ly-ats-sizing .ly-mini{\r\n  padding:20px;\r\n  border:1px solid var(--ly-border);\r\n  border-radius:10px;\r\n  background:#fff;\r\n}\r\n\r\n.ly-ats-sizing .ly-mini h3{\r\n  margin:0 0 12px;\r\n  font-size:21px;\r\n}\r\n\r\n.ly-ats-sizing .ly-mini ul{\r\n  margin-bottom:0;\r\n}\r\n\r\n.ly-ats-sizing .ly-checklist{\r\n  margin:28px 0;\r\n  padding:24px;\r\n  background:var(--ly-pale-2);\r\n  border:1px solid #cadae8;\r\n  border-radius:12px;\r\n}\r\n\r\n.ly-ats-sizing .ly-checklist h2,\r\n.ly-ats-sizing .ly-checklist h3{\r\n  margin-top:0;\r\n}\r\n\r\n.ly-ats-sizing .ly-check-grid{\r\n  display:grid;\r\n  grid-template-columns:1fr 1fr;\r\n  gap:8px 26px;\r\n  margin:14px 0 0;\r\n  padding:0;\r\n  list-style:none;\r\n}\r\n\r\n.ly-ats-sizing .ly-check-grid li{\r\n  position:relative;\r\n  margin:0;\r\n  padding:7px 0 7px 25px;\r\n}\r\n\r\n.ly-ats-sizing .ly-check-grid li::before{\r\n  content:\"\u2713\";\r\n  position:absolute;\r\n  left:0;\r\n  top:6px;\r\n  color:var(--ly-blue);\r\n  font-weight:800;\r\n}\r\n\r\n.ly-ats-sizing .ly-cta{\r\n  margin:30px 0 36px;\r\n  padding:25px 26px;\r\n  background:var(--ly-pale-2);\r\n  border:1px solid #cbdbea;\r\n  border-left:4px solid var(--ly-blue);\r\n  border-radius:12px;\r\n}\r\n\r\n.ly-ats-sizing .ly-cta h2,\r\n.ly-ats-sizing .ly-cta h3{\r\n  margin:0 0 10px;\r\n}\r\n\r\n.ly-ats-sizing .ly-cta p:last-of-type{\r\n  margin-bottom:18px;\r\n}\r\n\r\n.ly-ats-sizing .ly-small{\r\n  color:var(--ly-muted);\r\n  font-size:14px;\r\n}\r\n\r\n\/* LEEYEE inquiry popup button *\/\r\n.ly-ats-sizing .leeyee-about-btn-light{\r\n  appearance:none;\r\n  -webkit-appearance:none;\r\n  display:inline-flex;\r\n  align-items:center;\r\n  justify-content:center;\r\n  min-height:46px;\r\n  max-width:100%;\r\n  margin:0;\r\n  padding:12px 22px;\r\n  border:2px solid var(--ly-blue);\r\n  border-radius:7px;\r\n  background:#fff;\r\n  color:var(--ly-blue);\r\n  font:inherit;\r\n  font-size:15px;\r\n  line-height:1.25;\r\n  font-weight:700;\r\n  letter-spacing:0;\r\n  text-align:center;\r\n  text-decoration:none;\r\n  cursor:pointer;\r\n  transition:\r\n    background-color .2s ease,\r\n    color .2s ease,\r\n    border-color .2s ease,\r\n    box-shadow .2s ease,\r\n    transform .2s ease;\r\n}\r\n\r\n.ly-ats-sizing .leeyee-about-btn-light .w-btn-label{\r\n  display:block;\r\n  color:inherit;\r\n  line-height:1.25;\r\n}\r\n\r\n.ly-ats-sizing .leeyee-about-btn-light:hover{\r\n  background:var(--ly-blue);\r\n  border-color:var(--ly-blue);\r\n  color:#fff;\r\n  transform:translateY(-1px);\r\n  box-shadow:0 6px 16px rgba(0,72,152,.16);\r\n}\r\n\r\n.ly-ats-sizing .leeyee-about-btn-light:active{\r\n  transform:translateY(0);\r\n  box-shadow:none;\r\n}\r\n\r\n.ly-ats-sizing .leeyee-about-btn-light:focus{\r\n  outline:none;\r\n}\r\n\r\n.ly-ats-sizing .leeyee-about-btn-light:focus-visible{\r\n  outline:3px solid rgba(0,72,152,.22);\r\n  outline-offset:3px;\r\n  background:var(--ly-blue);\r\n  border-color:var(--ly-blue);\r\n  color:#fff;\r\n}\r\n\r\n.ly-ats-sizing .ly-faq{\r\n  border-top:1px solid var(--ly-border);\r\n}\r\n\r\n.ly-ats-sizing .ly-faq-item{\r\n  padding:23px 0;\r\n  border-bottom:1px solid var(--ly-border);\r\n}\r\n\r\n.ly-ats-sizing .ly-faq-item h3{\r\n  margin:0 0 9px;\r\n  font-size:21px;\r\n}\r\n\r\n.ly-ats-sizing .ly-faq-item p:last-child{\r\n  margin-bottom:0;\r\n}\r\n\r\n.ly-ats-sizing .ly-related{\r\n  margin:40px 0 8px;\r\n  padding:22px 24px;\r\n  background:#fff;\r\n  border:1px solid var(--ly-border);\r\n  border-radius:10px;\r\n}\r\n\r\n.ly-ats-sizing .ly-related h2{\r\n  margin:0 0 12px;\r\n  font-size:25px;\r\n}\r\n\r\n.ly-ats-sizing .ly-related ul{\r\n  margin:0;\r\n  padding-left:20px;\r\n}\r\n\r\n.ly-ats-sizing .ly-related li{\r\n  margin:8px 0;\r\n}\r\n\r\n.ly-ats-sizing .ly-references{\r\n  margin:48px 0 0;\r\n  padding-top:4px;\r\n  border-top:2px solid #dbe5ed;\r\n}\r\n\r\n.ly-ats-sizing .ly-references ol{\r\n  padding-left:22px;\r\n}\r\n\r\n.ly-ats-sizing .ly-references li{\r\n  margin:13px 0;\r\n  color:#4e5f6d;\r\n  font-size:14px;\r\n  line-height:1.58;\r\n}\r\n\r\n.ly-ats-sizing .ly-references a{\r\n  word-break:break-word;\r\n}\r\n\r\n.ly-ats-sizing .ly-brand-note{\r\n  margin:30px 0 0;\r\n  padding-top:18px;\r\n  border-top:1px solid #e3e9ee;\r\n  color:#6a7781;\r\n  font-size:13px;\r\n}\r\n\r\n@media (max-width:900px){\r\n  .ly-ats-sizing{\r\n    max-width:100%;\r\n    padding:0 22px;\r\n  }\r\n\r\n  .ly-ats-sizing .ly-tech-figure,\r\n  .ly-ats-sizing .ly-tech-figure img{\r\n    max-width:720px;\r\n  }\r\n}\r\n\r\n@media (max-width:820px){\r\n  .ly-ats-sizing .ly-tech-figure,\r\n  .ly-ats-sizing .ly-tech-figure img{\r\n    max-width:100%;\r\n  }\r\n}\r\n\r\n@media (max-width:768px){\r\n  .ly-ats-sizing{\r\n    font-size:16px;\r\n    line-height:1.7;\r\n  }\r\n\r\n  .ly-ats-sizing h2{\r\n    margin-top:44px;\r\n    font-size:28px;\r\n  }\r\n\r\n  .ly-ats-sizing h3{\r\n    font-size:22px;\r\n  }\r\n\r\n  .ly-ats-sizing .ly-formula-grid,\r\n  .ly-ats-sizing .ly-two-col,\r\n  .ly-ats-sizing .ly-check-grid,\r\n  .ly-ats-sizing .ly-three-defs{\r\n    grid-template-columns:1fr;\r\n  }\r\n\r\n  .ly-ats-sizing .ly-quick,\r\n  .ly-ats-sizing .ly-checklist,\r\n  .ly-ats-sizing .ly-cta{\r\n    padding:21px;\r\n  }\r\n\r\n  .ly-ats-sizing th,\r\n  .ly-ats-sizing td{\r\n    padding:11px 10px;\r\n    font-size:13px;\r\n  }\r\n}\r\n\r\n@media (max-width:600px){\r\n  .ly-ats-sizing .ly-table-wrap{\r\n    overflow-x:auto;\r\n    -webkit-overflow-scrolling:touch;\r\n    padding-bottom:3px;\r\n  }\r\n\r\n  .ly-ats-sizing table{\r\n    min-width:600px;\r\n  }\r\n\r\n  .ly-ats-sizing .leeyee-about-btn-light{\r\n    width:100%;\r\n    min-height:48px;\r\n    padding:13px 18px;\r\n  }\r\n}\r\n\r\n@media (max-width:540px){\r\n  .ly-ats-sizing{\r\n    padding:0 16px;\r\n  }\r\n\r\n  .ly-ats-sizing h2{\r\n    font-size:25px;\r\n    line-height:1.28;\r\n  }\r\n\r\n  .ly-ats-sizing h3{\r\n    font-size:20px;\r\n  }\r\n\r\n  .ly-ats-sizing .ly-intro{\r\n    font-size:17px;\r\n  }\r\n\r\n  .ly-ats-sizing .ly-quick h2{\r\n    font-size:23px;\r\n  }\r\n\r\n  .ly-ats-sizing .ly-tech-figure{\r\n    margin:24px auto;\r\n  }\r\n\r\n  .ly-ats-sizing .ly-tech-figure img{\r\n    width:100%;\r\n    max-width:100%;\r\n    border-radius:9px;\r\n  }\r\n}\r\n\r\n@media (max-width:390px){\r\n  .ly-ats-sizing{\r\n    padding:0 13px;\r\n  }\r\n\r\n  .ly-ats-sizing .ly-quick,\r\n  .ly-ats-sizing .ly-checklist,\r\n  .ly-ats-sizing .ly-cta,\r\n  .ly-ats-sizing .ly-example{\r\n    padding:18px;\r\n  }\r\n\r\n  .ly-ats-sizing .ly-equation{\r\n    padding:10px;\r\n    font-size:13px;\r\n  }\r\n\r\n  .ly-ats-sizing .leeyee-about-btn-light{\r\n    font-size:14px;\r\n  }\r\n}\r\n<\/style>\r\n\r\n<article class=\"ly-ats-sizing\">\r\n\r\n  <p class=\"ly-intro\">\r\n    Automatic transfer switch sizing starts with the current that will actually pass through the ATS, but it does not end there. A reliable selection must also consider maximum demand, continuous loading, motors and other inductive loads, generator capability, rated operational current, utilization category, protective-device coordination, available fault current, temperature, terminals and switchboard integration.\r\n  <\/p>\r\n\r\n  <p class=\"ly-context-link\">\r\n    Need the basic operating principle, pole selection or difference between an ATS and a UPS first?\r\n    Read <a href=\"https:\/\/www.cnspd.com\/what-is-an-automatic-transfer-switch-how-ats-works-how-to-choose\/\">What Is an Automatic Transfer Switch? How ATS Works &amp; How to Choose<\/a>.\r\n    This page stays focused specifically on <strong>ATS current sizing<\/strong>.\r\n  <\/p>\r\n\r\n  <section class=\"ly-quick\" aria-labelledby=\"ly-quick-answer\">\r\n    <span class=\"ly-kicker\">Quick Answer<\/span>\r\n    <div id=\"ez-toc-container\" class=\"ez-toc-v2_0_87 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\/automatic-transfer-switch-sizing-guide\/#what-size-ats-do-i-need\" >What Size ATS Do I Need?<\/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\/automatic-transfer-switch-sizing-guide\/#1-connected-load-maximum-demand-and-source-capacity-are-not-the-same\" >1. Connected Load, Maximum Demand and Source Capacity Are Not the Same<\/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\/automatic-transfer-switch-sizing-guide\/#2-convert-kw-or-kva-to-current-correctly\" >2. Convert kW or kVA to Current Correctly<\/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\/automatic-transfer-switch-sizing-guide\/#3-three-worked-ats-sizing-examples\" >3. Three Worked ATS Sizing Examples<\/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\/automatic-transfer-switch-sizing-guide\/#4-calculated-current-is-not-the-final-ats-rating\" >4. Calculated Current Is Not the Final ATS Rating<\/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\/automatic-transfer-switch-sizing-guide\/#5-rated-operational-current-ie-the-missing-link-between-calculation-and-model\" >5. Rated Operational Current Ie: The Missing Link Between Calculation and Model<\/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\/automatic-transfer-switch-sizing-guide\/#6-do-you-need-a-20-or-25-ats-sizing-margin\" >6. Do You Need a 20% or 25% ATS Sizing Margin?<\/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\/automatic-transfer-switch-sizing-guide\/#7-can-an-ats-run-continuously-at-its-full-ampere-rating\" >7. Can an ATS Run Continuously at Its Full Ampere Rating?<\/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\/automatic-transfer-switch-sizing-guide\/#8-motors-pumps-compressors-and-hvac-loads\" >8. Motors, Pumps, Compressors and HVAC Loads<\/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\/automatic-transfer-switch-sizing-guide\/#9-published-engineering-example-545a-load-to-a-600a-ats\" >9. Published Engineering Example: 545A Load to a 600A ATS<\/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\/automatic-transfer-switch-sizing-guide\/#10-should-ats-rating-match-generator-rating\" >10. Should ATS Rating Match Generator Rating?<\/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\/automatic-transfer-switch-sizing-guide\/#11-should-the-mccb-acb-and-ats-have-the-same-ampere-rating\" >11. Should the MCCB, ACB and ATS Have the Same Ampere Rating?<\/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\/automatic-transfer-switch-sizing-guide\/#12-available-fault-current-can-change-the-ats-selection\" >12. Available Fault Current Can Change the ATS Selection<\/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\/automatic-transfer-switch-sizing-guide\/#13-does-ambient-temperature-or-enclosure-design-change-ats-sizing\" >13. Does Ambient Temperature or Enclosure Design Change ATS Sizing?<\/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\/automatic-transfer-switch-sizing-guide\/#14-63a-to-3200a-ats-sizing-reference\" >14. 63A to 3200A ATS Sizing Reference<\/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\/automatic-transfer-switch-sizing-guide\/#15-why-two-400a-ats-units-may-not-be-equivalent\" >15. Why Two 400A ATS Units May Not Be Equivalent<\/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\/automatic-transfer-switch-sizing-guide\/#16-what-happens-if-the-ats-is-too-small\" >16. What Happens If the ATS Is Too Small?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-18\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/pt\/automatic-transfer-switch-sizing-guide\/#17-is-an-oversized-ats-always-better\" >17. Is an Oversized ATS Always Better?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-19\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/pt\/automatic-transfer-switch-sizing-guide\/#18-how-ats-current-rating-affects-price-and-lead-time\" >18. How ATS Current Rating Affects Price and Lead Time<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-20\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/pt\/automatic-transfer-switch-sizing-guide\/#19-final-ats-sizing-decision-table\" >19. Final ATS Sizing Decision Table<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-21\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/pt\/automatic-transfer-switch-sizing-guide\/#20-information-to-send-before-requesting-an-ats-recommendation\" >20. Information to Send Before Requesting an ATS Recommendation<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-22\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/pt\/automatic-transfer-switch-sizing-guide\/#21-frequently-asked-ats-sizing-questions\" >21. Frequently Asked ATS Sizing Questions<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-23\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/pt\/automatic-transfer-switch-sizing-guide\/#related-ats-reading\" >Related ATS Reading<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-24\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/pt\/automatic-transfer-switch-sizing-guide\/#references\" >References<\/a><\/li><\/ul><\/nav><\/div>\n<h2 id=\"ly-quick-answer\"><span class=\"ez-toc-section\" id=\"what-size-ats-do-i-need\"><\/span>What Size ATS Do I Need?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n    <p>\r\n      Choose an automatic transfer switch whose applicable <strong>rated operational current is not lower than the verified design current that the ATS must carry<\/strong>. If the load is given in kW or kVA, first convert it to line current using the correct voltage, phase and power factor.\r\n    <\/p>\r\n\r\n    <p>\r\n      Then verify maximum demand, continuous-load conditions, motor or HVAC duty, generator capability, breaker coordination, available fault current, utilization category, ambient conditions and the terminals of the proposed model. Finally, select an available ATS rating that satisfies all of those conditions.\r\n    <\/p>\r\n\r\n    <p>\r\n      A calculated load of about <strong>144A<\/strong> may make a <strong>160A ATS<\/strong> a reasonable preliminary candidate. A calculated load of about <strong>321A<\/strong> may point toward <strong>400A<\/strong>. Neither calculation alone proves that a particular model is suitable.\r\n    <\/p>\r\n\r\n    <div class=\"ly-keyline\">\r\n      ATS sizing = actual transferred demand \u2192 calculated current \u2192 duty verification \u2192 protection and fault-current check \u2192 suitable ATS rating \u2192 model and cabinet confirmation.\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <div class=\"ly-scope\">\r\n    <strong>Scope:<\/strong> The 63A\u20133200A ratings in this guide are industry sizing reference points for engineering and procurement discussions. They do not imply that LEEYEE supplies every rating shown. LEEYEE's currently published ATS-63 product range covers 6A\u201363A; higher-current projects must be verified against the documentation of the specific proposed equipment.\r\n  <\/div>\r\n\r\n  <figure class=\"ly-tech-figure\">\r\n    <img fetchpriority=\"high\"\r\n      src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/09\/ats-sizing-decision-flow.webp\"\r\n      alt=\"Automatic transfer switch sizing decision flow from load calculation to final ATS rating\"\r\n      width=\"1448\"\r\n      height=\"1086\"\r\n      decoding=\"async\"\r\n      fetchpriority=\"high\">\r\n    <figcaption>\r\n      ATS sizing is a decision process, not one formula. The calculated current is the starting point; the final switch must also suit the load duty, protection system, fault level and installation.\r\n    <\/figcaption>\r\n  <\/figure>\r\n\r\n  <div class=\"ly-buyer-meaning\">\r\n    <strong>Buyer meaning<\/strong>\r\n    \u201c400A ATS\u201d is not enough information for a technically complete quotation. The supplier also needs to know what the ATS carries, how the load behaves and how the switch will be protected.\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"1-connected-load-maximum-demand-and-source-capacity-are-not-the-same\"><\/span>1. Connected Load, Maximum Demand and Source Capacity Are Not the Same<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    These three values are often mixed together during ATS selection. They answer different engineering questions.\r\n  <\/p>\r\n\r\n  <div class=\"ly-three-defs\">\r\n    <div class=\"ly-def\">\r\n      <h3>Connected Load<\/h3>\r\n      <p>\r\n        The total rating of equipment electrically connected downstream. It does not automatically mean that every load operates at full power at the same time.\r\n      <\/p>\r\n    <\/div>\r\n\r\n    <div class=\"ly-def\">\r\n      <h3>Maximum Demand<\/h3>\r\n      <p>\r\n        The highest design load expected to operate simultaneously, based on the approved load schedule, demand factors or project study.\r\n      <\/p>\r\n    <\/div>\r\n\r\n    <div class=\"ly-def\">\r\n      <h3>Source Capacity<\/h3>\r\n      <p>\r\n        The capability of the utility, generator or other source. It determines what the source can supply, not automatically what one ATS must carry.\r\n      <\/p>\r\n    <\/div>\r\n  <\/div>\r\n\r\n  <p>\r\n    For ATS current sizing, begin with the approved load or demand that can actually pass through the specific transfer switch. A generator can serve several ATS units, so the generator's complete kVA rating does not automatically become the ampere rating of every downstream ATS.\r\n  <\/p>\r\n\r\n  <div class=\"ly-engineering\">\r\n    <strong>Engineering rule<\/strong>\r\n    Use the downstream load schedule, verified maximum demand or another approved design basis for the ATS location. Do not size an individual ATS from unrelated site capacity.\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"2-convert-kw-or-kva-to-current-correctly\"><\/span>2. Convert kW or kVA to Current Correctly<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    If approved full-load current is already available from the equipment nameplate, load schedule or project design, use that current instead of converting power back to amperes with unnecessary assumptions.\r\n  <\/p>\r\n\r\n  <p>\r\n    If only power is available, distinguish <strong>kVA<\/strong> from <strong>kW<\/strong>. kVA represents apparent power. kW represents real power and therefore requires power factor when converted to AC line current.\r\n  <\/p>\r\n\r\n  <div class=\"ly-formula-grid\">\r\n    <div class=\"ly-formula\">\r\n      <h3>Single-Phase Load<\/h3>\r\n      <span class=\"ly-equation\">From kVA: I = kVA \u00d7 1000 \u00f7 V<\/span>\r\n      <span class=\"ly-equation\">From electrical-input kW: I = kW \u00d7 1000 \u00f7 (V \u00d7 PF)<\/span>\r\n      <p class=\"ly-small\">\r\n        If a motor value is mechanical shaft-output kW rather than electrical input kW, motor efficiency must also be considered.\r\n      <\/p>\r\n    <\/div>\r\n\r\n    <div class=\"ly-formula\">\r\n      <h3>Three-Phase Load<\/h3>\r\n      <span class=\"ly-equation\">From kVA: I = kVA \u00d7 1000 \u00f7 (\u221a3 \u00d7 V)<\/span>\r\n      <span class=\"ly-equation\">From electrical-input kW: I = kW \u00d7 1000 \u00f7 (\u221a3 \u00d7 V \u00d7 PF)<\/span>\r\n      <p class=\"ly-small\">\r\n        Use the line-to-line voltage for a balanced three-phase calculation.\r\n      <\/p>\r\n    <\/div>\r\n  <\/div>\r\n\r\n  <div class=\"ly-note\">\r\n    <p>\r\n      <strong>PF means power factor.<\/strong> A 200 kW three-phase load at PF 0.90 draws more current than the same 200 kW at PF 1.00. This is why a generic \u201cpower \u00f7 voltage\u201d calculation is not a complete three-phase ATS sizing method.\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"3-three-worked-ats-sizing-examples\"><\/span>3. Three Worked ATS Sizing Examples<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <div class=\"ly-example\">\r\n    <h3>Example A \u2014 10 kW, 230 V, Single Phase<\/h3>\r\n    <p>Assume the 10 kW value is electrical input power and PF = 0.95.<\/p>\r\n    <span class=\"ly-equation\">I = 10,000 \u00f7 (230 \u00d7 0.95) \u2248 45.8 A<\/span>\r\n    <div class=\"ly-result\">Calculated operating current: approximately 46A<\/div>\r\n    <p>\r\n      A 63A ATS may be a practical preliminary rating if the applicable continuous-current and duty requirements are also satisfied.\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <div class=\"ly-example\">\r\n    <h3>Example B \u2014 100 kVA, 400 V, Three Phase<\/h3>\r\n    <span class=\"ly-equation\">I = 100,000 \u00f7 (\u221a3 \u00d7 400) \u2248 144 A<\/span>\r\n    <div class=\"ly-result\">Calculated apparent-load current: approximately 144A<\/div>\r\n    <p>\r\n      If the full 100 kVA is genuinely expected to pass through this ATS, 160A may be the next practical preliminary rating. Do not turn this into a universal rule that \u201c100 kVA generator = 160A ATS.\u201d\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <div class=\"ly-example\">\r\n    <h3>Example C \u2014 200 kW, 400 V, Three Phase, PF 0.90<\/h3>\r\n    <span class=\"ly-equation\">I = 200,000 \u00f7 (\u221a3 \u00d7 400 \u00d7 0.90) \u2248 321 A<\/span>\r\n    <div class=\"ly-result\">Calculated operating current: approximately 321A<\/div>\r\n    <p>\r\n      A 400A ATS may appear to be the next suitable frame or rating. Before approving it, verify the proposed device's actual rated operational current, utilization category, continuous-loading conditions, upstream protection and fault-current capability.\r\n    <\/p>\r\n  <\/div>\r\n\r\n  <figure class=\"ly-tech-figure\">\r\n    <img loading=\"lazy\"\r\n      src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/09\/calculated-current-to-final-ats-size.webp\"\r\n      alt=\"Example showing why calculated load current is not the final automatic transfer switch size\"\r\n      width=\"1448\"\r\n      height=\"1086\"\r\n      loading=\"lazy\"\r\n      decoding=\"async\">\r\n    <figcaption>\r\n      A 321A calculation can make 400A a reasonable candidate, but the final model still requires project verification. Calculated load current and approved ATS selection are two different stages.\r\n    <\/figcaption>\r\n  <\/figure>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"4-calculated-current-is-not-the-final-ats-rating\"><\/span>4. Calculated Current Is Not the Final ATS Rating<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    The next catalogue number is only a candidate. A model should not be approved until the electrical and mechanical conditions associated with its published rating have been checked.\r\n  <\/p>\r\n\r\n  <ol class=\"ly-step-list\">\r\n    <li>\r\n      <strong>Identify the transferred loads.<\/strong>\r\n      Confirm which feeders and equipment are downstream of this specific ATS.\r\n    <\/li>\r\n    <li>\r\n      <strong>Confirm voltage, phase and frequency.<\/strong>\r\n      Use actual project data rather than an assumed system voltage.\r\n    <\/li>\r\n    <li>\r\n      <strong>Determine design current.<\/strong>\r\n      Use approved current data or calculate from kVA or kW with the correct assumptions.\r\n    <\/li>\r\n    <li>\r\n      <strong>Apply the correct demand and continuous-load rules.<\/strong>\r\n      Follow the applicable code, design specification and manufacturer rating.\r\n    <\/li>\r\n    <li>\r\n      <strong>Check motors, pumps, compressors and HVAC loads.<\/strong>\r\n      Verify the switching duty rather than converting starting current directly into ATS ampere rating.\r\n    <\/li>\r\n    <li>\r\n      <strong>Verify rated operational current and utilization category.<\/strong>\r\n      Confirm that the proposed ATS rating applies at the project voltage and for the actual load type.\r\n    <\/li>\r\n    <li>\r\n      <strong>Check both sources and upstream protective devices.<\/strong>\r\n      Review generator capability, normal supply and MCCB, ACB or fuse coordination.\r\n    <\/li>\r\n    <li>\r\n      <strong>Verify available fault current.<\/strong>\r\n      Confirm that the ATS short-circuit or withstand-and-closing capability is adequate at its installation point.\r\n    <\/li>\r\n    <li>\r\n      <strong>Confirm temperature, terminals and physical integration.<\/strong>\r\n      Check conductor range, enclosure, ventilation, busbars or parallel cables, pole configuration and maintenance space.\r\n    <\/li>\r\n  <\/ol>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"5-rated-operational-current-ie-the-missing-link-between-calculation-and-model\"><\/span>5. Rated Operational Current Ie: The Missing Link Between Calculation and Model<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    A catalogue family or frame description such as \u201c400A ATS\u201d should not be treated as proof that every version of that product can carry 400A under every operating condition.\r\n  <\/p>\r\n\r\n  <p>\r\n    For IEC-based equipment, verify the manufacturer's declared <strong>rated operational current, Ie<\/strong>, together with rated operational voltage and the applicable utilization category. Load type matters because transfer switches have to make and break different kinds of current during transfer.\r\n  <\/p>\r\n\r\n  <p>\r\n    Cummins' transfer-switch application manual explains that IEC utilization categories distinguish non-inductive or slightly inductive loads from motor and mixed loads. It identifies AC-31 categories for non-inductive or slightly inductive duty and AC-33 categories for motor or mixed-load duty.<sup><a href=\"#ats-ref-3\">[3]<\/a><\/sup>\r\n  <\/p>\r\n\r\n  <div class=\"ly-buyer-meaning\">\r\n    <strong>Buyer meaning<\/strong>\r\n    If your calculation gives 365A, do not approve a \u201c400A\u201d unit from the product title alone. Check the datasheet and confirm that the relevant Ie and utilization category satisfy the real project conditions.\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"6-do-you-need-a-20-or-25-ats-sizing-margin\"><\/span>6. Do You Need a 20% or 25% ATS Sizing Margin?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    There is no responsible global rule that says every ATS should be selected at \u201ccalculated current \u00d7 1.20\u201d or \u201ccalculated current \u00d7 1.25.\u201d\r\n  <\/p>\r\n\r\n  <p>\r\n    A larger design value can result from different requirements: a continuous-load rule in the applicable electrical code, manufacturer limitations, future expansion, temperature, conductors, fault-current performance or the project specification. Those reasons should be identified separately.\r\n  <\/p>\r\n\r\n  <p>\r\n    Cummins states that most transfer switches are capable of carrying 100% of rated current at 40\u00b0C ambient, while transfer switches incorporating integral overcurrent protection may be limited to continuous loading not exceeding 80% of the switch rating. The manufacturer's own specification determines which condition applies.<sup><a href=\"#ats-ref-3\">[3]<\/a><\/sup>\r\n  <\/p>\r\n\r\n  <div class=\"ly-warning\">\r\n    <strong>Do not use an unexplained safety factor.<\/strong>\r\n    If a 400A design load leads to a recommendation for 500A, 630A or another rating, identify the technical reason: continuous-load treatment, future expansion, temperature, conductor acceptance, fault-current capability or another documented project requirement.\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"7-can-an-ats-run-continuously-at-its-full-ampere-rating\"><\/span>7. Can an ATS Run Continuously at Its Full Ampere Rating?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    Sometimes yes, but this must be confirmed from the specific product data rather than assumed from the model name.\r\n  <\/p>\r\n\r\n  <p>\r\n    Continuous-current capability can depend on the switch design, integral protective device, ambient condition and installation instructions. Cummins specifically instructs designers to use the manufacturer's rating information when determining whether an ATS is 80% or 100% rated for continuous load.<sup><a href=\"#ats-ref-3\">[3]<\/a><\/sup>\r\n  <\/p>\r\n\r\n  <div class=\"ly-buyer-meaning\">\r\n    <strong>Buyer meaning<\/strong>\r\n    Do not approve a 400A ATS for a continuous 400A project load only because \u201c400A\u201d appears on the quotation. Confirm the continuous-current condition in the current technical documentation.\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"8-motors-pumps-compressors-and-hvac-loads\"><\/span>8. Motors, Pumps, Compressors and HVAC Loads<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    Motor starting current can be many times higher than normal running current. This affects generator behaviour, protection and transfer-switch duty, but it should not simply replace normal operating current as the ATS continuous-current rating.\r\n  <\/p>\r\n\r\n  <p>\r\n    IEC utilization categories and UL 1008 overload tests address switching duties that include motor and mixed loads. Cummins notes that transfer equipment must tolerate the electrical stresses associated with transferring such loads and explains that motor or mixed-load applications use different utilization duty from non-inductive loads.<sup><a href=\"#ats-ref-3\">[3]<\/a><\/sup>\r\n  <\/p>\r\n\r\n  <p>\r\n    Generator transient performance is a separate system check. A switch can have an appropriate current rating while the generator still experiences unacceptable voltage or frequency dip when a large motor starts.\r\n  <\/p>\r\n\r\n  <div class=\"ly-danger\">\r\n    <strong>Common mistake<\/strong>\r\n    \u201cThe motor draws 600A during starting, so I need a 600A ATS\u201d is not a complete engineering method. Verify running current, starting method, ATS utilization duty, generator response and protection coordination separately.\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"9-published-engineering-example-545a-load-to-a-600a-ats\"><\/span>9. Published Engineering Example: 545A Load to a 600A ATS<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    A published U.S. Tri-Service Electrical Working Group calculation provides a useful example of the sizing logic. For a 208Y\/120V three-phase circuit containing resistive heating, incandescent lighting and four motors, the document calculates a total continuous load of <strong>545A<\/strong> and selects a <strong>600A ATS<\/strong>, the next standard size in that example.<sup><a href=\"#ats-ref-5\">[5]<\/a><\/sup>\r\n  <\/p>\r\n\r\n  <p>\r\n    Importantly, the same example separately instructs the designer to verify with the manufacturer that the ATS is acceptable for the expected motor inrush current.<sup><a href=\"#ats-ref-5\">[5]<\/a><\/sup>\r\n  <\/p>\r\n\r\n  <div class=\"ly-engineering\">\r\n    <strong>What this example teaches<\/strong>\r\n    Calculate the continuous load, select a suitable standard rating, then verify special switching duty. It is an example of the decision process\u2014not a universal rule that every 545A project must use exactly the same equipment.\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"10-should-ats-rating-match-generator-rating\"><\/span>10. Should ATS Rating Match Generator Rating?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    <strong>Not necessarily.<\/strong> Generator rating and ATS current rating describe related but different parts of the power system.\r\n  <\/p>\r\n\r\n  <p>\r\n    The generator indicates how much electrical power the standby source can provide. The ATS must safely carry and transfer the loads connected through that specific switch.\r\n  <\/p>\r\n\r\n  <p>\r\n    If one 500 kVA generator supplies several emergency feeders, each feeder can have a different transferred load and therefore a different ATS requirement. If one ATS carries the complete emergency bus, the relationship between generator current and ATS current can be much closer.\r\n  <\/p>\r\n\r\n  <div class=\"ly-engineering\">\r\n    <strong>Engineering meaning<\/strong>\r\n    Do not ask only \u201cWhat ATS belongs to a 500 kVA generator?\u201d Ask \u201cWhat current can pass through this ATS, what loads are transferred, and what duty must this particular switch withstand?\u201d\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"11-should-the-mccb-acb-and-ats-have-the-same-ampere-rating\"><\/span>11. Should the MCCB, ACB and ATS Have the Same Ampere Rating?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    Not as a universal rule. They must form a compatible protection and distribution system, but their nameplate ampere values do not always have to be identical.\r\n  <\/p>\r\n\r\n  <p>\r\n    Review the load current, conductor ampacity, ATS rated operational current, protective-device type and settings, and the available short-circuit current at the ATS location.\r\n  <\/p>\r\n\r\n  <p>\r\n    Cummins states that the transfer switch must supply the required load current and also withstand the available fault current at its point of interconnection.<sup><a href=\"#ats-ref-3\">[3]<\/a><\/sup> Eaton likewise explains that Withstand and Closing Rating, or WCR, must be considered when applying UL 1008 transfer equipment in a distribution system.<sup><a href=\"#ats-ref-4\">[4]<\/a><\/sup>\r\n  <\/p>\r\n\r\n  <div class=\"ly-warning\">\r\n    <strong>400A does not mean 40kA, 50kA or 100kA fault capability.<\/strong>\r\n    Operational-current rating and short-circuit capability are different parameters. Both must be verified.\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"12-available-fault-current-can-change-the-ats-selection\"><\/span>12. Available Fault Current Can Change the ATS Selection<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    An ATS can have enough continuous ampere capacity and still be unsuitable for the installation because the available fault current is too high.\r\n  <\/p>\r\n\r\n  <p>\r\n    Cummins notes that available fault current should be determined from each source at the transfer-switch location and that the ATS must be applied within its tested short-circuit or withstand-and-closing rating.<sup><a href=\"#ats-ref-3\">[3]<\/a><\/sup>\r\n  <\/p>\r\n\r\n  <p>\r\n    Its application manual also explains that a larger switch can sometimes be required when the fault-current capability of a smaller switch is insufficient, even though the normal load current has not increased.<sup><a href=\"#ats-ref-3\">[3]<\/a><\/sup>\r\n  <\/p>\r\n\r\n  <p>\r\n    For UL projects, review the applicable WCR and any conditions associated with the upstream breaker or fuse. For IEC projects, review the specific manufacturer's declared short-circuit characteristics and the project protection arrangement.\r\n  <\/p>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"13-does-ambient-temperature-or-enclosure-design-change-ats-sizing\"><\/span>13. Does Ambient Temperature or Enclosure Design Change ATS Sizing?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    It can. Product current ratings are published for defined conditions, so ambient temperature and installation arrangement should be checked before a high-current model is approved.\r\n  <\/p>\r\n\r\n  <p>\r\n    Do not invent a universal temperature-derating percentage. Use the manufacturer's current datasheet or derating information for the selected product.\r\n  <\/p>\r\n\r\n  <h3>Check the Installation Environment<\/h3>\r\n\r\n  <ul>\r\n    <li>Expected ambient temperature inside the switchboard;<\/li>\r\n    <li>Indoor, outdoor or sealed enclosure;<\/li>\r\n    <li>Ventilation and heat dissipation;<\/li>\r\n    <li>Altitude if the manufacturer specifies an altitude limit or derating;<\/li>\r\n    <li>Dust, humidity or corrosive environmental requirements;<\/li>\r\n    <li>Required enclosure or IP \/ NEMA construction.<\/li>\r\n  <\/ul>\r\n\r\n  <h3>Check the Terminals Before Increasing Cable Size<\/h3>\r\n\r\n  <p>\r\n    Oversized feeders can create a mechanical problem even when the current calculation is acceptable. Cummins notes that field-wiring lugs have a limited conductor-size range and that a larger switch may sometimes be required simply because the selected switch cannot accept an oversized conductor.<sup><a href=\"#ats-ref-3\">[3]<\/a><\/sup>\r\n  <\/p>\r\n\r\n  <p>\r\n    At larger currents, also verify the number of parallel cables, lug quantity, cable bending space, busbar interface and the ability to terminate conductors without creating an impractical cabinet layout.\r\n  <\/p>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"14-63a-to-3200a-ats-sizing-reference\"><\/span>14. 63A to 3200A ATS Sizing Reference<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    The following current ratings are useful procurement reference points. They are not fixed power conversions and they are not universal manufacturer frame sizes.\r\n  <\/p>\r\n\r\n  <figure class=\"ly-tech-figure\">\r\n    <img loading=\"lazy\"\r\n      src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/09\/ats-63a-to-3200a-rating-comparison.webp\"\r\n      alt=\"Comparison of 63A to 3200A automatic transfer switch ratings and typical project scale\"\r\n      width=\"1448\"\r\n      height=\"1086\"\r\n      loading=\"lazy\"\r\n      decoding=\"async\">\r\n    <figcaption>\r\n      As ATS current increases, project decisions increasingly involve conductors or busbars, terminals, fault-current performance, protective coordination, cabinet space and installation logistics. The graphic is an engineering comparison, not a scale drawing.\r\n    <\/figcaption>\r\n  <\/figure>\r\n\r\n  <h3>63A, 100A, 160A and 250A ATS Projects<\/h3>\r\n\r\n  <div class=\"ly-table-wrap\">\r\n    <table class=\"ly-rating-table\">\r\n      <caption>Illustrative engineering context only. Always confirm the proposed product against project documentation.<\/caption>\r\n      <thead>\r\n        <tr>\r\n          <th>ATS Rating<\/th>\r\n          <th>Typical Project Context<\/th>\r\n          <th>What to Verify<\/th>\r\n        <\/tr>\r\n      <\/thead>\r\n      <tbody>\r\n        <tr>\r\n          <td><strong>63A<\/strong><\/td>\r\n          <td>Small distribution, control or selected-load system<\/td>\r\n          <td>Actual demand, voltage, poles, utilization duty and cable terminals<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td><strong>100A<\/strong><\/td>\r\n          <td>Small commercial or generator-backed feeder<\/td>\r\n          <td>Continuous demand, source current, breaker arrangement and enclosure<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td><strong>160A<\/strong><\/td>\r\n          <td>Commercial feeder or medium generator panel<\/td>\r\n          <td>Motor loads, Ie, utilization category, MCCB coordination and terminals<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td><strong>250A<\/strong><\/td>\r\n          <td>Medium distribution or industrial feeder<\/td>\r\n          <td>Conductors, available fault current, cabinet space and thermal conditions<\/td>\r\n        <\/tr>\r\n      <\/tbody>\r\n    <\/table>\r\n  <\/div>\r\n\r\n  <p class=\"ly-procurement-conclusion\">\r\n    <strong>Procurement conclusion:<\/strong> in the lower and medium-current range, the calculation often identifies a likely rating quickly, but utilization duty, protection and connection details still determine whether the model is actually acceptable.\r\n  <\/p>\r\n\r\n  <h3>400A, 630A and 800A ATS Projects<\/h3>\r\n\r\n  <div class=\"ly-table-wrap\">\r\n    <table class=\"ly-rating-table\">\r\n      <caption>At these current levels, cable layout, protection and cabinet integration usually become more significant.<\/caption>\r\n      <thead>\r\n        <tr>\r\n          <th>ATS Rating<\/th>\r\n          <th>Typical Project Context<\/th>\r\n          <th>What Becomes More Important<\/th>\r\n        <\/tr>\r\n      <\/thead>\r\n      <tbody>\r\n        <tr>\r\n          <td><strong>400A<\/strong><\/td>\r\n          <td>Commercial or industrial distribution<\/td>\r\n          <td>Motor duty, Ie, fault-current rating, protective coordination and cable space<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td><strong>630A<\/strong><\/td>\r\n          <td>Main feeder, generator system or industrial panel<\/td>\r\n          <td>Large terminals, conductor routing, thermal performance and enclosure layout<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td><strong>800A<\/strong><\/td>\r\n          <td>Large LV distribution or generator-backed main feeder<\/td>\r\n          <td>Parallel conductors or busbar interface, WCR \/ short-circuit rating, access and maintenance space<\/td>\r\n        <\/tr>\r\n      <\/tbody>\r\n    <\/table>\r\n  <\/div>\r\n\r\n  <p class=\"ly-procurement-conclusion\">\r\n    <strong>Procurement conclusion:<\/strong> at 400A\u2013800A, two quotations with the same ampere number can represent substantially different electrical and mechanical solutions.\r\n  <\/p>\r\n\r\n  <h3>1600A and 3200A ATS Projects<\/h3>\r\n\r\n  <div class=\"ly-table-wrap\">\r\n    <table class=\"ly-rating-table\">\r\n      <caption>Large-current transfer systems require full switchboard and protection review.<\/caption>\r\n      <thead>\r\n        <tr>\r\n          <th>ATS Rating<\/th>\r\n          <th>Typical Project Context<\/th>\r\n          <th>Engineering Impact<\/th>\r\n        <\/tr>\r\n      <\/thead>\r\n      <tbody>\r\n        <tr>\r\n          <td><strong>1600A<\/strong><\/td>\r\n          <td>Main low-voltage distribution or large standby system<\/td>\r\n          <td>Busbars or parallel cables, ACB\/MCCB coordination, thermal performance, fault-current capability and service access<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td><strong>3200A<\/strong><\/td>\r\n          <td>Large industrial, infrastructure or main LV switchboard application<\/td>\r\n          <td>Full busbar design, protection study, enclosure integration, ventilation, lifting, transport and installation planning<\/td>\r\n        <\/tr>\r\n      <\/tbody>\r\n    <\/table>\r\n  <\/div>\r\n\r\n  <div class=\"ly-engineering\">\r\n    <strong>At 1600A and 3200A, ATS selection becomes a switchboard-engineering decision.<\/strong>\r\n    The current calculation is still necessary, but it is no longer enough for approval. High-current transfer equipment can involve power-frame mechanisms, large busbars, multiple conductors, larger enclosures and significantly different maintenance and installation requirements.\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"15-why-two-400a-ats-units-may-not-be-equivalent\"><\/span>15. Why Two 400A ATS Units May Not Be Equivalent<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    \u201c400A ATS\u201d describes only part of the specification. Two switches with the same headline ampere rating can differ in electrical duty, short-circuit performance and construction.\r\n  <\/p>\r\n\r\n  <div class=\"ly-two-col\">\r\n    <div class=\"ly-mini\">\r\n      <h3>Electrical Ratings<\/h3>\r\n      <ul>\r\n        <li>Rated operational current Ie<\/li>\r\n        <li>Rated operational voltage Ue<\/li>\r\n        <li>Utilization category<\/li>\r\n        <li>Continuous-current condition<\/li>\r\n        <li>Short-circuit \/ WCR characteristics<\/li>\r\n        <li>Frequency<\/li>\r\n        <li>Number of poles<\/li>\r\n      <\/ul>\r\n    <\/div>\r\n\r\n    <div class=\"ly-mini\">\r\n      <h3>Construction &amp; Application<\/h3>\r\n      <ul>\r\n        <li>PC, CB or other architecture<\/li>\r\n        <li>3P or 4P arrangement<\/li>\r\n        <li>Transition method<\/li>\r\n        <li>Terminal or busbar arrangement<\/li>\r\n        <li>Controller functions<\/li>\r\n        <li>Enclosure and mounting design<\/li>\r\n        <li>Maintenance access<\/li>\r\n      <\/ul>\r\n    <\/div>\r\n  <\/div>\r\n\r\n  <p>\r\n    IEC 60947-6-1:2026 is the current fourth edition of the international transfer-switching-equipment standard. It applies to transfer switching equipment including automatic transfer switching equipment and includes provisions covering areas such as bypass\/isolation equipment, closed-transition ATSE and stand-alone ATS controllers.<sup><a href=\"#ats-ref-1\">[1]<\/a><\/sup>\r\n  <\/p>\r\n\r\n  <p>\r\n    For projects requiring UL certification, UL Solutions identifies UL 1008 as the applicable standard for automatic transfer switches used in emergency and optional standby systems, as well as applicable nonautomatic transfer switches.<sup><a href=\"#ats-ref-2\">[2]<\/a><\/sup>\r\n  <\/p>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"16-what-happens-if-the-ats-is-too-small\"><\/span>16. What Happens If the ATS Is Too Small?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    An undersized ATS can create excessive thermal stress, conductor or terminal problems, non-compliance with the required continuous-current condition or unsuitable switching performance for the load.\r\n  <\/p>\r\n\r\n  <p>\r\n    A switch can also be unacceptable even when its operating-current rating appears adequate if its short-circuit capability is insufficient for the installation. Cummins specifically notes that a larger transfer switch may sometimes be required when available fault current exceeds the capability of the smaller unit.<sup><a href=\"#ats-ref-3\">[3]<\/a><\/sup>\r\n  <\/p>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"17-is-an-oversized-ats-always-better\"><\/span>17. Is an Oversized ATS Always Better?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    No. A larger ATS can be justified by future expansion, continuous-load requirements, conductor size, fault-current performance or another documented design condition. But unnecessary oversizing can increase equipment cost and can affect enclosure dimensions, terminals, busbars, installation space, shipping and lead time.\r\n  <\/p>\r\n\r\n  <p>\r\n    Physical size does not always increase one-to-one with amperes. Manufacturers may use one frame for several current ratings, then move to a completely different mechanism or cabinet at a higher threshold.\r\n  <\/p>\r\n\r\n  <div class=\"ly-buyer-meaning\">\r\n    <strong>Buyer meaning<\/strong>\r\n    Ask why the proposed ATS frame was selected. \u201cBigger is safer\u201d is not enough engineering justification.\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"18-how-ats-current-rating-affects-price-and-lead-time\"><\/span>18. How ATS Current Rating Affects Price and Lead Time<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>\r\n    Current rating is one quotation driver, but it is not the only one. Poles, controller, switching mechanism, utilization category, transition type, short-circuit rating, enclosure, terminals, accessories and certification can all affect cost.\r\n  <\/p>\r\n\r\n  <p>\r\n    At higher currents, conductor or busbar arrangements, cabinet manufacturing, protection studies, transportation and site installation can become significant parts of the project.\r\n  <\/p>\r\n\r\n  <p>\r\n    For this reason, a generic \u201c400A ATS price\u201d or \u201c3200A ATS price\u201d cannot reliably compare two suppliers unless the configurations and required ratings are equivalent.\r\n  <\/p>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"19-final-ats-sizing-decision-table\"><\/span>19. Final ATS Sizing Decision Table<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <div class=\"ly-table-wrap\">\r\n    <table class=\"ly-example-table\">\r\n      <caption>Use this sequence before approving a model or requesting a final quotation.<\/caption>\r\n      <thead>\r\n        <tr>\r\n          <th>Decision<\/th>\r\n          <th>What to Confirm<\/th>\r\n          <th>Why It Matters<\/th>\r\n        <\/tr>\r\n      <\/thead>\r\n      <tbody>\r\n        <tr>\r\n          <td>Transferred load<\/td>\r\n          <td>Which loads pass through this ATS?<\/td>\r\n          <td>Prevents sizing from unrelated site or source capacity<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td>Maximum demand<\/td>\r\n          <td>What load can operate simultaneously?<\/td>\r\n          <td>Avoids confusing connected load with real design demand<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td>Electrical system<\/td>\r\n          <td>Voltage, phase and frequency<\/td>\r\n          <td>Defines the current calculation and product suitability<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td>Operating current<\/td>\r\n          <td>Verified amps, kVA or kW + PF<\/td>\r\n          <td>Establishes the basic current requirement<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td>Continuous loading<\/td>\r\n          <td>Applicable code and product declaration<\/td>\r\n          <td>Prevents misuse of universal 80%, 100% or 125% rules<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td>Load duty<\/td>\r\n          <td>Motor, pump, HVAC, transformer or mixed load<\/td>\r\n          <td>Changes switching-duty requirements<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td>Ie \/ utilization<\/td>\r\n          <td>Actual model rating at project voltage and duty<\/td>\r\n          <td>Connects the calculated current to a valid ATS model<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td>Protection<\/td>\r\n          <td>MCCB, ACB, fuse and settings<\/td>\r\n          <td>Required for coordinated protection<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td>Fault current<\/td>\r\n          <td>Available current at ATS location<\/td>\r\n          <td>Ensures WCR or other short-circuit ratings are adequate<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td>Environment<\/td>\r\n          <td>Ambient, enclosure, altitude and ventilation<\/td>\r\n          <td>Confirms rating conditions<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td>Physical design<\/td>\r\n          <td>Poles, cables, busbars, terminals and access<\/td>\r\n          <td>Ensures the switch can actually be integrated<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td>Final approval<\/td>\r\n          <td>Datasheet, standard, certificate and drawing<\/td>\r\n          <td>Turns a preliminary rating into an approved product<\/td>\r\n        <\/tr>\r\n      <\/tbody>\r\n    <\/table>\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"20-information-to-send-before-requesting-an-ats-recommendation\"><\/span>20. Information to Send Before Requesting an ATS Recommendation<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <section class=\"ly-checklist\">\r\n    <h3>ATS Sizing \/ RFQ Checklist<\/h3>\r\n\r\n    <p>\r\n      Providing these details allows the supplier or project engineer to move beyond a simple ampere estimate.\r\n    <\/p>\r\n\r\n    <ul class=\"ly-check-grid\">\r\n      <li>Total connected load<\/li>\r\n      <li>Expected simultaneous or maximum demand<\/li>\r\n      <li>System voltage<\/li>\r\n      <li>Single-phase or three-phase<\/li>\r\n      <li>Frequency<\/li>\r\n      <li>Load power factor, if known<\/li>\r\n      <li>Motor, pump, compressor or HVAC loads<\/li>\r\n      <li>Largest motor rating and starting method<\/li>\r\n      <li>Generator kW \/ kVA<\/li>\r\n      <li>Generator rated current, if available<\/li>\r\n      <li>Normal-source breaker type and rating<\/li>\r\n      <li>Generator-side breaker type and rating<\/li>\r\n      <li>Available fault current, if known<\/li>\r\n      <li>Required 2P \/ 3P \/ 4P configuration<\/li>\r\n      <li>Required transition method<\/li>\r\n      <li>Required utilization category<\/li>\r\n      <li>Required standard or certification<\/li>\r\n      <li>Ambient and installation environment<\/li>\r\n      <li>Cable size or busbar arrangement<\/li>\r\n      <li>Required quantity<\/li>\r\n      <li>OEM label or private-label requirement<\/li>\r\n    <\/ul>\r\n  <\/section>\r\n\r\n  <section class=\"ly-cta\">\r\n    <h3>Need Help Confirming a Compact ATS Configuration?<\/h3>\r\n\r\n    <p>\r\n      LEEYEE's published ATS-63 range covers 6A, 10A, 16A, 20A, 25A, 32A, 40A, 50A and 63A in 2P \/ 4P configurations. Send the voltage, current, phase, backup source and wiring information for model confirmation.\r\n    <\/p>\r\n\r\n    <p class=\"ly-small\">\r\n      For engineered ATS projects above the currently published LEEYEE range, use the sizing method in this guide to prepare the project specification and verify the proposed manufacturer's ratings, dimensions and certification before approval.\r\n    <\/p>\r\n\r\n    <button\r\n      type=\"button\"\r\n      class=\"leeyee-about-btn-light leeyee-site-popup-btn\"\r\n      aria-label=\"Request a Quote\">\r\n      <span class=\"w-btn-label\">Request a Quote<\/span>\r\n    <\/button>\r\n  <\/section>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"21-frequently-asked-ats-sizing-questions\"><\/span>21. Frequently Asked ATS Sizing Questions<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <section class=\"ly-faq\">\r\n\r\n    <div class=\"ly-faq-item\">\r\n      <h3>What size ATS do I need for a 100 kVA generator?<\/h3>\r\n      <p>\r\n        At 400V three phase, 100 kVA corresponds to approximately 144A. A 160A ATS may therefore be a reasonable preliminary candidate if the full 100 kVA can pass through that switch. Final selection still requires maximum demand, continuous-current, utilization-category, protection and fault-current checks.\r\n      <\/p>\r\n    <\/div>\r\n\r\n    <div class=\"ly-faq-item\">\r\n      <h3>Can I choose an ATS from generator kVA alone?<\/h3>\r\n      <p>\r\n        No. Generator kVA describes source capacity. The ATS should be selected for the current and electrical duty that actually pass through that transfer switch.\r\n      <\/p>\r\n    <\/div>\r\n\r\n    <div class=\"ly-faq-item\">\r\n      <h3>What is the difference between connected load and maximum demand?<\/h3>\r\n      <p>\r\n        Connected load is the sum of equipment connected downstream. Maximum demand is the highest simultaneous load expected under the approved design assumptions. ATS sizing should use the project design basis appropriate to the installation rather than assuming every connected load operates at full rating together.\r\n      <\/p>\r\n    <\/div>\r\n\r\n    <div class=\"ly-faq-item\">\r\n      <h3>Should I multiply ATS current by 1.25?<\/h3>\r\n      <p>\r\n        Not automatically. A 125% factor can arise from specific code or continuous-load requirements, but it is not a universal ATS sizing multiplier. Confirm the applicable code, project specification and product rating.\r\n      <\/p>\r\n    <\/div>\r\n\r\n    <div class=\"ly-faq-item\">\r\n      <h3>Does a 400A ATS always have 400A rated operational current?<\/h3>\r\n      <p>\r\n        Do not assume so from the product name alone. Verify the manufacturer's rated operational current Ie, rated voltage, utilization category and any ambient or installation conditions for the exact model.\r\n      <\/p>\r\n    <\/div>\r\n\r\n    <div class=\"ly-faq-item\">\r\n      <h3>Do I size an ATS to motor starting current?<\/h3>\r\n      <p>\r\n        Not by simply using motor starting current as the ATS continuous rating. Start with the normal design load current, then verify motor or mixed-load switching duty, generator transient response and protection coordination.\r\n      <\/p>\r\n    <\/div>\r\n\r\n    <div class=\"ly-faq-item\">\r\n      <h3>Should the ATS ampere rating equal the main breaker rating?<\/h3>\r\n      <p>\r\n        Not as a universal rule. The ATS, conductors and upstream protective devices must be coordinated for load current and fault conditions. Check the actual system architecture and manufacturer documentation.\r\n      <\/p>\r\n    <\/div>\r\n\r\n    <div class=\"ly-faq-item\">\r\n      <h3>Can available fault current force me to choose a larger ATS?<\/h3>\r\n      <p>\r\n        Yes, in some product families. If the smaller ATS does not have adequate tested short-circuit or withstand-and-closing capability, a larger frame or a different protection arrangement may be required even when the normal load current has not increased.\r\n      <\/p>\r\n    <\/div>\r\n\r\n    <div class=\"ly-faq-item\">\r\n      <h3>Does high ambient temperature affect ATS sizing?<\/h3>\r\n      <p>\r\n        It can. Use the selected manufacturer's stated rating and derating information. Do not apply one universal temperature factor to every ATS.\r\n      <\/p>\r\n    <\/div>\r\n\r\n    <div class=\"ly-faq-item\">\r\n      <h3>Is a 630A ATS always physically larger than a 400A ATS?<\/h3>\r\n      <p>\r\n        Not necessarily. Some manufacturers use one frame for several current ratings. Other rating transitions can move to a larger mechanism or enclosure. Confirm actual dimensions and terminals.\r\n      <\/p>\r\n    <\/div>\r\n\r\n    <div class=\"ly-faq-item\">\r\n      <h3>What changes when moving from 800A to 1600A or 3200A?<\/h3>\r\n      <p>\r\n        High-current projects normally require greater attention to busbars or parallel conductors, terminals, enclosure size, thermal design, fault-current performance, ACB\/MCCB coordination, maintenance access and installation logistics.\r\n      <\/p>\r\n    <\/div>\r\n\r\n    <div class=\"ly-faq-item\">\r\n      <h3>Are 63A, 100A, 160A, 250A, 400A, 630A, 800A, 1600A and 3200A universal ATS sizes?<\/h3>\r\n      <p>\r\n        No. They are useful market and engineering reference ratings, but available current steps and physical frame sizes vary by manufacturer and product family.\r\n      <\/p>\r\n    <\/div>\r\n\r\n    <div class=\"ly-faq-item\">\r\n      <h3>Is a larger ATS always safer?<\/h3>\r\n      <p>\r\n        No. The ATS must have adequate current and fault capability, but unnecessary oversizing can increase cost, cabinet space and integration requirements without solving a real engineering problem.\r\n      <\/p>\r\n    <\/div>\r\n\r\n  <\/section>\r\n\r\n  <section class=\"ly-related\">\r\n    <h2><span class=\"ez-toc-section\" id=\"related-ats-reading\"><\/span>Related ATS Reading<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n    <ul>\r\n      <li>\r\n        <a href=\"https:\/\/www.cnspd.com\/what-is-an-automatic-transfer-switch-how-ats-works-how-to-choose\/\">\r\n          What Is an Automatic Transfer Switch? How ATS Works &amp; How to Choose\r\n        <\/a>\r\n        \u2014 use this for ATS operating principle, pole selection and general application basics.\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.cnspd.com\/products\/leeyee-automatic-transfer-switch-solar-backup\/\">\r\n          LEEYEE ATS-63 Automatic Transfer Switch\r\n        <\/a>\r\n        \u2014 published specifications for the current 6A\u201363A compact 2P \/ 4P ATS range.\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.cnspd.com\/shop\/all-products\/\">\r\n          LEEYEE All Products\r\n        <\/a>\r\n        \u2014 browse switching, isolation and low-voltage protection product categories.\r\n      <\/li>\r\n    <\/ul>\r\n  <\/section>\r\n\r\n  <section class=\"ly-references\">\r\n    <h2><span class=\"ez-toc-section\" id=\"references\"><\/span>References<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n    <ol>\r\n      <li id=\"ats-ref-1\">\r\n        <strong>International Electrotechnical Commission.<\/strong>\r\n        IEC 60947-6-1:2026,\r\n        <em>Low-voltage switchgear and controlgear \u2013 Part 6-1: Multiple function equipment \u2013 Transfer switching equipment<\/em>,\r\n        Edition 4.0, published 2 April 2026.\r\n        <a href=\"https:\/\/webstore.iec.ch\/en\/publication\/90494\" target=\"_blank\" rel=\"noopener noreferrer\">IEC official publication page<\/a>.\r\n      <\/li>\r\n\r\n      <li id=\"ats-ref-2\">\r\n        <strong>UL Solutions.<\/strong>\r\n        <em>Switch Certification and Evaluation Services<\/em>. UL identifies UL 1008 for automatic transfer switches used in emergency systems and optional standby systems, and for applicable nonautomatic transfer switches.\r\n        <a href=\"https:\/\/www.ul.com\/services\/switch-certification-and-evaluation-services\" target=\"_blank\" rel=\"noopener noreferrer\">UL Solutions official page<\/a>.\r\n      <\/li>\r\n\r\n      <li id=\"ats-ref-3\">\r\n        <strong>Cummins Power Generation.<\/strong>\r\n        T-011,\r\n        <em>Transfer Switch Application Manual<\/em>,\r\n        A048F226, Issue 4. Relevant sections include continuous current, switching motor loads, IEC utilization categories, cable\/terminal considerations and short-circuit protection.\r\n        <a href=\"https:\/\/www.cummins.com\/sites\/default\/files\/2024-08\/t011-Transfer-switch-application-manual.pdf\" target=\"_blank\" rel=\"noopener noreferrer\">Cummins application manual PDF<\/a>.\r\n      <\/li>\r\n\r\n      <li id=\"ats-ref-4\">\r\n        <strong>Eaton.<\/strong>\r\n        <em>Fundamentals of Automatic Transfer Switches<\/em>. Technical guidance covering ATS mechanisms, applications and Withstand and Closing Rating considerations.\r\n        <a href=\"https:\/\/www.eaton.com\/us\/en-us\/products\/low-voltage-power-distribution-control-systems\/automatic-transfer-switches\/automatic-transfer-switch-fundamentals.html\" target=\"_blank\" rel=\"noopener noreferrer\">Eaton ATS fundamentals<\/a>.\r\n      <\/li>\r\n\r\n      <li id=\"ats-ref-5\">\r\n        <strong>Tri-Service Electrical Working Group \/ Whole Building Design Guide.<\/strong>\r\n        <em>TSEWG TP-1 Electrical Calculation Examples<\/em>, ATS sizing example for a 208Y\/120V three-phase circuit. The example calculates a 545A continuous load, selects a 600A ATS and separately calls for manufacturer verification of motor inrush suitability.\r\n        <a href=\"https:\/\/www.wbdg.org\/FFC\/DOD\/STC\/twewg_tp1.pdf\" target=\"_blank\" rel=\"noopener noreferrer\">WBDG \/ U.S. DoD calculation example PDF<\/a>.\r\n      <\/li>\r\n\r\n      <li id=\"ats-ref-6\">\r\n        <strong>LEEYEE.<\/strong>\r\n        <em>ATS-63 Automatic Transfer Switch for Backup Power<\/em>. Current published product data includes 6A\u201363A rated operational current options and 2P \/ 4P configurations.\r\n        <a href=\"https:\/\/www.cnspd.com\/products\/leeyee-automatic-transfer-switch-solar-backup\/\" target=\"_blank\" rel=\"noopener noreferrer\">LEEYEE ATS-63 product page<\/a>.\r\n      <\/li>\r\n    <\/ol>\r\n\r\n    <p class=\"ly-small\">\r\n      Standards, national adoptions, certification records and product data can be revised. Confirm the applicable edition, local requirements, project specification and exact manufacturer model documentation before final engineering approval, procurement or installation.\r\n    <\/p>\r\n  <\/section>\r\n\r\n  <p class=\"ly-brand-note\">\r\n    LEEYEE \u00b7 Built to Protect. Trusted to Last. CNSPD is LEEYEE's surge-protection-focused technical and product platform for global buyers. ATS recommendations must be confirmed against the actual project and the specific product documentation submitted for approval.\r\n  <\/p>\r\n\r\n  <script>\r\n  document.addEventListener('DOMContentLoaded', function () {\r\n    var aboutPopupButtons = document.querySelectorAll('.leeyee-site-popup-btn');\r\n\r\n    aboutPopupButtons.forEach(function (button) {\r\n      button.addEventListener('click', function () {\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  });\r\n  <\/script>\r\n\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>Automatic transfer switch sizing starts with the current that will actually pass through the ATS, but it does not end there. A reliable selection must also consider maximum demand, continuous loading, motors and other inductive loads, generator capability, rated operational current, utilization category, protective-device coordination, available fault current, temperature, terminals and switchboard integration. Need the&#8230;<\/p>","protected":false},"author":18,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[490,1,422],"tags":[],"class_list":["post-31089","post","type-post","status-publish","format-standard","hentry","category-isolator-switching","category-news","category-industry-news"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.3 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Automatic Transfer Switch Sizing Guide: 63A\u20133200A ATS<\/title>\n<meta name=\"description\" content=\"Learn how to size an automatic transfer switch from 63A to 3200A using load current, maximum demand, motors, generator capacity, Ie, breakers and fault current.\" \/>\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\/pt\/automatic-transfer-switch-sizing-guide\/\" \/>\n<meta property=\"og:locale\" content=\"pt_PT\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Automatic Transfer Switch Sizing Guide: 63A\u20133200A ATS\" \/>\n<meta property=\"og:description\" content=\"Learn how to size an automatic transfer switch from 63A to 3200A using load current, maximum demand, motors, generator capacity, Ie, breakers and fault current.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.cnspd.com\/pt\/automatic-transfer-switch-sizing-guide\/\" \/>\n<meta property=\"og:site_name\" content=\"Surge Protector, Surge Arrestor, Isolating Switch - LEEYEE\" \/>\n<meta property=\"article:published_time\" content=\"2026-09-16T01:13:04+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2026-09-16T01:13:33+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/09\/ats-sizing-decision-flow.webp\" \/>\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=\"20 minutos\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/automatic-transfer-switch-sizing-guide\\\/#article\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/automatic-transfer-switch-sizing-guide\\\/\"},\"author\":{\"name\":\"Devin Ling\",\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/#\\\/schema\\\/person\\\/f49dbafe62c5b47100ad2d9f88af92d3\"},\"headline\":\"Automatic Transfer Switch Sizing: What Size ATS Do I Need? 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