{"id":31234,"date":"2026-09-21T14:33:11","date_gmt":"2026-09-21T06:33:11","guid":{"rendered":"https:\/\/www.cnspd.com\/?p=31234"},"modified":"2026-09-21T14:34:22","modified_gmt":"2026-09-21T06:34:22","slug":"automatic-transfer-switch-for-main-distribution-boards-compact-mdb-ats-selection-guide","status":"publish","type":"post","link":"https:\/\/www.cnspd.com\/id\/automatic-transfer-switch-main-distribution-board\/","title":{"rendered":"Automatic Transfer Switch for Main Distribution Boards: Compact MDB ATS Selection Guide"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"31234\" class=\"elementor elementor-31234\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-efeea3f e-flex e-con-boxed e-con e-parent\" data-id=\"efeea3f\" 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-e70bfd1 elementor-widget 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the complete power-distribution design, not as an isolated switch. For panel builders, electrical contractors, generator integrators and project buyers, the key questions are where the transfer point is located, which loads actually require standby power, what current the ATS must carry, and how the neutral, protection and alternate source are arranged.<\/p>\r\n\r\n  <p class=\"ly-intro\">This guide focuses on compact automatic transfer switches used in suitable low-voltage MDB sections and essential-load distribution. It keeps the MDB engineering perspective while separating standard compact ATS applications from larger switchgear architectures that require different equipment or a project-specific solution.<\/p>\r\n\r\n  <div class=\"ly-quick\">\r\n    <span class=\"ly-kicker\">Quick Answer<\/span>\r\n    <strong class=\"ly-lead\">A compact ATS can be integrated into a suitable MDB or essential-load section when its declared current, poles, short-circuit application conditions, source arrangement and transfer function match the project.<\/strong>\r\n    <p>Do not select the ATS from the MDB current label alone. Confirm the single-line diagram, transferred load, prospective fault conditions, upstream protection, 3P\/4P requirement, neutral and earthing arrangement, generator data and the actual ratings of the selected ATS.<sup><a href=\"#ref-1\">[1]<\/a><\/sup><sup><a href=\"#ref-2\">[2]<\/a><\/sup><sup><a href=\"#ref-3\">[3]<\/a><\/sup><\/p>\r\n  <\/div>\r\n\r\n  <div class=\"ly-scope\">\r\n    <strong>LEEYEE product scope on this page:<\/strong>\r\n    LEEYEE's standard offering is a compact integrated ATS format for normal two-source low-voltage transfer applications. The standard product direction is conventional open-transition switching, with pole and current options selected according to the actual model. Closed-transition systems, Class CB architectures, bypass-isolation systems and large switchboard transfer schemes should be treated as separate engineered configurations rather than assumed to be functions of the standard compact ATS.\r\n  <\/div>\r\n\r\n  <div class=\"ly-table-wrap\">\r\n    <p class=\"ly-table-note\">For a compact ATS in an MDB, these are the first project inputs to confirm.<\/p>\r\n    <table aria-label=\"Compact ATS selection factors for main distribution boards\">\r\n      <thead>\r\n        <tr>\r\n          <th>Decision item<\/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 data-label=\"Decision item\"><strong>Source arrangement<\/strong><\/td>\r\n          <td data-label=\"Confirm\">Utility\u2013generator or utility\u2013utility<\/td>\r\n          <td data-label=\"Why it matters\">Changes source monitoring and transfer logic<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Decision item\"><strong>Transferred load<\/strong><\/td>\r\n          <td data-label=\"Confirm\">Whole suitable section or selected essential loads<\/td>\r\n          <td data-label=\"Why it matters\">Defines the real current requirement<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Decision item\"><strong>Design current<\/strong><\/td>\r\n          <td data-label=\"Confirm\">Actual load\/design current<\/td>\r\n          <td data-label=\"Why it matters\">Must remain within the selected ATS rating and application conditions<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Decision item\"><strong>Short-circuit conditions<\/strong><\/td>\r\n          <td data-label=\"Confirm\">Prospective fault current and upstream protection<\/td>\r\n          <td data-label=\"Why it matters\">Current rating alone does not prove fault suitability<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Decision item\"><strong>Poles and neutral<\/strong><\/td>\r\n          <td data-label=\"Confirm\">2P \/ 3P \/ 4P and neutral strategy<\/td>\r\n          <td data-label=\"Why it matters\">Neutral switching depends on the actual system design<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Decision item\"><strong>Generator data<\/strong><\/td>\r\n          <td data-label=\"Confirm\">Voltage, frequency, capacity, neutral and start interface<\/td>\r\n          <td data-label=\"Why it matters\">The alternate source must be acceptable before transfer<\/td>\r\n        <\/tr>\r\n        <tr>\r\n          <td data-label=\"Decision item\"><strong>MDB integration<\/strong><\/td>\r\n          <td data-label=\"Confirm\">Busbar, cables, enclosure, access and thermal conditions<\/td>\r\n          <td data-label=\"Why it matters\">The ATS becomes part of the complete assembly<\/td>\r\n        <\/tr>\r\n      <\/tbody>\r\n    <\/table>\r\n    <p class=\"ly-table-conclusion\">Procurement conclusion: select the compact ATS from the actual transfer point and load, not from the total MDB nameplate rating alone.<\/p>\r\n  <\/div>\r\n\r\n  <figure class=\"ly-figure\">\r\n    <img fetchpriority=\"high\" src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/09\/ats-position-main-distribution-board.webp\" width=\"1448\" height=\"1086\" loading=\"eager\" decoding=\"async\" alt=\"Automatic transfer switch position in a main distribution board with utility, generator, ATS, busbar and essential loads\">\r\n    <figcaption>A compact ATS may feed a suitable MDB section or an essential-load bus. It does not automatically need to transfer every circuit connected to the main distribution board.<\/figcaption>\r\n  <\/figure>\r\n\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\/id\/automatic-transfer-switch-main-distribution-board\/#where-should-a-compact-ats-sit-in-an-mdb\" >Where should a compact ATS sit in an MDB?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/automatic-transfer-switch-main-distribution-board\/#utility%e2%80%93generator-or-utility%e2%80%93utility\" >Utility\u2013generator or utility\u2013utility?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/automatic-transfer-switch-main-distribution-board\/#how-should-ats-current-be-matched-to-the-mdb\" >How should ATS current be matched to the MDB?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/automatic-transfer-switch-main-distribution-board\/#why-short-circuit-conditions-still-matter-for-a-compact-ats\" >Why short-circuit conditions still matter for a compact ATS<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/automatic-transfer-switch-main-distribution-board\/#is-this-a-class-pc-or-class-cb-application\" >Is this a Class PC or Class CB application?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/automatic-transfer-switch-main-distribution-board\/#open-transition-is-the-relevant-standard-configuration\" >Open transition is the relevant standard configuration<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/automatic-transfer-switch-main-distribution-board\/#a-practical-compact-ats-selection-workflow-for-an-mdb\" >A practical compact ATS selection workflow for an MDB<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/automatic-transfer-switch-main-distribution-board\/#does-a-three-phase-four-wire-mdb-always-need-a-4-pole-ats\" >Does a three-phase four-wire MDB always need a 4-pole ATS?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/automatic-transfer-switch-main-distribution-board\/#can-a-compact-ats-be-installed-inside-the-mdb\" >Can a compact ATS be installed inside the MDB?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/automatic-transfer-switch-main-distribution-board\/#which-generator-information-should-be-confirmed\" >Which generator information should be confirmed?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/automatic-transfer-switch-main-distribution-board\/#what-should-you-send-before-requesting-a-compact-mdb-ats\" >What should you send before requesting a compact MDB ATS?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/automatic-transfer-switch-main-distribution-board\/#need-help-confirming-a-compact-ats-for-your-mdb\" >Need help confirming a compact ATS for your MDB?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/automatic-transfer-switch-main-distribution-board\/#faq-for-compact-ats-selection-in-an-mdb\" >FAQ for compact ATS selection in an MDB<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/id\/automatic-transfer-switch-main-distribution-board\/#references\" >References<\/a><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"where-should-a-compact-ats-sit-in-an-mdb\"><\/span>Where should a compact ATS sit in an MDB?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>The best location depends on which loads need an alternate source. In many projects, the useful question is not \u201cDoes the MDB need an ATS?\u201d but \u201cWhich part of the MDB must remain supplied when the normal source fails?\u201d<\/p>\r\n\r\n  <div class=\"ly-grid-2\">\r\n    <div class=\"ly-mini\">\r\n      <h3>Selected MDB section<\/h3>\r\n      <p>A compact ATS can supply a defined section when the transferred load and fault conditions remain within the selected device's declared ratings.<\/p>\r\n    <\/div>\r\n    <div class=\"ly-mini\">\r\n      <h3>Essential-load bus<\/h3>\r\n      <p>The ATS transfers only critical circuits such as selected controls, lighting, pumps or other project-defined essential loads. This can avoid sizing the standby source for every outgoing circuit.<\/p>\r\n    <\/div>\r\n  <\/div>\r\n\r\n  <p>Eaton's ATS guidance describes both utility\u2013generator and utility\u2013utility applications and shows why transferred loads and source availability must be defined as part of the power architecture.<sup><a href=\"#ref-4\">[4]<\/a><\/sup><\/p>\r\n\r\n  <div class=\"ly-note\"><strong>Engineering note:<\/strong> A compact ATS should not be presented as a universal replacement for a high-current main-incomer transfer system. If the project fault level, current, protection architecture or switchboard arrangement exceeds the selected ATS's declared application range, a different engineered solution is required.<\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"utility%e2%80%93generator-or-utility%e2%80%93utility\"><\/span>Utility\u2013generator or utility\u2013utility?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>LEEYEE's compact ATS format is most naturally applied to conventional two-source transfer arrangements. The two most relevant MDB scenarios are utility\u2013generator and utility\u2013utility.<\/p>\r\n\r\n  <div class=\"ly-grid-2\">\r\n    <div class=\"ly-mini\">\r\n      <h3>Utility\u2013Generator<\/h3>\r\n      <p>The ATS monitors source availability and transfers the load after the alternate source reaches acceptable operating conditions. Generator start and stop logic must be coordinated with the controller and genset interface.<\/p>\r\n    <\/div>\r\n    <div class=\"ly-mini\">\r\n      <h3>Utility\u2013Utility<\/h3>\r\n      <p>There is no generator start sequence, but source priority, acceptable source conditions, transfer delay and retransfer logic still need to be defined.<\/p>\r\n    <\/div>\r\n  <\/div>\r\n\r\n  <div class=\"ly-buyer\"><strong>Buyer meaning:<\/strong> Do not send only \u201cneed ATS for MDB.\u201d State the two sources, the transferred load and whether the alternate source is a generator or another utility\/feed.<\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"how-should-ats-current-be-matched-to-the-mdb\"><\/span>How should ATS current be matched to the MDB?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>The ATS current rating should match the actual transferred load, not automatically the full MDB busbar rating. If only an essential-load section is transferred, the relevant current is the load that passes through the ATS under normal and alternate-source operation.<\/p>\r\n\r\n  <p>The selected ATS must also remain within the manufacturer's declared service conditions. When the ATS is built into an MDB, the complete switchboard still has its own assembly requirements under IEC 61439 where applicable.<sup><a href=\"#ref-2\">[2]<\/a><\/sup><sup><a href=\"#ref-3\">[3]<\/a><\/sup><\/p>\r\n\r\n  <div class=\"ly-warning\"><strong>Do not oversize the application on paper.<\/strong> A compact ATS should only be used where the selected model's declared current, voltage, poles, utilization and short-circuit application data are suitable for the real transfer point.<\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"why-short-circuit-conditions-still-matter-for-a-compact-ats\"><\/span>Why short-circuit conditions still matter for a compact ATS<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>A compact size does not remove the need to check fault conditions. Rated current describes normal load carrying. Short-circuit performance addresses a different operating condition.<\/p>\r\n\r\n  <p>For an MDB application, compare the prospective short-circuit current at the ATS location and the upstream protective arrangement with the selected transfer equipment's declared data. IEC 60947-6-1:2026 is the current IEC product standard for transfer switching equipment within its stated scope.<sup><a href=\"#ref-1\">[1]<\/a><\/sup><\/p>\r\n\r\n  <div class=\"ly-buyer\"><strong>Buyer meaning:<\/strong> If the project has a high fault level near the transformer or main incomer, do not assume a compact ATS is suitable because its current rating matches the load. Ask for model-specific short-circuit application data first.<\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"is-this-a-class-pc-or-class-cb-application\"><\/span>Is this a Class PC or Class CB application?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>Class PC and Class CB describe different transfer-switch architectures. They should not be treated as quality levels.<\/p>\r\n\r\n  <p>LEEYEE's standard compact ATS direction is based on compact switching equipment rather than a circuit-breaker-based Class CB architecture. The exact classification and ratings of the model being quoted should still be confirmed from its technical documentation.<\/p>\r\n\r\n  <p>Class CB systems use circuit-breaker-based transfer architectures and can be appropriate in other MDB designs, but that does not mean the standard compact LEEYEE ATS should be presented as a Class CB product. Schneider Electric's current TransferPacT information shows the structural distinction between breaker-based Class CB and switch-disconnector-based Class PC arrangements.<sup><a href=\"#ref-5\">[5]<\/a><\/sup><\/p>\r\n\r\n  <div class=\"ly-note\"><strong>Scope boundary:<\/strong> This page explains Class CB because buyers may encounter it in MDB design. It is not being presented here as the standard LEEYEE compact ATS configuration.<\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"open-transition-is-the-relevant-standard-configuration\"><\/span>Open transition is the relevant standard configuration<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>For the standard compact LEEYEE ATS discussed on this page, the practical reference is conventional open-transition switching: one source is disconnected before the other source is connected.<\/p>\r\n\r\n  <p>This break-before-make behaviour is different from closed transition, where two acceptable sources are momentarily paralleled under controlled conditions. Closed-transition systems require additional equipment capabilities, source conditions and project review.<sup><a href=\"#ref-6\">[6]<\/a><\/sup><\/p>\r\n\r\n  <div class=\"ly-warning\"><strong>Important product boundary:<\/strong> Do not interpret this compact ATS page as an offer of a standard closed-transition product. Closed transition, bypass isolation and similar advanced switching architectures require separate engineering confirmation and are not the normal configuration represented by the compact ATS shown in this product family.<\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"a-practical-compact-ats-selection-workflow-for-an-mdb\"><\/span>A practical compact ATS selection workflow for an MDB<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <figure class=\"ly-figure\">\r\n    <img loading=\"lazy\" src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/09\/mdb-ats-selection-workflow.webp\" width=\"1448\" height=\"1086\" loading=\"lazy\" decoding=\"async\" alt=\"Main distribution board ATS selection workflow covering sources, current, short-circuit level, poles, neutral and generator data\">\r\n    <figcaption>Start with the source and transferred load, then confirm current, fault conditions, poles, neutral and generator information before fixing the compact ATS model.<\/figcaption>\r\n  <\/figure>\r\n\r\n  <ol class=\"ly-steps\">\r\n    <li><strong>Read the single-line diagram.<\/strong> Identify the normal source, alternate source and intended transfer point.<\/li>\r\n    <li><strong>Define which loads must transfer.<\/strong> Separate the actual standby load from loads that do not need alternate-source supply.<\/li>\r\n    <li><strong>Calculate or confirm the transferred design current.<\/strong> Do not automatically use the full MDB busbar rating.<\/li>\r\n    <li><strong>Check prospective short-circuit conditions.<\/strong> Compare project fault conditions and upstream protection with the selected ATS data.<\/li>\r\n    <li><strong>Confirm the required poles.<\/strong> Decide 2P, 3P or 4P from the actual system and neutral design.<\/li>\r\n    <li><strong>Confirm open-transition operation.<\/strong> If the project requires closed transition, treat it as a different engineered solution.<\/li>\r\n    <li><strong>Confirm generator and control requirements.<\/strong> Provide voltage, frequency, neutral arrangement and required start interface.<\/li>\r\n    <li><strong>Verify integration into the MDB.<\/strong> Check enclosure space, busbars, wiring, cable access, thermal conditions and maintenance access.<\/li>\r\n  <\/ol>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"does-a-three-phase-four-wire-mdb-always-need-a-4-pole-ats\"><\/span>Does a three-phase four-wire MDB always need a 4-pole ATS?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>No. A three-phase four-wire system does not automatically mean every project requires a switched neutral.<\/p>\r\n\r\n  <p>The decision depends on the normal and alternate source grounding arrangements, neutral bonding and any ground-fault protection or sensing affected by source transfer. Schneider Electric's ASCO guidance explains that solid-neutral versus switched-neutral selection depends on the distribution system and the grounding of the alternate source.<sup><a href=\"#ref-7\">[7]<\/a><\/sup><\/p>\r\n\r\n  <figure class=\"ly-figure\">\r\n    <img loading=\"lazy\" src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/09\/3p-4p-ats-neutral-decision.webp\" width=\"1448\" height=\"1086\" loading=\"lazy\" decoding=\"async\" alt=\"Decision diagram for choosing 3-pole or 4-pole ATS based on neutral, generator grounding and earthing arrangement\">\r\n    <figcaption>A 4-pole ATS can switch the neutral together with the phase conductors, but the project should first confirm whether neutral switching is actually required.<\/figcaption>\r\n  <\/figure>\r\n\r\n  <div class=\"ly-warning\"><strong>Project confirmation required:<\/strong> Do not choose 3P or 4P only from the words \u201cthree-phase four-wire.\u201d Review source grounding, neutral bonding, protection and local project requirements.<\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"can-a-compact-ats-be-installed-inside-the-mdb\"><\/span>Can a compact ATS be installed inside the MDB?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>Yes, when the selected ATS is suitable for the actual current and fault conditions and the panel is designed around the device. This is one of the most relevant uses of the compact ATS format.<\/p>\r\n\r\n  <p>The ATS can be mounted as a transfer component within a suitable MDB section or an essential distribution section. The panel builder must still coordinate busbars, incoming and outgoing conductors, enclosure space, heat dissipation, wiring access and maintenance clearance.<\/p>\r\n\r\n  <p>IEC 61439-2 covers power switchgear and controlgear assemblies within its stated scope. Compliance of the ATS component does not automatically establish compliance of the finished MDB assembly.<sup><a href=\"#ref-3\">[3]<\/a><\/sup><\/p>\r\n\r\n  <div class=\"ly-scope\">\r\n    <strong>What LEEYEE is supplying in this context:<\/strong>\r\n    the compact ATS is the transfer device to be integrated into the customer's suitable panel design. A large dedicated ATS switchboard, circuit-breaker transfer lineup, bypass-isolation system or multi-section Main-Tie-Main switchgear arrangement should not be assumed to be the standard product represented by this page.\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"which-generator-information-should-be-confirmed\"><\/span>Which generator information should be confirmed?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>For a generator-backed MDB section, the ATS supplier should receive enough information to confirm whether the alternate source and control interface match the selected product.<\/p>\r\n\r\n  <ul>\r\n    <li>Generator rated voltage<\/li>\r\n    <li>Frequency<\/li>\r\n    <li>Rated power or available current<\/li>\r\n    <li>Neutral arrangement<\/li>\r\n    <li>Start \/ stop signal requirement<\/li>\r\n    <li>Required transfer and retransfer delays<\/li>\r\n    <li>Critical motors or other high-inrush loads<\/li>\r\n  <\/ul>\r\n\r\n  <p>The generator must reach acceptable operating conditions before the load is transferred. The exact voltage\/frequency acceptance thresholds and delays should follow the selected controller, generator system and project requirements rather than be invented as universal values.<sup><a href=\"#ref-4\">[4]<\/a><\/sup><\/p>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"what-should-you-send-before-requesting-a-compact-mdb-ats\"><\/span>What should you send before requesting a compact MDB ATS?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <p>A good quotation starts with the single-line diagram and the actual transfer point. This prevents the ATS from being selected only from a current value with no information about the source, fault conditions or neutral.<\/p>\r\n\r\n  <figure class=\"ly-figure\">\r\n    <img loading=\"lazy\" src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/09\/mdb-ats-quotation-information.webp\" width=\"1448\" height=\"1086\" loading=\"lazy\" decoding=\"async\" alt=\"Information required for an MDB ATS quotation including single-line diagram, current, short-circuit level, generator and earthing data\">\r\n    <figcaption>For a compact MDB ATS enquiry, the single-line diagram plus source, load, fault and neutral information gives LEEYEE a much better basis for model confirmation.<\/figcaption>\r\n  <\/figure>\r\n\r\n  <div class=\"ly-checklist\">\r\n    <span class=\"ly-kicker\">Before Ordering \/ Project Review<\/span>\r\n    <h3>Prepare these items before fixing the ATS model<\/h3>\r\n    <ul class=\"ly-check-grid\">\r\n      <li>Single-line diagram<\/li>\r\n      <li>System voltage and frequency<\/li>\r\n      <li>Utility\u2013generator or utility\u2013utility arrangement<\/li>\r\n      <li>Actual transferred-load current<\/li>\r\n      <li>MDB busbar rating<\/li>\r\n      <li>Prospective short-circuit current at the ATS location<\/li>\r\n      <li>Upstream breaker or fuse information<\/li>\r\n      <li>2P \/ 3P \/ 4P requirement<\/li>\r\n      <li>Earthing arrangement<\/li>\r\n      <li>Neutral switching requirement<\/li>\r\n      <li>Generator voltage and frequency<\/li>\r\n      <li>Generator rated power or available current<\/li>\r\n      <li>Generator neutral arrangement<\/li>\r\n      <li>Start \/ stop interface requirement<\/li>\r\n      <li>Transferred-load list<\/li>\r\n      <li>Required transfer\/retransfer logic<\/li>\r\n      <li>Required standard or certificate<\/li>\r\n      <li>Quantity and OEM requirements<\/li>\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <div class=\"ly-cta\">\r\n    <h2><span class=\"ez-toc-section\" id=\"need-help-confirming-a-compact-ats-for-your-mdb\"><\/span>Need help confirming a compact ATS for your MDB?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n    <p>Send LEEYEE your single-line diagram, transferred-load current, source arrangement, short-circuit information, pole requirement, neutral\/earthing details and generator data. We can review which standard compact ATS configuration should be considered for the project.<\/p>\r\n    <button type=\"button\"\r\n            class=\"leeyee-about-btn-light leeyee-site-popup-btn\"\r\n            aria-label=\"Request an MDB ATS Configuration Review\">\r\n      <span class=\"w-btn-label\">Request an MDB ATS Configuration Review<\/span>\r\n    <\/button>\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"faq-for-compact-ats-selection-in-an-mdb\"><\/span>FAQ for compact ATS selection in an MDB<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <div class=\"ly-faq\">\r\n\r\n    <details>\r\n      <summary>Can a compact ATS be used in a main distribution board?<\/summary>\r\n      <div class=\"ly-faq-answer\">\r\n        <p>Yes, when the selected transfer point, load current, short-circuit conditions, poles, voltage and source arrangement are within the selected ATS's declared application limits. In many projects the compact ATS is more naturally used for a suitable MDB section or essential-load bus than for a very high-current main incomer.<\/p>\r\n      <\/div>\r\n    <\/details>\r\n\r\n    <details>\r\n      <summary>Should the ATS transfer the entire MDB?<\/summary>\r\n      <div class=\"ly-faq-answer\">\r\n        <p>Not necessarily. If only essential loads require backup power, the ATS can be applied to a dedicated essential-load section. The project single-line diagram should define which circuits really need to transfer.<\/p>\r\n      <\/div>\r\n    <\/details>\r\n\r\n    <details>\r\n      <summary>Can I select the ATS only from the MDB current rating?<\/summary>\r\n      <div class=\"ly-faq-answer\">\r\n        <p>No. Confirm the actual transferred load, prospective short-circuit conditions, upstream protection, poles, neutral arrangement and source information. A matching ampere number alone does not prove suitability.<\/p>\r\n      <\/div>\r\n    <\/details>\r\n\r\n    <details>\r\n      <summary>Is the standard LEEYEE compact ATS a Class CB solution?<\/summary>\r\n      <div class=\"ly-faq-answer\">\r\n        <p>The standard compact ATS should not be presented as a circuit-breaker-based Class CB transfer architecture. Confirm the exact classification of the selected LEEYEE model from its current technical documentation before project approval.<\/p>\r\n      <\/div>\r\n    <\/details>\r\n\r\n    <details>\r\n      <summary>Does the standard compact ATS use closed transition?<\/summary>\r\n      <div class=\"ly-faq-answer\">\r\n        <p>The standard product direction discussed on this page is conventional open-transition transfer. Closed-transition systems require a different engineered configuration and should not be assumed from the standard compact ATS.<\/p>\r\n      <\/div>\r\n    <\/details>\r\n\r\n    <details>\r\n      <summary>Does a three-phase four-wire MDB always need a 4-pole ATS?<\/summary>\r\n      <div class=\"ly-faq-answer\">\r\n        <p>No. Pole selection depends on whether the neutral must remain connected or be switched, together with the grounding and protection arrangement of both sources.<sup><a href=\"#ref-7\">[7]<\/a><\/sup><\/p>\r\n      <\/div>\r\n    <\/details>\r\n\r\n    <details>\r\n      <summary>Why must short-circuit conditions be checked?<\/summary>\r\n      <div class=\"ly-faq-answer\">\r\n        <p>Because continuous-current rating and fault performance are different characteristics. A compact ATS should only be applied where its declared short-circuit conditions match the actual installation and associated protection.<sup><a href=\"#ref-1\">[1]<\/a><\/sup><\/p>\r\n      <\/div>\r\n    <\/details>\r\n\r\n    <details>\r\n      <summary>Can the compact ATS be built into an IEC 61439 MDB?<\/summary>\r\n      <div class=\"ly-faq-answer\">\r\n        <p>It can be integrated into a suitable assembly, but the completed MDB still needs to be designed and verified according to the applicable assembly requirements. Component compliance alone does not establish compliance of the finished switchboard.<sup><a href=\"#ref-2\">[2]<\/a><\/sup><sup><a href=\"#ref-3\">[3]<\/a><\/sup><\/p>\r\n      <\/div>\r\n    <\/details>\r\n\r\n  <\/div>\r\n\r\n  <h2><span class=\"ez-toc-section\" id=\"references\"><\/span>References<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n  <ol class=\"ly-refs\">\r\n    <li id=\"ref-1\">\r\n      <strong>International Electrotechnical Commission (IEC).<\/strong>\r\n      IEC 60947-6-1:2026,\r\n      <em>Low-voltage switchgear and controlgear \u2014 Part 6-1: Multiple function equipment \u2014 Transfer switching equipment<\/em>.\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=\"ref-2\">\r\n      <strong>International Electrotechnical Commission (IEC).<\/strong>\r\n      IEC 61439-1:2020,\r\n      <em>Low-voltage switchgear and controlgear assemblies \u2014 Part 1: General rules<\/em>.\r\n      <a href=\"https:\/\/webstore.iec.ch\/en\/publication\/32338\" target=\"_blank\" rel=\"noopener noreferrer\">IEC official publication page<\/a>.\r\n    <\/li>\r\n\r\n    <li id=\"ref-3\">\r\n      <strong>International Electrotechnical Commission (IEC).<\/strong>\r\n      IEC 61439-2:2020,\r\n      <em>Low-voltage switchgear and controlgear assemblies \u2014 Part 2: Power switchgear and controlgear assemblies<\/em>.\r\n      <a href=\"https:\/\/webstore.iec.ch\/en\/publication\/30043\" target=\"_blank\" rel=\"noopener noreferrer\">IEC official publication page<\/a>.\r\n    <\/li>\r\n\r\n    <li id=\"ref-4\">\r\n      <strong>Eaton.<\/strong>\r\n      <em>Fundamentals of Automatic Transfer Switches (ATS)<\/em>.\r\n      Official technical guidance covering utility\u2013generator and utility\u2013utility applications, source monitoring and transfer sequence.\r\n      <a href=\"https:\/\/www.eaton.com\/sg\/en-us\/products\/low-voltage-power-distribution-control-systems\/automatic-transfer-switches\/automatic-transfer-switch-fundamentals.html\" target=\"_blank\" rel=\"noopener noreferrer\">Eaton technical guide<\/a>.\r\n    <\/li>\r\n\r\n    <li id=\"ref-5\">\r\n      <strong>Schneider Electric.<\/strong>\r\n      <em>Source Changeover Switches \/ TransferPacT<\/em>.\r\n      Manufacturer information illustrating the distinction between breaker-based Class CB and switch-disconnector-based Class PC architectures.\r\n      <a href=\"https:\/\/www.se.com\/sg\/en\/product-subcategory\/4260-source-changeover-switches\/\" target=\"_blank\" rel=\"noopener noreferrer\">Schneider Electric source changeover range<\/a>.\r\n    <\/li>\r\n\r\n    <li id=\"ref-6\">\r\n      <strong>Schneider Electric \/ ASCO Power Technologies.<\/strong>\r\n      <em>ATS Transition Modes<\/em>.\r\n      Technical explanation of open, delayed and closed transition operation.\r\n      <a href=\"https:\/\/www.se.com\/sg\/en\/faqs\/FAQ000219583\/\" target=\"_blank\" rel=\"noopener noreferrer\">Schneider Electric technical FAQ<\/a>.\r\n    <\/li>\r\n\r\n    <li id=\"ref-7\">\r\n      <strong>Schneider Electric \/ ASCO Power Technologies.<\/strong>\r\n      <em>Neutral Configurations in Transfer Switches<\/em>,\r\n      Document ASC-DB-NCTS, Version 1.0.\r\n      <a href=\"https:\/\/www.se.com\/us\/en\/download\/document\/ASC-DB-NCTS\/\" target=\"_blank\" rel=\"noopener noreferrer\">Official Schneider Electric document page<\/a>.\r\n    <\/li>\r\n  <\/ol>\r\n\r\n  <p class=\"ly-final-note\"><strong>Project boundary:<\/strong> This page is an engineering and procurement guide for applying a compact ATS within a suitable MDB or essential distribution section. Final model selection, short-circuit coordination, pole configuration, neutral switching, generator interface, enclosure integration and compliance must be confirmed from the actual single-line diagram, current LEEYEE model data, applicable standards and local project requirements.<\/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(\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>\r\n\r\n<\/div>\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>An automatic transfer switch in a main distribution board should be selected as part of the complete power-distribution design, not as an isolated switch. For panel builders, electrical contractors, generator integrators and project buyers, the key questions are where the transfer point is located, which loads actually require standby power, what current the ATS must&#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-31234","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 for MDB | Compact ATS Selection Guide<\/title>\n<meta name=\"description\" content=\"Learn how to select a compact automatic transfer switch for an MDB by transferred load, current, short-circuit conditions, 3P\/4P neutral, generator data and IEC requirements.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.cnspd.com\/id\/automatic-transfer-switch-main-distribution-board\/\" \/>\n<meta property=\"og:locale\" content=\"id_ID\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Automatic Transfer Switch for MDB | Compact ATS Selection Guide\" \/>\n<meta property=\"og:description\" content=\"Learn how to select a compact automatic transfer switch for an MDB by transferred load, current, short-circuit conditions, 3P\/4P neutral, generator data and IEC requirements.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.cnspd.com\/id\/automatic-transfer-switch-main-distribution-board\/\" \/>\n<meta property=\"og:site_name\" content=\"Surge Protector, Surge Arrestor, Isolating Switch - 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