{"id":19305,"date":"2026-10-17T11:16:14","date_gmt":"2026-10-17T03:16:14","guid":{"rendered":"https:\/\/www.wehopower.com\/news\/safety-extra-low-voltage-and-selv-output-requirements\/"},"modified":"2026-10-19T12:09:28","modified_gmt":"2026-10-19T04:09:28","slug":"safety-extra-low-voltage-and-selv-output-requirements","status":"publish","type":"news","link":"https:\/\/www.wehopower.com\/tl\/news\/safety-extra-low-voltage-and-selv-output-requirements\/","title":{"rendered":"Safety Extra Low Voltage and SELV Output Requirements for OEM Buyers"},"content":{"rendered":"<article>\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_86 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Talaan ng mga Nilalaman<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">I-toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewbox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewbox=\"0 0 24 24\" version=\"1.2\" baseprofile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1' ><li class='ez-toc-page-1 ez-toc-heading-level-1'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.wehopower.com\/tl\/news\/safety-extra-low-voltage-and-selv-output-requirements\/#Safety_Extra_Low_Voltage_and_SELV_Output_Requirements_for_OEM_Buyers\" >Safety Extra Low Voltage and SELV Output Requirements for OEM Buyers<\/a><ul class='ez-toc-list-level-2' ><li class='ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.wehopower.com\/tl\/news\/safety-extra-low-voltage-and-selv-output-requirements\/#Separate_the_voltage_rating_from_the_protection_concept\" >Separate the voltage rating from the protection concept<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.wehopower.com\/tl\/news\/safety-extra-low-voltage-and-selv-output-requirements\/#Read_the_receiving_equipments_requirements\" >Read the receiving equipment\u2019s requirements<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.wehopower.com\/tl\/news\/safety-extra-low-voltage-and-selv-output-requirements\/#What_the_NDR-75-24_evidence_does_and_does_not_show\" >What the NDR-75-24 evidence does and does not show<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.wehopower.com\/tl\/news\/safety-extra-low-voltage-and-selv-output-requirements\/#Put_safety_evidence_into_the_purchase_specification\" >Put safety evidence into the purchase specification<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.wehopower.com\/tl\/news\/safety-extra-low-voltage-and-selv-output-requirements\/#Do_not_solve_an_evidence_gap_by_changing_the_earth_connection\" >Do not solve an evidence gap by changing the earth connection<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.wehopower.com\/tl\/news\/safety-extra-low-voltage-and-selv-output-requirements\/#Prepare_a_useful_enquiry\" >Prepare a useful enquiry<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/www.wehopower.com\/tl\/news\/safety-extra-low-voltage-and-selv-output-requirements\/#Buyer_FAQ\" >Buyer FAQ<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/www.wehopower.com\/tl\/news\/safety-extra-low-voltage-and-selv-output-requirements\/#Is_every_24_V_supply_SELV\" >Is every 24 V supply SELV?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/www.wehopower.com\/tl\/news\/safety-extra-low-voltage-and-selv-output-requirements\/#Does_the_presence_of_an_earth_terminal_rule_out_a_separated_output\" >Does the presence of an earth terminal rule out a separated output?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/www.wehopower.com\/tl\/news\/safety-extra-low-voltage-and-selv-output-requirements\/#Can_the_same_accepted_supply_be_connected_to_a_new_external_device_without_review\" >Can the same accepted supply be connected to a new external device without review?<\/a><\/li><\/ul><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n<h1><span class=\"ez-toc-section\" id=\"Safety_Extra_Low_Voltage_and_SELV_Output_Requirements_for_OEM_Buyers\"><\/span>Safety Extra Low Voltage and SELV Output Requirements for OEM Buyers<span class=\"ez-toc-section-end\"><\/span><\/h1>\n<figure data-image-role=\"application_a\"><img fetchpriority=\"high\" decoding=\"async\" src=\"https:\/\/i1.wp.com\/www.wehopower.com\/wp-content\/uploads\/2026\/10\/01-application-a-98.png?quality=85&#038;strip=all\" alt=\"Safety Extra Low Voltage and SELV Output Requirements for OEM Buyers  title=\" width=\"1536\" height=\"1024\" safety extra low voltage and selv output requirements for oem buyers title=\"\"><figcaption>Conceptual 24 V auxiliary control arrangement. The mounting and wiring illustration does not establish a SELV assessment.<\/figcaption><\/figure>\n<p>A 24 V output does not automatically qualify as SELV. For an OEM purchase, specify the required protection concept, the exact safety evidence for the power supply and the conditions under which the complete circuit will be used. The normal output voltage is only one part of that assessment.<\/p>\n<p>The pictured NDR-75-24 is marked 24 V, 3.2 A and has a protective-earth input terminal. Those visible facts support component identification, not a conclusion that every circuit connected to it is SELV. This article is a procurement framework; the equipment\u2019s electrical safety design and verification remain the responsibility of appropriately qualified personnel.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Separate_the_voltage_rating_from_the_protection_concept\"><\/span>Separate the voltage rating from the protection concept<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/23997\" target=\"_blank\" rel=\"noopener\">IEC 61140<\/a> provides common principles for protection against electric shock across installations, systems and equipment. An applicable product or installation standard determines how those principles are implemented in the project. The market, equipment type and operating environment therefore belong in the specification before a supplier is asked for \u201ca safe 24 V supply.\u201d<\/p>\n<p>The <a href=\"https:\/\/www.se.com\/in\/en\/faqs\/FA253330\/\" target=\"_blank\" rel=\"noopener\">referenced SELV explanation<\/a> distinguishes the low voltage from protective separation and behavior under relevant fault conditions. PELV is a related protection concept with different earthing provisions. These terms should not be used interchangeably, and a simple voltage reading cannot establish the required separation.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Read_the_receiving_equipments_requirements\"><\/span>Read the receiving equipment\u2019s requirements<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Some receivers specify SELV or PELV explicitly. Collect the selected receiver&#8217;s external-supply and earthing requirements before evaluating a WEHO candidate. An example from a different device&#8217;s manual does not establish compatibility with the WEHO sample.<\/p>\n<p>Create an interface list for the actual project: supply, controller, field devices, communication ports, external connectors and any earth-referenced equipment. Determine whether an external connection changes the protection arrangement. Keep functional grounding, protective earth and the DC return distinct in the design records; do not assume that all three are interchangeable.<\/p>\n<figure data-image-role=\"product_detail\"><img decoding=\"async\" src=\"https:\/\/i1.wp.com\/www.wehopower.com\/wp-content\/uploads\/2026\/10\/03-product-detail-95.png?quality=85&#038;strip=all\" alt=\"Safety Extra Low Voltage and SELV Output Requirements for OEM Buyers  title=\" width=\"1536\" height=\"1024\" safety extra low voltage and selv output requirements for oem buyers title=\"\"><figcaption>The original sample identifies its rating and physical interface. A SELV claim needs the applicable safety evidence and circuit arrangement.<\/figcaption><\/figure>\n<h2><span class=\"ez-toc-section\" id=\"What_the_NDR-75-24_evidence_does_and_does_not_show\"><\/span>What the NDR-75-24 evidence does and does not show<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>The original sample has four upper DC terminals marked \u2212V, \u2212V, +V, +V and three lower input terminals marked earth, N and L. Its matching drawing gives a 32 \u00d7 125.2 \u00d7 102 mm envelope and a rear DIN-rail mounting arrangement. These details are useful for the bill of materials and panel layout.<\/p>\n<p>The <a href=\"https:\/\/www.wehopower.com\/tl\/product\/ndr-dinrail-75w-ac-to-dc-single-output-switching-power-supply\/\">NDR-75 product information<\/a> provides electrical and installation data. However, a CE mark, nominal 24 V rating or a withstand-voltage row is not a substitute for an exact-model safety assessment. The materials used for this article do not establish a specific SELV qualification for the photographed revision. Request the relevant report or certificate scope and conditions before treating it as such.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Put_safety_evidence_into_the_purchase_specification\"><\/span>Put safety evidence into the purchase specification<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<table>\n<thead>\n<tr>\n<th>RFQ requirement<\/th>\n<th>What to obtain<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Protection concept<\/td>\n<td>State SELV, PELV or the requirement specified by the applicable equipment standard.<\/td>\n<\/tr>\n<tr>\n<td>Source identity<\/td>\n<td>Full model, hardware revision, label and the exact documents covering the offered unit.<\/td>\n<\/tr>\n<tr>\n<td>Assessment scope<\/td>\n<td>Applicable standard and edition, report identity, tested configuration and limitations.<\/td>\n<\/tr>\n<tr>\n<td>Installation conditions<\/td>\n<td>Required earthing, spacing, enclosure, wiring and environmental conditions.<\/td>\n<\/tr>\n<tr>\n<td>System acceptance<\/td>\n<td>Verification plan covering the assembled equipment and all external interfaces.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Agree how the supplier will notify you of changes affecting the approved construction or document coverage. For a second source, repeat the interface and evidence review rather than carrying over approval because the replacement also says 24 V. Retain the accepted sample identification and revision in the production documentation.<\/p>\n<figure data-image-role=\"application_b\"><img decoding=\"async\" src=\"https:\/\/i1.wp.com\/www.wehopower.com\/wp-content\/uploads\/2026\/10\/02-application-b-96.png?quality=85&#038;strip=all\" alt=\"Safety Extra Low Voltage and SELV Output Requirements for OEM Buyers  title=\" width=\"1536\" height=\"1024\" safety extra low voltage and selv output requirements for oem buyers title=\"\"><figcaption>An isolated mechanical-fit layout with all supply terminals empty; no working connection or SELV assessment is implied.<\/figcaption><\/figure>\n<h2><span class=\"ez-toc-section\" id=\"Do_not_solve_an_evidence_gap_by_changing_the_earth_connection\"><\/span>Do not solve an evidence gap by changing the earth connection<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Never remove a required protective-earth connection to make a circuit appear floating. The metal enclosure\u2019s protective arrangement and the output circuit\u2019s earthing rules are separate design questions. Similarly, an output fuse can help address a circuit\u2019s overcurrent risk, but it does not create protective separation from the mains.<\/p>\n<p>The final equipment assessment should use the actual enclosure, wiring and connected loads. Any tests involving hazardous voltages or simulated faults require the appropriate qualified facility and procedures; they are not a field workaround for missing product documentation.<\/p>\n<figure data-image-role=\"engineering_context\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/i1.wp.com\/www.wehopower.com\/wp-content\/uploads\/2026\/10\/04-engineering-context-99.png?quality=85&#038;strip=all\" alt=\"Safety Extra Low Voltage and SELV Output Requirements for OEM Buyers  title=\" width=\"1536\" height=\"1024\" safety extra low voltage and selv output requirements for oem buyers title=\"\"><figcaption>The equipment designer must reconcile the source, receiver and external connections under the applicable safety standard.<\/figcaption><\/figure>\n<h2><span class=\"ez-toc-section\" id=\"Prepare_a_useful_enquiry\"><\/span>Prepare a useful enquiry<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><a href=\"https:\/\/www.wehopower.com\/tl\/contact\/\">Ask WEHO about the offered revision<\/a> with the required output and load profile, input conditions, receiver safety requirements, destination market, environment and panel layout. Include sample quantity, forecast production volume and the specific evidence needed for your technical file. Request commercial terms separately from the safety assessment.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Buyer_FAQ\"><\/span>Buyer FAQ<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><span class=\"ez-toc-section\" id=\"Is_every_24_V_supply_SELV\"><\/span>Is every 24 V supply SELV?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>No. The voltage rating alone does not establish protective separation or the required behavior in fault conditions.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Does_the_presence_of_an_earth_terminal_rule_out_a_separated_output\"><\/span>Does the presence of an earth terminal rule out a separated output?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>No. Chassis protective earth and output-circuit configuration are different matters. Use the exact safety documentation and the equipment\u2019s applicable requirements; do not infer the answer from one terminal.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Can_the_same_accepted_supply_be_connected_to_a_new_external_device_without_review\"><\/span>Can the same accepted supply be connected to a new external device without review?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Not automatically. A new interface can change grounding, separation or fault paths. Review the connection as part of the complete circuit before releasing the change.<\/p>\n<\/article>","protected":false},"excerpt":{"rendered":"<p>SELV is a protection concept for the circuit and its source, not another name for 24 V. Keep voltage ratings, protective separation and equipment wiring distinct.<\/p>","protected":false},"author":2,"featured_media":19301,"parent":0,"menu_order":35,"comment_status":"closed","ping_status":"","template":"","format":"standard","meta":{"_acf_changed":false,"_joinchat":[],"footnotes":""},"news_category":[149,284],"class_list":["post-19305","news","type-news","status-publish","format-standard","has-post-thumbnail","hentry","news_category-blog","news_category-product-articles","entry"],"acf":[],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/www.wehopower.com\/tl\/wp-json\/wp\/v2\/news\/19305","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.wehopower.com\/tl\/wp-json\/wp\/v2\/news"}],"about":[{"href":"https:\/\/www.wehopower.com\/tl\/wp-json\/wp\/v2\/types\/news"}],"author":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/tl\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/tl\/wp-json\/wp\/v2\/comments?post=19305"}],"version-history":[{"count":1,"href":"https:\/\/www.wehopower.com\/tl\/wp-json\/wp\/v2\/news\/19305\/revisions"}],"predecessor-version":[{"id":19632,"href":"https:\/\/www.wehopower.com\/tl\/wp-json\/wp\/v2\/news\/19305\/revisions\/19632"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/tl\/wp-json\/wp\/v2\/media\/19301"}],"wp:attachment":[{"href":"https:\/\/www.wehopower.com\/tl\/wp-json\/wp\/v2\/media?parent=19305"}],"wp:term":[{"taxonomy":"news_category","embeddable":true,"href":"https:\/\/www.wehopower.com\/tl\/wp-json\/wp\/v2\/news_category?post=19305"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}