{"id":17409,"date":"2026-11-02T13:39:16","date_gmt":"2026-11-02T12:39:16","guid":{"rendered":"https:\/\/ventsystems.de\/24-v-netzteil-fensterantrieb-berechnen\/"},"modified":"2026-11-08T14:56:29","modified_gmt":"2026-11-08T13:56:29","slug":"calculate-24v-power-supply-window-actuators","status":"publish","type":"page","link":"https:\/\/ventsystems.de\/en\/24-v-netzteil-fensterantrieb-berechnen\/","title":{"rendered":"Calculating a 24 V power supply for window actuators"},"content":{"rendered":"<p class=\"vs-kurzantwort wp-block-paragraph\"><strong>In short:<\/strong> Add up the current draw of all 24 V actuators that run at the same time and add about 20 % reserve. The result is the minimum current of the power supply in amps. The VS-C24-7A control unit delivers up to 7 A and replaces a separate power supply in ventilation systems.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">The formula<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Power supply current = total current draw of all actuators running simultaneously \u00d7 1.2<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">You get the power in watts by multiplying the current by 24 V. The current draw is on the rating plate or in the actuator's datasheet \u2013 for Vent Systems in the downloads area of the product page.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Worked example<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A stairwell has four fanlights. According to the datasheet each actuator draws 1.0 A (example value). All four run together.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table><thead><tr><th>Step<\/th><th>Invoice<\/th><th>Result<\/th><\/tr><\/thead><tbody><tr><td>Total current draw<\/td><td>4 \u00d7 1.0 A<\/td><td>4.0 A<\/td><\/tr><tr><td>20 % reserve<\/td><td>4.0 A \u00d7 1.2<\/td><td>4.8 A<\/td><\/tr><tr><td>Performance<\/td><td>4.8 A \u00d7 24 V<\/td><td>approx. 115 W<\/td><\/tr><tr><td>Fits the VS-C24-7A?<\/td><td>4.8 A &lt; 7 A<\/td><td>Yes<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">If the actuators don't run at the same time, only the group that runs together counts. On the VS-C24-7A all connected actuators run together \u2013 for separate groups use one control unit per group.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Power supply or control unit?<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Pure power supply:<\/strong> provides 24 V only. To open and close you also need switches with polarity reversal or a control unit.<\/li>\n\n<li><strong>VS-C24-7A control unit:<\/strong> converts 230 V to 24 V (max. 7 A) and drives the actuators open and closed by switch or radio. Rain and wind sensors can be connected. \u20ac60 net, in stock in Hamburg.<\/li>\n\n<li><strong>SHEV systems:<\/strong> Here the approved smoke vent control panel powers the actuators. The VS-C24-7A is not a smoke vent control panel.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Don't forget the cable cross-section<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">At 24 V, noticeable voltage is lost over long cables. If too little reaches the actuator, it runs slower or stops. Estimate the voltage drop on a copper cable like this:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>\u0394U = 2 \u00d7 cable length (m) \u00d7 current (A) \u00f7 (56 \u00d7 cross-section in mm\u00b2)<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Example: 20 m cable, 3 A, 1.5 mm\u00b2 gives about 1.4 V \u2013 just under 6 % of 24 V. With 2.5 mm\u00b2 it is only about 0.9 V. The permissible voltage drop is in the actuator's datasheet; if in doubt, choose the larger cross-section.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">What to look out for<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Only add up the actuators that really run at the same time.<\/li>\n\n<li>Inrush currents and ageing are reasons for the reserve \u2013 don't calculate too tightly.<\/li>\n\n<li>Mount the power supply or control unit dry and well ventilated.<\/li>\n\n<li>Never mix up 24 V and 230 V actuators: a 24 V actuator must not be connected to 230 V.<\/li>\n\n<li>The 230 V connection must be made by a qualified electrician.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Read more:<\/strong> <a href=\"\/en\/laying-cables-window-drive\/\">Laying cables for window drives: cross-section, length and connection<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Frequently asked questions<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">How many actuators can the VS-C24-7A handle?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Up to 7 actuators, depending on current draw. The total of all actuators must stay below 7 A.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Is a power supply with exactly the calculated total enough?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Better not. Plan for about 20 % reserve so the power supply delivers enough current reliably at start-up and after years of operation.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Where do I find my actuator's current draw?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">On the rating plate or in the datasheet. For Vent Systems actuators it is in the downloads area of the product page.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Learn more: <a href=\"\/en\/dictionary\/24-v-power-supply\/\">24 V power supply in the glossary<\/a> \u00b7 <a href=\"\/en\/dictionary\/current-consumption\/\">Current consumption<\/a> \u00b7 <a href=\"\/en\/dictionary\/spannungsfall\/\">Voltage drop<\/a> \u00b7 <a href=\"\/en\/dictionary\/cable-cross-section\/\">Cable cross-section<\/a> \u00b7 <a href=\"\/en\/ventilation-control-window-drives\/\">Planning a ventilation control<\/a> \u00b7 <a href=\"\/en\/product-category\/controls\/\">Controls in the shop<\/a>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">See also in the glossary: <a href=\"\/en\/dictionary\/polarity-reversal\/\">Polarity reversal<\/a> \u00b7 <a href=\"\/en\/dictionary\/safety-extra-low-voltage\/\">Safety extra-low voltage (SELV)<\/a><\/p>","protected":false},"excerpt":{"rendered":"<p>Kurz gesagt: Addieren Sie die Stromaufnahme aller 24-V-Antriebe, die gleichzeitig fahren, und rechnen Sie etwa 20 % Reserve dazu. Das Ergebnis ist der Mindeststrom des Netzteils in Ampere. Die Steuerung VS-C24-7A liefert bis zu 7 A und ersetzt bei L\u00fcftungsanlagen ein separates Netzteil. Die Formel Netzteilstrom = Summe der Stromaufnahme aller gleichzeitig fahrenden Antriebe \u00d7 [&hellip;]<\/p>\n","protected":false},"author":9,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"class_list":["post-17409","page","type-page","status-publish","hentry"],"acf":[],"_links":{"self":[{"href":"https:\/\/ventsystems.de\/en\/wp-json\/wp\/v2\/pages\/17409","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ventsystems.de\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/ventsystems.de\/en\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/ventsystems.de\/en\/wp-json\/wp\/v2\/users\/9"}],"replies":[{"embeddable":true,"href":"https:\/\/ventsystems.de\/en\/wp-json\/wp\/v2\/comments?post=17409"}],"version-history":[{"count":2,"href":"https:\/\/ventsystems.de\/en\/wp-json\/wp\/v2\/pages\/17409\/revisions"}],"predecessor-version":[{"id":17867,"href":"https:\/\/ventsystems.de\/en\/wp-json\/wp\/v2\/pages\/17409\/revisions\/17867"}],"wp:attachment":[{"href":"https:\/\/ventsystems.de\/en\/wp-json\/wp\/v2\/media?parent=17409"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}