{"id":24710,"date":"2026-11-12T21:51:34","date_gmt":"2026-11-12T18:51:34","guid":{"rendered":"https:\/\/azeidkgroup.com\/sa\/media-center\/"},"modified":"2026-11-12T21:52:42","modified_gmt":"2026-11-12T18:52:42","slug":"fire-alarm-wiring-diagram","status":"publish","type":"post","link":"https:\/\/azeidkgroup.com\/en\/sa\/media-center\/fire-alarm-wiring-diagram\/","title":{"rendered":"Fire Alarm Wiring Diagram: Detector Bases, EOL Resistors, Zones and Riser"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"24710\" class=\"elementor elementor-24710 elementor-24709 elementor-bc-flex-widget\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-116d4f2 e-con-full az-el-article e-flex e-con e-parent\" data-id=\"116d4f2\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-0238f1a elementor-widget elementor-widget-text-editor\" data-id=\"0238f1a\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p class=\"az-intro\">A <strong>fire alarm wiring diagram<\/strong> shows how the zone circuits and sounder circuits leave the control panel, how the cable runs from one detector base to the next until the last device, where the end-of-line (EOL) device sits, and how those circuits are spread over the floors on the riser diagram. Values change from panel to panel and come from the datasheet.<\/p>\n<p>This guide uses the official datasheets for the Context Plus panels and detectors that AZEIDK supplies as part of its <a href=\"\/en\/sa\/solutions\/fire-alarm-systems\/\">fire alarm systems<\/a>, plus NFPA 72 pathway classes.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-bb2e27f elementor-widget elementor-widget-text-editor\" data-id=\"bb2e27f\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<div class=\"az-keybox\"><h2>Key takeaways<\/h2><ul><li>A conventional detector plugs into a base, and the base is the wiring point. Context Plus Series 65E detectors use a two-wire, polarity-insensitive supply per the datasheet.<\/li><li>The cable goes into each base and out to the next one. The EOL device goes at the last device, never inside the panel.<\/li><li>EOL and call point resistor values differ between panels: for example, 6,800 ohm on the sounder circuits of the CFP and MFP panels, and a dedicated EOL unit on each zone.<\/li><li>A Class B circuit stops working beyond the first open; a Class A circuit has a return path and keeps working after a single open.<\/li><li>The riser diagram summarises floors, zones, device counts, cable type and repeater panels, and is checked before installation.<\/li><\/ul><\/div>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-5bee80a elementor-widget elementor-widget-text-editor\" data-id=\"5bee80a\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>What does a fire alarm wiring diagram show?<\/h2>\n<p>On Saudi projects the consultant usually asks for two drawings: the wiring diagram, which shows each device&#8217;s terminals and how it connects, and the riser diagram, which shows how the system is distributed vertically through the building. A good diagram shows:<\/p>\n<ul><li>Where the control panel is, and how many zones are used and kept spare.<\/li><li>The route of each zone and the devices on it: smoke detectors, heat detectors and manual call points (break glass units).<\/li><li>Sounder circuits kept separate from detection circuits, with the EOL position for each circuit.<\/li><li>Cable type and size, and auxiliary outputs such as fire and fault relays.<\/li><\/ul>\n<p>The Saudi Fire Code, SBC 801, sets out in Chapter 9 when a fire alarm and detection system is required. The circuit details themselves come from the reference standard adopted for the project, such as NFPA 72, and from the panel manufacturer&#8217;s instructions.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-aec3da6 elementor-widget elementor-widget-text-editor\" data-id=\"aec3da6\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>How is a smoke detector wired to its base in a conventional system?<\/h2>\n<p>A conventional detector is never wired directly. The base is fixed to the ceiling and the cables are terminated on it, then the detector head twists onto the base. Context Plus states that Series 65A and 65E bases accept the detector without force, are lockable and contain no electronic parts that could be damaged during installation.<\/p>\n<h3>Standard base and relay base<\/h3>\n<p>The <a href=\"\/en\/sa\/products\/series-65a-and-series-65e-conventional-detector-bases-45681-200imc-and-45681-245\/\">Context Plus conventional detector bases<\/a> come as the 45681-200IMC standard base and the 45681-245 relay base, used where an extra switching function is needed on alarm.<\/p>\n<h3>Two wires, no polarity, and the remote indicator terminal<\/h3>\n<p>According to the datasheet, Series 65E smoke detectors (optical 55000-316IMC and ionisation 55000-216IMC) operate from 9 to 33 V DC on a two-wire, polarity-insensitive supply, and draw 52 mA in alarm at 24 V DC. An R- terminal drives a remote LED indicator (BF318) for detectors hidden in ceiling voids or locked rooms; the catalogue notes that a current-limiting series resistor may be needed for the remote indicator.<\/p>\n<p>Terminal numbering varies by model, so follow the installation sheet supplied with the base.<\/p>\n<h3>Daisy chain, not branches<\/h3>\n<p>The zone cable enters the first base and leaves to the second, and so on until the last device. As Wayne D. Moore explains in Electrical Contractor (February 2017, based on NFPA 72-2016), T-tapping a conventional circuit compromises its monitoring: a branch off the main run can break without the panel ever seeing it.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-ab995d6 elementor-widget elementor-widget-text-editor\" data-id=\"ab995d6\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>End-of-line resistor (EOL): what value, and why does it change?<\/h2>\n<p>A conventional panel monitors each zone with a small current that flows to the end of the line. A break drops the current and shows a fault; an alarm raises it and shows a fire. So the EOL must sit at the real last device and must be the value the panel manufacturer specifies. From the official Context Plus datasheets:<\/p>\n<div class=\"az-table-wrap\"><table><thead><tr><th>Item<\/th><th>CFP panel (2 to 8 zones)<\/th><th>MFP panel (16 to 28 zones)<\/th><\/tr><\/thead><tbody><tr><td>Zone end of line<\/td><td>EOL monitoring module supplied, one per zone<\/td><td>Miniature circuit board supplied, one per zone (BF-EOL)<\/td><\/tr><tr><td>Manual call point resistor<\/td><td>470 to 680 ohm<\/td><td>470 to 680 ohm, 0.5 W<\/td><\/tr><tr><td>Sounder circuit EOL<\/td><td>6,800 ohm, 5% tolerance, 0.25 W<\/td><td>6,800 ohm, 5% tolerance, 0.25 W<\/td><\/tr><tr><td>Devices per zone<\/td><td>25 detectors; 32 detectors and call points combined<\/td><td>20 smoke detectors; no limit on call points<\/td><\/tr><tr><td>Sounder circuits<\/td><td>4<\/td><td>4<\/td><\/tr><tr><td>Cable<\/td><td>Fire-resistant screened, minimum 1 mm\u00b2, up to 500 m per circuit, max 20 ohm per conductor<\/td><td>Per the installation manual<\/td><\/tr><\/tbody><\/table><\/div>\n<p>The MFP panel also uses detector continuity diodes (silicon 1N4001 or Schottky) for head-removal monitoring. For the FP 1 to 14 zone panels, the catalogue lists head-removal monitoring as an option and a &#8220;short circuit equals fire&#8221; setting, selectable zone by zone, intended for older installations with no resistors in the call points. The catalogue does not give the FP zone EOL value, so take it from that panel&#8217;s installation manual.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-fbc597c elementor-widget elementor-widget-text-editor\" data-id=\"fbc597c\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>How are zones divided and sounder circuits drawn?<\/h2>\n<p>In a conventional system a zone is one circuit and gives the panel one message: &#8220;fire in zone X&#8221;. Zones normally follow floors or parts of floors per the approved design.<\/p>\n<p>The <a href=\"\/en\/sa\/products\/fp-1-14-zone-conventional-fire-alarm-panels\/\">Context Plus FP conventional panels<\/a> come as non-expandable 1, 2, 4 and 8 zone units, a 4 zone panel expandable to 6, and an 8 zone panel expandable to 14, each with two sounder circuits. The CFP and MFP panels each have four sounder circuits.<\/p>\n<p>Sounder circuits are fully separate from detection circuits and are monitored by reverse voltage, which is why the CFP datasheet requires electronic sounders to be polarised. On the CFP, sounder current is limited to 200 mA per circuit and 800 mA across all circuits.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-c4bc7bc elementor-widget elementor-widget-text-editor\" data-id=\"c4bc7bc\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>Class A vs Class B on the wiring diagram<\/h2>\n<p>Since the 2010 edition, NFPA 72 has had a dedicated chapter on circuits and pathways (Chapter 12) and classifies them by Class instead of the old Style system, as Wayne D. Moore explains in Electrical Contractor (April 2011):<\/p>\n<ul><li><strong>Class B:<\/strong> a single path with no return. The first open stops every device beyond it, and the panel signals a fault.<\/li><li><strong>Class A:<\/strong> the cable returns from the last device to the panel, so devices keep working after a single open.<\/li><li><strong>Class X:<\/strong> a redundant path that keeps working after a single open or a single short; common on addressable signalling line circuits.<\/li><\/ul>\n<p>For Class A, the outgoing and return conductors must be routed separately, with limited exceptions in Chapter 12, including up to 10 feet where the cables enter or leave the control unit enclosure, as City of San Diego Technical Bulletin FIRE-9-4 (June 2020) summarises. Before drawing Class A, confirm in the installation manual that the panel supports it: the datasheets above describe zones terminated with an EOL device.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-a015a49 elementor-widget elementor-widget-text-editor\" data-id=\"a015a49\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>Fire alarm riser diagram: what goes on it?<\/h2>\n<p>A riser diagram is a vertical schematic of the building. Each floor is a horizontal line with its devices. It normally shows:<\/p>\n<ol><li>The main panel and repeater panels. The FP range has the FF396-2 ten-zone and FF398-2 twenty-zone repeaters; the CFP connects up to eight two-wire repeaters through a CFP761 card; the MFP connects up to eight repeaters through an FF596T transmitter.<\/li><li>Each zone number, its name and the floor it covers.<\/li><li>Device counts per floor by type: smoke detectors, heat detectors, call points and sounders.<\/li><li>Cable type and size for each circuit.<\/li><li>Outputs to other systems, such as the CFP fire and fault relays (voltage-free, 1 A at 30 V DC maximum), used for interfaces such as AHU shutdown.<\/li><\/ol>\n<p>The MFP datasheet warns against powering door release from the panel, as it cuts battery standby time. Addressable risers follow different logic, covered in our article on <a href=\"\/en\/sa\/media-center\/addressable-fire-alarm-loop-design\/\">addressable fire alarm loop design<\/a>, and the choice between the two is covered in <a href=\"\/en\/sa\/media-center\/fire-alarm-systems-saudi-arabia\/\">conventional vs addressable fire alarm systems<\/a>. AZEIDK&#8217;s <a href=\"\/en\/sa\/services\/shop-drawings-coordination\/\">shop drawings and coordination<\/a> team prepares wiring and riser diagrams to the project&#8217;s approved design.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-4fc0584 elementor-widget elementor-widget-text-editor\" data-id=\"4fc0584\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>Common fire alarm wiring mistakes<\/h2>\n<ul><li><strong>EOL fitted inside the panel:<\/strong> the circuit looks healthy while part of it can be broken without the panel noticing.<\/li><li><strong>T-tapped zones:<\/strong> the branch is not monitored.<\/li><li><strong>EOL value taken from another panel:<\/strong> a permanent fault, or a break the panel cannot detect.<\/li><li><strong>Non-polarised sounders on a reverse-voltage monitored circuit<\/strong>, or sounders wired onto a detection zone.<\/li><li><strong>Cable that does not match the datasheet:<\/strong> smaller cross-section, or non-fire-resistant cable where the manufacturer calls for it.<\/li><li><strong>Riser diagram that does not match site:<\/strong> handover stalls.<\/li><\/ul>\n<p><strong>Safety note:<\/strong> this article is technical guidance only. Wiring and testing must be carried out by qualified technicians to the project&#8217;s approved design and the manufacturer&#8217;s installation manual, with mains and batteries isolated.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-3f69e0d elementor-widget elementor-widget-text-editor\" data-id=\"3f69e0d\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>Frequently asked questions<\/h2>\n<div class=\"az-faq\"><details class=\"az-faq__item\"><summary><h3>How do you wire a conventional fire alarm circuit?<\/h3><\/summary><p>The zone cable leaves the panel and runs in and out of each detector base and call point in turn, up to the last device, where the EOL device specified by the panel manufacturer is fitted. Sounders go on a separate circuit with their own EOL.<\/p><\/details><details class=\"az-faq__item\"><summary><h3>What is the end of line resistor value in a fire alarm system?<\/h3><\/summary><p>There is no single value. For example, the CFP and MFP datasheets specify 6,800 ohm on sounder circuits and a dedicated EOL unit on each zone. Always check your panel&#8217;s manual.<\/p><\/details><details class=\"az-faq__item\"><summary><h3>Does a 2 wire smoke detector have polarity?<\/h3><\/summary><p>It depends on the model. Context Plus Series 65E detectors are polarity-insensitive per the datasheet, while electronic sounders on a CFP panel must be polarised.<\/p><\/details><details class=\"az-faq__item\"><summary><h3>What is the difference between Class A and Class B?<\/h3><\/summary><p>Class B is a single path that stops beyond the first open. Class A returns to the panel and keeps devices working after a single open. Both signal a fault, per NFPA 72.<\/p><\/details><details class=\"az-faq__item\"><summary><h3>How many detectors can go on one zone?<\/h3><\/summary><p>It depends on the panel: 25 detectors and 32 devices in total on the CFP, 20 smoke detectors on the MFP.<\/p><\/details><details class=\"az-faq__item\"><summary><h3>Can I fit another brand&#8217;s detector on a Context Plus panel?<\/h3><\/summary><p>Context Plus states compatibility with its Series 65A, Series 65E and ActiV detectors. Any other detector needs compatibility confirmed by the manufacturer before installation.<\/p><\/details><\/div>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-b3e99fa elementor-widget elementor-widget-text-editor\" data-id=\"b3e99fa\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>Conclusion<\/h2>\n<p>Reading a fire alarm wiring diagram starts at the panel: how many zones, how many sounder circuits, and what EOL value the manufacturer specifies. Then follow the cable from base to base to the last device, and check the riser diagram against site for floors, zones and device counts. Checking these points on the drawing before cable pulling catches wiring errors before handover.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-2ab063c elementor-widget elementor-widget-text-editor\" data-id=\"2ab063c\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p class=\"az-cta\"><strong>Need a wiring or riser diagram for a conventional system?<\/strong> Send us the architectural drawings, number of floors and required zones, and we will propose the right panel and detectors with datasheets. <a href=\"\/en\/sa\/contact\/\">Talk to the AZEIDK team<\/a><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-40e3067 elementor-widget elementor-widget-text-editor\" data-id=\"40e3067\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<div class=\"az-source\"><strong>References:<\/strong> <a href=\"https:\/\/www.ecmag.com\/section\/systems\/fire-alarm-circuits-redfined\" rel=\"noopener\" target=\"_blank\">Fire Alarm Circuits Redefined<\/a> (Wayne D. Moore, Electrical Contractor, April 2011), <a href=\"https:\/\/www.ecmag.com\/magazine\/articles\/article-detail\/systems-cabling-mysteries-and-myths\" rel=\"noopener\" target=\"_blank\">Cabling Mysteries and Myths<\/a> (Wayne D. Moore, Electrical Contractor, February 2017), <a href=\"https:\/\/www.contextplus.co.uk\/\" rel=\"noopener\" target=\"_blank\">Context Plus official website<\/a>, Context Plus CFP 2 to 8 zone conventional panels datasheet (PDF), Context Plus MFP 16 to 28 zone conventional panel datasheet (PDF), Context Plus Conventional Fire Equipment Catalogue: FP panels, Series 65A and 65E detectors and bases (PDF), and City of San Diego Development Services Technical Bulletin FIRE-9-4 (June 2020, PDF).<\/div>\t\t\t\t\t\t\t\t<\/div>\n\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>Fire alarm wiring diagram explained: detector-to-base wiring, end of line resistor values, zones, Class A vs Class B and the riser diagram for Saudi projects.<\/p>\n","protected":false},"author":0,"featured_media":24701,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[221,321,323,322],"tags":[],"azeidk_region":[223],"class_list":["post-24710","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-azeidk-articles","category-codes-certifications-en","category-systems-guides-en","category-systems-guides-ar"],"acf":[],"_links":{"self":[{"href":"https:\/\/azeidkgroup.com\/en\/wp-json\/wp\/v2\/posts\/24710","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/azeidkgroup.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/azeidkgroup.com\/en\/wp-json\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/azeidkgroup.com\/en\/wp-json\/wp\/v2\/comments?post=24710"}],"version-history":[{"count":1,"href":"https:\/\/azeidkgroup.com\/en\/wp-json\/wp\/v2\/posts\/24710\/revisions"}],"predecessor-version":[{"id":24726,"href":"https:\/\/azeidkgroup.com\/en\/wp-json\/wp\/v2\/posts\/24710\/revisions\/24726"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/azeidkgroup.com\/en\/wp-json\/wp\/v2\/media\/24701"}],"wp:attachment":[{"href":"https:\/\/azeidkgroup.com\/en\/wp-json\/wp\/v2\/media?parent=24710"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/azeidkgroup.com\/en\/wp-json\/wp\/v2\/categories?post=24710"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/azeidkgroup.com\/en\/wp-json\/wp\/v2\/tags?post=24710"},{"taxonomy":"azeidk_region","embeddable":true,"href":"https:\/\/azeidkgroup.com\/en\/wp-json\/wp\/v2\/azeidk_region?post=24710"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}