{"schemaVersion":1,"slug":"fused-connection-unit-plan-mark","name":"Fused connection unit plan mark","kind":"symbol","abbreviation":"FCU","aliases":["fused spur","fused connection unit","switched fused spur"],"category":"installation-communications","drawingTypes":["GA"],"referenceFamilies":["IEC"],"summary":"Plan mark for a fused connection unit that feeds fixed equipment through a cartridge fuse instead of a plug.","description":["A fused connection unit, often called a fused spur, connects a fixed appliance such as a towel rail, extractor fan or boiler directly to a final circuit through a small cartridge fuse. Plans commonly draw a small square with an S-shaped fuse mark or the letters FCU at the wall line, sometimes with a switch stroke for the switched type.","The symbol is common in British-style layouts on ring final circuits, where fixed loads must be fused down from the circuit rating. The reader should check the fuse rating and whether a flex outlet is fitted on the front or the cable leaves from the back of the box.","It is not a socket outlet: no plug is involved. It also does not provide isolation suitable for mechanical maintenance unless the specification says so."],"readingNotes":["Read the fuse rating written beside the symbol, often 3 A or 13 A.","Check whether the switched or unswitched version is required."],"drawingChecklist":["State fuse rating and switched or unswitched type.","Name the fixed appliance it serves.","Show the flex outlet or rear cable entry."],"distinction":"A switched socket outlet accepts a plug; a fused connection unit is wired to fixed equipment.","facts":[{"label":"Typical loads","value":"Towel rails, extract fans, boilers, hand dryers"},{"label":"Protection","value":"Cartridge fuse in the accessory"},{"label":"Preview","value":"Independent educational concept; plan symbols for this device vary between legends, so read the project key"}],"references":[{"sourceId":"pub-object-engineering-design","relevance":"Installation design methodology context: circuits, outlets and final distribution are planned before symbols are placed."},{"sourceId":"iec-diagrams","relevance":"IEC committee context for graphical symbols used in diagrams and installation documents; not a source of reproduced artwork."}],"related":["iec-switched-socket-outlet","iec-flex-outlet-plate"],"artwork":"s28-fused-connection-unit-plan-mark","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","plainEnglish":{"title":"What does Fused connection unit plan mark mean?","introduction":"A fused connection unit, often called a fused spur, connects a fixed appliance such as a towel rail, extractor fan or boiler directly to a final circuit through a small cartridge fuse. Plans commonly draw a small square with an S-shaped fuse mark or the letters FCU at the wall line, sometimes with a switch stroke for the switched type.","example":"The symbol is common in British-style layouts on ring final circuits, where fixed loads must be fused down from the circuit rating. The reader should check the fuse rating and whether a flex outlet is fitted on the front or the cable leaves from the back of the box.","drawings":"It is not a socket outlet: no plug is involved. It also does not provide isolation suitable for mechanical maintenance unless the specification says so.","terms":[{"name":"Normally open / normally closed","meaning":"The contact state in the normal condition defined for the drawing."},{"name":"Terminal","meaning":"An identified point where a conductor connects."},{"name":"Rating","meaning":"A value stating the conditions for which equipment is specified."}],"diagram":"flow","steps":["Identify the device and form","Read the connections and state","Check the equipment reference"],"caption":"A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.","sources":[{"label":"Electrical installation design methodology and references","url":"https://www.electrical-installation.org/enwiki/General_rules_of_electrical_installation_design"},{"label":"IEC graphical symbols for diagrams","url":"https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/"}],"detail":"Plan mark for a fused connection unit that feeds fixed equipment through a cartridge fuse instead of a plug. A switched socket outlet accepts a plug; a fused connection unit is wired to fixed equipment.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/fused-connection-unit-plan-mark","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/fused-connection-unit-plan-mark.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"pub-object-engineering-design","title":"Electrical installation design methodology and references","publisher":"Schneider Electric — Electrical Installation Guide","url":"https://www.electrical-installation.org/enwiki/General_rules_of_electrical_installation_design","type":"manufacturer","scope":"Public design context. No universal working clearance, equipment dimension or project compliance conclusion is asserted.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Installation design methodology context: circuits, outlets and final distribution are planned before symbols are placed."},{"id":"iec-diagrams","title":"IEC graphical symbols for diagrams","publisher":"IEC","url":"https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/","type":"standard","scope":"IEC 60617 and related symbol-design publications. Full database access requires a subscription.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"IEC committee context for graphical symbols used in diagrams and installation documents; not a source of reproduced artwork."}]}