SSO
Switched socket outlet
Plan mark for a socket outlet with its own integral switch that controls the supply to the plug.
IEC
Symbols · FCU
Fused connection unit plan mark
Plan mark for a fused connection unit that feeds fixed equipment through a cartridge fuse instead of a plug.
In plain English
What does Fused connection unit plan mark mean?
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.
A simple 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.
What the drawings help you do
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.
This particular reference
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.
- Normally open / normally closed
- The contact state in the normal condition defined for the drawing.
- Terminal
- An identified point where a conductor connects.
- Rating
- A value stating the conditions for which equipment is specified.
Read the source: Electrical installation design methodology and references · IEC graphical symbols for diagrams
GA · FCU
What it represents
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.
How to read it
- Read the fuse rating written beside the symbol, often 3 A or 13 A.
- Check whether the switched or unswitched version is required.
Information to show or reference
- State fuse rating and switched or unswitched type.
- Name the fixed appliance it serves.
- Show the flex outlet or rear cable entry.
A distinction that matters
A switched socket outlet accepts a plug; a fused connection unit is wired to fixed equipment.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Electrical installation design methodology and references
Installation design methodology context: circuits, outlets and final distribution are planned before symbols are placed.
IEC graphical symbols for diagrams
IEC committee context for graphical symbols used in diagrams and installation documents; not a source of reproduced artwork.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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