HD-R
Rate-of-rise heat detector plan symbol
Fire alarm plan symbol for a heat detector that alarms on a rapid temperature increase as well as a threshold.
IEC
IEC · HD
Fixed-temperature heat detector plan symbol
Fire alarm plan symbol for a fixed-temperature heat detector that alarms at a set temperature.
In plain English
What does Fixed-temperature heat detector plan mean?
Fixed-temperature heat detectors alarm when the surrounding air reaches a set point, commonly around 57 to 90 degrees Celsius depending on class. Plans draw the detector box with a temperature mark or the letter H, often with a class tag.
A simple example
They are used where smoke detectors would false alarm, such as kitchens, plant rooms, car parks and dusty areas. The detection is slower than smoke, so coverage spacing is tighter and the reason for choosing heat should be clear. The symbol does not give the operating temperature or class. Check the schedule, especially in hot plant rooms.
What the drawings help you do
Confirm the class suits the ambient temperature. Check spacing, which is tighter than for smoke. A rate-of-rise detector responds to a fast temperature increase; this one only to an absolute threshold.
This particular reference
Fire alarm plan symbol for a fixed-temperature heat detector that alarms at a set temperature. A rate-of-rise detector responds to a fast temperature increase; this one only to an absolute threshold.
- Rating
- A value stating the conditions for which equipment is specified.
- Schematic
- A drawing showing function and connections rather than physical appearance.
Read the source: IEC graphical symbols for diagrams · Electrical installation design methodology and references
IEC · Heat detector, fixed temperature
IEC 60617 installation-plan style (architectural and topographical installation symbols); independently drawn, not certified IEC geometry or a database identifier.
Shown as an independently authored educational illustration. Use the cited publication and drawing legend to verify the required drafting form.
GA · HD
What it represents
Fixed-temperature heat detectors alarm when the surrounding air reaches a set point, commonly around 57 to 90 degrees Celsius depending on class. Plans draw the detector box with a temperature mark or the letter H, often with a class tag.
They are used where smoke detectors would false alarm, such as kitchens, plant rooms, car parks and dusty areas. The detection is slower than smoke, so coverage spacing is tighter and the reason for choosing heat should be clear. The symbol does not give the operating temperature or class. Check the schedule, especially in hot plant rooms.
How to read it
- Confirm the class suits the ambient temperature.
- Check spacing, which is tighter than for smoke.
Information to show or reference
- State class or operating temperature.
- Tag loop and address.
- Note why heat detection is chosen.
A distinction that matters
A rate-of-rise detector responds to a fast temperature increase; this one only to an absolute threshold.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
IEC graphical symbols for diagrams
IEC graphical symbol context for installation plans; independently drawn here.
Electrical installation design methodology and references
Installation design context: life-safety systems are coordinated with the building electrical design.
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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