# Rate-of-rise heat detector plan symbol

Canonical URL: https://eloragrid.ai/symbols/iec-rate-of-rise-heat-detector-plan-symbol
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: HD-R
Drawing use: GA
Reference families: IEC

## Symbol convention

Convention: IEC
Form: Heat detector, rate of rise
IEC 60617 installation-plan style (architectural and topographical installation symbols); independently drawn, not certified IEC geometry or a database identifier.

Fire alarm plan symbol for a heat detector that alarms on a rapid temperature increase as well as a threshold.

## In plain English

### What does Rate-of-rise heat detector plan mean?

Rate-of-rise heat detectors alarm when temperature climbs faster than a set rate, and usually also at a fixed threshold. Plans use the heat detector form with an added rising mark or an R tag to distinguish it.

### A simple example

They respond faster than fixed-temperature detectors to fast-growing fires, but can false alarm where temperature normally changes quickly, such as near ovens or doors to outside in winter. The plan location should be checked with this in mind. The symbol does not state the rate or threshold, which belong to the product class.

### What the drawings help you do

Look for the rising mark or R tag. Check for rapid ambient changes near the location. A fixed-temperature detector waits for an absolute threshold; rate-of-rise reacts to the speed of change.

### This particular reference

Fire alarm plan symbol for a heat detector that alarms on a rapid temperature increase as well as a threshold. A fixed-temperature detector waits for an absolute threshold; rate-of-rise reacts to the speed of change.

### Terms

- Schematic: A drawing showing function and connections rather than physical appearance.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/)


## What it represents

Rate-of-rise heat detectors alarm when temperature climbs faster than a set rate, and usually also at a fixed threshold. Plans use the heat detector form with an added rising mark or an R tag to distinguish it.
They respond faster than fixed-temperature detectors to fast-growing fires, but can false alarm where temperature normally changes quickly, such as near ovens or doors to outside in winter. The plan location should be checked with this in mind. The symbol does not state the rate or threshold, which belong to the product class.

## How to read it

- Look for the rising mark or R tag.
- Check for rapid ambient changes near the location.

## Information to show or reference

- State class.
- Tag loop and address.
- Avoid locations with rapid normal temperature swings.

## Important distinction

A fixed-temperature detector waits for an absolute threshold; rate-of-rise reacts to the speed of change.

## Facts

- Operating principle: Rate of temperature rise plus threshold
- False alarm risk: Rooms with fast normal temperature changes
- Exact standard graphic: Not reproduced here; confirm the form against IEC 60617 and the project legend

## Public references

- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/) — IEC. IEC graphical symbol context for installation plans; independently drawn here.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.