Rate of Rise Heat Detectors
Introduction
Heat detector, thermal detector or temperature detector is a fire alarm device designed to respond when convective thermal energy from a fire increases the temperature of a heat-sensitive element. It is part of a fire detection systems. The thermal mass and conductivity of the element regulate the flow rate of heat in the element. All heat detectors have their thermal inertia. Heat detectors are classified according to their triggering mode into two types: "fixed temperature" and "thermovelocimetric" that act according to the speed of the temperature increase.
Currently, the detectors are powered from the zones or loops depending on the technology of the fire panel or control panel and are powered either at 24 V or at 220 V.
When the detector's temperature sensor reaches the maximum temperature (generally 64 °C with IP20 or 30 protection for indoor use) the detector is activated and passes the signal to the fire panel or directly to an extinguishing system. You can also find temperature detectors that are activated at higher temperatures to avoid deformation of the material and are called thermal probes.[1][2][3].
Fixed or thermofix temperature heat detectors
The fixed temperature (or fixed temperature) is the most common type of heat detector. Fixed temperature detectors operate when the heat sensor of the eutectic alloy reaches the state of changing the eutectic point from a solid to a liquid. Thermal retardation delays the buildup of heat in the sensitive element, so that a fixed temperature device will reach its operating temperature sometime after the temperature of the surrounding air exceeds that temperature. The most common fixed temperature point for electrically connected heat detectors is 58°C. Technological advances have allowed the perfection of detectors that activate at a temperature of 47 °C, increasing the available reaction time and the safety margin. This type of technology has been available for decades without the use of batteries or electricity.