FENWAL DAF 27121-000

The DETECT A FIRE sensors are designed with the COMPENSATION principle. The DAF reacts accurately to the temperature of the air surrounding it, depending on the development of the fire. At a predetermined danger threshold the sensor intervenes. The maximum temperature sensors must be completely heated to the alarm value before intervening, therefore in the event of rapidly developing fires, a disastrous delay in the alarm signal is foreseeable. Pure differential sensors, on the other hand, are extremely subject to false alarms, due, for example, to harmless temperature changes caused by the release of hot air (for example when opening a process furnace). The external body of the DAF has a high thermal expansion index, linked to the temperature of the surrounding air. The internal machinery, on the other hand, has a very low expansion coefficient. A slow-moving fire, simultaneously expanding the external body and the internal machinery, will activate the sensor at the alarm temperature. A temperature gradient of up to 4.44 ° C / min (40 ° F / min.), Will act on the external body, but will not be able to make the internal machinery intervene. By ignoring hot air transients, the DAF virtually eliminates the false alarms prevalent in gradient detectors. In the case of rapidly developing fires, the external body will expand rapidly so as to cause the intervention of the internal machinery. The faster the focus will develop, the faster the sensor will intervene.