There are two heat detectors in the XPander range, designed to suit a wide variety of operating conditions. A Static Heat Detector (CS) which responds only when a fixed temperature has been reached and a Rate-of-Rise Detector (A1R) which has a fixed upper limit, but in addition, measures the rate of increase in temperature.
Operation
Heat detectors have an open-web casing which allows air to flow freely across a thermistor which measures the air temperature every 2 seconds. A microprocessor stores the temperatures and compares them with pre-set values to determine whether a fixed upper limit–the alarm level–has been reached. In the case of rate-of-rise detectors the microprocessor uses algorithms to determine how fast the temperature is increasing. Static heat detectors respond only when a fixed temperature has been reached. Rate-of-rise detectors have a fixed upper limit but they also measure the rate of increase in temperature. A fire might thus be detected at an earlier stage than with a static detector so that a rate-of-rise detector is to be preferred to a static heat detector unless sharp increases in temperature are part of the normal environment in the area protected by the heat detector.
