MAN3041-1
14
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 of heat are part of the normal environment in the area protected by
the heat detector.
7.4
Environmental Performance:
The environmental performance is similar to that of the Orbis IS optical smoke detector but it should be
noted that heat detectors are designed to work at particular ambient temperatures (see Fig 3). Also
classification and BASEEFA certificate number are the same as for the optical smoke detector.
7.5
Technical Data:
Specifications are typical and given at 23°C and 50% relative humidity unless specified otherwise.
Detector
operating
principle:
Measurement of heat by means of a thermistor
Sampling frequency:
Once every 2 seconds
Supply voltage:
14-28V dc
Supply wiring:
2 wires, polarity sensitive
Polarity reversal:
Not allowed
Power-up time:
<20 seconds
Minimum
detector
active voltage:
12V dc
Switch-on surge current:
105µA at 24V dc
Quiescent current:
80µA at 24V dc
Alarm load:
325
Ω
in series with 1.0V drop
Material:
Detector and base moulded in white polycarbonate
Alarm Indicator:
Integral indicator with 360° visibility
Dimensions and weight
of detector:
100mm diameter x 42mm H
70g
Dimensions and weight
inc base:
100mm diameter x 50mm H
140g
Operating and storage
temperature:
-40°C to +70°C
Operating temperature is restricted by the intrinsic safety gas classification.
Class T5: - 40°C to +40°C Class T4: - 40°C to +60°C
The detector must be protected from conditions of condensation or icing.
Humidity:
0% to 98% relative humidity (no condensation)
Wind speed:
Unaffected by wind
Atmospheric pressure:
Insensitive to pressure
IP rating:
23D to EN60529:1992*
Electromagnetic
compatibility:
The detector meets the requirements of BS EN61000-6-3 for emissions and BS
EN50 130-4 for susceptibility.