Heat Detectors Introduction A heat detector is a fire detection device. It is similar to a smoke detector; however it is more resistant to false alarms in areas with a large amount of dust and debris. Since it does not detect smoke, it is therefore not meant as a replacement for a smoke detector. In fact, this type of sensor is used to detect changes in ambient temperature; alarms are triggered when the temperature gets too hot. The following will discuss: • Types of Heat Detectors Heat Detector- Types and Operation There are two types of heat detectors on the market today: • Fixed Temperature Fixed Temperature A fixed temperature heat detector makes use of a metal alloy. When the ambient room temperature exceeds the specified temperature for that particular device; the alloy melts and in turn give rise to an alarm. Normally the fixed temperature for these detectors is 115°F to 135°F. It is important to replace this type of heat detector once an alarm has been triggered; if the metal alloy melts, the detector is worthless.
Rate of Rise This type of heat detector employs a sensing component; used to detect rapid or slow/steady increases in the ambient room temperature. This type is slightly more sensitive than the fixed temperature detector. There are two scenarios that can cause an alarm: • A sudden and abrupt change in temperature. One type of detector is not better than the other; rather they have different purposes. For example, you would not put a rate of rise type in a kitchen; for the reason that when the oven door is opened a sudden change in room temperature would cause an alarm. A fixed temperature is not well suited in an area with highly combustible materials; in that an earlier warning is usually required. Configuration There are two ways with which heat detectors can be configured: • Independently Independently One heat detector is directly wired to an input on the fire alarm panel. This is perhaps the better configuration in that when an alarm occurs, the area of the fire is indentified. Two or More in Parallel
Applications The following is a list of possible applications for heat detectors: • Garage  |
As explained in the following diagram. Two or
more detectors are wired in parallel to one input on the
fire alarm panel. This is useful when a large area must be
protected (industrial application). If all devices are
within the same room, then the area in alarm will be
easily identified. If however, the devices are mounted in
separate areas this can cause confusion as to which area
is in alarm.
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