This is the standard THERMOFLEX™ double circuit detector, in which one set of contacts is Normally Open (N/O), and the other set of contacts is Normally Closed (N/C). The connectivity is modified with pigtail leads that extend through a seal plate. This provides for enhanced protection against corrosive or moisture-laden environments.

The model number suffix  “-2CO”, indicates that the detectoir is a double circuit with one set of Normally Open (N/O) contacts, and one set of Normally Closed (N/C) contacts.  The N/O contacts are provided with a pair of black leads connected to one side of the contacts and a pair of white leads connected to the other side. The N/C contacts have a blue lead to each side.


This detector is suitable for use in areas where condensation or corrosion couldn have harmful effects on circuit wiring connected to standard terminals. Its seal plate (with extended pigtail leads) will mount onto a typical cast exterior back box or standard 4-inch octogon box.The detector is connected to a fire alarm system’s input circuit as an initiating device.The internal contacts will operate when the detector is sbjected to either a rate of temperature increase, or if the releasing temperature is reached. With its non-metallic diaphragm, the detector can operate normally at low temperatures, making it suitable for non-heated or chilled environments including garages and carports.

The set of N/C contacts are used to activate a local ancillary function that includes elevator recall, release of magnetically-held doors, local signal operation, local annunciation, etc.  In many cases this set of contacts will be connected to a controlling relay that is used to switch heavier voltages.


Combination Rate-of-Rise & Fixed Temperature

The Model Number prefix “CR” indicates that the detector is a combination Rate-of-Rise and Fixed Temperature, (often referred to as “Dual-action”), unit.  The Rate-of-Rise function allows the detector to close one set of its contacts and open the other set when the temperature at the ceiling increases at a rate of 8.4 Celsius degrees (15 Fahrenheit degrees) per minute.  In most cases, the closing of one set of contacts initiates the Fire Alarm sequence.  The second set of contacts (N/C), is commonly used to initiate an ancillary function. The Fixed Temperature portion consists of a spring-loaded plunger held in place by a eutectic solder that will fuse at the specific temperature (in Fahrenheit degrees) as indicated by the Model Number i.e. 135, 165, and 200 degrees.

Fixed Temperature Only

The Model Number prefix “CF” indicates that the detector is Fixed Temperature Only, and will therefore not respond to a rate of temperature increase but will operate when the detector fuses at the prescribed (Fahrenheit) temperature as indicated by the model number, i.e. 135,165,200 and 285 degrees.  This detector is referred to as “Fixed Temperature Only, non-restorable”.