THERMOFLEX™ is the brand name for a series of automatic Heat Detectors that form an integral part of a Fire Alarm System. They are connected to a fire alarm panel as an Alarm Initiating Device in conjunction with other devices such as smoke detectors , manual stations, and water flow switches.

The THERMOFLEX™ heat detector is designed to initiate an alarm condition if it detects a rate of temperature increase of 15°F (8.4°C) over one minute, at the ceiling. This is referred to as the “rate-of-rise” function.

The unit will also initiate an alarm condition if the ceiling temperature reaches a pre-determined level. This is referred to as the “fixed temperature” function.

A standard THERMOFLEX™ heat detector combines the rate-of-rise and fixed temperature unit.

The air chamber of the unit is sealed, with the exception of a small orifice. As the ceiling temperature increases, the expanding air trapped in the chamber is allowed to escape through the orifice. The rate at which the air escapes is governed by a calibrated restrictor. If the temperature increases at a rate of 15°F (8.4°C) per minute, the air inside the chamber expands faster than it can escape. The increasing pressure inside the chamber begins to depress a thin diaphragm which, in turn, pushes a contact against a fixed contact point. This contact closure initiates a fire alarm response.

Every THERMOFLEX™ unit has a device that provides for fail-safe operation. Should the ceiling temperature rise at a rate less than 8.4 Celsius degrees per minute ( 15 F°), a spring loaded plunger held in place by a special alloy, will release at a specific temperature. The plunger strikes the contacts and holds them closed. The contact closure initiates a fire alarm condition.

The standard releasing temperature is 135°F (57°C).

There are many instances where ceiling temperatures are normally much higher than usual, e.g. furnace and laundry rooms, kitchens and  saunas. THERMOFLEX™ offers three fusible settings that are higher than the standard 135°F. These are:
  o    165°F (74°C)
  o    200°F (93°C)
  o    285°F (140°C)
 

In some instances, rapid (yet normal) temperature increases would cause the rate of rise portion of the detector to operate, resulting in a false fire alarm. Locations where this can occur include boiler rooms, janitor closets with hot water sinks, kitchens, saunas, etc.

In these situations, the “Fixed Temperature Only” unit should be used. With this unit, the rate of rise function is disabled in such a way that the construction of the thermostat is virtually unchanged. The expanding air is allowed to vent to atmosphere, which prevents a pressure build-up in the air chamber.

Although Fixed Temperature Only units fulfill a specific need, they should be regarded as exception to the rule, with the combination rate-of-rise and fixed temperature unit considered as the standard detector.
 

In a word: Reliability. As a life safety device, it is extremely important that the THERMOFLEX™ detector be designed and manufactured to maximize its ability to sense and respond to a specific rate of temperature increase. This important tracking capability does not change with time. With the THERMOFLEX™ series, calibration procedures at the time of manufacture ensure that repeated field testing of the detector does not affect its capability to respond properly to a temperature increase. The quality of a detector is determined by its ability to maintain its calibrated settings over long period of time without “wandering”.

It is a well-known fact that the THERMOFLEX™ line of heat detectors has performed unfailingly in the North American market for over three decades, and is the brand selected by alarm installers and electrical contractors who are interested in supplying the most reliable heat detector in safety-to-life situations. The reason for this popularity is simple: the unit does not change its operational characteristics over time but remains stable test after test, year after year.
 

Affixed to the heat-collecting fin are differently colored, round dots that can be seen from the floor. The color code for these dots is:
  o    No Dot: Combination of rate-of-rise & fixed temperature, 135 °F
  o    White Dot: Combination rate-of-rise & fixed temperature, 200 °F
  o    Gray dot: Combination rate-of-rise & fixed temperature, 165 °F
  o    Black dot: Fixed temperature only, 135 °F
  o    Black dot and grey dot: Fixed temperature only, 165°F
  o    Black dot and white dot: Fixed temperature only, 200 °F
  o    Black dot and Blue dot: Fixed temperature only, 285 °F
 

Definitely. Fire Detection Devices Ltd. offers two types of guards for protection of the unit, which can be added during or after installation.  WG150 is a welded wire cage that encloses the entire unit, providing complete protection from any potentially damaging blows.

WG152 consists of a wire cage that is fastened to a standard cover plate. This unit is ideal for less hazardous locations, such as kitchens or stock rooms.
 

The prefix “CR” means the unit is a Combination Rate-of-Rise and Fixed Temperature type. The prefix “CF” means the unit is a “Fixed Temperature Only” type.
After the prefix, a temperature setting relating to the fusible alloy is given in Fahrenheit degrees – either 135, 165, 200, or 285.
We then indicate what type of contact configuration is in the unit, namely:
  o    “2” – two sets of normally open contacts
  o    “C” – one set of normally closed contacts
  o    “2C” – two sets of normally closed contacts
  o    “2CO” – one set of normally open contacts and one set of normally closed
  o    If none of the above appear immediately after the temperature setting, the detector is a standard single circuit, normally open
The next component of the Model Number is the Special Environment suffix, namely:
  o    MP – Modified Pigtail (sealed). A seal plate on the back of the unit prevents corrosion of the contacts and terminal screws.  Pigtail leads are attached at the factory.
  o    EWT – Explosion proof, Water (and dust) Tight.
The final component of the Model Number is:
  o    LED – This indicates that the detector has a visible Light Emitting Diode that turns on if the detector has initiated an alarm. The LED unit is only available in single circuit, normally open.
 

 o    The entire THERMOFLEX™ product line is listed by Underwriters’ Laboratories of Canada (ULC)
 o    The entire line, with the exception of the Explosion Proof unit, is listed by Underwriters’ Laboratories (UL) in the United States
 o    CSFM
 

The listed Standard Spacing Parameters are described as follows:
 o    “The standard spacing between THERMOFLEX™ detectors, for the rate-of-rise function, is 70 feet (21.35 m) on a flat, uninterrupted ceiling up to 3 meters (10 feet) in height.”
 o    “The standard spacing between THERMOFLEX™ detectors for the Fixed Temperature Only function is 40 feet (12m) on a flat, uninterrupted ceiling up to 3 meters (10 feet) in height.”