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Baby It's Hot Outside – Fire Sprinklers Can Be Heat Stressed Too!

Blog Post created by david.hague Employee on Aug 16, 2018


The issue of temperature usually comes up in any discussion of sprinklers and sprinkler systems, and NFPA receives a great deal of questions related to the required temperature rating for sprinklers. This is important because any sprinkler that is located too close to a source of heat can result in an unintended activation. For many years sprinkler designers have known that a sprinkler located next to a unit heater, for example, must be either a high temperature rated sprinkler if located within a 7ft (2.1 m) radius around the unit heater, or an intermediate temperature sprinkler if located in the discharge pattern of the unit heater out to a distance of 20ft (6.1 m) (see Figure 8.3.2.5). There are many other examples of where a higher temperature rating is needed for sprinklers, such as in unventilated attic spaces, under skylights, or in unventilated show windows, etc.


Up until recently, all sprinklers within a building were required to be of the ordinary temperature rating unless located near one of the above mentioned heat sources, so it is not uncommon to have a variety of temperature ratings for sprinklers within the same building or sprinkler system. However, beginning with the 2010 edition of NFPA 13, ordinary and intermediate temperature sprinklers are now permitted for use throughout a building. Why the change? Many buildings are designed without the traditional dropped ceiling, leaving an unfinished space which incorporates a large number of Heating, Ventilation and Air Conditioning (HVAC) diffusers. The diffusers drive the need for a significant number of intermediate temperature sprinklers in addition to ordinary temperature sprinklers within a system. To accommodate such installations, the sprinkler committee decided to allow ordinary or intermediate temperature sprinklers throughout a building. Now that quick response sprinklers are required and with the knowledge that the activation time between the two temperature ratings is not significant, either temperature rating is allowed. Can we mix temperature ratings within the same building? Absolutely, although it is best to use the same temperature rating throughout if at all possible. Doing so makes the replacement of sprinklers at some point in the future a simple effort.

 

Another factor to consider is how sprinklers are stored and treated before and during installation. If a sprinkler system is being installed or roughed-in in a building under construction, the sprinklers can be exposed to an untreated space inside the building. If the temperature during construction is above 100°F (38°C), ordinary temperature sprinklers will be exposed to a temperature for which they are not rated (see Table 6.2.5.1). This situation can stress the glass bulb and cause unintended operation at a later time. This has already occurred in some parts of the country and is an on-going concern whenever an area experiences a heat wave.


Suppose the temperature where you live and work does not exceed 95°F (35°C); consider where the sprinklers might be stored in such situations. A box of sprinklers is usually labeled “Store in a cool dry place” by the manufacturer. Placing a box of sprinklers in a Conex box (a large metal storage container frequently used on construction sites) on a job site in the sun in 95°F (35°C) temperatures will expose the sprinklers to temperatures of 120°F (49°C) or more. This temperature is much too high for ordinary temperature sprinklers and is approaching the threshold for intermediate temperature sprinklers.


Sprinkler temperature ratings are designed for very specific uses. Treating sprinklers properly before and during construction is important to ensure that they operate only when needed. Baby, it’s hot outside, so avoiding heat stress is important for you and sprinklers!

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