When #@*% Hits the (HVLS) Fan

The use and market for high-volume low speed (HVLS) fans has increased significantly over the past several years. The concept of placing fans in buildings originally started in agricultural buildings in the late 1990’s to keep cows cool during hot summer months. Farmers realized the cows would produce little to no milk when they were too hot. HVLS fans generate cooler air, when felt on the body the cool air accelerates evaporation and this effect helps the body feel cooler. Manufacturers realized there was a need for large diameter fans in commercial and industrial environments to keep employees cool as well. Business owners found by installing HVLS fans, efficiency, and worker productivity improved. Studies show HVLS fans can lower temperature in an area by as much as 8°F. When workers feel better, the result tends to be increased productivity and efficiency.

What impact do HVLS fans have on sprinkler performance?

Sprinkler Fundamentals

We know sprinkler technology utilizes fundamentals of fire science and fire dynamics to successfully operate and apply water to a fire. Heat and flame will always spread using the scientific method of conduction, convection, and/or radiation. Conduction is the transfer of heat by direct contact (flame touching the other object). Convection is the transfer of heat through a liquid or gas. Radiation is the transfer of heat through rays, waves, or particles. Fire and flame will spread using all three of these methods. Building codes dedicate entire chapters to this topic by requiring fire rated walls, doors, dampers, sprinklers, fire caulking, and other similar materials. The goal from an NFPA 13 perspective is to detect and contain a fire by preventing the transfer of heat through the application of water as quickly and efficiently as possible.

HVLS Fans and Sprinkler Studies

In the early 2000’s, the impact of HVLS fans and its correlation to conduction, convection and radiation was yet to be determined. With the installation and use of HVLS fans increasing, the fire protection industry had more questions than answers if there was any correlation between HVLS fans and sprinkler performance. In 2007, the Property Insurance Research Group and NFPA’s Fire Protection Research Foundation (FPRF) did a study to evaluate the impact HVLS fans had on sprinkler operation. The study evaluated the following:

  • Conduct 10 different tests to determine if new language in NFPA 13 was necessary.
  • Evaluate the use of ESFR and CMDA sprinklers in relation to HVLS fans.
  • View the full FPRF report at: file:///C:/Users/JohnSwanson/Downloads/FPRF-2009-05_hvls%20(5).pdf.

The studies showed successful results were achieved when HVLS fans were centered approximately between four adjacent sprinklers and the fans shut down upon sprinkler waterflow. The conclusions drawn based on the test results were added to the 2013 Edition of NFPA 13, in Section 11.1.7.

  • The maximum fan diameter is limited to 24 ft (7.3 m).
  • HVLS fans shall be centered approximately between four adjacent sprinklers
  • The vertical clearance from HVLS fan to sprinkler deflectors shall be 36 inches
  • All HVLS fans shall be interlocked to shut down immediately upon a waterflow alarm. When the building is protected with a fire alarm system, this interlock shall be in accordance with NFPA 72.

What does a “fire alarm system” mean?

Fire Alarm Systems: Different Meanings by Different People

Unfortunately, the term, “fire alarm system” can have different meanings to different people. In this case, the term “fire alarm system” does not necessarily mean smoke and heat detection or occupant notification (horn/strobes) must be present in the building.

International Building Code (IBC) Section 903.4 requires valves controlling water supply for automatic sprinkler systems…to be electrically supervised by a listed fire alarm control unit. NFPA codes contain similar verbiage. There are some exceptions for smaller systems, but for the most part, every building provided with HVLS fans, should have a dedicated function fire alarm control unit to monitor for waterflow. The term, “dedicated function” was added to the 2007 Edition of NFPA 72 to clarify there are buildings that must have a fire panel installed to perform a specific function, but the occupancy itself does not meet the conditions for a full fire alarm system based on IBC Section 907. As an example, dedicated function fire alarm control units may be used for the following scenarios when a full building fire alarm system with detectors, pull stations and occupant notification isn’t required:

  • Monitor sprinkler waterflow
  • Control elevator detectors
  • Supervise duct detectors
  • Transmit signals to Central, Proprietary or Remote Supervising Station

The term dedicated function was added to NFPA 72 because some interpreted the codes to say that when a fire panel alone was installed to perform (or monitor) a specific function, the building now had a “fire alarm system”. In other words, it was being used as justification to install additional equipment (such as, automatic detection, manual pull stations and/or occupant notification) when the model codes didn’t necessarily require it. This interpretation is not supported by the IBC or NFPA 72.

As a point of reference, there was a correlation issue when NFPA 13 referred to NFPA 72 for interlocking of HVLS fans and sprinkler waterflow to the building fire alarm control unit. You will find no reference to HVLS fans in the 2013 or 2016 Editions of NFPA 72. This issue was addressed and corrected in the 2019 Edition of NFPA 72.

In conclusion, the installation of HVLS fans is becoming a common site in many industrial, commercial, and storage occupancies. It is important HVLS fans be installed in accordance with the criteria in NFPA 13, be connected to a building fire alarm control unit, and shut down upon sprinkler waterflow, for the automatic sprinkler system to work effectively.