(Photo: courtesy of Big Ass Fans Co.)
Wind + Water
How much impact do high-volume, low-speed fans have on sprinkler system effectiveness in storage facilities?
NFPA Journal®, March/April 2011
By Fred Durso, Jr.
Spinning from the ceilings of storage and manufacturing facilities across the country, high-volume, low-speed (HVLS) fans provide energy-efficient air movement by virtue of their size: the fans measure 12 to 24 feet (3.6 to 7.3 meters) in diameter, the latter being five times the diameter of a typical residential ceiling fan.
Research Foundation Exec. Director Kathleen Almand describes the two phases of the NFLS study.
The dimensions and increasing popularity of these behemoths have gotten the attention of property insurers, as well as the Technical Committee on Sprinkler System Discharge Criteria that helps develop the design rules for NFPA 13, Installation of Sprinkler Systems. These groups, among others, have voiced concerns over whether the fans affect fire suppression systems in storage facilities. Through its two-phase study, HVLS Fans and Sprinkler Operation Research Program, the Fire Protection Research Foundation commissioned an investigation into the obstruction of sprinkler spray patterns and how fan-induced airflow affected the rate of fire spread through palletized and rack storage arrays.
Released in February, the project’s Phase II report, available at nfpa.org/foundation along with the Phase I report, concludes that HVLS fans, when installed with specific restrictions on installation and shutdown procedures, do not impair a sprinkler system’s performance. Advancing this data, the Sprinkler System Discharge Criteria Committee has formed a new HVLS fans task group to determine code provisions for the fan’s operation.
"This project is an example of the Foundation’s role in developing guidance to ensure that the implications on fire control and suppression of new technology are appropriately addressed," says Kathleen Almand, the Foundation’s executive director. "This comprehensive research program provides guidance to help ensure that the installation of HVLS fans does not compromise fire safety. The project illustrates the leadership of the insurance industry and NFPA committees in proactively addressing fire safety issues."
Bigger is better
Making their initial appearance in the 1990s, HVLS fans, according to the insurance industry, have become a popular staple in storage settings since they efficiently circulate large volumes of air via aluminum blades. Desired airflow is also achieved at speeds lower than those used by conventional, smaller fans, providing cooler work environments in the summer and circulating rising heat in the winter. Certain fans tested with this study, for example, had "full speeds" of only 63 revolutions per minute, creating airflow of about 330,000 cubic feet (9345 cubic meters) per minute.
"This is a product that allows coverage of a large area…for low initial cost and drastically improved worker comfort," says Paul Lauritzen, senior director of special projects for Big Ass Fans Co., one of three HVLS fan manufacturers that participated in the Foundation study. "As companies look for more efficient means to manage their buildings, these fans are becoming a key component of a sensible, simple, efficient system for thermal comfort and energy savings."
Responding to the fan’s popularity, the insurance industry and the Sprinkler System Discharge Criteria Committee prompted the Foundation to begin a testing program that quantifies the device’s effect on sprinkler operations in storage and manufacturing facilities. Phase I of the HVLS Fan and Sprinkler Operation Research Program began in 2008 and explored the interaction between the fans and early suppression fast-response (ESFR) sprinklers as plastic commodities were burned in rack storage arrays. Used in many storage settings, ESFR sprinklers have increased water flows and a quicker response to a fire compared to the alternative, control mode density area (CMDA) sprinklers.
Phase I test results, which applied only to 30-foot-high (9-meter-high) facilities with 20-foot (6-meter) storage heights, indicate that HVLS fans did not affect the performance of ESFR sprinklers to an "unacceptable level." Successful sprinkler performance was also achieved without fan shutoff during the tests, which were completed for the Foundation by Aon Fire Protection Engineering, formerly Schirmer Engineering.
Since fan shutdown, storage height, and other parameters weren’t fully explored during Phase I, researchers recommended another round of tests. On deck for Phase II were additional configurations of rack storage with ESFR sprinklers, the evaluation of ESFR sprinkler performance on palletized storage arrays, the effects of CMDA sprinklers on both rack and pallet storage, and measuring the airflow created by HVLS fans in the flue spaces of each array. Flue spaces are the space between racking rows or areas on either side of a racked pallet.
"We narrowed the boundaries in Phase I and tested all of them in Phase II," says Garner Palenske, the study’s project manager from Aon Fire Protection Engineering and member of NFPA’s Technical Correlating Committee on Automatic Sprinkler Systems and Sprinkler System Discharge Criteria committees. "Phase II was a concentrated fire test effort to apply what we learned in Phase I to the different arrays and sprinklers."
Phase II testing took place from June to December last year at the FM Global Research Campus in West Glocester, Rhode Island, and the Underwriters Laboratories fire test facility in Northbrook, Illinois. For all of those tests, researchers filled pallets and double-row racks with cartoned, unexpanded Group A plastics, a material used to create certain toy products, due to its high heat-release rate. The new rack storage tests for ESFR sprinklers were designed to challenge the system to its limit by maximizing storage and ceiling height while HVLS fans were at full speed. As listed in NFPA 13, the tallest ceiling height allowed for these storage arrays — 40 feet (12 meters) — was selected. Design guidelines from manufacturers outline a clearance of up to 5 feet (1.5 meters) between the fan and the ceiling, and the same from the fan to the rack below. Using a fan 24 feet (7 meters) in diameter, researchers selected a 30-foot (9-meter) storage height for three of the four rack storage tests. The fourth had a storage height of 15 feet (4.5 meters) to mimic a "high-clearance" condition. Compliance with this clearance is consistent with the treatment of HVLS fans as sprinkler obstructions, which are also governed by NFPA 13.
To determine parameters for ESFR sprinkler tests with palletized arrays, researchers surveyed 46 warehouses to confirm that HVLS fans were primarily located over areas typically occupied by people, predominantly in loading docks or sorting/picking areas, although some storage locations were identified. The survey established maximum ceiling and pallet storage heights of 40 feet (12 meters) and 15 feet (4.5 meters), respectively.
ESFR tests for both rack and storage included ignition at one of two locations — one near the tip of the fan blade and another under the fan hub. Researchers chose the former based on fan performance data and the latter because it was considered the "most challenging" location in Phase I. The fan was centered between four sprinklers in all but one test. Researchers established pass/fail criteria for the tests, which passed if the fire was confined to the ignition array, not more than eight sprinklers operated, and ceiling gas temperatures were such that exposed structural steel would not be endangered.
Both ESFR tests for palletized storage array were successful, since a maximum of six sprinklers activated and the damage that occurred was within acceptable parameters. Passing tests of rack storage arrays (30-foot (9-meter) storage, 40-foot (12-meter) ceiling) occurred when HVLS fans at full speed were shut down with a 90-second delay upon water flow, as allowed by NFPA 72®, National Fire Alarm and Signaling Code®. Four sprinklers operated, and commodity damage and ceiling temperatures were also within acceptable performance criteria.
Even more surprising, says Palenske, were the CMDA sprinkler tests on palletized arrays stacked 15 feet (4.5 meters) high under a 25-foot (7.6-meter) ceiling, the highest storage height allowed by both NFPA 13 and FM Global standards for CMDA sprinklers. Tests passed if a maximum of 20 sprinklers operated, the fire didn’t burn to the end of the main test array or "jump the aisle," and ceiling gas temperatures didn’t endanger structural steel. Fan operations were controlled by the shutdown of the fan by the activation of an air-sampling-type detector or an ionization spot detector, or by shutdown 90 seconds after the first sprinkler water flow. Six, seven, and twenty sprinklers, respectively, operated during these three tests, with the results well within performance parameters.
CMDA sprinkler protection on rack storage wasn’t tested, since previous test results indicate that they could adequately protect the arrays while HVLS fans are operating.
"The committee now has about 20 tests from Phase I and II to digest what’s going on," Palenske says. "You usually get one fire test to base your [code substantiations] on."
NFPA’s new HVLS fan task group, formed in December, will analyze the study results before considering revisions to the standard. Also in the works from the NFPA 13 Committee are modifications to the requirements for other configurations in industrial and storage occupancies. Information from the HVLS fans study will assist with these projects, adds Palenske. "The task group will have all of this great data to look at to come up with informed, scientifically based code language. It’s a very substantial, scientific validation of what we’re doing."
Fred Durso, Jr. is staff writer for NFPA Journal.