Meeting NFPA 25’s minimum-temperature requirements for wet-pipe sprinkler systems
NFPA Journal®, January/February 2011
Everyone involved with fire sprinkler systems in areas that are subject to freezing should be aware of the recent efforts to address the combustibility of antifreeze solutions.
While NFPA technical committees investigate and address this subject, more attention is being given to alternatives, such as protecting wet-pipe systems against freezing by properly placing the piping in heated spaces and insulating it against the cold.
Wet-pipe sprinkler systems are often preferred to dry-pipe and preaction sprinkler systems because they are simple and reliable. However, water-filled piping in colder climates must be kept at a minimum temperature of 40oF (4.4oC).
Where buildings are well insulated and heated, system piping must be installed in the insulated envelope. Any insulation that gets between the sprinkler piping and the heated area of the building isolates the piping from the heated space. Simply wrapping water-filled fire protection piping with insulation is generally discouraged, as it does nothing to generate or preserve heat.
The new 2011 edition of NFPA 25, Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, contains a significant change that relates to the protection of fire protection piping against freezing.
In previous editions, subsection 5.2.5, "Buildings," called for an annual inspection for proper protection against freezing, stating that "prior to the onset of freezing weather, buildings with wet-pipe systems shall be inspected to verify that windows, skylights, doors, ventilators, other openings and closures, blind spaces, unused attics, stair towers, roof houses, and low spaces under buildings do not expose water-filled sprinkler piping to freezing and to verify that adequate heat [minimum 40oF (4.4oC)] is available."
Paragraph 18.104.22.168 of the new edition replaces this wording, saying simply, "The building owner shall ensure that all areas of the building containing water-filled piping shall be maintained at a minimum temperature of 40oF (4.4oC) and not exposed to freezing conditions."
This new wording clarifies that keeping sprinkler systems warm is not something that can be checked on a one-time, annual basis, but must be done throughout the winter.
Too often, the inspection required before the onset of freezing weather was confused with the fire protection system inspections performed by outside contractors. The new standard now clarifies that system inspections are examinations of the systems themselves and that they are intended to verify that the systems are in operating condition and are free of damage.
Building owners are aware of various maintenance activities that can have an adverse effect on a building’s insulative envelope. For example, installation of outside lighting can dislodge insulation from a building’s eaves. Running electrical cables or reworking other piping systems can result in holes cut through insulated ceilings or concealed spaces in which NFPA 25 does not require system inspectors to check either the sprinklers or piping.
In general, the biggest threat to a building’s insulative envelope results from building repairs and alterations that take place during warm weather, when the prospect of freezing seems so remote.
The change in the 2011 edition of NFPA 25 does not mean that checking a building’s thermal integrity is no longer important. It simply clarifies that the owner is in the best position to perform that check and that the check should be ongoing rather than a single, annual event.
Russell P. Fleming, P.E., is the executive vice-president of the National Fire Sprinkler Association.