Planning for freezing temperatures during the sweltering summer might not be the first thing on anyone’s to-do list in the fire sector. But in the case of sprinkler-system freeze protection, this is the year it should be. NFPA standards are pushing best practices to new heights, so advance planning, insights from the field and even some outside-of-the-box thinking will be useful to prepare for safe, effective freeze protection in sprinklered applications this winter and next.
Winter is coming… and so are new requirements
The NFPA 25 requirement that all existing antifreeze systems with an unlisted antifreeze must be drained and refilled with one that is listed by 30 September 2022 is fast approaching – only 18 months away. Listed antifreeze solutions must flow free through the pipes and never freeze when the temperature is at, or warmer than, its minimum-use temperature. Regardless of the components a manufacturer introduces into the antifreeze formulation to prevent freezing, the sprinkler system must be able to suppress the fire.
Now, factory premixed solutions are the standard practice. This requirement ensures the antifreeze maintains its fire performance as per its UL safety certification, eliminating the potential for human error in mixing and ensuring that a precise formulation is always used.
Winterizing ‘above the line’
Listed antifreezes have minimum-use temperatures engineered for suitability in unlimited exterior uses. For example, freezemaster™ antifreeze’s minimum-use temperature is -12°F (-24°C). Structures located in most areas of the United States and along the east and west coastal areas of Canada are prime targets: these regions appear on or below the line (see Figure 1), ranging from Boston, Massachusetts to Vancouver, British Columbia. But what about northern areas of the US and Canada where temperatures drop much lower? Don’t count out the thousands of partially conditioned interior spaces that are suitable candidates for this type of protection as well.
Buildings with small unheated areas vulnerable to freezing often charge sprinkler pipes with water during the summer only. During the coldest months when there is a risk of freezing, the pipes are drained and charged with air under pressure. These spaces may be heated on average to 50°F (10°C) but can drop below freezing if an outside door is open or the heat can’t keep up with severe cold at night. Structures outfitted with these ‘tail end’ hybrid systems are good candidates for a listed antifreeze, such as:
- Small walk-in freezers and refrigerators
- Temperate small parking garages
- Small cold-storage facilities
- Roof access hatches
- Basement garbage rooms
- Industrial refrigeration equipment
- Pits in heated buildings
- Surge areas
- The first few heads of a heated parking garage
- Obstruction heads below bay doors
- Tunnels/corridors in heated industrial applications with large-diameter piping but not much heating capacity
Insights from field experience
After the creation of the NFPA standard in 2013 and before listed antifreezes were commercially available, many contractors designed and installed dry systems in new construction projects that required freeze protection, especially in applications like attics, unheated warehouses, commercial freezers, overhead canopies, loading docks and parking garages.
While dry systems can be the right freeze-protection solution for some applications, this past winter uncovered several instances in which dry systems increased costs for sprinkler contractors and building owners alike. The drawbacks reported to us can be assessed in terms of corrosion mitigation costs, installation costs and maintenance costs.
- Corrosion mitigation costs – In order for fire sprinkler systems to function as designed, they must be protected from damaging corrosion, which can flourish in wet and dry sprinkler systems. While wet systems are permanently charged with static water that is released when the sprinkler activates, the term ‘dry’ system is something of a misnomer in the sense that this type of fire protection is subject to condensation from the compressed air equipment that charges the pipework. To address the issue, and because inert nitrogen acts as a drying agent, many facilities have opted to replace the atmospheric air of the dry system with a costly nitrogen generator instead of a compressor.
- Installation costs – Dry-pipe sprinkler systems typically require ten additional system components, compared to just four for antifreeze systems. (See Figure 2) Further, to avoid the aforementioned corrosion in dry systems, the sprinkler system piping must be pitched to promote drainage of condensation at its lowest points (see NFPA 13 188.8.131.52). The arrangement requires piping to be pitched ½in per 10ft (4mm/m) for all branch lines, and ¼in per 10ft (2mm/m) for all other sprinkler piping. This adds to installed costs, as it requires auxiliary drains for each pipe section to collect condensates from the pressurized air while minimizing loss of air pressure during maintenance. These systems are also often equipped with heat tracing to provide freeze protection for the low-point drains and prevent blowouts, the cost of which ranges widely. In smaller facilities or those with complex roof systems, the need for pitched piping presents installation and inspection challenges.
- Maintenance costs – Besides the dedicated staff time needed to inspect and drain any sprinkler system, the extra components of a dry-pipe sprinkler system add up to more parts that can malfunction and require maintenance and/or replacement. Thus, maintaining dry systems can be three to four times higher than the initial installed cost, especially if a dry-pipe valve has been persistently leaking or the compressor has needed excessive repair.
Getting ready and staying vigilant
The September 2022 deadline is the date the conversion to a listed antifreeze must be completed, not started. For building owners with antifreeze systems, this means making a decision ahead of the next annual visit by your qualified sprinkler system inspection, testing and maintenance (ITM) contractor. For fire-sprinkler contractors, it means beginning to actively encourage clients to not only get a head start on compliance but also enhance their life-safety practices. After all, a listing provides the peace of mind that the antifreeze meets or exceeds the most rigorous standards and, unlike an unlisted antifreeze, will not explode or contribute to the heat release rate of a fire.
Once this step has been taken, NFPA 25: Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems governs future actions, requiring antifreeze systems to be tested for composition effectiveness annually at the most remote portion and where it interfaces with the wet-pipe system. For systems over 150 gallons, one additional test point is conducted every 100ft. This is crucial because leaks, pressure surges or temperature changes can cause antifreeze to flow out of the system or water into the system, leading to changes in the freeze temperature and antifreeze concentrations. Both of these measures must be maintained at 100% accuracy. If a sample shows a concentration outside the desired range, the system must be drained and refilled; it cannot simply be topped up.
Bottom line: best practices for wet sprinkler systems had to address past life-safety issues associated with antifreeze use. For manufacturers, this entailed a significant balancing act in the laboratory. It didn’t happen overnight, but the advances in life safety were priceless. And that’s why summer 2021 is the time to plan to make the most of those advances.
Consider these questions in selecting an antifreeze for your fire sprinkler system:
- Does it meet the rigorous technical challenges of becoming listed as required by NFPA standards?
- Is it listed and approved for use with the application and the size of the system?
- Will it protect the system against damage from exposure to the severe cold?
- How does it contribute to the prevention of damaging corrosion?
For more information, go to www.freezemaster.com/summer