Protection of Fire Protection Systems from Freezing
With the harsh winter many areas of the country are suffering from lower than normal temperatures making the protection of their fire protection systems from freezing more of an issue. As stated in NFPA 13
188.8.131.52.1 Unless the requirements of 184.108.40.206.2 are met, where portions of systems are subject to freezing and temperatures cannot reliably be maintained at or above 40°F (4°C), sprinklers shall be installed as a dry pipe or preaction system.
220.127.116.11.2 allows the use of antifreeze systems in small areas in lieu of dry pipe or preaction systems. As NFPA does not define small areas with a specific number the size is usually up to the contractor to determine due to the cost of the system verses a dry pipe system. Also the local building codes may specify and the Authority Having Juristiction (AHJ) may have input as to area and size limitations. In Florida we use NFPA 1 and it has no specifics on size limitations.
NFPA also states methods of protecting water filled pipe.
18.104.22.168.3* Where aboveground water-filled supply pipes, risers, system risers, or feed mains pass through open areas, cold rooms, passageways, or other areas exposed to freezing temperatures, the pipe shall be protected against freezing by insulating coverings, frostproof casings, or other reliable means capable of maintaining a minimum temperature between 40°F (4°C) and 120°F (48.9°C).
In many areas such as here in northern Florida, they feel that simple insulation is sufficient to protect against freezing. But if the cold spell is long enough, without a heat source, freezing is inevitable. Insulation can only slow the transfer of temperature, not prevent it. So unless the water is moving, which is not the case in fire sprinkler piping, some source of heat must be provided. This is generally what they mean by “other reliable means” This could be a unit heater or heat tape, etc.
I know that this time of year fire sprinkler contractors make a good deal of money fixing damage from freezing. But if we don’t help the customer, and advise how he needs to prevent future damage are we really doing our jobs?