Wet chemical extinguishing systems are most commonly used to provide fire protection for commercial cooking operations.

They are pre-engineered systems – meaning they are proprietary – which contain predetermined flow rates, nozzle pressures, and quantities of agent required, specific pipe sizes, maximum and minimum pipe lengths, and most importantly are limited to the protection of hazards for which they have been specifically listed. So how does one complete an acceptance test for a pre-engineered wet chemical system once it is installed?

For many years, the approval of installation requirements provided in NFPA 17A, Standard for Wet Chemical Extinguishing Systems, contained four items. The industry was not standardized, and manufacturers’ manuals of the pre-engineered systems were not consistent. Beginning with the 2013 edition of NFPA 17A, a new and improved outline of 11 minimum requirements to approve installations was published to standardize acceptance testing of a wet chemical extinguishing system.

Prior to the 2013 edition of NFPA 17A, a test was required to be conducted by trained personnel as required by the manufacturer’s listed installation and maintenance manual. The test was used to determine if the system was properly installed and functioned as intended. An approval test, where required by the AHJ, mandated that a discharge test, in accordance with the manufacturer’s listed installation manual, be conducted to verify that the system is properly installed and functional. Lastly, the owner had to be provided with a copy of the manufacturer’s listed installation and maintenance manual or listed owner’s manual.

There was a lot of confusion around the types of tests that needed to be conducted. Specifically, many believed the discharge test was to be conducted with the wet chemical or substituted with water, and this was simply not the case. Although associated annex language (explanatory material) clarified when this test was required, the system manufacturer should be contacted for detailed functional discharge procedures, and that water was not endorsed by all of the wet chemical system manufacturers, many users of the standard either did not see this annex language or chose not to apply it.

It is important to remember that local authorities can require testing and documentation beyond what is required by the manufacturer’s provisions or any NFPA code or standard. However, most of the misunderstanding was not due to local authorities having additional provisions.

In preparation for the 2013 edition of NFPA 17A, the Technical Committee developed a task group to determine the essential approval installation requirements to align with the scope of NFPA 17A. Recognizing that each manufacturer has a specific, unique procedure for testing their system, the task group reviewed several manufacturers’ installation and maintenance manuals. Interestingly, no manufacturers required discharge testing. In fact, the task group only found manufacturers advising against a discharge test. This new information provided support to remove the discharge test from the standard, but raised the question: What minimum requirements are necessary for examination during assembly and installation approval to assure safety and functionality of wet chemical extinguishing systems?

First requirements

As previously stated, wet chemical extinguishing systems are proprietary, pre-engineered systems, and therefore the first three out of the new 11 requirements include complying with the manufacturer’s design, installation and maintenance manual.

For example, during the approval of installation, the installing contractor and authority having jurisdiction will verify appliances, hoods and ducts are properly protected with nozzles and positioned in accordance with the manufacturer’s design, installation and maintenance manual. For mechanical components of the system, nozzle sizes and pipe sizes are verified to be in accordance with the manufacturer’s design installation, and maintenance manual. Lastly, the team will verify the piping supports are securely fastened and appliances are installed in the same location, as approved by the system design, and are in compliance with the manufacturer’s instructions.

The fourth provision on the list is to complete the piping integrity test. The intent of this test is to verify that flow is continuous and that the piping and nozzles are reasonably unobstructed. Piping is not required to be hydrostatically tested. So how does one conduct a piping integrity test? NFPA 17A outlines these four steps:

• All the piping is to be physically checked for tightness.
• A test using nitrogen or dry air is to be performed on the piping network at a pressure not exceeding the normal operating pressure of the extinguishing system.
• The test is required to verify that nitrogen or dry air has discharged out of each nozzle of the system.
• The method of verification is up to the AHJ.

What are appropriate methods of verification? That depends on your AHJ. However, some of the methods used in the industry include puff tests, balloon tests, bag tests and flow tests. The puff test is conducted with the caps on the discharge nozzles, and uses air or nitrogen to enter the system. Once the air or nitrogen is introduced into the system and the caps on the discharge nozzles pop off, it is believed that the system is reasonably unobstructed. Balloon tests are conducted by placing balloons over each discharge nozzle and introducing dry air or nitrogen into the system at low pressure. The concept is that once the balloons inflate with the dry air or nitrogen, there is evidence that the system is reasonably unobstructed.

The bag test includes discharging a liquid at system pressure through the system piping with a bag attached at each nozzle. The idea is that once the liquid discharges from each nozzle, the system is reasonably unobstructed. Flow tests are similar to bag tests except that these tests are conducted with the plastic hose attached to each discharge nozzle and placed into a container that will collect the liquid and show the quantity of liquid discharged.

The method of verification to conduct the piping integrity test is up to the AHJ. A common theme from reviewing the different test methods is that a “successful test” is not definitive that the correct amount of agent will discharge in an actual event. Remember, these are pre-engineered systems that have been calculated for the correct pipe size, elevation change and pressure drops. Discharge testing is included as a part of the listing process for pre-engineered systems. The goal of the piping integrity test is to verify that flow is continuous and that the piping and nozzles are reasonably unobstructed.

Final six requirements

Once this test is completed, the final six requirements mandated for approval of installations in NFPA 17A are straight forward.

Devices need to be labeled with proper designations and instructions. If you have a building alarm system, the installing contractor and AHJ will verify that the alarm-sounding or notification devices and remote annunciation devices are functional. All pull stations need to be readily accessible and accurately identified. System operational tests, including functional tests of the automatic detection system, manual release devices, gas shutoff, shutoff of makeup air supplied internally to a hood, and the electrical power shutdown, are to be performed in accordance with the manufacturer’s design, installation and maintenance manual. If releasing control panels are provided, it is critical to make sure the panel is accessible and restricted from unauthorized personnel. In addition, the installing contractor and AHJ will need to verify that the panel is connected to a dedicated circuit that is labeled properly.

One of the easiest but most missed “sanity checks” when it comes to any testing is to make sure the system is returned to its operational condition. This includes verification that each extinguishing agent storage container is reconnected and the system is returned to its operational condition. If the system is connected to an alarm-receiving office, the alarm-receiving office and all concerned personnel at the end user’s facility need to be notified that the fire system test is complete and the system has returned to full-service operational condition as well.

One of the final steps in the approval of installation procedure required in NFPA 17A is for the installing contractor to complete and sign an acceptance test report acceptable to the AHJ. Lastly, the owner is provided with a copy of the manufacturer’s design, installation and maintenance manual or the owner’s manual, as ultimately the owner is responsible for the wet chemical extinguishing system.

The Technical Committee responsible for NFPA 17A developed these 11 minimum requirements to provide a comprehensive procedure for the approval of installation of wet chemical extinguishing systems to assure safety and functionality.

The public comment closing date for the 2021 edition of NFPA 17A was May 8. Visit www.nfpa.org/17A for more information.