Exploring the requirements for fire pump retrofits
- Learn about the implications of codes and standards that fire protection engineers and other consultants should consider when retrofitting a fire pump into an existing building and fire protection system.
- Understand that cost impacts for fire pump retrofit extend beyond the cost of the fire pump equipment.
- Learn how to identify major architectural and electrical costs, early in the process of a fire pump retrofit project.
Retrofitting a new fire pump in an existing building to supply an existing fire sprinkler system can pose several challenges in regard to apparent costs, such as the fire pump equipment, and not so apparent costs, such as electrical equipment upgrades, architectural changes, etc. A fire protection contractor can frequently provide a rapid and accurate cost estimate to procure and install the fire pump, pump controller, and piping. It is the responsibility of the consulting engineer to consider and identify the hidden costs of numerous NFPA 20: Standard for the Installation of Stationary Pumps for Fire Protection requirements that need special consideration early in the project to ensure a successful installation.
NFPA 20 is the primary standard for installing fire pumps. This standard is typically used in conjunction with the local fire codes and other NFPA standards as adopted by the authority having jurisdiction (AHJ). When a retrofit installation of a fire pump is to be completed, the consulting engineer will be expected to deliver an installation that not only complies with NFPA 20 and the other adopted codes, but also functions seamlessly with the existing building systems.
Retrofit fire pump installations
Retrofit fire pump installations typically become necessary when a change in a building or a change in the use of the building creates an increased demand on the fire protection system. A frequent example is when a new warehouse operation moves into an existing space that is not provided with a sufficient sprinkler system to protect the new commodity that will be stored. The addition of a fire pump may be considered to provide additional pressure to properly protect the new storage configuration. Alternatively, a new fire pump may be necessary to bolster an existing water supply to accommodate the expansion of an existing building. In yet other cases, a fire pump may be required to offset the degradation of an existing water supply.
Regardless of the primary reason for a retrofit installation of a fire pump, an existing building will also likely require some degree of modification to provide a space with the NFPA 20-required features to house the new fire pump equipment. The financial and functional costs of these modifications are often neglected at the outset, when the decision is made to install a fire pump.
For example, if an electric fire pump is to be provided, significant modifications may be required to the building’s electrical system to support the new equipment. In some circumstances, the effort and cost of these building modifications may exceed the cost and effort to install the actual fire pump and piping equipment. Without carefully considering these factors, the cost and level of effort to provide a new fire pump in an existing building may be significantly underestimated.
A renovation of an airline’s flight-simulator facility in a large metropolitan area was recently completed. After evaluating the existing fire protection systems, it was determined that the space housing the flight simulators required additional protection to meet modern code requirements. Several design options were investigated during an initial basis-of-design assessment phase. Options considered included various configurations of clean agent, water-mist, and sprinkler systems. Considering each option, the designers had to weigh cost factors including equipment costs, building-modification
costs, building-operation impact costs, and existing system interface costs. While clean agent and water-mist systems had some advantages (minimal building-modification costs, minimal backup-power demands), the decision was ultimately made to increase the water density provided by the existing sprinkler system.
The existing water supply for the building’s fire protection systems relied solely on the pressure provided by the underground water supply from the city. Hydraulic calculations showed that the existing overhead piping and sprinklers would be sufficient to deliver the increased sprinkler density with the additional pressure boost provided by installing a new fire pump. Alternative fire sprinkler system-modification options could have included upsizing existing piping and replacing sprinklers with larger orifice heads. The fire pump option was selected, in part, because it would have the smallest impact on the operation of the flight simulators, which were in nearly continuous operation.
Fire pump rooms
Once it is determined that a fire pump is necessary, one of the first challenges will be identifying adequate space for the fire pump location. In a new building, this is simply a matter of informing the architect and ensuring that they providea room of adequate size for the pump and supporting equipment. In an existing building, allocating space can be a considerable challenge. The process begins with selecting an appropriate pump type-horizontal split case, vertical inline, etc.-and then obtaining the dimensions of the fire pump that suits the waterflow, pressure, and electrical (if applicable) demand requirements. Note, if the project intends to allow for open bidding, then the designer must anticipate a range of pump manufacturers and, therefore, plan for pump dimensions accordingly. Using the identified dimensions, a concrete pad should be specified for mounting the pump above the floor. The designer must then consider the space required for all the necessary pump piping and trim (NFPA 20-2016, Section 18.104.22.168.7).
When dealing with a limited space, it’s important for the designer to fully lay out the system to determine if all the appurtenances can be accommodated, along with adequate clearance for future maintenance. For example, the Department of Defense’s Unified Facilities Criteria (UFC) 3-600-01 Fire Protection Engineering for Facilities (Change 2, March 2018), Paragraph 9-7.10.1, requires a minimum of 3 ft of clearance in front of all piping in addition to 6 in. of clearance behind piping. A similar strategy should be used for all installations, regardless of whether the UFC is applied.
Space will also need to be allocated for the fire pump controller panel and the pressure-maintenance (jockey) pump controller panel. NFPA 20-2016, Sections 10.2.1 and 12.2.1, require controllers to be located as close as practical to the pump engine. When an electric-motor fire pump is used, space may need to be allocated for an automatic transfer switch if standby power is required. Section 12.2.4 refers to NFPA 70: National Electrical Code (2014) (NEC) Article 110, which requires electrical-panel clearances based on equipment voltage, and at a minimum, adequate space to permit a 90-deg. opening for the panel door(s).
If a diesel engine-driven fire pump is selected, then space will be required for the fuel tank, which must be located indoors in locations subject to freezing temperatures (NFPA 20-2016, Section 11.4.2). Space must be provisioned for the engine-starter equipment; dual batteries for electric starting (typical), a hydraulic accumulator for hydraulic starting, or an air compressor for air starting. Ideally, the fire pump room should be located along an exterior wall to accommodate supply- and exhaust-air venting. This is particularly important in multistory buildings where venting to the roof becomes challenging. NFPA 20-2016, Section 22.214.171.124, requires exhaust venting to be as short as possible.
In addition to the space demands, there are several pump-room requirements that can be especially challenging in an existing building. NFPA 20-2016, Section 4.13.7, requires the floor to be sloped to drain water away from critical equipment, such as the pump, driver, controller, etc. In addition, a floor drain is required to direct drainage to a frost-free location. Section 126.96.36.199 requires the pump to be located in a room that is separated from the building by either a 1-hour fire barrier or at a 50-ft distance. If the pump is serving a high-rise, the pump room is unsprinklered, or the protected building is not fully sprinklered, then the pump must be separated either by a 2-hour fire barrier or 50 ft of separation distance. If the fire pump room cannot be located along an exterior wall with direct access from the outside, then it must be accessible from an exit enclosure or a fire-resistance-rated passageway of equal fire resistance to the pump room separation (Section 4.13.2).
NFPA 20-2016, Section 188.8.131.52.5, restricts the equipment that can be located inside the fire pump room. Specifically, only equipment essential to the fire pump may be located in the pump room. The room cannot be used for storage, and it cannot contain other systems equipment, such as unrelated electrical panels, boilers, or mechanical HVAC equipment that serves other areas of the building, etc. The only extraneous equipment permitted in the pump room is domestic-water-supply distribution equipment per Section 184.108.40.206.6.
For the flight-simulator fire pump project that was previously mentioned, the building’s basement consisted primarily of a large, narrow, rectangular mechanical room housing hydraulic power units used for providing motion for the flight simulators. Fortunately, an approximately 8×15-ft clear area without existing equipment was identified within the mechanical room to house the new fire pump. The clear area was located within 15 ft of the existing city fire water-line point of entry and immediately adjacent to an existing exit door that led to the ground-level grade via an exterior stairway. Despite the good fortune of finding adequate clear space, architectural modifications were still necessary to separate the pump room from adjacent spaces and unrelated equipment, as well as to provide direct access from the exterior. One-hour fire-rated walls were constructed to separate the new fire pump room from the existing mechanical room. To provide NFPA 20-compliant pump room access and maintain the existing building exit, a vestibule was constructed at the existing exit door with access from both areas. The vestibule was erected using 1-hour fire-rated construction typical to the pump room. A new floor drain was also required to be installed in the room to meet NFPA requirements.
Fire pump room challenges in existing buildings
Due to the challenges of creating a fire pump room in an existing building, the designer may prefer to have a separate pump-house building constructed. In this case, the designer will need to keep in mind that locations subject to freezing temperatures will require additional precautions. The pump house will need to be heated and the pump-discharge piping will need to be routed underground to the sprinkler-protected building unless other freeze-protection methods are used.
Interior pump rooms and exterior pump houses are required to be provided with a heating system that maintains the temperature above a minimum of 40°F (NFPA 20-2016, Section 220.127.116.11) or at the minimum temperature recommended by the pump engine manufacturer for diesel engine-driven pumps (Section 11.6.5). Pump rooms and pump houses will also require normal lighting and emergency lighting (Sections 4.13.4 and 4.13.5).
Since the flight-simulator fire pump project constructed a new dedicated pump room, a thermostat-controlled fan, ductwork, and associated fire dampers had to be installed to provide heat and air circulation from the mechanical room to the fire pump room. Although there were notable costs associated with constructing a fire pump room and providing new HVAC equipment, the design team and owner considered the savings in building-operation time outweighed these costs.
Water supply for fire pumps
If an existing-building water supply is to be used to supply a new fire pump installation, the water supply will require an evaluation for the additional demand posed by the pump. Ideally, the water supply for a fire pump would be capable of operating the fire pump at 150% of its rated capacity while maintaining the minimum-allowable suction pressure. NFPA 20 allows the suction-gauge pressure to drop to 0 psi at the pump’s suction flange at 150% of the pump’s rated flow. Operating the fire pump at 150% of its rated capacity allows for full acceptance and annual testing of the pump’s performance. Additionally, if the pump is to be supplied from a city water main, the local water authority typically requires a minimum positive pressure of at least 20 psi to be maintained in the underground-supply piping at all times. While the original design of the existing water-supply piping may have been adequate to support the building’s existing fire protection systems, the friction loss experienced when supplying a fire pump during a fire incident or during testing may drop the pressure at the suction flange or the underground-supply piping to below the minimums that were previously discussed. Negative suction pressure may cause pump cavitation and reduced pump performance.
NFPA 20-2016, Sections 4.6.2 and 18.104.22.168, provide alternative design approaches for situations where suction pressure is inadequate. Alternatively, the existing underground water supply may have to be supplemented or replaced to support the new pump installation.
During the initial basis-of-design assessment phase for the flight-simulator fire pump project, high-level hydraulic calculations were performed by the consultant engineer to verify that the supply had sufficient flow and pressure to allow the proposed fire pump to operate at 150% of its rated capacity. This required obtaining recent underground waterflow information from the local water utility and confirmation of the existing underground water main routing and size. This early assessment confirmed that the underground water supply would not require a modification or upgrade to support the proposed fire pump installation.
Interface with existing fire protection systems
If the new fire pump is being installed to supply existing sprinkler or standpipe systems, consider how the new fire pump will interface with the existing system piping and water supply.
The new fire pump would ideally be physically located adjacent to the existing pipe network at a point upstream from the individual fire protection system risers and hose valves. If the fire pump is to be located remotely from the existing fire protection water-supply piping, large amounts of bulk-supply piping may need to be installed to connect the pump discharge to the existing fire protection system risers. Additional bulk-supply piping may also be needed if the remotely located pump is to use the building’s existing underground water supply. Existing valves and backflow-prevention devices may have to be included in the project scope for replacement and/or relocation to ensure sufficient pipe distance is provided from the new fire pump. NFPA 20-2016, Section 22.214.171.124, requires that no control valves other than listed outside screw and yoke (OS&Y) valves be installed in the suction pipe within 50 ft of the pump suction flange. Section 4.28.3 requires that a minimum distance of 10 pipe diameters be provided between the pump suction flange and any check valves or backflow-prevention assemblies.
The existing fire department connection (FDC) may also require modification. NFPA 13-2016: Standard for the Installation of Sprinkler Systems, Section 126.96.36.199.8, prohibits fire department connections from connecting on the suction side of fire pumps. Other NFPA standards for water-based fire protection systems have similar restrictions. If the existing FDC is connected to the piping network upstream of the new fire pump, additional piping may be required to reconnect the fire department connection to the discharge side of the fire pump. Alternatively, the FDC may be entirely relocated. Existing remote fire department connections pose an additional challenge since they may tie into the existing underground water supply prior to entering the building. This type of FDC arrangement may necessitate underground pipe work to provide an NFPA 20-compliant final installation.
An initial survey of the flight-simulator building revealed the existence of two independent water-supply mains to the building. The fire pump’s location was adjacent to only one of the water-supply entry points. This configuration presented a problem where a new bulk main would need to interconnect the secondary water main to the suction side of the fire pump. Installing approximately 500 ft of 8-in. bulk main would have added a significant cost to the project. After discussing with the building owner and AHJ, it was discovered that the secondary water-supply main was previously installed as a temporary water supply and was not intended (nor sized) to supply the full demand of the buildings’ fire protection systems. It was also confirmed that there was no local code requiring redundant water supplies for the building. Based on this analysis and discussion with the stakeholders, it was determined that the secondary water-supply main could be abandoned, thus negating the need for any new bulk piping for interconnection of the two water supplies to the fire pump. Furthermore, the existing FDC was tied into the piping network at a location downstream of the intended fire pump tie-in.
NFPA 20-2016, Section 10.4.7, requires that fire pump alarms and signals be transmitted to a point of constant attendance when the pump room itself is not constantly attended. In most cases, this implies that a fire alarm reporting system will be necessary. If the building has an existing fire alarm system, several additional devices will need to be provided to monitor the status reported by the fire pump controller as well as the new control valves. If the building is not already provided with a fire alarm system, then at a minimum, a dedicated-function fire alarm system (NFPA 72-2016: National Fire Alarm and Signaling Code, Section 188.8.131.52) may need to be installed to provide supervision for the fire pump.
Based on the typical fire pump, the designer should anticipate six or more monitor modules to monitor the status of valve-tamper switches (note that the two valves on the jockey-pump loop do not need to be monitored) and four or more additional monitor modules to monitor the status of the fire pump controller.
The flight-simulator building was already provided with a building fire alarm reporting system. Therefore, costs were limited to the addition of several monitor modules. During the initial survey, it was verified that the fire alarm system had adequate spare capacity to accommodate these additional devices.
Interface with existing electrical systems
If an electric-drive pump is selected for the building, then the electrical service will need to be arranged to meet one of the following requirements (NFPA 20-2016, Section 9.2.2):
- Service connection dedicated to the fire pump installation.
- Onsite power-production facility connection dedicated to the fire pump installation.
- Dedicated feeder connection derived directly from the dedicated service to the fire pump installation.
- Feeder connection where all conditions of NFPA 20-2016, Section 9.2.2(4), are met.
- Dedicated transformer connection directly from the service, meeting the requirements of NEC, Article 695.
In each of the five requirements listed above, anticipate that some modification to the existing electrical system will be necessary to provide a dedicated connection to the fire pump.
Furthermore, an electric-motor pump will need to be provided with an alternate source of power, unless: The building is not a high-rise and the fire department apparatus can deliver the system demand, a backup fire pump with an independent power source is provided, or the primary power source can be considered reliable (NFPA 20-2016, Section 9.3.3). The Annex to Section 9.3.2 defines a reliable power source as one that has not experienced a power loss greater than 10 hours in the previous year, and where routine outages are not experienced due to generation or transmission in the vicinity of the protected facility. Additionally, a reliable normal power source may not serve the protected facility via overhead lines. Finally, the reliable normal power source must be designed such that power disconnection and activated overcurrent protection may only occur at the fire pump controller. If the electrical service is determined to be reliable, it is highly recommended that the engineer obtain a letter from the power utility authority stating compliance with the aforementioned criteria.
The requirement for an alternate source of power for the new fire pump may dictate the installation of a new emergency generator. The installation of this new equipment will contribute additional challenges to the project. In particular, space allocation will once again become problematic and a fuel-supply source, either by refillable fuel storage or a utility connection, will need to be identified.
For the flight-simulator fire pump project, primary power was provided to the facility via an existing utility-owned high-voltage transformer located on the property. A preliminary assessment determined that the existing transformer would have adequate capacity for the load imposed by the new fire pump. The installation of a utility-provided secondary-connection cabinet permitted a new power feed to be connected from the pump directly to the transformer, independent of the primary building feed.
A review of the applicable fire and building codes also confirmed that an alternate source of power would not be required. This may have posed a significant cost increase, as it was determined that the building’s existing backup generators did not possess adequate capacity to serve a fire pump.
The flight-simulator fire pump project was considered a success. The engineers involved were able to inform the project stakeholders of the necessary discipline coordination and costs early in the project. This thorough, early assessment ensured that all stakeholders were able to make an informed decision to install the fire pump while being code-compliant and prevent unpleasant surprises late in the project.