NEC Rules for Fire PumpsApr 16, 2013Mike Holt|Electrical Construction and Maintenance NEC Rules for Fire Pumps SIDEBAR: Power Source(s) for Electric Motor-Driven Fire PumpsUnderstanding the circuit protection requirements of Art. 695 and why theyre different from other parts of the NECAdvertisementThe general philosophy behind most Code requirements is to provide circuit protection that will shut down equipment before the supply conductors become overloaded, overheated, and damaged. But Art. 695 is based on a different philosophy: The fire pump motor must run, regardless of the risk to the conductors.A fire pump supplies water to a facilitys fire protection piping. If the pump doesnt run, not only will those conductors be damaged, but the entire facility will also be in danger of burning down. Consequently, the many requirements of Art. 695 aim to keep the pump running.Obviously, the pump is more likely to keep running if its location minimizes exposure to fire, and doing so is an NEC requirement. This doesnt conflict with other requirements, but many Art. 695 requirements do. For example, contrary to what other articles require, the disconnect must be lockable in the closed position [695.4(B)(3)(a)(2)].According to the scope statement of Art. 695, it covers the installation of the fire pump supply and controls. It doesnt cover the jockey pumps or the internal wiring of the system (Photo).What is a jockey pump?A jockey pump, or a pressure-maintenance pump, is a small apparatus that works together with afire pumpas part of a fire-protection sprinkler system. It is designed to keep the pressure in the system elevated to a specific level when the system is not in use, so that the fire pump doesn't have to run all the time and the system doesn't go off randomly. It can also help prevent the system from damage when a fire happens and water rushes into the pipes. These devices consist of a three-part assembly. In many places, there are governmental guidelines and recommendations for installing these devices to make sure they work properly.How it WorksTo understand how a jockey pump works, it's important to understand how a fire sprinkler system works. Sprinkler systems consist of pipes with pressurized water in them and heads that are designed to open when they reach a certain temperature. When the heads open, thewater pressurein the pipes drops, since water is flowing out of them. When this happens, a large device called a fire pump starts to send more water through the pipes so that the system can continue to put out the fire.

The purpose of the jockey pump is to keep the water pressure in the pipes within a specific range when there's not a fire, so that the sprinklers won't go off randomly. Since pipes leak, over time, the water pressure inside them automatically goes down. The jockey pump senses this, and then fills them back up to normal pressure. If a fire happens and the pressure drops dramatically, the jockey pump won't be able to keep up, and the drop in pressure will trigger the large fire pump to start sending water.Secondarily, this pump prevents sprinkler systems from being damaged when the fire pump begins sending water. If a system does not have a jockey pump keeping it pressurized, it may have a relatively low pressure. When the fire pump starts sending highly pressurized water through the pipes, the sudden change in pressure can damage or destroy the system.AssemblyAll jockey pumps consist of a pump, a motor, and a controller. The two main types of pumps available are centrifugal and regenerativeturbinepumps. Both have their pros and cons: the centrifugal type is often less energy-efficient, but it needs less maintenance than a regenerative turbine one. Likewise, a regenerativeturbine pumpcan create a lot of pressure with very little power, but it can make the system too pressurized, and needs a lot of maintenance. Which type is best for a system also depends on the size of the system, with centrifugal pumps often being preferred for smaller systems, since they sometimes create less pressure.The type of motor used also depends largely on the size of the system. The two main choices for jockey pump motors are single-phase and three-phase. Both work largely the same way, though single phase motors are typically used for smaller, lower pressure systems since they're not as powerful. Controllers can also be either single-phase or three-phase, and differ primarily in the complexity of their assembly.

RequirementsMany places have governmental standards for installing and maintaining jockey pumps. In the US, the National Fire Protection Association's (NFPA) guidelines are the standard. These include things such as the recommended power for a jockey pump in relation to a system's size, how long it can take to repressurize the system, and the pressure that it needs to maintain.

The rules covering the installation of electric power sources and interconnecting circuits for switching and control equipment dedicated to fire pump drivers are very specific.Power sourcesWith the 2011 NEC, the power requirements found in Art. 695 have changed extensively (seeSIDEBAR: Power Source(s) for Electric Motor-Driven Fire Pumps). However, as with previous NEC editions, you must supply power from a reliable source. This source must be able to carry the locked-rotor current of the fire pump motor(s) and pressure maintenance pump motors, plus the full-load current of associated fire pump equipment [695.3(A)].Electric motor-driven fire pumps must have a reliable source of power, which is subject to the approval of the AHJ. It needs to be one or more of the following: A separate electric utility service [695.3(A)(1)]. A connection located ahead of (but not within) the service disconnecting means [695.3(A)(1)]. An on-site power supply, such as a generator, located and protected to minimize damage by fire [695.3(A)(2)]. A dedicated feeder derived from a service connection in accordance with 695.3(A)(1) [695.3(A)(3)].If reliable power cant be obtained from one of these sources, then it must be supplied by one of the following multiple sources [695.3(B)]:1. Individual sources. An approved combination of two or more of the sources from 695.3(A).2. Individual source and on-site standby generator. An approved combination of one of the sources in 695.3(A) and an on-site standby generator.Exception to 695.3(B)(1) and (B)(2): An alternate source of power isnt required where a back-up engine-driven or back-up steam turbine-driven fire pump is installed.If you have: Amulti-building, campus-style installation where the sources just discussed arent practicable, follow the requirements of 695.3(C). An on-site standby generator as an alternate source, follow the requirements of 695.3(D).Arrange multiple sources so that a fire at one source wont cause an interruption at the other source [695.3(E)]. Phase converters are not permitted for a fire pump service [695.3(F)].ContinuityCircuits that supply electric motor-driven fire pumps must be supervised from inadvertent disconnection whether the conductors connect directly or through a disconnecting means and overcurrent device [695.4].If you have a direct connection, the supply conductors must directly connect the power source either to a listed fire pump controller or to a listed combination fire pump controller and power transfer switch [695.4(A)].If you connect through a disconnect and an overcurrent protective device (OCPD), then you can use a single disconnecting means and associated OCPD(s) between the fire pump power source and one of the following [695.4(B)(1)]:1. Listed fire pump controller.2. Listed fire pump power transfer switch.3. Listed combination fire pump controller and power transfer switch.Select or set the OCPD to carry indefinitely the sum of the locked-rotor current of the fire pump and pressure maintenance pump motor(s), and 100% of the ampere rating of the fire pumps accessory equipment.If the locked-rotor current value doesnt correspond to a standard OCPD size, then use the next standard OCPD size per 240.6 (Fig. 1). The requirement to carry the locked-rotor current indefinitely doesnt apply to fire pump motor conductors [695.4(B)(2)(a)].

Fig. 1. If the locked-rotor current doesnt correspond to a standard overcurrent protective device (OCPD), then use the next size up per 240.6. In this example, the locked rotor current is shown as 404A. Therefore, you should use a 450A OCPD.Disconnecting meansThe disconnecting means for the normal power source must be [695.4(B)(3)]: Identified as suitable for use as service equipment. Lockable in the closed position. Not located within equipment that feeds loads other than the fire pump. Located sufficiently remote from other building or other fire pump source disconnecting means. Marked Fire Pump Disconnecting Means. The letters must be at least 1 in. high. People must be able to see them without opening enclosure doors or covers [695.4(B)(3)(c)].What if an on-site generator is the alternate power source? In that case, install its disconnect per 700.10(B)(5) for emergency circuits, and ensure the disconnect can be locked in the closed position [695.4(B)(3)(a)(2)].TransformersIf a transformer supplies an electric fire pump motor, size it at least 125% of the sum of the fire pump and pressure maintenance pump(s) motor loads, and 100% of the ampere rating of the fire pumps accessory equipment [695.5(A)].Size the primary OCPD to carry indefinitely the sum of the locked-rotor current of the fire pump and pressure maintenance pump motor(s), and 100% of the ampere rating of the fire pumps accessory equipment. The requirement to carry the locked-rotor currents indefinitely does not apply to fire pump motor conductors. Secondary overcurrent protection is not permitted [695.5(B)].Power wiringService conductors and conductors supplied by on-site power production facilities must be physically routed outside buildings [695.6]. Install them per Art. 230. If these conductors cannot be routed outside of buildings, then encase them in 2 in. of concrete or brick [230.6(1) or (2)].Keep fire pump supply conductors entirely independent of all other wiring. They can supply only those loads directly associated with the fire pump system. Make sure they are protected from potential damage by fire, structural failure, or operational accident [695.6(A)(2)]. You can route fire pump conductors through a building by one of the following methods [695.6(A)(2)(d)]: Encase them in a minimum 2 in. of concrete. Run them within an enclosed construction dedicated to the fire pump circuit(s) and having a minimum of a 2-hr fire-resistive rating. Use a listed electrical circuit protective system protected by a fire-rated assembly listed to achieve a minimum fire rating of 2 hr and dedicated to the fire pump circuit(s).

Fig. 2. Branch circuit conductors to a single fire pump motor must have a rating of not less than 125% of the motor FLC as listed in Tables 430.248 or 430.250.Conductors supplying only a fire pump motor must have a minimum ampacity of at least 125% of the motor full-load current rating as required by 430.22 [695.6(B)(2)], as shown inFig. 2. If these conductors also supply related equipment, such as another fire pump motor, pressure maintenance pumps, and associated fire pump accessory equipment, they must have a minimum ampacity of at least 125% of the sum of the fire pump motors and pressure maintenance motors full-load currents and 100% of the associated fire pump accessory equipment [695.6(B)(1)].Wiring from the fire pump controller to the fire pump motor (not installed through a building, as covered in 695.6(B)) must be in rigid metal conduit, intermediate metal conduit, electrical metallic tubing, liquidtight flexible metal conduit, liquidtight flexible nonmetallic conduit Type B, listed Type MC cable with an impervious covering, or Type MI cable [695.6(D)]. This requirement also applies to the control wiring [695.14(E)].The voltage at the line terminals of the fire pump controller, when the motor starts (locked-rotor current), must not drop more than 15% below the controllers rated voltage [695.7(A)].In addition, the voltage at the motor terminals must not drop more than 5% below the voltage rating of the motor when the motor operates at 115% of the fire pump full-load current rating [695.7(B)].Regardless of the voltage drop calculations, size the branch circuit conductors no smaller than required by [695.6(B)].GFCIGround-fault protection of equipment is not allowed on fire pump equipment [695.6(G)]. The NEC doesnt prohibit you from installing GFCI-protected receptacles in a fire pump location for portable equipment or other outlets required by the NEC to be GFCI protected.In summaryBecause the circuit protection requirements of Art. 695 differ from and philosophically conflict with the NECs other circuit protection requirements, correct application can be confusing. The central question to answer when installing fire pumps and related equipment is, How do I make sure the pump runs no matter what?Remember, the fire pump must be kept in service, even if doing so damages or destroys the pump. Its better to run the pump until its windings melt than to save the fire pump and lose the facility. The intent of Art. 695 is to save the facility.SIDEBAR: Power Source(s) for Electric Motor-Driven Fire Pumps