Electric Fire Pump: Power Supply, Controller, Starting and Testing

1. Control panel under the Brazilian rules and controller under NFPA 20

Under São Paulo IT 22, Goiás NT 22 and NBR 13714, the control panel for motor protection and automatic starting is selected by the motor power in CV (metric horsepower). It sits as close as possible to the motor, protected against water splashes and dust, and is supplied with dimensional drawings, layout, wiring diagram, terminal strip, internal wiring diagram and a list of the materials used.

Wires are ferruled to match the diagram, and the audible alarm, once silenced by a push button, sounds again when a new event occurs (IT 22, C.2.17 and C.2.18.3 to C.2.18.6; NT 22, C.4.14 and C.4.16 to C.4.19; NBR 13714, B.2.11 and B.2.13 to B.2.16).

The electric pump’s signal panel has a push button to start the pump manually and visual and audible signals for, at least, panel energized, pump running, phase failure and loss of power to the starting circuit (IT 22 and NT 22, C.1.16 and C.1.16.1; NBR 13714, B.1.14 and B.1.14.1). NBR 13714 requires this panel where there is permanent surveillance. The jockey pump may have only a visual pump-running signal (IT 22, C.2.14; NT 22, C.4.11; NBR 13714, B.2.8).

Under NFPA 20, the controller is the group of devices that governs, in some predetermined manner, the starting and stopping of the pump driver and monitors and signals the status and condition of the fire pump unit (3.3.24).

The standard’s annex explains that a controller and transfer switch “suitable for use” have been prototype tested and have shown their short-circuit withstand and interrupting capacity at the short-circuit current and voltage available at their line terminals, and it refers to UL 218, the fire pump controller standard, UL 508 and UL 1008.

The same annex recommends a short-circuit study to establish the current available at the controller and notes that, after a high fault current, the controller and transfer switch might need inspection or repair.

By the NFPA 20 definition, listed equipment is included in a list published by an organization acceptable to the authority having jurisdiction, which evaluates the product, maintains periodic inspection of production and states that it meets appropriate designated standards or has been tested and found suitable for a specified purpose (3.2.3). A design that conforms to a standard is not a listed product, and the Brazilian rules cited here do not require a listed panel.

Under NFPA 20, even the jockey pump controller is listed, although it need not be listed for fire pump service (4.27.8).

FB Bombas builds the FBFS electric set with an FBCN main pump, a three-phase electric motor, a jockey pump and automatic starting by pressure switch when network pressure drops. Pump, motor, panel and interfaces are defined by the hydraulic demand and the power supply specified in the design. State the contract standard in your enquiry, because it determines whether the panel and the motor must be listed.

2. Starting: magnetic starter, acceleration within 10 s and voltage drop

In the three Brazilian rules, motor starting follows the recommendations of NBR 5410 or the local utility, the starting system is magnetic and the motor acceleration period does not exceed 10 s (IT 22, C.2.18 to C.2.18.2; NT 22, C.4.15 to C.4.15.2; NBR 13714, B.2.12 to B.2.12.2). NBR 13714 also requires motor protection in accordance with NBR 5410 (B.2.17). After starting, the pump reaches full operating condition in approximately 30 s (IT 22, C.1.9; NT 22, C.1.10; NBR 13714, B.1.9).

None of the three sets the starting method beyond requiring a magnetic starter: direct-on-line, star-delta or another method depends on the motor, the power supply and the recommendations of NBR 5410 or the utility. Choose the method with data for the network, the generator where there is one and the other loads on the circuit, and check that the motor accelerates within the 10 s.

Where the contract adopts NFPA 20, the voltage at the controller line terminals does not drop more than 15% below the controller rated voltage while the motor starts, and the voltage at the contactor load terminals does not drop more than 5% below the motor rated voltage with the motor at 115% of full-load current (9.4.1 and 9.4.4). The starting limit does not apply to emergency-run mechanical starting, provided a successful start can be demonstrated on the standby generator (9.4.2).

The standard also prohibits phase converters on the pump supply, ground-fault interruption that opens the motor circuit below the current needed to protect the conductors and any arc-fault interruption device in the pump’s power and control circuits (9.1.7, 9.1.8.1 and 9.1.8.2).

Under NFPA 20, the motor horsepower is such that the current in any phase, under any condition of pump load and voltage unbalance, does not exceed the full-load current multiplied by the service factor. In rejecting a proposal to limit this check to 175% of rated flow, the standard’s committee stated that it requires non-overloading over the entire pump curve and that many pumps can perform past 175% of rated flow.

In the NFPA 25 no-flow test, observe the time for the motor to reach full speed and, with reduced-voltage or reduced-current starting, record the time the controller is on the first step.

3. Independent power supply, generator and transfer switch

Under the Brazilian rules, the fire pump power supply is independent of the general building load, so that switching off the building’s power does not affect the motor.

The building’s service entrance is sized for the fire pumps running together with the other electrical loads at full load, the supply switches carry the marking “ALIMENTAÇÃO DA BOMBA DE INCÊNDIO – NÃO DESLIGUE” (fire pump supply – do not switch off) and the motor wiring inside the area protected by the hydrant system is protected against mechanical and chemical damage, fire and moisture (IT 22, C.2.7 and C.2.10 to C.2.12; NT 22, C.4.4 and C.4.7 to C.4.9; NBR 13714, B.2.1, B.2.3, B.2.5 and B.2.6).

NBR 13714 also requires an electrical supervision system that detects any fault in the building’s electrical installations that could interfere with pump operation (B.2.4).

When utility power fails, the three rules allow the electric pump to be fed by a diesel generator (IT 22, C.2.9, which refers to C.2.8; NT 22, C.4.6; NBR 13714, B.2.2, which refers to the service entrance requirement of B.2.3).

In a facility supplied at medium voltage with a safety generator, IT 22 and NT 22 allow the supply to be connected ahead of the main low-voltage switch, with an exclusive utility supply and redundancy from the safety generator (C.2.8 and C.4.5). In NBR 13714 system acceptance, the automatic start of the pump fed by the emergency generator set, specified to come into operation or readiness if power to the main motor fails, is also tested (C.1.3.1).

In Goiás, NT 22 sets the minimum number of pumps by function: a booster arrangement is one main pump with a backup power source, and a fixed arrangement is two pumps, main and standby, the standby with a backup power source (C.1.3). In low-hazard buildings, with a fire load up to 300 MJ/m², a fixed arrangement may omit the standby pump, and the main pump then has the backup power source (Note 1 to C.1.3).

The backup source may be a generator or another source, such as batteries, and may be omitted when the pump has an internal combustion engine (C.1.3.2 and C.1.3.2.1). With the standby running because of a power failure, the electric main pump does not start when power returns (C.1.3.1), and the pumps, at full load, have a minimum autonomy of 2 hours up to 1,200 MJ/m², 4 hours from 1,200 to 2,400 MJ/m² and 6 hours above 2,400 MJ/m² (C.1.3.3).

Under NFPA 20, the electric pump has a normal source of power as a continually available source, connected through one of the standard’s arrangements: a dedicated service connection, a dedicated on-site power production facility connection, a dedicated feeder derived directly from the dedicated service, a feeder on a multibuilding campus under the stated conditions or a dedicated transformer connected directly from the service (9.2.1 and 9.2.2).

Every power supply is protected against damage by fire from within the premises and exposing hazards, can run the pump continuously and meets the voltage drop limits (9.1.4 to 9.1.6). At least one alternate source is required where the normal source is not reliable or where the power is for a high-rise building, unless a backup engine-driven, steam turbine-driven or electric motor-driven fire pump with an independent power source meeting 9.2.2 is installed (9.3.1 and 9.3.2).

The standard’s annex describes a reliable source: the source power plant has not had shutdowns longer than 10 continuous hours in the year before plan submittal, outages from generation or transmission failures are not routine in the area, the normal supply does not arrive through overhead conductors outside the protected facility, and only the disconnecting means and overcurrent protection the standard permits are installed in it.

The same annex states that the standard does not require the normal source to be infallible, nor does it intend to require a backup source for every electric fire pump, and it leaves the determination of reliability to the authority having jurisdiction.

Where provided, the alternate source is a generator or another source independent of the normal one, arranged so that it is not disrupted when overhead lines are de-energized for fire department operations (9.3.3 and 9.3.4). The on-site standby generator meets the voltage drop requirements of Section 9.4 and the Level 1, Type 10, Class X requirements of NFPA 110 (9.6.2.1).

Type 10 means that the load terminals of the transfer switch receive power within 10 s after loss of the normal source, not that the pump starts within 10 s: the NFPA 20 technical committee recorded that the controller listing requires the controller to power the pump within 10 s of receiving power, and it added an annex note to the First Draft of the next edition to clarify this difference.

In the dedicated arrangements, NFPA 20 permits a single disconnecting means, with its associated overcurrent protection, in the supply to the controller (9.2.3).

Where installed, it is identified as suitable for use as service equipment, lockable in both the open and closed positions, remote from the other building disconnecting means and from the other fire pump source disconnecting means, marked “Fire Pump Disconnecting Means” in letters at least 25 mm high that can be seen without opening enclosure doors or covers, and supervised in the closed position; a placard next to the controller states where it is and where any key to unlock it is kept (9.2.3.1 to 9.2.3.3).

The overcurrent protection device carries indefinitely the sum of the locked-rotor current of the largest pump motor and the full-load current of all other pump motors and accessory equipment (9.2.3.4).

4. Automatic starting and manual-only stopping

Under the Brazilian rules, automatic operation is initiated simply by opening any hydrant point in the installation (IT 22, C.1.8; NT 22, C.1.9; NBR 13714, B.1.8). Automatic control uses pressure switches on the automation manifold, wired to the control panels and the motor starters: the jockey pump starts and stops automatically, and the main pump only starts automatically (IT 22, C.1.15.2; NT 22, C.2.3; NBR 13714, B.1.13.2).

After starting, the main or booster pump is stopped manually only. In São Paulo and under NBR 13714, it is stopped at its own control panel, in the pump room (IT 22, C.1.6; NBR 13714, B.1.6); in Goiás, NT 22 requires manual-only stopping and allows the manual start point to stop the pump as well (C.1.7 and C.1.8).

With an automatic pump, there is at least one manual start point in a safe, easily accessible place in the building (IT 22, C.1.7; NT 22, C.1.8; NBR 13714, B.1.7). In NBR 13714 acceptance, the main pump is started from that manual point and stopped at its own panel (C.1.3.1).

Without automation, the pump may be operated manually only, by start-stop push buttons at each hydrant or hose reel, provided there are no more than six points; the limit does not apply when the pump draws from an elevated reservoir, with the network permanently full (IT 22, C.1.10, C.1.11 and C.2.2; NT 22, C.1.11, C.1.11.1 and C.4.2).

The push-button conductors run in rigid conduit embedded in the walls or, when exposed, in metal conduit, outside hazardous areas, and the control circuit may be stepped down to 24 V at the panel output when it shares the fire alarm conduit (IT 22, C.2.2.1 and C.2.4; NT 22, C.1.12 and C.4.2.2).

Manual-only stopping is a requirement of the Brazilian rules. In the NFPA context, there are automatic stop controllers: NFPA 20 permits automatic shutdown under defined conditions, and the NFPA 25 no-flow test records, for those controllers, how long the pump runs after starting. On a project in Brazil under IT 22, NT 22 or NBR 13714, the main and booster pumps stop manually only.

The jockey pump keeps the network pressurized within a preset range and makes up small losses, with a maximum flow of 20 L/min; its maximum operating pressure equals the main pump’s (in NT 22, the fixed booster pump’s) shutoff pressure, measured at no flow, and a differential of about 100 kPa (10 m of water) between the sequential pump starts is recommended (IT 22, C.1.15 and C.1.15.1; NT 22, C.2.1 and C.2.2; NBR 13714, B.1.13 and B.1.13.1).

In São Paulo and Goiás, it is mandatory above six outlets, except with an elevated reservoir; NBR 13714 calls for it where necessary. Under NFPA 20, the jockey pump does not need alternate or standby power, and the primary or standby fire pump is not used as a jockey pump, except as the standard permits in the positive displacement pump chapter (4.27.7 and 4.27.9).

5. Motor, nameplates and pump room

Each main or booster pump has a nameplate with manufacturer, serial number, model, rated flow and pressure, operating speed and impeller diameter, and the electric motor has a nameplate with manufacturer, type, model, serial number, power in CV, speed at rated voltage, input voltage, operating current and frequency (IT 22, C.2.15 and C.2.16; NT 22, C.4.12 and C.4.13; NBR 13714, B.2.9 and B.2.10). These data must match the pump curve, the panel and the design power supply.

Where the contract adopts NFPA 20, the motor complies with NEMA MG-1, is marked as NEMA Design B when three-phase and is specifically listed for fire pump service; an IEC motor, where used, is listed for fire service (9.5.1.1 and 9.5.1.1.2).

Direct-current motors, motors above 600 V or above 500 hp, among other types, are outside that requirement and may be used where approved (9.5.1.2); with a variable speed controller, the motor is listed, suitable and marked for inverter duty (9.5.1.4.2).

IT 22, NT 22 and NBR 13714 do not set an ingress protection rating or an insulation class: these belong to the motor selected for the pump room environment. State temperature, humidity, exposure and any hazardous-area classification for motor and panel selection.

To prevent overheating of the main pump running at no flow, NBR 13714 provides a continuous water flow through a 6 mm tube or a 6 mm orifice plate, taken from the volute and returned preferably to the reservoir or the priming tank (B.2.18); in São Paulo, IT 22 requires the same on fire pumps rated above 600 L/min (C.2.18.7).

Where the contract adopts NFPA 25, check during the no-flow test that the circulation relief valve discharges a small flow of water.

The pump room allows access all around the pumps, space for maintenance on the pumps and the panel and complete removal of any pump (IT 22, C.1.2; NT 22, C.1.1; NBR 13714, B.1.2). The pumps are protected against mechanical damage, weather, chemicals, fire or moisture, and the main pumps are coupled directly through a flexible coupling, without belts or chains (IT 22, C.1.4 and C.1.5; NT 22, C.1.5 and C.1.6; NBR 13714, B.1.4 and B.1.5).

Under NFPA 20, wiring from the controller to the motor runs in rigid metal conduit, intermediate metal conduit, electrical metallic tubing, liquidtight flexible metal conduit, liquidtight flexible nonmetallic conduit Type LFNC-B, listed Type MC cable with an impervious covering or Type MI cable, and connections at the motor terminal box use a listed means of connection, without twist-on, insulation-piercing or soldered connectors (9.4.4.1 to 9.4.4.3).

6. Testing: fortnightly under NBR 13714, monthly or weekly under NFPA 25

Under NBR 13714, fire pumps, their accessories and the alarm devices are run fortnightly for at least 15 min; audible alarms may be silenced right after activation (note to C.2.2). The periodic inspection takes place at intervals of no more than three months, by the fire brigade or specially trained personnel (C.2), and carrying out the maintenance plan, prepared by the designer, takes no longer than one year (5.10.2 and C.3.1).

At acceptance, carried out by a qualified professional, the pressure switch settings, the alarms, starting from the emergency generator and stopping at the pump’s own panel are tested (C.1 and C.1.3.1).

Under NFPA 25, most electric fire pumps run the no-flow test monthly. The test is weekly when the pump serves systems in buildings beyond the pumping capacity of the fire department, has a limited service controller, is a vertical turbine pump or takes suction from ground level tanks or a water source that does not provide sufficient pressure to be of material value without the pump, unless a redundant pump is provided.

Both frequencies allow the interval to be extended on the basis of an approved risk analysis, which the standard’s annex recommends be prepared and reviewed by qualified people.

The test start is automatic, by draining water from the pressure sensing line to simulate a pressure drop in the system, not with the controller’s start button; NFPA 25 allows an automatic timer with a solenoid drain valve on the pressure control line. The electric pump runs for at least 10 minutes, with qualified personnel in attendance, unless automated inspection and testing is performed in accordance with the standard.

With the pump at rest, record the suction and discharge pressures and, for controllers with electronic pressure sensors, the highest and lowest pressure in the event log, where that information is available without opening an energized controller; with the pump running, record the starting pressure and the suction and discharge pressures, and check for noise, vibration and overheating of packing boxes, bearings and casing.

The annual flow test verifies the complete operating condition of the pump. At the electric controller, NFPA 25 calls for the NFPA 70E safe work practices, or an equivalent program approved by the authority having jurisdiction, and relieves the readings and inspections that could only be done by opening the energized controller, including recording motor voltage and current.

Many fire pumps are supplied directly from a service with no upstream overcurrent protection, and the lack of that protection exposes service personnel to electric shock and arc flash.