12.3 Wind Electric Systems and Fire Pumps

Article 694 — Wind Electric Systems

694.1 Scope. Article 694 applies to wind electric systems that consist of one or more wind electric generators. These systems can include generators, alternators, inverters, and controllers.

694.7 Installation. (A) Wind Electric Systems. A wind electric system shall be permitted to supply a building or other structure in addition to any service(s) of another electricity supply system(s). (B) Equipment. Inverters, motor generators, wind generators, surge arresters, and charge controllers shall be identified and listed for use in wind electric systems. (C) Qualified Personnel. The installation of equipment and all associated wiring and interconnections shall be performed only by qualified persons.

694.12 Circuit Sizing and Current. (A) Calculation of Maximum Circuit Current. The maximum current for the specific circuit shall be calculated as the rated continuous output current of the wind turbine at its rated output power for the output circuit, and the maximum current output rating of the inverter for the inverter output circuit. (B) Ampacity and Overcurrent Device Ratings. Wind turbine output circuit conductors and overcurrent devices shall be sized to carry not less than 125 percent of the maximum currents as calculated in 694.12(A).

694.22 Additional Provisions. (A) Disconnecting Means. Means shall be provided to disconnect all current-carrying conductors of a wind electric power source from all other conductors in a building or other structure. (B) The disconnecting means shall be readily accessible and shall be lockable open in accordance with 110.25 where remote from the turbine. (C) The disconnecting means shall be permanently marked to identify it as a wind electric system disconnect.

694.23 Turbine Shutdown. Wind electric systems shall be provided with a manual shutdown button or switch. The shutdown button or switch shall be located at a readily accessible location. The shutdown method shall not require the turbine to be in a parked state before initiation, and the shutdown procedure shall place the turbine in a parked state.

694.24 Loss of Interactive System Power. An inverter or AC module that is used in an interactive wind electric system shall automatically de-energize its output to the connected electrical production and distribution network upon loss of voltage in that system and shall remain in that state until the electrical production and distribution network voltage has been restored.

694.28 Grounding Electrode System. (A) A grounding electrode system shall be provided in accordance with 250.50 through 250.60. (B) Tower and Turbine Grounding. Towers and turbine nacelles shall be connected to a grounding electrode system. 694.40 Equipment Grounding and Bonding requires exposed non-current-carrying metal parts of towers, turbine nacelles, and other equipment to be grounded.

694.30 Wiring Methods. All raceway and cable wiring methods included in the Code and other wiring systems and fittings specifically listed for use on wind turbines shall be permitted. Flexible cords and cables, where used to connect the moving parts of turbines or where used for ready removal for maintenance and repair, shall comply with Article 400 and shall be listed for extra-hard usage, be water resistant, and be sunlight resistant.

Small wind systems are meaningful in Alaska for remote village power, telecommunications sites, and off-grid homes, often combined with PV and battery storage in the DC microgrid architecture of Article 712.

Article 695 — Fire Pumps

Fire pump circuits invert the Code's usual priority. Everywhere else, the objective is to open the circuit on a fault. For a fire pump, the objective is to keep the pump running as long as physically possible, even to the point of destroying the motor. A burned-out fire pump motor in a burning building has still done its job; a fire pump that trips offline has not.

695.3 Power Source(s) for Electric Motor-Driven Fire Pumps. Electric motor-driven fire pumps shall have a reliable source of power. Acceptable sources include:

• (A)(1) Electric Utility Service Connection. A fire pump shall be permitted to be supplied by a separate service, or from a connection located ahead of and not within the same enclosure as the service disconnecting means.
• (A)(2) On-Site Power Production Facility. A fire pump shall be permitted to be supplied by an on-site power production facility, located and protected to minimize the possibility of damage by fire.
• (B) Multiple Sources. Where reliable power cannot be obtained from a source described in (A), power shall be supplied by an approved combination of two or more of the specified sources.
• (C) Multibuilding Campus-Style Complexes provides a further alternative under specified conditions.

695.4 Continuity of Power. Circuits that supply electric motor-driven fire pumps shall be supervised from inadvertent disconnection as covered in 695.4(A) or (B).

• (A) Direct Connection. The supply conductors shall directly connect the power source to a listed fire pump controller, a listed fire pump power transfer switch, or a listed combination fire pump controller and power transfer switch.
• (B) Connection Through Disconnecting Means and Overcurrent Device. A single disconnecting means and associated overcurrent protective device shall be permitted between the power source and one of the following: a listed fire pump controller, a listed fire pump power transfer switch, or a listed combination fire pump controller and power transfer switch.
  • (B)(1) Number of Disconnecting Means. A single disconnecting means and overcurrent device shall be permitted for each source.
  • (B)(2)(a) Overcurrent Device Selection. The overcurrent protective device shall be rated to carry indefinitely the sum of the locked-rotor current of the largest fire pump motor and the full-load current of all of the other pump motors and accessory equipment. Where the locked-rotor current value does not correspond to a standard overcurrent device size, the next standard overcurrent device size shall be used.
  • (B)(3) Disconnecting Means. The disconnecting means shall comply with all of the following: be identified as "FIRE PUMP DISCONNECTING MEANS" in letters not less than 25 mm (1 in.) in height and visible without opening enclosure doors or covers; be lockable in the closed position; be located remote enough from other building disconnecting means that inadvertent contemporaneous operation is unlikely; and be supervised in the closed position by one of four listed methods including central station, local signaling service, locking the disconnecting means closed, or sealing with weekly recorded inspections.

The locked-rotor current requirement in (B)(2)(a) is the point of the whole article. A fire pump motor with a 100-ampere full-load current may have a locked-rotor current near 600 amperes. The upstream overcurrent device must carry that indefinitely — meaning the pump can stall and burn without opening the circuit and dropping the other fire pumps.

695.5 Transformers. Where a transformer supplies an electric motor-driven fire pump, it shall be rated at a minimum of 125 percent of the sum of the fire pump motor(s) and pressure maintenance pump(s) loads, and 100 percent of the associated fire pump accessory equipment supplied by the transformer. The primary overcurrent device shall be rated or set to carry indefinitely the sum of the locked-rotor current of the largest fire pump motor and the full-load current of all other pumps and accessory equipment.

695.6(A)(2) Supply Conductors — Services, Feeders, and Branch Circuits Supplying Fire Pumps. Supply conductors shall be physically routed outside a building and shall be installed as service-entrance conductors in accordance with Article 230, or shall be encased in 50 mm (2 in.) of concrete or brick as specified, or shall be protected by a fire-rated assembly listed to achieve a minimum fire rating of 2 hours.

695.6(B) Conductor Size. Conductors supplying a fire pump motor, pressure maintenance pumps, and associated fire pump accessory equipment shall have a rating not less than 125 percent of the sum of the fire pump motor(s) and pressure maintenance motor(s) full-load current(s), and 100 percent of the associated fire pump accessory equipment.

695.6(D) Pump Wiring. All wiring from the controllers to the pump motors shall be in rigid metal conduit, intermediate metal conduit, liquidtight flexible metal conduit, liquidtight flexible nonmetallic conduit Type LFNC-B, or Type MI cable.

695.6(H) Ground-Fault Protection of Equipment. Ground-fault protection of equipment shall not be installed in any fire pump power circuit. This is one of the very few outright prohibitions of a protective device in the Code, and it exists for the same reason as everything else in Article 695: an unwanted GFPE trip would stop the pump.

695.7 Voltage Drop.

• (A) Motor Starting. The voltage at the line terminals of a fire pump controller shall not drop more than 15 percent below normal (controller-rated voltage) under motor starting conditions.
• (B) Motor Running. The voltage at the load terminals of the motor controller shall not drop more than 5 percent below the voltage rating of the motor when the motor is operating at 115 percent of the full-load current rating of the fire pump motor.

These are mandatory voltage-drop limits, unlike the advisory Informational Notes in 210.19(A) and 215.2(A).

695.10 Listed Equipment. Diesel engine fire pump controllers, electric fire pump controllers, electric motors, fire pump power transfer switches, foam pump controllers, and limited service controllers shall be listed for fire pump service.

695.14(F) Electrical Circuit Protective Systems. Electrical circuit protective systems shall be installed in accordance with the listing requirements for the system.

695.15 Surge Protection. A listed surge protective device shall be installed in or on the fire pump controller.