90.2 Scope. The installation of electrical conductors, equipment and raceways for:

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1 NEC Generator Primer Rules on the installation of generators and transfer switches Scope The installation of electrical conductors, equipment and raceways for: public and private premises Conductors and equipment that connect to the supply of electricity Generators and transfer switches are equipment 2 Article 445 Generators 3 1

2 Generators shall be of a type suitable for the locations in which they are installed. They also shall satisfy Generators shall be located such that: Adequate ventilation can be provided Maintenance can be readily accomplished Generators to have a nameplate giving: Manufacturer Frequency, PF and phases Subtransient and transient impedances Rating in kw or kva Voltage and ampere rating and rpm Insulation system class Rated ambient temperature or temperature rise Time rating

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4 Generator Rating Definitions Standby Rating: Applicable for supplying emergency power for the duration of normal power interruption. No sustained overload capability is available for this rating. Prime (Unlimited Running Time) Rating: Applicable for supplying power in lieu of commercially purchased power. Prime power is the maximum power available at a variable load for an unlimited number of hours. A 10% overload capability is available for limited time. Base Load (Continuous) Rating: Applicable for supplying power continuously to a constant load up to the full output rating for unlimited hours. No sustained overload capability is available for this rating

5 Overcurrent Protection (A) Constant voltage generators shall be protected from overload by Inherent design Circuit breakers Fuses Protective relays Other identified means suitable for the conditions of use

6 Overcurrent Definition: Any current in excess of the rated current of equipment or the ampacity of a conductor. It may result from overload, short circuit or ground fault Overcurrent Protection, Location in Circuit (G) Conductors from Generator Terminals. Conductors from generator terminals that meet the size requirement in shall be permitted to be protected against overload by the generator overload protective device(s) required by

7 Ampacity of Conductors Shall be 115% of the nameplate current rating It is permitted to derate neutral per for the maximum unbalanced load Conductors that carry ground fault currents shall not be smaller than required by (A)

8 Disconnecting Means Required for Generators Generators shall be equipped with disconnect(s), lockable in the open position to disconnect entirely the generator and all protective devices and control apparatus Exceptions: If the driving means can be readily shut down, and If the generator is not arranged to operate in parallel with another generator or other source of power

9 Wiring, Emergency System (B) wiring from an emergency source to emergency loads shall be kept entirely independent of all other loads with some exceptions IBC Chapter 27, Electrical Emergency loads: Egress lighting Exit signs Voice alarm communications in places of assembly Semiconductor fabrication facilities High-rise and underground buildings Prisons and jails Storage or manufacture of: Hazardous material Highly toxic material Pyrophoric materials 27 9

10 Emergency and Legally Required Standby Electrical Power Sources NFPA 110 Referenced by Informational Note in Referenced by IBC (required to be used) Requires a remote manual stop station Located outside the room housing the prime mover Requires an audible alarm Requires battery powered emergency lighting Requires an initial acceptance test with AHJ Prime movers to comply with NFPA 37 NFPA 37 Engine rooms located within structures to have minimum 1 hour walls, floor and ceiling. Engines on roofs shall be minimum 5 feet from openings and any combustible structures or walls. Engines located outdoors shall be a minimum 5 feet from openings and any combustible structures or walls. NFPA s opinion A generator is considered a source of ignition as it contains an internal combustion engine

11 Clearances from Propane Clearances from propane Is a propane optional standby generator considered a source of ignition at a residential dwelling? ANSWER: YES If the propane generator is considered a source of ignition, how far from the generator should the gas regulator be installed? ANSWER: The issue is not the regulator location but the discharge from the regulator which needs to be 5 feet from a source of ignition. How far from the generator should the relief valve be installed? ANSWER: See answer #2 What is the distance that the propane generator should be located from the propane tank? ANSWER: 10 Feet JOHN DOUCETTE OFFICE OF STATE FIRE MARSHAL Photo Contributed by Joseph Summers

12 Clearances from air intake IRC and IMC require a clearance of 2 feet above any mechanical air intake opening within 10 feet of the exhaust pipe discharge Includes windows that open, fresh air and combustion air intakes 2011 NEC Generators Supplying Multiple Loads Shall be permitted to supply either: A vertical switchboard with separate sections Individual enclosures with overcurrent protection tapped from a single feeder for load separation and distribution if provided with OC protection

13 Article 702 Optional Standby Systems

14 702.1 Scope The systems covered by Article 702 consist of those that are permanently installed, including prime movers, and those that are arranged for a connection to a premises wiring system from a portable alternate power supply

15 702.1 Scope A portable generator used for temporary power, like those used on construction sites, doesn't fall within the scope of Article 702 unless the generator is connected to the premises wiring Definition Optional Standby Systems. Optional standby systems are intended to supply power to public or private facilities or property where life safety doesn't depend on the performance of the system

16 702.2 Definition Optional standby systems typically provide electric power for processes that, when stopped could cause discomfort, economic loss, serious interruption of the process, or damage to the product or process Definition Can be either manual or automatic, selected, partial or total loads IBC Chapter 27, Electrical Lists when Emergency and Legally required standby systems are required All other systems are optional standby

17 2011 NEC Capacity and Rating An optional standby system must have adequate capacity to carry safely all loads that are expected to operate simultaneously. The user of the optional standby system can select the loads connected to the system. 49 Choose the loads straight from the panel NEC HANDBOOK The standby source must have the capacity to supply all of the loads connected to it, unless an automatic load management system is used to ensure that the transferred load does not overload the source. This requirement applies only to systems where the switching between power sources occurs automatically

18 2011 NEC Section If an automatic transfer switch is used: Standby source must be capable of handling the full load to be transferred, OR An automatic load shedding capability shall be installed to limit the load to that the standby source can handle 54 18

19 Transfer Equipment Equipment shall be suitable for the intended use A transfer switch is required for all fixed or portable optional standby power systems

20 702.5 Transfer Equipment Ex: Transfer switch not required for temporary connection, where written safety procedures and conditions of maintenance and supervision ensure that only qualified persons will service the installation if: The normal supply is physically isolated by a lockable disconnecting means or The normal supply conductors are disconnected Wiring The optional standby system wiring can occupy the same raceways, cables, boxes, and cabinets with other general wiring

21 Portable Generators When the portable generator is a separately derived system, the generator(s) must be grounded and bonded in accordance with

22 Outdoor Generator Sets Where an outdoor-housed generator is equipped with a readily accessible disconnecting means that is located within sight of the building or structure, an additional disconnecting means isn't required for the generator feeder conductors that serve or pass through the building or structure. Article 250 on Grounding Generators

23 250.34(A) Portable Generators (B) Vehicle-mounted Frames are not required to be connected to a grounding electrode if: Only cord connected equipment is energized, or Only generator mounted equipment is energized, or both, and The non-current carrying metal parts and the grounding terminals of receptacles are connected to the frame Vehicle frame not required to be connected to a grounding electrode if: Frame of generator is bonded to the vehicle frame, and Only equipment on the vehicle or cord connected loads are energized, and The non-current carrying metal parts and the grounding terminals of receptacles are connected to the frame 69 23

24 250.34(C) Grounded Conductor Bonding With both portable and vehicle mounted generators: A system conductor (i.e. neutral) is required to be grounded. It shall be connected to the generator frame where the generator is a component of a separately derived system

25 Grounding Separately Derived AC Systems In addition to (A), grounded systems shall also comply with , , and tells which systems must be grounded tells which systems might not be grounded tells which circuits must not be grounded tells which conductor must be grounded With most voltages over 50 volts and most systems, the neutral is the conductor to be grounded Article Definitions The definition of a Separately Derived System was amended and simplified for clarity Separately Derived System. A premises wiring system whose power is derived from a source of electric energy or equipment other than a service Such systems have no direct electrical connection from circuit conductors of one system to circuit conductors of another system, other than connections through the earth, metal enclosures, metallic raceways, or equipment grounding conductors including a solidly connected grounded circuit conductor, to supply conductors originating in another system (B) AC Systems to be grounded 240/120 volt systems that supply premises wiring are required to be grounded. Neutral is required to be grounded Article 100: Grounded Connected to ground or to a conductive body that extends the ground connection. If the generator neutral is not bonded to the frame it is not a separately derived system The service GES provides the conductive body that extends the ground connection

26 250.30(A) Grounded Systems Please note no generator frame ground connection A separately derived system shall have: An unspliced system bonding jumper which shall be connected at any point from the source to the first disconnecting means 78 26

27 Please note generator frame grounding connection CONDITIONS WHERE GROUNDING THE GENERATOR FRAME TO GROUNDING ELECTRODE SYSTEM IS REQUIRED: 1. The generator is not part of a separately derived system, OR 2. It has its neutral conductor solidly interconnected to a service-supplied system neutral, OR 3. It supplies auxiliary power output (115 volts AC / 230 volts AC) by means other than cord-and-plug connection through receptacles mounted on the generator, such as connections to internal terminals on the generator hard wired (see equipment Owner s Manual for grounding instructions)

28 CONDITIONS WHERE GROUNDING THE GENERATOR FRAME TO A GROUNDING ELECTRODE SYSTEM IS NOT REQUIRED: 1. The generator has auxiliary power output (115 volts AC or 230 volts AC) and the generator receptacles have a ground pin outlet available for the equipment that plugs into the receptacle, AND 2. The generator is portable or mounted on a truck or trailer, AND 3. The auxiliary power is used by cord-and plugconnection means through receptacles mounted on the generator, AND 4. The generator is mounted on a vehicle and the generator frame is bonded to the vehicle frame. 82 The decision is based on what you do with your auxiliary power: If you just plug equipment into the receptacles, connection to the vehicle frame is fine. If you hard wire the auxiliary power into another electrical system, then you must connect the generator frame to a grounding electrode system 83 Article 225 on Generators 84 28

29 Number of Supplies (A) Special Conditions. Additional feeders shall be permitted for: Fire pumps Emergency systems Legally required standby systems Optional standby systems Parallel power production systems Multiple sources of supply Disconnecting Means Means shall be provided to disconnect all ungrounded conductors that supply or pass through the building or structure Location The disconnecting means shall be installed at a readily accessible location nearest the point of entrance of the conductors

30 Suitable for Service Disconnect Identification The disconnecting means specified in shall be suitable for use as service equipment. A permanent plaque or directory shall be installed at each disconnect location denoting all other services, feeders or branch circuits supplying that building or structure Article 230 on Generators

31 230.2 Number of Services Marking 100 Definition Service Equipment (E) Identification Where a building is supplied by a combination of feeders and services, a permanent plaque or directory shall be installed at each service disconnect location denoting all other sources supplying the building or structure Service equipment shall be marked to identify it as being suitable for use as service equipment. All service equipment shall be listed. The necessary equipment connected to the load end of service conductors to a building or structure

32 Equipment Connected to the Supply Side of Service Disconnect Only the following equipment is allowed: (3) Meter disconnect switches with short circuit ratings equal to or greater than the available short-circuit rating Official Word The Generlink has been approved for use jointly by the CT DCP and Connecticut Light and Power. There are rules:

33 CL and P rules for Generlink Home owners are suggested to have a EC do the work OR must do paperwork to disconnect power get inspection approved and then arrange for a reconnection of power Pre-approved EC allowed to remove and put meter back in after install. Must have permit and CSR prior to installation Inspector has nothing to see when installed Only the paper trail Suggest electrical contractor take pictures Equipment Connected to the Supply Side of Service Disconnect Only the following equipment is allowed: (5) Taps used only to supply.circuits for standby power systems If provided with service equipment and installed in accordance with requirements for service entrance conductors. Standby power systems are allowed to be connected ahead of the normal service disconnecting means only if it is provided with a separate disconnecting means and overcurrent protection. 98 TS Connected Ahead of Main Must be listed and marked as suitable for use as service equipment (230.66) Must match ampacity and voltage of service (230.90) Must be adequate for available fault current (110.9) Service ends at first disconnect on building Grounding of grounded conductor must occur on the line side of or in same enclosure as disconnect (250.24(A)(1), (A)) 99 33

34 Overcurrent Protection Synchronous Generators Article 705 Interconnected Electric Power Production Sources Part III Generators Conductors to be protected per Article 240 Equipment and conductors to have OC protection to protect from all sources Generators to be protected per Parallel production generators shall have the necessary equipment to establish and maintain a synchronous condition

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