−---
−title: Emergency and Standby Power Systems
−category: Electrical / Power Distribution Equipment
−toc_depth: 3
−description: >
− When to use: System-level standard establishing the classification, source selection, load assignment, transfer scheme, overcurrent coordination, and acceptance testing for a building's emergency and standby power system, in accordance with NFPA 70 Articles 700 (Emergency Systems), 701 (Legally Required Standby), 702 (Optional Standby), and 708 (Critical Operations Power Systems), and NFPA 110 and NFPA 111. Use this standard to define what the system must do as a whole — which loads are emergency vs. standby, what alternate source serves them, how fast they transfer, and how they are commissioned and maintained. Component-level requirements are deferred to the equipment standards for the engine-generator set (see [[sync/generators]]), the automatic transfer switches (see [[sync/automatic-transfer-switches]]), and the stored-energy sources (see [[sync/dc-battery-systems]]).
− Not intended for: Selection or sizing of an individual engine-generator set, transfer switch, battery, or UPS module (use the component standards), the project overcurrent selective coordination study itself (see [[sync/protective-coordination-study]]), normal-power distribution equipment, utility service entrance design, microgrid or utility-paralleled distributed generation operated for economic dispatch, or grid-tied photovoltaic and battery storage systems whose primary purpose is energy management rather than life-safety backup.
−---
−
−# Scope
−
−This specification establishes the system-level requirements for a building's emergency and standby power system: the body of equipment and wiring that supplies electrical power to designated loads when the normal source fails. It defines how loads are classified, which alternate source serves each class of load, how the load is transferred between sources, how the overcurrent protective devices are coordinated, and how the complete system is commissioned, tested, and maintained. The standard is the umbrella under which the individual pieces of equipment are coordinated; it does not itself specify the construction of any one piece of equipment.
−
−The legal weight of this system is unusual. For emergency systems under NFPA 70 (NEC) Article 700, the wiring, sources, and transfer equipment exist to protect human life during a power failure, and the requirements are correspondingly strict. The system shall be designed, installed, and commissioned as an integrated whole — the generator, the transfer switches, the stored-energy sources, the coordinated overcurrent devices, and the wiring that connects them are not independent scopes that happen to be in the same building. A correctly sized generator behind a transfer switch that cannot transfer in time, or a correctly rated transfer switch fed by a feeder that is not coordinated, is a non-compliant system regardless of how good each component is in isolation.
−
−This standard coordinates with and defers component detail to the engine-generator set (see [[sync/generators]]), the automatic transfer switches (see [[sync/automatic-transfer-switches]]), the stored-energy and battery sources (see [[sync/dc-battery-systems]]), and the overcurrent selective coordination study (see [[sync/protective-coordination-study]]). Where this standard and a component standard appear to conflict, the system-level intent stated here governs the coordination, and the component standard governs the construction of that component.
−
−This standard does not establish the normal-power distribution, the utility service, or any source operated principally for economic dispatch or energy management. Distributed generation interconnected to the utility for parallel operation under IEEE 1547 is outside scope except where a closed-transition or paralleling alternate source is used solely to restore a backup function; those provisions are coordinated through [[sync/automatic-transfer-switches]] and [[sync/generators]].
−
−# Referenced Standards
−
−Design, equipment, and installation shall comply with the latest adopted edition of the following. Where the contract documents, the adopted building code, or a referenced standard conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
−
−| Standard | Title |
−|----------|-------|
−| NFPA 70 | National Electrical Code (Articles 700, 701, 702, 705, 708, 230, 250, 110) |
−| NFPA 110 | Standard for Emergency and Standby Power Systems |
−| NFPA 111 | Standard on Stored Electrical Energy Emergency and Standby Power Systems |
−| NFPA 101 | Life Safety Code (means of egress illumination) |
−| NFPA 99 | Health Care Facilities Code (where applicable) |
−| NFPA 70E | Standard for Electrical Safety in the Workplace |
−| IBC | International Building Code (egress illumination, seismic, importance factors) |
−| UL 924 | Emergency Lighting and Power Equipment |
−| UL 1008 | Transfer Switch Equipment |
−| UL 1778 | Uninterruptible Power Systems |
−| UL 2200 | Stationary Engine Generator Assemblies |
−| IEEE 446 | Recommended Practice for Emergency and Standby Power Systems for Industrial and Commercial Applications (Orange Book) |
−| IEEE 241 | Recommended Practice for Electric Power Systems in Commercial Buildings (Gray Book) |
−| IEEE 1547 | Standard for Interconnection and Interoperability of Distributed Energy Resources |
−| ASCE 7 | Minimum Design Loads and Associated Criteria for Buildings and Other Structures |
−| ICC ES AC156 | Acceptance Criteria for Seismic Certification by Shake-Table Testing |
−| ANSI/NETA ATS | Standard for Acceptance Testing Specifications for Electrical Power Equipment and Systems |
−
−# Submittals
−
−## Action Submittals
−
−Contractor shall submit the following for the Engineer's review prior to procurement of system equipment. Procurement of long-lead items shall not proceed until the system-level submittals establishing classification, source assignment, and transfer scheme have been reviewed and returned.
−
−- System one-line diagram showing the normal source, each alternate source, every transfer switch, the load class served by each transfer switch, and the boundary between the emergency, legally required standby, and optional standby portions of the system, coordinated with [[drawing: the contract one-line diagram]]
−- Load schedule classifying each connected load as emergency (Article 700), legally required standby (Article 701), optional standby (Article 702), or critical operations (Article 708), with connected and demand kW/kVA for each class, coordinated with [[drawing: the contract load schedules]]
−- Alternate source capacity calculation demonstrating that each source can carry its assigned loads at the worst-case step and steady state, including the starting kVA and voltage-dip analysis from [[sync/generators]]
−- Transfer scheme narrative describing transfer type, time delays, source priority, and load-shed sequence for each transfer switch, consistent with [[sync/automatic-transfer-switches]]
−- NFPA 110 classification statement (Level, Type, and Class) for each portion of the system, with the basis for each selection
−- Selective coordination study confirming compliance with NEC 700.32, 701.32, and 708.54 as applicable, prepared per [[sync/protective-coordination-study]]
−- Wiring separation and circuit-integrity plan for the Article 700 emergency portion per NEC 700.10
−- Emergency illumination duration calculation demonstrating 90-minute egress illumination per NFPA 101 and the IBC for any stored-energy egress source
−- Integrated commissioning plan describing the system acceptance test per NFPA 110 Chapter 7
−
−```datasheet
−label: System-Level Action Submittals Required
−type: checkbox
−options:
− - "System one-line with source/load-class boundaries"
− - "Load schedule classified by NEC article (700/701/702/708)"
− - "Alternate source capacity and step-load calculation"
− - "Transfer scheme narrative (type, delays, priority, load shed)"
− - "NFPA 110 Level/Type/Class classification statement"
− - "Selective coordination study (700.32 / 701.32 / 708.54)"
− - "Article 700 wiring separation and circuit-integrity plan"
− - "Emergency illumination 90-minute duration calculation"
− - "Integrated commissioning / acceptance test plan"
−default: "System one-line with source/load-class boundaries"
−```
−
−## Closeout Submittals
−
−Contractor shall provide the following at substantial completion before the system is accepted into emergency or standby service.
−
−- Signed and dated NFPA 110 integrated acceptance test record covering the complete normal-source / alternate-source / transfer chain
−- As-built system one-line and load schedule reflecting the installed configuration and the commissioned transfer settings
−- Final selective coordination study reflecting as-installed overcurrent device settings and ratings
−- Operation and maintenance manuals for the system, including the testing and maintenance schedule required by NFPA 110 Chapter 8
−- Written instructions to the Owner establishing the periodic testing intervals, the maintenance log format, and the recordkeeping obligations under the applicable NEC articles and NFPA 110
−- Owner training sign-off documenting system operation, source transfer behavior, and emergency response procedures
−
−# Quality Assurance
−
−## Designer and System Integrator Qualifications
−
−The system one-line, load classification, source capacity calculation, and selective coordination study shall be prepared by or under the responsible charge of a licensed Professional Engineer. NEC 708.54 requires that the selective coordination of a critical operations power system be performed by a licensed Professional Engineer or other qualified person; this standard extends that expectation to the coordination study for Article 700 and 701 systems as well.
−
−## System Integration Responsibility
−
−A single party shall be responsible for demonstrating that the assembled system meets its NFPA 110 classification end to end. Acceptance of the individual components (the generator startup, the transfer switch commissioning, the battery commissioning) does not constitute acceptance of the system; the integrated acceptance test under NFPA 110 Chapter 7 is what places the system in service.
−
−## Testing Personnel Qualifications
−
−Integrated system acceptance testing shall be performed by technicians certified by NETA, EGSA, or the equipment manufacturer's training program, with documented experience commissioning emergency power systems of comparable scope. Personnel shall coordinate the generator field test (see [[sync/generators]]) and the transfer switch field test (see [[sync/automatic-transfer-switches]]) so that the chain is verified as one system.
−
−# Environmental and Service Conditions
−
−System-level environmental conditions are established at the component standards. This standard requires only that the alternate source remain available during the same events that may cause the normal-source outage. For life-safety systems in seismic, high-wind, or flood-prone regions, the source, its fuel or stored-energy supply, and its cooling shall not depend on a utility or infrastructure that is likely to fail in the same event. A natural-gas-fueled generator tied to a utility gas supply, or a generator cooled by a domestic water main, may not satisfy this requirement for an Article 700 system; confirm the Authority Having Jurisdiction position before relying on a source whose continued operation depends on another utility.
−
−```datasheet
−label: Alternate Source Availability Basis
−type: radio
−options:
− - "On-site stored fuel or energy (independent of other utilities)"
− - "Continuous utility fuel supply (natural gas / LP, with AHJ acceptance)"
− - "Dual source (on-site stored plus utility supplement)"
−default: "On-site stored fuel or energy (independent of other utilities)"
−```
−
−# Load Classification
−
−The first design decision is the classification of each connected load. Classification determines which NEC article governs the load, how fast it shall be restored, how its wiring shall be separated, and whether selective coordination is mandatory. A load that is mis-classified — for example, a life-safety load assigned to an optional standby branch — produces a system that is non-compliant even if every piece of equipment performs perfectly.
−
−## Article 700 — Emergency Systems
−
−Emergency systems supply loads whose failure could cause loss of human life or serious injury: egress and exit illumination, exit signage, fire alarm and detection, fire pumps where designated, smoke control, elevators required for egress, and life-support and similar loads in occupancies that require them. Emergency systems shall restore power to their loads within 10 seconds of normal-source failure (NEC 700.12), their wiring shall be kept entirely independent of all other wiring per NEC 700.10(B), and their overcurrent devices shall be selectively coordinated per NEC 700.32.
−
−## Article 701 — Legally Required Standby Systems
−
−Legally required standby systems supply loads that the adopted code or the Authority Having Jurisdiction requires to be backed up but whose failure does not immediately endanger life: heating and ventilation for habitability, sewage and stormwater pumping, certain communications, and industrial processes whose interruption creates a hazard. Legally required standby systems shall restore power within 60 seconds (NEC 701.12), may share raceways and enclosures with general wiring, and shall be selectively coordinated per NEC 701.32.
−
−## Article 702 — Optional Standby Systems
−
−Optional standby systems supply loads that the Owner elects to back up for convenience, comfort, or economic continuity, where life safety does not depend on the system: data processing, refrigeration, general lighting and receptacles, and similar loads. Optional standby systems have no code-mandated transfer time, no mandatory wiring separation, and no mandatory selective coordination; their performance is set by the Owner's continuity requirements.
−
−## Article 708 — Critical Operations Power Systems
−
−Critical operations power systems supply designated critical operations areas (DCOA) in facilities whose loss would disrupt national security, the economy, or public safety, as designated by a governmental authority or by the facility's own engineering documentation. COPS carry the most stringent requirements: full selective coordination of all overcurrent devices supplying COPS loads per NEC 708.54, enhanced commissioning, and documented maintenance. Apply Article 708 only where the load has been formally designated; it is not a default for ordinary critical loads.
−
−```datasheet
−label: System Classes Present on This Project
−type: checkbox
−options:
− - "Article 700 — Emergency (life safety, 10 s transfer)"
− - "Article 701 — Legally Required Standby (60 s transfer)"
− - "Article 702 — Optional Standby (Owner continuity)"
− - "Article 708 — Critical Operations Power System (designated DCOA)"
−default: "Article 700 — Emergency (life safety, 10 s transfer)"
−```
−
−The classification of each individual load shall be [[drawing: as indicated on the load schedule and panel schedules]]. Where a single building contains more than one class, the system shall maintain the separation and priority appropriate to the highest class present.
−
−# Source Selection
−
−## Alternate Source Type
−
−The alternate source shall be selected to match the load class, the required transfer time, and the required runtime. The engine-generator set is the default alternate source for systems whose loads exceed the practical limit of a stored-energy source and whose required runtime exceeds the runtime achievable from batteries. Stored-energy sources (battery/inverter, central battery egress equipment, or UPS) are appropriate where the load is small, where a zero-interruption transition is required, or where the only emergency load is egress illumination. Many systems use both: a generator for the bulk of the standby load and a stored-energy source to bridge the engine-start interval for loads that cannot tolerate the 10-second gap.
−
−```datasheet
−label: Primary Alternate Source
−type: radio
−options:
− - "Engine-generator set (see component standard)"
− - "Stored-energy: central battery / inverter egress equipment (UL 924)"
− - "Stored-energy: uninterruptible power supply (UPS, UL 1778)"
− - "Generator plus UPS (UPS bridges engine-start interval)"
− - "Fuel cell (continuous, with AHJ acceptance)"
−default: "Engine-generator set (see component standard)"
−```
−
−The engine-generator set, where used, shall be specified per [[sync/generators]]. The stored-energy source, where used, shall be specified per [[sync/dc-battery-systems]] and applied per NFPA 111. This standard establishes which source serves which load and what each source shall accomplish; the construction of each source is set by its component standard.
−
−## Stored-Energy Source for Egress Illumination
−
−Where egress illumination is supplied by a stored-energy source rather than a generator, the source shall provide not less than 90 minutes of the required illumination per NFPA 101 and the IBC, and the equipment shall be UL 924 listed for emergency service. The 90-minute duration is the controlling sizing parameter for a battery or inverter egress source and shall be demonstrated by calculation in the submittal.
−
−```datasheet
−label: Egress Illumination Source
−type: radio
−options:
− - "Generator-backed emergency lighting (transfer within 10 s)"
− - "Central battery / inverter unit (UL 924, 90-minute)"
− - "Distributed unit equipment (UL 924 fixtures with integral battery, 90-minute)"
− - "Generator plus unit equipment (defense in depth)"
−default: "Generator-backed emergency lighting (transfer within 10 s)"
−```
−
−```datasheet
−label: Emergency Illumination Duration
−type: select
−unit: min
−options:
− - "90 minutes (NFPA 101 / IBC egress minimum)"
− - "120 minutes (extended, per AHJ or owner)"
− - "Generator-backed (duration set by fuel Class, not battery)"
−default: "90 minutes (NFPA 101 / IBC egress minimum)"
−```
−
−## Source Redundancy
−
−```datasheet
−label: Source Redundancy
−type: radio
−options:
− - "Single alternate source (N) — typical"
− - "N+1 redundant sources (one spare source)"
− - "2N fully redundant sources (independent A/B)"
−default: "Single alternate source (N) — typical"
−```
−
−A single alternate source is the default for most buildings. Redundant sources are appropriate where the load cannot tolerate the loss of the alternate source during maintenance or a single source failure — typically hospitals, data centers, and Article 708 facilities. Source redundancy is a system decision that drives the number of generators, the paralleling scheme, and the number and bypass construction of the transfer switches; it shall be resolved before the component standards are applied.
−
−# Load Assignment and Sizing
−
−The alternate source shall be sized for the connected load it serves at the worst-case starting step and at steady state, with the load assigned to the source according to its class. Where one source serves more than one class — a single generator serving both emergency and standby loads, for example — the emergency loads shall have priority and the lower-class loads shall be shed if the source approaches capacity.
−
−## Load Assignment Method
−
−```datasheet
−label: Load Assignment Method
−type: radio
−options:
− - "Dedicated source per class (separate source for emergency vs. standby)"
− - "Single source, priority load management (emergency first, shed lower classes)"
− - "Single source, full connected load (no shedding required)"
−default: "Single source, priority load management (emergency first, shed lower classes)"
−```
−
−A single source with priority load management is the common arrangement for commercial and institutional buildings, because it lets one generator serve emergency, legally required standby, and optional standby loads while guaranteeing the emergency loads through a defined shed sequence. Dedicated sources per class are used where the classes must be physically independent — where, for example, an Article 700 system shall not depend on a source that also carries discretionary load. The load-shed and source-priority behavior shall be configured at the transfer switches per [[sync/automatic-transfer-switches]] and coordinated with the source capacity from [[sync/generators]].
−
−## Total Alternate-Source Capacity
−
−The total continuous capacity required of the alternate source shall be [[drawing: as indicated on the one-line diagram and load schedule]].
−
−```datasheet
−label: Total Alternate-Source Continuous Capacity
−type: range
−unit: kW
−drawing_ref: true
−options:
− min: 30
− max: 3000
− setpoints: [30, 60, 100, 150, 200, 300, 400, 500, 750, 1000, 1500, 2000, 3000]
−default: 500
−```
−
−The source capacity shall account for the largest motor or step load (typically a fire pump, elevator, or chiller), the step-load sequence as transfer switches close in priority order, and any nonlinear-load derating. The step-load and voltage-dip analysis is performed at the source and is required as a submittal under [[sync/generators]]; this standard requires only that the assigned load not exceed the source's demonstrated capacity at any step.
−
−## NFPA 110 Class (Runtime)
−
−```datasheet
−label: NFPA 110 Class — Minimum Runtime at Rated Load
−type: select
−options:
− - "Class 2 (2 hours)"
− - "Class 6 (6 hours)"
− - "Class 8 (8 hours)"
− - "Class 24 (24 hours)"
− - "Class 48 (48 hours)"
− - "Class 96 (96 hours)"
−default: "Class 8 (8 hours)"
−```
−
−The Class establishes the minimum time the system shall operate at rated load without refueling or recharging. The project Class shall be the larger of the value required by the Authority Having Jurisdiction and the value required by the served occupancy; healthcare facilities under NFPA 99 commonly require Class 96, while common commercial buildings often default to Class 8. The Class drives fuel storage at the generator (see [[sync/generators]]) or stored-energy capacity at the battery source (see [[sync/dc-battery-systems]]).
−
−# Transfer Scheme
−
−The transfer scheme is the set of decisions about how each load class is moved between the normal and alternate sources: how fast, by what kind of transfer, in what priority, and with what neutral treatment. The transfer switches themselves are specified per [[sync/automatic-transfer-switches]]; this standard sets the system-level requirements that those switches shall satisfy.
−
−## Required Transfer Time by Class
−
−The transfer time is fixed by the NEC article governing each load class and is not a free design choice. The system shall meet the most stringent transfer time among the classes it serves.
−
−```datasheet
−label: Required Transfer Time (governing class)
−type: select
−options:
− - "10 seconds — Article 700 emergency (NFPA 110 Type 10)"
− - "60 seconds — Article 701 legally required standby"
− - "No mandated time — Article 702 optional standby"
− - "Uninterruptible (0 seconds) — UPS-bridged critical load"
−default: "10 seconds — Article 700 emergency (NFPA 110 Type 10)"
−```
−
−For Article 700 emergency loads the total time from loss of normal source to restoration on the alternate source shall not exceed 10 seconds (NFPA 110 Type 10). For Article 701 legally required standby loads the limit is 60 seconds. A truly uninterruptible (Type U) transition cannot be achieved by a generator alone, which must crank, start, and stabilize before accepting load; an uninterruptible requirement shall be met by a UPS or battery source that bridges the engine-start interval, with the generator then carrying the load for the duration.
−
−## Transfer Switch Count and Segregation
−
−```datasheet
−label: Transfer Switch Segregation
−type: radio
−options:
− - "Separate transfer switch per load class (emergency / standby segregated)"
− - "Separate transfer switch per branch (life safety / critical / equipment)"
− - "Single transfer switch (single class, simple system)"
−default: "Separate transfer switch per load class (emergency / standby segregated)"
−```
−
−Emergency loads shall be served through transfer equipment separate from the lower-class loads so that the emergency portion can be wired independently per NEC 700.10 and so that a fault or maintenance action on a standby branch cannot affect the emergency branch. In healthcare facilities under NFPA 99, the essential electrical system is divided into the life-safety, critical, and equipment branches, each served by its own transfer switch. The number, ampere rating, and location of the transfer switches shall be [[drawing: as indicated on the one-line diagram and the equipment plans]].
−
−## Transfer Type and Neutral Treatment
−
−The transfer type (open, delayed, or closed transition) and the neutral treatment (3-pole solid neutral or 4-pole switched neutral) are system-level decisions that affect grounding and ground-fault sensing across the whole system, even though they are configured at each switch. Open transition is the default. A 4-pole switched-neutral arrangement, which makes the alternate source a separately derived system, is the safer default wherever the system has ground-fault protection on either source. These selections shall be made consistently across the system and are specified in detail per [[sync/automatic-transfer-switches]]; the resulting system bonding shall be coordinated through the grounding scheme and confirmed against the generator neutral treatment in [[sync/generators]].
−
−# Selective Coordination
−
−For emergency (700.32), legally required standby (701.32), and critical operations (708.54) systems, the overcurrent protective devices in the alternate-source path shall be selectively coordinated with all supply-side overcurrent devices, so that a fault on one branch is cleared by the device immediately upstream of the fault and does not open a device that would de-energize unaffected emergency or standby loads. Selective coordination is a mandatory code requirement for these classes — not a recommendation — and it constrains the choice and settings of every breaker and fuse from the source to the load.
−
−```datasheet
−label: Selective Coordination Required
−type: radio
−options:
− - "Required — Article 700 / 701 / 708 loads present (700.32 / 701.32 / 708.54)"
− - "Not required — Article 702 optional standby only"
−default: "Required — Article 700 / 701 / 708 loads present (700.32 / 701.32 / 708.54)"
−```
−
−The coordination shall be demonstrated by a study prepared per [[sync/protective-coordination-study]] and signed by a licensed Professional Engineer. The study shall use the available fault current at each point in the system, including the contribution of the alternate source, which differs from the utility contribution and shall be evaluated separately. Because coordination constrains device selection, the study shall be performed before the overcurrent devices are procured; retrofitting coordination after equipment is purchased commonly forces device replacement.
−
−```datasheet
−label: Coordination Time Boundary
−type: select
−unit: s
−options:
− - "Coordinated to 0.1 s (instantaneous region — most stringent)"
− - "Coordinated to 0.01 s (full instantaneous, fuse / current-limiting)"
− - "Coordinated above 0.1 s only (time-overcurrent region)"
−default: "Coordinated to 0.1 s (instantaneous region — most stringent)"
−```
−
−The NEC requirement for selective coordination has historically been interpreted to require coordination throughout the full range of overcurrents and operating times, including the instantaneous region. The coordination boundary selected here shall match the interpretation accepted by the Authority Having Jurisdiction and shall be documented in the study.
−
−# Wiring and Circuit Integrity
−
−## Article 700 Wiring Separation
−
−The wiring of an Article 700 emergency system shall be kept entirely independent of all other wiring and equipment per NEC 700.10(B), occupying its own raceways, cables, boxes, and cabinets, except at transfer equipment and at specifically permitted points. This separation prevents a fault or a maintenance action in the normal or standby wiring from disabling the emergency system. Legally required standby (Article 701) and optional standby (Article 702) wiring may share raceways and enclosures with general wiring.
−
−```datasheet
−label: Emergency Wiring Separation (Article 700)
−type: radio
−options:
− - "Fully independent raceways, boxes, and enclosures (NEC 700.10(B))"
− - "Not applicable (no Article 700 loads)"
−default: "Fully independent raceways, boxes, and enclosures (NEC 700.10(B))"
−```
−
−## Circuit Integrity and Survivability
−
−Where the building is a high-rise or otherwise requires feeder survivability, the emergency feeders shall maintain circuit integrity during fire exposure for the duration required by NEC 700.10(D) and the adopted building code, by means of a listed electrical circuit protective system, a 2-hour fire-rated assembly, or routing through a 2-hour fire-rated space, as accepted by the Authority Having Jurisdiction.
−
−```datasheet
−label: Emergency Feeder Circuit Integrity
−type: radio
−options:
− - "Not required (no survivability requirement)"
− - "2-hour fire-rated cable / circuit integrity system (high-rise per 700.10(D))"
− - "Routed in 2-hour fire-rated construction"
−default: "Not required (no survivability requirement)"
−```
−
−Conductor types, sizing, and raceway are specified at the conductor and raceway standards; this standard establishes only the system-level separation and survivability requirement. Where a stored-energy source is part of the system, its DC and inverter wiring shall be coordinated per [[sync/dc-battery-systems]].
−
−# System Monitoring and Annunciation
−
−The system shall annunciate its readiness and its alarm conditions at a location that is continuously attended, so that a failure of the system to be ready is detected before the next outage rather than during it. For NFPA 110 Level 1 systems, a remote annunciator displaying the required alarms shall be provided at a continuously monitored point, typically the fire command center, security desk, or building operations center. The annunciator and its supervised wiring are specified at the generator and transfer switch standards; this standard requires that the system as a whole present a single, coherent annunciation of readiness and alarms.
−
−```datasheet
−label: System Annunciation Location
−type: text
−drawing_ref: true
−default: "As indicated on the drawings (typically fire command center or 24-hour monitored station)"
−```
−
−```datasheet
−label: System Status Integration
−type: checkbox
−options:
− - "Remote annunciator at monitored location (NFPA 110 Level 1)"
− - "Building management system integration (status and alarms)"
− - "Source-running and on-alternate indication per transfer switch"
− - "Battery / stored-energy source status (where present)"
−default: "Remote annunciator at monitored location (NFPA 110 Level 1)"
−```
−
−# Testing and Commissioning
−
−## Integrated Acceptance Test
−
−After the individual components are commissioned, the Contractor shall perform an integrated system acceptance test per NFPA 110 Chapter 7 that verifies the complete chain — loss of normal source, source start, transfer of each load class within its required time, operation under load, restoration of normal source, retransfer, and source cool-down — as one system. The test shall not be a sum of component tests; it shall exercise the system the way an actual outage would, with the loads connected and the transfer switches operating in their commissioned priority and shed sequence.
−
−The integrated acceptance test shall include, at a minimum:
−
−- Simulated loss of normal source, with measurement of the total time from loss of normal to load energized on the alternate source for each class (10 seconds maximum for Article 700, 60 seconds maximum for Article 701)
−- Operation under load for the duration required by NFPA 110 Chapter 7, with the load-shed and source-priority sequence verified across multiple transfer switches
−- Verification that every emergency and legally required standby load is in fact transferred and energized
−- Simulated restoration of the normal source, with verification of retransfer timing and source cool-down
−- Verification of the system annunciation and alarms at the monitored location
−- For stored-energy egress sources, verification of the full required illumination duration (90 minutes) per NFPA 101
−
−```datasheet
−label: Integrated Acceptance Test Scope
−type: radio
−options:
− - "Full NFPA 110 Chapter 7 integrated test with building loads"
− - "Full NFPA 110 Chapter 7 test with supplemental load bank to rated capacity"
− - "Component tests only (Article 702 optional standby, no integrated requirement)"
−default: "Full NFPA 110 Chapter 7 test with supplemental load bank to rated capacity"
−```
−
−A supplemental load bank is recommended at acceptance because the connected building load at commissioning is usually well below the source's rated capacity, and a full-capacity test exercises the source, transfer, and cooling systems in a way that an under-loaded run cannot. The generator field test required by [[sync/generators]] and the transfer switch field test required by [[sync/automatic-transfer-switches]] shall be scheduled so that they roll up into this single integrated test.
−
−```datasheet
−label: Acceptance Test Witness
−type: radio
−options:
− - "Authority Having Jurisdiction witness required"
− - "Owner's commissioning agent witness"
− - "Engineer of Record witness"
− - "Test report certified by Contractor"
−default: "Authority Having Jurisdiction witness required"
−```
−
−For emergency and legally required standby systems the Authority Having Jurisdiction commonly witnesses the acceptance test, and a written, signed test record is required before the system is placed in service.
−
−## Periodic Testing and Maintenance
−
−The Owner shall maintain and periodically test the system per NFPA 110 Chapter 8 (and the maintenance provisions of the governing NEC article) for the life of the installation. Emergency and legally required standby systems require periodic testing and a written maintenance log as a code obligation; the testing intervals and recordkeeping format shall be documented in the closeout submittals and turned over to the Owner.
−
−```datasheet
−label: Periodic Test Interval
−type: select
−options:
− - "Monthly under load (min. 30 minutes) plus weekly inspection — NFPA 110 Ch. 8"
− - "Monthly under load plus annual full-duration/load-bank test"
− - "Per NEC 702 owner maintenance (optional standby — no mandated interval)"
−default: "Monthly under load (min. 30 minutes) plus weekly inspection — NFPA 110 Ch. 8"
−```
−
−NFPA 110 Chapter 8 requires weekly inspection and a monthly exercise under load of at least 30 minutes at a loading that maintains the manufacturer's recommended minimum exhaust-gas temperature for engine-generator sources. Where the monthly under-load test cannot be met by building load, or where a diesel set is chronically under-loaded, an annual load-bank test (commonly two continuous hours, stepped through the manufacturer's loading) shall be performed. Stored-energy egress sources shall be tested monthly (a short functional test) and annually (a full 90-minute discharge) per NFPA 101.
−
−# Identification and Labeling
−
−The components of an emergency system shall be marked as part of the emergency system per NEC 700.10(A) at each enclosure, and the system one-line and the served panelboards shall identify the source and class of the backed-up loads. The available fault current at the alternate source and at the load side of each transfer switch shall be calculated, labeled, and dated per NEC 110.24. Detailed equipment labeling at each component follows that component's standard; this element captures the system-level identification.
−
−```datasheet
−label: System Identification and Labeling
−type: checkbox
−options:
− - "Emergency system component marking per NEC 700.10(A)"
− - "Load class identification at served panelboards (700 / 701 / 702 / 708)"
− - "Source identification at each transfer switch (normal / alternate)"
− - "Available fault current label and date at alternate source and ATS load side (NEC 110.24)"
− - "Arc flash warning labels per NFPA 70E"
− - "NFPA 110 Level / Type / Class identification on system documentation"
−default: "Emergency system component marking per NEC 700.10(A)"
−```
−
−# Warranty
−
−```datasheet
−label: System Warranty Period
−type: select
−options:
− - "1 year from substantial completion"
− - "2 years from substantial completion (typical)"
− - "Per component warranties, coordinated to a common start date"
−default: "Per component warranties, coordinated to a common start date"
−```
−
−The system warranty shall coordinate the warranties of the individual components (generator, transfer switches, stored-energy sources) to a common commencement date so that the Owner is not tracking separate, staggered warranty periods on a single system. For emergency and legally required standby systems, the warranty shall include the emergency field-service response commitment established in the component standards (see [[sync/generators]] and [[sync/automatic-transfer-switches]]). Coverage shall extend to defects in materials and workmanship and to the system's failure to meet its commissioned transfer times under normal standby use.
+---
+title: Emergency and Standby Power Systems
+category: Electrical / Power Distribution Equipment
+toc_depth: 3
+description: >
+ When to use: System-level standard establishing the classification, source selection, load assignment, transfer scheme, overcurrent coordination, and acceptance testing for a building's emergency and standby power system, in accordance with NFPA 70 Articles 700 (Emergency Systems), 701 (Legally Required Standby), 702 (Optional Standby), and 708 (Critical Operations Power Systems), and NFPA 110 and NFPA 111. Use this standard to define what the system must do as a whole — which loads are emergency vs. standby, what alternate source serves them, how fast they transfer, and how they are commissioned and maintained. Component-level requirements are deferred to the equipment standards for the engine-generator set (see [[sync/generators]]), the automatic transfer switches (see [[sync/automatic-transfer-switches]]), and the stored-energy sources (see [[sync/dc-battery-systems]]).
+ Not intended for: Selection or sizing of an individual engine-generator set, transfer switch, battery, or UPS module (use the component standards), the project overcurrent selective coordination study itself (see [[sync/protective-coordination-study]]), normal-power distribution equipment, utility service entrance design, microgrid or utility-paralleled distributed generation operated for economic dispatch, or grid-tied photovoltaic and battery storage systems whose primary purpose is energy management rather than life-safety backup.
+---
+
+# Scope {toc}
+
+## This specification establishes the system-level requirements for a building's emergency and standby power system: the body of equipment and wiring that supplies electrical power to designated loads when the normal source fails. {note}
+## It defines how loads are classified, which alternate source serves each class of load, how the load is transferred between sources, how the overcurrent protective devices are coordinated, and how the complete system is commissioned, tested, and maintained. {note}
+
+## The standard is the umbrella under which the individual pieces of equipment are coordinated; it does not itself specify the construction of any one piece of equipment. {note}
+
+## Legal Weight {toc}
+
+### The legal weight of this system is unusual. {note}
+### For emergency systems under NFPA 70 (NEC) Article 700, the wiring, sources, and transfer equipment exist to protect human life during a power failure, and the requirements are correspondingly strict. {note}
+
+### The system shall be designed, installed, and commissioned as an integrated whole — the generator, the transfer switches, the stored-energy sources, the coordinated overcurrent devices, and the wiring that connects them are not independent scopes that happen to be in the same building.
+
+### A correctly sized generator behind a transfer switch that cannot transfer in time, or a correctly rated transfer switch fed by a feeder that is not coordinated, is a non-compliant system regardless of how good each component is in isolation. {note}
+
+## Coordination with Component Standards {toc}
+
+### This standard coordinates with and defers component detail to the engine-generator set (see [[sync/generators]]), the automatic transfer switches (see [[sync/automatic-transfer-switches]]), the stored-energy and battery sources (see [[sync/dc-battery-systems]]), and the overcurrent selective coordination study (see [[sync/protective-coordination-study]]). {note}
+
+### Where this standard and a component standard appear to conflict, the system-level intent stated here governs the coordination, and the component standard governs the construction of that component.
+
+## Exclusions {toc}
+
+### This standard does not establish the normal-power distribution, the utility service, or any source operated principally for economic dispatch or energy management. {note}
+### Distributed generation interconnected to the utility for parallel operation under IEEE 1547 is outside scope except where a closed-transition or paralleling alternate source is used solely to restore a backup function; those provisions are coordinated through [[sync/automatic-transfer-switches]] and [[sync/generators]]. {note}
+
+# Referenced Standards {toc}
+
+## Design, equipment, and installation shall comply with the latest adopted edition of the following.
+
+## Where the contract documents, the adopted building code, or a referenced standard conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+
+## Referenced Standards List {toc}
+
+| Standard | Title |
+|----------|-------|
+| NFPA 70 | National Electrical Code (Articles 700, 701, 702, 705, 708, 230, 250, 110) |
+| NFPA 110 | Standard for Emergency and Standby Power Systems |
+| NFPA 111 | Standard on Stored Electrical Energy Emergency and Standby Power Systems |
+| NFPA 101 | Life Safety Code (means of egress illumination) |
+| NFPA 99 | Health Care Facilities Code (where applicable) |
+| NFPA 70E | Standard for Electrical Safety in the Workplace |
+| IBC | International Building Code (egress illumination, seismic, importance factors) |
+| UL 924 | Emergency Lighting and Power Equipment |
+| UL 1008 | Transfer Switch Equipment |
+| UL 1778 | Uninterruptible Power Systems |
+| UL 2200 | Stationary Engine Generator Assemblies |
+| IEEE 446 | Recommended Practice for Emergency and Standby Power Systems for Industrial and Commercial Applications (Orange Book) |
+| IEEE 241 | Recommended Practice for Electric Power Systems in Commercial Buildings (Gray Book) |
+| IEEE 1547 | Standard for Interconnection and Interoperability of Distributed Energy Resources |
+| ASCE 7 | Minimum Design Loads and Associated Criteria for Buildings and Other Structures |
+| ICC ES AC156 | Acceptance Criteria for Seismic Certification by Shake-Table Testing |
+| ANSI/NETA ATS | Standard for Acceptance Testing Specifications for Electrical Power Equipment and Systems |
+
+# Submittals {toc}
+
+## Action Submittals {toc}
+
+### Contractor shall submit the following for the Engineer's review prior to procurement of system equipment:
+
+- System one-line diagram showing the normal source, each alternate source, every transfer switch, the load class served by each transfer switch, and the boundary between the emergency, legally required standby, and optional standby portions of the system, coordinated with [[drawing: the contract one-line diagram]]
+- Load schedule classifying each connected load as emergency (Article 700), legally required standby (Article 701), optional standby (Article 702), or critical operations (Article 708), with connected and demand kW/kVA for each class, coordinated with [[drawing: the contract load schedules]]
+- Alternate source capacity calculation demonstrating that each source can carry its assigned loads at the worst-case step and steady state, including the starting kVA and voltage-dip analysis from [[sync/generators]]
+- Transfer scheme narrative describing transfer type, time delays, source priority, and load-shed sequence for each transfer switch, consistent with [[sync/automatic-transfer-switches]]
+- NFPA 110 classification statement (Level, Type, and Class) for each portion of the system, with the basis for each selection
+- Selective coordination study confirming compliance with NEC 700.32, 701.32, and 708.54 as applicable, prepared per [[sync/protective-coordination-study]]
+- Wiring separation and circuit-integrity plan for the Article 700 emergency portion per NEC 700.10
+- Emergency illumination duration calculation demonstrating 90-minute egress illumination per NFPA 101 and the IBC for any stored-energy egress source
+- Integrated commissioning plan describing the system acceptance test per NFPA 110 Chapter 7
+
+```datasheet
+label: System-Level Action Submittals Required
+type: checkbox
+options:
+ - "System one-line with source/load-class boundaries"
+ - "Load schedule classified by NEC article (700/701/702/708)"
+ - "Alternate source capacity and step-load calculation"
+ - "Transfer scheme narrative (type, delays, priority, load shed)"
+ - "NFPA 110 Level/Type/Class classification statement"
+ - "Selective coordination study (700.32 / 701.32 / 708.54)"
+ - "Article 700 wiring separation and circuit-integrity plan"
+ - "Emergency illumination 90-minute duration calculation"
+ - "Integrated commissioning / acceptance test plan"
+default: "System one-line with source/load-class boundaries"
+```
+
+### Procurement of long-lead items shall not proceed until the system-level submittals establishing classification, source assignment, and transfer scheme have been reviewed and returned.
+
+## Closeout Submittals {toc}
+
+### Contractor shall provide the following at substantial completion before the system is accepted into emergency or standby service:
+
+- Signed and dated NFPA 110 integrated acceptance test record covering the complete normal-source / alternate-source / transfer chain
+- As-built system one-line and load schedule reflecting the installed configuration and the commissioned transfer settings
+- Final selective coordination study reflecting as-installed overcurrent device settings and ratings
+- Operation and maintenance manuals for the system, including the testing and maintenance schedule required by NFPA 110 Chapter 8
+- Written instructions to the Owner establishing the periodic testing intervals, the maintenance log format, and the recordkeeping obligations under the applicable NEC articles and NFPA 110
+- Owner training sign-off documenting system operation, source transfer behavior, and emergency response procedures
+
+```datasheet
+label: Required Closeout Submittals
+type: checkbox
+options:
+ - "NFPA 110 integrated acceptance test record (signed and dated)"
+ - "As-built system one-line and load schedule"
+ - "Final selective coordination study (as-installed settings)"
+ - "Operation and maintenance manuals (NFPA 110 Ch. 8 schedule)"
+ - "Written Owner instructions (test intervals, log format, recordkeeping)"
+ - "Owner training sign-off"
+default: [NFPA 110 integrated acceptance test record (signed and dated), As-built system one-line and load schedule, Final selective coordination study (as-installed settings), Operation and maintenance manuals (NFPA 110 Ch. 8 schedule), Written Owner instructions (test intervals, log format, recordkeeping), Owner training sign-off]
+```
+
+# Quality Assurance {toc}
+
+## Designer and System Integrator Qualifications {toc}
+
+### The system one-line, load classification, source capacity calculation, and selective coordination study shall be prepared by or under the responsible charge of a licensed Professional Engineer.
+
+### NEC 708.54 requires that the selective coordination of a critical operations power system be performed by a licensed Professional Engineer or other qualified person; this standard extends that expectation to the coordination study for Article 700 and 701 systems as well. {note}
+
+## System Integration Responsibility {toc}
+
+### A single party shall be responsible for demonstrating that the assembled system meets its NFPA 110 classification end to end.
+
+### Acceptance of the individual components (the generator startup, the transfer switch commissioning, the battery commissioning) does not constitute acceptance of the system; the integrated acceptance test under NFPA 110 Chapter 7 is what places the system in service. {note}
+
+## Testing Personnel Qualifications {toc}
+
+### Integrated system acceptance testing shall be performed by technicians certified by NETA, EGSA, or the equipment manufacturer's training program, with documented experience commissioning emergency power systems of comparable scope.
+
+### Personnel shall coordinate the generator field test (see [[sync/generators]]) and the transfer switch field test (see [[sync/automatic-transfer-switches]]) so that the chain is verified as one system.
+
+# Environmental and Service Conditions {toc}
+
+## System-level environmental conditions are established at the component standards. {note}
+
+## This standard requires only that the alternate source remain available during the same events that may cause the normal-source outage.
+
+## For life-safety systems in seismic, high-wind, or flood-prone regions, the source, its fuel or stored-energy supply, and its cooling shall not depend on a utility or infrastructure that is likely to fail in the same event.
+
+## A natural-gas-fueled generator tied to a utility gas supply, or a generator cooled by a domestic water main, may not satisfy this requirement for an Article 700 system; confirm the Authority Having Jurisdiction position before relying on a source whose continued operation depends on another utility.
+
+## Alternate Source Availability Basis {toc}
+
+```datasheet
+label: Alternate Source Availability Basis
+type: radio
+options:
+ - "On-site stored fuel or energy (independent of other utilities)"
+ - "Continuous utility fuel supply (natural gas / LP, with AHJ acceptance)"
+ - "Dual source (on-site stored plus utility supplement)"
+default: "On-site stored fuel or energy (independent of other utilities)"
+```
+
+# Load Classification {toc}
+
+## The first design decision is the classification of each connected load. {note}
+## Classification determines which NEC article governs the load, how fast it shall be restored, how its wiring shall be separated, and whether selective coordination is mandatory.
+
+## A load that is mis-classified — for example, a life-safety load assigned to an optional standby branch — produces a system that is non-compliant even if every piece of equipment performs perfectly. {note}
+
+## Article 700 — Emergency Systems {toc}
+
+### Emergency systems supply loads whose failure could cause loss of human life or serious injury: egress and exit illumination, exit signage, fire alarm and detection, fire pumps where designated, smoke control, elevators required for egress, and life-support and similar loads in occupancies that require them. {note}
+
+### Emergency systems shall restore power to their loads within 10 seconds of normal-source failure (NEC 700.12).
+
+### The wiring of emergency systems shall be kept entirely independent of all other wiring per NEC 700.10(B).
+
+### The overcurrent devices of emergency systems shall be selectively coordinated per NEC 700.32.
+
+## Article 701 — Legally Required Standby Systems {toc}
+
+### Legally required standby systems supply loads that the adopted code or the Authority Having Jurisdiction requires to be backed up but whose failure does not immediately endanger life: heating and ventilation for habitability, sewage and stormwater pumping, certain communications, and industrial processes whose interruption creates a hazard. {note}
+
+### Legally required standby systems shall restore power within 60 seconds (NEC 701.12).
+
+### Legally required standby systems may share raceways and enclosures with general wiring.
+
+### Legally required standby systems shall be selectively coordinated per NEC 701.32.
+
+## Article 702 — Optional Standby Systems {toc}
+
+### Optional standby systems supply loads that the Owner elects to back up for convenience, comfort, or economic continuity, where life safety does not depend on the system: data processing, refrigeration, general lighting and receptacles, and similar loads. {note}
+
+### Optional standby systems have no code-mandated transfer time, no mandatory wiring separation, and no mandatory selective coordination; their performance is set by the Owner's continuity requirements.
+
+## Article 708 — Critical Operations Power Systems {toc}
+
+### Critical operations power systems supply designated critical operations areas (DCOA) in facilities whose loss would disrupt national security, the economy, or public safety, as designated by a governmental authority or by the facility's own engineering documentation. {note}
+
+### COPS shall have full selective coordination of all overcurrent devices supplying COPS loads per NEC 708.54, enhanced commissioning, and documented maintenance.
+
+### Apply Article 708 only where the load has been formally designated; it is not a default for ordinary critical loads. {note}
+
+## System Classes Present {toc}
+
+```datasheet
+label: System Classes Present on This Project
+type: checkbox
+options:
+ - "Article 700 — Emergency (life safety, 10 s transfer)"
+ - "Article 701 — Legally Required Standby (60 s transfer)"
+ - "Article 702 — Optional Standby (Owner continuity)"
+ - "Article 708 — Critical Operations Power System (designated DCOA)"
+default: "Article 700 — Emergency (life safety, 10 s transfer)"
+```
+
+### The classification of each individual load shall be [[drawing: as indicated on the load schedule and panel schedules]].
+
+### Where a single building contains more than one class, the system shall maintain the separation and priority appropriate to the highest class present.
+
+# Source Selection {toc}
+
+## Alternate Source Type {toc}
+
+### The engine-generator set is the default alternate source for systems whose loads exceed the practical limit of a stored-energy source and whose required runtime exceeds the runtime achievable from batteries. {note}
+### Stored-energy sources (battery/inverter, central battery egress equipment, or UPS) are appropriate where the load is small, where a zero-interruption transition is required, or where the only emergency load is egress illumination. {note}
+### Many systems use both: a generator for the bulk of the standby load and a stored-energy source to bridge the engine-start interval for loads that cannot tolerate the 10-second gap. {note}
+
+```datasheet
+label: Primary Alternate Source
+type: radio
+options:
+ - "Engine-generator set (see component standard)"
+ - "Stored-energy: central battery / inverter egress equipment (UL 924)"
+ - "Stored-energy: uninterruptible power supply (UPS, UL 1778)"
+ - "Generator plus UPS (UPS bridges engine-start interval)"
+ - "Fuel cell (continuous, with AHJ acceptance)"
+default: "Engine-generator set (see component standard)"
+```
+
+### The alternate source shall be selected to match the load class, the required transfer time, and the required runtime.
+
+### The engine-generator set, where used, shall be specified per [[sync/generators]].
+
+### The stored-energy source, where used, shall be specified per [[sync/dc-battery-systems]] and applied per NFPA 111.
+
+### This standard establishes which source serves which load and what each source shall accomplish; the construction of each source is set by its component standard. {note}
+
+## Stored-Energy Source for Egress Illumination {toc}
+
+### Where egress illumination is supplied by a stored-energy source rather than a generator, the source shall provide not less than 90 minutes of the required illumination per NFPA 101 and the IBC.
+
+### Where egress illumination is supplied by a stored-energy source, the equipment shall be UL 924 listed for emergency service.
+
+### The 90-minute duration is the controlling sizing parameter for a battery or inverter egress source and shall be demonstrated by calculation in the submittal.
+
+## Egress Illumination Source Selection {toc}
+
+```datasheet
+label: Egress Illumination Source
+type: radio
+options:
+ - "Generator-backed emergency lighting (transfer within 10 s)"
+ - "Central battery / inverter unit (UL 924, 90-minute)"
+ - "Distributed unit equipment (UL 924 fixtures with integral battery, 90-minute)"
+ - "Generator plus unit equipment (defense in depth)"
+default: "Generator-backed emergency lighting (transfer within 10 s)"
+```
+
+```datasheet
+label: Emergency Illumination Duration
+type: select
+unit: min
+options:
+ - "90 minutes (NFPA 101 / IBC egress minimum)"
+ - "120 minutes (extended, per AHJ or owner)"
+ - "Generator-backed (duration set by fuel Class, not battery)"
+default: "90 minutes (NFPA 101 / IBC egress minimum)"
+```
+
+## Source Redundancy {toc}
+
+```datasheet
+label: Source Redundancy
+type: radio
+options:
+ - "Single alternate source (N) — typical"
+ - "N+1 redundant sources (one spare source)"
+ - "2N fully redundant sources (independent A/B)"
+default: "Single alternate source (N) — typical"
+```
+
+### A single alternate source is the default for most buildings. {note}
+### Redundant sources are appropriate where the load cannot tolerate the loss of the alternate source during maintenance or a single source failure — typically hospitals, data centers, and Article 708 facilities. {note}
+
+### Source redundancy is a system decision that drives the number of generators, the paralleling scheme, and the number and bypass construction of the transfer switches; it shall be resolved before the component standards are applied.
+
+# Load Assignment and Sizing {toc}
+
+## The alternate source shall be sized for the connected load it serves at the worst-case starting step and at steady state, with the load assigned to the source according to its class.
+
+## Where one source serves more than one class — a single generator serving both emergency and standby loads, for example — the emergency loads shall have priority and the lower-class loads shall be shed if the source approaches capacity.
+
+## Load Assignment Method {toc}
+
+```datasheet
+label: Load Assignment Method
+type: radio
+options:
+ - "Dedicated source per class (separate source for emergency vs. standby)"
+ - "Single source, priority load management (emergency first, shed lower classes)"
+ - "Single source, full connected load (no shedding required)"
+default: "Single source, priority load management (emergency first, shed lower classes)"
+```
+
+### A single source with priority load management is the common arrangement for commercial and institutional buildings, because it lets one generator serve emergency, legally required standby, and optional standby loads while guaranteeing the emergency loads through a defined shed sequence. {note}
+### Dedicated sources per class are used where the classes must be physically independent — where, for example, an Article 700 system shall not depend on a source that also carries discretionary load.
+
+### The load-shed and source-priority behavior shall be configured at the transfer switches per [[sync/automatic-transfer-switches]] and coordinated with the source capacity from [[sync/generators]].
+
+## Total Alternate-Source Capacity {toc}
+
+```datasheet
+label: Total Alternate-Source Continuous Capacity
+type: range
+unit: kW
+drawing_ref: true
+options:
+ min: 30
+ max: 3000
+ setpoints: [30, 60, 100, 150, 200, 300, 400, 500, 750, 1000, 1500, 2000, 3000]
+default: 500
+```
+
+### The total continuous capacity required of the alternate source shall be [[drawing: as indicated on the one-line diagram and load schedule]].
+
+### The source capacity shall account for the largest motor or step load (typically a fire pump, elevator, or chiller), the step-load sequence as transfer switches close in priority order, and any nonlinear-load derating.
+
+### The step-load and voltage-dip analysis is performed at the source and is required as a submittal under [[sync/generators]]; this standard requires only that the assigned load not exceed the source's demonstrated capacity at any step.
+
+## NFPA 110 Class (Runtime) {toc}
+
+```datasheet
+label: NFPA 110 Class — Minimum Runtime at Rated Load
+type: select
+options:
+ - "Class 2 (2 hours)"
+ - "Class 6 (6 hours)"
+ - "Class 8 (8 hours)"
+ - "Class 24 (24 hours)"
+ - "Class 48 (48 hours)"
+ - "Class 96 (96 hours)"
+default: "Class 8 (8 hours)"
+```
+
+### The Class establishes the minimum time the system shall operate at rated load without refueling or recharging.
+
+### The project Class shall be the larger of the value required by the Authority Having Jurisdiction and the value required by the served occupancy.
+
+### Healthcare facilities under NFPA 99 commonly require Class 96, while common commercial buildings often default to Class 8. {note}
+
+### The Class drives fuel storage at the generator (see [[sync/generators]]) or stored-energy capacity at the battery source (see [[sync/dc-battery-systems]]). {note}
+
+# Transfer Scheme {toc}
+
+## The transfer scheme is the set of decisions about how each load class is moved between the normal and alternate sources: how fast, by what kind of transfer, in what priority, and with what neutral treatment. {note}
+
+## The transfer switches themselves are specified per [[sync/automatic-transfer-switches]]; this standard sets the system-level requirements that those switches shall satisfy. {note}
+
+## Required Transfer Time by Class {toc}
+
+```datasheet
+label: Required Transfer Time (governing class)
+type: select
+options:
+ - "10 seconds — Article 700 emergency (NFPA 110 Type 10)"
+ - "60 seconds — Article 701 legally required standby"
+ - "No mandated time — Article 702 optional standby"
+ - "Uninterruptible (0 seconds) — UPS-bridged critical load"
+default: "10 seconds — Article 700 emergency (NFPA 110 Type 10)"
+```
+
+### The transfer time is fixed by the NEC article governing each load class and is not a free design choice.
+
+### The system shall meet the most stringent transfer time among the classes it serves.
+
+### For Article 700 emergency loads the total time from loss of normal source to restoration on the alternate source shall not exceed 10 seconds (NFPA 110 Type 10).
+
+### For Article 701 legally required standby loads the limit is 60 seconds.
+
+### A truly uninterruptible (Type U) transition cannot be achieved by a generator alone, which must crank, start, and stabilize before accepting load; an uninterruptible requirement shall be met by a UPS or battery source that bridges the engine-start interval, with the generator then carrying the load for the duration.
+
+## Transfer Switch Count and Segregation {toc}
+
+```datasheet
+label: Transfer Switch Segregation
+type: radio
+options:
+ - "Separate transfer switch per load class (emergency / standby segregated)"
+ - "Separate transfer switch per branch (life safety / critical / equipment)"
+ - "Single transfer switch (single class, simple system)"
+default: "Separate transfer switch per load class (emergency / standby segregated)"
+```
+
+### Emergency loads shall be served through transfer equipment separate from the lower-class loads so that the emergency portion can be wired independently per NEC 700.10 and so that a fault or maintenance action on a standby branch cannot affect the emergency branch.
+
+### In healthcare facilities under NFPA 99, the essential electrical system is divided into the life-safety, critical, and equipment branches, each served by its own transfer switch. {note}
+
+### The number, ampere rating, and location of the transfer switches shall be [[drawing: as indicated on the one-line diagram and the equipment plans]].
+
+## Transfer Type and Neutral Treatment {toc}
+
+### The transfer type (open, delayed, or closed transition) and the neutral treatment (3-pole solid neutral or 4-pole switched neutral) are system-level decisions that affect grounding and ground-fault sensing across the whole system, even though they are configured at each switch. {note}
+
+### Open transition is the default.
+
+### A 4-pole switched-neutral arrangement, which makes the alternate source a separately derived system, is the safer default wherever the system has ground-fault protection on either source.
+
+### These selections shall be made consistently across the system and are specified in detail per [[sync/automatic-transfer-switches]]; the resulting system bonding shall be coordinated through the grounding scheme and confirmed against the generator neutral treatment in [[sync/generators]].
+
+# Selective Coordination {toc}
+
+## For emergency (700.32), legally required standby (701.32), and critical operations (708.54) systems, the overcurrent protective devices in the alternate-source path shall be selectively coordinated with all supply-side overcurrent devices, so that a fault on one branch is cleared by the device immediately upstream of the fault and does not open a device that would de-energize unaffected emergency or standby loads.
+
+## Selective coordination is a mandatory code requirement for these classes — not a recommendation — and it constrains the choice and settings of every breaker and fuse from the source to the load. {note}
+
+## Selective Coordination Requirement {toc}
+
+```datasheet
+label: Selective Coordination Required
+type: radio
+options:
+ - "Required — Article 700 / 701 / 708 loads present (700.32 / 701.32 / 708.54)"
+ - "Not required — Article 702 optional standby only"
+default: "Required — Article 700 / 701 / 708 loads present (700.32 / 701.32 / 708.54)"
+```
+
+### The coordination shall be demonstrated by a study prepared per [[sync/protective-coordination-study]] and signed by a licensed Professional Engineer.
+
+### The study shall use the available fault current at each point in the system, including the contribution of the alternate source, which differs from the utility contribution and shall be evaluated separately.
+
+### Because coordination constrains device selection, the study shall be performed before the overcurrent devices are procured; retrofitting coordination after equipment is purchased commonly forces device replacement.
+
+## Coordination Time Boundary {toc}
+
+```datasheet
+label: Coordination Time Boundary
+type: select
+unit: s
+options:
+ - "Coordinated to 0.1 s (instantaneous region — most stringent)"
+ - "Coordinated to 0.01 s (full instantaneous, fuse / current-limiting)"
+ - "Coordinated above 0.1 s only (time-overcurrent region)"
+default: "Coordinated to 0.1 s (instantaneous region — most stringent)"
+```
+
+### The NEC requirement for selective coordination has historically been interpreted to require coordination throughout the full range of overcurrents and operating times, including the instantaneous region. {note}
+
+### The coordination boundary selected here shall match the interpretation accepted by the Authority Having Jurisdiction and shall be documented in the study.
+
+# Wiring and Circuit Integrity {toc}
+
+## Article 700 Wiring Separation {toc}
+
+### The wiring of an Article 700 emergency system shall be kept entirely independent of all other wiring and equipment per NEC 700.10(B), occupying its own raceways, cables, boxes, and cabinets, except at transfer equipment and at specifically permitted points.
+
+### This separation prevents a fault or a maintenance action in the normal or standby wiring from disabling the emergency system. {note}
+
+### Legally required standby (Article 701) and optional standby (Article 702) wiring may share raceways and enclosures with general wiring.
+
+## Emergency Wiring Separation Selection {toc}
+
+```datasheet
+label: Emergency Wiring Separation (Article 700)
+type: radio
+options:
+ - "Fully independent raceways, boxes, and enclosures (NEC 700.10(B))"
+ - "Not applicable (no Article 700 loads)"
+default: "Fully independent raceways, boxes, and enclosures (NEC 700.10(B))"
+```
+
+## Circuit Integrity and Survivability {toc}
+
+### Where the building is a high-rise or otherwise requires feeder survivability, the emergency feeders shall maintain circuit integrity during fire exposure for the duration required by NEC 700.10(D) and the adopted building code, by means of a listed electrical circuit protective system, a 2-hour fire-rated assembly, or routing through a 2-hour fire-rated space, as accepted by the Authority Having Jurisdiction.
+
+## Emergency Feeder Circuit Integrity Selection {toc}
+
+```datasheet
+label: Emergency Feeder Circuit Integrity
+type: radio
+options:
+ - "Not required (no survivability requirement)"
+ - "2-hour fire-rated cable / circuit integrity system (high-rise per 700.10(D))"
+ - "Routed in 2-hour fire-rated construction"
+default: "Not required (no survivability requirement)"
+```
+
+### Conductor types, sizing, and raceway are specified at the conductor and raceway standards; this standard establishes only the system-level separation and survivability requirement.
+
+### Where a stored-energy source is part of the system, its DC and inverter wiring shall be coordinated per [[sync/dc-battery-systems]].
+
+# System Monitoring and Annunciation {toc}
+
+## The system shall annunciate its readiness and its alarm conditions at a location that is continuously attended, so that a failure of the system to be ready is detected before the next outage rather than during it.
+
+## For NFPA 110 Level 1 systems, a remote annunciator displaying the required alarms shall be provided at a continuously monitored point, typically the fire command center, security desk, or building operations center.
+
+## The annunciator and its supervised wiring are specified at the generator and transfer switch standards; this standard requires that the system as a whole present a single, coherent annunciation of readiness and alarms.
+
+## System Annunciation Configuration {toc}
+
+```datasheet
+label: System Annunciation Location
+type: text
+drawing_ref: true
+default: "As indicated on the drawings (typically fire command center or 24-hour monitored station)"
+```
+
+```datasheet
+label: System Status Integration
+type: checkbox
+options:
+ - "Remote annunciator at monitored location (NFPA 110 Level 1)"
+ - "Building management system integration (status and alarms)"
+ - "Source-running and on-alternate indication per transfer switch"
+ - "Battery / stored-energy source status (where present)"
+default: "Remote annunciator at monitored location (NFPA 110 Level 1)"
+```
+
+# Testing and Commissioning {toc}
+
+## Integrated Acceptance Test {toc}
+
+### After the individual components are commissioned, the Contractor shall perform an integrated system acceptance test per NFPA 110 Chapter 7 that verifies the complete chain — loss of normal source, source start, transfer of each load class within its required time, operation under load, restoration of normal source, retransfer, and source cool-down — as one system.
+
+### The test shall not be a sum of component tests; it shall exercise the system the way an actual outage would, with the loads connected and the transfer switches operating in their commissioned priority and shed sequence.
+
+## Integrated Acceptance Test Minimum Scope {toc}
+
+### The integrated acceptance test shall include, at a minimum:
+
+- Simulated loss of normal source, with measurement of the total time from loss of normal to load energized on the alternate source for each class (10 seconds maximum for Article 700, 60 seconds maximum for Article 701)
+- Operation under load for the duration required by NFPA 110 Chapter 7, with the load-shed and source-priority sequence verified across multiple transfer switches
+- Verification that every emergency and legally required standby load is in fact transferred and energized
+- Simulated restoration of the normal source, with verification of retransfer timing and source cool-down
+- Verification of the system annunciation and alarms at the monitored location
+- For stored-energy egress sources, verification of the full required illumination duration (90 minutes) per NFPA 101
+
+```datasheet
+label: Integrated Acceptance Test Scope
+type: radio
+options:
+ - "Full NFPA 110 Chapter 7 integrated test with building loads"
+ - "Full NFPA 110 Chapter 7 test with supplemental load bank to rated capacity"
+ - "Component tests only (Article 702 optional standby, no integrated requirement)"
+default: "Full NFPA 110 Chapter 7 test with supplemental load bank to rated capacity"
+```
+
+### A supplemental load bank is recommended at acceptance because the connected building load at commissioning is usually well below the source's rated capacity, and a full-capacity test exercises the source, transfer, and cooling systems in a way that an under-loaded run cannot. {note}
+
+### The generator field test required by [[sync/generators]] and the transfer switch field test required by [[sync/automatic-transfer-switches]] shall be scheduled so that they roll up into this single integrated test.
+
+## Acceptance Test Witness {toc}
+
+```datasheet
+label: Acceptance Test Witness
+type: radio
+options:
+ - "Authority Having Jurisdiction witness required"
+ - "Owner's commissioning agent witness"
+ - "Engineer of Record witness"
+ - "Test report certified by Contractor"
+default: "Authority Having Jurisdiction witness required"
+```
+
+### For emergency and legally required standby systems the Authority Having Jurisdiction commonly witnesses the acceptance test, and a written, signed test record is required before the system is placed in service.
+
+## Periodic Testing and Maintenance {toc}
+
+### The Owner shall maintain and periodically test the system per NFPA 110 Chapter 8 (and the maintenance provisions of the governing NEC article) for the life of the installation.
+
+### Emergency and legally required standby systems require periodic testing and a written maintenance log as a code obligation; the testing intervals and recordkeeping format shall be documented in the closeout submittals and turned over to the Owner.
+
+## Periodic Test Interval Selection {toc}
+
+```datasheet
+label: Periodic Test Interval
+type: select
+options:
+ - "Monthly under load (min. 30 minutes) plus weekly inspection — NFPA 110 Ch. 8"
+ - "Monthly under load plus annual full-duration/load-bank test"
+ - "Per NEC 702 owner maintenance (optional standby — no mandated interval)"
+default: "Monthly under load (min. 30 minutes) plus weekly inspection — NFPA 110 Ch. 8"
+```
+
+### NFPA 110 Chapter 8 requires weekly inspection and a monthly exercise under load of at least 30 minutes at a loading that maintains the manufacturer's recommended minimum exhaust-gas temperature for engine-generator sources.
+
+### Where the monthly under-load test cannot be met by building load, or where a diesel set is chronically under-loaded, an annual load-bank test (commonly two continuous hours, stepped through the manufacturer's loading) shall be performed.
+
+### Stored-energy egress sources shall be tested monthly (a short functional test) and annually (a full 90-minute discharge) per NFPA 101.
+
+# Identification and Labeling {toc}
+
+## The components of an emergency system shall be marked as part of the emergency system per NEC 700.10(A) at each enclosure, and the system one-line and the served panelboards shall identify the source and class of the backed-up loads.
+
+## The available fault current at the alternate source and at the load side of each transfer switch shall be calculated, labeled, and dated per NEC 110.24.
+
+## Detailed equipment labeling at each component follows that component's standard; this element captures the system-level identification. {note}
+
+## System Identification and Labeling Selection {toc}
+
+```datasheet
+label: System Identification and Labeling
+type: checkbox
+options:
+ - "Emergency system component marking per NEC 700.10(A)"
+ - "Load class identification at served panelboards (700 / 701 / 702 / 708)"
+ - "Source identification at each transfer switch (normal / alternate)"
+ - "Available fault current label and date at alternate source and ATS load side (NEC 110.24)"
+ - "Arc flash warning labels per NFPA 70E"
+ - "NFPA 110 Level / Type / Class identification on system documentation"
+default: "Emergency system component marking per NEC 700.10(A)"
+```
+
+# Warranty {toc}
+
+```datasheet
+label: System Warranty Period
+type: select
+options:
+ - "1 year from substantial completion"
+ - "2 years from substantial completion (typical)"
+ - "Per component warranties, coordinated to a common start date"
+default: "Per component warranties, coordinated to a common start date"
+```
+
+## The system warranty shall coordinate the warranties of the individual components (generator, transfer switches, stored-energy sources) to a common commencement date so that the Owner is not tracking separate, staggered warranty periods on a single system.
+
+## For emergency and legally required standby systems, the warranty shall include the emergency field-service response commitment established in the component standards (see [[sync/generators]] and [[sync/automatic-transfer-switches]]).
+
+## Coverage shall extend to defects in materials and workmanship and to the system's failure to meet its commissioned transfer times under normal standby use.