UFC 3-520-01

16 January 2025

UNIFIED FACILITIES CRITERIA (UFC)

APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED

INTERIOR ELECTRICAL SYSTEMS

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UNIFIED FACILITIES CRITERIA (UFC)

INTERIOR ELECTRICAL SYSTEMS

Any copyrighted material included in this UFC is identified at its point of use.

Use of the copyrighted material apart from this UFC must have the permission of the copyright holder.

Indicate the Military Department Preparing Activity responsible for the document.

U.S. ARMY CORPS OF ENGINEERS

NAVAL FACILITIES ENGINEERING SYSTEMS COMMAND (Preparing Activity)

AIR FORCE CIVIL ENGINEER CENTER

Record of Changes (changes are indicated by \1\ ... /1/)

Change No. Date Location

This UFC supersedes UFC 3-520-01, dated 06 October 2015.

FOREWORD

The Unified Facilities Criteria (UFC) system is prescribed by MIL-STD 3007 and provides planning, design, construction, sustainment, restoration, and modernization criteria, and applies to the Military Departments, the Defense Agencies, and the DoD Field Activities in accordance with USD (AT&L) Memorandum dated 29 May 2002. UFC will be used for all DoD projects and work for other customers where appropriate. All construction outside of the United States, its territories, and possessions is also governed by Status of Forces Agreements (SOFA), Host Nation Funded Construction Agreements (HNFA), and in some instances, Bilateral Infrastructure Agreements (BIA). Therefore, the acquisition team must ensure compliance with the most stringent of the UFC, the SOFA, the HNFA, and the BIA, as applicable.

UFC are living documents and will be periodically reviewed, updated, and made available to users as part of the Military Department’s responsibility for providing technical criteria for military construction. Headquarters, U.S. Army Corps of Engineers (HQUSACE), Naval Facilities Engineering Systems Command (NAVFAC), and Air Force Civil Engineer Center (AFCEC) are responsible for administration of the UFC system. Technical content of UFC is the responsibility of the cognizant DoD working group. Defense Agencies should contact the respective DoD Working Group for document interpretation and improvements. Recommended changes with supporting rationale may be sent to the respective DoD working group by submitting a Criteria Change Request (CCR) via the Internet site listed below.

UFC are effective upon issuance and are distributed only in electronic media from the following source:

• Whole Building Design Guide website https://www.wbdg.org/dod.

Refer to UFC 1-200-01, DoD Building Code, for implementation of new issuances on projects.

AUTHORIZED BY:

THOMAS P. SMITH, P.E., SES

Chief, Engineering and Construction U.S. Army Corps of Engineers

S. KEITH HAMILTON, P.E., SES

Chief Engineer and Assistant Commander Planning, Design and Construction Naval Facilities Engineering Systems Command

THOMAS P. BROWN, SES

Deputy Director of Civil Engineers DCS/Logistics, Engineering & Force Protection (HAF/A4C) HQ United States Air Force

MARK S. SINDER, SES

Deputy Assistant Secretary of Defense (Infrastructure Modernization and Resilience) Office of the Secretary of Defense http://www.wbdg.org/pdfs/ufc_implementation.pdf https://www.wbdg.org/dod i

TABLE OF CONTENTS

CHAPTER 1 INTRODUCTION

1-1 PURPOSE AND SCOPE

1-2 REISSUES AND CANCELS

1-3 APPLICABILITY

1-3.1 UFC Scope

1-3.2 Host Nation Standards

1-4 GENERAL BUILDING REQUIREMENTS

1-5 CYBERSECURITY

1-6 DESIGN STANDARDS

1-7 GLOSSARY

1-8 REFERENCES

CHAPTER 2 GENERAL POWER SYSTEM CRITERIA

2-1 VOLTAGE

2-2 FREQUENCY

CHAPTER 3 POWER DISTRIBUTION AND UTILIZATION

3-1 TRANSFORMERS

3-1.1 Low Voltage Transformers

3-1.2 Other Transformer Types

3-2 SERVICE ENTRANCE AND DISTRIBUTION EQUIPMENT

3-2.1 Spare Capacity

3-2.2 Selection

3-2.3 Switchgear

3-2.4 Switchboards

3-2.5 Panelboards

3-2.6 Motor Control Centers (MCCs)

3-2.7 Power for Fire Protection Systems

3-2.8 Disconnect Switches

3-2.9 Circuit Lockout Requirements

3-2.10 Signage

3-2.11 Interrupting Ratings

3-2.12 Load Balancing by Phase ii

3-2.13 Adjustable Trip Devices

3-3 MOTORS AND MOTOR CONTROL CIRCUITS

3-3.1 Basic Motor Criteria

3-3.2 Motor Control Circuits

3-4 SURGE PROTECTIVE DEVICES (SPDS)

3-4.1 Power System Surge Protection

3-4.2 Surge Protection for Communications and Related Systems

3-4.3 Acceptance Tests

3-5 METERING

3-6 RACEWAY AND WIRING

3-6.1 Wiring Devices

3-6.2 Cable and Raceway Criteria

3-6.3 Conductors

3-6.4 Wiring Annotation

3-7 LIGHTING

3-8 GENERATORS

3-9 AUTOMATIC TRANSFER EQUIPMENT

3-10 UNINTERRUPTIBLE POWER SUPPLY

3-11 STATIONARY BATTERIES AND BATTERY CHARGERS

3-11.1 Selection

3-11.2 Battery Areas and Battery Racks

3-11.3 Installation Design

3-12 GROUNDING, BONDING, AND STATIC PROTECTION

3-12.1 Ground Rods

3-12.2 Ground Rings

3-12.3 Communication-Electronics Facilities

3-12.4 Static Electricity Protection

3-12.5 Aircraft Hangars

3-12.6 Ammunition and Explosive Storage Magazines

3-13 LIGHTNING PROTECTION SYSTEMS

3-14 400-HERTZ DISTRIBUTION SYSTEMS

3-15 270-VOLT DC DISTRIBUTION SYSTEMS

iii

3-16 POWER FACTOR CORRECTION

3-17 POWER QUALITY

3-18 SYSTEMS FURNITURE

3-18.1 Planning

3-18.2 Design

3-19 ASHRAE COMPLIANCE

3-20 ELECTRIC VEHICLE SUPPLY EQUIPMENT

3-20.1 Site and Equipment Considerations

APPENDIX A ADJUSTABLE SPEED DRIVES

A-1 ADJUSTABLE SPEED DRIVES (ASD)

A-1.1 ASD Sizing

A-1.2 Motor Considerations

A-1.3 Power Quality

A-1.4 Capacitor Switching Effects

A-1.5 Bypass Capability

APPENDIX B POWER QUALITY

B-1 INTRODUCTION

B-2 UNBALANCED VOLTAGES

B-2.1 Calculation

B-2.2 Effect on Motors

B-3 HARMONIC DISTORTION EVALUATION

B-4 DERATING TRANSFORMERS FOR HARMONIC CURRENT EFFECTS.

B-5 NONLINEAR LOAD DESIGN CONSIDERATIONS

B-6 NEUTRAL CIRCUIT SIZING FOR NONLINEAR LOAD CONDITIONS. . 43

APPENDIX C GLOSSARY

C-1 ACRONYMS

C-2 DEFINITION OF TERMS

APPENDIX D REFERENCES

iv

FIGURES

Figure B-1 Typical Derating Factor for Three-Phase Induction Motors

TABLES

Table 3-1 Authorized Cable and Raceway Types

CHAPTER 1 INTRODUCTION

1-1 PURPOSE AND SCOPE.

This Unified Facilities Criteria (UFC) has been issued to provide guidance for the design of interior electrical systems. The criteria contained herein are intended to ensure economical, durable, efficient, and reliable systems and installations. Whenever unique conditions and problems are not specifically covered by this UFC, use the applicable referenced industry standards and other documents for design guidance.

UFC 3-501-01 provides the governing criteria for electrical systems, explains the delineation between the different electrical-related UFCs, and refers to UFC 3-520-01 for interior electrical system requirements. Modernization of electrical systems within existing facilities solely for the purpose of meeting design criteria in this UFC is not required. Upgrades or modifications of existing facilities must apply the design criteria in this UFC, but it is not intended that an entire facility require modernization solely because of a minor modification to a part of the facility.

1-2 REISSUES AND CANCELS.

This UFC reissues and cancels UFC 3-520-01, dated 06 October 2015.

1-3 APPLICABILITY.

This UFC applies to planning, design, construction, sustainment, restoration, and modernization of DoD-owned facilities. It applies to all methods of project delivery and levels of construction as defined by UFC 1-200-01, Section 1-3.

1-3.1 UFC Scope.

Compliance with this UFC is mandatory for the design of interior electrical systems at all facilities and bases. This UFC typically applies up to 5 feet beyond the facility envelope.

It also applies to:

• Service(s) supplying power from the utility system utilization transformer to the wiring system of the facility.

• Circuits originating from within the facility that extend beyond the facility envelope.

• Wiring and connections for supplemental grounding systems.

• Wiring from and connections to non-utility equipment supplying power to the wiring system of the facility, including engine-generator sets, photovoltaic power systems and fuel cells.

Refer to UFC 3-550-01 for exterior electrical systems.

1-3.2 Host Nation Standards.

In addition to NFPA 70 requirements, facilities located outside of the United States must also comply with the applicable host nation standards. Host nation voltage and frequency as defined in UFC 3-510-01 generally applies. Different wiring and grounding conventions usually apply in other host nations; however, follow the design principles provided in this UFC to the extent practical.

1-4 GENERAL BUILDING REQUIREMENTS.

Comply with UFC 1-200-01, DoD Building Code. UFC 1-200-01 provides applicability of model building codes and government unique criteria for typical design disciplines and building systems, as well as for accessibility, antiterrorism, security, high performance and sustainability requirements, and safety. Use this UFC in addition to UFC 1-200-01 and the UFCs and government criteria referenced therein.

1-5 CYBERSECURITY.

All facility-related control systems (including systems separate from a utility monitoring and control system) must be planned, designed, acquired, executed, and maintained in accordance with UFC 4-010-06, and as required by individual Service Implementation Policy.

Cybersecurity is implemented to mitigate vulnerabilities to all DoD real property facility-related control systems to a level that is acceptable to the System Owner and Authorizing Official. UFC 4-010-06 provides requirements for integrating cybersecurity into the design and construction of control systems.

1-6 DESIGN STANDARDS.

Comply with the requirements of National Fire Protection Association (NFPA) 70, National Electrical Code, and the requirements herein. Electrical safety requirements, including the types of energized work permitted, approval process for energized work, and Personal Protective Equipment (PPE), applicable to the design, installation, and operation of electrical systems are provided in UFC 3-560-01.

Note: When a project, or portion of a project, has been designated as requiring Critical Operations Power Systems (COPS) treatment as a Designated Critical Operations Area (DCOA) per NFPA 70 Article 708, those requirements identified in the Unified Facility Criteria that are more stringent than NFPA 70 requirements take precedence over NFPA requirements. This UFC does not address COPS requirements.

1-7 GLOSSARY.

APPENDIX C contains acronyms, abbreviations, and terms.

1-8 REFERENCES.

APPENDIX D contains a list of references used in this document. The publication date of the code or standard is not included in this document. Unless otherwise specified, the most recent edition of the referenced publication applies.

References applicable to a specific topic are also listed and described in the appropriate sections of this UFC. Codes and standards are referenced throughout this UFC.

Follow the guidance provided in UFC 1-200-01, Section 1-3.1 to establish the issue/version of the publication effective for the project.

CHAPTER 2 GENERAL POWER SYSTEM CRITERIA

2-1 VOLTAGE.

Refer to UFC 3-550-01 for voltage criteria associated with the primary distribution supply voltage.

Unless there are specialty voltage requirements, base the facility system voltage on the interior load requirements as follows:

• Apply 240/120V for facilities with only single-phase loads.

• Apply three-phase, four-wire, 208Y/120V systems for lighting and power demand loads less than 150 kVA.

• Apply three-phase, four-wire, 480Y/277V systems for lighting and power demand loads greater than 150 kVA unless 208Y/120V systems are shown to be more cost-effective. Use step-down transformers inside the facility as required to obtain lower voltages.

• For facilities with demand loads less than or equal to 150 kVA in which potential voltage drop issues have been identified, evaluate the life cycle cost effectiveness of installing larger conductor sizes and/or buck-boost transformers on a 208Y/120V system against the use of a 480Y/277V service utilizing step-down transformers. If determined that the life cycle cost is effective, the use of a 480Y/277V service shall be used in lieu of a 208Y/120V service.

2-2 FREQUENCY.

Apply a frequency of 60 Hz for distribution and utilization power.

In locations in which the commercially supplied frequency is other than 60 Hz, such as 50 Hz, use the available supplied frequency to the extent practical. Where frequencies other than that locally available are required for technical purposes, frequency conversion or generation equipment can be installed. The facility user will normally provide this equipment.

CHAPTER 3 POWER DISTRIBUTION AND UTILIZATION

3-1 TRANSFORMERS.

The transformer design criteria provided herein apply to interior applications and to dry-type transformers fed by distribution traditionally placed in/for the facility downstream of the main service. Most facilities will be supplied by an exterior utility system pad-mounted transformer.

Interior transformers shall be sized according to the NEC.

3-1.1 Low Voltage Transformers.

Specify dry-type transformers in accordance with NEMA ST 20 and the following:

• For transformers rated for 15 kVA or larger, use transformers with a 428 degrees F (220 degree C) insulation system not to exceed a 239 degrees F (115 degree C) rise capable of carrying continuously 115 percent of nameplate kVA without exceeding insulation rating at a maximum ambient temperature of 104 degrees F (40 degrees C). Provide a transformer of 80 degrees C temperature rise capable of carrying continuously 130 percent of nameplate kVA without exceeding insulation rating when additional overload capacity is required.

• Transformers rated less than 15 kVA can use a 356 degrees F (180 degree C) insulation system not to exceed an 176 degrees F (80 degree C) rise at a maximum ambient temperature of 104 degrees F (40 degrees C).

• When the transformer is located in areas where noise is a factor, specify sound levels at least 3 decibels below recommended values established by NEMA ST 20.

• Derate the transformer in accordance with the manufacturer’s guidance for locations with a maximum ambient temperature above 104 degrees F (40 degrees C) and in accordance NEMA ST 20 for altitudes higher than 3,300 feet (1,000 meters).

Include the following as part of the installation:

• Design system such that transformer vibrations are not transmitted to the surrounding structure. Small transformers can usually be solidly mounted on a reinforced concrete floor or wall. Flexible mounting will be necessary if the transformer is mounted to the structure in a normally low-ambient noise area.

• Use flexible couplings and conduit to minimize vibration transmission through the connection points.

• Locate the transformer in spaces where the sound level is not increased by sound reflection. For example, in terms of sound emission, the least desirable transformer location is in a corner near the ceiling because the walls and ceiling function as a megaphone.

• Provide adequate ventilation in transformer spaces to prevent the temperature rise from exceeding the transformer rating.

Refer to TSEWG TP-05, Interior Transformer Ratings and Installation, at https://wbdg.org/dod/supp-tech-documents for additional information regarding transformers and transformer ratings.

3-1.2 Other Transformer Types.

Do not use unless justified and documented in the design analysis. Refer to Appendix B for additional guidance for applications involving significant harmonic distortion.

3-2 SERVICE ENTRANCE AND DISTRIBUTION EQUIPMENT.

Locate service entrance equipment and other major electrical equipment in a dedicated electrical space. Provide a main breaker on each service entrance either outside of a building or structure or inside nearest the point of entrance of the service conductors in accordance with NFPA 70. Service feeders may be installed under the building only when necessary or for optimal routing. Distances shall be minimal. Locate other electrical equipment, such as electrical panels, in dedicated spaces.

Note: Identify when 100 percent rated circuit breakers are included in the design.

Size circuit breaker interrupting ratings based on the available short circuit current;

however, do not select circuit breakers less than 10 kA symmetrical interrupting rating for voltages 240V and below and 14 kA symmetrical interrupting rating for 480V applications. The use of series-rated combinations of breakers to clear a fault that utilize an individual breaker rated at less than the available fault current is prohibited.

Do not use fusible overcurrent devices except when non-fusible overcurrent devices will not comply with NFPA 70 requirements for selective coordination.

3-2.1 Spare Capacity.

Provide a minimum of 15% empty space and 15% spare capacity (ampacity) for all switchgear, switchboards, panelboards, and load centers. For flush-mounted equipment, provide spare conduits extending up above the ceiling and down below raised floors when applicable. For panelboards, provide one spare conduit, minimum of ¾-inch (20 mm), for every three spare circuit breakers and for every three empty pole positions. Round up the sum of spare breakers and empty pole positions to the nearest multiple of three.

https://wbdg.org/dod/supp-tech-documents

Note: Do not use spare capacity as part of the demand calculations specified in UFC 3-501-01. The overall calculations already account for this spare capacity with the 15% allowance for future load growth specified in UFC 3-501-01 load analysis calculations for the service entrance.

3-2.2 Selection.

Select equipment as follows:

• Specify metal-enclosed switchgear when the equipment is 1200A or larger, and branch and feeder circuits are above 400A or if any branch or feeder circuits is larger than 800A.

• Specify switchboards when the equipment feeds circuit breakers 800A or larger. Utilize switchboards throughout the distribution system where equipment is 1200A or larger.

• Specify distribution system type panelboards when the equipment is 800 – 1200A. Utilize panelboards up to 600A if they can be accommodated in one enclosure.

For all circuit breakers where the continuous current trip setting for the actual overcurrent device in the circuit breaker is rated for or can be adjusted is 1,200 amperes or higher, select the method used to reduce the clearing time for arc energy reduction:

• Zone-selective interlocking, or

• Differential relaying, or

• Energy-reducing maintenance switching with local status indicator, or

• Energy-reducing active arc flash mitigation system or

• An approved equivalent means.

3-2.3 Switchgear.

Design metal-enclosed switchgear per IEEE C37.20.1 and UL 1558. Provide electrically operated circuit breakers. The switchgear and circuit breakers must be the product of the same manufacturer.

Evaluate the following options as part of the switchgear design:

• Arc-resistant switchgear tested and certified to IEEE C37.20.7 to provide added protection for internal arcing faults.

• Infrared viewing windows to allow the use of an infrared camera or thermal imager direct line of site to inspect electrical connections without requiring the opening of panels and doors.

• A remote racking mechanism to allow an operator to rack a circuit breaker in or out at least 20 feet from the front of the equipment.

• Drawout compartment shutters to protect operators from accidental contact with breaker stabs when a circuit breaker is withdrawn from its cubicle.

• Evaluate medium-voltage gas-insulated switchgear (GIS) with vacuum circuit breakers when the facility owner requires more than 99.9% availability, or the switchgear must fit in a small footprint. GIS switchgear must be tested and certified per IEEE C37.20.9

3-2.4 Switchboards.

Design switchboards per NEMA PB2 and UL 891. Devices must be front accessible and must be completely isolated between sections by vertical steel barriers.

Switchboards should have hinged fronts to allow safer maintenance access for electrical safety.

3-2.5 Panelboards.

3-2.5.1 Configuration.

Equip panelboards and load centers with separate ground bus bars and insulated neutral bus bars to isolate the bus bar, when required by code. Circuit breakers must be bolt-on type unless where specifically indicated otherwise for load center type panelboards. Do not use dual section panelboards.

Do not use panelboards or load centers with more than 54 poles unless any of the following conditions are met.

• All of the loads are served by a redundant source, or

• The customer accepts in writing the risk of larger outages and the AHJ approves the larger panelboard or load center.

Distribution and branch circuit panelboards should be of the wall-mounted, dead-front type, equipped with bolt-on circuit breakers. Load center style panelboards, with plug-in breakers should be used only where authorized for military family housing. Each panelboard and load center style panelboard must be fed from a dedicated circuit and circuit breaker.

3-2.5.2 Location and Design.

Place panelboards as close as possible to the center of the loads to be served. Provide panelboards with hinged fronts to allow safer maintenance access for electrical safety.

Clearly fill out panelboard circuit directories indicating the specific load and location, such as “Lights, Room 102”.

Optimize equipment layout and circuit arrangement. Optimization shall include grouping together circuits going to the same space or area of the building. The phase loading on panelboards shall be balanced as much as practical by the type of loads on the panel.

Take into consideration circuit breaker frame size mismatching when arranging circuits across from each other, as well as additional pole spaces required for specialty features such as 3-pole GFCI electronics and shut trip devices.

3-2.5.3 BEQ/BOQ Facilities and Housing.

Use panelboards for service entrance equipment and electrical distribution in BEQ/BOQ facilities. Load center style panelboards, with plug-in breakers, can be used in housing units and BEQ/BOQ rooms.

3-2.5.4 Arc-Fault Circuit Interrupters.

Provide arc-fault circuit interrupter protection for branch circuits supplying 120V, single-phase,15A and 20A outlets installed in dwelling units as specifically required by NFPA 70.

3-2.6 Motor Control Centers (MCCs).

Comply with UL 845 and NEMA ICS 2.

3-2.7 Power for Fire Protection Systems.

Fire pump and fire pump controller power supply shall satisfy the requirements of NFPA 70 and UFC 3-600-01 rather than the requirements of this subpart.

Provide power for the remainder of the fire protection systems, including fire alarm and mass notification systems, suppression and containment control panels, line voltage indicator systems (such as beacons), transmitter panel, and similar monitoring, control, and reporting equipment but excluding fire pumps and fire pump controllers in accordance with NFPA 72, NFPA 70 Article 760, and as follows:

a. Distribution Configuration(s). A dedicated distribution leg (or multiple legs) shall be supplied from the main distribution equipment to support the fire protection system components described above if either of the following conditions are present:

1. The building area exceeds 25,000 square feet.

2. Six or more circuits are required to supply the fire protection system components on a given voltage system (i.e., 208/120V, 480/277V, etc.).

Circuits for components directly supporting the fire protection components, such as surge protective devices and receptacles in the immediate vicinity of and whose purpose is to perform maintenance on the fire protection components, shall be permitted to be supplied from the dedicated equipment.

In all other cases, the fire protection system components may be suppled from the portions of the distribution equipment present for other building electrical support, and such distribution components must comply with the succeeding requirements of this section.

Where multiple fire protection circuits are supplied from the same panel not dedicated exclusively to fire protection systems described above, connect the fire protection circuits to physically adjacent pole locations.

Where fire protection circuits for larger equipment (such as nitrogen generators or jockey pumps) are connected to the building main distribution equipment or the main distribution equipment for a backup power system, such circuits do not contribute toward the number of circuits in the threshold listed above. The succeeding requirements apply to the circuits connected directly to the main distribution equipment described in the paragraph.

b. Protection and Control Features. Provide lock-on circuit breakers for all feeders and branch circuits supplying fire protection system components described above. Start providing the lock-on circuit breakers from the load side of the service disconnecting means. Permanently identify in red the lock-on breakers in the branch panelboards, distribution equipment, and dedicated panelboards without obstructing manufacturer’s markings on the breakers.

c. Distribution System Identification. At the distribution equipment, including panelboards, distribution panels, switchboards, switchgear, transformers, enclosed circuit breakers, disconnect switches, transfer switches, and similar equipment which are part of the electrical supply to components described above, provide a label with the following inscription in addition to the equipment nameplate: “Fire Protection/Life safety Equipment.”

Construct and fasten the label identical to the panelboard nameplate, except the label must be red laminated plastic with white center core. The service disconnecting means shall not require this supplemental nameplate.

d. Backup Power Sources. For facilities which are provided with emergency power supplies (i.e., engine-driven generator, energy storage system, etc.)

supporting life safety functions, fire protection described above must be powered by the backup power supply system. Do not power fire protection systems from UPS systems dedicated to specific compartmentalized functions such as individual telecommunications rooms.

3-2.8 Disconnect Switches.

Fusible disconnect switches should be used only where special considerations require their use. Provide heavy duty type safety switches on systems rated for greater than 240V. Use fused switches that utilize Class R fuseholders and fuses. Use NEMA 4X stainless steel switch enclosures for switches located on building exteriors in areas where salt spray or extended high humidity is a concern.

Utilize non-fused disconnect switches as local disconnects only, properly protected by an upstream protective device.

Note: Selection of disconnect switches must be coordinated with the short circuit calculations. Non-fused disconnects are typically rated to only 10kAIC. In cases where the fault current at a disconnect location is greater than 10KAIC, provide one of the following solutions:

a. Fused disconnect.

b. Enclosed circuit breaker.

c. If NFPA 70 permits for a given application, eliminate the local disconnecting means and provide a lockable circuit breaker at the panel.

3-2.9 Circuit Lockout Requirements.

Circuit breakers, disconnect switches, and other devices that are electrical energy-isolating must be lockable in accordance with NFPA 70E and OSHA 1910.303.

3-2.10 Signage.

Place a safety sign on any cubicles containing more than one voltage source. Refer to ANSI Z535.4 for safety sign criteria.

3-2.11 Interrupting Ratings.

Refer to TSEWG TP-06, Low Voltage Breaker Interrupting Ratings, at https://wbdg.org/dod/supp-tech-documents for additional information regarding low voltage breaker interrupting ratings.

3-2.12 Load Balancing by Phase.

Arrange circuits throughout the distribution system with 5% or less design load imbalance for both single- and three-phase systems. Show load imbalance by phase as a percentage on the panel, switchboard, switchgear, and motor control center schedules. Larger facilities generally will be capable of better phase balancing than smaller facilities. Document within the design analysis the instances where phase balancing below the imbalance threshold is not possible and state the reasons, tradeoffs, and/or broader remedies.

3-2.13 Adjustable Trip Devices.

Where adjustable-trip devices are used and NFPA 70 does not permit use of the maximum trip setting, conductors must be sized with the rated capacity equal to the actual device setting. Perform arc flash calculations based on the actual device setting.

In design-bid-build projects, provide contract language requiring the contractor to adjust conductor sizes at the direction of the designer of record should the trip setting on the adjustable devices deviate from the rating indicated on the plans in cases such as complying with selective coordination requirements.

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Note: NFPA 70 limits the maximum trip rating for equipment such as transformers and motors. It is also possible for the circuit breaker’s trip setting to exceed the bus rating.

Provide labeling on the adjustable-trip device indicating the maximum value to which the conductors are capable of safely carrying after all applicable correction and adjustment factors were applied and voltage drop calculations performed. Additionally, provide warning of the potential for different arc flash conditions should the adjustable trip rating be altered.

Size equipment grounding conductors and perform voltage drop calculations based on the respective approach used: Where the rating is based on restricted access, use the actual setting; where the rating is based on unrestricted access, use the maximum setting possible.

3-3 MOTORS AND MOTOR CONTROL CIRCUITS.

3-3.1 Basic Motor Criteria.

3-3.1.1 Efficiency.

Apply premium efficiency ratings per the Energy Policy Act of 2005 (EPACT 2005) to all motors.

3-3.1.2 Application.

Use three-phase motors if more than 0.5 horsepower rating when such service is available. If three-phase service is not available or if three-phase motor is not available, operate motors larger than 0.5 horsepower at phase-to-phase voltage rather than phase-to-neutral voltage. Motors 0.5 horsepower and smaller must be single phase.

Do not use 230V motors on 208V systems because the utilization voltage will commonly be below the -10% tolerance on the voltage rating for which the motor is designed (a 230V motor is intended for use on a nominal 240V system).

3-3.2 Motor Control Circuits.

3-3.2.1 Motor Controllers.

Provide motor controllers (starters) for motors larger than 1/8 horsepower (93.25 watts) and apply the design criteria of NEMA ICS 1 and NEMA ICS 2.

3-3.2.2 Motor Starting.

Use full voltage-type starting unless the motor starting current will result in more than a 20% transient voltage dip or if the analyzed voltage dip is otherwise determined to be unacceptable. For other than full voltage starting, apply one of the following methods for motor starting:

• Reduced Voltage Starters.

• Adjustable Speed Drives (ASDs) are also referred to as Variable Frequency Drives (VFDs). If an ASD is required for other reasons, it can also address motor starting current design needs. Refer to NEMA ICS 7 for design criteria related to the selection and design of ASDs. Appendix A provides additional information regarding the sizing and operational design of ASDs.

3-3.2.3 Manual Control.

Provide manual control capability for all installations having automatic control that operates the motor directly. Use a double-throw, three-position switch or other suitable device (marked MANUAL-OFF-AUTOMATIC) for the manual control. Confirm that all safety control devices, such as low- or high-pressure cutouts, high-temperature cutouts, and motor overload protective devices, remain connected in the motor control circuit in both the manual and automatic positions.

3-4 SURGE PROTECTIVE DEVICES (SPDS).

Provide SPDs for surge protection of sensitive or critical electronic equipment, as required by the activity or equipment manufacturer.

The design criteria provided here apply to permanently installed, hard-wired surge protectors and should not be applied to plug-in type surge protectors (Type 3). Use point-of-use (plug-in type) surge protectors to protect specific critical equipment that plugs into wall receptacles.

3-4.1 Power System Surge Protection.

Use Type 1 or Type 2 SPD and connect on the load side of a dedicated main circuit breaker of the associated equipment. Where multiple service main disconnects are used the device(s) should be placed as recommended by the manufacturer to protect the circuits. Locate as close as practical to the breaker with a maximum lead length of 3 ft (900 mm). Integral SPDs with surge counters visible from the dead front of the panelboard and manufactured by the panelboard manufacturer are permitted. The SPDs must be rated as Type 1 or Type 2 and comply with UL 1449. The SPDs must include the thermal protection measures and overcurrent protection per UL 1449.

For buildings with high concentrations of electronics equipment, employ a multi-level or cascaded system. Coordinate multiple stage surge protection.

Note: Type 1 SPDs are allowed to be installed ahead of the service entrance MCB when other equipment is required to be connected ahead of the MCB.

3-4.1.1 Service Entrance Surge Protection.

Provide the following specification requirements for SPD on the service entrance equipment

a. Use SPD to protect the electrical service entrance equipment.

b. The SPD must meet or have a voltage protection rating that is less than the UL 1449 voltage protection ratings listed below. If surge protection is required as part of a lightning protection system, comply with the more stringent voltage protection ratings specified in NFPA 780.

System Voltage Protection Modes

Voltage Protection

Rating 208/120 or

240/120 L-N L-G N-G L-L

1,200 480/277 L-N

L-G N-G L-L

1,200 1,200 1,200 2,000

c. Per mode single pulse surge current rating for an 8x20 ms waveform must be no less than:

L-N 40kA L-G 40kA N-G 40kA L-L 80kA

d. Protection Mode: Provide the following six modes (additional modes are permitted):

Line-to-line Line-to-ground or line-to-neutral

Wire SPDs at grounded service entrances in a line-to-ground (L–G) or line-to-neutral (L–N) configuration. For services without a neutral, connect the SPD elements line-to-ground (L–G).

e. MCOV for L-N and L-G modes of operation: 120% of nominal voltage for 240 volts and below; 115% of nominal voltage above 240 volts to 480 volts.

f. Surge Life: Greater than 5000 surges of repetitive sequential IEEE C62.41 Category C3 waveforms with less than 10% degradation of measured limiting voltage.

g. Listing: The total unit as installed must be UL 1283 and UL 1449 listed, and not merely the components or modules.

h. Warranty: Not less than a 5-year warranty and include unlimited free replacements of the unit if destroyed by lightning or other transients during the warranty period.

i. Diagnostics: Visual indication unit has malfunctioned or requires replacement. Provide Form C dry contacts for remote monitoring.

3-4.1.2 Branch Panelboard Surge Protection.

Provide the following specification requirements for SPD on all the branch panelboards for facilities requiring cascaded suppression system protection.

a. Use SPD to protect the distribution branch panelboards.

b. The SPD must meet or have a voltage protection rating that is less than the UL 1449 voltage protection ratings listed below.

System Voltage Protection Modes

Voltage Protection

Rating 208/120 or

240/120 L-N L-G N-G L-L

1,200 480/277 L-N

L-G N-G L-L

1,200 1,200 1,200 2,000

c. Per mode single pulse surge current rating for an 8x20 ms waveform must be no less than:

L-N 40kA L-G 40kA N-G 40kA L-L 80kA

d. Protection Mode: Provide the following six modes (additional modes are permitted):

Line-to-line Line-to-ground or line-to-neutral

Wire SPDs at grounded service entrances in a line-to-ground (L–G) or line-to-neutral (L–N) configuration. For services without a neutral, connect SPD elements line-to-ground (L–G).

e. MCOV for L-N, L-G, and N-G modes of operation: 120% of nominal voltage for 240 volts and below; 115% of nominal voltage above 240 volts to 480 volts.

f. Surge Life: Greater than 5000 surges of repetitive sequential IEEE C62.41 Category B3 waveforms with less than 10% degradation of measured limiting voltage.

g. Listing: The total unit as installed must be UL 1283 and UL 1449 listed, and not merely the components or modules.

h. Warranty: Not less than a 5-year warranty and include unlimited free replacements of the unit if destroyed by lightning or other transients during the warranty period.

i. Diagnostics: Visual indication unit has malfunctioned or requires replacement. Provide Form C dry contacts for remote monitoring.

3-4.1.3 Dwelling Unit Surge Protection.

Install as close as practical to the main breaker/lugs. All leads must be as short as possible, with no leads longer than 24 in (610 mm). Provide protection in accordance with branch panelboard surge protection criteria listed above.

3-4.2 Surge Protection for Communications and Related Systems.

3-4.2.1 Systems Requiring Protection.

Provide surge protection for the following systems, including related systems:

• Fire alarm systems.

• Telephone systems.

• Computer data circuits.

• Security systems.

• Television systems.

• Coaxial cable systems.

• Intercom systems.

• Electronic equipment data lines.

3-4.2.2 Protection Levels.

Provide surge protection equipment used for communications and related systems as follows:

• If surge protection is required as part of a lightning protection system, comply with the more stringent voltage protection ratings specified in

NFPA 780.

• If surge protection is not required as part of a lightning protection system, provide the following protection UL Listed and tested to UL 497A, or third party verified and tested to UL 497A:

o Telephone communication interface circuit protection – provide a minimum surge current rating of 9,000A.

o Central office telephone line protection – provide multi-stage protection with a minimum surge current rating of 4,000A.

o Intercom circuit protection – provide a minimum surge current rating of 9,000A. Provide protection on points of entry and exit from separate buildings.

• Provide fire alarm and security alarm system loops and addressable circuits that enter or leave separate buildings, UL Listed or third-party verified and tested to UL 497B, with a minimum of 9,000A surge current rating.

• Protect coaxial lines at points of entry and exit from separate buildings.

• Single stage gas discharge protectors can be used for less critical circuits.

Multistage protectors utilizing a gas discharge protector with solid-state secondary stages should be used to obtain lower let-through voltages for more critical equipment.

3-4.3 Acceptance Tests.

Perform the following installation checks:

• Inspect for physical damage and compare nameplate data with drawings and specifications.

• Verify that the surge protector rating is appropriate for the voltage.

• Inspect for proper mounting and adequate clearances.

• Verify that the installation achieves the minimum possible lead lengths.

Inspect the wiring for loops or sharp bends that add to the overall inductance.

• Check tightness of connections by using a calibrated torque wrench.

Refer to the manufacturer’s instructions or Table 10-1 of International Electrical Testing Association (NETA) ATS for the recommended torque.

• Check the ground lead on each device for individual attachment to the ground bus or ground electrode.

• Perform insulation resistance tests in accordance with the manufacturer’s instructions.

• For surge protectors with visual indications of proper operation (indicating lights), verify that the surge protector displays normal operating characteristics.

• Record the date of installation.

3-5 METERING.

Provide advanced metering systems (e.g., with remote reading, monitoring, or activation capabilities) in accordance with service-specific criteria and the DoD directives to comply with EPACT 2005 requirements. Coordinate meters, system components, and meter locations to be compatible with the Activity’s central system.

Upon Activity request, limit housing units to meter sockets only. Sockets must be single phase, four terminal, and ring-less with manual bypass device and polycarbonate blank cover plate.

3-6 RACEWAY AND WIRING.

3-6.1 Wiring Devices.

Wiring devices and faceplate colors must match and be consistent with the interior wall types and colors. Use grounding type wiring devices. Outlet boxes must not be placed back-to-back. Provide a minimum of 12 inch (300 mm) of separation between outlet boxes located on opposite sides on common walls.

3-6.1.1 Switches.

Toggle switches must be specification grade, quiet type, and rated minimum 120/277V, 20A, totally enclosed with bodies of thermoplastic and/or thermoset plastic and mounting strap with grounding screw. Use silver-cadmium contacts and one-piece copper alloy contact arm.

When specified, pilot lights must be integrally constructed as a part of the switch's handle.

3-6.1.2 Receptacles.

Provide general purpose convenience outlets that are specification grade, 20 A, 120 V, duplex. Identify locations where split receptacles will be used with one receptacle controlled by a separate manual or automatic switching device. Provide GFI and AFCI protection in accordance with NFPA 70.

Where required by ASHRAE 90.1, all workstations and work areas must have controlled and non-controlled outlets. For non-systems furniture, duplex receptacles must be split yoke with controlled and non-controlled outlets. Duplex receptacle outlets must be fed from the same circuit. Double duplex receptacles must have controlled and non-controlled outlets fed from the same circuit, but split yoke outlets are not required. Note that GFCI receptacles typically cannot be split wired where both split wiring and GFCI are required. Provide either a GFCI device ahead of the wiring split (such as at the panelboard) or provide a double duplex arrangement where each yoke has a GFCI feature.

In addition to the location requirements specified by NFPA 70, locate general purpose, and dedicated (on an individual circuit) outlets in accordance with the following:

a. Mechanical equipment: Provide receptacle within 25 ft (7.6 m) of mechanical equipment on the interior and exterior of buildings, including roof mounted mechanical equipment.

b. Office, staff-support spaces, and other workstation locations: Minimum of two duplex receptacles, one double duplex, or one quadraplex receptacle for each workstation. Where systems furniture is not to be provided, provide double duplex receptacles a minimum of every 20-ft (5.2 m) of wall space at the floor line. Where there is less than 20-ft (5.2 m) of wall at the floor line in offices and where there are no other provisions for powering workstations (such as with systems furniture), provide a minimum of two duplex receptacles spaced appropriately to anticipate furniture relocations. Limit loads to a maximum of four (4) workstations per 20A circuit.

c. Conference rooms and training rooms: One for every 12 ft (3.6 m) of wall space at the floor line. Ensure one receptacle is located next to each voice/data outlet in all areas of the room (floor, wall, and ceiling). Provide one receptacle in the ceiling, faceplate flush with ceiling, to support video projection device, if necessary, and one receptacle in the wall to support a wall mounted monitor. Extend circuit to wall location for connection to motorized screen. When it is expected that a conference room table will be specifically dedicated to floor space in a conference room, ensure not less than one (1) floor-mounted receptacle is located under the table. This receptacle may be part of combination power/communications outlet.

Ensure signal pathway exists between conference room table and wall or ceiling mounted displays.

d. Provide power outlets throughout the building to serve all proposed equipment, including government furnished equipment, and allow for future reconfiguration of equipment layout. Provide power connections to all ancillary office equipment such as printers, faxes, plotters, and shredders. Provide dedicated circuits where warranted.

e. In each telecommunications room provide a dedicated 20A circuit with a receptacle adjacent to each rack or backboard for each of the following:

• CCTV for training systems

• CCSTV for security systems

• CATV

• Voice systems

• Data systems.

f. Provide receptacles supplying television monitors on circuits dedicated for such equipment and associated specialty equipment. Multiple receptacles, television monitors, and associated specialty equipment receptacles may be connected to the same circuit dedicated to this purpose provided the total connected load satisfies the limits permitted by NFPA 70 for a standard 15- or 20-amp receptacle circuit as applicable.

These outlets will typically be located near the ceiling level for wall mounted television monitors.

g. Corridors: One every 50 ft (15 m) with a minimum of one per corridor.

h. Janitor’s closet and toilet rooms: One GFI receptacle per closet. Provide

GFI receptacles at counter height for each counter in toilets such that there is a minimum of one outlet for each two sinks.

i. Space with counter tops: One for every 4 ft (1.2 m) of countertop, with a minimum of one outlet.

j. Building exterior: GFCI protected, weather-resistant (WR) and identified as extra-duty, within 25 ft (7.5 m) of each exterior door and near HVAC equipment in accordance with NFPA 70 requirements. An exception to the requirement for a receptacle in proximity to each exterior door is permitted for doors providing direct entrance into living units for barracks and dormitories. In such cases, one is to be provided for every 50 ft (15

m) wall length with a minimum of one per exterior wall; additionally, one is to be installed within 10 ft (3m) of each exterior door which does not provide direct entrance into a living unit.

k. Kitchen non-residential: One for each 10 ft (3 m) of wall space at the floor line.

l. Dwelling units, Child Development Centers, and other child occupied spaces (including toilets): Provide listed tamper-resistant receptacles.

m. All other rooms: One for every 25 ft (7.6 m) of wall space at the floor line.

When 25 ft (7.6 m) or less of wall at the floor line exists in a room, provide a minimum of two receptacles spaced appropriately to anticipate furniture relocations.

n. Special purpose receptacles: Coordinate with the user to provide any special purpose outlets required. Provide outlets to allow connection of equipment in special use rooms.

o. Permanently installed equipment: Do not use cord and plug connections for permanently installed equipment in areas requiring GFI-protected receptacles. Provide hard-wired connections instead.

3-6.2 Cable and Raceway Criteria.

3-6.2.1 Installation.

Minimum permitted size conduit permitted is 1/2 in (15 mm). Provide an insulated green equipment grounding conductor or supply-side bonding jumper for all circuit(s) installed in raceways. Do not rely on the metallic raceway as the only boding path. Conceal raceways above ceilings and in finished areas that have finished walls or finished surfaces.

The above minimum conduit size does not apply to conduit that is part of a factory installed assembly, such as lighting fixtures.

3-6.2.2 Approved Cable and Raceway Types.

Specify cables and raceway in accordance with NFPA 70 as follows:

• The Uses Permitted are as modified by Table 3-1.

• The Uses Not Permitted are:

o As specified in NFPA 70.

o When restricted by other UFCs for specific types of buildings such as medical facilities.

For instances where NFPA 70 does not allow an installation based on “subject to physical damage” or “subject to severe physical damage,” refer to Appendix C-2 for baseline definitions of these conditions.

Provide a plan in the contract documents that graphically depicts the areas subject to physical damage or subject to severe physical damage along with the descriptions (such as the heights given in Appendix C-2) for installation purposes. Alternatively, as another option, provide a narrative list in the specifications indicating such descriptions in the portion of the specifications pertaining to areas subject to physical damage and subject to severe physical damage, respectively.

Table 3-1 Authorized Cable and Raceway Types

NFPA 70

Article Raceway/Cable Type Authorization

320 AC – Armored Cable Prohibited for feeder circuits.

Prohibited for embedded locations.

Allowed for branch circuits only in the following dry locations:

• New construction in exposed locations.

• Renovations in exposed locations.

• Concealed in renovations in existing areas where walls and ceilings are not disturbed.

• Cable trays.

322 FC – Flat Cable

Assemblies Authorized.

324 FCC – Flat Conductor Cable

Authorized.

326 IGS – Integrated Gas Spacer Cable

Prohibited.

328 MV – Medium Voltage Cable

Authorized. For interior applications, MV cable must be installed in raceway or a fully enclosed cable tray.

Refer to UFC 3-550-01 for additional applications.

NFPA 70

Article Raceway/Cable Type Authorization

330 MC – Metal-Clad Cable Prohibited for feeder circuits other than feeder circuits for aerial messengers between buildings.

Prohibited for embedded or direct buried locations.

Prohibited for concealed locations, except as allowed below.

Allowed for branch circuits only in the following dry locations:

• New construction in exposed locations.

• Renovations in exposed locations.

• Concealed in renovations in existing areas where walls and ceilings are not disturbed.

• Cable trays.

332 MI – Mineral-Insulated, Metal-Sheathed Cable Authorized.

334 NM, NMC, NMS –

Nonmetallic-Sheathed Cable

Allowed only in one- and two-family dwellings and their attached or detached garages, and their storage buildings.

336 TC – Power and Control Tray Cable

Authorized.

338 SE, USE – Service- Entrance Cable

Authorized.

340 UF – Underground Feeder and Branch- Circuit Cable

Prohibited.

342 IMC – Intermediate Metal Conduit

Authorized.

344 RMC – Rigid Metal Conduit

Authorized. Only threaded-type fittings are allowed for wet and damp locations.

Article Raceway/Cable Type Authorization

348 FMC – Flexible Metal Conduit

Flexible metal conduit can be used, limited to 6 ft length, for…