PEC 2017 – Article 1.10

Posted by

Table of Contents

Article 1.10 – REQUIREMENTS FOR ELECTRICAL INSTALLATIONS

1.10.1 General

1.10.1.1 Scope

This article covers general requirements for the examination and approval, installation and use, access to and spaces about electrical conductors and equipment; enclosures intended for personnel entry; and tunnel installations.

1.10.1.2 Approval

The conductors and equipment required or permitted by this Code shall be acceptable only if approved.

FPN: See 1.0.1.7, Examination of Equipment for Safety, and 1.10.1.3, Examination, Identification, Installation, and Use of Equipment. See definitions of Approved, Identified, Labeled, and Listed.

1.10.1.3 Examination, Identification, Installation, Use, and Listing (Product Certification) of Equipment.

(A) Examination

In judging equipment, considerations such as the following shall be evaluated:

  • (1) Suitability for installation and use in conformity with the provisions of this Code

FPN No. 1: Equipment may be new, reconditioned, refurbished, or remanufactured.

FPN No. 2: Suitability of equipment use may be identified by a description marked on or provided with a product to identify the suitability of the product for a specific purpose, environment, or application. Suitability of equipment may be evidenced by listing or labeling.

  • (2) Mechanical strength and durability, including, for parts designed to enclose and protect other equipment, the adequacy of the protection thus provided
  • (3) Wire-bending and connection space
  • (4) Electrical Insulation
  • (5) Heating effects under normal conditions of use and also under abnormal conditions likely to arise in service
  • (6) Arcing effects
  • (7) Classification by type, size, voltage, current capacity, and specific use
  • (8) Other factors that contribute to the practical safeguarding of persons using or likely to come in contact with the equipment

(B) Installation and Use

Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.

(C) Listing

Product testing, evaluation, and listing (product certification) shall be performed by recognized qualified electrical testing laboratories and shall be in accordance with applicable product standards recognized as achieving equivalent and effective safety for equipment installed to comply with this Code.

FPN: The Occupational Safety and Health Administration (OSHA) recognizes qualified electrical testing laboratories that perform evaluation, testing, and certification of certain products to ensure that they meet the requirements of both the construction and general industry OSHA electrical standards. If the listing (product certification) is done under a qualified electrical testing laboratory program, this listing mark signifies that the tested and certified product complies with the requirements of one or more appropriate product safety test standards.

1.10.1.4 Voltages

Throughout this Code, the voltage considered shall be that at which the circuit operates. The voltage rating of electrical equipment shall not be less than the nominal voltage of a circuit to which it is connected.

1.10.1.5 Conductors

Conductors normally used to carry current shall be of copper or aluminum unless otherwise provided in this Code. Where the conductor material is not specified, the sizes given in this Code shall apply to copper conductors. Where other materials are used, the size shall be changed accordingly.

FPN For aluminum and copper-clad aluminum conductors, see 3.10.1.15.

1.10.1.6 Conductor Sizes

Conductor sizes are expressed in metric system (SI).

1.10.1.7 Wiring Integrity

Completed wiring installations shall be free from short circuits and from grounds other than as required or permitted in Article 2.50.

1.10.1.8 Wiring Methods

Only wiring methods recognized as suitable are included in this Code. The recognized methods of wiring shall be permitted to be installed in any type of building or occupancy, except as otherwise provided in this Code.

1.10.1.9 Interrupting Rating

Equipment intended to interrupt current at fault levels shall have an interrupting rating sufficient for the nominal circuit voltage at least equal to the current that is available at the line terminals of the equipment.

Equipment intended to interrupt current at other than fault levels shall have an interrupting rating at nominal circuit voltage at least equal to the current that must be interrupted.

1.10.1.10 Circuit Impedance, Short-Circuit Current Ratings, and Other Characteristics

The overcurrent protective devices, the total impedance, the component short-circuit current ratings, and other characteristics of the circuit to be protected shall be selected and coordinated to permit the circuit protective devices used to clear a fault to do so without extensive damage to the electrical components of the circuit. This fault shall be assumed to be either between two or more of the circuit conductors or between any circuit conductor and the grounding conductor(s) permitted in 2.50.6.9. Listed products applied in accordance with their listing shall be considered to meet the requirements of this section.

1.10.1.11 Deteriorating Agents

Unless identified for use in the operating environment, no conductors or equipment shall be located in damp or wet locations; where exposed to gases, fumes, vapors, liquids, or other agents that have a deteriorating effect on the conductors or equipment; or where exposed to excessive temperatures.

FPN No.1: See 3.0.1.6 for protection against corrosion.

FPN No. 2: Some cleaning and lubricating compounds can cause severe deterioration of many plastic materials used for insulating and structural applications in equipment.

Equipment identified only as “dry locations,” “Type 1,” or “indoor use only” shall be protected against permanent damage from the weather during building construction.

FPN No. 3: See Table 1.10.2.3 for appropriate enclosure-type designations.

FPN No. 4: Minimum flood provisions are provided in NFPA 5000-2015 Building Construction and Safety Code, the International Building Code (IBC), and the International Residential Code for One-and Two-Family Dwelling Unit (IRC).

1.10.1.12 Listed and Labeled When Not Required

Electrical Equipment, materials and services shall not be required to be Listed and/or Labeled when local or international product and services standards do not require listing and/or labeling.

1.10.1.13 Mechanical Execution of Work

Electrical equipment shall be installed in a neat and workmanlike manner.

FPN: Accepted industry practices are described in ANSI/NECA 1-2015, Standard Practices for Good Workmanship in Electrical Contracting, and other ANSI-approved installation standards.

(A) Unused Openings

Unused openings, other than those intended for the operation of equipment, those intended for mounting purposes, or those permitted as part of the design for listed equipment, shall be effectively closed to afford protection substantially equivalent to the wall of the equipment. Where metallic plugs or plates are used with nonmetallic enclosures, they shall be recessed at least 6 mm from the outer surface of the enclosure.

(B) Integrity of Electrical Equipment and Connections.

Internal parts of electrical equipment, including busbars, wiring terminals, insulators, and other surfaces, shall not be damaged or contaminated by foreign materials such as paint, plaster, cleaners, abrasives, or corrosive residues. There shall be no damaged parts that may adversely affect safe operation or mechanical strength of the equipment such as parts that are broken; bent; cut; or deteriorated by corrosion, chemical action, or overheating.

1.10.1.14 Mounting and Cooling of Equipment

(A) Mounting

Electrical equipment shall be firmly secured to the surface on which it is mounted. Wooden plugs driven into holes in masonry, concrete, plaster, or similar materials shall not be used.

(B) Cooling

Electrical equipment that depends on the natural circulation of air and convection principles for cooling of exposed surfaces shall be installed so that room airflow over such surfaces is not prevented by walls or by adjacent installed equipment. For equipment designed for floor mounting, clearance between top surfaces and adjacent surfaces shall be provided to dissipate rising warm air.

Electrical equipment provided with ventilating openings shall be installed so that walls or other obstructions do not prevent the free circulation of air through the equipment.

1.10.1.15 Electrical Connections

Because of different characteristics of dissimilar metals, devices such as pressure terminal or pressure splicing connectors and soldering lugs shall be identified for the material of the conductor and shall be properly installed and used. Conductors of dissimilar metals shall not be intermixed in a terminal or splicing connector where physical contact occurs between dissimilar conductors (such as copper and aluminum, copper and copper-clad aluminum, or aluminum and copper-clad aluminum), unless the device is identified for the purpose and conditions of use. Materials such as solder, fluxes, inhibitors, and compounds, where employed, shall be suitable for the use and shall be of a type that will not adversely affect the conductors, installation, or equipment.

Connectors and terminals for conductors more finely stranded than Class B and Class C stranding as shown in Chapter 10, Table 10.1.1.10, shall be identified for the specific conductor class or classes.

(A) Terminals

Connection of conductors to terminal parts shall ensure a thoroughly good connection without damaging the conductors and shall be made by means of pressure connectors (including setscrew type), solder lugs, or splices to flexible leads. Connection by means of wire-binding screws or studs and nuts that have upturned lugs or the equivalent shall be permitted for 5.5 mm2 (2.6 mm dia.) or smaller conductors. Terminals for more than one conductor and terminals used to connect aluminum shall be so identified.

(B) Splices

Conductors shall be spliced or joined with splicing devices identified for the use or by brazing, welding, or soldering with a fusible metal or alloy. Soldered splices shall first be spliced or joined so as to be mechanically and electrically secure without solder and then be soldered. All splices and joints and the free ends of conductors shall be covered with an insulation equivalent to that of the conductors or with an identified insulating device. Wire connectors or splicing means installed on conductors for direct burial shall be listed for such use.

(C) Temperature Limitations

The temperature rating associated with the ampacity of a conductor shall be selected and coordinated so as not to exceed the lowest temperature rating of any connected termination, conductor, or device. Conductors with temperature ratings higher than specified for terminations shall be permitted to be used for ampacity adjustment, correction, or both.

(1) Equipment Provisions

The determination of termination provisions of equipment shall be based on 1.10.1.14(C)(1)a or (C)(1)b. Unless the equipment is listed and marked otherwise, conductor ampacities used in determining equipment termination provisions shall be based on Table 3.10.2.6 as appropriately modified by 3.10.2.6(B)(6).

  • (a) Termination provisions of equipment for circuits rated 100 amperes or less, or marked for 2.0 mm2 (1.6 mm dia.) through 38 mm2 conductors, shall be used only for one of the following:
    • 1.  Conductors rated 60°C
    • 2. Conductors with higher temperature ratings, provided the ampacity of such conductors is determined based on the 60°C ampacity of the conductor size used.
    • 3. Conductors with higher temperature ratings if the equipment is listed and identified for use with such conductors.
    • 4. For motors marked with design letters B, C, or D, conductors having an insulation rating of 75°C or higher shall be permitted to be used, provided the ampacity of such conductors does not exceed the 75°C ampacity.
  • (b) Termination provisions of equipment for circuits rated over 100 amperes, or marked for conductors larger than 38 mm2, shall be used only for one of the following:
    • 1. Conductors rated 75°C
    • 2. Conductors with higher temperature ratings, provided the ampacity of such conductors does not exceed the 75°C ampacity of the conductor size used, or up to their ampacity if the equipment is listed and identified for use with such conductors
(2) Separate Connector Provisions

Separately installed pressure connectors shall be used with conductors at the ampacities not exceeding the ampacity at the listed and identified temperature rating of the connector.

FPN: With respect to 1.10.1.14(C)(1) and (C)(2), equipment markings or listing information may additionally restrict the sizing and temperature ratings of connected conductors.

(D) Installation

Where a tightening torque is indicated as a numeric value on equipment or in installation instructions provided by the manufacturer, a calibrated torque tool shall be used to achieve the indicated torque value, unless the equipment manufacturer has provided installation instructions for an alternative method of achieving the required torque.

1.10.1.16 High-Leg Marking

On a 4-wire, delta-connected system where the midpoint of one phase winding is grounded, only the conductor or busbar having the higher phase voltage to ground shall be durably and permanently marked by an outer finish that is orange in color or by other effective means. Such identification shall be placed at each point on the system where a connection is made if the grounded conductor is also present.

1.10.1.17 Arc-Flash Hazard Warning

(A) General

Electrical equipment, such as switchboards, switchgear, panelboards, industrial control panels, meter socket enclosures, and motor control centers, that is in other than dwelling units, is likely to require examination, adjustment, servicing, or maintenance while energized, shall be field or factory marked to warn qualified persons of potential electric arc flash hazards. The marking shall meet the requirements in 1.10.1.21(B) and shall be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment.

(B) Service Equipment

In other than dwelling units, in addition to the requirements in (A), a permanent label shall be field or factory applied to service equipment rated 1200 amps or more. The label shall meet the requirements of 1.10.1.21(B) and contain the following information:

  1. Nominal System Voltage
  2. Available fault current at the service overcurrent protective devices
  3. The clearing time of service overcurrent protective devices based on the available fault current at the service equipment
  4. The date the label was applied

Exception: Service equipment labeling shall not be required if an arc flash label is applied in accordance with acceptable industry practice.

FPN No. 1: NFPA 70E-2015, Standard for Electrical Safety in the Workplace, provides assistance in determining severity of potential exposure, planning safe work practices, and selecting personal protective equipment.

FPN No. 2: ANSI Z535.4-2011, Product Safety Signs and Labels, provides guidelines for the design of safety signs and labels for application to products.

FPN No. 3: Acceptable industry practices for equipment labeling are described in NFPA 70E-2015 Standard for Electrical Safety in the Workplace. This standard provides specific criteria for developing arc-flash labels for equipment that provides nominal system voltage, incident energy levels, arc-flash boundaries, minimum required levels of personal protective equipment, and so forth.

1.10.1.18 Arcing Parts

Parts of electric equipment that in ordinary operation produce arcs, sparks, flames, or molten metal shall be enclosed or separated and isolated from all combustible material.

FPN: For hazardous (classified) locations, see Articles 5.0 through 5.17. For motors, see 4.30.1.14.

1.10.1.19 Light and Power from Railway Conductors

Circuits for lighting and power shall not be connected to any system that contains trolley wires with a ground return.

Exception: Such circuit connections shall be permitted in car houses, power houses, or passenger and freight stations operated in connection with electric railways.

1.10.1.21 Marking

(A) Equipment Markings

(1) General

The manufacturer’s name, trademark, or other descriptive marking by which the organization responsible for the product can be identified shall be placed on all electric equipment. Other markings that indicate voltage, current, wattage, or other ratings shall be provided as specified elsewhere in this Code. The marking shall be of sufficient durability to withstand the environment involved.

(2) Reconditioned Equipment

Reconditioned equipment shall be marked with the name, trademarks, or other descriptive marking by which the organization responsible for reconditioning the electrical equipment can be identified, along with the date of reconditioning.

Reconditioned equipment shall be identified as “reconditioned” and approval of the reconditioned equipment shall not be based solely on the equipment’s original listing.

Exception: In industrial occupancies, where conditions of maintenance and supervision ensure that only qualified persons service the equipment, the markings indicated in 1.10.1.21(A)(2) shall not be required.

FPN: Industry standards are available for application of reconditioned and refurbished equipment. Normal servicing of equipment that remains within a facility should not be considered reconditioning or refurbishing.

(B) Field-Applied Hazard Markings

Where caution, warning, or danger sins or labels are required by this Code, the labels shall meet the following requirement:

  1. The marking shall warn of the hazards using effective words, colors, symbols or any combination thereof.
  2. The label shall be permanently affixed to the equipment or wiring method and shall not be hand written.
  3. The label shall be of sufficient durability to withstand the environment involved.

FPN: ANSI Z535.4-2011, Product Safety Signs and Labels, provides guidelines for suitable font sizes, words, colors, symbols, and location requirements for labels.

Exception to (2): Portions of labels or markings that are variable, or that could be subject to changes, shall be permitted to be hand written and shall be legible.

FPN: ANSI Z535.4-2011, Product Safety Signs and Labels, provides guidelines for design and durability of safety signs and labels for application to electrical equipment.

1.10.1.22 Identification of Disconnecting Means

(A) General

Each disconnecting means shall be legibly marked to indicate its purpose unless located and arranged so the purpose is evident. The marking shall be of sufficient durability to withstand the environment involved.

(B) Engineered Series Combination Systems

Equipment enclosures for circuit breakers or fuses applied in compliance with series combination ratings selected under engineering supervision in accordance with 2.40.7.7(A) shall be legibly marked in the field as directed by the engineer to indicate the equipment has been applied with a series combination rating. The marking shall meet the requirements in 1.10.1.21(B) and shall be readily visible and state the following:

CAUTION
SERIES COMBINATION SYSTEM RATED
___ AMPERES IDENTIFIED REPLACEMENT
COMPONENTS REQUIRED

(C) Tested Series Combination Systems

Equipment enclosures for circuit breakers or fuses applied in compliance with series combination ratings selected under engineering supervision in accordance with 2.40.7.7(B) shall be legibly marked in the field as directed by the engineer to indicate the equipment has been applied with a series combination rating. The marking shall meet the requirements in 1.10.1.21(B) and shall be readily visible and state the following:

CAUTION
SERIES COMBINATION SYSTEM RATED
___ AMPERES IDENTIFIED REPLACEMENT
COMPONENTS REQUIRED

FPN: See IEEE 3004.5-2014 Recommended Practice for the Application of Low-Voltage Circuit Breakers in Industrial and Commercial Power Systems, for further information on series tested systems.

1.10.1.23 Current Transformers

Unused current transformers associated with potentially energized circuits shall be short-circuited.

1.10.1.24 Available Fault Current

(A) Field Marking

Service Equipment at other than dwelling units shall be legibly marked in the field with the maximum available fault current. The field marking(s) shall include the date the fault-current calculations was performed and be of sufficient durability to withstand the environment involved. The calculation shall be documented and made available to those authorized to design, install, inspect, maintain, or operate the system.

FPN: The available fault-current marking(s) addressed in 1.10.1.24 is related to the required short-circuit current ratings of equipment. NFPA 70E-2015, Standard for Electrical Safety in the Workplace, provides assistance in determining the severity of potential exposure, planning safe work practices, and selecting personal protective equipment.

(B) Modifications

When modifications to the electrical installation occur that affect the maximum available fault current at the service, the maximum available fault current shall be verified or recalculated as necessary to ensure the service equipment ratings are sufficient for the maximum available fault current at the line terminals of the equipment. The required field marking(s) in 1.10.1.24(A) shall be adjusted to reflect the new level of maximum available fault current.

Exception: The field marking requirements in 1.10.1.24(A) and 1.10.1.24(B) shall not be required in industrial installations where conditions of maintenance and supervision ensure that only qualified persons service the equipment.

1.10.1.25 Lockable Disconnecting Means

If a disconnecting means is required to be lockable open elsewhere in this Code, it shall be capable of being locked in the open position. The provisions for locking shall remain in place with or without the lock installed.

Exception: Locking provisions for a cord-and-plug connection shall not be required to remain in place without the lock installed.

1.10.2 1000 Volts, Nominal, or Less

1.10.2.1 Spaces About Electrical Equipment

Sufficient access and working space shall be provided and maintained about all electric equipment to permit ready and safe operation and maintenance of such equipment.

(A) Working Space

Working space for equipment operating at 1000 volts, nominal, or less to ground and likely to require examination, adjustment, servicing, or maintenance while energized shall comply with the dimensions of 1.10.2.1(A)(1), (A)(2), and (A)(3) or as required or permitted elsewhere in this Code.

(1) Depth of Working Space

The depth of the working space in the direction of live parts shall not be less than that specified in Table 1.10.2.1(A)(1) unless the requirements of 1.10.2.1(A)(1)a, (A)(1)b, or (A)(1)c are met. Distances shall be measured from the exposed live parts or from the Height of Working Space. The work space shall be clear and extend from the grade, floor, or platform to the height required by 1.10.2.1(E). Within the height requirements of this section, other equipment that is associated with the electrical installation and is located above or below the electrical equipment shall be permitted to extend not more than 150 mm beyond the front of the electrical equipment.

  • a. Dead-Front Assemblies. Working space shall not be required in the back or sides of assemblies, such as dead-front switchboards, switchgear, or motor control centers, where all connections and all renewable or adjustable parts, such as fuses or switches, are accessible from locations other than the back or sides. Where rear access is required to work on nonelectrical parts on the back of enclosed equipment, a minimum horizontal working space of 750 mm shall be provided.
  • b. Low Voltage. Smaller working spaces shall be permitted where all exposed live parts operate at not greater than 30 volts rms, 42 volts peak, or 60 volts dc.
  • c. Existing Buildings. . In existing buildings where electrical equipment is being replaced, Condition 2 working clearance shall be permitted between dead-front switchboards, switchgear, panelboards, or motor control centers located across the aisle from each other where conditions of maintenance and supervision ensure that written procedures have been adopted to prohibit equipment on both sides of the aisle from being open at the same time and licensed electrical practitioner or qualified person under the supervision of licensed electrical practitioner who are authorized will service the installation.
Table 1.10.2.1(A)(1) Working Spaces
Nominal Voltage to GroundMinimum Clear Distance (mm)
Condition 1Condition 2Condition 3
0 -150900900900
151 – 60090010001200
601 – 100090012001500
Note: Where the conditions are as follows:
Condition 1 – Exposed live parts on one side of the working space and no live or grounded parts on the other side of the working space, or exposed live parts on both sides of the working space that are effectively guarded by insulating materials.
Condition 2 – Exposed live parts on one side of the working space and grounded parts on the other side of the working space. Concrete, brick, or tile walls shall be considered as grounded.
Condition 3 – Exposed live parts on both sides of the working space.
(2) Width of Working Space

The width of the working space in front of the electric equipment shall be the width of the equipment or 750 mm, whichever is greater. In all cases, the work space shall permit at least a 90 degree opening of equipment doors or hinged panels.

(3) Height of Working Space

The work space shall be clear and extend from the grade, floor, or platform to the height required by 1.10.2.1(E). Within the height requirements of this section, other equipment that is associated with the electrical installation and is located above or below the electrical equipment shall be permitted to extend not more than 150 mm beyond the front of the electrical equipment.

Exception No.1: In existing dwelling units, service equipment or panelboards that do not exceed 200 amperes shall be permitted in spaces where the height of the working space is less than 2000 mm.

Exception No. 2: Meters that are installed in meter sockets shall be permitted to extend beyond the other equipment. The meter socket shall be required to follow the rules of this section.

Exception No. 3: On battery systems mounted on open racks, the top clearance shall comply with 4.80.1.10(D)

(4) Limited Access

Where equipment operating at 1000 volts, nominal, or less to ground and likely to require examination, adjustment, servicing, or maintenance while energized is required by installation instructions or function to be located in a space with limited access, all of the following shall apply:

  • (a) Where equipment is installed above a lay-in ceiling, there shall be an opening not smaller than 559 mm x 559 mm, or in a crawl space, there shall be an accessible opening not smaller than 559 mm x 762 mm.
  • (b) The width of the working space shall be the width of the equipment enclosure or a minimum of 762 mm, whichever is greater.
  • (c) All enclosure doors or hinged panels shall be capable of opening a minimum of 90 degrees.
  • (d) The space in front of the enclosure shall comply with the depth requirements of Table 1.10.2.1(A)(1). The maximum height of the working space shall be the height necessary to install the equipment in the limited space. A horizontal ceiling structural member or access panel shall be permitted in this space.
(5) Separation from High-Voltage Equipment

Where switches, cutouts, or other equipment operating at 1000 volts, nominal or less are installed in a vault, room, or enclosure where there are exposed live parts or exposed wiring operating over 1000 volts, nominal, the high-voltage equipment shall be effectively separated from the space occupied by the low-voltage equipment by a suitable partition, fence , or screen.

(B) Clear Spaces

Working space required by this section shall not be used for storage. When normally enclosed live parts are exposed for inspection or servicing, the working space, if in a passageway or general open space, shall be suitably guarded.

(C) Entrance to Working Space

(1) Minimum Required

At least one entrance of sufficient area shall be provided to give access to working space about electrical equipment.

(2) Large Equipment

For equipment rated 1 200 amperes or more that contains overcurrent devices, switching devices, or control devices, there shall be one entrance to the required working space not less than 600 mm wide and 2 000 mm high at each end of the working space. Where the entrance has a personnel door(s), the door(s) shall open in the direction of egress and be equipped with panic bars, pressure plates, or other devices that are normally latched but open under simple pressure.

A single entrance to the required working space shall be permitted where either of the conditions in 1.10.2.1(C)(2)a or (C)(2)b is met.

  • (a) Unobstructed Exit. Where the location permits a continuous and unobstructed way of exit travel, a single entrance to the working space shall be permitted.
  • (b) Extra Working Space. Where the depth of the working space is twice that required by 1.10.2.1(A)(1), a single entrance shall be permitted. It shall be located so that the distance from the equipment to the nearest edge of the entrance is not less than the minimum clear distance specified in Table 1.10.2.1(A)(1) for equipment operating at that voltage and in that condition.
(3) Personnel Doors

Where equipment rated 800 A or more that contains overcurrent devices, switching devices, or control devices is installed and there is a personnel door(s) intended for entrance to and egress from the working space less than 7600 mm from the nearest edge of the working space, the door(s) shall open in the direction of egress and be equipped with listed panic hardware.

(D) Illumination

Illumination shall be provided for all working spaces about service equipment, switchboards, switchgears, panelboards, or motor control centers installed indoors. Additional lighting outlets shall not be required where the work space is illuminated by an adjacent light source or as permitted by 2.10.3.21(A)(1), Exception No. 1, for switched receptacles.

(E) Dedicated Equipment Use

All switchboards, switchgear, panelboards, distribution boards, and motor control centers, shall be located in dedicated spaces and protected from damage.

Exception: Control equipment that by its very nature or because of other rules of the Code must be adjacent to or within sight of its operating machinery shall be permitted in those locations.

(1) Indoor

Indoor installations shall comply with 1.10.2.1(E)(1)a through (E)(1)d.

  • a. Dedicated Electrical Space. The space equal to the width and depth of the equipment and extending from the floor to a height of 1 800 m above the equipment or to the structural ceiling, whichever is lower, shall be dedicated to the electrical installation. No piping, ducts, leak protection apparatus, or other equipment foreign to the electrical installation shall be located in this zone.

Exception: Suspended ceilings with removable panels shall be permitted within the 1 800 mm zone.

  • b. Foreign Systems. The area above the dedicated space required by 1.10.2.1(E)(1)a shall be permitted to contain foreign systems, provided protection is installed to avoid damage to the electrical equipment from condensation, leaks, or breaks in such foreign systems.
  • c. Sprinkler Protection. Sprinkler protection shall be permitted for the dedicated space where the piping complies with this section.
  • d. Suspended Ceilings. A dropped, suspended, or similar ceiling that does not add strength to the building structure shall not be considered a structural ceiling.
(2) Outdoor

Outdoor installations shall comply with 1.10.1.26(E)(2)(a) and (b).

  • a. Installation Requirements. Outdoor electrical equipment shall be the following:
    • (1) Installed in identified enclosures
    • (2) Protected from accidental contact by unauthorized personnel or by vehicular traffic.
    • (3) Protected from accidental spillage or leakage from piping systems.
  • b. Work Space. The working clearance space shall include the zone described in 1.10.2.1(A). No architectural appurtenance or other equipment shall be located in this zone.

Exception: Structural overhangs or roof extensions shall be permitted in this zone.

  • c. Dedicated Equipment Space. The space equal to the width and depth of the equipment, and extending from grade to a height of 1800 mm above the equipment, shall be dedicated to the electrical installation. No piping or other equipment foreign to the electrical installation shall be located in this zone.

(F) Locked Electrical Equipment Rooms or Enclosures

Electrical equipment rooms or enclosures housing electrical apparatus that are controlled by a lock(s) shall be considered accessible to qualified persons.

1.10.2.2 Guarding of Live Parts

(A) Live Parts Guarded Against Accidental Contact

Except as elsewhere required or permitted by this Code, live parts of electrical equipment operating at 50 volts or more shall be guarded against accidental contact by approved enclosures or by any of the following means:

  • (1) By location in a room, vault, or similar enclosure that is accessible only to licensed electrical practitioner or qualified person under the supervision of a licensed electrical practitioner.
  • (2) By permanent, substantial partitions or screens arranged so that only licensed electrical practitioner or qualified person under the supervision of a licensed electrical practitioner have access to the space within reach of the live parts. Any openings in such partitions or screens shall be sized and located so that persons are not likely to come into accidental contact with the live parts or to bring conducting objects into contact with them.
  • (3) By location on a suitable balcony, gallery, or platform elevated and arranged so as to exclude unqualified persons.
  • (4) By elevation above the floor or other working surface as shown in 1.10.2.2(A)(4)(a) or (b) below:
    • a. A minimum of 2500 mm for 50 volts to 300 volts between ungrounded conductors.
    • b. A minimum of 2600 mm for 301 volts to 600 volts between ungrounded conductors.
    • c. A minimum of 2620 mm for 601 volts to 1000 volts between ungrounded conductors.

(B) Prevent Physical Damage

In locations where electric equipment is likely to be exposed to physical damage, enclosures or guards shall be so arranged and of such strength as to prevent such damage.

(C) Warning Signs

Entrances to rooms and other guarded locations that contain exposed live parts shall be marked with conspicuous warning signs forbidding unqualified persons to enter. The marking shall meet the requirements in 1.10.1.21(B)

FPN: For motors, see 4.30.12.2 and 4.30.12.3. For over 1000 volts, see 1.10.3.5.

1.10.2.3 Enclosure Types

Enclosures (other than surrounding fences or walls covered in 1.10.3.2) of switchboards, switchgear, panelboards, industrial control panels, motor control centers, meter sockets, enclosed switches, transfer switches, power outlets, circuit breakers, adjustable-speed drive systems, pullout switches, portable power distribution equipment, termination boxes, general-purpose transformers, fire pump controllers, fire pump motors, and motor controllers, rated not over 1000 volts nominal and intended for such locations, shall be marked with an enclosure-type number as shown in Table 1.10.2.3.

Table 1.10.2.3 shall be used for selecting these enclosures for use in specific locations other than hazardous (classified) locations. The enclosures are not intended to protect against conditions such as condensation, icing, corrosion, or contamination that may occur within the enclosure or enter via the conduit or unsealed openings.

Table 1.10.2.3 Enclosure Selection
Provides a Degree of Protection Against the following Environmental ConditionsFor Outdoor Use
Enclosure Type Number
33R3S3X3RX3SX44X66P
Incidental contact with the enclosed equipmentXXXXXXXXXX
RainXXXXXXXXXX
Windblown dustXXXXXXXX
HosedownXXXX
Corrosive agentsXXXXX
Temporary submersionXX
Prolonged submersionX
Provides a Degree of Protection Against the following Environmental ConditionsFor Indoor Use
Enclosure Type Number
1244X566P1212K13
Incidental contact with enclosed equipmentXXXXXXXXXX
Falling dirtXXXXXXXXXX
Falling liquids and light splashingXXXXXXXXX
Circulating dust, lint, fibers, and flyingsXXXXXXX
Settling airborne dust, lint, fibers, and flyingsXXXXXXXX
Hosedown and splashing waterXXXX
Oil and coolant seepageXXX
Oil and coolant spraying and splashingX
Corrosive agentsXX
Temporary submersionXX
Prolonged submersionX
FPN No. 1: The term raintight is typically used in conjunction with Enclosure Types 3, 3S, 3SX, 3X, 4, 4X, 6, and 6P. The term rainproof is typically used in conjunction with Enclosure Types 3R and 3RX. The term watertight is typically used in conjunction with Enclosure Types 4, 4X, 6, and 6P. The term driptight is typically used in conjunction with Enclosure types 2, 5, 12, 12K, and 13. The term dusttight is typically used in conjunction with Enclosure Types 3, 3S, 3SX, 5, 12, 12K, and 13.
FPN No. 2: Ingress protection (IP) ratings may be found in ANSI/IEC 60529, Degrees of Protection Provided by Enclosures. IP ratings are not a substitute for Enclosure Type ratings.

1.10.3 Over 1000 Volts, Nominal

1.10.3.1 General

Conductors and equipment used on circuits over 1000 volts, nominal, shall comply with Part 1.10.1 and with 1.10.3.1 through 1.10.3.12, which supplement or modify Part 1.10.1. In no case shall the provisions of this part apply to equipment on the supply side of the service point.

1.10.3.2 Enclosure for Electrical Installations

Electrical installations in a vault, room, or closet or in an area surrounded by a wall, screen, or fence, access to which is controlled by a lock(s) or other approved means, shall be considered to be accessible to licensed electrical practitioner or qualified person under the supervision of a licensed electrical practitioner only. The type of enclosure used in a given case shall be designed and constructed according to the nature and degree of the hazard(s) associated with the installation.

For installations other than equipment as described in 1.10.3.2(D), a wall, screen, or fence shall be used to enclose an outdoor electrical installation to deter access by persons who are not qualified. A fence shall not be less than 2 100 mm in height or a combination of 1 800 mm or more of fence fabric and a 300 mm or more extension utilizing three or more strands of barbed wire or equivalent. The distance from the fence to live parts shall be not less than given in Table 1.10.3.2.

FPN: See Article 4.50 for construction requirements for transformer vaults.

Table 1.10.3.2 Minimum Distance from Fence to Live Parts
Nominal VoltageMinimum Distance to Live Parts (m)
1001 – 137993.05
13,800 – 230,0004.57
Over 230,0005.49
Note: For clearances of conductors for specific system voltages and typical BIL ratings, see ANSI/IEEE C2-2012, National Electrical Safety Code.

(A) Electrical Vaults

Where an electrical vault is required or specified for conductors and equipment 1.10.3.2(A)(1) to (A5) shall apply.

(1) Walls and Roof

The walls and roof shall be constructed of materials that have adequate structural strength for the conditions, with a minimum wire rating of 3 hours. For the purpose of this section, studs and wallboard construction shall not be permitted.

(2) Floors

The floor of vaults in contact with the earth shall be of concrete that is not less than 100 mm thick, but where the vault is constructed with a vacant space or other stories below it, the floor shall have adequate structural strength for the load imposed on it and a minimum fire resistance of 3 hours.

(3) Doors

Each doorway leading into a vault from the building interior shall be provided with a tight-fitting door that has a minimum fire rating of 3 hours. It shall be permitted to have such a door for an exterior wall opening where conditions warrant.

Exception to (1), (2), and (3): Where the vault is protected with automatic sprinkler, water spray, carbon dioxide, or halon, construction with a 1-hour rating shall be permitted.

(4) Locks

Doors shall be equipped with locks, and doors shall be kept locked, with access allowed only to qualified persons. Personnel doors shall swing out and be equipped with panic bars, pressure plates, or other devices that are normally latched but that open under simple pressure.

(5) Transformers

Where a transformer is installed in a vault as required in Article 4.50, the vault shall be constructed in accordance with the requirements of Part 4.50.3.

FPN No.1: For additional information, see ANSI/ASTM E119-2015a, Method for Fire Tests of Building Construction and Materials, and NFPA 80-2016, Standard for Fire Doors and Other Opening Protectives.

FPN No. 2: A typical 3-hour construction is 150 mm thick reinforced concrete.

(B) Indoor Installations

(1) In Places Accessible to Unqualified Persons

Indoor electrical installations that are accessible to unqualified persons shall be made with metal-enclosed equipment. Switchgear, transformers, pull boxes, connection boxes, and other similar associated equipment shall be marked with appropriate caution signs. Openings in ventilated dry-type transformers or similar openings in other equipment shall be designed so that foreign objects inserted through these openings are deflected from energized parts.

(2) In Places Accessible to Licensed Electrical Practitioner or Qualified Person Under the Supervision of a Licensed Electrical Practitioner Only

Indoor electrical installations considered accessible only to licensed electrical practitioner or qualified person under the supervision of a licensed electrical practitioner in accordance with this section shall comply with 1.10.3.5, 1.10.3.7, and 4.90.2.4.

(C) Outdoor Installations

(1) In Places Accessible to Unqualified Persons

Outdoor electrical installations that are open to unqualified persons shall comply with Parts 2.25.1, 2.25.2, and 2.25.3.

FPN: For clearances of conductors for system voltages over 600 volts, nominal, see ANSI C2-2002, National Electrical Safety Code, or the Philippine Electrical Code Part 1, 2008.

(2) In Places Accessible to Licensed Electrical Practitioner or Qualified Person Under the Supervision of a Licensed Electrical Practitioner Only

Outdoor electrical installations that have exposed live parts shall be accessible to licensed electrical practitioner or qualified person under the supervision of a licensed electrical practitioner only in accordance with the first paragraph of this section and shall comply with 1.10.3.5, 1.10.3.7, and 4.90.2.4.

(D) Enclosed Equipment Accessible to Unqualified Persons

Ventilating or similar openings in equipment shall be designed such that foreign objects inserted through these openings are deflected from energized parts. Where exposed to physical damage from vehicular traffic, suitable guards shall be provided. Equipment located outdoors and accessible to the unqualified persons shall be designed such that exposed nuts or bolts cannot be readily removed, permitting access to live parts. . Where equipment is accessible to the unqualified persons and the bottom of the enclosure is less than 2 400 mm above the floor or grade level, the enclosure door or hinged cover shall be kept locked. Doors and covers of enclosures used solely as pull boxes, splice boxes, or junction boxes shall be locked, bolted, or screwed on. Underground box covers that weigh over 45.4 kg shall be considered as meeting this requirement.

1.10.3.3 Work Space About Equipment

Sufficient space shall be provided and maintained about electric equipment to permit ready and safe operation and maintenance of such equipment. Where energized parts are exposed, the minimum clear work space shall not be less than 2 000 mm high (measured vertically from the floor or platform) or less than 900 mm wide (measured parallel to the equipment). The depth shall be as required in 1.10.3.5(a). In all cases, the work space shall permit at least a 90 degree opening of doors or hinged panels.

1.10.3.4 Entrance and Access to Work Space

(A) Entrance

At least one entrance not less than 600 mm wide and 2 000 mm high shall be provided to give access to the working space about electric equipment. Where the entrance has a personnel door(s), the door(s) shall open in the direction of egress and be equipped with panic bars, pressure plates, or other devices that are normally latched but open under simple pressure.

(1) Large Equipment

On switchboard and control panels exceeding 1 800 mm in width, there shall be one entrance at each end of the equipment. A single entrance to the required working space shall be permitted where either of the conditions in 1.10.3.4(A)(1)a or (A)(1)b is met.

  • a. Unobstructed Exit. Where the location permits a continuous and unobstructed way of exit travel, a single entrance to the working space shall be permitted.
  • b. Extra Working Space. Where the depth of the working space is twice that required by 1.10.3.5(a), a single entrance shall be permitted. It shall be located so that the distance from the equipment to the nearest edge of the entrance is not less than the minimum clear distance specified in Table 1.10.3.5(A) for equipment operating at that voltage and in that condition.
(2) Guarding

Where bare energized parts at any voltage or insulated energized parts above 1000 volts, nominal, to ground are located adjacent to such entrance, they shall be suitably guarded.

(3) Personnel Doors

Where there is a personnel doors(s) intended for entrance to and egress from the working space less than 7600 mm from the nearest edges of the working space, the door(s) shall open in the direction of egress and be equipped with listed panic hardware.

(B) Access

Permanent ladders or stairways shall be provided to give safe access to the working space around electric equipment installed on platforms, balconies, or mezzanine floors or in attic or roof rooms or spaces.

1.10.3.5 Work Space and Guarding

(A) Working Space

Except as elsewhere required or permitted in this Code, the minimum clear working space in the direction of access to live parts of electrical equipment shall not be less than specified in Table 1.10.3.5(A). Distances shall be measured from the live parts, if such are exposed, or from the enclosure front or opening if such are enclosed.

Exception : Working space shall not be required in back of equipment such as switchgear or control assemblies where there are no renewable or adjustable parts (such as fuses or switches) on the back and where all connections are accessible from locations other than the back. Where rear access is required to work on deenergized parts on the back of enclosed equipment, a minimum working space of 750 mm horizontally shall be provided.

Table 1.10.3.5(A) Minimum Depth of Clear Working Space at Electrical Equipment
Nominal Voltage to GroundMinimum Clear Distance (mm)
Condition 1Condition 2Condition 3
1001 – 2500 V90012001500
2501 – 9000 V120015001800
9001 – 25000 V150018002800
25001 – 75 kV180025003000
Above 75 kV250030003700
Note: Where the conditions are as follows:
Condition 1 – Exposed live parts on one side of the working space and no live or grounded parts on the other side of the working space, or exposed live parts on both sides of the working space that are effectively guarded by insulating materials.
Condition 2 – Exposed live parts on one side of the working space and grounded parts on the other side of the working space. Concrete, brick, or tile walls shall be considered as grounded.
Condition 3 – Exposed live parts on both sides of the working space.
(B) Separation from Low-Voltage Equipment

Where switches, cutouts, or other equipment operating at 1000 volts, nominal, or less are installed in a vault, room, or enclosure where there are exposed live parts or exposed wiring operating at over 1000 volts, nominal, the high voltage equipment shall be effectively separated from the space occupied by the low-voltage equipment by a suitable partition, fence, or screen.

Exception : Switches or other equipment operating at 600 volts, nominal, or less and serving only equipment within the high-voltage vault, room, or enclosure shall be permitted to be installed in the high voltage vault, room or enclosure without a partition, fence, or screen if accessible to licensed electrical practitioner or qualified person under the supervision of a licensed electrical practitioner only.

(C) Locked Rooms or Enclosures

The entrance to all buildings, vaults, rooms, or enclosures containing exposed live parts or exposed conductors operating at over1000 volts, nominal, shall be kept locked unless such entrances are under the observation of a licensed electrical practitioner or qualified person under the supervision of a licensed electrical practitioner at all times.

Where the voltage exceeds 1000 volts, nominal, permanent and conspicuous warning signs shall be provided, reading as follows:

DANGER - HIGH VOLTAGE - KEEP OUT
(D) Illumination

Illumination shall be provided for all working spaces about electrical equipment. Control by automatic means only shall be permitted. The lighting outlets shall be arranged so that persons changing lamps or making repairs on the lighting system are not endangered by live parts or other equipment.

The points of control shall be located so that persons are not likely to come in contact with any live part or moving part of the equipment while turning on the lights.

(E) Elevation of Unguarded Live Parts

Unguarded live parts above working space shall be maintained at elevations not less than required by Table 1.10.3.5(E).

Table 1.10.3.5(E) Elevation of Unguarded Live Parts Above Working Space
Nominal Voltage Between PhasesElevation (m)
1001 – 7500 V3.05
7501 – 35000 V4.57
Over 35 kVAdd 9.5 mm per kV above 35kV
(F) Protection of Service Equipment, Switchgear, and Industrial Control Assemblies

Pipes or ducts foreign to the electrical installation and requiring periodic maintenance or whose malfunction would endanger the operation of the electrical system shall not be located in the vicinity of the service equipment, metal-enclosed power switchgear, or industrial control assemblies. Protection shall be provided where necessary to avoid damage from condensation leaks and breaks in such foreign systems. Piping and other facilities shall not be considered foreign if provided for fire protection of the electrical installation.

1.10.3.7 Circuit Conductors

Circuit conductors shall be permitted to be installed in raceways; in cable trays; as metal-clad cable, as bare wire, cable, and busbars; or as Type MV cables or conductors as provided in 3.0.2.7, 3.0.2.9, 3.0.2.10, and 3.0.2.20. Bare live conductors shall conform with 4.90.2.4.

Insulators, together with their mounting and conductor attachments, where used as supports for wires, single-conductor cables, or busbars, shall be capable of safely withstanding the maximum magnetic forces that would prevail when two or more conductors of a circuit were subjected to short-circuit current.

Exposed runs of insulated wires and cables that have a bare lead sheath or a braided outer covering shall be supported in a manner designed to prevent physical damage to the braid or sheath. Supports for lead-covered cables shall be designed to prevent electrolysis of the sheath.

1.10.3.11 Temperature Limitation at Termination

Conductors shall be permitted to be terminated based on the 90°C temperature rating and ampacity as given in Table 3.10.2.50(C)(67) through Table 3.10.2.50(C)(86), unless otherwise identified.

1.10.3.12 Inspections and Tests

(A) Pre-energization and Operating Tests

Where required elsewhere in this Code, the complete electrical system design, including settings for protective, switching, and control circuits shall be prepared in advance and made available on requests to the Office of the Building Official/EE (OBO/EE) and shall be tested when first installed on-site.

(B) Test Report

A test report covering the results of the tests required in 1.10.3.12(A) shall be available to the Office of the Building Official/EE (OBO/EE) prior to energization and made available to those authorized to install, operate, test, and maintain the system.

1.10.4 Tunnel Installation Over 1000 Volts, Nominal

1.10.4.1General

(A) Covered

The provisions of this part shall apply to the installation and use of high-voltage power distribution and utilization equipment that is portable, mobile, or both, such as substations, trailers, cars, mobile shovels, draglines, hoists, drills, dredges, compressors, pumps, conveyors, underground excavators, and the like.

(B) Other Articles

The requirements of this part shall be additional to, or amendatory of, those prescribed in Articles 1.0 through 4.90 of this Code. Special attention shall be paid to Article 2.50.

(C) Protection Against Physical Damage

Conductors and cables in tunnels shall be located above the tunnel floor and so placed or guarded to protect them from physical damage.

1.10.4.2 Overcurrent Protection

Motor-operated equipment shall be protected from overcurrent in accordance with Parts 4.30.3, 4.30.4, and 4.30.5. Transformers shall be protected from overcurrent in accordance with 4.50.1.3.

1.10.4.3 Conductors

High-voltage conductors in tunnels shall be installed in metal conduit or other metal raceway, Type MC cable, or other approved multiconductor cable. Multiconductor portable cable shall be permitted to supply mobile equipment.

1.10.4.4 Bonding and Equipment Grounding Conductors

(A) Grounded and Bonded

All non–current-carrying metal parts of electric equipment and all metal raceways and cable sheaths shall be effectively grounded and bonded to all metal pipes and rails at the portal and at intervals not exceeding 300 m throughout the tunnel.

(B) Equipment Grounding Conductors

An equipment grounding conductor shall be run with circuit conductors inside the metal raceway or inside the multiconductor cable jacket. The equipment grounding conductor shall be permitted to be insulated or bare.

1.10.4.5 Transformers, Switches, and Electrical Equipment

All transformers, switches, motor controllers, motors, rectifiers, and other equipment installed below ground shall be protected from physical damage by location or guarding.

1.10.4.6 Energized Parts

Bare terminals of transformers, switches, motor controllers, and other equipment shall be enclosed to prevent accidental contact with energized parts.

1.10.4.7 Ventilation System Controls

Electrical controls for the ventilation system shall be arranged so that the airflow can be reversed.

1.10.4.8 Disconnecting Means

A switch or circuit breaker that simultaneously opens all ungrounded conductors of the circuit shall be installed within sight of each transformer or motor location for disconnecting the transformer or motor. The switch or circuit breaker for a transformer shall have an ampere rating not less than the ampacity of the transformer supply conductors. The switch or circuit breaker for a motor shall comply with the applicable requirements of Article 4.30.

1.10.4.9 Enclosures

Enclosures for use in tunnels shall be dripproof, weatherproof, or submersible as required by the environmental conditions. Switch or contactor enclosures shall not be used as junction boxes or as raceways for conductors feeding through or tapping off to other switches, unless the enclosures comply with 3.12.1.8.

1.10.5 Manholes and Other Electrical Enclosures Intended for Personnel Entry

1.10.5.1 General

Electric enclosures intended for personnel entry and specifically fabricated for this purpose shall be of sufficient size to provide safe work space about electric equipment with live parts that is likely to require examination, adjustment, servicing, or maintenance while energized. Such enclosures shall have sufficient size to permit ready installation or withdrawal of the conductors employed without damage to the conductors or to their insulation. They shall comply with the provisions of this part.

Exception : Where electric enclosures covered by 1.10.5 are part of an industrial wiring system operating under conditions of maintenance and supervision that ensure that only licensed electrical practitioner or qualified person under the supervision of a licensed electrical practitioner monitor and supervise the system, they shall be permitted to be designed and installed in accordance with appropriate engineering practice. If required by the Office of the Building Official/EE, design documentation shall be provided.

1.10.5.2 Strength

Manholes, vaults, and their means of access shall be designed under qualified engineering supervision and shall withstand all loads likely to be imposed on the structures.

FPN: See ANSI C2-2007, National Electrical Safety Code, or the Philippine Electrical Code Part 2, 2008 for additional information on the loading that can be expected to bear on underground enclosures.

1.10.5.3 Cabling Work Space

A clear work space not less than 900 mm wide shall be provided where cables are located on both sides, and not less than 750 mm where cables are only on one side. The vertical headroom shall not be less than 1 800 mm unless the opening is within 300 mm, measured horizontally, of the adjacent interior side wall of the enclosure.

Exception : A manhole containing only one or more of the following shall be permitted to have one of the horizontal work space dimensions reduced to 600 mm where the other horizontal clear work space is increased so the sum of the two dimensions is not less than 1 800 mm:

(1) Optical fiber cables as covered in Article 7.70

(2) Power-limited fire alarm circuits supplied in accordance with 7.60.3.1(A)

(3) Class 2 or Class 3 remote-control and signaling circuits, or both, supplied in accordance with 7.25.3.1.

1.10.5.4 Equipment Work Space

Where electric equipment with live parts that is likely to require examination, adjustment, servicing, or maintenance while energized is installed in a manhole, vault, or other enclosure designed for personnel access, the work space and associated requirements in 1.10.2.1 shall be met for installations operating at 1000 volts or less. Where the installation is over 1000 volts, the work space and associated requirements in 1.10.3.5 shall be met. A manhole access cover that weighs over 45 kg shall be considered as meeting the requirements of 1.10.3.5(C).

1.10.5.5 Bending Space for Conductors

 Bending space for conductors operating at 600 volts or below shall be provided in accordance with the requirements of 3.14.2.14. Conductors operating over 1000 volts shall be provided with bending space in accordance with 3.14.4.2(A) and 3.14.4.2(B), as applicable. All conductors shall be cabled, racked up, or arranged in an approved manner that provides ready and safe access for persons to enter for installation and maintenance.

Exception: Where 3.14.4.2(B) applies, each row or column of ducts on one wall of the enclosure shall be calculated individually, and the single row or column that provides the maximum distance shall be used.

1.10.5.6 Access to Manholes

(A) Dimensions

Rectangular access openings shall not be less than 650 mm × 550 mm. Round access openings in a manhole shall not be less than 650 mm in diameter.

Exception: A manhole that has a fixed ladder that does not obstruct the opening or that contains only one or more of the following shall be permitted to reduce the minimum cover diameter to 600 mm:

(1) Optical fiber cables as covered in Article 7.70

(2) Power-limited fire alarm circuits supplied in accordance with 7.60.3.1

(3) Class 2 or Class 3 remote-control and signaling circuits, or both, supplied in accordance with 7.25.3.1.

(B) Obstructions

Manhole openings shall be free of protrusions that could injure personnel or prevent ready egress.

(C) Location

Manhole openings for personnel shall be located where they are not directly above electric equipment or conductors in the enclosure. Where this is not practicable, either a protective barrier or a fixed ladder shall be provided.

(D) Covers

Covers shall be over 45 kg or otherwise designed to require the use of tools to open. They shall be designed or restrained so they cannot fall into the manhole or protrude sufficiently to contact electrical conductors or equipment within the manhole.

(E) Marking

Manhole covers shall have an identifying mark or logo that prominently indicates their function, such as “electric.”

1.10.5.7 Access to Vaults and Tunnels

(A) Location

Access openings for personnel shall be located where they are not directly above electric equipment or conductors in the enclosure. Other openings shall be permitted over equipment to facilitate installation, maintenance, or replacement of equipment.

(B) Locks

In addition to compliance with the requirements of 1.10.3.5, if applicable, access openings for personnel shall be arranged such that a person on the inside can exit when the access door is locked from the outside, or in the case of normally locking by padlock, the locking arrangement shall be such that the padlock can be closed on the locking system to prevent locking from the outside.

1.10.5.8 Ventilation

Where manholes, tunnels, and vaults have communicating openings into enclosed areas used by the public, ventilation to open air shall be provided wherever practicable.

1.10.5.9 Guarding

Where conductors or equipment, or both, could be contacted by objects falling or being pushed through a ventilating grating, both conductors and live parts shall be protected in accordance with the requirements of 1.10.2.2(A)(2) or 1.10.3.2(B)(1), depending on the voltage.

1.10.5.10 Fixed Ladders

Fixed ladders shall be corrosion resistant.