Article 504 Intrinsically Safe Systems

Table of contents:

Article 505 Class I, Zone 0, 1, and 2 Locations

If this article is used, the equipment selection, wiring methods, and area classification must be under the supervision of a qualified registered professional engineer.

505.1

Scope

505.2

Definitions

505.3

Other Articles

505.4

General

505.5

Classification of Locations

505.6

Material Groups

505.7

Special Precautions

505.8

Protection Techniques

505.9

Equipment

505.15

Wiring Methods

505.16

Sealing and Drainage

505.17

Flexible Cords, Class I, Zones 1 and 2

505.18

Conductors and Conductor Insulation

505.19

Uninsulated Exposed Parts

505.20

Equipment Requirements

505.21

Multiwire Branch Circuits

505.22

Increased Safety "e" Motors and Generators

505.25

Grounding and Bonding

 

Article 506 Zone 20, 21, and 22 Locations for Flammable Dusts, Fibers, and Flyings

506.1

Scope

506.2

Definitions

506.4

General

506.5

Classification of Locations

506.6

Special Precautions

506.8

Protection Techniques

506.9

Equipment Requirements

506.15

Wiring Methods

506.16

Sealing

506.17

Flexible Cords

506.20

Equipment Installation

506.21

Multiwire Branch Circuits

506.25

Grounding and Bonding

 

Article 510 Hazardous (Classified) LocationsSpecific

Articles 511 through 517 cover specific locations that might be hazardous. The following article titles are listed for reference: Article 511Commercial Garages, Repair and Storage; Article 513Aircraft Hangars; Article 514Motor Fuel Dispensing Facilities; Article 515Bulk Storage Plants; Article 516Spray Application, Dipping, and Coating Processes.

Article 517 Health Care Facilities

I. General

FPN: Rules that are followed by a reference in brackets contain text that has been extracted from NFPA-2002, Standard for Health Care Facilities. Only editorial changes were made to the extracted text to make it consistent with the NEC.

517.1

Scope

Electrical construction and installation criteria for health care facilities that provide service to human beings are covered in this article. Performance, maintenance, and testing criteria are covered in NFPA 99 and other appropriate health care documents. Veterinary facilities are not covered. The reader is referred to NFPA 99.

Parts II and III are intended to be applied to both single-function buildings and to applicable portions of multifunction buildings. The example used is a doctor's examining room in a residential custodial care facility having to comply with Section 517.10.

517.2

Definitions

Many definitions are listed in this section that are not covered in Article 100. These are specific to health care facilities. The reader should refer to these in the Code.

II. Wiring Design and Protection

517.10

Applicability

Generally, this part applies to all health care facilities. Part II does not apply to business offices, corridors, waiting rooms, and similar areas in clinics, medical and dental offices, and outpatient clinics, and if wired in accordance with Chapters 1, 2, 3, and 4 of the Code, patient sleeping areas in nursing homes and limited care facilities.

517.11

General Installation-Construction Criteria

It is important that the system installed maintain low potential differences between exposed conductive surfaces which are likely to become energized and the patient could contact.

517.12

Wiring Methods

All the requirements of Chapters 1 through 4 must be followed unless they are changed in this article.

517.13

Grounding of Receptacles and Fixed Electric Equipment in Patient Care Areas

(A) Wiring Methods. Branch circuits serving patient care areas must have a ground path for fault current by being installed in a metal raceway or cable having a metallic armor or sheath assembly which qualifies as an equipment grounding return path. This is in addition to all other requirements of this section.

(B) Insulated Equipment Grounding Conductor. If operated over 100 V, the grounding terminal of all receptacles and noncurrent-carrying areas of fixed equipment that a person can contact and may become energized must be grounded using an insulated copper conductor. It must be sized according to Table 250.122 and be installed in a metal raceway or as a part of listed cables that have metallic armor or sheath assembly with the branch-circuit conductors supplying the equipment or receptacle. There are two exceptions.

517.14

Panelboard Bonding

The equipment grounding busses of all panelboards serving the same patient vicinity must be bonded together. This is to be done using a continuous insulated copper conductor 10 AWG or larger. If two or more panelboards serve the same patient vicinity and are served from different transfer switches in the emergency system, then the equipment grounding terminal buses have to be bonded together with an insulated continuous copper conductor. The conductor cannot be smaller than 10 AWG.

517.16

Receptacles with Insulated Grounding Terminals

517.17

Ground-Fault Protection

(A) Applicability. Hospitals and other buildings that have or provide essential utilities or services for critical care areas or use life support equipment must comply with 517.17.

(B) Feeders. If ground-fault protection is used at the service disconnect as per Section 230.95 or 215.10, an additional step is needed at the next level of feeder away from the service. There are three areas listed where the additional level of ground- fault protection cannot be installed.

(C) Selectivity. The system must be fully selective. Six-cycle separation between the levels is required.

(D) Testing

517.18

General Care Areas

(A) Patient Bed Location. Each patient bed location must have at least two branch circuits, at least one of them must originate from the normal system and one from the emergency system. All branch circuits on the normal system must come from the same panel-board. There are three exceptions to this.

(B) Patient Bed Location Receptacles. Each location must have at least four receptacles, either single, duplex, or a combination. They must all be hospital grade and grounded with an insulated copper conductor in accordance with Table 250.122. There are two exceptions to this.

(C) Pediatric Locations. The receptacles must be listed tamper resistant or have a listed tamper resistant cover.

517.19

Critical Care Areas

(A) Patient Bed Location Branch Circuits. Each patient bed location must have at least two branch circuits, at least one from the normal system and one from the emergency system. One circuit on the emergency system that supplies no other bed location must be available at each bed location. All branch circuits from the normal system must come from one panelboard. The emergency receptacles must be identified and have the panelboard and circuit number of its supply noted. There are two exceptions.

(B) Patient Bed Location Receptacles. Each location must have at least six receptacles, either single, duplex, or a combination of both. At least one must be connected to the normal system or an emergency system supplied by a different transfer switch than the other receptacles in that location. They must all be hospital grade and grounded with an insulated copper conductor to the reference grounding point.

(C) Patient Vicinity Grounding and Bonding (Optional). A patient equipment grounding point is allowed in the patient vicinity. It can have grounding and bonding jacks listed for that purpose. All the grounding terminals on the receptacles must be connected to the patient equipment grounding point if supplied with an equipment bonding jumper no smaller than 10 AWG. This jumper can be looped or run centrically.

(D) Panelboard Grounding. Grounding of panelboards and switchboards must be accomplished if a grounded distribution system is used and metal feeder raceway or Type MC or MI cable is used. There are three acceptable means noted for use at each termination or junction point in the system.

(E) Additional Protective Techniques in Critical Care Areas (Optional). Isolated power systems are permitted.

(F) Isolated Power System Grounding

(G) Special-Purpose Receptacle Grounding

517.20

Wet Locations

(A) In a wet location two methods can be used to protect personnel. Either a ground-fault circuit interrupter can be used if power interruption is acceptable or an isolated power supply can be used. There is an exception.

(B) Isolated power supplies must conform to Section 517.160.

517.21

Ground-Fault Circuit Protection for Personnel

Not required for receptacles in critical care areas that have the toilet and basin in the patient room.

III. Essential Electrical System

517.25

Scope

This system is needed to provide light and power for systems essential to life safety and orderly cessation of procedures during a power failure of the normal electrical supply. The types of structures and services are listed in the Code. The reader is also referred to NFPA 99-2002 for further information as to the need for an essential electrical system.

517.26

Application of Other Articles

517.30

Essential Electrical Systems for Hospitals

(A) Applicability

(B) General. The system is comprised of two separate systems, the emergency system and the equipment system. The emergency systems has a life safety branch and a critical branch. The equipment system supplies power to major equipment. The number of transfer switches depends on many design considerations. One switch can be used for a system with a maximum demand of 150 kVA (120 kw). Loads not noted in Article 517 must have their own transfer switch and must not transfer if it overloads the generator and must automatically shed if the generating equipment becomes overloaded. Continguous facilities can be served by the hospital power and alternate power sources. [NFPA99, 13.3.4.3]

(C) Wiring Requirements. The life safety and critical branch must be kept separate from all other wiring and equipment except for four conditions. The wiring of the emergency system must be mechanically protected. There are five methods accepted. When isolated power systems are used in anesthetizing locations or special environments, each must be supplied by a separate circuit.

(D) Capacity of Systems. The system must be able to supply the entire load. There is now a statement on demand calculations.

(E) Receptacle Identification. Must be distinctively marked. [NFPA99, 4.4.2.2.4.2(B)]

517.31

Emergency System

This is divided into two required branches, the life safety and the critical. This system must be automatically restored to power within 10 seconds of the loss of the normal supply. [NFPA99, 4.4.2.2.2.1, 4.4.3.1]

517.32

Life Safety Branch

The Code lists all the items that are required to be on the life safety branch. They are basically illumination of means of egress, exit signs, alarm and alerting systems, communication systems, generator set location, elevators, and automatic doors. The reader is referred to the Code for the exact list. No function other than those listed can be connected to the life safety branch.

517.33

Critical Branch

The Code lists all the items that are required to be on the critical branch. They are basically task illumination and selected receptacles for the isolated power system, anesthetizing locations, patient care areas, additional specialized areas, nurse call systems, blood, bone and tissue bank, telephone equipment room and closets, special areas, and special circuits. The critical branch can be divided into two or more branches. The reader is referred to the Code for the exact list.

517.34

Equipment Source Connection to Alternate Power Source

This section describes what equipment must be placed on the equipment system. It also describes how the system is energized (i.e., automatic, delayed automatic, and manually). The reader is referred to the Code for the exact requirements.

517.35

Sources of Power

(A) Two Independent Sources of Power. There must be a normal source of power and an alternate source of power for use when the normal source is interrupted. [NFPA99, 4.4.1.1.4]

(B) Alternate Source of Power. This must be located on the premises and be a generator driven by a prime mover, another generator when the normal source is a generator, or an outside utility company when the normal source is a generator.

(C) Location of Essential Electrical System Components

517.40

Essential Electrical Systems for Nursing Homes and Limited Care Facilities

(A) Applicability

(B) Inpatient Hospital Care Facilities. If the facility provides inpatient hospital care, it must comply with the requirements of Part III, 517.30 through 517.35.

(C) Facilities Contiguous with Hospitals. These can have their systems supplied by the hospital. The reader is again referred to NFPA 99-2002 for performance, maintenance, and testing requirements.

517.41

Essential Electrical Systems

(A) General. The systems for nursing homes and limited care facilities must have two separate branches, the life safety branch and the critical branch. [NFPA99, FPN ANNEX A 4.5.2.2.1]

(B) Transfer Switches. The number of transfer switches depends on design. One transfer switch is permitted if the load is not more than 150 kVA. [NFPA99, 4.5.2.2.1]

(C) Capacity of System. The system must be capable of supplying the entire load, that is required on the essential electrical system.

(D) Separation from Other Circuits. The life safety branch must be kept separate from all other wiring and equipment. There are three exceptions.

(E) Receptacle Identification. The receptacles or cover plates must have a distinctive color or marking.

517.42

Automatic Connection to Life Safety Branch

The life safety branch must be automatically restored to power after 10 seconds of loss of the normal source of supply. This branch is referred to as the emergency system in NFPA 99-2002. The life safety branch basically supplies power for illumination of means of egress, exit signs, alarm and alerting systems, communication systems, dining and recreation areas, generator set location, and elevators. Refer to the Code for complete requirements. No function other than those listed can be connected to the life safety branch. For elevators [NFPA99, 4.4.2.2.2.2(6) and 4.5.2.2.2(7)]

517.43

Connection to Critical Branch

This section describes what must be connected to the critical branch and how it is to be energized from the essential electrical system (i.e., automatic, delayed automatic, or manual).

517.44

Sources of Power

(A) Two Independent Sources of Power. There must be a normal source of power and an alternate source of power for use when the normal source is interrupted. [NFPA99, 4.4.1.1.4]

(B) Alternate Source of Power. This must be located on the premises and be a generator driven by a prime mover. There is an exception to this when the normal source is a generator. In that case the alternate source can be either another generator or an outside utility company. There is also an exception where battery units may be used in nursing homes or limited-care facilities meeting the requirements of Section 517.40(A), Exception. [NFPA99, 17.3.4.1, 18.3.4.1.1]

(C) Location of Essential Electrical System Components

517.45

Essential Electrical Systems for Other Health Care Facilities

(A) Essential Electrical Distribution. A battery or generator system must be used for the essential electrical distribution system. [NFPA 99-2002]

(B) Electrical Life Support Equipment. An essential electrical distribution system described in 517.30 through 517.35 must be used if electrical life support equipment is required. [NFPA 99: 14.3.4.2.1]

(C) Critical Care Areas. An essential electrical distribution system as described in 527.30 through 517.35 must be used where critical care areas are located. [NFPA99, 14.3.4.2.2]

(D) Power Systems. Battery systems must follow the requirements of Article 700 and generator systems must follow the requirements of 517.30 through 517.35.

IV. Inhalation Anesthetizing Locations

The reader is again referred to NFPA 99-2002.

517.60

Anesthetizing Location Classification

These are classified as hazardous (classified) or other-than-hazardous (classified).

517.61

Wiring and Equipment

517.62

Grounding

517.63

Grounded Power Systems in Anesthetizing Locations

517.64

Low-Voltage Equipment and Instruments

 

V. X-Ray Installations

517.71

Connection to Supply Circuit

517.72

Disconnecting Means

517.73

Rating of Supply Conductors and Overcurrent Protection

517.74

Control Circuit Conductors

517.75

Equipment Installations

517.76

Transformers and Capacitors

517.77

Installation of High-Tension X-Ray Cables

517.78

Guarding and Grounding

 

VI. Communications, Signaling Systems, Data Systems, Fire Alarm Systems, and Systems Less than 120 Volts, Nominal

517.80

Patient Care Areas

517.81

Other than Patient Care Areas

517.82

Signal Transmission between Appliances

 

VII. Isolated Power Systems

517.160

Isolated Power Systems

(A) Installations

(B) Line Isolation Monitor

The following article titles are listed for reference: Article 518Assembly Occupancies; Article 520Theaters, Audience Areas of Motion Picture and Television Studios, Performance Areas, and Similar Locations; Article 525Carnivals, Circuses, Fairs, and Similar Events; Article 530Motion Picture and Television Studios and Similar Locations; Article 540Motion Picture Projection Rooms; Article 545Manufactured Buildings; Article 547Agricultural Buildings; Article 550Mobile Homes, Manufactured Homes, and Mobile Home Parks; Article 551Recreational Vehicles and Recreational Vehicle Parks; Article 552Park Trailers; Article 553Floating Buildings; Article 555Marinas and Boatyards; 590Temporary Installations.

, 7, and 8

Note: Those articles in Chapters 6, 7, and 8 not discussed in their entirety are listed here with article titles for reference purposes.

Article 90 Introduction

General

Wiring and Protection

Wiring Methods and Materials

Equipment for General Use

Special Occupancies

Special Equipment

Special Conditions

Tables

Annex C. Conduit and Tubing Fill Tables for Conductors and Fixture Wires of the Same Size

Annex D. Examples

Annex E. Types of Construction



Pocket Guide to the National Electrical Code 2005
Pocket Guide to the National Electrical Code(R), 2005 Edition (8th Edition)
ISBN: 0131480014
EAN: 2147483647
Year: 2004
Pages: 120

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