Article 100 NEC Definitions (Letter H)

Habitable Room
A room in a building designated for living, sleeping, eating, or cooking. Excludes bathrooms, toilet rooms, closets, hallways, storage or utility spaces, and similar areas.
Source: CMP—2

Handhole Enclosure
An enclosure for underground systems with an open or closed bottom, allowing personnel to reach in, but not enter, for installing, operating, or maintaining equipment or wiring.
Source: CMP—9

Hazard Current
For a given set of connections in an isolated power system, it is the total current that would flow through a low impedance if connected between any isolated conductor and ground.
Source: [99:3.3.72] (517) (CMP—15)

Hazard Current, Fault
The hazard current in an isolated power system with all devices connected, excluding the line isolation monitor.
Source: [99:3.3.72.1] (517) (CMP—15)

Monitor Hazard Current
The hazard current of the line isolation monitor alone in an isolated power system.
Source: [99:3.3.72.2] (517) (CMP—15)

Total Hazard Current
The hazard current in an isolated system with all devices, including the line isolation monitor, connected.
Source: [99:3.3.72.3] (517) (CMP—15)

Header
Transverse metal raceways for electrical conductors, providing access to predetermined cells in a precast cellular concrete floor, allowing the installation of conductors from a distribution center to the floor cells.
Source: CMP—8

Health Care Facilities
Buildings or portions of buildings where medical, dental, psychiatric, nursing, obstetrical, or surgical care is provided, including hospitals, nursing homes, clinics, and medical offices.
Source: [99:3.3.73] (CMP—15)
Informational Note: Examples include hospitals, nursing homes, limited care facilities, clinics, and ambulatory care centers.

Health Care Facility’s Governing Body
The person or group responsible for the legal operation of a health care facility.
Source: [99:3.3.74] (517) (CMP—15)

Heating Equipment
Equipment used for heating purposes where heat is generated by induction or dielectric methods.
Source: CMP—12

Heating Panel
A complete assembly that includes a junction box or a length of flexible conduit for connection to a branch circuit.
Source: CMP—17

Heating Panel Set
A rigid or nonrigid assembly provided with nonheating leads or a terminal junction assembly suitable for connection to a wiring system.
Source: CMP—17

Heating System
A complete system that consists of components like heating elements, fastening devices, nonheating circuit wiring, temperature controllers, safety signs, junction boxes, raceways, and fittings.
Source: CMP—17

Heating System, Impedance
A system in which heat is generated in an object (such as a pipe or rod) by direct current flow through the object, connected to an ac voltage source from an isolating transformer. The object may be embedded in the surface to be heated or exposed.
Source: CMP—17

Heating System, Induction
A system that generates heat in a pipeline or vessel wall by inducing current from an external isolated ac field.
Source: CMP—17

Heating System, Skin Effect
A system where heat is generated on the inner surface of a ferromagnetic envelope, embedded or fastened to the surface to be heated. An insulated conductor is routed through and connected to the envelope, with both connected to an ac voltage source from an isolating transformer.
Source: CMP—17
Informational Note: The envelope is often embedded or fastened to the surface to be heated.

Hermetic Refrigerant Motor-Compressor
A combination of a compressor and motor enclosed in the same housing, with no external shaft or shaft seals, operating in the refrigerant.
Source: CMP—11

Hoistway
A vertical opening or space where an elevator or dumbwaiter is designed to operate.
Source: CMP—12

Hospital
A building or portion of a building used for 24-hour medical, psychiatric, obstetrical, or surgical care for four or more inpatients.
Source: [101:3.3.152] (CMP—15)

Host Sign
A sign or lighting system already installed that is designated for field conversion using a retrofit kit.
Source: CMP—18

Hydromassage Bathtub
A permanently installed bathtub equipped with a recirculating piping system, pump, and associated equipment, designed to accept, circulate, and discharge water upon each use.
Source: CMP—17

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Summary Table: Terms and Definitions

Term	Definition
Habitable Room	A room used for living, sleeping, eating, or cooking, excluding certain areas.
Handhole Enclosure	An underground enclosure for equipment maintenance, with restricted access.
Hazard Current	The total current that would flow through a low impedance in an isolated system.
Hazard Current, Fault	The hazard current with all devices connected, excluding the line isolation monitor.
Monitor Hazard Current	The hazard current of the line isolation monitor alone.
Total Hazard Current	The hazard current with all devices, including the line isolation monitor.
Header	Metal raceways providing access to electrical conductors in floor cells.
Health Care Facilities	Buildings where medical, dental, psychiatric, or surgical care is provided.
Health Care Facility’s Governing Body	The group or person responsible for the legal operation of the facility.
Heating Equipment	Equipment that generates heat by induction or dielectric methods.
Heating Panel	An assembly with a junction box or flexible conduit for circuit connection.
Heating Panel Set	An assembly suitable for wiring system connections, without heating leads.
Heating System	A complete system with heating elements, controllers, and safety components.
Heating System, Impedance	A system where heat is generated by current flow through an object.
Heating System, Induction	A system generating heat in a wall by inducing current from an external ac field.
Heating System, Skin Effect	A system where heat is generated on the inner surface of a ferromagnetic envelope.
Hermetic Refrigerant Motor-Compressor	A combined motor and compressor in the same housing, operating in refrigerant.
Hoistway	A vertical opening for elevator or dumbwaiter operation.
Hospital	A facility providing 24-hour care for four or more inpatients.
Host Sign	A sign or lighting system designated for retrofit field conversion.
Hydromassage Bathtub	A bathtub designed for water circulation and discharge with a pump and system.