210.0 – H –

Hangers. See Supports.

Hazardous Location. An area or space where combustible dust, ignitable fibers, flammable liquids, volatile liquids, gases, vapors, or mixtures are or may be present in the air in quantities sufficient to produce explosive or ignitable mix tures.

Hazardous Process Piping (HPP). A process material piping or tubing conveying a liquid or gas that has a degreeof-hazard rating in health, flammability, or reactivity of Class 3 or 4, as ranked by the fire code.

Health Facilities. [OSHPD 1, 1R, 2, 3, 4, 5 & 6] Build- ings specified within the statutory authority of the Depart- ment of Health Care Access and Information/Office of Statewide Hospital Planning and Development.

Heat Pump. A refrigeration system that extracts heat from one substance and transfers it to another portion of the same substance or to a second substance at a higher temperature.

Heat Recovery Ventilation (HRV) System. A device intended to remove air from buildings, replace it with outside air, and in the process transfer heat from the warmer to the colder airstreams.

Heating Degree Day. A unit, based upon temperature difference and time, used in estimating fuel consumption and specifying nominal annual heating load of a building. For any one day when the mean temperature is less than 65°F (18°C), there exist as many degree days as there is Fahrenheit degrees difference in temperature between mean temperature for the day and 65°F (18°C).

Heating Equipment. Includes warm air furnaces, warm air heaters, combustion products vents, heating air-distribution ducts and fans, and all steam and hot water piping, together with all control devices and accessories installed as part of, or in connection with, any environmental heating system or appliance regulated by this code.

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DEFINITIONS

Hydronic System, District Ambient Temperature Loop. An endless closed loop system comprised of centralized pumping for the circulation of the contained fluid between multiple heat exchange devices installed on the loop. The endless loop may run exterior to conditioned spaces in order to serve multiple structures and the heat exchange devices installed within.

Hydronic System, Fifth Generation (5G) System Configurations . An advanced ambient temperature (ATL) system that distributes near-ambient-temperature water among and between end-use buildings that are equipped with water-source heat pumps or other watersource HVAC equipment. Such systems stand in contrast to fourth generation (4G) systems that distribute hot water or chilled water to buildings to serve facility loads.

Hydronic System, Fourth Generation (4G) Sys- tem Configurations. A district geothermal energy system that distributes hot water and cold water for direct

use in the conditioned space.

Hydronic System, Geothermal Closed-Loop. A closed-loop hydronic geothermal system that uses one or more heat exchangers submerged in a body of water or buried in the ground, fluidly coupled to one or more heat exchangers or heat pumps serving one or more conditioned spaces or thermal storage vessels.

Hydronic System, Geothermal Open-Loop. An open-loop geothermal energy system draws in surface or ground water, passes it through one or more heat exchangers and/or heat pumps, and then discharges the water back into the environment.

Hydronic System, Non-Oxygen Barrier Closed- Loop. A hydronic system constructed all or in part with pipe or tubing that permit the diffusion of oxygen into the system fluid.

Hydronic System, Open-Loop. A hydronic system that takes in a fluid mass from an external source, transfers thermal energy into or out of the fluid by means of one or more heat exchangers, and then returns the fluid mass all or in part to the external source.

Hydronic System, Vented Closed-Loop. A hydronic system wherein the system volume is occupied in part by a gas, such as air. The gaseous content is vented so as to modulate or regulate the gas pressure and/or the system fluid pressure.