HVAC Central Cooling & Heating

This article is about HVAC Central Equipment Cooling & Heating as per ASHRAE international standard of chapter 4. Following are main topics are covered in this article and ASHRAE document.

Central Equipment System Characteristics
Design Considerations of Central Equipment
Distribution System
Central Equipment Space Considerations
Central Plant Controls

Central cooling and or heating plants generate cooling and or heating in a single location for distribution to a number of areas in a single building or a whole campus or neighborhood. Central heating and cooling systems are utilized in nearly all classes of buildings, however notably in very giant buildings and complexes. They’re particularly suited to purposes the place maximizing tools service life and utilizing power and operational workforce effectively are vital.

The next facility sorts are good candidates for central cooling and or heating systems:

Campus environments with distribution to a number of buildings
High-rise facilities
Massive workplace buildings
Massive public meeting facilities, leisure complexes, stadiums, arenas, and conference and exhibition facilities
District cooling and heating plants
Shopping malls ,
Large condominiums, motels, and condo complexes
Academic facilities
Hospitals and different health care services
Industrial plants
Giant museums and similar institutions

HVAC SYSTEM CHARACTERISTICS

Central systems are characterized by large equipment situated in a chiller or boiler plant. Equipment configuration and ancillary equipment differ considerably relying on the facility’s use. See Chapter 1, HVAC System Analysis and Selection, for informationon selecting a central cooling or heating plant.

Equipment will be situated adjoining to the facility, or in distant stand-alone plants. Additionally, completely different mixtures of centralized and decentralized systems (e.g., a central cooling plant and decentralized heating and ventilating systems) can be utilized.

Main equipment (i.e. chillers and boilers) is accessible in different sizes, capacities, and, configurations to serve quite a lot of building applications. Working just a few items of major equipment (usually with back-up tools) offers central plants completely different advantages from decentralized systems (evaluate Chapter 5 of ASHRAE, Decentralized Cooling and Heating).

A number of kinds of equipment and fuel sources could also be mixed in a single plant. The heating and cooling energy could also be a mix of electrical energy, pure fuel, oil, coal, photo voltaic, geothermal, and so on. This power is transformed into chilled water, hot water, or steam that’s distributed by the power for air conditioning, heating, and processes. The working, upkeep, and first prices of all these choices needs to be mentioned with the proprietor earlier than remaining choice.

A central plant will be personalized with out sacrificing the standardization; flexibility; and efficiency required to help the first cooling and heating tools by cautious collection of ancillary tools, computerized management, and facility administration.
Plant design varies widely based mostly on building use, life-cycle prices, operating economies, and the necessity to preserve reliable building HVAC, course of, and electrical systems. These techniques can require extra in depth engineering, equipment, and financial analysis than decentralized methods areas do.

In giant buildings with inside areas that require cooling whereas perimeter require heating, one in every of a number of kinds of centralized heat-reclaim units can meet each these necessities effectively.
Chapter 8 describes these combinations, and Chapters 12, 13, and 14 give design details for central plants.

Central plants can accommodate each occupied/unoccupied and fixed, year-round operation. Upkeep will be carried out with conventional one-shift operating crews, however normally requires 24 hours protection.

Advantages of Central Equipment

Main cooling and heating will be supplied always, unbiased of the operation mode of equipment and systems outdoors the central plant.
Utilizing bigger however fewer items of equipment usually reduces the facility’s total operation and upkeep value. It additionally permits wider working ranges and extra versatile operating sequences.
A centralized location minimizes restrictions on servicing accessibility.
Energy-efficient design methods, energy restoration, and power administration will be less complicated and cheaper to implement.
A number of energy sources will be utilized to the central plant offering flexibility and leverage when buying gasoline.
Standardizing equipment will be helpful for redundancy and stocking substitute components. Nevertheless, strategically choosing different-sized tools for a central plant can present higher half load functionality and, effectivity.
Standby capabilities (for agency capability/redundancy) and back-up gasoline sources can simply be added to tools.
Equipment operation will be staged to match load profile and brought offline for upkeep.
District cooling and heating will be supplied.
A central plant and its distribution will be economically expanded to accommodate future development (e.g., including new buildings to the service group).
Load range can considerably scale back the entire equipment capability requirement.
Submetering secondary distribution can permit particular person billing of cooling and heating customers outdoors the central plant.
Main vibration and noise-producing equipment will be grouped away from occupied spaces, making acoustic and vibration controls less complicated. Acoustical therapy will be utilized in a single location as a substitute of many separate areas.
Points similar to cooling tower plume and plant emissions are centralized, permitting a extra economic solution.

Disadvantages of Central Equipment

Equipment will not be available, leading to lengthy lead time for production and supply.
Equipment could also be extra sophisticated than decentralized tools, and thus require a extra educated equipment operator.
A central location inside or adjoining to the constructing is required.
Further equipment room height could also be wanted.
Relying on the fuel supply, giant underground or floor storage tanks could also be required on site. If coal is used, house for storage bunker(s) will likely be wanted.
Entry could also be wanted for big deliveries of gasoline (oil or coal).
Heating plants require a chimney and presumably emission treatments.
A number of equipment manufacturers are required when combining major and ancillary tools.
System management logic could also be complicated.
First costs will be larger.
Special permitting could also be required.
Security necessities are increased.
A big pipe distribution system could also be obligatory (which can really be a bonus for some purposes).