Central HVAC ensures comfort and efficiency in diverse settings

Maintaining a comfortable and healthy indoor environment requires intelligent HVAC systems in large buildings and facilities. In this article, Satyam Majumdar, an HVAC Expert, provides insight into central HVAC plants’ components functions and energy efficiency, highlighting their effect on modern building management.

A central HVAC plant – a centralised system designed to provide heating, ventilation, and air conditioning to multiple zones or areas within a building or complex. Central plant systems carry components that deliver chilled water for cooling and use a boiler to heat water. These plants distribute conditioned air or water through an extensive network of ducts while piping circulates hot or chilled water.

Central HVAC Plants and components

The plant and its components provide efficient climate control across expansive spaces.

Chillers and Boilers: Chillers in central HVAC plants remove heat from the building by circulating chilled water or refrigerant. Air-cooled chillers use ambient air to dissipate heat in smaller or less critical applications. Water-cooled chillers use a cooling tower and water to dissipate heat, making them more efficient for larger applications. In a water-cooled chiller, the refrigerant condensing temperature depends on the temperature and volume of water entering the condenser.

Boilers provide heating by generating hot water or steam distributed through pipes to radiators, convectors, or air-handling units. Common types of boilers include gas-fired, oil-fired, and electric boilers.

Cooling Towers: A cooling tower provides cooling water to remove heat from a coolant (often water) used to cool machinery, process fluids, or buildings. When the cooling water meets with air, a small portion evaporates, lowering its temperature through evaporative cooling. Cooling towers are located near bodies of water like lakes and rivers to ensure a constant water supply for cooling. Heated water from an industrial process can enter a heat exchanger or condenser and flow through the pipework into the cooling tower for heat removal or flow directly through the tower. Spray nozzles inside the tower spray the water onto a fill material with a large surface area to maximise contact with air and increase the evaporation rate. Cooling fans within the tower aid the cooling process.

Air Handling Units and Pumps: AHUs draw in fresh air, filter it, heat or cool it, and distribute it throughout the building. The conditioned air is distributed throughout the building, ensuring good indoor air quality. They consist of fans, heating and cooling coils, filters, and dampers. The pumps circulate hot or chilled water. They ensure the efficient transfer of heat by moving water between boilers, chillers, cooling towers, and AHUs.

Central HVAC plants operate on thermodynamics, fluid mechanics, and heat transfer principles.

Advanced control systems monitor and regulate the operation of the central HVAC plant. They include sensors, thermostats, and building management systems (BMS) to optimise performance and energy efficiency. BMS monitors conditions and adjusts settings to maximise efficiency.  Investing in high-efficiency boilers, chillers, and AHUs with high SEER (Seasonal Energy Efficiency Ratio) and AFUE (Annual Fuel Utilisation Efficiency) ratings ensures optimal performance.

Energy efficiency

Energy efficiency is a critical aspect of central HVAC plants. The emerging technologies have led to high-efficiency systems that consume less energy and reduce greenhouse gas emissions.

Variable Frequency Drive (VFD) technology is fundamental to the efficiency of HVAC systems. Controlling the speed and torque of an HVAC system motor, AC Drives adjust these parameters to match the heating or cooling demand exactly. This intelligent regulation leads to significant energy savings and increased comfort for occupants. VFDs also contribute to the longevity of the HVAC equipment, reducing wear and tear, thus minimising the need for maintenance and repairs.

Heat recovery systems capture waste heat from exhaust air or water and reuse it for heating purposes, reducing energy consumption. A Heat Recovery Ventilation (HRV) system is a form of mechanical ventilation that improves indoor air quality and household energy efficiency. The principle involves the extraction of room-temperature stale air and the introduction of fresh, filtered outdoor air.

Central HVAC plants in large spaces

Central HVAC plants provide heating, ventilation, and air conditioning for large buildings. They warrant comfortable indoor environments by regulating temperature and air quality, contributing to energy efficiency and occupant well-being in residential, commercial, and industrial settings. For instance, an international airport employs a central HVAC plant to manage the climate control needs of its vast terminal buildings.

Office and Shopping Mall: In a high-rise office building, a central HVAC plant in the basement or roof provides heating and cooling to all floors. Air handling units (AHUs) on each floor distribute conditioned air through a network of ducts, ensuring even temperature distribution and fresh air supply.

A large shopping mall uses a central HVAC plant with chillers, boilers, and AHUs to cool and heat the facility. Cooling towers on the roof help dissipate heat from the chillers, while air ducts distribute conditioned air to various sections of the mall, keeping it cool in summer and warm in winter.

Hospitals and Hotels: In hospitals, a central HVAC plant provides precise temperature and humidity control for patient care and the operation of medical equipment. The system includes HEPA filters in AHUs to remove airborne contaminants and to create sterile and clean environments.

The hotel uses a central HVAC plant to deliver consistent climate control throughout the property. Each guest room has its thermostat to allow individual temperature adjustments, while the central plant ensures efficient and uniform heating and cooling across the entire hotel.

Data centres: A large data centre uses a central HVAC plant with precision cooling systems to manage the high heat load. Chilled water circulates through computer room air conditioning (CRAC) units, which keep the server rooms at optimal temperatures.

In conclusion

Central HVAC plants provide comfort and air quality in large and complex buildings. Understanding how these systems work can help building managers make informed decisions about their HVAC needs. As technology advances, central HVAC plants become more efficient, environmentally friendly, and adaptable to diverse needs, making them a foundation of contemporary building design and management.

Expertise shared by-

Satyam Mazumdar, HVAC Expert.