What are HVAC systems?
An efficient HVAC system makes buildings safer and healthier. These systems may use fresh air from external surroundings to regulate temperature and humidity.
In light of its importance, this article aims to discuss the various aspects of HVAC systems:
- Need for HVAC Systems in Buildings
- Air Conditioning
- Types of HVAC Systems
- Components of HVAC Systems
- Energy-Efficient HVAC Systems
1. Need for HVAC Systems in Buildings
An HVAC system is a necessity, not a choice. Why is it a must-have requirement for all residential, commercial and industrial buildings? HVAC systems play a crucial role in the maintenance of indoor air quality.
In research by Environmental Protection Agency, poor air quality was the largest factor for environment-related sickness. An efficient HVAC system solves this problem. It circulates the air, regulates the temperature according to the weather and removes harmful particles or gases from the air.
These features greatly reduce the risk of allergies, lung-related problems, and seasonal flu.
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Most people are aware of the concept of heaters. Who doesn’t warm up their room during the winters with a convector heater?
Now, imagine a system that centrally heats an entire building. That is what the heating aspect of an HVAC system is about. A component like a boiler or a heat pump heats water or air in a furnace or a large mechanical room. The process of conduction or convection transfers heat to all the areas of the building.
Pipes transport heat created by water or steam to other areas. A circulator or a heat pump moves the hot water to distribution systems. Wall-mounted or floor-installed radiators transfer heat throughout the building. The transfer of heat using steam or water is known as Hydronics.
The heat from the air is transferred through ducts which are heat-resistant. In this system, the air needs to be filtered for dust and other particles.
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Generally, a commercial building that has a large number of people does not need a lot of heat production. The balance should be maintained for the building to feel pleasantly warm.
3. Ventilation in HVAC systems
The indoor air quality of a building has a direct correlation to the health of the people who reside or work in that building.
The process of ventilation ensures the exchange of air in any space. It replaces the stale air of the inside with the fresh air from outside.
Ventilating space includes temperature control and the replenishment of oxygen. It removes odors, smoke, carbon dioxide, moisture, dust, and bacteria from a building.
Ventilation is an intentional procedure. It is either natural or mechanical. Natural modes of ventilation are concerned with open windows and any such source of airflow. Mechanical ventilation, on the other hand, specifically directs fresh air via ducts and vents.
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4. Air Conditioning in HVAC systems
A standalone air conditioner is a part of most urban homes now. It provides cooling and humidity control for one room. In the same manner, a central air conditioning system cools a commercial building and regulates humidity inside it.
Office buildings with heavy-duty computer systems need cooling to prevent over-heating. Sealed windows help in keeping the air cool for longer periods of time.
Vents draw fresh air from the outside and route it to a mixed air chamber. From this chamber, the mixed air goes into a heat exchanger. The air cools down and makes its way into space it is meant to be cooling.
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5. Types of HVAC Systems
a) Split HVAC System
As the name suggests, a split HVAC system consists of two different units- an indoor unit and an outdoor unit. An air handler (indoor unit), a condenser (outdoor unit), a thermostat, an air filter, and ducts are the components of such a system.
Split HVAC systems are further classified into single-split and multi-split systems.
i. Single-Split HVAC Systems
It is a compact system that is suitable for small commercial spaces. The installation procedure is quite simple. This system is affordable.
Cafes, shops, and offices usually opt for this HVAC system.
ii. Multi-Split HVAC Systems
It is a more expansive system. Multiple indoor units are connected to one outdoor unit. The installation requires professional help.
This system finds use in larger spaces like clinics and restaurants.
b) VRV or VRF HVAC systems
VRV (Variable Refrigerant Volume) or VRF (Variable Refrigerant Flow) uses a refrigerant for heating and cooling. This system uses just one condenser for more than one evaporator. Thus, this system is perfect for medium and large commercial buildings.
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VRV systems are of two types:
i. Heat Pump Systems
They can provide either coolness or heat at one time.
ii. Heat Recovery Systems
They can provide coolness and heat at the same time.
c) CAV and VAV HVAC Systems
The CAV (Constant Air Volume) system is best for manufacturing factories where the temperature is stable for long periods of time. The compressor operates at full capacity in order to reach the ideal temperature.
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The VAV (Variable Air Volume) system is more energy-efficient than the CAV system. Buildings that require a range of heating and cooling use the VAV system. The speed of the compressor depends on the temperature needed.
6. Components of HVAC Systems
An HVAC system comprises several components. They work together to adjust the temperature and ensure fresh air in the building.
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The main components of a commercial HVAC system are:
a) Air Handler or Blower Units
These units usually comprise of:
Warm moist air, after cooling, produces water (condensate). The condensate runs down the evaporator coil into a pan. This pan drains the water through the pipes to dispose of it.
It’s a small pump that collects and pumps water to a drain. Condensate pumps come into the picture when a building can’t rely on gravity for disposal.
Condensate Overflow Pan
It is a safety device that prevents leaks and spills. It either has a separate drain or a float switch that can shut down the AC if the pan is full.
It circulates the air inside the building. Air is moved at different speeds when the heating and the cooling functions are simultaneous.
These consist of the shut-down switch as well as the fuse that protects an AC circuit from overheating.
b) Evaporator Coil (Cooling Coil)
High-pressure refrigerant liquid, released into the cooling coil by the thermal expansion valve changes state from a liquid to a gas, causing a drop in temperature of the refrigerant and thus cooling the evaporator coil so that when we move air across the coil the air will, in turn, be cooled.
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The return plenum is connected to the return duct system. It is a compartment that receives air and provides it to the blower fan.
It is connected to the supply duct system. It is a compartment that collects air.
The return plenum and supply plenum are like “junction boxes” to which return ducts or supply ducts respectively can be connected.
It is the means by which an attic-mounted air handler is supported or held in place. You may suspend it from the roof rafters or place it on supporting wood beams.
c) Thermal Expansion Valve
An air conditioner thermal expansion valve is a device located at the cooling coil and connected between the incoming refrigerant line and the refrigerant inlet to the cooling coil in the air handler.
The air conditioning system thermal expansion valve or “TEV” is a device that regulates the flow of refrigerant from the incoming high-pressure side (from the compressor/condenser) into the low-pressure side (in the cooling coil).
d) Ducts and Vents:
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They are located at the return duct air inlets, at one or more central return air inlets, or at the air handler unit itself. Air filters remove dust and debris from building air.
Access ports to duct interior
Commercial ducts and some residential duct systems may have cleaning access ports. Residential HVAC ducts may have plugs indicating that the ducts were cleaned in the past.
Ductless air conditioning systems
These are also called “Split A/C systems”. A ductless air conditioning system may employ one or more wall-mounted cooling units.
Return air ducts
Return air ducts and registers collect warm moist air from the occupied space and return it to the air handler unit. Some air conditioning installations do not provide return air registers and ducts in every room and use one or more “central air return inlets” instead.
Supply air ducts
Supply air ducts deliver cooled air to the occupied space. They have the dual function of spreading out and directing the airflow into a location and permitting the regulation of airflow by opening or closing the register.
Supply air balancing dampers
Manual and motorized zone dampers may be installed inside the supply ducts at varying locations to permit balancing the airflow among different duct sections and thus among different building areas.
They are used to turn the air conditioning on and off and to set the desired indoor temperature. One thermostat will be located in each different air conditioning zone and will control an individual air handler unit’s operation.
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7) Energy-efficient HVAC Systems
These systems give intelligent reports on identifying problem areas and provide recommendations for solving those problems.
They also integrate control systems to automate responses. Heating and cooling systems are automatically adjusted according to the temperature outside. Constant monitoring ensures that neither overcooling nor overheating takes place.
HVAC (Heating, Ventilation and Air Conditioning) Systems are instrumental in building design. Architectural design and HVAC installations go hand-in-hand. Therefore, make the HVAC installation plans at an early stage.
HVAC systems combine the processes of heating, cooling, and ventilation. Doing so enables the proper circulation of air inside the building. It also helps in modifying the building temperature according to the needs of the climate or season.
HVAC systems for commercial buildings come in various types like the Split AC System, the VRV or VRF system and, the CAV and VAV systems. Each HVAC system type fulfills specific requirements for different-sized buildings.
There are several components of an HVAC system. From air handlers to evaporator coils, and from thermostats to ducts, every component has an indispensable role to play.
Technological advancements have allowed HVAC systems to become “intelligent”. Software like EMS (Energy Management Systems) provides energy-efficiency.
This software identifies problem areas and then provides automated responses to solve those problems.
The bottom line is that great attention to detail must be paid while choosing HVAC systems that perfectly suit residential or commercial buildings. This system provides a safe and healthy indoor environment for any space.
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