How Does A HVAC System Work – A Guide To Air Conditioning System

How Does A HVAC System Work – A Guide To Air Conditioning System

HVAC may be a mystery to the average business or homeowner. HVAC is the acronym for Heating, Ventilation and Air Conditioning.

HVAC is usually a combined system that provides heating, ventilation and cooling in a home or building.


Important Parts of an HVAC System

To dispel the mystery of what a HVAC system is, it is important to know the key parts of the system. For example, the portion of the system that provides heat includes:

. A motorized fan or blower

. Electrical wiring

. Condenser coil or compressor

. Heat exchanger

. Thermostat

. Evaporator coil

Cooling system parts include refrigerant, expansion valve, compressor, thermostat, condenser and evaporator coils.


Ducting and Piping

As AAA AC described, heating units and central air conditioning units also require a ducting system and piping. A stand-alone air conditioning unit requires installation through a window, or it may be a portable unit.

Note that piping is usually steel, copper or brass. In the case of natural gas heating, the piping is referred to as black steel.


How Ventilation Works

The ventilation part of HVAC refers to the output of the heating or cooling functions through intakes that pull air into the system and output sometimes called return vents or return registers that push heated or cooled air outward and circulate throughout a room or entire structure.

In recent years, HVAC systems pull in fresh air from the outdoors and circulate it indoors for greater air quality.


How Does an HVAC System Work?

The first step to the operation of an HVAC system is the thermostat. A thermostat is set to a specific temperature for optimal indoor heating or cooling comfort. The thermostat sends a signal through electrical wiring either to the furnace or air conditioning unit.

The specified type of fuel for heating is carried via piping to a connector. At this point, the motorized fan or blower activates the operation of the heating unit by pulling in the fresh air and pushing out or forcing heated air through vents and ducts.


How a Cooling System Works

Electricity powers both a stand-alone air conditioner and a central air conditioning unit. Similar to the design of a heating unit, refrigerant in a central air system relies on the fan and ductwork used by the heating system.

However, the difference is that piping lines for a central air unit are separate from those of the heating unit. This allows the refrigerant to flow through a closed system of piping.

Refrigerant is pumped from a condenser coil to the evaporator coil that absorbs heated air and cools it. The cooled air is then pushed through existing duct work or stand-alone air conditioner unit and, in concert with the fan or blower, circulates the cooled air throughout a room or building.

Understanding How the Thermostat Works for Heating and Cooling

The central air conditioning unit receives a signal from the thermostat when the thermostat is set to a specific temperature.

With a heating unit, the thermostat is set to a higher temperature for optimal heating comfort, whereas the thermostat for cooler air is set to a lower temperature.

Today’s thermostats are programmable for convenience. Temperatures may be programmed lower for heating or raised for cooling on a thermostat when a building or room is unoccupied.

An added feature of this programming is that thermostats can be programmed by remote with the use of a mobile device.

A heating system may operate with natural gas (one of the many compressed natural gas applications), oil, hot water or electricity. These variables tend to change the operation of the heating unit according to the manufacturer’s specifications.


HVAC System Maintenance

All mechanical parts should always be properly maintained. An HVAC professional should inspect the HVAC system at least once or twice a year, depending on the age of the unit and volume of use.

With regular, diligent maintenance by an HVAC professional unnecessary, costly repairs are avoided, and the unit will maintain the manufacturer’s efficiency ratings longer. The major benefit of proper maintenance is higher indoor air quality and better health.


HVAC Owner Maintenance

HVAC owners should be aware that heating and cooling units are equipped with filters. These should be replaced regularly depending on the type of HVAC filter recommended by the manufacturer and in the proper size for the size of the HVAC unit.


There are several types of HVAC filters. These include:

. Fibreglass

. UV


. Washable

. Pleated

. Electrostatic

HVAC filters capture airborne bacteria, odors and other types of particulate that keep indoor air quality healthy for occupants.

The operations and maintenance manual that accompanied the installation instruction and parts manual indicates the required size of the filter for the specific type of unit.

Each type of filter has a MERV (Minimum Efficiency Reporting Value) rating, which will indicate the size of the particulate capture that is most efficient.


HVAC System Design Data

The way an HVAC system works is largely dependent on system design. For example, some HVAC systems are designed for single zones dependent on a single thermostat. Other HVAC systems are designed for multiple zones that require multiple thermostats to provide adequate room temperatures.

Note that coils and fans should operate at peak efficiencies. These are further defined by flow rates as well as inlet and outlet temperature differentials.

Mechanical engineers who design HVAC systems are highly knowledgeable in variable parts that comprise these systems and also in system loads for input and output ranges for the overall sizes of units.

Thus, an industrial HVAC system is designed for greater input and output ranges than a residential system.


How to Choose an HVAC System


The choice of which HVAC system is best should be discussed with a HVAC professional. The sizes of HVAC Systems are determined by the square footage of a room or building. For residential and small buildings these sizes include:

1.5 tons for 600 to 1100 square feet

2-tons for 901 to 1400 square feet

2.5-tons for 1201 to 1650 square feet

3 tons for 1501 to 2100 square feet

3.5 tons for 1801-2300 square feet

4 tons for 2101 to 2700 square feet

5 tons – 2401 to 3300 square feet

In gas heating, Btu refers to the amount of energy needed to heat specific square footage. To further define Btu (British Thermal Unit), “one BTU is equal to the amount of energy used to raise the temperature of one pound of water one degree Fahrenheit.”


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