The heating system in HVAC can be classified into two major types, the direct heating where we have heating systems such as firewood, open furnace, etc. and the indirect heating system. The indirect heating system is commonly called the central heating system, where the source of heat is not close to the place where heat is needed. The central heating is the process of providing heat through a mechanized system. In central heating, the conversion of energy to heat is done from a source outside of or apart from the site where the heat is needed. Sometimes, the source could be located within the site(s) where the heat is needed. The produced heat is transported in form of a vehicular movement through a fluid medium. The central heating system can either provide the whole interior of the building with enough warmth or designed to meet the needs of a portion of the building. From one space to multiple spaces. When we combine the central heating system with other thermal regulating system to control the ambient environment of the building, the whole system would therefore be regarded to as an HVAC system i.e. (Heating, Ventilation, and Air Conditioning.)

How the Central Heating System Works

Compared to space heating, central heating system generates heat from one place such as a basement in a house or a furnace room or a mechanical room in a large building (the fact that it is called “central heating” does not necessarily make it to be located at geometrically central point). The heat produced from the system is distributed all around the building. This heat distribution is done by the forced air mechanism through ductwork, by water that circulates the pipes, or by steam that is fed through pipes. The combustion of fossil fuel in a furnace or a boiler commonly serve as the method through which heat is generated.

The Evolution of the Central Heating System

The invention of the central heating system used in today’s modern world can be traced to ancient Greeks. They originally developed central heating system. The temple of Ephesus was heated using flues planted in the ground, circulating the heat that was generated by fire. The Roman Empire also made use of central heating systems. They conducted air through a system known as hypocaust. The air was heated by furnaces through empty spaces dug under the floor and pipes installed inside the walls. The roman hypocaust was used on a smaller scale until a point in history when Muslim builders began using a simpler system that made use of underfloor pipes as a form of central heating to generate heat. A simpler central heating system whose mechanism operates in a way that allows for heat to travel through underfloor channels from the furnace room replaced the hypocaust system of the Romans in the medieval period.

Today, modern heating system has been developed from the three main methods of central heating. These three main methods include the hot air, steam and hot water central heating methods.

The Science behind HVAC

HVAC systems help us to stay warm in the cold and stay cool in the heat. They are ubiquitous in modern society and we may well wonder what we’d have done as a race without them. Tropical areas wouldn’t be able to survive the sweltering heat and the attack of mosquitoes without cooling systems. The people in extremely cold and icy areas of the world would be unable to survive without heating systems and most would die from hypothermia. Here’s an important question though? These systems that have done so much for us, how do they work? How is heat generated and distributed within a living space? How do air conditioners cool the air within our living spaces?
Science holds all most of the answers here. We will discuss a few basic scientific principles under the various units of HVAC that make the system work.
Heating- We all have a good idea about how heat gets generated. Fuels are burnt, energy is transferred. But how exactly does this energy get circulated around a room or living space? Heat transfer is achieved basically through three processes: Conduction, convection, and radiation.
Conduction: This is the transfer of heat by the vibration and collision of molecules through a solid body. Conduction is how the body of a metal pot feels hot when you’re cooking with it. The heat from the burner got transferred to the pot. Conduction depends on various factors such as the type of metal or material (heat capacity), size (heat transfer area) and others.
Convection: Convection is basically the transfer of heat through the movement of fluids. Fluids here refer to either liquid or gaseous materials. Convection occurs mainly by the bulk motion of the fluid. In simpler terms, imagine a kettle of boiling water gets spilt on the flow, as the water flows towards a nearby object (say your feet) It carries the heat along with it and makes you feel burned. That’s basically how convection works. Moving the heat through fluid.
Radiation: Radiation is the form of heat transfer that does not require a material medium through which the heat is transported. Rather, electromagnetic waves are the media through which radiant heat is transported. Radiation is how the heat from the sun gets to us on earth.
All of these phenomena have mathematical formulae to calculate the amount of heat transferred, but we do not want to scare away our non-science inclined readers

Ventilation- Like we described earlier, ventilation involves exchange of air, and it makes use of the principle fo diffusion. Diffusion involves the movement of molecules in air from a region of higher concentration to a region of lower concentration.

Air Conditioning
Refrigeration- Refrigeration works by taking a liquid (known as a refrigerant) through series of expansion and compression in an heat exchanger. The intermittent process allows for the removal of heat from the air inside the room and recirculating it out into the external air. This is why the air at the back of an air conditioner feels warm to the touch. More Info

How to choose the right contractor for HVAC Installation

Keeping your HVAC system up and running not only needs dedication but the right professional service. Your air heating and cooling system requires a high level of expertise and the care your system gets can affect the health of your family for better or worse. There are many companies that offer HVAC professional services but unfortunately, not all are created equal. Whether you need a repair or replacement for your HVAC system, choosing the right contractor for the job is a very important aspect of the process. A reputable HVAC contractor will ensure quality work on your system for efficient functionality. Here are helpful tips when choosing an HVAC contractor.

Research and referrals

You should start by doing your homework first. Check out the local HVAC companies on review sites like Facebook and Google just to mention a few. You can also ask your friends, neighbors and family members for advice and referrals. Word of mouth is often the best way to get a reputable contractor. Ensure the contractor you get in touch with has a good reputation for excellent customer service and quality workmanship.

Check for licensing and insurance

Look for an HVAC certified professional service whose technicians are licensed, insured and bonded. A certified professional service is an assurance that you’re working with a company that quality service. A proper insurance of the HVAC contractor is very important because it protects you from liability in case of injuries or accidental damages during the work. Don’t fear to ask the prospective contractor for the license number and criminal background check information.

Look for experience

Don’t forget to ask the experience of your prospective contractor. The contract should have experience working with the brand of system you have in your home. Ensure you get to know the exact HVAC systems the contractor specialize in before you can make a decision if they right for the job. Although longevity alone may not guarantee quality work, stability in business for long shows that the contractor is competent.

Ask for references

Ask the contractor for a list of references with their contact information. Previous clients are a good place to start when gathering information about the HVAC contractor. Call the clients and ask if the job was completed within the budget and on time. Get to know about the quality of service the clients received before you can decide to hire the contractor.

Home evaluation

If you need an air conditioning installation, your potential contractor should do a comprehensive home evaluation ascertain the heating and cooling solution that will work best for your home. An experienced contractor will inspect the duct system and insulation for any problems before installation process. A contractor who gives you an estimate without home evaluation could be a red flag signal.

Get written estimates and compare

A reputable HVAC contractor will have no problem providing a written estimate for you before the work starts. Get estimates from three to five contractors to choose the one with the best services. Don’t choose the lowest estimate especially if the company is not well rated online.  More info