How Air Conditioning Works
Brought to you by Hingham Realtor Alice Pierce serving the South Shore of Boston
Basics of the Air Conditioning Process
Air conditioning is one of those things having to do with our homes, and our work spaces, that is easily forgotten about. The reason most of us think about air conditioning, or heating, is because the systems break. July and August here in Hingham, MA and on the South Shore of Boston have been a tad warm so reliance on cooling methods has increased. With this in mind, a basic primer on how air conditioning actually works is in order.
HVAC is an acronym for “heating, ventilating/ventilation, and air conditioning and is a sub-discipline of mechanical engineering. One of the invisible processes in air conditioning (and the reason the air is literally conditioned) is that the excess humidity is removed or diluted, if you will, and indoor air is replaced with outside air. The ventilation action is an exchange and a circulation of that exchange. Most individuals in the field of HVAC do this exclusively, and this is because of the complexities involved.
The goal of any HVAC system is to provide a climate of comfort by managing using indoor air quality and temperature. All HVAC systems, whether it is a heating or air conditioning process, use thermodynamics, fluid mechanics, and heat transfer while also preventing trapped air from stagnating. Moving and replacing air is the single most important factor in creating and maintaining healthy air.
Ventilation is common to both hot and cold air exchanges. Exchanging and replacing air within a building space ensures that while the temperature is controlled, the indoor air quality also meets numerous criteria. A high indoor air quality involves temperature consistency, oxygen replenishment, humidity control, odor removal, and the extraction of smoke, heat, dust, airborne bacteria, carbon dioxide, and other gases.
There are two categories of ventilation; mechanical or forced, and natural. Mechanical ventilation relies on an air handler to control indoor air quality and temperature. Natural ventilation is exchanging air within a building using no fans or mechanical systems. That would even exclude fans, as discussed in last week’s article about staying cool with out air conditioning. HVAC and air conditioning is only concerned with mechanical ventilation.
While it is easy to equate heating and cooling, excluding temperature differences, the two processes are quite different. When winter arrives, we will fire up our furnaces to stay warm inside of our homes. A furnace heats air or water with energy (requiring fuel like gas or oil, electricity, solar storage or friction) and distributes it to different parts of a building or a house.
An air conditioning system used to cool down hot air is more mechanically complex than a heating system. This is because air conditioning relies on the physics of evaporation rather than just heat production. Whenever something liquid evaporates into a gas or vapor, that process itself absorbs the heat.
You might notice that when we perspire we cool off. This is because when the water on our skin evaporates, by design, this process of evaporation takes some of our body heat with it. With an air conditioner the same type of evaporation happens but the process occurs within a closed, circular loop as a chemical is converted repeatedly. Within this continuing cycle, a class of refrigerants called R-140 refrigerants are converted from liquid to gas and back to liquid again and again.
The reason a chemical is used instead of water is that water must reach astronomically high temperatures before it converts to gas. Chemicals in the class of R-140 refrigerants require a much lower temperature before becoming gaseous.
The trademarked chemical Freon and many others in the category of R-22 refrigerants were once used in abundance and this is why we associate air conditioning with the word “Freon.” These R-22 type refrigerants relied on chlorofluorocarbons, or CFCS for heating and cooling until were found to contribute to the depletion of the ozone layer. They have since been phased out of use.
5 Types of Air Conditioning
Air conditioning is fast becoming a necessity much like heating already is. Central air conditioning gives relief from the blazing heat and high humidity of warmer climates or summer seasons throughout entire structures. The portable air conditioning unit is generally on wheels and can be moved around from window to window. And there is still the window air-conditioner.
Forced-air systems are the most typical in our homes. This air conditioning uses a central cooling unit and a system of ducts throughout the house to push cool air to each room. There are basically two settings in a forced air setup: on or off. The air handler operates at full blast, or is shut off completely when a desired temperature is reached.
Ductless Air Conditioning
Ductless air conditioning systems use outdoor compressor units to provide refrigerant, electricity and drainage into indoor components that are mounted on the walls in rooms to be cooled. This approach increases efficiency because no air is lost when moving through a ductless system.
Variable-speed air handler
This is actually an alternate means of moving cold air where the unit begins at high speed in the morning to establish a reasonably cool temperature. As the day goes on, the flow of air gradually slows down and operates continuously to maintain a set temperature. This is an energy saving system because it operates overall at slower speeds. In addition there is less wear and tear to your system without the repeated starting and stopping.
Air-source heat pumps
High-efficiency heat pumps do wonders for your electric bills. The pump is used for heating and cooling and condenses warm air before transferring it indoors. Acting very much like an air conditioner, the pump cools be removing heat from inside the home and condenses it before returning air inside. The air-source pump has a long lifespan and is a good investment. However. these units are better suited for climate zones where round-the-clock cooling is not needed. In Hingham, MA and along the Massachusetts coast, there are indeed times when round-the-clock cooling is helpful for comfort.
Geothermal heat pumps
The geothermal heat pump is one of the most energy-efficient methods of heating or cooling a home. It is a fascinating technology and relatively new in the United States. A series of liquid-filled pipes uses energy underground in the 50 to 60 degree range and, for cooling purposes, removes heat from the home and replaces it with the colder air. Because the temperature underground stays constant regardless of the weather, the system is extremely reliable. Geothermal systems last about twice as long as air-source units because of the lack of moving parts
The Efficiency of Your Air Conditioners
Air conditioning efficiency is rated using something called the “seasonal energy efficiency ratio,” or SEER. The ratio compares cool air delivered with energy used to get that cooler air. The higher your SEER rating, the more efficient a system is.
You have probably seen the “Energy Star” label on air conditioners. Usually more expensive, these units have a higher SEER rating than the same item without the Energy Star label.
To preserve efficiency with what you have, general maintenance can go a long way. While you can’t necessarily avoid a repair or replacement, you can make sure that you have cool air available to you when it is needed. Like right now!
1) Change your air filters.
Think of them like the oil in your car because they are that important. If your filters are dirty, then your system strains to work harder, and parts wear out much faster. Fresh filters will also contain debris in your air. During times of high usage, you should change your filters once a month, and otherwise once every three months.
2) Check for Obstacles
Check to see there are no obstacles to the functioning of outside components. Things like weeds, grass, branches, leaves and vines will wreak havoc on your air conditioning.
3) Hire a Professional HVAC
Have your HVAC person come once a year, in the spring, to test all the working parts of your air conditioning. He or she will measure temperature and air flow and adjust where needed. A reputable HVAC company can also check that no ducts are leaking, grills are placed properly, and that the settings controlling your air conditioning are correct and well balanced. It is also important to monitor the refrigerant level.
Take a look at the air conditioning coils as they can use occasional cleaning.
Maybe there are some worn or missing spots where the insulating material is around your ducts. If you re-insulate air conditioning ducts you can get cooler air for less money going towards your utility bills.
When you air conditioning is running, check for any hissing noises, or hold the palm of your hand close to areas of your ductwork. If there are any holes, seal any leaks in the duct system with caulking and weather stripping.
A Formula for Repair vs. Replace
Nothing lasts forever, and things like air conditioners often break before they stop working completely. The recommendation is to consider whether or not the unit is more than 6 years old. If it is, and the repair will cost more than 50% of a brand new system, buy something new. Energy Star recommends replacing an air conditioner that’s more than 10 years old, even if it’s still working. The system won’t have many more years left in it, and it’s likely to be using more energy than necessary.
Installation of Air Conditioning and Hiring an HVAC Professional
If you are considering a renovation or new installation of air conditioning, you truly do need an HVAC professional. Ask for references, and make sure that the person or company is licensed and insured before signing a contract. A solid professional will have multiple references and active clients. A good HVAC provider will educate you so that you can make an informed decision.
Once you decide on the brand, the work will begin. The HVAC company will calculate your home’s cooling load, and from this determine what size system you need. Ductwork will be installed using sealants and/or metal backed tape for an airtight route of delivery.
For the life of your air conditioner, you can then use the same HVAC company that performed the installation. This gives you an edge since they know your layout and equipment better than someone new.
Waterfront properties about on the South Shore of Boston and top Realtor Alice Pierce is your preferred agent for buying or selling your home. Contact her by visiting her Coldwell Banker website, sending an email or calling her cell phone at 781-724-7622. She can provide in-depth, first hand information about all South Shore communities including Hingham, MA, Cohasset, MA, Hull, MA, Norwell, MA and any other South Shore towns.