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The Ins and Outs of Air Conditioning

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Have you ever truly sat down to research your air conditioner and see what exactly is in your unit or even what it exactly does? From the Thermostat to the smallest bits and bobs that are inside your actual air conditioning unit to the duct work that pushes the cold or warm air that you love into your home. It’s important to know and it could really help you in the long run to know what these are. Since It’s probably the most important appliance in your home, this way you’ll understand your unit a little better.


When you walk into your home, the first thing you think about is, whether it’s too cold or too hot inside your house. This means that you will most likely end up walking towards your thermostat. While most thermostats installed now are almost all digital, there are still others that are not digital. Your thermostat will make sure that your home is cool or warm, depending on what exactly you want.

Mercury and Wires in your Thermostat

There’s a type of thermostat that includes something called mercury switch, which is a glass vial with small amounts of real mercury. Mercury is a liquid metal, it can conduct electricity and it flows like water. Inside the glass vial there are 3 wires, one wire goes all across to the bottom, so that it always touches the mercury. The next wire finishes to the left side of this vial, so if the vial moves in that direction the mercury touches it, this makes it to touch both left and bottom side. The last wire touches the right side, when it slides to the right the mercury makes contact with the right wire and the bottom wire as well.

It’s also important to note that there are two different kinds of thermometers in this form of thermostat. The first is the cover that shows the temperature, while the other is on the top layer of the thermostat; this controls the systems of cooling and heating. This kind of thermometer is just a coiled bimetallic strip. Now you’re probably asking, but what is a bimetallic strip? Well it is a piece of metal which is created by laminating 2 different kinds of metal into one. These metals can expand or contract depending on if they are being cooled or heated. The coil has a center that is connected to the lever that adjusts the temperature and at the end of the coil is mounted to the mercury switch, this way the coil can decide which way the mercury switch will tip towards.These type of thermostats have 2 switches, which move small metal balls which make contact with the circuit card which is inside of the thermostat. While one of the switches controls the heat or cold modes, the other switch will control the fan for circulation. If you move the switch to the left, it makes the mercury shift and then it gives a current to energize a relay which makes the heater and the circulation fan starts inside your home. Then if you move the switch to the right, it does the same however it turns on the air conditioner. Thermostats also have a device that is called a heat anticipator. Basically this makes it so, if the heat in your house hasn’t reached the thermostat, but it’s heated well elsewhere in the home it will automatically turn off the heater. Inside there are also the resistor and the wiper, these basically bake it so that the current that controls the heater has to travel from the mercury switch to these. The resistor generates heat while this is happening and eventually it will shut off the heater once it’s reached the optimum heat you desire.

There are wired thermostats which are a type of thermostat that have been designed with 5 wires. Here are the wires:

Digital Thermostats

While having 2 transformers providing the power for the thermostat which is used to switch with the various relays. This means that this ends up leading to turning on the air conditioner, fan, and furnace.There are Digital Thermostats which end up using a simple device that is called a thermistor which measures the surrounding temperature. This allows electrical resistance to change with the temperature. Your digital thermostat can have a micro-controller which measures the resistance and can convert the number to give you what the actual temperature is. A digital thermostat has a larger number of things that it can do, that a regular thermostat just can’t do. One of the more popular features is the ability to program your thermostat. Which means you can make it turn on or off at certain hours for certain times, which is actually a great feature that can eventually save you money!

If it seems like there are just rooms in your house that you either can’t properly heat or properly cool, it’s probably time to consider a system zoning to be installed. This all basically means that you would install multiple thermostats that are linked to a control panel. This panel operates dampers in the ductwork of your air system. These thermostats will read the temperatures in their respective areas, which helps to decide what parts of the house need more air conditioning or where in the house there is less need for air conditioning. Some of these digital thermostats actually talk to the point where they recognize and respond to voice commands. Commands would be worded simply such as: Thermostat… Raise.. this would make the thermostat raise the levels from lets say 75 to 77 degrees Fahrenheit.

New Age Thermostats

If you’re someone who travels a lot, and you don’t want to be paying to cool or heat an empty home, there are some thermostats that may be important for you. Telephone Thermostats are basically a way where you can make a phone call to your home phone line which you can turn on or off as well as adjust the temperature of your air conditioning/heating unit. This is simply all done by connecting the thermostat to the home telephone line. However now that there are smart phones, we have what are called smart thermostats. These thermostats allow you to control your home’s thermostat from your touch-screen phone. There are even phone apps, that make it easy and convenient to keep using. 

One important thing about the thermostat is that you can’t just place it anywhere, which is why it’s important to know how and where it should be placed. First of all it should be located in a part of the home where you or your family spend most of your time. There should be a distance of at least 5 feet from the ground and 18 inches away from the wall outside. It’s also important that wherever it’s kept, it isn’t being exposed to any kind of heat sources, such as heater vents, sunlight, appliances, windows, or even hot-water pipes. One last thing is to not put thermostats near stairways or in a corner, because it can affect the air circulation. 

Air Conditioner/Heating Units

An important point to make when it has to do with air conditioning is that, the air conditioning manages refrigerant and moves air in two directions: indoors and outside. There are 4 parts of the air conditioner that are important to know about:

To put it simply the air conditioner is split 4 ways that feed into each other. The evaporator is actually in the cold side of the air conditioner and a fan blows air over the chilled coils and into the room. Whereas the hot side contains the compressor, the condenser, and finally another fan that is meant to vent warm air that’s coming off from the compressed refrigerant that leads to the outdoors. There’s an expansion valve that makes sure that there’s refrigerant moving towards the evaporator. Then this liquid receives a pressure drop, which then turns into gas. A compressor is a large electric pump which gives pressure to the refrigerant gas and this turns the gas into liquid. Inside the unit there are also things like sensors, timers, and valves. This is probably the most common set up for an air conditioner however there are some units that have variations.

Air Conditioning Options

The window air conditioners are much smaller and the hot air vents are on the back, there are also condenser coils as well as a fan that cools and re-circulates the indoor air. Then there are larger buildings like for example: hotels and hospitals. These will usually have them located somewhere on the roof. At a point where the house is larger and more spread out than most, this usually ends up needing a larger unit, which is when you end up needing a split-system unit. The way it works is that it splits the units to having the hot side outside of the home and the cold side inside of the home. Basically the colder side, is the expansion valve as well as the cold coil, it’s all placed inside some type of furnace or air handler. Then you have the unit that is sitting outside which is the hot side. This part consists of long spiral coils that are shaped like a cylinder. There’s also a BIG fan inside this coil that blows the air through the coil itself, there’s also a weather-resistant compressor, this helps the unit in case of rain or storms. It’s also important that if you live in an area where there are lots of hurricane and storms. One of the biggest points about the split-system is that it’s low-cost as well as it reduces the noise inside your house, even if it increases the noise outside of the home.

When a building gets too big it becomes harder to use the split-system, which causes it to become hard to spread the air conditioning across the whole building. This is where we get into systems that use water to cool the home. To start of there are Chilled water systems. This type of air conditioner is installed on the roof or behind the building, it also cools water to about 40 and 45 degrees Fahrenheit. This water travels through pipe work, which works like an evaporator coil. As long as the pipes are properly insulated, there’s no limitation to the chilled-water system. On most units the air gets used to dissipate heat from the compressor coils. However in larger systems they use a cooling tower instead. The tower will blow air to evaporate some of the water, which leads to cooling the water stream. The only drawback of this is that you’ll have to constantly add water to make up for the evaporation.

Different Options to Cool or Heat your Home

There’s also something called a Heat Pump, which is basically a system of mechanical-compression cycle and refrigeration system, which can be either reversed to give cool or heat in small spaces. An advantage of having this type of heating is energy efficient, because it doesn’t generate the heat but moves the heat along. Depending on your home and if humidity is an issue for you and your family you may want to add a humidifier to your unit. It has a humidity-sensing control which cycles with the humidifier which would go on and off. There’s a water panel that will have vapor circulating within the air when it is necessary. This can help with giving your skin moisture, assisting with making sure those things such as wood floors, furnishings, and keepsakes from drying out. 

A way to assist your unit outside to work more efficiently and work easier is if you surround it with plants. It will cast some shade on your air conditioner to help keep it efficient. You can plant some shrubs around it, however it’s important to plant things that won’t shed too many leaves around the winter time. Also you can create a lattice which looks nice with some climbing plants this would give lots of shade to the unit. Just make sure that you leave a way to the unit, so if you or a technician need to they can get to the unit.


Ducts are made of various materials. Starting out with Galvanized steel, which is the standard as well as most common material that they use in making ductwork. These are usually lined with fiberglass blankets or wrapped outside with fiberglass blankets. Then there are aluminum ducts that are quick to install but lightweight compared to others. Then there are Polyurethane and phenolic insulation panels, these are panels that come already insulated. Fiberglass duct board are also pre-insulated however they aren’t metallic ductworks, it also absorbs sound which makes the system quieter. There are also ducts that are flexible which are constructed out of flexible plastic which is laid over metal wire coil to shape the tube.

Parts of the Ductwork

When a duct system is being installed they put in a vibration isolator which basically makes it so that it doesn’t cause too much vibration, as well as too much noise. This way people who live in the home aren’t being distracted or bothered by the ductwork. There’s a part in the ductwork that’s called take-offs which usually have multiple small metal tabs which are then bent so they attach to the main duct. Sometimes the ductwork has to be able to vertically be placed to let the air travel in thin walls which are called stacks. Ducting systems usually give a method to adjust the volume and the air flow that travels through many parts of the system this is called volume control dampers.

There are two dampers that you can have placed in the ductwork that are smoke and fire dampers. The smoke damper is electronically operated, and basically as soon as it senses smoke the damper will close automatically until someone opens it manually. Then the fire damper which is not electrical, they are set vertically which means they are gravity operated, then horizontal fire dampers which are spring powered. A fire damper has an advantage over the smoke damper, because if there’s an electrical issue the smoke damper will stop working, but the fire damper won’t. When the temperature goes up to a certain level, the fire damper can end up melting the piece of metal or breaking, which holds open the damper, this will cause the ducts to be sealed properly.

Importance of Ductwork

There are turning vanes that are installed inside of the ductwork in the changes of direction, to help minimize the turbulence as well as the resistance to the air flow. Then there’s the plenums which are the central distribution and collection units for the HVAC system. There are ductless systems as well, that are easy and they allow flexibility where you can bring heat and cool to your home without actually using ductwork. It’s a great tool If you ever have to add a room to your home, and you don’t want to spend a large amount of money to put in some ductwork, it would just be easier and cheaper to just add a ductless system which can bring to the new room air conditioning and heating efficiently. 

It’s also important that you make sure your ductwork regardless of who installs it is professionally installed. There are consequences that may happen if you do not have a professional build your ductwork. It could create poor air quality, make your electric bill go higher. If it’s installed and designed in a poor manner it could make it so that the cooling or heating around the home is meager compared to proper work. It could possibly place you in a position where you have leaky ducts which can possibly lose you 20 to 40% of your air, which means that your unit has to work harder to cool your home which will eventually lead to your electric bill going up. If there are flexible ducts it’s important that they aren’t twisted, crushed, or even torn. These could cause restriction in the airflow. If your ductwork has issues or damages to it, there’s a chance that animals or insects can become pests inside your ductwork. Which not only does it make the air quality poor, but think about watching insects crawl out of a vent into your room, Gross right?  

The Cooling of HVAC Systems: Understanding Air Conditioning (

How Air Conditioners Work | HowStuffWorks

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