HVAC 101 - #1

How does my air conditioner work?

That is a good question. I think it is important every homeowner to understand how their system works. When the system is not working correctly you will have a better understanding of the diagnosis that your local service technician will give you when he is called. If you have an idea what he is talking about, you will have more confidence in him and his company that they know what they are doing. I do not know how many times I have heard stories about homeowners accusing technicians of trying to rip them off, only to find out that they were correct when a second company comes out and makes the same diagnosis. A majority of this can be avoided by understanding more about your system.

The basic refrigeration cycle:



Starting with the COMPRESSOR:
-The refrigerant (freon, R-22, etc.) enters the compressor as a low-pressure/low-temperature vapor. This is important since compressors are not very efficient at compressing liquids.
-The refrigerant is compressed causing the pressure and temperature of the refrigerant to raise significantly leaving the compressor as a high-pressure/high-temperature vapor.
-The compressor acts like a pump and moves the refrigerant through the system.

After leaving the compressor, the refrigerant enters the CONDENSER:
-The condenser is the set of coils outside that you can see with the fan usually blowing out of the top.
-The refrigerant enters the condenser as a high-pressure/high-temperature vapor.
-Once in the condensing coils, with the help of airflow from the fan, the refrigerant gives up some of its heat to the outside air causing the refrigerant to condense from a vapor to a liquid.
-The refrigerant is now a high-pressure/high-temperature liquid.

Whether you have a package unit or a split system, the refrigerant travels towards the TXV (Thermal Expansion Valve):
-Some systems might use either a small capilary tube or another metering device such as an orifice. Whatever the device, the process is still the same.
-The TXV or other metering device rapidly reduces the pressure of the refrigerant and by doing so, rapidly lowers its temperature as well.
-The refrigerant is now a low-pressure/low-temperature liquid.

After the metering device, the refrigerant enters the EVAPORATOR:
-Here the refrigerant absorbs heat from the air inside your house. (Heat always transfers from a high temperature substance to a low temperature substance).
-As the refrigerant temperature rises from the relatively hot air inside your house (moving by way of the fan), the refrigerant evaporates from a liquid back to a vapor.
-The refrigerant is again a low-pressure/low-temperature vapor and is ready to start the cycle over again as it travels back to the compressor.

This is the process in all vapor-compression refrigeration cycles, whether it is your freezer, refrigerator, or your air conditioner. If you still have any questions about the process feel free to send me an email and I will be glad to go into more details.

Homeowner Tip #1

What is the most important thing about my system that I need to understand?

Sufficient air flow! It is absolutely critical that the air flow through your return and supply ducts is unrestricted. Dirty air filters, clogged evaporator and condenser coils, fallen insulation, crushed duct lines, or an undersized duct system will not only adversely affect the temperature in your home, but I will also cause your system to work harder and wear out sooner. As a result, not only will you see an increase in your monthly utility bills, but a call to your local service company is not far behind.

Solutions:
-Make sure you regularly check your filter(s), at least every 30 days. Replace them when needed.

-You can clean the condensing coils outside by hosing them off with water. Not too hard of a spray stream though or you will damage the fins. Be careful mowing the lawn and try to keep from slinging cut grass and dirt onto the outside coil.

-If you are inclined, you can wash your evaporator coil inside by using a solution of dish detergent and water. Use a brush and go in the direction of the fins as to not cause damage to them.

-Be careful crawling around in your crawl space or attic. You do not want to crush any of the ducts.

-You can always call your local service company. They will most likely sell service agreements to come check your system out at least twice a year and clean the coils for you as well as performing other preventative maintenance items. Most of the companies will have other added benefits for loyal service agreement customers. Shop around and find out who is offering the best deal by comparing benefits and the services they offer. Ask friends and neighbors who they use. Having a service agreement is a wise investment to protect your HVAC system.