“We are keenly aware that there is great value in having an educated consumer, which is why we have developed this page. It will hopefully help the customer to better understand the different parts of an HVAC system, why they go bad or are inefficient, and why they need to be replaced. We encourage you to be your own Best Advocate. Never be afraid to ask your technician to demonstrate for you why the part they say is bad, is bad.
Go armed with the following information!” -Greg Guthrie Vice-President
Condenser Fan Motor-These normally go bad in the hottest part of the year, and when you most need them. A motor has bearings in it (some that can be lubricated, most that can’t) that over time and under stress will fail. As the bearings lose their ability to move freely they begin to generate more and more heat. This can create issues with the motor windings and/or electrical components of the motor. A quick way to check if the motor bearings are operating properly is to disconnect power at the service disconnect, and using a screwdriver or butter knife, see if the condensers’ fan blades spin freely. If not it is time for a new condenser fan motor.
Capacitors- Like condenser motors these tend to go bad at the worst possible times. They have a mF tag on them that denotes what they are rated for. A technician will suggest that you replace this part (even if your system is not noticeably acting up) if he gets a reading from his meter that is 10% less than the rating on the capacitor. He is doing this to save you money, because he knows that the capacitor is on its way to failure, and he doesn’t want you to incur any additional fees in a guaranteed callback. There is also the fact that a capacitor which isn’t performing at its rated levels creates stress on the motor it is assisting, which can also cause a more expensive bill down the road when the motor goes bad.
Compressor Failure- No one wants to hear “You’ve got a bad compressor.” This always ends up in a bill that almost no one is prepared for. Compressors also tend to go out when we need them the most. As compressors heat up under stress (usually during the hottest part of the year) the copper windings that are responsible for making the motor spin, melt away a protective coating that separates one copper strand from another. This causes the copper windings to touch each other or other metals and the motor to “short out” or”ground out”. For most residential systems this means complete compressor or condenser replacement.
Low Refrigerant- Refrigerant doesn’t go bad, and in a sealed system, it will never run low. If a technician tells you that your system is low on refrigerant, this always means a leak somewhere in the system. This always means you will eventually be low on refrigerant again, and that you will always have to call them out again to refill your system unless the leak is repaired. A system can develop a leak from a copper line vibrating against another object, damage to the condenser coils from a lawnmower kicking debris at it, or as was the case with me, your kids dropping rocks into the condenser while the fan is rotating. However it happened, the leak should always be repaired.
Thermostat problems- some of these problems can be created by:
- A painter who removes the thermostat to paint behind it and loosens or breaks the connection to the thermostat
- A reset button that has to be pushed by the homeowner after the batteries have been replaced
- Design issues such as being located in the wrong place in a house, or too close to a supply register or heat source, causing short cycling.
- A Heat Limit Switch going bad can be caused by poor airflow across your heat exchanger due to a clogged air filter or closed/blocked vents in your home. Over time the limit switch gets worn out and will begin to stick.
- A proving switch getting debris lodged in its sensing tube
- A Hot Surface Igniter getting worn out prematurely due to furnace short cycling. They can also fail if something like drywall dust, insulation or other contaminants collect on them.
Furnaces – Transformer Burn out; A Furnace Board not working properly can be a short somewhere on the board, a faulty relay (in which case the entire board has to be replaced), or sometimes it can be as inexpensive as replacing the 3a or 5a fuse which is located on the board
The worst thing that can happen to your furnace is a crack somewhere in a furnace heat exchanger. This can’t be fixed and the heat exchanger must be replaced. In fact, upon diagnosis of a cracked heat exchanger the technician is required to disable the furnace on the spot. This is due to the real possibility of flue gases (carbon monoxide) getting into the air system and suffocating the building occupants.
This is also a good reason to have annual furnace maintenance performed. Carbon Monoxide poisoning is a real danger…
Indoor Blower Motors- Indoor blower motors, much like the condensing fan motors, periodically go bad, due to internal and external stresses. A properly maintained system (regular filter maintenance and annual inspections) will produce a longer lasting IBM. These will go bad due to time, loss of lubrication of the bearings, or an electrical issue (often caused by heat generated by the extra friction caused by poorly lubricated bearings).
Little to no Airflow- Possible causes include a plugged filter, a bad capacitor or Indoor Blower motor (if outdoor equipment is running, but indoor motor is not), low on refrigerant (evaporator iced up), loose duct attic connections
Unit Runs Constantly- This can be caused by a system low on refrigerant, or a loose return air connection allowing attic air to be pulled through the system.
Contractors and Relays- Contactors are a device used to turn on high voltage equipment using a low voltage circuit. They can go bad over time due to pitting on the points of the contactor caused by electrical arcing. These pits on the surface of the contactor can keep the points from making a solid path for electricity. Contactors can also become welded shut due to electric arcing between the points. This is often the case when you have a motor that never turns off. Relays serve much the same purpose as a contactor does. Relays work with smaller voltages than do most contactors. A bad relay will act much the same way as a bad contactor does (either sticking closed or open).
As you can see, there are many components and parts that make up an HVAC system. Our NATE certified and licensed technicians can handle them all. Give us a call at (702) 935-1955 and we will get one of our certified and licensed technicians out to your home or place of business and do a complete diagnostic.