Keep the Heart Pumping: Proper HVAC Compressor Maintenance
To Keep the System Running, Overall System Health Must Be Maintained
The compressor is often compared to the heart in a human body — a vital organ that must keep pumping for the entire system to function. Just as the human body must be regularly checked to ensure the heart is working properly, so, too, must HVAC equipment. Or, in the words of Scott Pires, a service technician with Welsch Heating & Cooling, St. Louis: “Have it cared for.”
Another analogy commonly used to explain the importance of the compressor is to compare it to an engine in a car. To keep both the heart and engine running, overall system health must be maintained.
While commercial customers typically have a better understanding of the importance of regular maintenance, the same doesn’t hold true for residential customers.
“Explaining the importance of seasonal maintenance to a residential customer in terms they can understand is essential,” Pires said, noting this is why he uses the car comparison. “Generally, they always understand the analogy, and the importance of having it cared for is apparent.”
So, what needs to be cared for to ensure the long life and health of the compressor?
According to Cory Contreras, co-owner of Lex Air Conditioning and Heating, Carrollton, Texas, all aspects of the system must be considered to determine how the compressor is running.
“Keep in mind, the compressor is dependent on so many other components — both inside and outside the equipment,” he pointed out. “Duct, refrigerant piping, motors, metering devices, filters, and the refrigerant itself all contribute to the operation and overall health of the compressor.”
Pires added, “All the things you normally check will cue a tech into how the compressor is doing.”
Potential Red Flags
During a routine maintenance tuneup, there are many checks technicians may perform that can alert them of potential issues with the compressor.
“The most common red flags are abnormal pressure or temperature readings,” Contreras said. “These readings alert us to the presence of an abnormal condition in the system and, hopefully, prevent future compressor failure.”
More specifically, Contreras said, abnormal refrigerant pressure readings, abnormal superheat and/or subcooling, a high discharge temperature, and abnormal evaporator coil temperature drop are all indicators of an underlying condition that could lead to compressor failure.
“For example, a low superheat reading would indicate liquid refrigerant could be slugging or flooding back to the compressor,” he said. “A compressor is not designed to compress liquid. It is designed to compress gas. This slugging of liquid can cause internal compressor components to break. Liquid flooding can also wash away oil from compressor bearing surfaces, which leads to lack of lubrication and overheating. All of these conditions will ultimately result in compressor failure.”
According to Contreras, slugging can be caused by a number of things, including a dirty air filter, dirty evaporator coil, nonfunctioning blower motor, lack of return air duct, faulty metering device, or restricted drier.
“Any of these problems will usually manifest as abnormal pressure readings and abnormal superheat or subcooling,” he said.
Returning to the heart analogy, Fred Kobie, president of Kobie Kooling Inc., Fort Myers, Florida, compared pressure readings and amp draws to blood pressure readings.
Both can be compared to blood pressure, he said, “and how a doctor will use that information to help determine the health of the body, or in this case, the heart of the system — the compressor.”
Kobie continued: “Fluctuating pressures or amp draws, unexplained variance of the refrigerant pressures, and unexplained high pressures are all red flags to a mechanic.”
Benefits of Regular Maintenance
Compressors are expensive to replace, so it’s important to spot the red flags before a big failure occurs.
As Pires pointed out, “Residentially speaking, there isn’t much you can do to repair a compressor.”
The goal, of course, is to uncover any potential problems and address them during a regular maintenance check.
Contreras said he often has to explain to customers that preventive fixes uncovered during a system checkup are generally a much better solution than the wait-and-see approach.
“A compressor is more expensive to replace than a condenser motor with bad bearings or a faulty high-pressure switch,” he said.
Of course, none of these early warning indicators of problems can be detected if regular maintenance is not performed. That means contractors must continue to stress the importance of consistent maintenance to all customers.
“We try to educate them as much as possible and let them know the benefits of a properly maintained system. They will enjoy increased equipment lifespans, overall,” Contreras said. “They’ll also experience optimum comfort and IAQ in their homes, which is beneficial health-wise to the entire family. A properly maintained system will also help our customers save a little bit of money on electric bills.”
It also never hurts to remind customers of what they can do themselves to extend the lives of their systems.
“Keeping the evaporator coil and condenser coil clean are relatively easy things to do,” Contreras said. “Dirty coils are a surefire way to damage a compressor and negatively impact compressor efficiency.” As a result, Contreras tells customers to rinse their coils periodically with water and also reminds them to change filters regularly.
Publication date: 3/30/2015