A compressor is considered the heart of a heating and cooling unit. It circulates the refrigerants between the indoor and outdoor unit to either cool or heat the air.
Every homeowner should know some basics of AC and heat compressors to troubleshoot basic issues, communicate effectively with technicians, make informed decisions, and perform preventative maintenance.
This guide will cover what a compressor, the different types of HVAC compressors in AC and heat pumps, common issues, fixes, and maintenance tips for compressors is. Understanding the different types of air conditioning compressors is essential for selecting the right system.
What is a compressor in HVAC
An “HVAC compressor” is the compressor in the heat pump or air conditioning unit. At its core, a compressor is a device that pressurizes refrigerants.
This pressurization is key to the heat transfer process that makes cooling and heating possible.
The refrigerant is a chemical compound that transfers heat to or from the air in heat pump or air conditioners. It circulates throughout the system while doing its heat-transferring job. The compressor is linked to the refrigerant’s circulation.
An HVAC compressor has several key components to perform its task:
- Motor
- Piston or scrolls
- Valves
- Crankshaft
- Connecting rod
- Oil sump
The motor provides the power for the whole process. Pistons or scrolls compress the chamber that compresses refrigerant gas. Valves control the inward or outward flow of this gas.
The crankshaft converts the motor’s rotational movement into compressing and expanding linear motion. Connecting rods connect the crankshaft with the motor.
The whole process involves different kinds of movement. Lubricating oil allows this movement to run with less friction. Oil sumps hold these lubricating oils.
How Does a Heat Pump or Air Conditioning Compressor Work?
The compressor compresses the refrigerant when it is in gas form during the circulation process. This process is fundamental to how all air conditioning compressors function.
Refrigerants take heat from outside air during heating and inside air during cooling. The high-temperature refrigerant becomes a gas. The pressure remains low still.
At its gaseous state, the refrigerant enters the compressor. The compressor compresses the refrigerant gas to make it a hot and high-pressure gas.
5 Types of HVAC Compressors
1. Reciprocating Compressor
This is the most efficient HVAC compressor among all the types. Reciprocating compressors are known for their robust design. The reciprocating HVAC compressor design has been a workhorse in the industry for many years.
The reciprocating air conditioner compressor has a piston in it and can have up to eight cylinders. When the piston moves down, it creates a vacuum effect inside the compressor. As a result, it sucks in the refrigerant gas. When the piston goes up, it pushes the refrigerant out to the condenser.
2. Scroll Compressor
The scroll compressor is the latest technology of compressors and the most used one, especially in Trane units.
The scroll compressor has fewer moving parts. It has fixed coils called the scroll. During the compression, a scroll moves the refrigerant to the compressor’s center. Then it compresses the refrigerant gas.
3. Rotary Compressor
The rotary air conditioning compressor has a blade and shaft in it. The shaft rotates inside the compressor cylinder to push refrigerants inside. Then the refrigerant gas gets compressed.
The whole process doesn’t make much noise. So, this compressor is best for noise-free areas like office spaces.
4. Screw Compressor
The screw compressor is best for large-scale cooling. It has two helical motors that move from one place to another. To compress the refrigerant, it shrinks the space inside it. The screw air conditioning compressor is a robust option for industrial applications. Due to their design, they are well-suited for continuous operation and large cooling loads.
5. Centrifugal Air Conditioning Compressor
Centrifugal compressors are used in extra-large HVAC systems. For very large buildings, the centrifugal HVAC compressor is often the most suitable choice.
As the name suggests, the centrifugal compressor uses centrifugal forces to pull the refrigerant. Then it spins the refrigerant quickly to transform it into a compressed form.
Our infographic on the 5 HVAC compressor types.
Key Difference Between AC Compressors and Heat Compressors (as HVAC Compressors)
Both an air conditioner and heat pump use the same type of compressor. There is no fundamental difference. What set them apart are the systems and how refrigerant flows.
The misconception arises from two reasons:
- Different applications
- Reversing valve
The air conditioner solely focuses on cooling. In an air conditioner, the liquid refrigerant absorbs heat from inside (through the evaporator coil). Then pass into the compressor.
Meanwhile, a heat pump works in two different modes: heating and cooling. In cooling mode, it works the same way as the air conditioner. In heating mode, the refrigerant takes heat from outside air before going into the compressor.
Reversing Valve Issue
Reversing valve is responsible for the modes in heat pumps. It changes the direction of refrigerant flow.
Instead of an evaporator and condenser coil (like AC), a heat pump has indoor and outdoor coils. Both coils can work as evaporators and condensers. The reversing valve determines that.
So, the compressor and its functionality remain the same even though they are mentioned separately sometimes. It’s how the refrigerator is flowing into it from different directions.
Common Issues and Troubleshooting
A failing compressor can be a major headache. So, knowing the signs, common problems, and what to do is crucial.
Common Problems with HVAC Compressors
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Refrigerant Leaks
Some refrigerant leaks are inevitable due to age and wear and tear. Some are due to physical damage and defects.
The compressor has seals to prevent the leak.
However, these seals wear out over time causing a loss of refrigerants. When the refrigerant levels get low, the cooling system loses its ability to cool or heat effectively. The compressor has to run longer times to make up for it. The longer runs cause more wearing on compressors.
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Electrical Issues
HVAC compressors have coils in them or depend on electricity to compress the refrigerants.
Any kind of electrical issues can cause the compressor to malfunction. Most commonly, wiring problems and capacitor failure are involved. Any kind of loose connection or damaged wiring interrupts the electricity’s flow.
The disruption causes the compressor to receive any power to function.
The capacitor provides the starting boost for the compressor motor. A faulty compressor can cause the compressor to start altogether.
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Overheating
Overheating can be caused by clogged coils, insufficient refrigerant, and poor lubrication.
Dirty coils can’t dissipate the heat as effectively and cause overheat.
Low refrigerant can cause the compressor to overwork and overheat for the reasons mentioned. It can even cause the AC compressor function to fail.
Lubrication makes the part movements smoother. Insufficient lubrication causes excessive friction instead and hence the overheating.
Troubleshooting Tips
As a homeowner, you can take some basic steps if you detect any issues with the HVAC compressor:
- Check the thermostat’s mode and temperature settings
- Look for dirt in air filters and replace them if they are dirty so that it doesn’t strain the compressor
- Check for obstructions (leaves, branches, etc.) in the outdoor unit
- Make sure the circuit breaker hasn’t tripped and reset it if it has
- Pay attention to the unusual noises
Call a professional when you face the following issues:
- Basic troubleshooting didn’t work
- Handling refrigerants
- Electrical work
- Require specialized tools and expertise
- Complex repairs
- Warranty consideration
Maintenance Tips for HVAC Compressors
On average, an air conditioner or heat pump compressor costs 1000 USD, excluding the labor cost and other costs associated with it. Proper maintenance is crucial to avoid premature failure of your HVAC compressor.
Here are some steps you can take:
- Regularly clean or change air filters to avoid overworking and overheating.
- Check refrigerant levels on a regular basis.
- Maintain a clean, unobstructed outdoor unit. Keep at least 1-2 feet clearance around the unit.
- Keep the vents and registers open indoors. Clean ducts properly. The ductwork should also be leak-free. It will ensure proper airflow.
- Pay attention to unusual noises coming from the compressors. They are the early signs of compressor problems.
- Schedule regular HVAC maintenance. A qualified professional will always check the whole system thoroughly including the HVAC compressor and detect any problem.
- Consider a surge protector to avoid compressor damage from power surges.
- Consider using a “hard start kit” to start the compressor more easily. Seek professional advice on whether you need one.
When to Replace a Compressor
The compressor is an integral component of an air conditioning system or heat pump system. So, replacing it can take a toll on your budget. However, it is time for a compressor replacement when you face the following symptoms:
- Loud or unusual noises like grinding, rattling, clicking, or hissing
- Warm air blowing from AC vents
- Insufficient heating from heat pumps
- Short cycling
- Compressor unable to start
- Ice buildup on the outdoor unit
- Visible refrigerant leaks
It is always better to consult an HVAC service company first to determine if you need a minor fix or a total replacement. They can accurately diagnose whether a repair or a full HVAC compressor replacement is necessary.
If your system is too old (10-15 years), it would be more cost-effective to replace the entire unit because other parts would need replacing soon enough.
Conclusion
Compressors are key to your HVAC system. Choosing the right HVAC compressor for your needs is essential for efficient and reliable climate control. They circulate refrigerant to cool or heat your home. Knowing how compressors work, their types and common issues can help you take better care of your system and avoid costly repairs.
Simple maintenance, like cleaning filters and checking refrigerant levels, can keep your compressor in good shape. For weird noises or operational problems, calling a professional is the wiser choice.
With regular care, your compressor will last longer. Knowing the facts leads to better choices for your HVAC system.
FAQs about HVAC Compressor
1. What happens to the Temperature of the Refrigerant When It is Compressed?
In the beginning, the refrigerant enters the compressor in low pressure and cold condition.
But during compression, it turns into high pressure and high-temperature gas. After transforming from a liquid to a gas state, it absorbs the heat from the space and releases it to the environment, making your home cool.
2. What are the Signs of a Bad Air Conditioner Compressor Unit?
If you hear any noise coming from the AC or heat pump unit, there is a high probability that your compressor needs repair. Again, if you face a cooling problem, your compressor will require repair too.
3. What is the Cost to Replace a Compressor?
It’ll cost you around 1000 USD depending on the brand and the AC compressor type you choose. However, this doesn’t include the labor costs and installation costs. That’s why while buying a new AC, ask the salesperson about what is include and whatnot.
