Heat Pump Compressor Not Turning On: Common Causes and Fixes

Figure 1: Heat pump outdoor units.

Heat pump compressors are integral components of heating and cooling systems, responsible for compressing and circulating refrigerant through the system. When the compressor fails to turn on, it can result in inefficient operation, poor heating or cooling performance, and even complete system failure.

In this article, we'll explore some of the common causes of a heat pump compressor not turning on and the steps you can take to troubleshoot and resolve the issue.

1. What is a Heat Pump Compressor?

Before diving into the potential causes of a heat pump compressor not turning on, it's important to understand what a heat pump compressor is and what it does.

A compressor for heat pump is responsible for compressing refrigerant as it circulates through the system. This compression is what allows the refrigerant to absorb heat from the indoor air and release it outside during the cooling cycle, or vice versa during the heating cycle.

Without a functioning compressor, a heat pump system cannot circulate refrigerant or operate efficiently.

Figure 2: Heat pump working principle diagram.

2. 6 Common Causes of a Heat Pump Compressor Not Turning on

There are several potential causes of a heat pump compressor not turning on. Some of the most common causes include:
● Electrical Issues
● Bad Capacitor
● Low Refrigerant Levels
● Compressor Overload
● Faulty Motor
● Defrost Cycle

2.1 Electrical Issues

One of the most common causes of a heat pump compressor not turning on is an electrical issue. This could be due to a blown fuse or tripped circuit breaker, a faulty thermostat, or a problem with the wiring or connections within the system.

2.2 Bad Capacitor

Another common cause of a heat pump compressor not turning on is a bad capacitor. The capacitor is responsible for providing the initial electrical boost that the compressor needs to start up. If the capacitor fails, the compressor may not have enough power to start up, or it may fail to start altogether.

2.3 Low Refrigerant Levels

Refrigerant is essential for the heat pump system to operate properly. If the refrigerant levels are too low, it can cause the compressor to overheat or fail to turn on altogether.

2.4 Compressor Overload

The compressor can become overloaded if it is forced to work too hard for an extended period. This can happen if the system is not properly maintained, or if there are other issues with the system that put extra strain on the compressor.

Figure 3: The inner structure of heat pump units.

2.5 Faulty Motor

The motor that powers the compressor for heat pump can also become faulty over time. This can be due to wear and tear or other issues within the system.

2.6 Defrost Cycle

Heat pumps go into defrost mode periodically to remove frost buildup on the outdoor unit's coils. During this time, the compressor may not operate for a period of time, which can cause it to appear as though the compressor is not turning on. However, this is a normal part of the heat pump's operation and is not a cause for concern.

3. Troubleshooting a Heat Pump Compressor Not Turning on

If your compressor for heat pump is not turning on, there are several steps you can take to troubleshoot the issue. Here are some of the most important steps to follow:

1.Check the Power Source
The first step is to check the power source for the heat pump system. Make sure that the circuit breaker is not tripped and that the fuse is not blown. Also, check the thermostat to ensure it is set to the correct temperature and that the batteries are not dead.

2.Inspect the Wiring and Connections
If the power source is not the issue, the next step is to inspect the wiring and connections within the system. Look for any loose or corroded connections and ensure that the wires are properly connected.

3.Test the Capacitor
The capacitor is an essential component of the heat pump system. Use a multimeter to test the capacitor and ensure that it is functioning properly. If the capacitor is faulty, it will need to be replaced.

4.Check the Refrigerant Levels
Low refrigerant levels can cause the compressor to overheat or fail to turn on. Use a refrigerant gauge to check the refrigerant levels and add more if necessary.

5.Clean or Replace the Air Filter
A dirty or clogged air filter can restrict airflow through the system, which can cause the compressor to work harder than it should. Clean or replace the air filter to ensure proper airflow and prevent unnecessary strain on the compressor.

6.Inspect the Motor
If the power supply and capacitor are not the issue, inspect the motor that powers the compressor. Look for any signs of wear and tear, and ensure that the motor is receiving the correct voltage and amperage.

Figure 4: Structural diagram of air source heat pump unit.

4. When to Call a Professional

If you have followed the troubleshooting steps listed above and the heat pump compressor is still not turning on, it may be time to call in a professional.

A trained HVAC technician can diagnose the issue and recommend the best course of action to resolve the problem. Attempting to repair or replace components of the heat pump system without proper training can be dangerous and may cause further damage to the system.

5. Conclusion

A heat pump compressor not turning on can be a frustrating and potentially costly issue. By understanding the common causes of this problem and following the troubleshooting steps outlined in this article, you can identify and resolve the issue quickly and efficiently.

Remember, if you are unsure about any aspect of troubleshooting your heat pump system, it is always best to seek the help of a trained professional.

6. FAQs

6.1 How Do You Reset a Heat Pump Compressor?

Resetting a heat pump compressor can be a simple process, but it's important to follow the correct steps to avoid damaging the system. Here's how to reset a heat pump compressor:

1.Turn off the power: The first step is to turn off the power to the heat pump system. This can be done by switching off the circuit breaker or by unplugging the system.

2.Wait a few minutes: After turning off the power, wait a few minutes to allow the system to fully shut down.

3.Turn the power back on: After waiting a few minutes, turn the power back on to the heat pump system. This can be done by switching on the circuit breaker or plugging the system back in.

4.Reset the compressor: To reset the compressor, locate the reset button on the outside unit of the heat pump system. Press and hold down the reset button for a few seconds, then release it. This will reset the compressor and allow it to restart.

5.Wait for the system to restart: After resetting the compressor, wait for the system to fully restart before turning on the heating or cooling function. This can take a few minutes, so be patient.

It's important to note that resetting a heat pump compressor should only be done if there is an issue with the system that has caused it to shut down or malfunction.

Figure 5: Copeland heat pump compressor.

6.2 Will a Heat Pump Work If the Compressor is Not Working?

No, a heat pump will not work if the compressor is not working.

6.3 How Do I Know If My Heat Pump Compressor is Bad?

There are several signs that may indicate that your heat pump compressor is bad and needs to be repaired or replaced.

● The heat pump is not working.
● The heat pump is making unusual noises.
● Reduced heating or cooling performance.
● The heat pump is tripping the circuit breaker.
● The heat pump is freezing up.

If you notice any of these signs, it's important to call in a professional HVAC technician to diagnose and repair the problem.

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