Why Is My Heat Pump Making a Loud Noise in Cold Weather?

If you’ve ever noticed strange sounds coming from your heat pump during colder months, you’re not alone. While heat pumps are generally known for being efficient and quiet, they can become noisy when the weather turns cold. While these noises can be concerning, they’re often completely normal. HVAC.com explores why your heat pump might make noise in cold weather and how to address the issue.

Why Do Heat Pumps Make Noise?

Heat pumps are designed to provide both heating and cooling by transferring heat from the outside air into your home. In colder weather, however, they work harder to extract heat from the air, which can lead to certain noises. While some noise is a natural part of the operation, persistent or loud sounds can indicate that something is wrong.

Why Is My Heat Pump Noisy in Cold Weather?

Defrost Cycle

One of the primary reasons for noise in cold weather is the heat pump’s defrost cycle. When the outside coil gets too cold and frost begins to build up, the heat pump will switch to cooling mode with the fan off temporarily  to melt the ice, pulling thermal energy from inside the home to warm the condenser coil. During this process, you may hear a loud “swooshing” sound as the system works to remove the frost. This is typically a temporary noise that lasts for a few minutes and is perfectly normal.

Increased Workload in Cold Weather

Heat pumps can become noisier in cold weather because they have to work harder to extract heat from the colder outside air. As the temperature drops, the system runs longer, and components – including the compressor and defrost cycle – may make more noise than usual. While this is typically normal, any unusual or persistent noise may need attention.

Ice Build-Up

If your heat pump is freezing up, the ice buildup can cause it to run inefficiently and create unusual noises, such as scraping, grinding, or even vibrations. These sounds are typically caused by fan blades hitting ice, or loose parts and wires creating rattling. Ice buildup can be a sign that the system needs maintenance or a defrost cycle that’s not functioning properly.

Start-Up Noises

When a heat pump starts up, it may make brief noises, such as clicking or thumping, as the system engages. These sounds are normal and can happen more frequently in cold weather when the system is operating more frequently to keep your home warm.

How to Handle Noisy Heat Pumps

If your heat pump is making noise during cold weather, there are a few things you can do to address the issue:

• Check for Obstructions: Sometimes, leaves, twigs, or dirt can get stuck in the outdoor unit, leading to unwanted noise. Turn off your system and inspect the outdoor unit to ensure nothing is blocking it. A quick cleanup can eliminate some of the noise.
• Ensure Proper Defrosting: If you hear a hissing, whooshing, or buzzing sound, it may just be the defrost cycle doing its job. However, if the noise persists or sounds like it’s not functioning properly, your system may need a checkup. A technician can ensure the defrost cycle is working efficiently and address any underlying issues, such as a refrigerant leak.
• Clear Ice and Snow: Ice and snow buildup around your heat pump can obstruct airflow, leading to scraping, grinding, or rattling sounds as the fan blades or other components struggle to operate properly.
• Routine Maintenance: To keep your heat pump in top working condition, regular maintenance is essential. Having a professional HVAC technician inspect the system before the cold weather hits can help prevent problems and identify any worn-out parts. This maintenance ensures your heat pump operates smoothly and quietly.

When to Call a Professional for Heat Pump Noises

If you’ve tried the basic troubleshooting steps and your heat pump is still making concerning noises, it’s time to call a professional. A technician can identify if there’s a deeper issue, such as faulty or worn-out parts, refrigerant leaks, or frozen coils. Refrigerant leaks, in particular, may cause a hissing sound, which indicates that the system is low on refrigerant and unable to operate efficiently.

A professional HVAC technician can perform an in-depth inspection and repair or replace any necessary components to get your heat pump back to quiet operation.