Why Is My Heat Pump Blowing Hot Air in Cool Mode?

woman suffering from heat at home depicting heat pump blowing hot air in cool mode

HVAC systems are an absolute must in a home. For example, heat pumps offer great versatility, providing year-round comfort by allowing you to heat or cool your home as desired. If you feel too cold during the winter, a heat pump can warm up your house, while in the summer, the same unit can cool things down. It’s simple to change temperature settings and switch modes. However, some owners may encounter an issue, such as their heat pump blowing hot air in cool mode. Today, we will explore the reasons behind this phenomenon.

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Why Is My Heat Pump Blowing Hot Air in Cool Mode?

Even though heat pumps are known for their durability, they can still experience malfunctions like other machinery. One of the most common issues is a heat pump blowing warm air during the cooling cycle. Homeowners should become familiar with the typical causes of this problem. By understanding the root of the issue, they can minimize the chance of it happening again and attempt basic troubleshooting before seeking professional assistance. Here are seven factors to investigate when encountering this problem.

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Related Article: Identifying Poor Indoor Air Quality In Your Home

A Broken Heat Pump Reversing Valve

heat pump refrigeration cycle

The heat pump’s ability to operate in both heating and cooling modes is attributed to its reversing valve. This valve controls the direction of refrigerant flow. It determines whether the unit will extract heat from indoors and release it outdoors or gather heat from outdoors and transfer it indoors. A malfunctioning reversing valve can impede the heat pump’s performance. To resolve this issue, a skilled HVAC technician must replace the valve and recharge the refrigerant, which is a complicated task.

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Heat Pump Thermostat Problem


If your heat pump is blowing warm air around the house, it may be due to incorrect thermostat programming. Ensure that the unit is set to cool mode instead of fan-only mode. If the settings are incorrect, adjust them as required, as someone may have accidentally changed them. Also, check the battery level of the thermostat, as low batteries can cause malfunctions. Tripped breakers may also be the culprit, so examine them.

If the issue persists, you might be dealing with a faulty thermostat. In this case, replacing it with a new one is the only option. Consider upgrading to a programmable thermostat if you have an old manual one, as it could be due for replacement. Basic models are affordable, while more advanced models with additional features may cost a little more.

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Heat Pump Refrigerant Loss

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Heat pumps differ from furnaces in that they do not produce heat internally. Instead, they rely on a refrigerant to absorb heat from one area and release it in another. The heat pump will not function correctly if the refrigerant is not flowing sufficiently throughout the system. Even if the thermostat settings are accurate and the reversing valve is working properly, the unit may still dispense warm air in cooling mode. This situation is often the result of refrigerant leakage. Contact a licensed technician promptly to repair the leak and replenish the refrigerant.

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Clogged Air Filter on Heat Pump

The air filter’s primary responsibility is to trap dirt and dust, which accumulates on its surface as air flows freely. However, the layer of debris may become so thick that it obstructs the airflow, resulting in difficulty for the heat pump to function properly. To resolve this issue, one can clean the air filter to remove the blockage or replace it with a new one for a fresh start. Refer to the manufacturer’s manual for the suggested filter cleaning and replacement frequency, as environmental conditions around your home may necessitate more frequent replacements.

Related Article: Understanding MERV Ratings: Choosing The Right Air Filter For Your HVAC System

Heat Pump Duct Leak

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Air ducts can degrade over time. If your ducts are old, they may have developed air leaks, which can impede the distribution of conditioned air throughout your home. This can result in uneven temperatures, with some rooms feeling colder or warmer than others. Locating the source of the leaks can be challenging. Seek assistance from HVAC professionals to address this issue. By fixing leaks, you can improve air distribution, reduce energy consumption, and lower monthly bills. Don’t delay repairing the ductwork to enjoy long-term savings and enhanced comfort.

Related Article: Heat Pump: Auxiliary Heat vs Emergency Heat

Dirty Heat Pump Coil

image of air handing unit or fan coil unit of a heat pump

The heat pump’s outdoor unit is particularly susceptible to dirt and debris accumulation due to its location. Dust levels in the environment and the presence of pet hair, grass clippings, and dried leaves can all contribute to dirt buildup on the heat pump coil over time. A layer of dirt on the coil can hinder the absorption or expulsion of heat, decreasing the unit’s efficiency. Regular cleaning is necessary to address this issue. A water hose with low to medium pressure can remove loose dirt, but high water pressure can damage the unit, so be careful with the settings. A light brush can be used to scrub stubborn spots off.

Indoor coils should also be cleaned, although they may be more challenging to access, so it may be best to leave the job to an HVAC technician. A heat pump tune-up service is a reasonably priced option that can deliver excellent results.

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Frosted Indoor Coil on Heat Pump

A frosted indoor coil could cause a malfunctioning heat pump. Although it may seem counterintuitive that a frosted coil would result in warm air during the cool mode, this is a common issue when you understand how heat pumps function. The low temperatures can cause moisture from the air to condense around the indoor coils, resulting in freezing. This ice buildup can prevent the coil from collecting heat properly, which can cause the unit to malfunction. The heat pump will need some downtime to enter fan mode, forcing warm air through the coils and accelerating the defrosting process.

Related Article: Heat Pump Never Reaches Good Temperature In Cold Weather

Do I Repair or Replace the Heat Pump?

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Before deciding whether to continue paying for heat pump system repairs or replace the entire heat pump, homeowners should consider the following factors:

  • Heat Pump Warranty: Check if the heat pump system is still covered under warranty. If it is, then parts replacement and labor fees will be covered, making it logical to keep the unit until the warranty runs out.
  • Heat Pump Age: Although heat pumps can run for over a decade, they are more likely to experience wear and tear once they pass the ten-year mark. This can lead to frequent HVAC repairs, which can inconvenience many homeowners. Getting a new heat pump may be a more reliable solution.
  • It is wise to calculate the repair costs versus the replacement cost. Homeowners can add up their repair bills from the previous years and estimate their future expenses. If the cost of repairing the heat pump is higher than the price of a new one, then replacing it may be more cost-effective.
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Heat pumps are a great way to keep your home comfortable throughout the year, providing both heating and cooling options. However, if you notice that the heat pump is blowing hot air in cool mode, it is vital to investigate the issue. This can be caused by one of the reasons mentioned above. Contact a professional HVAC technician to get immediate assistance.

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Townsend Energy provides exceptional heating and cooling services throughout Northeastern Massachusetts, Southern New Hampshire, and Maine. Our team comprises highly skilled and certified technicians who offer top-notch HVAC tune-ups, installations, repairs, and replacements. Our technicians possess the necessary knowledge and experience to service your HVAC system with precision and efficiency.

We take pride in offering competitive rates for heating and cooling services in the area. Our maintenance services are designed to improve your home’s comfort levels while enhancing energy efficiency and lowering heating and cooling costs. Whether you require an HVAC repair or replacement, we can suggest the most suitable option that meets your needs and budget. We stand behind our service with a satisfaction guarantee to ensure you are pleased with our services. To book an appointment, contact Townsend Energy today. We also provide complimentary in-home estimates.

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