Heat pumps are generally considered the best option for heating in Florida. That’s because they are the most efficient heating option in places that experience mild winter weather. There is also the added advantage that the same unit can effectively cool your home during the warmer parts of the year. Despite being able to provide effective heating, heat pumps can sometimes experience issues that cause them to suddenly start putting out cold air. Let’s explore the different reasons this can happen so that you know what to do if your heat pump starts blowing cold air when it should be heating.
Wrong Thermostat Setting
Any time you notice your heat pump starts blowing cold air, the first thing you should check is your thermostat. Specifically, you want to make sure that the thermostat is set to heating mode and that the fan is set to On, not Auto. If the fan is set to Auto, it will just run constantly. That means the system will stop putting out heat once the heat pump outside shuts off. As a result, the air coming out of your vents will quickly start to feel somewhat cool. When the heat pump itself is running, the air the system puts out will normally be around 90 degrees. If the heat pump is off and the fan is still running, the air coming out of your vents will only be as warm as the current temperature in your house. Even if your home feels warm, the air the system is putting out will feel fairly cool on your hand since it’s not nearly as warm as your body temperature.
Dirty Coils
Just like a standard air conditioner, a heat pump has two coils that allow the refrigerant that flows through the system to capture and transfer heat. One coil is located within the air handler unit inside the house and the other is outside in the heat pump itself. Each coil serves a different role, depending on whether the heat pump system is currently heating or cooling. When the system is operating in heating mode, the outdoor coil functions as the evaporator coil and allows the refrigerant to absorb heat from the air outside the house. That means the indoor coil functions as the condenser coil and allows the refrigerant to release the heat into the air inside.
Both of the coils in a heat pump system need to be cleaned regularly to ensure that the system can heat (and cool) effectively. When the coils are overly dusty, it interferes with the heat transfer process since the dust creates an insulating layer. If the outdoor coil is dirty, the refrigerant isn’t able to absorb nearly as much heat as it should. That means it won’t get nearly as hot as it needs to for the heat pump to heat effectively, resulting in much less heat flowing out into the air inside the home. Similarly, dust on the indoor coil basically traps the heat. That means that not nearly as much heat will flow out into the air in the home as it moves through the air handler. In either case, the result is that the air the heat pump system puts out won’t be nearly as hot as it should be when the system is working properly.
Defrost Cycle Is Running
When a heat pump is heating, the refrigerant is extremely cold when it gets pumped through the outdoor coil. This leads to ice slowly forming on the coil any time the outdoor air temperature is 40 degrees or less. The buildup of ice eventually prevents the refrigerant from absorbing any heat, which is why a heat pump may need to occasionally defrost when running in heating mode. A heat pump in Florida usually won’t need to run its defrost cycle, but it can happen on unusually cold days and lead to it blowing cold air for a few minutes.
The reason that a heat pump system blows cold air when defrosting is that it has to switch over to cooling mode. It starts absorbing heat from inside so that it can then pump hot refrigerant through the outdoor coil to melt all of the ice on it. It typically only takes a few minutes for the coil to completely thaw out and the heat pump to switch back to heating mode. Any time you notice your heat pump is blowing cold air, you should just wait for 10 to 15 minutes to see if it again starts blowing hot air. If the air is still cold after waiting, it indicates your heat pump isn’t working correctly for some reason, and you need to have a technician inspect it.
Malfunctioning or Worn Out Reversing Valve
The reason that heat pumps are able to cool and heat is that they have a reversing valve that allows the compressor to pump the refrigerant through the system in both directions. When heating, the compressor pumps cold refrigerant outside and then the hot refrigerant flows inside. The refrigerant then gets pumped in the opposite direction when the system is cooling. The valve always activates when you switch between the two modes, and it also must activate to switch over to the defrost cycle.
The reversing valve can sometimes get stuck in one position or simply wear out. When this happens, the heat pump will still run but it won’t be able to switch modes. If your heat pump blows cold air the first time you switch it to heating mode in the winter, you can be fairly certain that there’s an issue with the reversing valve stuck in cooling mode. Similarly, if your heat pump starts blowing cold air on a much colder day, the valve is likely stuck or broken, leading to the system being stuck in defrost mode.
Low Refrigerant Charge
One last thing that can cause a heat pump to blow cold air is if it no longer has the proper amount of refrigerant due to a leak. If a heat pump system is low on refrigerant, it will often lead to the outdoor coil freezing up more often when the system is in heating mode. The refrigerant also won’t absorb enough heat for the system to provide effective heating, which can lead to it blowing cold air.
Other Signs That You Need to Have Your Heat Pump Repaired
Just as if your heat pump blows cold air in winter, having it start blowing hot air in the summer obviously indicates it isn’t working as it should. This issue usually indicates that the indoor coil is frozen, which can happen because the system is low on refrigerant or has some type of airflow issue. Another possibility is simply that the air filter is dirty and you need to replace it. Other signs you should watch for are if your heat pump often shuts off before your home is at the right temperature or if it starts running much longer or more often than usual. Unusual sounds, like humming, squealing, grinding and hissing, coming from either the heat pump or the air handler are also something you definitely don’t want to ignore. In addition, it’s important to monitor your electricity bills since a sudden spike in usage is likely related to some issue with your heat pump.
Since 1987, American Air, Plumbing, and Electrical has been providing professional heating, air conditioning, plumbing and electrical services in Oviedo and throughout Central Florida. Our team is ready to help with all of your heat pump repair and maintenance needs to ensure your cooling and heating works as it should. Contact us today if you need to have your heat pump inspected or for any other home service.
