How Often Should A Heat Pump Defrost?

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The defrost cycle is known to make your heat pump and HVAC system operate effectively. As a homeowner, you may be wondering how often a heat pump is supposed to defrost, especially during winter. We have consulted some experts in this field to get your question answered.

Heat pumps tend to defrost often when frost conditions are taking place. A unit usually runs for no less than 35 minutes following startup before the first defrost is completed. However, defrosts shouldn't be more than roughly every 40 minutes. 

The defrost cycle should take time so frost or ice will melt, but it should be quick enough to be energy efficient. Continue reading to learn more about the defrost cycle and how it works.

Heat pump system in modern house, How Often Should A Heat Pump Defrost?

The Heat Pump Defrost Cycle

A defrost cycle is a system that involves the formation of ice and immediately fixing it. When it comes to heating mode, the heat pump collects heat from outdoor air and transfers it to the inside of your house so it can be warmed. Since the air outside your house is cool, the outdoor coil plays the role of an evaporator.

When the external temperature becomes cold, the air moisture freezes on the outdoor unit's heat exchanger, with the fan blowing the air across it.

Alternative energy concept with air heat pump

Why Do Heat Pumps Often Go Into Defrost Mode?

Several conditions affect how often a unit may go into defrost mode. Here are some of the factors:

Leak In The Refrigerant

This may affect how often the heat pump goes into defrost mode. When the leak is minimal, it does not affect the unit. However, when the leak worsens, the heat pump goes into defrost mode more often and becomes less efficient.

Damaged Reversing Valve

A damaged reversing valve can make the heat pump go into defrost mode regularly. The damaged reversing valve may not be able to alter the route of the refrigerant between the two coils (indoor and outdoor), thus leading to damage.

Bad Outdoor Coil

Air conditioner doing some checking for leaks

If your outdoor coil is damaged, there is a higher chance that your pump will go into defrost mode. You should check your coils regularly so you can work on them if damaged before the problem gets worse.

How To Know When Your Heat Pump Is In Defrost Mode

  • From the Iinside: There is a higher chance your unit is in defrost cycle when the system isn't heating anymore, and the fan is shut off. During the defrost cycle, you may notice a blinking light (visual indicator).
  • From the outside: Whenever the outdoor fan stops and the compressor is on, there is a higher chance your unit is in the defrost cycle.

How Defrost Cycle Works

The heat pump is reversely operated during the defrost cycle. It is the work of a defrost control to tell the reversing valve when it is time to send hot refrigerant outdoors so the outdoor coil will be melted. The outdoor fan is prevented from turning on, with the temperature increase of the coil aggravated anytime the pump switches over.

The length of time required to melt the outdoor coil differs. However, heat pumps are usually in the defrost cycle until the coil is about 58 degrees. The internal heater tends to stop when the unit becomes frost-free with the valve reversing. This will make the unit start the heating cycle. 

How Long Does Defrosting Last? 

heat conditioning unit in a residential backyard

A unit can be brought out of a defrost cycle if the sensors outside detect the temperature of the heat exchanger has increased well. The highest a system remains in the defrost cycle is about 10 minutes if the defrost cycle isn't stopped by the sensors in advance.

Never stop the defrost cycle because this may cause the system to run inefficiently, causing harm to the entire system. The time it takes for the heat pump to defrost differs. 

How Do You know When Your Heat Pump Is Having Issues?

If you notice that your heat pump is defrosting too often or not delivering the supposed heat since installation, it could be an operator error. If this happens, you need to consult the user manual. But if the consultation has been made and you have already ruled out user error, then it could be a contractor installation problem.

It could be that the unit is the wrong size for the space that needs to be heated. The best thing to do here is to either call the installer, or a good HVAC technician so the wrong sized unit can be replaced with the correct size. 

How Do You Force A Heat Pump To Defrost?

If you want to force your heat pump to defrost, simply turn on the fan. Blowing air can melt the equipment within 60 minutes. If the temperature outside is low, you can try setting up the fan on an exhaust setting. Leaving the fan on for a while might not be a solution to all freezing issues, but it can serve as a short-term solution. 

Another thing you can do is to turn on the defrost cycle manually. Changing the valve to air conditioning mode is how the defrost cycle works. The fan outside then goes off, changing the external evaporator into a condenser. 

How To Maintain Your Heat Pump

Maintaining your heat pump is an important part of owning one. If you follow these simple steps, you will be able to keep your heat pump running smoothly and efficiently:

  1. Clean or change your air filter when necessary.
  2. Ensure your outdoor unit is free of debris and foliage.
  3. Make sure the unit is turned off during power outages.
  4. Check for leaks.
  5. Always check your heat exchanger to make sure it isn't blocked.

Heat pump in outdoor

How Can You Reduce Defrosting?

Defrosting can be reduced by keeping your system in good condition. This can be done by carrying out seasonal maintenance checks on them. Also, make sure to clean and change your filters often so your unit will continue running smoothly.

Best Heat Pumps

Before choosing the types of heat pumps to buy, it's better to have a detailed picture of the climate zone you reside in, your budget, requirements, and most importantly, the location of your heat pump. It is better to go for a mini-split heat pump if you are furnishing an old building. If you reside near a large body of water in a rural area, an underwater heat pump should be on your list.

Another factor to consider when personal preference and geographical limitations are out of the picture is the installation and operational costs. Installing a geothermal system is expensive, but the operating costs are affordable compared to a ductless heat pump. 

Here are different types of heat pumps to choose from:

1. Air-To-Air Heat Pump

This is an energy-efficient air conditioning system. An air-to-air heat pump is cheaper to install and can offer sufficient heating and cooling in climate zones, making them ideal for use in different parts of the country. This heat pump uses air as the working fluid. Types of air-to-air heat pumps are mini-split and exhaust air heat pumps.

2. Underwater/Underground Heat Pump

Underground or underwater heat pumps are capable of providing efficient cool or warm air all through the year. Since they consume low energy, their heat pump efficiency is greater than other types. They help in heating houses during the winter months. Furthermore, underwater heat pumps cool houses during the summer months.

3. Hybrid Heat Pump

Hybrid heat pumps are cost effective, efficient, and environmentally friendly. They also provide flexibility because you can use them to heat or cool your home depending on the season. Hybrid heat pumps use the power of gas to heat and cool your home, but they also have battery backup.

Hybrid heat pumps have some disadvantages which include the need for an external source of power that may be costly. The installation process of this heat pump is not easy.

To Wrap It Up

Heat pump system in modern house

The frequency at which heat pumps defrost depends on how often you use them for heating and cooling. If you use them only for heating, your heat pump will not defrost regularly. But if you use them both for heating and cooling, your heat pump will defrost more often.

If you enjoyed reading this post, check out these related articles:

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How Long Does It Take for A Central AC To Defrost?

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