How Does A Heat Pump Work In Winter?

Jalin Coblentz
by Jalin Coblentz

Most people are familiar with heat pumps when it comes to using them as air conditioners. A unique feature about a heat pump is that it can be used during the winter to heat your home and not just during the summer to cool it. But how can a split system like a heat pump perform both of these functions?

Heat pumps have the ability to reverse the flow of their refrigerant. Reversing the flow supercools the refrigerant and makes it colder than the outside air. The refrigerant then absorbs the heat from the air and transports it inside your home where it’s dispersed through your duct system.

A heat pump’s ability to perform in both winter and summer makes it a desirable option for homeowners. However, there are a few things that you should know before jumping the gun and purchasing a heat pump. In this article, we’ll look at how a heat pump works and what its best application is.

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How Does a Heat Pump Work in Winter?

A heat pump works in the winter by sucking cold air from the outside atmosphere, heating it up, and transferring it into your home. Heat pumps do this so quickly and effortlessly that you don’t realize what’s happening until you suddenly have heat in your home. Let’s take a more in-depth look at how a heat pump operates in the winter.

It Absorbs and Transfers Energy

A heat pump consists of an outside unit, an inside unit, and a series of pipes that connect the two. There is refrigerant running through the pipes and either unit that forms a closed loop. This allows the refrigerant to travel from the outside unit, through the pipes, and into the inside unit consisting of an air handler and an A-coil.

The outside heat pump unit absorbs heat out of the cold, winter air and transfers only the heat to the inside unit. It absorbs heat out of cold air by making so that the refrigerant inside of it has a lower temperature than the air itself. This allows heat to be absorbed and transferred via the pipes connecting the inside unit to the outside unit.

It Requires Special Refrigerant

The only reason that it’s possible to absorb heat out of cold air is through the refrigerant contained inside the heat pump. The refrigerant must have a lower temperature than the outside air, but must still be warm to change the cold air into hot air. For that reason, R-410 refrigerant is used because it has a boiling point of 14 degrees Fahrenheit. This allows the refrigerant to be cold and hot simultaneously.

Next, Comes the Compressor

The compressor on the outside unit then compresses the refrigerant and superheats it to a temperature of 104 degrees Fahrenheit.

Hot Refrigerant Goes to the Air Handler

From there, the compressor pushes the now hot refrigerant from the outside unit to the inside unit. It then circulates throughout A-coil at a temperature of 100+ degrees. The air handler circulates air that flows over the now hot A-coil and heats up the air itself.

Normal Air Dispersal Happens

Once the air inside the coil gets hot, the air handler fan turns on and blows it through your duct system and into your house. All of these things happen within seconds or a minute of turning on your heat pump. You can change from cold air to hot air in very little time, which is necessary for spring and autumn days when temperatures change quickly.

Your Heat Pump Adjusts Accordingly

Your heat pump adjusts the temperature of the refrigerant according to what your needs are. When you turn the thermostat up and down, your heat pump will alter the refrigerant temperature accordingly. Simply put, the goal of your heat pump is to give you the desired temperature no matter what time of day it is or what part of the year it is.

It should be noted, however, that heat pumps do have their limitations. Once the ambient temperature drops below a certain point, the heat pump can no longer lower the refrigerant enough to absorb heat out of the air. When that happens, you’ll need a backup source of heat or emergency heating.

Should a Heat Pump Run Constantly in Winter?

For those who are used to a furnace and switch to a heat pump, they’re often worried about how much it runs in winter.

However, because of how heat pumps are designed to operate, it’s not unusual for them to run constantly in winter. The heat pump is constantly running in order to constantly absorb heat from the outside air. For that reason, you shouldn’t be worried if your heat pump runs frequently or constantly when it gets to be 30 degrees and below.

However, if it’s not overly cold outside and your heat pump is constantly running, there might be a problem. Here are a few possible reasons that your heat pump is constantly running when it’s over 40 degrees outside.

Refrigerant Leak

If you have a refrigerant leak, even a microscopic one, your heat pump will run constantly in both summer and winter. The reason is that a heat pump is designed to operate with a set amount of refrigerant based on the size of the heat pump itself. If it starts to lose refrigerant, there won’t be enough to raise or lower the air temperature and it will be overworked.

Undersized Unit

If your heat pump is too small for the house you’re trying to heat up or cool down, it will run constantly. This is because it’s having to work too hard to raise or lower the temperature in an area too big for its design.

It’s in the Wrong Mode

Heat pumps can run as an air conditioner or as a furnace. There’s a reversing valve inside the heat pump that changes the course of the refrigerant according to what its setting is. If your heat pump is in heating mode but it doesn’t seem to be generating enough hot air, it’s possible that the reversing valve is stuck in AC mode. If that happens, your heat pump will run constantly without doing anything.

Do Heat Pumps Have Cold-Weather Limitations?

As previously mentioned, heat pumps have limitations in regards to how much heat they can generate during the winter. R-410 refrigerant is an incredible gas, but your heat pump can only lower its temperature so much. The only way a heat pump can do its job is by lowering the refrigerant temperature enough to make it colder than the ambient temperature.

However, once it gets to be around 25 to 40 degrees, a heat pump starts to struggle and gets overworked. It can no longer lower the refrigerant temperature enough to get it colder than the ambient temperature while still being able to compress it to 100+ degrees. For that reason, it’s not advisable to have a heat pump in extremely cold-weather areas with harsh winters.

With outside temperatures of 25-40 degrees Farhenheit, your heat pump will lose efficiency and will be insufficient to heat your home.

Explainer Video: How a Heat Pump Works

Related Questions

Is it ok to run a heat pump all night?

If the outside temperature is cold enough, your heat pump will run all night and there’s nothing wrong with that.

How often should a heat pump cycle on and off?

Your heat pump will cycle on and off according to how hot or cold it is. The more extreme the ambient temperature is, the more often your heat pump will cycle on and off. This isn’t a cause for concern unless temperatures outside are relatively mild.

What’s the best temperature for a heat pump in winter?

The ideal temperature setting for your heat pump is right around 68 degrees, give or take a degree. This setting allows for comfort during the winter months without overworking your heat pump.

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Final Thoughts

Heat pumps are extremely handy and efficient heating and cooling appliances when used in the right areas. They will operate as well as any air conditioner during the summer but will struggle during the winter months with extremely cold temperatures.

For that reason, you should think carefully about how harsh your winters are before purchasing a heat pump system. If you have frequent temperatures of less than 30 or 35 degrees, a standard furnace might be a better option for you.

Jalin Coblentz
Jalin Coblentz

Before I started writing, I worked for 6 plus years in the plumbing, electrical, and HVAC business. I was primarily an HVAC installer but also worked as a plumber and electrician. Now I'm a copywriter, focusing on home improvement content and guides.

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