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Should I Cover My AC Unit In The Winter?

Should I Cover My AC Unit in the Winter

Anyone who lives in the southern portions of the United States will tell you that having a good air conditioning system is essential because, for about two-thirds of the year, your unit is going to be running pretty much nonstop.

You’ll depend upon your AC to survive our hot, sweltering summers, when the temperatures frequently hit triple digits. You’ll also rely on your system during much of the spring and fall, since the 80s and 90s stick around for much longer here than in many other parts of the country.

During the hottest times of the year, homeowners may regularly clean or replace filters, pay attention to how their system is running and remove debris from around outdoor vents.

When the cold weather (briefly) sets in, however, many of us promptly forget all about our AC, basking in lower electric bills while we can. Some homeowners might not even give the air conditioner a second thought until the thermometer hits 80 degrees again. When you’re not living in Pittsburgh or New York, but in a warmer climate, you might deal with maybe one or two freezes a year, and snow is quite rare. 

Although you’re not going to be dealing with heavy snowstorms or subzero temperatures, you may wonder: Should I cover my AC unit in the winter? The answer is that this is probably unnecessary. The condensers in these units are built to endure both the mild winters in warmer climates and the extreme temperatures in northern parts of the country.

In this post, we’ll discuss how your air conditioning system works and what winter maintenance is necessary to make sure your heating and cooling needs are met, year round.

How HVAC Systems Work

There are several basic air conditioner parts and functions everyone should know. Here are the four key elements in an AC unit. We’ll describe them below so you won’t have to ask “What is refrigerant?” ever again. 


The evaporator is typically found inside of your home. This component converts liquid refrigerant to a gas by absorbing the heat in the air inside of the compartment. 


Refrigerant is a chemical compound that can be either a fluid or a gas which absorbs the heat present in an environment as air passes through your system. One of the more common air conditioner problems is a refrigerant leak. Your unit will not operate efficiently if the refrigerant charge does not exactly match the manufacturer’s recommendations. The performance of your heating and cooling system can be compromised if refrigerant was undercharged when your unit was installed, and a leak can be harmful for the environment.


The condenser is usually located outside the house. This purpose of this part of your air conditioning system is to convert high-pressure gas from your compressor into a liquid. Although these components are designed to weather the elements, some homeowners do cover these parts during the winter months, when the system is not in use. The most important thing to remember if you purchase an AC cover is to make sure to remove it before turning on your unit again when winter is over. 


Also often found outside, the compressor concentrates heat by circulating refrigerant under pressure in your cooling system. 

Standard AC units work based on a thermodynamics principle known as the Joule-Thompson Effect. Based on this principle, when an AC’s refrigerant expands, there’s an accompanying drop in temperature and pressure. Similarly, when the refrigerant is compressed, its temperature rises.

The evaporator coil in an AC unit causes the refrigerant inside to expand, thereby resulting in a rapid cooling of the coil. The air conditioner blower then pushes your home’s air over the now cool coil. The refrigerant in the coil absorbs heat from the hot air in your home. The cool air is then blown back into your home.

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Once the refrigerant absorbs heat from the air in your home, its temperature rises, and the substance transitions from a liquid to gaseous state.  The now gaseous refrigerant is pushed out of your home into the condenser and compressor parts of the AC.

Here, the refrigerant is condensed and compressed back into a liquid state. In the process, the compound loses its heat to the environment. The now cold refrigerant is pumped back into the evaporator inside the house. The cycle repeats, as needed, to keep the air in your home cool.

Besides cooling air, the evaporator also plays an essential role in dehumidifying the air in your home. As the home’s air blows over the evaporator coil, the coil wrings out atmospheric moisture from the surrounding environment. The water that leaches out of the air can pool in the AC unit, so most devices have a way of draining this moisture out.

What’s the difference between the terms AC and HVAC? It’s pretty simple, really:

  • An AC unit is only designed to cool your home.
  • HVAC units do much more than just cooling. These systems cool, warm and ventilate a home.
  • Therefore, HVAC systems are somewhat more complex than AC systems. A typical HVAC system consists of an AC unit, a heating element or furnace and a network of ventilation ducts and vents.

Unless you’re dealing with a window unit for a single room, when most people say “AC system,” they’re really talking about an HVAC system.

Now that we have an overview of how air conditioning works, let’s look at some of the reasons why a typical AC unit can freeze up.

air conditioner freezing up outside unit

Why Is My Air Conditioner Freezing Up Outside My Unit?

An air conditioner may freeze up if there is a change in the normal mode of operations. Some of the most common cause of AC freezing include insufficient air flow, inadequate refrigerant and mechanical problems.

Insufficient Air Flow To The Evaporator Coil

When air flows over the evaporator coil, heat is released to the coil. This heat keeps the coil warm. If this airflow is inadequate, the temperature of the refrigerant within the coil may continue to drop because the coil isn’t getting warm enough. Eventually, the cold refrigerant may cause your AC to freeze up.

Inadequate Amount Of Refrigerant

If your AC is low on refrigerant—which can happen if you have a leak—the little amount your system contains is forced to expand a great deal within your unit. More expansion equals greater temperature drops. If the overall temperature drops to below the freezing point, your AC may freeze up.

Mechanical Problems Within The Unit

Problems, including as kinks along the refrigerant lines, blower fan failure and clogged filter dryers, can alter the pressure balance within an AC system. The resultant pressure imbalance may then cause temperature anomalies that result in an AC unit freezing.

Other problems that might cause AC freezing include:

  • Faulty thermostats
  • Issues that hinder proper drainage of the water that condenses during dehumidification

What should you do when an AC unit freezes up at night? That’s another issue homeowners are usually unsure of how to best handle.

AC unit freezing up at night

AC Unit Freezing Up At Night: What’s Going On?

Remember how we talked about temperatures staying warm late into the fall in the south? Or when the mercury reaches 80 degrees—or higher—early in the spring?

Well, here’s the thing. Those high temperatures tend not to stick around all the time. Maybe the afternoons are hot, but the mornings and evenings might get cool. Another scenario is hot spells that come and go every few days, followed by more “seasonally appropriate” temperatures.

If you neglect to turn off your air conditioning when the temperature gets cooler again, you may unknowingly wreak havoc with the system. Most often what happens is that people get hot in the afternoon, turn on their AC to cool down, then forget and leave the system on overnight.

What happens at night? The temperature drops. Sometimes drastically.

When this happens, AC problems are more likely. In some cases, your system can even freeze up as it struggles to work in the cold air.

What happens when your AC freezes up?

Consequences Of An Air Conditioner Freezing Up

A frozen AC unit is bad news for an obvious reason: your system doesn’t work correctly.

If left unchecked, freezing could, in fact, destroy your entire central air conditioning system. No homeowner wants that to happen.

During freezing, water expands as it turns into ice. If this expansion occurs within the air conditioning system, you could be faced with broken parts and other damages that are expensive to repair.

HVAC winter maintenance

How Can HVAC Winter Maintenance Help?

Maintaining your air conditioner and heater during the winter months isn’t complicated. Performing periodic maintenance will go a long way in preserving your heating and cooling system and saving you the trouble of doing major repairs when spring arrives.

The experts recommend homeowners do the following in winter to save on energy costs and keep you feeling comfortable in your home:

  • Use a programmable thermostat to keep your indoor temperature as low as possible, while being comfortable.
  • Set your temperature a few degrees cooler when you are asleep or when you are away from your home.
  • Replace or clean your furnace filters, according to manufacturer recommendations, or once a month.
  • Move furniture, carpet and window treatments so that they are away from registers and heaters.
  • Remove dust or any other debris from your vents.
  • Open drapes and other window coverings on your windows on sunny days to naturally warm your home and close them at night to keep cold from the winters from entering your home.
  • Have your heating system professionally inspected before the colder months come to make sure your venting system, heat exchanger, controls and fluid levels are working and at operating at recommended levels.

HVAC tips for winter

Additional HVAC Tips For Winter

As we’ve already stated, air conditioners typically don’t need to be covered during the winter months. If you are concerned about your outdoor AC unit freezing, talk to a trusted air conditioning technician about what cover would work best for your unit. The most important thing to remember if you do choose to cover your unit is to take it off before you turn on your AC again.

HVAC/AC experts recommend the following tips to help in maintaining your air conditioning unit throughout winter and to ensure peak performance for many years.

Switch Off The AC

Your AC might turn on during an unusually warm winter day. When this happens, some water might get into the system and cause damage when it later freezes. Look for the AC switch at the air conditioner circuit and turn it off until you need to cool off your home when warmer weather hits.

Clean The AC/HVAC Unit Thoroughly

Remove any leaves, debris, twigs, grasses, bugs, dirt and dust from the AC unit. You can use a hose to give the unit a thorough cleaning, provided that temperatures aren’t hovering right around freezing. If possible, be sure to clean the outer casings, air ducts, outer and inner coils and all other air conditioning controls that might be dirty. This task requires some level of dexterity and therefore it is best left to a professional.

Cover Exterior Exposed Pipes

Place foam pipe covers around the pipes outside of your unit. Use covers that fit the pipe’s length and diameter adequately, and hold them in place using duct tape. Foam covers are excellent insulators that protect AC pipes from freeze damage.

Check Your AC Periodically

Inspect your air conditioner during the cooler months of the year—preferably once a week. Test the integrity of the AC cover and brush off any water or frost that may have accumulated on the unit. Also, be sure to also remove any leaves, twigs and other debris from the cover.

ABC Can Protect Your HVAC System Year-Round

Always remember that regular maintenance is needed to ensure that your heating and cooling system continues running perfectly. Manufacturers recommend that you call an experienced professional to look at the state of your AC before winter begins. The HVAC specialists at ABC Home & Commercial Services can diagnose and resolve any problems that may compromise the efficiency of the air conditioning in your home. In any kind of weather, ABC can keep your living spaces comfortable.

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