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Why Is Ice On My Outside Air Conditioner Pipe?

Two MSP technicians in front of a truck

Have frozen AC pipes? MSP technicians can help you

The Twin Cities are beautiful in the summer, with average temperatures between 75 and 85 degrees June through August, making it a little easier to tolerate the humidity. Even more so, your air conditioning unit helps keep your indoor spaces cool and comfortable.

As you run your air conditioning unit, you may start to notice ice building up on your air conditioning pipes even in the summer. Seeing ice buildup is definitely not normal. This blog will discuss the 2 most common reasons why you may be having this issue when it’s a humid 80 degrees outside:

Continue reading to help determine which issue you may have and how you can fix it.

MSP has served the Minneapolis St. Paul area since 1918. We’re family-owned and operated and hire only the best technicians to handle your heating and air conditioning needs. If your AC requires worry-free service or replacement, call us today at (651) 228-9200 or schedule a free appointment online.

Restricted airflow over the evaporator coils

Photo of a frozen evaporator coil

Evaporator coils freeze if there isn’t enough airflow blowing over them

The evaporator coil is the part of your air conditioner that holds the refrigerant, a fluid that absorbs the heat from the air in your home. Warm air from inside your home is pulled in through the return vents and passes over the evaporator coils in your AC unit. Refrigerant inside the AC pipes removes the heat in the air and then pushes it outside through the condenser. This chilled air is then recirculated back into your home through your ducts and vents.

When the warm airflow over the evaporator coils is restricted, the refrigerant can’t do its job. When there isn’t enough warm air flowing over the evaporator coils, there is not enough heat to balance the cold refrigerant. Not enough heat counterbalancing the refrigerant will lead to ice forming on the pipes.

Several things can be causing restricted airflow over the evaporator coils, including:

  • Blocked air vents: Air can’t easily flow through your HVAC system if vents are blocked or covered by furniture, wall hangings, or dirt and grime.
  • A dirty air filter: Dirt, lint, and pollutants clogging your air filters will dramatically reduce the amount of air your AC can pull in from your home, which, in turn, reduces the airflow over the evaporator coils.
  • Issues with the blower fan: The blower fan is inside the air handler of the AC unit, and it helps to push cooled air through your ducts and vents and throughout your home. When the fan is not working properly, the airflow of the cool air entering your home and the warm air flowing back into the AC unit can be restricted or slowed.
  • Collapsed or leaky air ducts: Leaks and collapsed ductwork will reduce the amount of air circulating through your home and HVAC system as air escapes into the attic, ceilings, and crawl spaces instead of staying in circulation.
  • A dirty evaporator coil: When the coil is dirty, warm air passing over it won't touch as much exposed surface area as usual. Because dirt is clogging the coil, the refrigerant can't effectively cool the incoming warm air. Much of the heat will remain in the air, which will recirculate through your home. In some cases, the dirt on the evaporator coil can even freeze along with the pipes, and you may stop feeling cool air altogether.

What to do

To troubleshoot any of these potential issues, follow these steps.

  1. First, check your vents. These include the air vents that push air into your spaces and the return vents that pull air back through your HVAC system. Make sure they are clean, open, and unobstructed.
  2. Then, check your air filter to ensure it is clean and allows air to flow through. HVAC system air filters will be inside of your return vents. When you open the vent cover, visually inspect the filter. If it is brown or covered in dirt and lint that you can see, it’s probably time to replace it.
  3. Next, you’ll check the blower fan for your air conditioner. To do this, go to the thermostat that controls the AC unit and switch it from COOL to OFF. Then, locate the fan controls on the thermostat and switch the fan from AUTO to ON. When your fan is “ON,” it will blow air even if the AC isn’t running a cooling cycle. Doing so means more warm air will blow over the evaporator coils to help defrost the pipes. Leave the fan ON and the AC system OFF for 3 to 4 hours before turning the system back to COOL.
  4. If you still see ice on the pipes after completing the first 3 steps, it’s time to call in experts. A licensed HVAC technician can inspect your vents and the inside of your AC system to see if they are the cause of your issue.

Low refrigerant levels

The refrigerant cycle

How does refrigerant work?

Another issue that can cause ice on the pipes is low refrigerant levels. When refrigerant levels drop, there isn’t enough fluid to counterbalance the warm, humid air blowing over the evaporator coils. Not enough warmth can cause the moisture from the humidity on the coils to freeze.

Diagram of refrigerant lines

Refrigerant works in a closed-loop system

The refrigerant in your AC system is in a closed system of pipes, meaning that it stays in the evaporator coil and recirculates to be cooled and warmed over and over, so the fluid level should remain constant. So if your refrigerant levels are low, that’s a good indication that the coil has a leak.

Some other signs that indicate you have a refrigerant leak include:

  • The air coming out of your vents isn’t as cold as usual
  • Your energy bill is abnormally high
  • You hear a hissing sound from the pipes on your outdoor AC unit

What to do

Regardless of the refrigerant leak cause, it’s nearly impossible for a homeowner to resolve the problem independently. Refrigerant is a dangerous chemical, and only professional technicians should handle it. You’ll want to contact MSP Plumbing, Heating, and Air as soon as possible to have your system inspected and the refrigerant lines repaired.

Do you need a professional to inspect your HVAC system? We’ve got you covered with our 100% satisfaction guarantee.

Let the expert technicians at MSP Plumbing, Heating, and Air diagnose and troubleshoot the cause of your AC icing over. Schedule your AC repair or call us at (651) 228-9200 today.