There is Ice in my air conditioner

What causes an evaporator coil to freeze?

Let’s start by talking about how air conditioners work in the first place. In the simplest of terms, air conditioners are able to cool down your home by moving heat from one place to another (moves heat from inside your home to the outside). The evaporator coil contains refrigerant that runs from the inside to the outside in a constant loop. As the refrigerant enters the inside portion of the air conditioner (the evaporator) the molecules expand, cooling down the coil and allowing it to absorb heat from the air inside your home. It then returns to the outdoors, where the outside coil (the condenser) condenses those same molecules with the help of the compressor, causing the line to heat and expel that heat into the outdoor air, that’s why the fan on the outside unit always seems to blow warm/hot air. ?This happens over-and-over again until sufficient heat is removed from your home to bring it down to the temperature where things are comfortable.

In the event that heat is not able to be absorbed into the refrigerant, things start to go wrong. Most often, this occurs because the return air (the heat filled air inside of your home) is unable to get to the inside coil (evaporator). As a result, the refrigerant in the line begins to get colder with no heat to absorb. The line gets cold enough that the condensation on the outside of the line and moisture in the air, which normally drains away harmlessly, freezes over leading to a literal block of ice.

What are the most-common causes of this problem?

Essentially, anything that blocks airflow to the evaporator coil can lead to a frozen evaporator coil. Here are some of the most likely culprits:

1.?????Over time, your system’s evaporator coil will become covered in dust, dirt, grime, and more. This prevents it from getting the airflow it needs to properly move heat, which means that the system could then freeze over. Keeping your air filter clean and changing it on a regular basis is essential. If you have pets, you need to change your filter more often. Even if the filter says it will last 90 days or 6 months. Those are estimates for normal use in laboratory environments.

2.?????Blocked air ducts. In the event that you’ve manually shut many of your home’s floor or ceiling registers, the return air flow to the coil may not be getting sufficient airflow to continue operating correctly. Another common cause of this problem is when homeowners unknowingly block floor registers below furniture or rugs. Similarly, an extremely dirty air filter can block a main source of air from reaching the line.

3.?????Low refrigerant. The refrigerant line is a closed-loop system. However, in some cases, refrigerant may be lost through leaks or other problems. Without enough refrigerant, the molecules expand too much, causing a runaway cooling effect that results in a frozen-over system.

What should you do?

First things first, you’re going to want to turn off your air conditioner. At this point, any further operation by the air conditioner is just going to keep refreezing the already-frozen system. The next thing you should do is switch the thermostat to FAN only mode. This will keep the AC from running but allow air to move over the ice causing to thaw faster.

Once the system has fully thawed, the cause of the problem will need to be determined and it’s likely one of the three culprits: dirty coils, blocked air ducts, or low refrigerant. If it is the latter, a technician will need to recharge the system with the appropriate refrigerant type and address any leaks that caused the system to lose refrigerant in the first place.

By keeping your filter changed and clean, keeping your air ducts unblocked and registers open, you may be able to avoid having to call an HVAC technician saving yourself hundreds of dollars.