Help Keep Your Air Conditioner From Freezing Up!

June 24, 2016

Have you ever heard of an air conditioner ‘freezing up,’ and then shutting down the system at the worst possible time? What is an AC freeze up, how is it caused, and how can it be avoided? Let’s take a closer look:

What Is An Air Conditioner Freeze-Up?

On a central or ductless air conditioning system, a freeze-up is typically caused when the indoor part of the system—specifically, the evaporator coil located by the output side of the blower unit—becomes coated in ice, preventing air flow from the unit into your home. Ice may often appear in other areas of the AC system as well. Essentially, a freeze up stops your air conditioner from cooling your home, and the system must be shut down until the situation is remedied.

How Is An AC Freeze Up Caused?

Lennox AC CondenserAn AC freeze up can be caused by many things, such as a problem with the refrigerant charge, a parts failure, running the system when it’s too cool outdoors, or airflow issues. The most common cause of a freeze up is an airflow issue caused by a clogged furnace filter. If the filter in your furnace or air handler is neglected it will restrict airflow and adversely affect refrigerant pressures in the system, the end result being an iced-over indoor coil and no cooling to your home! Closing too many supply registers around the home, or blocking return air grilles, can also result in an airflow-related freeze up. The operable concept here is that air must be allowed to flow freely and through the ducting and furnace or air handler. In the summertime, be sure to check your furnace filter regularly. Some homeowners replace the filter as often as once per month. As no two systems are identical, the frequency required for changing the filter can vary.

What To Do?

If your air conditioning system appears to be working but little air is coming out of the registers, the first thing you should do is turn the power off to the system and check the furnace filter and the ducting by your furnace. If the metal ducting on the output side of the furnace shows signs of frost or ice, or is ice cold to the touch, you are likely dealing with a freeze up. If the furnace filter is clogged, the good news is that you may be able to solve the problem yourself! Simply replace the filter and let the ice thaw out. This may take several hours depending on the amount of ice. Don’t be surprised if you see a puddle of water collect on the floor as the ice melts. When your system is frozen, you can also contact an HVAC professional for a service call, but often there is little they can do until the system thaws.

If the furnace filter is not clogged, the next thing you can do is check all the supply registers and return air grilles around the house, making sure they’re open and providing no obstruction to airflow. If all registers and grilles are open, then leave the system shut down and contact your HVAC service contractor. Your system also has a large outdoor component, called the condenser or condensing unit. The condenser has an aluminum-finned coil wrapped around it, and if this coil is plugged with things like dust or leaves (think cottonwood trees!), that can also cause a freeze up. If you find this to be the case, contact your HVAC contractor to discuss the situation and determine the best course of action. You may also consider consulting your contractor for further maintenance, as it could turn out to be something requiring specialized skills and equipment.

An Ounce of Prevention

We have touched briefly here on some common maintenance issues, which if neglected, can take your air conditioner down at the most inopportune of times. A freeze up condition can often be avoided by regular routine maintenance of your system. Some of these tasks are things that a homeowner can address him or her self. However, checking the refrigerant charge and testing performance of vital components like the system’s compressor, are important procedures that should be addressed annually by an EPA and NATE certified technician. We recommend learning more about the annual maintenance that your system requires, and exploring an annual service agreement with your trusted HVAC service contractor. An ounce of prevention can certainly be worth a pound of cure when the temperature outside skyrockets!