20,317 posts, read 15,073,405 times When a central air conditioner freezes up, what actually freezes is the condensor unit's evaporator coil. This is the part of the air conditioning system that transfers (evaporates) heat from the inside to the outside of the home. There are two primary reasons the evaporator coil may freeze, it can either be due to 1) restricted air flow, or 2) lack of sufficient refrigerant. Either way, the result is that the air conditioner's evaporator coil cannot operate to properly dissipate heat, and in effect 'overcools' itself. The result of this super-cooling is condensation (that's water formation), and eventually ice from that condensation as it cools below the freezing point. Yep, the A/C just turned into an old-school icebox. Basic Tips for AC Repair and Maintenance Filter is brand new. he checked air flow and temp conversion etc. The unit is 12 years old and never used hard. I never have my temp below 76 in the summer. Input and out put lines also freeze so does the tank inside the unit out side.

Its a carrier high eff. What ever he did seems to have made it worse. Originally Posted by tinman01 Well contact him to return and 1. either fix it properly or 2. you will have someone else do it and he will eat cost of the service if it is determined that his initial work, indeed made things worse. 222 posts, read 301,003 times inexpensive fiberglass filtershigh dollar thick filters restrict too much air flowI was a bit surprised to see this question, since this should be readily available information elsewhere, so I did a short search to see if there is a problem finding out the answer.  It turned out there is, in that there are a lot of incorrect or incomplete answers out there.  The best answer I came across was this:"All air conditioners try to freeze up, that is the goal of the refrigerant... to chill.It is the design of the system that prevents this freezing up from occurring.There are three basic reasons for air conditioner freeze ups:1) The two most common causes of insufficient air flow are dirty filters and under sized ducts.

A dirty filter limits air flow which in turn allows the cooling coil’s temperature to drop below freezing. Replacing the filter, monthly, usually alleviates this problem. Under sized ducts will also cause the system to freezeBecause it also limits the amount of air flowing over the cooling coil. This results in lowering the coil temperature and allowing the humidity in the air to collect on the coil and freeze.2)Refrigerant charge. ac water cooling systemThe refrigerant system teeters on a delicate balance. used outside ac unitIf the system is not charged correctly, the system will not function properly. size of outdoor ac unitThis malfunction may result in the poor cooling output and/or freezing up. Only a qualified, certified service technician can properly test and charge a refrigerant system.3) Outdoor temperature.

If night time temperatures are too low, the system will not operate properly, and freeze up may occur. The outdoor unit does not function well in temperatures below 60 degrees F. A special “ambient temperature” control must be installed to allow the unit to run properly in cool temperatures, or you may open your windows and save energy."  (, Air Conditioning Freeze Up .)Too many of the answers given on the web assume it is low charge, when it most likely is poor air flow due to an obstruction, which can be the filter, the coil itself being dirty, blocked vents, closed or dampered vents, or incorrectly set fan speed.  It can also be a symptom of too much refrigerant charge.  If the first thing your A/C serviceman does is hook up a bottle of refrigerant to your system, get a new serviceman.  The amount of charge should stay constant if the unit was installed correctly, so the most likely cause is a dirty filter, and hooking up hoses and gauges will not fix that and will typically lead to some incidental degree of refrigerant loss, especially when done carelessly, compounding the problem.

Keep your filters and ductwork and coils clean and you will eliminate most problems with freeze-ups.This article was crafted with the help of Mike Costa from Perfect Home Services The inner workings of HVAC systems can be perplexing to many people, but finding ice on a heat pump during the hot summer months will surely spark confusion among even the savviest homeowners. Thankfully, there are precautions that homeowners can take to avoid having their heat pumps freeze over during any season. Mike Costa, Technical Supervisor with Perfect Home Services in Chicago, offers his expertise on how to keep your heat pump free of ice and running smoothly. While many homeowners have separate units for heating and cooling, a heat pump uses the traditional mechanisms of an A/C unit to provide both. During the summer, a heat pump operates just like a standard air conditioner. In the winter, the heat pump takes in energy from outside and provides heat to your home by using a reversing valve that redirects the flow of refrigerant.

When used in the right climates, heat pumps can be very energy efficient because they heat your home using electricity and refrigerant instead of burning fuel with a traditional gas furnace. However, Mike warns that recurring freezes can damage a heat pump, so it’s important for homeowners to know how to avoid and treat heat pump freezes. “When a unit starts to freeze, you actually start to slug liquid back into the compressor, and you don’t cool the compressor properly,” says Mike. “This can cause severe damage to the compressor itself.” Replacing a compressor can be very costly and will likely waste any money saved on energy bills. Common Causes of Heat Pump FreezesMike explains that heat pumps work best in “climates that do not get below around 32 degrees ambient temperature.” But even homeowners living in the ideal climates for a heat pump will have to endure occasional drops in temperature. During cold spells, look for the accumulation of ice on coils and Freon lines, says Mike.

Many types of heat pumps have a defrost cycle to combat brief periods of below-freezing temperatures, but Mike warns that any prolonged icing will inhibit airflow and potentially damage your system.Unfortunately, many things that can go wrong in an installation will block airflow and consequently cause your heat pump to freeze. Mike says that mismatching is a common problem when heat pumps are installed, making it especially important to work with reputable contractors. Oftentimes “the wrong-sized coil is put with the wrong-sized pump; the wrong-sized heat pump is put with the wrong-sized blowing motor in the furnace; or the Freon lines are not sized correctly,” says Mike. Hiring a knowledgeable professional will ensure that your heat pump has the correctly sized components to provide year-round comfort in your home.Heat pumps become susceptible to icing when the refrigerant levels are too low. A perfectionist when it comes to HVAC, Mike says that “there’s a right level for refrigerant.

A lot of guys will read it as being ‘close enough’ to the perfect level.” Low refrigerant levels can also cause problems with the compressor by forcing it to work overtime. You must be EPA certified to work with refrigerants, so always call in a professional to check these levels. Mike says that homeowners can identify a freezing problem if they either visually inspect their unit for ice or notice a problem with airflow in their homes. Airflow problems will typically result in your home not heating or cooling as it normally does, Mike notes. Remember that freezing can occur in either the winter or summer, so if your home does not feel as if it is cooling properly on a boiling summer day, don’t rule out the possibility of ice on your heat pump. Ways to Avoid a Heat Pump Freeze Have an annual inspection. While we unfortunately cannot control the weather, there are many preventative measures that homeowners can take to avoid heat pump malfunctions that cause icing. Mike says that “during a maintenance visit, the refrigerant levels are going to be checked, the coils are going to be cleaned, the electrical components are going to be checked, and the fan motors will be inspected.”

Without periodic inspections, your heat pump will be vulnerable to recurring freezes, which Mike says can severely damage your system. Consider a hybrid heat pump. Heat pumps are not typically recommended for climates that experience frequent freezes, but many homeowners would still like to avoid using their furnace as much as possible to save on energy costs. According to Mike, hybrid units are increasing in popularity because they “use the heat pump until the weather reaches freezing temperatures, and when it gets lower, there’s another controller that automatically kicks in the furnace for backup.” For those living in extreme cold, heat pumps designed specifically for cold climates are promising options, but they are still in the early stages of development and implementation. Be advised that you should never attempt to fix a heat pump yourself. Not only do you have to be EPA certified to work with refrigerants, but “you can really get hurt,” says Mike. “Depending on the heat pump, particularly newer ones, there are high-pressure gases inside the Freon levels, not to mention its high electrical charge.”