This Old House plumbing and heating expert Richard Trethewey shows how to prevent ice buildup from shutting down an air-conditioning system In this video, This Old House plumbing and heating expert Richard Trethewey shows how to prevent ice buildup from shutting down an air-conditioning system. 1. Clean or replace the return-air filter to ensure it's not obstructing the flow of fresh air to the air conditioner. 2. Confirm that the size of the air-conditioning unit can accommodate the diameter and number of cool-air ducts. 3. Remove the metal access panel to expose the evaporator coil. 4. Check the size of the outdoor condenser unit. Typically one ton of cooling is needed for every 500 to 600 square feet of living space. 5. If the condenser is too big for the house, it can cause ice to form on the evaporator coils and shut down the system. 6. Pump out and collect the refrigerant from the existing too-large condenser. 7. Disconnect the old condenser and cart it away.

8. Install a new appropriate-size condenser. 9. Connect the new condenser to the existing electrical power supply and refrigerant lines. 10. Remove the old evaporator coil and replace it with a new coil that matches the tonnage rating of the new condenser. 11. Reconnect the ductwork and seal the new evaporator cabinet at top and bottom with sheet metal strips and foil tape.hvac induction unit 12. Braze new copper connections to the refrigerant lines.window ac unit scrap value 13. Insulate the suction line.hvac unit 31 exam 14. Connect PVC pipe to the condensate drain and then attach the pipe to a pump. 15. Run flexible tubing from the pump to a drain. 16. If necessary, add refrigerant to the new system. 17. Turn on the air conditioner to ensure it's operating properly.

Your browser is out of date. For the correct work of a site, install the new version.What you will learn from Frozen Air Conditioner article:the major two reasons why your air conditioner has ice on it somewhere (otherwise you likely wouldn’t be here)the difference between a heat pump and an air conditioner in winter and summer operationwhy airflow is essential to a central air conditioning systemenough about HVAC refrigeration to help you determine the problem of a frozen air conditioner. We have many other related articles. Use the search feature to the right to help you find other related articles.Frozen Air Conditioner HVAC TroubleshootingIce on Air Conditioner - This is a common problem for people and it can be caused from one of two things:Lack of airflow across the evaporator coil orA problem with the refrigeration system.Most people figure out they have a frozen airconditioner when they are outside and see ice building up on the outside condenser unit or ice on the refrigeration pipes.

Others know they have this problem when they see the air handler and the pipes running into the air handler have ice. This, in addition to a noticeable decline in cooling capacity, is a sure sign you have problems that need to be resolved immediately. The best thing to do once you notice your air conditioner is frozen is to turn it off. On the thermostat turn the fan on but leave the cooling off. This will melt the ice on the evaporator coil. If you leave it on it will continue to make ice.If the coil is frozen when the technician arrives he cannot do anything. The coil must be defrosted to properly charge the system. Make sure you turn the cooling off but leave the fan running. If it is summer and you have a frozen heat pump (a heat pump provides heating and cooling using the process of refrigeration) you can turn it to heating mode and everything will defrost. However, be aware that if an excessive amount of ice is on the evaporator coil (located at the air handler usually inside the home) defrosting the frozen heat pump may overwhelm the condensation drain.

It is possible you will have some water damage as a result. This may happen either way you defrost the system especially if the air handler is located in a hot attic.Necessary StepsTurn the air conditioner to the off position and turn the fan switch to on (manual on) on the thermostat selector switch. This will help aid the defrost of an icy evaporator coil and the rest of the frozen air conditioning unit. This type of air conditioner problem can cause severe water damage because the ice melting from the air handler overwhelms the drain. So be aware of that potential additional problem if your AC system is frozen.Why is the Air Conditioner Frozen? Possible Cause Number OneThis is enough to cause concern because the air conditioner pipes have ice on them. Ice on the pipes is not normal. An airconditioner or heat pump is not designed to make ice. An air conditioning unit is designed to cool the home or business and it is abnormal for ice to form on an air conditioner. A heat pump will form frost or ice on the outside condenser coils in the winter time but frozen condenser coils is common and the heat pump is equipped with a method to defrost the condenser coils.

To solve the problem you need to look at airflow first. Every airconditioner or heat pump system is designed to have a specific amount of air flow go through the evaporator coil when the unit is in the cooling or air conditioning mode. Unless you have a high-velocity air conditioning system (most people do not) the evaporator coil needs at least 400 cubic feet per minute (CFM) of airflow across the evaporator coil per ton of air conditioning. If you have a 3-ton air conditioning unit or heat pump you need 1200 CFM’s of airflow across the evaporator or the air conditioner will freeze up. This means that if you have a:Extremely dirty filter orToo many supply vents closedCollapsed duct workBad blower motorSomething obstructing the ductworkDirt built up on the evaporator coil Airflow ConclusionOr anything else which would restrict airflow you will get ice build-up on the airconditioning system. This will cause a diminished capacity for the system to cool if it will cool at all. Defrost the system and then check the airflow.

Make sure the entire system is defrosted before checking the airflow of the system. It may take several hours to defrost the air conditioning system completely. The important part is to make sure all the ice has melted from the evaporator coils before checking airflow. After checking the airflow and you find a problem then have it repaired or taken care of. If you don’t find a problem then proceed to the next air conditioning problem below.2. Possible Cause Number TwoA frozen air conditioning system can also be caused by a refrigeration problem. The most common problem is a refrigerant leak (refrigerant is commonly referred to as Freon. Freon is a trademark name of DuPont Corporation). This means that the air conditioning is low on refrigerant. This leak needs to be repaired and then the system recharged by a professional. When the refrigerant leaks out the air A frozen air conditioning system can also be caused by a refrigeration problem conditioner pressures drop in the evaporator.A pressure drop in the evaporator coil means that the refrigerant will likely be colder than the dew point.

When the evaporator coil in your air conditioner or heat operates below the dew point the moisture or humidity in the air will freeze to the coil. A little frost will appear and then more frost on the air conditioner evaporator coil. This will eventually form into ice and restrict the air flow of the air conditioning system. An air flow restriction in the air conditioner will only exacerbate the problem. You need to call a professional to have this problem repaired.CertifiedThey have all the tools necessary to repair a refrigerant leak and restore the frozen air conditioner to normal operation sans the ice. There is another refrigeration problem which will cause the air conditioner to freeze up. This will require the attention of a trained HVAC professional to troubleshoot and repair the frozen air conditioner. Remember, when you see ice on your air conditioner pipes shut the system down and allow it to defrost. Check for proper airflow. If proper airflow is not present find the problem (or call in an HVAC professional to find and repair the problem).