How to Repair a Frozen Air Conditioner | Ask This Old House

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Published 2016-06-02
Plumbing and heating expert Richard Trethewey shows how to prevent ice buildup from shutting down an air-conditioning system. (See below for steps.)

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Richard troubleshoots an air conditioning coil that freezes up with use. Richard replaced a 4-ton air conditioner with a more appropriately sized 3-ton air conditioner.

Steps for How to Repair a Frozen Air Conditioner:
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.
12. Braze new copper connections to the refrigerant lines.
13. Insulate the suction line.
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.

Expert assistance on this project was provided by Papalia Plumbing [papaliaplumbing.com/] and Air Purchases [www.airpurchases.com/].

About Ask This Old House TV:
Homeowners have a virtual truckload of questions for us on smaller projects, and we're ready to answer. Ask This Old House solves the steady stream of home improvement problems faced by our viewers—and we make house calls! Ask This Old House features some familiar faces from This Old House, including Kevin O'Connor, general contractor Tom Silva, plumbing and heating expert Richard Trethewey, and landscape contractor Roger Cook.

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How to Repair a Frozen Air Conditioner | Ask This Old House
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