Frozen coils inside

Old 04-03-02, 07:27 PM
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Frozen coils inside

My Central Air System coils are frozen on the bottom. I have changed the filter, cleaned the fins, the outside coils are a little clogged but no more than normal. Is there anything else I can check before calling a service tech?
Old 04-04-02, 02:34 PM
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If you are getting

cooling and the unit cycles on and off----your drain is plugged.The water stands in the drain pan,then the freon freezes it.If your a/c is not cooling right you are low on charge or have air flow problems.Shut system down,place tstat to fan on position and see if the drain from unit drains.PDF
Old 04-04-02, 09:12 PM
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Last edited by jonathanisaac; 08-04-06 at 08:48 PM.
Old 04-05-02, 08:57 AM
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Frozen Coils

The evaporator coil above your furnace should be @ 45F, well above the freezing point. If there is any ice forming on the coil then there is a problem. Air flow or refrigerant.
The air flow can be tested by measuring the temperature drop (TD) across the coil. It should be 15F to 20F, a higher TD indicates a lack of air flow. This can be caused by dirty filters, dirty supply fan, plugged evaporator coil. This is why your AC needs to be checked every month, keep the filter clean to prevent this type of problem, if your filters have ever been negelected, this could be the cuase of the freezing. Air flow is also effected by ductwork size, and supply and return air grills.

This other cause of freezing is from the refrigerant. If the system is undercharged or the refrigerant is not being properly feed to the evaporator, then the coil temperature will drop below 32F and cause freezing. A low TD across the evaporator or a Warm suction line (big pipe at the furnace normally 55F to 60F) or a Cold liquid line (little pipe at the furnace normall 70F to 90F ) indicate a refrigerant problem and would require the services of a qualified technician.

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Old 04-05-02, 09:47 AM
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Freeze up is normally a result of refrigerant loss. Eventually you will build enough ice up that you will not be able to pass air through the coil. Get it serviced, and find the leak.

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