Odd Central Air Problem: What Should I Check Next?


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Old 06-02-13, 04:18 PM
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Odd Central Air Problem: What Should I Check Next?

Hello,
I have an apartment where the A/C isn't working correctly:
* It doesn't cool to temps set under 78, but it does cool to 78.
* On very hot days, the indoor temp will go up to over 80 when system is on.
* It'll even shut off after a few hours of trying to cool.
* I see condensation dipping out of the outdoor drain tubing.
* I see condensation in the attic on the insulted tubing too.
* Oddly, the air flow through the ducting one day is decent, but the next is almost nothing.
* Unit is only about 7 years old.
* It cooled sufficiently for those 7 years (unless the tenant never cared it didn't).
* The air handler is in the attic with the ducting.

WHAT I CHECKED:
* I checked 75% of the ducting (still looks pristine) for air leaks in the attic and didn't feel anything bad.
* I looked into the return in the ceiling and it is pristine inside the flex ducting.
* Both return filters are basically new and clean.

I'm going into the attic tomorrow morning and going to:
* Open the air handler to see if the evaporator is covered with dust.

QUESTIONS:
(1) Is there anything else I can check into while I'm up there?
(2) What else could it be: a bad compressor? Clogged Evaporator? A leak?
(3) Why would air flow thru the ducting be good one day and almost nothing the next?

Thanks a lot! -Tony
 
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Old 06-02-13, 04:28 PM
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If you are renting then you should call your landlord.
 
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Old 06-02-13, 04:29 PM
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I *AM* the landlord... :-)
 
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Old 06-02-13, 04:58 PM
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It could be icing up due to a dirty indoor coil a lack of refrigerant.

Take a digital "Meat Thermometer" and measure the temperature of the air entering and leaving the evaporator coil while it is cooling.

You want an 18 to 21 degree drop in temperature. Higher would point to low airflow and lower would point to low charge.

If the air entering the evaporator coil is much higher than the air entering the filter grill, you want to check for return air duct leaks.
 
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Old 06-02-13, 05:02 PM
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Thanks for the reply:

I forgot to mention in my original posting: I have a laser thermometer and the air coming out of the ceiling vent was 10 degrees cooler than the intake/return temp.

How would I check the air temp entering the evaporator coil? If I open the unit in the hot attic, that hot air will mix in.
-Tony
 
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Old 06-02-13, 09:52 PM
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A laser thermometer will not accurately measure air temperature.

Drill a small hole in the duct and stab your digital meat thermometer into the duct to get temperature readings.
 
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Old 06-07-13, 09:28 AM
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Houston, you were right. I called a tech and there's a leak at the indoor coil.

Also, the answer to my question on why the air flow in the apartment was strong one day and almost none the next is: that icing up blocks air flow.

Thank you. -Tony
 
 

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