A/C air is cold but weak flow


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Old 05-30-18, 10:27 AM
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A/C air is cold but weak flow

Moved into my house almost a year ago. AC unit is old.. 1995 Lennox C23-26-1 but worked fine last summer. This year not so much.. currently have thermostat set at 74 but AC can not even come close. The unit has ran for 3 days straight and fluctuates with the sun.. thermostat reading 75 in morning but was at 83 when I came home at 5pm yesterday. I go over by the vents and cold air is coming out but only like 3 inches above vent. Practically no air pressure coming out of the vents. Filter was a little dirty 3 days ago when I changed it. Still nothing different as far as temperature goes. Any ideas on what the problem could be?
 
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Old 05-30-18, 11:13 AM
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If you have very little airflow coming out of the vents, the evaporator coil is likely frozen, blocking most of the airflow. A frozen evaporator coil is often caused by restricted airflow (dirty filter) or low refrigerant. I would suggest turning off the A/C and running just the fan. This should speed up the process of melting the ice. Once normal airflow returns, try running the A/C again. If it freezes up again (low airflow), you're likely low on refrigerant (you have a leak) and it's time to call an HVAC technician.
 
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Old 05-30-18, 11:37 AM
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Thank you for your help. How long does it usually take to thaw out the evap coil? When I changed the filter I had ice on larger of 2 pipes running from inside/outside unit(suction line?) I ran the fan with no cooling for 2 hours and the big line no longer had ice on it and still doesn't at this time. Would the evap coil take longer to thaw? Also I have been browsing the forums and I read the small thin line should be warm/semi hot to touch. Mine is like room temperature. I dunno if this information is useful.
 
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Old 05-30-18, 11:43 AM
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A lot of things can cause low airflow.
What tonnage is the A/C?
Larger tonnage tend to have poor airflow due to improper design...
 
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Old 05-30-18, 11:48 AM
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Originally Posted by Ecubed View Post
Thank you for your help. How long does it usually take to thaw out the evap coil?
It could take as long as 12 hours for ice on the evaporator coil to fully melt. I would try running the fan only for ~12 hours and then check the airflow. If the airflow is much stronger, then the evaporator coil was frozen and that was what was restricting the airflow.
 
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Old 05-30-18, 04:21 PM
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Not sure where to look for the tonnage. As far as Bob's advice, I just got home turned cooling off and fan on. We will see results after 12 hours when I turn it on in the morning.
 
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Old 05-30-18, 04:28 PM
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You can post the model number for the condenser and the air handler and we can look them up.

You posted a model number in your first post. That is a Lennox 2 ton coil/airhandler.
 
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Old 05-30-18, 09:08 PM
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some pics of unit

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Last edited by PJmax; 05-30-18 at 09:41 PM. Reason: added pics from links
 

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