Air conditioning not cooling to desired temp

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Old 08-27-16, 05:49 PM
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Air conditioning not cooling to desired temp

My air condition is working normal, or at least normal for me in the six years I've lived in my house. The air coming out of the vents is cold as I expect and the air flow is the same as it's always been. However, lately during the day it does not shut off, I have it set to 73 during the day and 70 at night. At night, it usually reaches 70 and shuts off but during the day it never reaches 73, usually staying at 77. My blower motor did go out last week but it was replaced and the hvac guy said everything was fine after he fixed it. To stop rambling, is something wrong with the a/c or is this just because it's been 95+ everyday lately?
 
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Old 08-27-16, 05:53 PM
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You should do a Delta-T calculation. Measure the temperature of the air at a return that's close to the A/C evaporator coil or air handler. Likewise, measure the temperature of the air coming out of a vent that's close to the air handler. The difference in temperature between the air going in and the air coming out is the Delta-T (temperature delta). Ideally, it should be somewhere in the range of 15-20 degrees F @50% RH. The higher the better. If it's less than 15, you likely have a problem.
 
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Old 08-27-16, 09:45 PM
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Will do, what would the problem be if it is below 15?
 
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Old 08-27-16, 10:17 PM
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There could be any number of problems.

Low airflow.
Was it fine until the blower motor was just replaced?

Low on refrigerant.

Clogged air filter.
Easy to check that out.
 
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Old 08-28-16, 06:57 AM
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At 50% 'indoor' Relative Humidity the indoor delta-T should be 18 to 20F.
If the indoor humidity is higher the temp-split will be less accordingly.

Many things can reduce the indoor temp-split.
The condenser temp-split should also always be checked & compared to what it should be according to the condenser's SEER Rating & the existing operating conditions...
 
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Old 08-28-16, 05:46 PM
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No it was doing it before the motor issue and the guy said the refrigerant was fine. I changed the air filter right before posting this so that shouldn't be an issue.

As far as the air flow, I'm not sure if it's proper air flow or not. It's not bad And it's the same as it's always been, before this issue.
 
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Old 08-28-16, 06:02 PM
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So, as mentioned, let's get the delta-T first.
 
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Old 08-28-16, 07:49 PM
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Air at the return is 70, air coming out is about 52. Keep in mind I did this with a cheap thermometer.
 
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Old 08-28-16, 08:58 PM
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So your delta-T is 18 degrees which is not to bad.
I'm guessing you did this at night.

I'm thinking possible condenser fan problem.
 
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Old 08-29-16, 08:27 AM
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Here is what I am guessingAssume nothing else changed except the blower motor). 1) When the tech replaced the blower motor, he did not seal the air handler tight. 2) The blower motor is not as strong as the old one. needs to check the RPM. Also some questions, is the air handler in the attic? is the attic pretty hot during the day and cools down at night? As mentioned, did you take the delta-T at night ?
 
 

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