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Old 07-10-2011, 11:36 PM   #1
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AC doesn't cool during the day


1900 square feet house
10 year old house
10 foot ceilings throughout
4 ton Goodman unit
inside Goodman unit is in the attic
1 ceiling 20x25 return vent
9 supply out vents
Sorry if my nomenclature is a bit off.

During the night I have about 20 degree diff between filter and cool vents therefore it is working as designed. It feels great inside.
Although during the day it is only about a 10 degree difference. Right now it is in the mid 90s outside during the day with a good bit of humidity. I can not get inside cooler than 85 degrees.


All vents and filters have been cleaned.
Coils inside and out have been cleaned.
Ducts have no leaks.
AC has freon in the system. It cools down fine at night.



Any ideas?
Thanks for the responses,
Brad

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Old 07-11-2011, 12:08 AM   #2
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AC doesn't cool during the day


Takes time to remove all heat. Won't turn off your AC and set to 75F one day and night.

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Old 07-11-2011, 12:12 AM   #3
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AC doesn't cool during the day


Unfortunately it is more serious than that. I have had doors and windows shut for weeks with the exception of walking in and out.
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Old 07-11-2011, 05:24 AM   #4
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AC doesn't cool during the day


9 supplies for a 4 ton? Must be very big supplies. At that number, 8 of them should be 8" diameter minimum and a slightly smaller one for the bathroom. And that return is sized more for a 2 ton then a 4 ton.

You need to increase your return(add another one the same size or larger) and add a few supplies. Then the charge can be checked after that. Its probably slightly over charged to keep it from freezing up.


What size is the return duct, may also b e too small.
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Old 07-11-2011, 06:36 AM   #5
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AC doesn't cool during the day


how's that liquid line coming from the condenser warm is good hot to the touch in the middle of the day is a blocked condenser between the coils
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Old 07-11-2011, 09:24 AM   #6
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AC doesn't cool during the day


The question is 20 degree split at night, but only 10 during the day. Why ? The only reason that I can come up is the air handler/duct insulation in the attic may have some problem. not enough insualtion, or leak..
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Old 07-11-2011, 04:58 PM   #7
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AC doesn't cool during the day


Quote:
Originally Posted by clocert View Post
The question is 20 degree split at night, but only 10 during the day. Why ? The only reason that I can come up is the air handler/duct insulation in the attic may have some problem. not enough insualtion, or leak..
An over charged system on an under sized duct system can cause this.
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Old 07-12-2011, 12:52 AM   #8
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Originally Posted by beenthere View Post
9 supplies for a 4 ton? Must be very big supplies. At that number, 8 of them should be 8" diameter minimum and a slightly smaller one for the bathroom. And that return is sized more for a 2 ton then a 4 ton.

You need to increase your return(add another one the same size or larger) and add a few supplies. Then the charge can be checked after that. Its probably slightly over charged to keep it from freezing up.


What size is the return duct, may also b e too small.
I can add another return on the other side of the house, but how would I go about putting it inline with the current supply?

thanks
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Old 07-12-2011, 12:53 AM   #9
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AC doesn't cool during the day


Quote:
Originally Posted by biggles View Post
how's that liquid line coming from the condenser warm is good hot to the touch in the middle of the day is a blocked condenser between the coils
liquid line is warm
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Old 07-12-2011, 12:55 AM   #10
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AC doesn't cool during the day


Quote:
Originally Posted by clocert View Post
The question is 20 degree split at night, but only 10 during the day. Why ? The only reason that I can come up is the air handler/duct insulation in the attic may have some problem. not enough insualtion, or leak..
I have a good amount of insulation throughout the attic, but I am concerned that the plenum and return supply are flexboard.
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Old 07-12-2011, 12:56 AM   #11
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AC doesn't cool during the day


Quote:
Originally Posted by beenthere View Post
An over charged system on an under sized duct system can cause this.
Well short of getting a tech out, I am not sure if I can verify this.
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Old 07-12-2011, 01:40 AM   #12
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AC doesn't cool during the day


I still think your problem is caused by the hot attic if your plenum and duct work in the attic are not well insulated or tightly sealed. Try to check the temp split in the morning hours when the attic is not hot yet, you may get a higher temp split. (this is simple physics, you have a heat source during the day, but not at night)
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Old 07-12-2011, 02:15 PM   #13
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Originally Posted by clocert View Post
I still think your problem is caused by the hot attic if your plenum and duct work in the attic are not well insulated or tightly sealed. Try to check the temp split in the morning hours when the attic is not hot yet, you may get a higher temp split. (this is simple physics, you have a heat source during the day, but not at night)
Thanks.
I will try the temp split in the morning.
If my 4 ton wasn't big enough for my house would I have the same symptoms?
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Old 07-12-2011, 03:43 PM   #14
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AC doesn't cool during the day


This has nothing to do with the size of the system. One more check you can do, during a hot day, measure the air temp right before the blower and about 1 foot after the A-coil, the difference will be your real temp split, this will eliminate all other factors. And also measure register air temp in the house and return air temp in the house. with those 4 numbers, you should see something.
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Old 07-12-2011, 05:04 PM   #15
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Quote:
Originally Posted by clocert View Post
This has nothing to do with the size of the system. One more check you can do, during a hot day, measure the air temp right before the blower and about 1 foot after the A-coil, the difference will be your real temp split, this will eliminate all other factors. And also measure register air temp in the house and return air temp in the house. with those 4 numbers, you should see something.
Maybe I am not seeing this properly.
If I take the temp right after the evap coil that requires me to open it up allowing all the hot attic air inline to give me a false reading.

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