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tigersfan1989
LSU Fan
Member since Oct 2018
900 posts

Is there something wrong with my ac unit?
So in the afternoon my ac will be set at 72 but the actual temp of the house is 77. I looked at the thermostat last night at 9 and it showed 76. When I woke up this morning it was much cooler and showed 71. This has been happening more often lately but I’m thinking the fact it does finally cool down to 71 means there’s nothing wrong. Do I need to get an ac person out here or would I be wasting my money?


TBubba
LSU Fan
Not sure
Member since Sep 2007
954 posts

re: Is there something wrong with my ac unit?
Insulation
Humidity
Sunlight heating up windows



When it reaches 85 plus with high humidity and sunlight I close all curtains and keep all ceiling fans blowing. Definitely helps.


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60
Simon Gruber
Houston Astros Fan
Member since Mar 2017
564 posts

re: Is there something wrong with my ac unit?
It’s probably low on Freon. Get someone to charge it up and run dye in it to see if you have a leak.


tigersfan1989
LSU Fan
Member since Oct 2018
900 posts

re: Is there something wrong with my ac unit?
Not sure if this adds any value but house is 10 years old and it’s a Lennox unit


ItzMe1972
Member since Dec 2013
5763 posts
 Online 

re: Is there something wrong with my ac unit?
Filter clean?

Have you washed the coils on the outside unit?

Wouldn't hurt to have a service call to see if it's cooling as well as possible.


tigersfan1989
LSU Fan
Member since Oct 2018
900 posts

re: Is there something wrong with my ac unit?
I had it cleaned and serviced like 3 years ago. I figured it was kind of over kill to get it done every year. Thinking I’ll call to get cleaned and serviced like you said and go from there.


TU Rob
Atlanta Braves Fan
Birmingham
Member since Nov 2008
11601 posts

re: Is there something wrong with my ac unit?
quote:

I figured it was kind of over kill to get it done every year.


Maybe not every year, but I wouldn't go 3 years. Simple cleaning of the outside unit you can do yourself twice a year, but have someone come do a clean and checkup. Might just need a pound or so of refrigerant.

Also you mentioned Lennox, we finally replaced our ancient one last fall. It was a Lennox from 2004 I think. It needed R22 Freon about every other year, so I managed to keep it running maybe 3-4 more years before it died and I had to replace. Now I wish I had done it sooner. Went with a 4 ton Rheem and it gets the house downright cold when I set it low enough.


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DrewTheEngineer
LSU Fan
Baton Rouge (Oak Hills)
Member since Jun 2006
791 posts

re: Is there something wrong with my ac unit?
I'm in the same boat as you ...

I set my thermostat at 74 during the day. By 1:00 yesterday, the internal temperature of my house was 75 (measured with a portable thermometer). By 5:00 it was 77. Clearly the AC can not keep up, and it actually never shut off from 11AM to 11PM. Last year I never recall this happening unless the outside temperature got over 95 degrees, and yesterday I believe it peaked at 90.

So, first off, I've got an AC guy (hopefully) coming tomorrow. Second, I have an insulation guy coming next week to blow 9" of cellulose on top of what insulation I do have (which is not much by todays standards... my house was built in 1959).

Things you can check for now ... replace the filter if it's dirty and hose off the coils around your compressor to make sure they aren't covered with dust, grass clippings, etc.

ETA:
Also, if you have a portable thermometer, check the air coming out of the vents in your ceiling. It should be around 15 or degrees cooler than the air going into your return air duct. In my case, it's barely 10 degrees cooler.
This post was edited on 6/10 at 8:49 am


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20
Hamma1122
Member since Sep 2016
13651 posts

re: Is there something wrong with my ac unit?
Low on Freon


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20
WPBTiger
USA Fan
Parts Unknown
Member since Nov 2011
22591 posts

re: Is there something wrong with my ac unit?
quote:

It’s probably low on Freon.


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USA
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slapahoe
USA Fan
USA
Member since Sep 2009
7284 posts

re: Is there something wrong with my ac unit?
freon low


Dawgfanman
Georgia Fan
Member since Jun 2015
13108 posts

re: Is there something wrong with my ac unit?
Low Freon. Dirty filter. Both. You sure it’s isnt freezing up?


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tigersfan1989
LSU Fan
Member since Oct 2018
900 posts

re: Is there something wrong with my ac unit?
So is my best route to just call for a clean and service and they will prob tell me I need Freon in the process? I know it’s automatic $100 for a call out if I just tell them it’s not cooling properly so I mind as well get something for that $100 call out


CrawDude
LSU Fan
Baton Rouge
Member since Apr 2019
3125 posts

re: Is there something wrong with my ac unit?
As others have recommended, have a HVAC tech clean the outside condensing unit, indoor evaporator coil and check refrigerant pressures, superheat and subcool. The way you describe it, it does sound to be a little low on refrigerant (“Freon”). Though a sealed system, it would not be uncommon for a 10 year old unit to lose some refrigerant from a small, slow leak.

Check and change your air filter regularly - air flow is extremely important in proper HVAC operation. If you have 1 inch thick filter located in the return plenum grate, be sure it’s low MERV filter, like MERV 4 fiberglass spun filter (a cheap filter) - high MERV 1 inch pleated filters can restrict air flow to the evaporator coil reducing HVAC performance. The filter’s function is to protect the HVAC equipment, not improve air quality for human health.

Lastly, just for your general knowledge, if the HVAC if properly sized, and not over-sized (they are rarely undersized) it should be able to maintain an indoor temperature of 75 F at design temperature, outdoor design temperature being 92 F for south LA. At outdoor temperatures exceeding 92 F your indoor air temperature can exceed 75 F in mid to late afternoon in a properly functioning HVAC. Plus your HVAC could be expected run non-stop from 11 am to 7/8 pm at outdoor temperatures at or above design temperature (92 F or higher) until outdoor temperatures cool.


tigersfan1989
LSU Fan
Member since Oct 2018
900 posts

re: Is there something wrong with my ac unit?
So I actually have two spots on my unit for air filters. One is the standard 1 inch filter at the air intake in the ceiling. The other spot is in the attic right next to the air return part of the unit which has a door that opens and uses like a 6 inch filter. I’ve been told by other techs that come out that I only need to put a filter in one of these spots as two filters are not needed and will stress the unit out too much. So I chose the 6 inch filter bc I only have to change it every 6 months. I changed it in March so it should still be fine. I’m thinking maybe I should use the 1 inch filters instead it just seems like a 6 inch filter is way too much


CrawDude
LSU Fan
Baton Rouge
Member since Apr 2019
3125 posts

re: Is there something wrong with my ac unit?
quote:

So is my best route to just call for a clean and service and they will prob tell me I need Freon in the process? I know it’s automatic $100 for a call out if I just tell them it’s not cooling properly so I mind as well get something for that $100 call out


Yes do that - request a cleaning service plus a refrigerant check as you suspect your unit might be a little low on refrigerant but tell them that when you make the call. Part of the cleaning service is to check refrigerant pressures, superheat and subcool. The usual charge is about $80 to 100 for that. And of course if you need refrigerant they’ll be a charge for that. If you have R-22 refrigerant system and need some expect to pay a minimum of $100 per pound.


tigersfan1989
LSU Fan
Member since Oct 2018
900 posts

re: Is there something wrong with my ac unit?
Ok sounds like a plan thanks for the help. It seems like any ac call out you can generally expect to shell out a couple hundred at minimum


footballdude
LSU Fan
BR
Member since Sep 2010
727 posts

re: Is there something wrong with my ac unit?
quote:

I had it cleaned and serviced like 3 years ago


Get it serviced every year.



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20
TU Rob
Atlanta Braves Fan
Birmingham
Member since Nov 2008
11601 posts

re: Is there something wrong with my ac unit?
quote:

If you have R-22 refrigerant system and need some expect to pay a minimum of $100 per pound.


When I had mine serviced last, it was around $90 for the first pound, and my guy gives repeat customers a little discount for additional pounds. It needed around 2 lbs and my total for that was $155 plus the $90 service call. Of course this was a year ago according to my emails, and prices have probably continued to go up.


CrawDude
LSU Fan
Baton Rouge
Member since Apr 2019
3125 posts

re: Is there something wrong with my ac unit?
quote:

So I actually have two spots on my unit for air filters. One is the standard 1 inch filter at the air intake in the ceiling. The other spot is in the attic right next to the air return part of the unit which has a door that opens and uses like a 6 inch filter. I’ve been told by other techs that come out that I only need to put a filter in one of these spots as two filters are not needed and will stress the unit out too much. So I chose the 6 inch filter bc I only have to change it every 6 months. I changed it in March so it should still be fine. I’m thinking maybe I should use the 1 inch filters instead it just seems like a 6 inch filter is way too much


The single 6 inch filter is fine - if you changed it March all that should be good, and you can certainly use a higher MERV filter for 6 inches. Even then I’ve read where many HVAC techs don’t like those filters exceeding a MERV rating of 8 - again to insure proper air flow to the evaporator coil.

Basically as long as the single filter, or even 2 filters, doesn’t increase the total external static pressure above a certain level, usually 0.5 inches of water column (for older systems), the air flow to the system should be fine. Static pressure is a measure of resistance to air flow, and is analogous to measuring blood pressure of person. The return air static pressure and supply air static pressure are measured and added to get the total. Unfortunately static pressure seems to seldom or rarely done by many HVAC techs when trouble shooting and I’m not sure why as it is a simple and quick test usually taking no more than 5 to 10 minutes, and it’s an important HVAC diagnostic tool.


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