AC running constantly

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Old 07-07-10, 07:31 PM
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AC running constantly

Here in Connecticut we have had very hot weather the past couple of days. The thermostat is set to 76 degrees (78 is too hot for us) but the system has a hard time keeping the house 76 degrees. The thermostat says the house is 78-80 degrees and the ac has been running non-stop the past couple of days (only reaches set temp at night and morning).
I'm wondering if this is normal since the weather has been warmer than usual. I replaced the filter but can't tell if the vents are blowing more air.
The thing is that the evaporator hasn't been cleaned for as long as we've lived here (5 years, house is 11 years old) so I'm wondering if it just needs a thorough cleaning. I know that the previous home owners used those crappy blue fiberglass filters that probably allowed dust to accumulate in the evaporator. The air blowing out of the vents is somewhat weak. The ac has no problem maintaining the temperature when it's cooler outside, it just started when it got very hot.
Can a dirty evaporator / blower fan be causing the ac to run all day? The condenser is regularly cleaned, I'm not sure how to go about cleaning the evaporator, though I am handy. Thank you!
 
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Old 07-07-10, 10:56 PM
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Dirty evaporator affect the AC performance a lot. You can Google 'how to clean ac evaporator', you will find tons of threads...
 
  #3  
Old 07-08-10, 12:50 AM
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We can rule out a freon leak if the air coming out the register feels COLD.
 
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Old 07-08-10, 07:41 AM
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Yes, the air coming out of the registers is cold. Never felt warm air come out of them.

Right now in the morning, it has no problem maintaining the temperature and cycling on and off about two times per hour. I'm also wondering why the air coming out of the registers is rather weak - most houses I've been to have very strong airflow from the vents. Could the blower fan also be dirty / set to a low speed? This is just an AC unit.

I'll have to wait until the temperature cools down as the unit is in the attic.

Thank you
 
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Old 07-08-10, 05:30 PM
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Are you in a single family home or a townhouse/condo?
 
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Old 07-08-10, 09:19 PM
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Single family home - raised ranch - we don't have a basement.
 
  #7  
Old 07-08-10, 09:38 PM
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Ask yourself 2 questions. What is the temp split (temp difference between the cold air and the return air) ? Do you feel the cold air blow to your face from 8 feet away (from at least one or two of your vents) ?
 
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Old 07-08-10, 10:04 PM
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I have no way of figuring out the temperature split right now. I will as soon as I can. As for the second question, yes I can feel cold air blowing 8 feet from two vents (kitchen and living room, closest to the air handler), though I still feel as if the airflow is weak.

If I'm correct, shouldn't there be a cover on the right side of the air handler to keep the air going straight to the duct?
http://img149.imageshack.us/img149/2093/img1072fo3.jpg
I don't know how I would go about covering that hole unless I tape a sheet of metal over the hole.

Also, how would I be able to adjust the speed of the blower if I would need to?

I'm planning on cleaning the evaporator coil as soon as I get coil cleaner from Home Depot. The previous home owners that built the house used cheap fiberglass filters, which I'm sure didn't do any good for the evaporator coil.
 
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Old 07-09-10, 10:16 AM
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What do you mean to cover the right side of air handler ?? Are you saying the whole panel is gone ? It is wide open ?? No wonder you have problem. the air handler needs to be closed completely and sealed real real tight(no air leak at all). So, get a sheet of metal(put some insulation inside) and cover it. From the picture, I can see your coil is not dirty at all, but I can not see the air incoming side of the fin, so clean it anyway if you can. be careful not damage those tiny pipes. Don't worry about the fan speed yet, get this big hole covered first. may be this will fix the whole thing..
 
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Old 07-09-10, 10:34 AM
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WTF! Where did that cover go! Maybe you can get a replacement from the manufacturer. That's definitely the problem.

Maybe you can fashion something out of plywood while you wait for the part to come in or whatever.
 
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Old 07-09-10, 11:15 AM
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No expert (as the guys here know) but it seems like there should be a small cover on the right, inside of the main cover?? I see what appear to be screw holes...but maybe thats for a different application? Can't tell from the perspective in the pic....
 
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Old 07-09-10, 12:05 PM
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I just reread the OP's post. He is refering to that small cover on the right and not the large cover for the side.

I would agree that something should be there. I think Home Depot sells pieces of sheet metal in the aisle where they have the ductwork. I would try to fashion something myself with that and tape the seams with foil tape. I think that will make a big difference.
 
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Old 07-09-10, 03:03 PM
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No not the whole entire cover, haha the small one on the right! I remember reading somewhere that that's where the strip heaters are supposed to go or something like that.., but that there's supposed to be a cover there (hence the holes for screws? I'll have to buy that when I go buy the coil spray. The picture is about two years old fyi and the air handler has probably been like that since installation. The house can usually hold the temperature but maybe it would help have more airflow and help during these hot days.
I'll bet that the incoming side of the fins are dirty because the previous home owners used the blue fiberglass filters.
Thank you so much!
 
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Old 07-11-10, 10:04 AM
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It may just be that 100+ degrees is too hot for your unit to keep up with. I know my unit is undersized a bit and has problems when it gets over 90. It will run constantly and the inside temp starts to climb probably when it gets to like 93. High 90's and above is unusually high for our area, so I wouldn't worry too much if adding the cover doesn't solve your problem.
 
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Old 07-11-10, 10:11 AM
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throw the restrictive return air filter away that you have paid the big bucks for and put a nice blue cheapo free flowing return filter on there and live happy. The filters (believe it or not) are for equipment protection and the blue ones work well.The silly allergy catching things are too restrictive for the average system and cause nothing but problems. MERV 5 or less is what you need unless you swap out your return grilles to enormous sizes to make up for reduced airflow through the restrictive filters.
 
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Old 07-12-10, 07:36 AM
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I did in fact notice that the airflow is much better without the pleated filter. However, I'm worried about the cheap filters allowing the evaporator to get dirty, although I still don't know how dirty it is since I haven't been able to clean it out yet. I'll have to pick up a coil cleaner spray at Home Depot that's self rinsing. Does this look any good?

AC-Safe Foam Coil Cleaner - AC-920 at The Home Depot

Thank you!
 
  #17  
Old 07-12-10, 05:36 PM
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Originally Posted by Former Member View Post
throw the restrictive return air filter away that you have paid the big bucks for and put a nice blue cheapo free flowing return filter on there and live happy. The filters (believe it or not) are for equipment protection and the blue ones work well.The silly allergy catching things are too restrictive for the average system and cause nothing but problems. MERV 5 or less is what you need unless you swap out your return grilles to enormous sizes to make up for reduced airflow through the restrictive filters.
Maybe that's part of the problem on my system. I have a huge pleated filter on there. Maybe I should try a cheapo in the old slot and see how it works.
 
  #18  
Old 07-14-10, 07:06 PM
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So I decided to cover up the hole with a piece of sheet metal. While I was cleaning the evaporator coil I decided to turn the fan on to see if a lot of air came out of the hole. To my surprise, the amount of air that came out was alarming, no wonder I had low airflow around the house!
I covered it up, closed the air handler and turned the fan on. WOW, what an improvement! The registers closest to the air handler aren't much better than they were before, but the ones further away have much stronger airflow now! You can actually feel the air coming out of the registers. Now the kitchen can actually cool down instead of always being hot because of the skylight.
The evaporator coil wasn't all that dirty - however, the water coming from the coils after spraying them told me otherwise.
Here are some pictures

Before:
http://img149.imageshack.us/img149/2093/img1072fo3.jpg

After:
http://img22.imageshack.us/img22/4089/img2852e.jpg

http://img651.imageshack.us/img651/4808/img2853m.jpg

http://img715.imageshack.us/img715/1102/img2855n.jpg

I closed the evaporator coil side up before I could actually take pictures of it.

Thank you
 
  #19  
Old 07-20-10, 08:31 AM
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Arrow Check the blower wheel blades for lint...

Originally Posted by dk489 View Post
Here in Connecticut we have had very hot weather the past couple of days. The thermostat is set to 76 degrees (78 is too hot for us) but the system has a hard time keeping the house 76 degrees. The thermostat says the house is 78-80 degrees and the ac has been running non-stop the past couple of days (only reaches set temp at night and morning).
I'm wondering if this is normal since the weather has been warmer than usual. I replaced the filter but can't tell if the vents are blowing more air.
The thing is that the evaporator hasn't been cleaned for as long as we've lived here (5 years, house is 11 years old) so I'm wondering if it just needs a thorough cleaning. I know that the previous home owners used those crappy blue fiberglass filters that probably allowed dust to accumulate in the evaporator.
The air blowing out of the vents is somewhat weak. The ac has no problem maintaining the temperature when it's cooler outside, it just started when it got very hot.
Can a dirty evaporator / blower fan be causing the ac to run all day? YES!
The condenser is regularly cleaned, I'm not sure how to go about cleaning the evaporator, though I am handy. Thank you!
Check the blower wheel blades, if they are filled with lint, then the cooling coil needs professional cleaning.

Both have to be clean, & airflow needs to be at around 400-CFM per/ton of cooling.

Google search: low A/C airflow
 

Last edited by HVAC RETIRED; 07-20-10 at 08:33 AM. Reason: 400 CFM per/ton of cooling
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Old 07-20-10, 10:12 AM
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deleted,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
 
  #21  
Old 07-20-10, 10:14 PM
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Originally Posted by HVAC RETIRED View Post
Check the blower wheel blades, if they are filled with lint, then the cooling coil needs professional cleaning.

Both have to be clean, & airflow needs to be at around 400-CFM per/ton of cooling.

Google search: low A/C airflow
The cooling coil was actually pretty clean as was the blower motor. I cleaned the cooling coil anyway with coil spray from Home Depot. The blower motor had a little dust but nothing that would effect it.

The problem I had was that there was a hole in the air handler right before the duct. Someone never covered it as there were clearly screw holes for a metal cover to go over the hole. I fitted a piece of sheet metal over the hole and the airflow has improved dramatically since. The rooms on the end of the duct actually get very strong airflow going in. The returns also have much stronger airflow going up to them.
Pictures of what I fixed are above.

Thank you!
 
 

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