AC intermittently stops working


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Old 08-26-14, 07:47 PM
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AC intermittently stops working

Hi guys,
I recently moved into a small house in Florida. My GC (with the help of an AC tech) had installed an AC about 2-3 months ago. It consists of an outdoor condenser (which was new) and an indoor air handler (which was 2nd hand). Initially the AC worked great, however for the past 2 weeks I have been having problems.

Basically the AC will become less and less effective over time. The vents will have significantly lower air output along with passage of only minimally cool air. I can hear the blower making its normal noises during this, despite minimal air output.

The first time this happened, I turned the machine off, then restarted it several hours later. It then worked fine for a few days. I would have it on for about 14 hrs a day. The problem started again about a week later. At that time I looked at the air handler, which appeared to be slowly dripping liquid. I did some Googling, which made me think the problem could be frozen coils. As far as why the coils could be frozen, possible causes (according to random websites) included:
1. Poor air flow - Could be due to dirty filter, dirty coils on condenser or air handler, problems with tubing, or due to blocking an excessive amount of vents. With regards to the last point, I have 6 vents in the house and I had blocked all but 2-3 a few weeks before the problem started.
2. Low freon/freon leak

At that point I kept the AC off, left the AC's fan on, changed the filter, and let the water drip out overnight. The following morning when I tried the AC, it worked fairly well, though not at 100%.

I called my GC (who admittedly doesn't know that much about ACs). He looked inside the air handler and at the condenser outside, and said everything seemed to be working OK, and if problems persisted, that he could call his AC guy.

Since then, I keep getting the same problem, though without the water dripping from the AC. It has progressed to the point where it occurs on a daily basis-- the AC will become less and less effective, I will turn it off and leave the fans on, and after a few hours I will turn it back on and it seems to do an OK (though still subpar) cooling job.

Today when it happened, I looked at the AC and noticed that the filter was deformed and sort of bowed in toward the air handler. When I pulled the filter out, I looked inside (from below) and I think the coils were frosted.

As a side note (probably unrelated), the air coming to my bedroom has always been quite forceful. I assume it is the first vent off the AC. But if the door is ajar, the AC will always slam it shut. I am not sure if this means the system would be predisposed to developing problems after closing some of the vents.

Here are some pictures:

1. Indoor air handler
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2. Coils (frosted, I think). Shot from below air handler, where filter normally goes.
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3. Side view of deformed filter.
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I am going to have an HVAC guy come and check the system out, but I was wondering what you guys think could be the problem.

Also, please pardon my ignorance on the subject of ACs.
Thank you for any assistance,
Sweating
 
  #2  
Old 08-26-14, 08:08 PM
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I have 6 vents in the house and I had blocked all but 2-3 a few weeks before the problem started
Six vents isn't a lot and to block off 3-4 of them is not good. You need airflow thru the coil and thru the house.

The A/C tech should check the static pressure in the ductwork.

Usually a dirty or wet filter will get deformed like that. If the air can't get thru the filter it pull like that. When the filter is out..... is the airflow better/normal ?
 
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Old 08-26-14, 08:19 PM
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You definitely need to open all of the discharge vents in the house. Also make sure the return air vents are not blocked off or restricted. An HVAC system has to breathe and have adequate air flowing across the evaporator coil or it will more than likely ice up. Make sure you turn the system off or use fan only long enough to allow the ice to completely melt before turning it back on to a/c mode.Try that and see if the increased air flow corrects your problem. The system is ineffective because the iced up coil is blocking air flow.
 
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Old 08-27-14, 03:15 PM
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Thanks for all of your input. Based on what you guys said, I am guessing the filter is warped because of water damage (from when the AC defrosts and water drips down to the filter).

I opened all of the vents in the house before I went to work, turned the fan on, and left the AC off. When the girlfriend came home (about 3.5 hrs later), she turned the AC on again. When I got home (about 7.5 hrs after she got home), the AC was barely putting out air again. The coils were frozen, as was the pipe that carries the cold freon from outside.

I tried removing the filter, but there is no significant change in the air flow (though this may be because it is already frozen). I will try defrosting the AC for longer.

If the problem continues to occur even with all of the vents open, new filter, clean blower and coils, etc. does that imply the problem is one of low freon as opposed to poor air flow?

Thanks again for your help,
Sweating
 
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Old 08-27-14, 07:41 PM
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Yes, it definitely needs to have the freon level checked. Also, the evaporator coil could be clogged up and needs to be properly cleaned.
 
 

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