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Old 05-11-2011, 10:21 PM   #1
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Default SOLVED - How cold is my home AC supposed to be? (with pics)

My wife says the house is too hot and the AC has been running all day. I've been outside working on the Geo Metro all day so I have no idea. I didn't get to look at anything outside but I stuck a meat thermometer in one of the registers and it says 66 degrees. I figure that is probably +/- a few degrees due to the cheap thermometer. Does this sound right?

Last edited by rmcelwee; 05-12-2011 at 10:28 AM.
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Old 05-11-2011, 11:00 PM   #2
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I think it should be a bit colder than that, but I'm no expert.
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Old 05-11-2011, 11:11 PM   #3
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The air should be in the high 30s to low 40s coming out of the air handler. Registers will always vary due to duct length and insulation.
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Old 05-12-2011, 12:19 AM   #4
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I was told before I bought my new system that the difference in temp if measured at the intake in the house and at the vent should be no less than 13 degrees. 20 is more like it.

FYI: My new Carrier infinity system is baller.
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Old 05-12-2011, 12:47 AM   #5
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I've been meaning to go into the attic and clean the coils for the last couple of years (system is 8 years old). I guess I'm finally going to have to do it. What a pain in the *** this is going to be.
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Old 05-12-2011, 12:50 AM   #6
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I just checked the air temperatures from my AC. The air coming from the floor vent is 51.2 degrees, the air entering the air handler is 69.4 degrees, and the outside temperature is 68.5 degrees.
If your AC is running all day, there are 3 things that come to mind that could be to blame
1. system low on refrigerant, or coils plugged (condenser or evaporator)
2. inadequate insulation in the house
3. system undersized for the house

My house suffers from both number 2 & 3
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Old 05-12-2011, 03:01 AM   #7
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0200 hrs and the AC is still running (yeah, I know I should have killed it before now). I went into the attic, opened it up and found that the coils were one large block of ice. I'll let it melt over the next few hours and see what the coils look like in the morning. Of course, I'm hot, sweaty, and pissed now so I doubt if I get any sleep.
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Old 05-12-2011, 03:31 AM   #8
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I know absolutely nothing about aircon. Well, I understand the underlying thermodynamic principles perfectly well, but have zero first-hand experience in servicing the systems, short of replacing the occasional fan motor.

However, I do recall living in an apartment years ago in Florida, wherein the first day I moved in, I found the A/C to be exhibiting precisely the same symptoms as yours- insufficient cooling performance despite continual operation, and an evaporator coil that was a solid block of ice.

The maintenance fellow came over and either added refrigerant to, or removed refrigerant from the system, and this relieved the problem.
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Old 05-12-2011, 03:53 AM   #9
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One thing about Charleston SC, we have 100% humidity here. I'm hoping that is the cause and not low freon. If that isn't it, I hope it is low freon and not a problem with the coils.

Something to be aware of if you do not know anything about AC. There is a large capacitor in the unit outside (we have a split unit with the evaporator in the attic). These caps go bad and will keep your unit from firing up (I think the correct terminology is starter capacitor). If your system is more than 5 or 6 years old it is worth it to look at the specs and order a cheap on online. The AC guy will burn you for a couple hundred $$$ when this thing goes out ($15 part). You can tell when it is bad (I'm sure Joe knows this but I am saying it for the others) because the top will swell up.

Kind of hard to see here but the top is not flat on this one:

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Old 05-12-2011, 04:48 AM   #10
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Quote:
Originally Posted by rmcelwee View Post
One thing about Charleston SC, we have 100% humidity here. I'm hoping that is the cause and not low freon. If that isn't it, I hope it is low freon and not a problem with the coils.

Something to be aware of if you do not know anything about AC. There is a large capacitor in the unit outside (we have a split unit with the evaporator in the attic). These caps go bad and will keep your unit from firing up (I think the correct terminology is starter capacitor). If your system is more than 5 or 6 years old it is worth it to look at the specs and order a cheap on online. The AC guy will burn you for a couple hundred $$$ when this thing goes out ($15 part). You can tell when it is bad (I'm sure Joe knows this but I am saying it for the others) because the top will swell up.

Kind of hard to see here but the top is not flat on this one:

Stick your tongue on the posts! Of course you won't be able to reply to let us know you did it. Even a small capacitor in a TV will nearly stop your heart, one of those would kill you 10 times over I'm sure. Electricity scares me, or I guess I have a strong respect for it, as everyone should.
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Old 05-12-2011, 09:39 AM   #11
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Evaporator freezing up can indicate low refrigerant. And they haven't used Freon for a few years. It isn't particularly difficult to add but requires gauges and an understanding of what those gauges are telling you. The good news is that refrigerant itself is cheap. The bad news is that service calls are not and they will mark up the refrigerant a lot. More bad news is that you have a leak and that the A/C company may try to royally screw you on what is actually leaking and sell you a major component when you have a leaky joint at a fitting. If the estimate is over $250 after the A/C tech gets there, I would get a second quote.

Your home A/C system shouldn't see all of the humidity that exists outdoors because it is a closed system. It will continue to dehumidify your house as it runs and will get more efficient as the humidity is removed.

Good luck.
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Old 05-12-2011, 09:54 AM   #12
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I was just about to start a thread to see if anyone ehere knows how to clean the evaporator coils. From the information I can find on the interwebs, it seems that most use simple green and a nylon brush to clean it.

I noticed that the air wasn't coming out of my vents as hard as it used to , so I checked the coil and sure enough it had some crap built up on it.
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Old 05-12-2011, 10:04 AM   #13
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the manual doesnt say what to expect at the outlet as far as temp...only all the pressure readings of the system.
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Old 05-12-2011, 10:27 AM   #14
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The AC is once again working. It was only blowing 66 degrees again but there is a huge difference in the volume of the air blowing through it. It looks like there is quite a bit of work to do in order to get to the inside of the A-coil to clean it but I probably need to do it at sometime. Also, I can see a very rusty run capacitor on the side of the fan. I'll be looking to buy a replacement for this thing soon since I don't trust it.


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Old 05-12-2011, 10:35 AM   #15
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Quote:
Originally Posted by sixshooter View Post
And they haven't used Freon for a few years. It isn't particularly difficult to add but requires gauges and an understanding of what those gauges are telling you. The good news is that refrigerant itself is cheap.
I see the side of my compressor says R22. I'm not sure if that is something I can buy or not. I do have a friend (I rarely see him) that has ties to the AC business so maybe he can score some for me.

Just so you know, if I say freon I am not meaning that is what I think it uses. I'll never call it anything other than that <G>.
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Old 05-12-2011, 01:43 PM   #16
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Old 05-12-2011, 06:04 PM   #17
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The capacitor on my A/C unit went out last year. It was bulging out the sides like it was about to explode. The system had been running all day (well only the fan really) and it was 85+ degrees inside. I have a buddy in the A/C business and he came out and fixed it likidy split. I think the capacitor was like $35. He said it's a common problem when it's REALLY hot out because the unit turns on and off so much. My **** wasn't frozen up like yours though.

Another problem I've seen is the drain getting clogged up which will cause the condensation (water) to fill up the pan which makes the saftey thingy flip and causes the system to turn off. It happened on my parents house and my same friend came out, cut the pvc pipe and litterally blew the pipe out with his mouth. He put a joint on it to attach the pvc back together and it's been working fine ever since.
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Old 05-12-2011, 06:21 PM   #18
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Quote:
Originally Posted by bluemax View Post
He said it's a common problem when it's REALLY hot out because the unit turns on and off so much.
Which is why I like the "inverter" type A/C units. They work all the time, rather than going on/off above/below the temperature threshold.
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Old 05-13-2011, 10:54 PM   #19
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I worked all day but my wife was home. I called an AC guy (related to my boss - thought this would keep me from getting ripped off or my wife from getting raped) and had him go to the house to check it out. He added 3 pounds of freon, replaced some valve step caps (not sure what they are called but same sort of thing that is on your tires), inspected both units. In the end it cost me $140.

1) A cap was missing (these things have rubber o-rings in them and could stop a leak)

2) Freon was 3 pounds low (not much at all but enough to make the system inefficient). Low freon causes icing.

3) Said our new fancy (think K&N) filter was horrible (restrictive) and we should go back to the regular type. Lack of airflow causes icing.

4) Said I needed to clean the outside unit coils a bit (I knew that - they aren't really bad but I will do it anyway with some real cleaner)

5) The air was blowing out 66 and now it blows out at 56 degrees (not 100% sure those numbers are correct but it is close to that)

I'm tight but I think the $140 was well worth it.
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Old 05-16-2011, 11:06 AM   #20
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He's right. Low refrigerant causes icing.
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