A/C not cooling well


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Old 05-25-10, 07:49 AM
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A/C not cooling well

My A/C has not been working too well. It's not been working well for a few months pretty much but its been bearable. I've been out on vacation for a few days. The day I left for vacation I came home from work and the house was 90 degrees. Since I was about to go on vacation I figured I'd just deal with it when I got back. When I got back I took a look and realized the disconnect lever was in the wrong position.

I switched it on and let the A/C run for a couple of hours but it still wasn't making much difference so I called an A/C technician.

The technician checked the refrigerant levels, checked the amperage draw at the compressor took a look at the air handler and says he didn't see anything wrong except in the disconnect outside next to the compressor someone had replaced the fuses with copper piping.

He suggested replacing the disconnect with one with a breaker and said something might be wrong with the current disconnect and said it could be the cause of the problem. He recommended that I replace it myself since it should be fairly simple to do to save myself the $300 his company would charge. He said the A/C compressor might be going too but he would need to check that when its hot and sunny outside.

So I've had the A/C on all night and its been running the entire time I believe. Last night it was around 75 degrees and today so far the temperature is only up the 80 degrees so far though it is quite sunny out. The temp in my house though is currently 85 so my A/C still doesn't seem to be working too well.

I went to home depot to try to find a new disconnect and they had two types fusible and non-fusible with just a switch. One of the people working at home depot said you could put a breaker in one of the switch type disconnect boxes and I was reading the instructions for it and it said that you needed a QOT or HOMT breaker but I am not completely sure what that means. Is there anything wrong with using a fusible box like the one that is currently there?

So I'm wondering is can a malfunctioning disconnect cause a problem like this and should I replace the disconnect or just remove the copper tubing and put in the proper fuses?

Thanks for any help you guys can provide.
 
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Old 05-25-10, 03:07 PM
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the disconnect not being properly configured or whatever can cause your compressor not to run correctly, BUT, it would make an unusual sound and have trouble starting most likely. but if its running i dont see how it would cause a problem like not cooling well. check your filters. so i would not replace the disconnect as it will accomplish nothing. seems like he was just thinking of stuff cuz he could not find a problem. if you have a thermometer of any kind i would be interested to know what temp the air coming out of the vents it and what temp air is going in at a return. you should have atleast an 18 degree differential. i can only think of one other thing, if your condesner is dirty it would make the small copper line warm or hot and if it is hot(while running) then it means that your system has trouble removing the heat out of your house. if thats the case, turn off power to unit, pull disconnect and spray with a hose on the fins until u see dirt and crap come out. take ur time in cleaning and dont bend the fins with the water. or search web for how to clean condenser or use http://www.ehow.com/how_5051537_clea...condenser.html
 
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Old 05-25-10, 04:53 PM
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I agree with ender2272, disconnect is not your problem. as mentioned, try the simple things first, replace filters, clean the unit,... etc...if that does not help, then take the temperatures.. one other simple thing you can do is try to feel the large pipe outside while the system is running to see if it is cold, if not, you have a problem, by the way, do you know how to tell if the compressor is running ?? but do one at a time.. post back and we go from there.
 
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Old 05-27-10, 06:14 AM
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Thanks for the replies.

I don't have a thermometer I'm trying to find one but Home Depot didn't have one. But if I can find one somewhere I will check the temps at the registers.

I felt the larger pipe going from the compressor and it feels cold but not sure exactly what temperature it is. Also, the smaller pipe doesn't feel hot. But it's not very hot out now. And my A/C is actually reaching the target temp and turning off (I have the thermostat set to 82 right now, its somewhere around 80 outside I think).

I will give cleaning out the compressor a go and wait for a hotter day and hopefully have a thermometer to check temps.

I got some fuses for the disconnect box and I will change out those copper pipes for fuses so I'll know if the compressor starts drawing too much current.

I've been trying to figure out how the switch got turned off since it's a fuse box it would burn a fuse not switch off if something went wrong, correct? And there were copper pipes in there instead of fuses. I think what probably happened is my dog probably turned it off. The lever is on the outside of the box and I've seen her chasing lizards in the vicinity of the A/C compressor before.
 
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Old 05-30-10, 06:39 AM
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So I got a thermometer and checked the difference between supply and return air. I've heard the difference should be at least 18 degrees. And so far when I've checked a couple of times it has been 17-19 degrees of difference.

Using the thermometer to measure the air temp in the house I've realized that the thermostat is not measuring the temperature accurately. It usually says the temperature is 3-4 degrees hotter than my thermometer says. But its not always the same amount though. For instance right now it says the temp is 89 degrees while the thermometer says 81. And it doesn't feel like 89 though so I'm more inclined to believe the thermometer.

But there have definitely been times where it says the temp is high and it is. Like when it was fluctuating between 90-94 when the AC compressor wasn't coming on it was definitely around 90 degrees inside.

So I'm thinking maybe I need to replace it.
 
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Old 05-30-10, 07:23 AM
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Thermometer should be accurate to within 1 degree. Get a good one, or get couple more to compare. Your tool must be right to do the job right. From your temperature difference of 17-19 degrees, your A/C is working fine. Most old thermostats are not accurate, but within 1 or 2 degree is acceptable. SO, get your temperature reading right first and go from there.
 
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Old 05-31-10, 05:00 AM
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So I took your advice and got another thermometer and that one was within one degree of the first one and the thermostat was still a few degrees off of both thermometers and like before the amount it was off was inconsistent.

I replaced the thermostat and the new one seems to be pretty accurate. So it should shut off now when it's supposed to.

I'll just clean out the condenser outside and just wait for the temps to get around 90 again and see what happens.

I'm just not sure why if its running constantly why it doesn't get below 78-79 degrees when its not that hot. You would think if its 80-85 if should be able to at least cool down to 75, right?

Could attic insulation be a problem? I know when I bought the house the building inspector said it might be a good idea to replace since it was old and had been water damaged at some point.
 
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Old 05-31-10, 10:24 AM
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With 17-19 degree difference, your A/C is fine. I assume the air blow into the room is strong, not blocked by dirty filter or by expensive filter ( cheaper one is better for air flow). The only other thing you need to check is the insulation (window, door, wall, ceiling. etc.) There must be some heat source prevent the room from getting cooler. you need to find that, then your problem will be fixed. There are professional people use heat image camera to find the heat source, or you can do it yourself, buy a temperature gun to search every inch of the room, and hopefully you will find where the heat source is. I don't know how old your house is, if it is very old, the insulation may not be good anymore.
 
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Old 05-31-10, 12:34 PM
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Ok, so today it is hot outside. It's about 88 degrees outside and quite humid. And I'm back having temps in the mid 80s inside. It's 83 degrees inside currently.

I checked the air temp split again and the return air is 84 degrees and the supply air is about 71 degrees.

I also checked the temperature of the pipes outside going into the compressor and the large one is about 70 degrees and the small one is a little over 90 degrees.

In the article that was posted earlier in this thread about cleaning your condensor it says the larger pipe should be around 30 degrees.

What are some of the problems that would cause this pipe's temp to be higher than normal?

I do think part of my problem is insulation. I live in an older house. The house was built in 1950 and the A/C is 18 years old I think so the insulation is probably pretty old and I know the air handler in the attic had leaked at one point before I bought it and some of the insulation got wet so I'm sure that didn't help matters any.

I do have a more expensive air filter I can switch to a cheaper one and see if that makes a difference but it has been changed within the past two weeks so it's not dirty. One of the thermometers I have is an IR thermometer I can use that to try to find hot spots.
 
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Old 05-31-10, 08:31 PM
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Now the temperature difference is only 13 degrees, that indicates you have a problem. usually, low difference and large pipe not cold are caused by low freon. So, at this point, you need to check to see if your freon level is correct. 88 degree and humid day, your outside large pipe should be cold to touch and you should see the pipe sweats a lot (lots of condensation water).
 

Last edited by clocert; 05-31-10 at 10:31 PM.
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Old 06-01-10, 05:02 PM
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Originally Posted by clocert
Now the temperature difference is only 13 degrees, that indicates you have a problem. usually, low difference and large pipe not cold are caused by low freon. So, at this point, you need to check to see if your freon level is correct. 88 degree and humid day, your outside large pipe should be cold to touch and you should see the pipe sweats a lot (lots of condensation water).
On condos I do work at, the split is also only 13 or 14F/....73/59 (using same thermometer to test at large cold air return and a nearby register) degrees, and the outside big pipe is real cold and sweaty. Perhaps a split reading is not the entire story, say if the outside unit is of lower tonnage and if say the inside blower speed is perhaps too high. ?
 
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Old 06-01-10, 05:50 PM
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There are many factors can affect your room temperature, but large temperature difference between in-air and out-air is a must. In Texas, 15 degree is the minimum to be accepted by professional building inspectors. For a home owner (usually don't have all the A/C tools), hand feel outside pipe, and check in-out air temp are the two easy things to do. If that condo you mentioned only has 14 temp difference, then there is a problem with that one too, (not big problem since it is only one degree off. remember, newer unit these days can get to 20 temp diff). To be accurate, you need to check the air temp right before the air handler and right after it, so to eliminate the heat/cold lost in the duct work. That condo has cold pipe but not cold air, I bet the duct work either leak or not insulated right. Blower speed is also a factor, but there are so many things can go wrong, you need to do one thing at a time, and check common problems first. So if the duct is insulated right, no leak, then I think the next thing to do should be freon level check. (simply because the large pipe is not cold, and I assume your large pipe is insulated correctly all the way to the outside unit.) You need a gauge to check the freon, if you don't have one or never did this before, you may have to call a tech.
 

Last edited by clocert; 06-01-10 at 08:48 PM.
 

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