Lennox A/C does not work right any more


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Old 09-07-08, 03:33 PM
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Lennox A/C does not work right any more

Hi guys & gals,

A new member here from the north ATL area (Cumming) and this is my first post here. I am happy I found this forum.

We have lived in our Pulte-built home since late 2000 that was constructed in the same year. Central Lennox A/C system and we just found out today that the upstairs' system does not work the same way it has been doing the last 8 or so years.

Before it could reach the 78F what we set it for but now it is running full time, still blows some cool air but the thermostat meter does not get lower than 80F. It is an unusually hot day here today, about 88-90. The outside A/C unit stays in direct sunlight from the morning until about 2PM. It is 7 PM here now.

To be exact my wife noticed something "different" yesterday too with the A/C.

Our system is thus about 8 years old, never serviced, checked out or maintained, except for new filter(s) that I did last time today. It did not help.

The A/C units outside the house (2 total) work (fans work) and the temperature of the blown air I felt about the same, if that means anything in troubleshooting.

What could be the problem and what would be the most economical way to fix this problem? Anything I could do myself?

The builder (Pulte) recommends "Reliance" for the repair (perhaps they installed the system) and I indeed have seen their vans in our neighborhood.

Any help and advice greatly appreciated!
Thanks.
 

Last edited by pics20; 09-07-08 at 03:56 PM.
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Old 09-07-08, 03:58 PM
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Could be low on freon and coil in blower unit froze also. You can thaw out frozen coil by turning off a/c and run blower fan in the "fan on" setting on your thermostat.

What did your wife notice that is different? You must have forgot to say in your post?

It be interesting to find out what she noticed. But if the outside compressor and fan out there is running, and the indoor blower is blowing air, and you changed the flilter, you most likely need a tech out there. By law you cannot put in more freon, for one thing.

I reread your post and I missed a line. You say it is unusually hot there. But even if hotter than expected where you live, I think about anywhere in the country they would have to size units to handle 95 degrees, anyway. I'm not up on that particular exact aspect, but one would think so. Way up north we get 100 sometimes (at least we used to).

I also see you mention about 2 units outside and the fans run. At first I presumed you meant the fan and compressor run. Be sure the compressors are running out there, along with the fan. Get back to us about that, please.
 

Last edited by ecman51; 09-07-08 at 04:10 PM. Reason: added more
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Old 09-07-08, 04:08 PM
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Originally Posted by ecman51`
Could be low on freon and coil in blower unit froze also. You can thaw out frozen coil by turning off a/c and run blower fan in the "fan on" setting on your thermostat.

What did your wife notice that is different? You must have forgot to say in your post?
EC, thanks for your very quick reply.

I'll turn off the A/C right now to melt the ice if any, we can stand that perhaps for one 60 minutes as it is hot here. I know it will release all the little cool air we have here but I am willing to experiment and troubleshoot. The ice should be on the coils of the outside units, right?

What my wife told me that she felt yesterday like there was less cool air coming from the vents, confirming what I found out today....
 
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Old 09-07-08, 04:16 PM
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EC, Quick update...checked the coils in the outside unit, no ice what ever. I turned the system off and while checking the unit outsise I could hear some little noise from the coils (perhaps shrinking/expanding after turning the system off after being several hours on)

Originally Posted by pics20
EC, thanks for your very quick reply.

I'll turn off the A/C right now to melt the ice if any, we can stand that perhaps for one 60 minutes as it is hot here. I know it will release all the little cool air we have here but I am willing to experiment and troubleshoot. The ice should be on the coils of the outside units, right?

What my wife told me that she felt yesterday like there was less cool air coming from the vents, confirming what I found out today....
 
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Old 09-07-08, 04:20 PM
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No. You want to turn off the a/c setting on that stat to off, and put the fan to on. The ice would be inside the handling unit in the house where your blower is in that very same unit. You see, that is where the cold coils are located. The hot coils are outside. Some people do not realize that the outside units are not all there is to the a/c piping and coils system. Like I said, the cold coils are in the handler. The big and small copper lines go between the inside handler and the outside unit(s).

The fact you have some cool air now leads me to rethink that your compressor is probably running. UNLESS you have 2 whole outside units in tandem, where just one compressor is working and can't meet the demand. Check that out. If you have 2 complete seperate outside units, make sure both compressors can run. If you already turned off the units, wait maybe 20 minutes to turn them back on. Not a good idea I guess to switch them back on again until pressures inside do what they are supposed to do in equalizing.

Did you reread my first post as I added more than what you quoted above.
 
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Old 09-07-08, 04:24 PM
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Since you still have some cool air coming in, that means your system is still working (to some degree). Does your big insulated line go into outside unit feels real cold while the system is running ? or just a little cool ? If it is not real cold (alomost feel like ice), than you need to check the freon level first. After 8 years, add a little freon is very common. Hope this is your problem.
 
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Old 09-07-08, 04:56 PM
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I have now turned the AC system off with fan on, I'll wait for those 20 minutes or so before I turn the A/C on again.

How I can check the operation of the compressor? Where it is typically located? Next to the furnace?...editing EC: I reread your post, the handler must indeed be next to the indoor blower/furnace I believe.

These two systems are completely separated, one for the main floor, the second one for upstairs.

Closert, many thanks for your response too. I'll report back on the coldness of the pipe as soon as I have done the ice melting procedure EC is suggesting.

I am somewhat confused though...is one pipe to the outside unit suppsed to be hot and the insulated pipe cold?

You can notice I am not an AC expert here
 
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Old 09-07-08, 05:08 PM
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Just to clarify some terms...

The compressor is part of the condenser unit, the thing that is outside of the house. It is the heart of A/C - it moves the lifeblood of it, the refrigerant or "Freon".

Also, when we say "handler" we mean whatever is in your house that moves the air. For some people, this is a gas furnace, electric furnace, etc. For others it is simply something blows air only. The blower is inside this unit, the actual device that moves air. The cold A/C coils are also part of this area.

Furthermore, regarding the pipes or "lineset", the small copper pipe should be warm to hot, with the big insulated line cold and sweaty.
 
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Old 09-07-08, 06:24 PM
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tks codyy for the clarification.

just little new info:

After EC's ice melt process I turned the AC on...feels like little colder now, hard to say and perhaps it feel such as the sun is down now. I did not measure the temperature at the vent before or after, sorry.

I checked the insulated pipes outside while both systems were running...they feel the same, cold and sweaty, cannot really tell the difference.

I happened to see my neighbor while outside, he has the same Lennox system. He advised me to check the insulated pipe from the outside unit as when he had low freon situation the outlet from his outside had frozen. Does that make any sense?
 
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Old 09-07-08, 06:43 PM
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Air Conditioning Problems

If you want to do anything yourself take a temperature reading at your filter and at one of your supply vents then go outside and clean both of the outdoor units you can get a mild detergent coil cleaner from your local HVAC supply house follow the directions and rinse thoroughly then after restarting the unit allow 15 or 20 minutes for the coil to thoroughly dry then take a temperature reading at both places again if you are not dropping at a rate of 15 to 20 degrees then you may be undercharged and you probably need to call for service or you may want to check your return duct in your attic to make sure you are not drawing in hot attic air
 
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Old 09-07-08, 06:44 PM
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either low on freon or dirty condensor coil. Probably both.
If both suction lines feel the same ... Cooler out now, I would suspect a dirty coil.
Garden hose. Flush it out. Don't bend the fins.
 
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Old 09-07-08, 07:05 PM
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Ed & Mike,

The outside unit looks OK, not too many weeds around it and when I was peeking in while the system was turned off I really did not see anything special (dirt etc) on the fan blades or on the coils. So I think flushing it does not help here.

All this info I have from you guys makes me believe the system is low on freon...if that is the case who much $ I should be expecting to pay? I probably get the downstairs system checked at the same time, possibly recharged to same some money in the longer run?

If the system is low in freon where in heck it can leak from? How common it is?
 
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Old 09-07-08, 09:03 PM
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Well, you did said the large insulated pipe feels cold and sweety. then your freon level may be OK, and you did check the outside coil, you said that is OK, so the next thing you need to worry is inside coil (evaporator coil). inside coil is not easy to check, not easy to clean either. If you did not change your filters often the last 8 years, may be the inside coil is dirty now. At this point, you may need to call a AC tech to check the whole system for you. To add the freon will cost you some where around $100 -$200 per system depends on how much freon do you need. It can leak anywhere along the line and at both ends. Like I mentioned, after 8 years, add a little freon to the system is not bad at all.
 
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Old 09-07-08, 09:17 PM
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You did everything you could - it's time to get the refrigerant charge checked.

If it's low on refrigerant, there's a leak; DON'T LET ANYONE ADD REFRIGERANT without fixing the leak first.

Also the wetbulb return air temperature and refrigerant line temperatures will have be measured to determine if the charge is off; anyone who relies on pressures alone is not qualified to work on HVAC equipment.
 
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Old 09-07-08, 09:50 PM
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Originally Posted by Muggle
If it's low on refrigerant, there's a leak; DON'T LET ANYONE ADD REFRIGERANT without fixing the leak first.
Very important fact there. Technicians can employ some methods to find refrigerant leaks such as dye and electronic detectors. As a homeowner, look for oily areas on the linset and coils, etc.

The only way a unit can loose refrigerant is via a leak, it is a sealed system.
 
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Old 09-08-08, 06:10 AM
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Thanks Gents for the hints, very informative. I'll get a tech and I'll let you know what he finds.

PS: Closert, I have changed the filters about twice a year, I normally use the cheap blue ones, they don't seems to get very dirty (maybe due to their bad quality)
 
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Old 09-08-08, 07:27 AM
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Well, if both of your coils clean, the only thing you have not checked is the small copper line go into the compressor, it should be warm to a little hot while the system is running. and the air blow out of the outside fan should be warm(very warm), if that is the case, then your unit may be OK. The next thing you can do is check the inside register in and out air temperature as suggested by mike n, (I bet you won't have 15+ degree difference, otherwise you won't be here.) This is an interesting one, make sure you report back to us.
 
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Old 09-08-08, 11:00 AM
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I have not called for service yet.

I'll hose the outside unit just to make sure the coils are clean...and do the register temp check as miken and clocert suggest below + the small outdoor pipe temp too in more detail this time. I'll be back..
 
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Old 09-08-08, 02:34 PM
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I had the same problem and the a/c tech came out and cleaned my A-coils inside my blowers. It cost me $250.00 for 2 units to be cleaned. (I did not know how to do it at the time) That fixed it for me. Try that first. You can ask these guys what type of cleaner, if needed to use. I watched them clean the coils and it looks easy. And make sure you change your air filters too!
 
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Old 09-08-08, 06:06 PM
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After 8 years you should call a tech. anyway to tune up the whole system. An ounce a year of leakage is hard to find, but equals a 1/2 lb. of refrigerant.
Plus, the coils probably need cleaning, they should check superheat, subcooling, delta T's, air flow, etc...
3 or 4 hrs work will be worth it for the comfort, efficiency improvement, and increased longevity.
8 yo is middle aged for a split system on average.
 
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Old 09-09-08, 04:01 PM
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Your replies made me to check the inside units in more detail.

They look very much like this:

http://www.hometips.com/articleimage...nditioner1.gif

The evaporator is in a sealed box with no removable panels. The box is "glued" in place with some type of paste/sealant. Should I forget considering cleaning the evaporator coils by myself? How hard the access to them would be?

While in the attic I also checked the pipes to/from the outside unit while the system was running. The large pipe feels cold but the small pipe only kinda lukewarm (or about ambient temp). Same at the outdoor unit. Does that mean anything?

The outside temp now is about 76F, cloud/rain the whole day and the air from the upstairs registers feels cool at about 60F with my probably quite inaccurate thermometer. No problem to reach the set 76F room temp.

I have not had a chance to gardenhose the outdoor unit yet.

PS: The system is Lennox Value Series
 
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Old 09-09-08, 07:35 PM
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You are correct, from the picture, it is not easy to get to the inside coil. But you said your cold air temperature is about 60, room temperature is 76. there is a 16 degree difference, and cold large pipe, warm small copper pipe. Everything sounds fine. I think your AC is running just fine. Of course you can not test it out if outside temperature is only 76 degree. Your problem is when outside temperature gets to 90 degree. This points to one of two problems1) The unit is too small for your house, especially upstair. (2) Room with West sun in 90 degree day is very hard to cool. May be your AC unit performed even better in the past when the unit was new, but 16 degree difference is acceptable for an 8 year old unit.
 
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Old 09-11-08, 11:35 AM
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Thanks clocert. I'll make some more temp measurements and report back when it is getting hotter outside, probably in this weekend again.

If the temp difference still will be around that 16-degree level should I consider getting a tech? I hope not as my money situation is really tight now.

What is included in a typical annual service visit if you have a contract but not an apparent problem with a system? Are those contracts worth spending?

The room where the thermostat is indeed towards south/west and that is room where we noticed the "issue". I took the register temp in that room too.

BTW during the hot day when I first posted here the smaller pipe to the outside unit was considerably warmer than 2 days ago when it a cooler here. I assume that is the way it should be.

Tks again!
 
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Old 09-11-08, 12:30 PM
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Just for kicks, is your attic ductwork (branches) flex duct? Possibly, if origionally taped, may have come (partly) undone.

Or, you may have accidentally 'bruised' one of the runs. One may have become kinked.

Delta
 
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Old 09-11-08, 02:42 PM
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If your temperature difference is 16 degree and the air blow out of your register just AS STRONG AS before, then your system is OK, you don't need a tech for that purpose. The question is why it was OK in the past, but not now anymore. Here is what I am guessing: (1) your unit had may be 18+ or 19, or even 20 degree difference while it was new. (2) The insulation of your house has some problem now, you may want to check the doors, windows, outside trees, etc..anything may affect the room temperature to see if anything changed this year. If nothing else you can think about, you can try to add more freon to the system to push it to the limit to make it work harder. This may not be good to the system long term, but I can't think of any other way to cool the room more except go out buy a bigger new AC unit. (BTW, the pipe temperature go hand in hand with the outside temperature, so they should be different)
 
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Old 09-13-08, 02:12 PM
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delta i,

the duct work indeed in made from that flex stuff but I think they are still OK...looked at the lines at the attic and everything seems OK. Also the air flow at the register feels it is about the same as before. So I think not duct or blower proplem in this case.

clocert,

new temp measurement results as it is hot today but cloudy, very interesting.

Outside temp 90 in shade, has been partially cloudy the whole day.

With the same thermometer incoming AC air temp at the register is now 68F.

Thermostat set in the same room at 76 now but it looks like the system cannot reach it. The actual is hovering around 78.

Thus, the room 78 less the register temp 68 = ten degree difference. Is this still normal for a 8 year old system or would you call a tech to check the system out?

Any other ideas why the system behaves as it is doing?
 
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Old 09-13-08, 05:38 PM
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Rather than subtract register temp from room temp = 10 degrees, you may find temp 4-5 degrees less as it enters the filter at cold air return. Go down there and test that for everbody. And then what the register air is again, about at the same time. Use closest register to air handler.

I recently made such a test and found the air much cooler down low by the cold air return than 5 feet up higher at stat level.
 
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Old 09-17-08, 12:58 PM
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Originally Posted by ecman51`
Rather than subtract register temp from room temp = 10 degrees, you may find temp 4-5 degrees less as it enters the filter at cold air return. Go down there and test that for everbody. And then what the register air is again, about at the same time. Use closest register to air handler.

I recently made such a test and found the air much cooler down low by the cold air return than 5 feet up higher at stat level.
Ecman, I'll do that in the weekend and will let you know the temps. Thanks.
 
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Old 09-17-08, 06:36 PM
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Okay. The usual gang will be around, and maybe different results will influence the ideas. Be sure to use same thermometer in both locations and that enough time is given that each reading bottoms all the way out, for sure.
 
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Old 11-23-08, 12:57 PM
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ecman, just an "update", very sorry for the delay. I could not do the test before it became cooler outside...need probably to wait until the spring to do this. I have not forgotten the subject!
 
 

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