the A/C is not cooling


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Old 08-20-09, 02:20 PM
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the A/C is not cooling

I have a comfortmaker 10. I try to cool the house to 75oF during daytime, but it take forever to cool the house for 3 or 4 degrees take forever.
both inside and outside sound running, outside unit still blow the very hot air. but the air blow through the inside window is not cold, the temperature around vent is about 66-68oF.

two tube connect the outside unit: on big metal tube covered with foam is freeze cold, and other smaller tube is in regular temperature.

I asked a Tech, he checked that freon still full, but it is not cooling. he ask 4000 US dollar to replace both units and 2000 dollars to replace the compressor.
I was wondering if there is way I can check problem my self before give such big chunk of money away.
please. any comments will be realy helpful
 
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Old 08-20-09, 09:03 PM
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How old is the system ? Have you cleaned the coil inside, or replaced filter lately? Is this problem just occur now ? is there a way you can check the duct leaks ? 68 degree is a problem, you want at least 15 degree lower than your room temperature. Check all the possibilities before spend the big money...
 
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Old 08-21-09, 04:03 AM
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ninaqn

my central ac condensed water leaking
 
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Old 08-21-09, 04:09 AM
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I'am with "clocert" on this, sounds more like an air flow problem. I would start there, did the tech take a temp split across the evap coil?

Did he put any superheat or subcooling readings on the work order?
 
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Old 08-21-09, 05:35 AM
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Arrow Pulling hot air ito the Return-Air from a hot source?

Originally Posted by bjp929
I have a comfortmaker 10. I try to cool the house to 75oF during daytime, but it take forever to cool the house for 3 or 4 degrees take forever.

Both inside and outside sound running, outside unit still blowing very hot air. but the air blow through the inside window is not cold, the temperature around vent is about 66-68oF.

two tube connect the outside unit: on big metal tube covered with foam is freeze cold, and other smaller tube is in regular temperature.

I asked a Tech, he checked that freon still full, but it is not cooling. he ask 4000 US dollar to replace both units and 2000 dollars to replace the compressor.

I was wondering if there is way I can check problem my self before give such big chunk of money away.
please. Any comments will be really helpful
Don't spend any money yet!

Take a thermometer & check the temp of the outdoor condenser discharge air.

Post that temp & the outdoor temp.

If the condenser temp-split is real high it could be pulling hot air ito the Return-Air from a hot source.

If possible, check the air temp just head of the blower & at the Return-Air grille, post here.

The system is probably charged to handle that extra hot air load, therefore, the large pipe is very cold, but the small pipe is close to outdoor temp.

If the above is the case, it will be way over-charged when the situation is fixed.
 
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Old 08-21-09, 12:43 PM
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cleaned inside coil, stop work again.

Thanks for your comments
the AC problem 8 years old,
my house is 1299 sqft, in Texas Lubbock
I have taken suggestion and clear the inside coil with brush and soap and water.
I bought a new filter last night right after clean, it was worked. I mean the blow cold air which is 60 oF (15 degree below the target temperature 75). then , I keep it on for overnight.
right now, I just came back home, and checked the temperature around the blow vent, it showed 66 degree.
does that mean my coil is the problem? do I need call a professional to clean it?
the last Tech was a moron, he did not even open the cabinet and unit, he just check the freon and out unit, then ask for 2 grands to replace a compressor.
thanks for all the information.
 
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Old 08-21-09, 01:16 PM
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temperatures

Originally Posted by HVAC RETIRED
Don't spend any money yet!

Take a thermometer & check the temp of the outdoor condenser discharge air.

Post that temp & the outdoor temp.

If the condenser temp-split is real high it could be pulling hot air ito the Return-Air from a hot source.

If possible, check the air temp just head of the blower & at the Return-Air grille, post here.

The system is probably charged to handle that extra hot air load, therefore, the large pipe is very cold, but the small pipe is close to outdoor temp.

If the above is the case, it will be way over-charged when the situation is fixed.

I just did some measurement, here is the data:
time 3:10 pm

outdoor 95oF
post condenser 104oF
garage 93.2oF
below the filter 80.6oF
below the blower 55.4oF
next to the blower 73.4oF
return air inside 66.4oF

does it mean blower have promblem? or the duct is leaking?
 
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Old 08-21-09, 02:32 PM
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I don't understand your locations of the measurements. Where is below the blower ? where is below the filter ?? where is return air inside (66?)? All you have to do is check the nearest air vent from your A/C unit, that cold air come out of that vent should be at least 15 degree lower than your room temperature at that time( not your set target temperature). and also, the cold air should blow strong, not feels like blocked by anything. So, check it again, and let us know. Also, you said when you came back home, the air blow was 66 degree. What was (Did you take) the room temperature at that time ?
 
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Old 08-21-09, 04:17 PM
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temperature of the air from vent is 66 oF, room temperature is 75 oF

sorry about misleading.
"below filter" means I stick a glass thermal meter under the filter and measure the temperature of air before it run into the coil.
"below the blower' means I opened the inside unit, and put thermal meter right between the blower and coil.
'next to blower' means i opened the inside unit and put the thermalmeter next to the blower when it still running. feel like it produce some heat into the chamber.
 
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Old 08-21-09, 04:19 PM
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Originally Posted by bjp929
I have a comfortmaker 10. I try to cool the house to 75oF during daytime, but it take forever to cool the house for 3 or 4 degrees take forever.
both inside and outside sound running, outside unit still blow the very hot air. but the air blow through the inside window is not cold, the temperature around vent is about 66-68oF.

two tube connect the outside unit: on big metal tube covered with foam is freeze cold, and other smaller tube is in regular temperature.

I asked a Tech, he checked that freon still full, but it is not cooling. he ask 4000 US dollar to replace both units and 2000 dollars to replace the compressor.
I was wondering if there is way I can check problem my self before give such big chunk of money away.
1. Why did tech think compressor might be faulty? He must have given you some sort of explanation as to why he thought your house was not getting cool.

2. You said you try to target 75F. But it takes forever to cool 3-4 degrees. That leads me to believe, the way you put that, that it does cool - except it just takes a real long time. Otherwise you would have, or should have said it is not cooling.

3. At 95 degrees out, and perhaps sun pounding on the house ontop of it - and if say you are starting to run the a/c only during the day after it already got to be 78 - 80 inside? (a presumption based on how you want to target 75 but, have a hard time getting the temp to drop 3-4 degrees), it is possible there is nothing wrong at all. I work on condos where we have the very problem you speak of. Often it is simply how they sized the unit. They sort of intend it so the a/c has to run almost continously, to maintain that desired temp. But if you wait too long into the day and try to gain headway to get it to cool the house down, it can indeed take a long time.

4. You said that after you cleaned the coils you were able to get 60 out the vent at night? Yet during the next daytime 66 came out, leading you to believe it was up to it's old bad tricks. Maybe not. At night everything was cooler, both outside and inside, and therefore this also affects the temp that comes out the register. That is just how it works with a/c. As crazy as this sounds, if the air is too hot, the a/c does not cool as well. And I think most people presume that that is the very reason they invented a/c -so that the hotter it gets, the cooler you can get, right? Well, there are limitations to what can be achieved, unfortunately.

5. Please honor requests from others here to take the temp at the closest cold air return to the blower unit, and another reading that is from the cold air regsiter that also is closest to the blower unit.
 
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Old 08-21-09, 04:37 PM
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thank you all for such helpful information.
1. when tech came, he just take a thermal reading in different vents inside of house and took a read over the thermal-stat. then then connect a meter to outside unit with two tubes. one meter showed a number of 200 or something, he said freon is ok; and other one showed the temperature is 90, and it keep unchanged. he said that the compressor valve maybe damaged, and it can not pump the cold air inside.
but the bigger tube is cold, and inside unit big tube also cold, and the inside coil also very cold.

2. I try many time from different vent. the air temperature out of vent is 66-67 oF, and the temperature around vents for inflow is 75-76 oF

3. the air flow is as strong as couple years ago, I donot feel the reduction of air flow.

Thank you so much for the reply.
 
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Old 08-21-09, 05:35 PM
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10 degree split is not enough, you do have a problem. But your after coil temperature is 55, that means by the time the air gets to the vent, it becomes 66. it increased 11 degree in the duct. I am not sure if that is right, let other people comment on that. At this point, I don't know if you have compressor problem or not, You may want to call another tech and get a second opinion. If he meter your outside unit, get the 2 readings down and post here. some one here should be able to help you.
 
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Old 08-21-09, 07:29 PM
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If the readings you gave for the hoses hooked to the outside unit are 200 and 90, you may very well have a compressor with bad valves.
 
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Old 08-21-09, 09:13 PM
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If you have a bad compressor, you can get a compressor to match your coil. there is no need to replace both if the coil is still in good shape. $2000 is a little too high in north Texas. shop around and try to get one below or around $1500 since your system is not that big anyway (you did not post the A/C size, but for a 1300 sqft house, your unit shouldn't be larger than 3-ton.
 
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Old 08-21-09, 09:20 PM
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if it's the compressor's problem. why I still get the cold air after I washed and clean the coil?
what's the normal temperature around coil during its running?
does anybody know the cost to hire a professional to clean the coil or whole system?
 
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Old 08-21-09, 09:40 PM
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updates

ok.
tonight, i checked it again.
the outside temperature is 77 oF
room temperature is 75oF
the air from vent is 60oF

looks like the temperature is related to the outside temperature.

does that mean I got a leak on chamber or duct?
or because the blower works less than daytime, it thus produce less heat?
anyway to check if the blower is produce too much heat? any way to clean it or make it running smoother?

by the way, my compressor is CR28KFPFV130, 2.5 ton
 

Last edited by bjp929; 08-21-09 at 10:05 PM.
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Old 08-22-09, 06:45 AM
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Different between day and night, no, shouldn't work that way unless the duct/chamber is leaking and you draw the outside hot air into the system. I know you have a 11 degree increase in the front side of the duct, but more important is the back(return air) side or the chamber.
Check/measure the temp difference at all the ducts and air vents to see you can find any leaks. See HVAC RETIRED post.
Do you have a veriable speed blower ? Usually blower does not generate that much heat at all. but you do need to find out why 'next to the blower' temperature is (73) high. AS mentioned by HVAC RETIRED, your low side reading (90) is too high, the system may be overcharged to handle the leak in hot air. to clean the system, may be around $150-200. Coil temperature varies, I never measured near coil temp inside the chamber except once, I remember it was around 52 with the chamber open. but for your reference, my air vent is 60, room is 77 . hope this help...
 
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Old 08-22-09, 10:35 AM
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updat

thank you all for such kindness
I took out the blower and cleaned it. after I put it back, I turned on the fun without cooling and kept chamber open, i feel that air flow through the vent is more strong than that during the cooling with chamber closed.

does that mean the coil is too dirty, last wash is not completely remove all the dust and grease? can I use a high power wather spray to clean the coil, is that safe? and how to check the leak in the duck? any simple tool or need a professional?

really appreciate your help!!
 
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Old 08-22-09, 11:02 AM
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But if the air volume increases, that will not make the air cooler out the vents. It will actually make it warmer since more room air per second will be mixing with the constant a/c coil temp.

I have never heard of this, but say your evporator coil was somehow off kilter (or rotted thru) on where it sits, and there is a place for part of the warm return air to actually blow around the evaporator coil, this could cause your register temp to not be as cold.

When you say you cleaned the coil - which coil? -the outside coil or inside coil? If the inside, did you make any mental notation of how it looks around that coil, where something like I spoke of could be a possibility?

And this got me thinking of something else: Did anybody ever change out the blower motor say to a bigger one with more rpms? That could cause the apparent cold air return restriction symptom also. And also cause somewhat higher vent temps. Although these theories would not explain why the apt. has such a hard time cooling down, since even if slightly warmer air was blowing out, more total cool(yet slightly elevated in temp.) air volume would be blowing out, and offset the negative effect. In simpler terms, you'd still be blowing a high velocity of air through the constant cold coils to draw the maximum cold from those coils.
 

Last edited by ecman51; 08-22-09 at 11:13 AM. Reason: added more
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Old 08-22-09, 01:15 PM
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If you need to know what all should be operating, just ask.
 
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Old 08-22-09, 01:50 PM
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I am still confused about your measurement points. Below the filter-- is the filter inside your room or in the chamber right before the blower ?? I assume your air handler/chamber is in the attic. Below the blower -- (between coil and blower only shows 55 degree ?) is the return air hit blower first or coil first?
In a regular system, the return air should hit the chamber filter first(not the filters inside the rooms, if any), blower second, and then the coil last..if you put the thermal between the blower and coil, the temp should be room temp, not 55, unless your coil come first and then blower...but then next blower should not be 73. anyway, give us a clear picture and go from there.
 
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Old 08-22-09, 06:22 PM
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sorry for confusion
air lfow in my sysytem is:
it reach the filter first, then pass through coil, and blower on the top. my indoor unit in the garaage, and it's a vertical box, filter on the very bottom of the box, the coil in the middle and blower on the top. and air flow from bottom into the top duct.
I check one more time, and feel that air flow become much weaker after it pass through the coil, therefore, the blower did not have much cold air to blow into the duct, that's why it produce heat. i put my hand on the coil, it is feel freezed cold.
so, ifs taht normal or the coil is been blocked by the buid up dust.

I am not sure is that a problem, but I have climbed into attic and did not find hole or some major leak source from the duct.


what's wrong with firfox, every time I try to open this page, it ask me to up dat the flash player?
 
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Old 08-22-09, 09:44 PM
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I get the picture now. I thought you said the air blow is strong, same as 2 years ago when the system was OK. Anyway, As I mentioned, if your coil is cold, air come out the coil is 55 degree, why the air temp at the blower becomes 73, they are may be only 1 or 2 foot apart, and should be nothing in between. Go ahead check it again, this time put the thermal on the top of the blower, best way to do this is stick the thermal into the chamber from a hole, do not open the chamber so to get the real reading. or go in from the top so you don't draw hot air into the coil or blower.
I expect you get 55 or 56 degree (you should, weak air flow does not affect the temperature), then you should have 60 degree air blow into the room. if not, something is not right. Let's make sure the air temperature at the top of the blower is right first, then worry about the air flow. weak air flow can be caused by dirty coil, bad blower, dirty(or too expensive) filter, or blocked duct or vent (both return and going out),.....
 
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Old 08-23-09, 01:02 PM
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looks like the chamber is leak somewhere.
I draw a hole on the foil box right above the blower, and stick thermalmeter in to it, the temperature reading is 67oF, the return air also 67oF. that mean the duct is alright.
as mentioned the day before yesterday, coil is cold. looks like about 11 degree difference between coil surface and the air past through blower. does blower produce that much heat, or the air was blocked by the coil?
 

Last edited by bjp929; 08-23-09 at 01:23 PM.
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Old 08-23-09, 01:45 PM
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Can you see that the coils are clean or dirty on the filter side of the coils? If in doubt as to condition of coils, you may want to slide out the blower assembly (may be held in place by only 2 screws and blower assembly slides out on two side tracks) and you can use a bright light down in where the blower sat, to see if you see ample light shining thru the fins on the filter side. If ever you had a histroy of neglecting to change filters, or they got damaged or torn out, rather than slid out, and dust got sucked into the fins, that can cause clogged coil fins. Or if dusty house and only cheap fiberglass filters were used. Or no filters used at all during some stretch.

If you shut off the blower, and wait for blower wheel to stop, does the blower motor feel scorching hot, or you can even feel hot air wafting from above it?
 
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Old 08-23-09, 02:52 PM
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I am really confused now. 67 in, 67 out, that means your coil is useless this time (may be only cool the fan down, but I don't think the fan generate that much heat). How did you get the 55 degree below the blower Yesterday while outdoor temp was 95? One basic question. Does this problem come overnight ? one day was OK, next day problem came, or it goes bad slowly, a little a day, after say 1 month or 2, you noticed it is not cool anymore.
 
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Old 08-24-09, 05:37 AM
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And, if the return air temp is 67 degree. that is pretty cold already. What is your set target on the Tstat ? Well, at this point, I believe it is time to call another professional tech for help. Good luck toyou.
 
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Old 08-24-09, 12:32 PM
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i think there is misunderstand here.

the air flow in my indoor unit is from bottom to the top, it pass the filter first, then coil and reach the blower, then inject to the foil tube

the temperature of air
before it reach coil is 75oF
after it pass the coil is 55oF, means coil cool down the air
when it been inject into the foil tube, it is 67oF. looks like it increase 11-12 degree just pass through the blower. how is that possible?
the return air is 67oF too. means problem is inside of chamber.
 
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Old 08-24-09, 05:06 PM
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I followed.

Bu I do not know what a foil tube is. I'd say that is your evaporator coil that has that 'foil' on it, rather than plain fins. But you already said it passed through a cold coil already. ??

If your blower/evaporator handler is out in a hot garage? ---do you have a lot of long uninsulated cold air return duct in a hot garage that might explain the rise in temp from the 67 cold air return to 75 before the coil?

But where is the incoming 67 reading taken exactly. That is quite low for a cold air return reading, actually.
 
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Old 08-25-09, 08:15 AM
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I see the point. Now the question is why the air temp increase 12 degree after it passes the blower. from your post, the heat source must come from the area between blower and coil.
or the blower itself is hot. Where is your heating element ? I just remeber now I had a house with vertical unit like yours had a strange problem like this. The problem was the heating element was also on when the A/C was on. If not, then touch the blower right after it stops and see if it is really hot. If there is no leak in that area, I just can not figure out anything else that can cause this problem. (Also, if the return air is 67, then the air passed the coil should be lot less than 55, I like to see 45 come out of the coil. from this point, the coil is not cold enough)
 
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Old 08-25-09, 12:17 PM
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thanks, guy.really appreciate your time!
I opened chamber when its on. I put my hand close to blower, and I can feel warm air (about 70s) blow out of out of the blower.

if the heat element is the problem, how can I test if it is on or off?

i got two control switch in my central box, on for a/c, another for heater. does that heater mean the heat block in the A/C?
 
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Old 08-25-09, 01:13 PM
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If (I assume) you have electrical heat ? Do you see the heating elements in there ? if it is in the same area near coil and blower, Turn the A/C on for 10 minutes, make sure you get 67/70 degree out of blower and 55 out of coil, then turn it off, and immediately check to see if the fan motor is warm/hot, and also check to see if the heating element is warm/hot, if not, we can eliminate these two items.
 
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Old 08-25-09, 08:00 PM
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i checked the motor after about 10 mins run, I did not feel the motor get warm. I also did not feel significant heat release from the heater part.

i checked air temperature on the surface of coil (not touch the coil), it showed 50oF.
what's the normal temperature for the coil?
 
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Old 08-26-09, 11:55 AM
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It is over my head now. If the air comes out of Coil is 50, How come it becomes 67 after the blower. (how about the air temp right before the blower ? and how far is your blower from the coil ? anything in between or any leaks in that area ?) Coil surface temp is vary, depends on which section you touch and it is affected by a few other factors, also it is hard to measure because of the strong air flow. but it should be around 30-40 degree or even lower. People measure the pipes outside the coil to get the subcool/superheat numbers, but not the coil itself. Anyway, unless you can find out why from 50 to 67, this is going to be a hard one.
 
 

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