Help! House won't cool! Everyone is saying something different!

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Old 08-07-08, 11:10 AM
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Angry Help! House won't cool! Everyone is saying something different!

I will start with a little background.
I live in a 1400Sq Ft house in Savannah Ga with a 3 ton AC unit.
The house was built in 2005. (Everything is new).
It is a Mitchell built pre-fab home, which is “Energy Efficient”.

Last August while in the house (with similar outside temps) I kept my thermostat on 68 and the house stayed at a cool 68. The cooling unit was able to shut down throughout the day and night and only ran when it “needed to” and my power bill was $225.

This past March the unit stopped cooling well (staying around 74/75 when set on 72) and we called out a service tech. The service tech stated that the unit was fine and it was just getting hot outside. About a week later the unit stopped running all together and another service call was placed. At this point in time it was determined that a transformer had blown. The transformer was replaced, a fuse was placed in line, and the thermostat was replaced the wall.

A couple of weeks later it still was not cooling as well as it has the previous August and when the tech came out he said it was low on Freon, charged it, and said he would be back the next day to find the leak. The following day he came out, stated that there was not a leak and left.

A couple of weeks later, still no change, slowly getting hotter in the house as the summer rages on. Called service back out and was told that it was overcharged.

The house continued not to cool for weeks staying in the low 80’s during the majority of the day and night. I finally was able to get a real AC man out who checked Freon levels with the super heat/cool? Technique who determined that it was still overcharged but stated didn’t seem as if it would be enough to cause the problems that I am having. The coils outside and inside are spotless. The condenser is pulling the correct amount of amps. The duct system was designed poor, but there are no leaks. His recommendations are to increase the intake size (appears small) and add an attic fan.

My problems are this.
Last year it worked fine in the same temp weather with the same structural design.
Other houses with the exact same floor plan and size AC unit are not having any problems.
My bill has increased from 225 to 450 because the unit is never able to shut down.
My house won’t cool lower than 78 from about 11AM-11PM.

What am I missing????
Craig
 
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Old 08-07-08, 11:16 AM
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Are you seeing a 15-20 degree split from air entering to air exiting the nearest register?
 
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Old 08-07-08, 11:22 AM
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Craig...no A/C guy here, but it might be helpful to them when they do get here, if you could post model numbers of the units you have, both inside and out. Also type/model of thermostat.

Also, tho I know thats a huge increase in power costs, you should look at the actual usage, not just the dollar amounts. We had an rate increase here that raised my bill almost 25% though my usage is about the same as last year.

BTW I had a similar problem with my last house, and it was as simple as replacing the original mechanical thermostat with a quality Honeywell. Boom, problem gone..house comfy. And it was only 3-4 yrs old at the time.
 
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Old 08-07-08, 11:51 AM
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Tinman has the right idea. Check the air temp going into the return grill and check the air coming out of the register. Then check the air temp going into the condenser outside and check the air temp coming off the condenser. Write those numbers down and post them here. Also, check to see how much water is coming from the condensate drain. Is it pouring of just dripping a little or none at all.
There are those who think refrigeration theory is irrelevent here, but a basic understanding of heat transfer can help you get an idea of what information is important. You have to give off heat in order to pick up more and you have to pick up heat in order to give it off later.
Is the condenser dirty or stopped up?
Is your filter clean?
You didn't say what kind of heat you have, but is your heater running at the same time as the AC?...don't laugh...it happens.
Is the big copper line going to the condenser cool to touch and is the little copper line warm?
Do you see ice anywhere?
More info would be helpful.
 
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Old 08-07-08, 11:54 AM
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I am getting difference of about 14 degree's at the closest vent, so it is blowing out some cold air. There is about a 8 degree difference between the coldest vent and the warmest.


Thanks
Craig

I will post model number info when I get home..
 
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Old 08-07-08, 12:10 PM
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Check the air temp going into the return grill
78
check the air coming out of the register
64

Then check the air temp going into the condenser outside and check the air temp coming off the condenser.
No way to check currently..

Also, check to see how much water is coming from the condensate drain. Is it pouring of just dripping a little or none at all.
Not sure...


Is the condenser dirty or stopped up?
Condenser is clean and fan is clean.

Is your filter clean?
Filter is clean and replaced frequently.

You didn't say what kind of heat you have, but is your heater running at the same time as the AC?...don't laugh...it happens.
Is the big copper line going to the condenser cool to touch and is the little copper line warm?
Big copper is sweating and cold, but the pipe coming outside isn't hot, prob about 98


Do you see ice anywhere?
No ice anywhere...


Will post more info as I am able.....

Thanks
Craig
 
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Old 08-07-08, 12:12 PM
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14 is a bit on the low side. Where is the furnace and ductwork located?...attic or basement/crawl space?
 
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Old 08-07-08, 12:27 PM
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The duct work is in the attic. The last repairman said that the size seemed smaller than is needed and it appeared to be slightly compressed in some areas.... "The intake was too small and the out-take too large?"

It still does not make since to me though b/c it worked fine last year
 
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Old 08-07-08, 12:31 PM
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Also...The power bill increase according to Ga power is not a result of an increase in energy prices, but to my energy consumption almost doubling....
 
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Old 08-07-08, 12:34 PM
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taking a temperature of what the return air in the attic versus what the return is indoors would be my next step after hearing all else. If it's returning at a higher temp up there, look around to see if something has come apart or was not put together properly and is now sucking attic air.
 
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Old 08-07-08, 12:36 PM
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It would be interesting to know about the condensate. Here we go with theory again, but in order to cool air, one must remove the moisture (dehumidfy) because there is lots of heat trapped in those little droplets of moisture in the air (latent heat). If your AC is spending lots of energy removing moisture, it can't do a great job of cooling until some of the humidity is removed. So, even if the temperature conditions were the same as last year, is the relative humidity higher than last summer?
If the condensate drain is pouring water, your AC may be doing all it can just to remove the moisture.
But, the sweaty copper line and the warm copper line sounds about normal to me.
 
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Old 08-07-08, 12:42 PM
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Ok Craig...the power usage was just an info thing more than a question. You'll be getting plenty of help from the pro's. Actually sounds like the last tech you had out, may have been the best so far.

In the meantime, if you have time in between temp checks and anything else...does the airflow seem to be the same as it always has been? If ducts weren't attached, sealed and taped correctly, you may have something blowing(or sucking) in your attic.
As you said, if it worked ok for a few years, something has to have changed somehow.

Do you have the temp set at a constant, or some sort of programmable that changes at diff times? Sorry, guess I'm just stuck on a thermostat question, since that's what my problem (very similar to your) was.
 
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Old 08-07-08, 02:54 PM
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ac

has any one put gages on it? and ck the freon i read the thread, and did not see this being done. also you stated a 8 degree drop from one regester to another? is it possible a duct has come loose in the ceiling. between the register putten out good and the one with a 8 degree drop would that be a good spot to ck?
 
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Old 08-07-08, 05:52 PM
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Originally Posted by Craigious View Post
I am getting difference of about 14 degree's at the closest vent, so it is blowing out some cold air. There is about a 8 degree difference between the coldest vent and the warmest.


Thanks
Craig

I will post model number info when I get home..
So at some registers you are only getting -6- degrees cooling! Not good. No wonder. Sounds like duct issues.
 
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Old 08-07-08, 08:38 PM
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Savannah, GA, Summer Design 93-dry bulb; 77-wet bulb; 48% RH.

I would buy a low cost humidity gage at a hardware store & keep a close record of your indoor %RH. (Very Important!)

Humidity is an extremely important factor concerning the "Human Comfort Zone," & the SA/RA temp-splits.

In that home 74-F should be very comfortable, it should not require 68 degrees for comfort.

If Techs would follow a proper trouble-shooting sequence they would discover all the things that are reducing the systems performance.

Ductwork & proper airflow is extremely important & must be correct before anything else will be right.

barkleydoggy, is pointing to factors of importance, the condenser is charge temp split tells you if there is too much heat or too little heat being transferred through the condenser
outdoors.

The condenser temp-split also contains both the sensible heat & the important latent heat of condensation. The indoor split contains only the sensible temp-split, the higher the indoor humidity the lower the SA/RA sensible temp-split.

It is easy to locate all the problems if you know the proper sequence trouble-shooting order to follow. - HVAC RETIRED
 
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Old 08-08-08, 07:58 AM
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Here are the specs on the system.
Atic unit Goodman ARUF036-00A-1
Outside unit CPLE36-1A
Thermostat Honeywell TH5220D1003 0741

When looking at the thermostat I saw that no batteries were
installed, so I out in a couple of new AA's before I left. I am not sure if it will matter.

The condenser pan is bone dry.

I would be OK if the house would cool to 74...I had it on 68 last summer bc my wife was 8 months preg and HOT . This summer I am having to drop it down to 67 at night (which it reaches about 69 when the sun comes up) in order to help the house stay cool during the first part of the morning.

The duct work looks OK other than being small sized for the unit, no tears, leaks or any other problems with it in sight.
 
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Old 08-08-08, 08:33 AM
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Originally Posted by Craigious View Post
Here are the specs on the system.
Atic unit Goodman ARUF036-00A-1
Outside unit CPLE36-1A
Thermostat Honeywell TH5220D1003 0741

When looking at the thermostat I saw that no batteries were
installed, so I out in a couple of new AA's before I left. I am not sure if it will matter.

The condenser pan is bone dry.

I would be OK if the house would cool to 74...I had it on 68 last summer bc my wife was 8 months preg and HOT . This summer I am having to drop it down to 67 at night (which it reaches about 69 when the sun comes up) in order to help the house stay cool during the first part of the morning.

The duct work looks OK other than being small sized for the unit, no tears, leaks or any other problems with it in sight.
Not sure if you mean condensate pan, but are you saying there is no water coming from the condensate drain outside and the indoor coil pan is bone dry and you live in Savannah?
 
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Old 08-08-08, 08:48 AM
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Actually I am not really sure....The pan that is under the unit in the attic is bone dry, the freon line is sweating, and there is a PVC pipe comming out of the side of the house that drips...

Also, I just talked to the guy that rented the house the year before I moved in and he said that on one occasion he didn't change the intake filter for months at a time until suction seemed almost blocked.....
 
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Old 08-08-08, 08:56 AM
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Barkley You said it before...and it's been kinda passed over. The way I see it this is a heatpump, right? What about the aux heat, those are strips of some sort, aren't they?

Is there some way to easily disconnect them to rule them out as a problem?
 
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Old 08-08-08, 09:45 AM
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The last repair guy that came out said that the heat was not running at the same time while he was in the attic. He also said that he didn't think that there would be a 14 degree difference if the heat was running at the same time....
 
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Old 08-08-08, 09:51 AM
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Ok Craig...just checking...Someone must have an idea out there...
 
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Old 08-08-08, 10:10 AM
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It is an interesting problem and I'm sure there is a reason(s) for it. Sometimes there are multiple problems that seem to defy physics until you break it down into rudimentary pieces. I don't know if it's within the purvue of DIY but multiple temp and pressure readings, airflow measurements, humidity readings can usually indicate where problems are. IOW, for example, a slightly leaky reversing valve along with a slightly dirty condenser, and higher than normal ambient temps and humidity, along with maybe inefficient compressor valves can combine to cause the unit to not cool well whereas one of those problems alone may go by-and-largely unnoticed.
It may be time for a more in depth and objective look at your system like what Retired HVAC guy was alluding to. You can't change the laws of physics only obscure them.
 
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Old 08-08-08, 10:21 AM
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Craig..just re-reading....you are the owner right? Noticed you said someone was renting before.
 
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Old 08-08-08, 10:33 AM
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Sorry for the confusion....I am a renter as well...The property management is the one who has sent out the service "professionals"....
 
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Old 08-08-08, 07:46 PM
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Craig,

Didn't you say that you had a 14 degree temp differential from one duct?, but up to 8 degrees worse at other ducts? If that is true, why isn't anyone addressing that issue?
 
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Old 08-15-08, 12:07 PM
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Here is where I currently stand...The last AC guys to come out say that the intake is too small for the unit and have gotten permission from the owner to add a secondary intake to increase air flow. This will be completed on Monday. I don't think this will fix the problem as the unit worked last summer with the current smaller intake.
None the less....

It seems to me that mechanically something is not running at 100% and I am not sure how to pinpoint what that might be.

I am going to get the amps tests going into the unit to insure that it is running on 220....

What else can I get these guys to do while they are out that can help pinpoint what the problem is????
 
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