AC question

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I have lived in this house since it was new, 20 years ago. This past week, during the late afternoon, I would get condensation coming from the air outlet closest to the air handler and right after the coil. I remember reading on this group that this is probably caused by icing of the coil. remembering that low air movement across the coil could cause this, I changed the filter and this time used a filter that would allow more flow ( I had one of those super duper ones that wouldn't let any pollen through). For the next day or so, that seemed to fix the problem. Now today, It has started again. I turned the AC off for about an hour, then turned it back on and no more condensation dripping from the outlet. I know, however, that it will probably return in another couple of hours. It is presently 100 degrees outside. The humidity is about 40%. Inside the temp is 77 degrees with a humidity of about 33%.
This is the situation. The compressor is out side. Everything else is inside in the attic. Over the life of the AC, the filters have NOT be changed out on a regular basis. For the first 15 years or so, I used the el-chepo filters. Usually, when I did remember to change them, they were clogged up with dust. Last year I had someone come out to do a checkup. This was the first time in about 10 years. He measured the flow from the vents and used the gauges (I have no idea what the measurements were but he said the readings all looked good). He also checked the temp of the air coming out of the vents. All was good for the unit I had. He of course tried to sell me a new high effency unit, but when we finished talking, the payback would be after I was dead.
So now I'm thinking that one of two things is wrong. Either the coil is clogged up and won't allow enough air to flow through the coil and it therefore freezes up, or the freon level is low(?). There seems to be good air flow coming from the vents and the air is cool, but can the air get around the coil? Or is it possible that some of the coil is clogged and that's where the ice starts to form, and then it just gets worse from there?
I know I'm going to have to call an AC guy out, but I'd like to have an idea of what else the problem could be.
Thanks.
Dave
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I have a 2000sf home but I am shutting down the vents in unused rooms and have only 1400-1500sf to cool. The AC unit is scaled for 2000sf (4 ton unit). Does closing off the vents reduce the efficiency of the AC? Will it cycle more and thereby use more power?
Thanks Art
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This is Turtle.
You really need to get the sizes of the duct your cutting off and get the C.F.M. that your cutting off to get it right.
Now to a rule that may work or not but has been used for many years.
Never cut off more than 1/3 of the vents of your home. If you have 3 cut 1 , 6 cut 2 , 9 cut 3, 12 cut 4.
Now to the efficent operation of the equipment at this condition, Well your cooling a lot less space and would seem to cost less. With 1/3 cut off I would not think short cycling would become a factor.
Yes i cut vent off for a living.
TURTLE
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AR wrote:

It will probably cycle less, which may lead to unwanted humnidity problems, but it will probably use less power.
--
Robert Allison
Rimshot, Inc.
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AR,
Don't close the vents!!!!! You won't save money and with the lowered air flow, there is a chance you won't boil off all of the refrigerant in the evaporator coil. when liquid refrigerant gets back to the compressor it can wash the oil out of the bearings. It can also blow the valves apart as LIQUID refrigerant is not compressable. doing anything to lower the air flow will reduce the efficiency, may freeze the indoor coil and can daage the compressor. letting your filter get dirty can have the same effect as can using pleated or washable one inch filters.
By the way, my 2000 square foot house has a properly sized unit which is 2-ton. I did a load calculation to determine what my house actually needed instead of using a 50 year old rule of thumb. That rule of thumb started when there was no insulation in the walls or ceilings and single pane glass was the norm. Depending on where you are, your system may be way oversized.
Stretch
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ups.com...

way
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I made an assumption regarding the size of the AC unit and I was wrong. I do have a new home with all the engery things and the AC unit is a 3 ton based on my research of the model number. I live in the Boise, Idaho area and July and August are the hot months, high 90s and a few 100s. It does appear at this point it would be best not to close off the vents. Thanks to all for your replies and suggestions.
Art
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It will definitely save you money on your power bill. A couple of points though.
1. If you shut off too much of the house, then the inside coil will ice up.
2. The overpowered unit will not run long enough to dehumidify the air so you may notice a cold muggy feeling in the house. And all the other things that go with high humidity such as mold and mildew.
Since you obviously trying to save a buck, let me suggest something that worked for me.
Although I have a nice Trane central air and heat, I purchased a small 6,000 btu very high efficiency window unit (11eer) and placed it on the wall in our master bedroom.
It does an excellent job of removing moisture from the house and also keeps up comfortably cool while in the bedroom. My outside unit hardly ever comes on except in the very hottest part of the day.
The best part is that my summer electric bill went from over $300 to $175.
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I cut down in a similar way by closing vents in unused rooms on a 4000 sf houses upper AC unit and the blower motor failed ( cooked) the second year. I attributed to the increased backpressure with so many vents closed . Does this make sense ? Bob
wrote:

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BoborAnn Wrote
I cut down in a similar way by closing vents in unused rooms on a 4000 sf houses upper AC unit and the blower motor failed ( cooked) the second year. I attributed to the increased backpressure with so many vents closed . Does this make sense ? Bob
Heat is usually the culprit in motor failure. When you reduce the air flow, there is less air flowing over the motor to cool it. I have been to many motor seminars and the manufacturers will tell you reducing the air flow is a major cause of motor failure. The motor amps go down slightly, but the cooling air flow is reduced more. The result is premature motor failure. The backpressure is not a problem.
Stretch
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i was thinking like stretch , that to reduce air flow may cause problems, closing off rooms for heating is different and can save money and still work good. but max air flow over the evaporator while cooling is important. lucas
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Check your t-stat settings as well
When a unit stops working: say from the filter and someone will usally turn the t-stat down thinking that will make the air colder. That will also ice up the coil as well and since you changed the air filter it may have started working again but now it is to low.
Just a thought
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A call for cooling (when the room is 79 and the stat is on 76) is exactly the same as a call for cooling hwen the room is 79, and the stat is set for 58.
--

Christopher A. Young
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Dave...first of all....ignore the comment about the stat being too low...turning the stat too low on a properly charged system does NADA...the system knows only on, or off, and going too low will NOT cause freezing on a properly charged and operational unit in summer temps...PERIOD.
Now, you probably answered your own question, but its impossible to see it from here, however, your lack of normal service is screaming clogged coil....DO NOT LET YOUR AC GUY PUT ANY REFRIGERANT IN THE UNIT TILL HE INSPECTS THE COIL!!!! Most guys will come out, with only a manifold and a nice green tank and start juicing the unit..they never go inside, never take a lineset temp, never take a RH% reading indoors, never get a dew point...never do any of that and start to overcharge the unit, and then, WITHOUT a scale, they start to dump refrigerant into the unit and then, with NO WAY to know what they put in the unit, they proudly proclaim its working, and charge you for 3lbs of refrigerant that they got for next to nothing and charge you $45 a lb for it. Low airflow across the coil, due to dirt, mold, etc, will cause the pressure readings at the manifold to be, or appear low. (BTW, those pressures...mean NOTHING to a trained tech...hes looking for temps anyway) A dirty blower wheel will cause the same thing due to lack of airflow..lack of airflow, means lack of heat being transfered to the coil, and thus, lower pressures. IF the units not been serviced, its worth your while to get the evap properly cleaned, the condensor properly cleaned, and THEN have the tech look for the issue..chances are, if it is low, and the ONLY way hes gonna know is to check the coils, clean the coils, and go inside and take temp readings for starters...then its got a slow leak. Any legitimate company will check the coils while they are servicing the unit for leaks..and use a detector thats of decent quality...not soap unless its a question of moisture setting the detector off..and if hes got a decent one, like CPS, or LeBold, that wont happen anyway. 9 out of 10 leaks are at the service ports and can be repaired in seconds, not hours normally.
Now...things you want to see..
1-Checking the evap coil, and cleaning if needed. 2-Taking temp readings of the suction line and return air temp indoors BEFORE adding a damn drop of refrigerant. 3-a SCALE under that green refrigerant jug, so he knows EXACTLY how much he put in.... 4-a leak check if he adds any refrigerant.
You will want to ask him how hes gonna check the charge, and if he says, by pressure, you can tell him to get on down the road..superheat, or subcool, and HE wont know till he checks your metering device in the evap.
Now...if you want a gas-n-go.....then let him do whatever he wants, and dont do anything but pay him whatever he asks...LOL
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Carolina Breeze HVAC wrote:

You should save this one as a template. Will save retyping it over and over. Very thorough.
hvacrmedic
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Carolina Breeze HVAC wrote:

DO NOT LET YOUR AC GUY PUT ANY REFRIGERANT IN THE UNIT TILL HE

they never go inside, never take a lineset temp,

with NO WAY to know what they

negative energy to get here. If anyone got this far. It's clear that your main game is critizing others.

everyone to get here.
You should save this one as a template. Will save retyping it over and over. Very thorough. CY: Highly negative, and very insulting of every other tech. Why would anyone want to repeat a bunch of insults and putdowns?
hvacrmedic
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Here is a fourth in a hurry for ya Chris...what fucking brand of megger do you own? How do you check compressor windings? Your own words were....you know nothing about those....and you claim to be a tech....lol...

You stupid incompetent moron....suggest you learn how to read....that wasnt negative..this is....you are impossible to train...

Ummm...no. Its negative to your type..the untrained, unwilling to learn kind that isnt licenced....and has admitted to putting used parts on your so called customers units.

No...thats a fact, and I bet I nailed you on the head. What brand and model scale do you use Chris?

I read that I just nailed how you charge a unit.

Whassa matter Chris? Really pisses you off that you have been called out time and time again, and now, your charging techiques have been uncovered?

No...just putting the hacks out....get used to it bubba... See Chris, the bad thing is that there are people out there like you....the average homeowner has no clue the things that need to be done, so when someone like you comes out, they think, wow, hes got it running...and all you did was keep them stupid to what you did...need I remind you about your capacitor story???? Educate the homeowner, the hacks will find other avenues.

You learned something? Amazing. Shame you continue to lie to everyone....more negative energy that I am positive about.

Another pro, (something you are not even close to) thinks its ok...deal with it Chris. Wait till the vid comes out that we are gonna offer...its got guys like you that we taped working on units, and then it shows the RIGHT way to do what they lied to the customer about.
BTW Chris..for someone that claims to be a Mormon..that sure was a very un-moron..err..mormom post you made there.. Dont mind if I send it to the local Mormons in your area do you? Ill also include your most recent post about how you cheated and admitted to us all how you cheated a customer by installing used parts on his unit in the hopes it would run, and how you KNEW you had a GUARANTEED return visit you could charge for.
BTW..glad you cross posted this to alt.hvac....the guys there will have a field day with you...

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Carolina Breeze HVAC posted for all of us... I don't top post - see either inline or at bottom.

balance. It's in the back of the Pinto somewhere bent like a pretzel and due to be recalibrated 75 years ago...
--

Tekkie


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That's better than the one I have in my bathroom. Mine just says "one at a time, please" when I get on it.
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Generally, people with jobs don't spend this much time on the computer. I don't have the time to rebutt each and every accusation. Why don't you make some more vicious accusations? You sure are revealing your true personality.
--

Christopher A. Young
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