Central air not cooling - what to ask tech?
I know this is not a DIY job but, as a single woman, if I'm not slightly informed, techs will rip me off. Certainly not all, but it's happened many times. I've talked to three this week. When the first one came, he put in 1 lb of freon and then tried to sell me a new unit. 2nd one never called me back. Diff websites have helped me a lot, just to know what to ask for - like checking the temp at the vent.
The air temp coming out of the vent was only 7 degrees lower than the actual room temp. The first tech put 1 lb of freon in it but that did nothing. I got another tech to come and he cleaned the coil and said that if that didn't work it might need to be "weighed back in" --- something like there might be air in the freon and it needs to be emptied, vacuum the air out, and then refilled --- or maybe it was moisture instead of air ... IDK. He was planning on doing this on Monday, if the coil cleaning didn't work. It's MUCH worse now. The air temp has only a 3 degree difference now, and I think the outside unit sounds "different" than what it did before. I might be wrong though and just looking for things. I just turned it off today, but it is HOT (90) and going to be a long weekend!
Things I did b4 I called a tech: the filter is only a few wks old (changed monthly) and I tried turning it the unit off for 10 min and then turning it back on to reset when this first started and that didn't work.
I like the last tech that came out, even though they asked me if I was married when I made the appt (what does that matter??). He seems to be going in the right direction, but he did comment on how I knew as much as I did (and I don't that much). I told him I had electrician friends in another city LOL.
Right now, the freon is full, the coils are clean, there's no ice anywhere, and the unit is 9 years old. Oh, and I remember him saying the pressures were good (didn't really understand it, but he said it).
A retired electrician friend of mine told me to have him check for a "blocked screen" b4 he dumped (vacuumed, refilled, weighted --- whatever it's called) the freon. Anything else you can think of, or anything that I should be sure to ask him about would be greatly appreciated. Sorry if my explanations aren't good. Since I'm not a tech, techs try to tell me things in laymen terms that often don't make sense when I try to tell it to another tech.
sounds like a possible overcharge if he added more refer and it decreased efficiency IMO
tell him to varify airflow,then charge via superheat subcool method.....................
p.s. are you married...........LOL,JK
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You need to tell the next tech that comes out exactly what you said in your post. Especially the difference in the sound that it makes. Make sure he does a thorough inspection of the entire system. ( indoor blower, evaporator coil, & filter for airflow as well as refrigerant pressures, compressor, condenser fan motor and all elecrtical supply and components). Good Luck
He should not check freon just by pressures. Superheat/ subcooling is the correct way to charge a system. Sounds like you need a new tech. Of course, after the other tech cleaned the coils, the freon needed to be checked again, because the heat transfer is different.
Remember, Air Conditioning begins with AIR.
I agree, Kevin. Sorry to have omitted that peice of information.
Originally Posted by Kevin O'Neill
Originally Posted by HVAC2B
It didn't make a bit of difference when he added the pound of freon. That guy ... I don't even know if he did anything honestly. He said it was low. I asked him how low. He said, "What?" I said, "How many pounds does it need?" Then he said that he was putting in a pound. He was more interested in selling me a new unit.
I think he did "verify airflow" - he said that air was coming in (tested it at the bottom) but said it wasn't spitting it out at the right temp (tested it in the vent). I know the vents all blow air out well, just not cold enough.
I don't know what "charge via superheat subcool method" means. How can I ask him that like I know what I'm talking about? LOL
PS---I'm taking husband applications as we speak, only HVAC, carpenters, and auto mechanics need apply LOL --- J/K
The difference in noise......Louder of more quiet?
Originally Posted by Kevin O'Neill
Okay, that helps. I know that he did check the freon after the coil cleaning. He said it held 4.75 lbs. So, he said that he'd "drain all the freon out, vacuum the system to make sure the air was out, and then refill it, putting exactly the same amount back in." Does that sound right?
I'll ask him about superheat/subcooling b/c several of you are saying that but he didn't. But, he may have and just told me in different words. I know he did have a lot of little machines and hooked them up to various places on the unit and then told me that it was registering fine. I assumed he was checking electrical stuff.
This is just a guess from here, but a 3-F drop sounds like the blower way be sucking hot air into the Return Air! The system is probably way over charged with R-22, because they were trying to get the suction line beer can cold!Could also have way too much airflow.
Below is one of my trouble shooting lists, copy the data portion into your word processor & make hard copies it.
Snail mail or email the list to the local contractors, & then when you call them, ask if they are willing to do the diagnosis with you keeping the data, then you might get a tech that knows how to diagnosis a system!
If he/she they can't do most of them or don't know what they are, well, that is a problem.
TROUBLE SHOOTING DATA
Age of unit, Tonnage & SEER Rating ________
Square Footage of home & major city near you __________
Out-Door temperature: ______
Outdoor condenser’s DB discharge-air-temperature _____
In-Door temp DB and WB: ___________
Total-ESP/ air flow in CFM: _____
Suction pressure ___________
Suction-Vapor line temperature: ______
Head pressure ______
Liquid line temperature: ________
Superheat & Subcooling: _____________
RETURN AIR TEMP just ahead of the blower (Hot Attic Air) _____________
Return air temp DB and, WB, or %RH: ____________
Supply air temp DB and, WB, or %RH: ____________
My advice: get a low cost humidity gage at a local hardware store & see what the percentage-RH is in your home, I can cross-reference that to the wet bulb depression.
Then, perhaps we can provide a ballpark opinion on how well the system is performing. External Static Pressure (ESP) Testing:
Superheat & Subcooling:
Print those pages for yourself & for them too.
The problem is either in the refrigerant system or the airflow system, the data will tell us where the problems are located.
Tell them you have a relative (I am your spiritual brother) that is an HVAC Tech.
Last edited by udarrell; 06-28-2008 at 07:57 PM.
Reason: Suction & head pressures - & Location of problems
I'm not really sure. I almost think I was just freaking out, afraid I was hurting it by letting it run. It just seemed different. You know how it kind of hums, like you can hear a machine down there or something? I think the fan was louder, like all I heard was fan and not that little hum. I didn't think the fan was moving as fast either. May have all been in my head though.
Originally Posted by phbsales
Sounds like the compressor may not be running. If not, have the tech check compressor leads, capacitor, etc. Then have him check pressures, superheat, and subcooling.
Originally Posted by kentuckycuz
Originally Posted by phbsales
I thought that if the compressor wasn't running, the whole unit would shut down, so that may very well have been the difference. It was 90 degrees today and the unit only got the house down to 86. I finally just shut it off and opened the windows. It got up to 88 in here and still is 88. We just had a storm which has remarkably (God is watching me :-) cooled the outside temp down to 73. The house is still 88! Should I turn it back on? If it could pull the outside air in, that would get the house down to 73 wouldn't it? Or, is my thinking backwards?
Opening windows might not be a bad idea. Cheaper than overtime rates (jk we need to make a living too). Anyway, it IS possible, without going into great detail that the fan may still run on the condenser w/o the compressor running (capacitor, internal overload on compressor). Best thing to do is shut it down, let it cool off if it is the overload on the compressor.