How cold should the air be as it comes out of my A/C vents? It's at 60F, but my A/C has been running non-stop since temps hit > 90F here in Orlando. I'm pretty sure it's a testament to needing more insulation (23 year old house, original cellulose, thin in areas), but I want to make sure my A/C is blowing cold enough air as well.
If you havnt had it serviced recently you will never know if it is operating right. It really is a yearly event. There are a few things you really cant ck . The output temp is only a small part of it.
Maybe you should call a qualified, trained, licensed technician to come out and check your air conditioner over, evaluate its operational performance, and provide you with estimates for repairing any problems that are found.
He could probably tell more about it by looking at it and inspecting it than we can over the internet.
To those who responded to have it checked.. It was checked in October, so it's < 1 year. It got a full cleaning of the compressor coils and needed a little refridgerant. The coil can use a little bit of a cleaning, but the unit is so old, I'm suspecting it will go out entirely, and I wasn't going to spend $300 to have the coil pulled. My main concern is it blowing the proper amount of cold air, which it appears to be doing.
How much air is coming out? That's the question.
Les
It could blow -40C and if its not working right...(and at that temp, it wont be) its not going to cool the home. Design temps play a part as well...if you have a design temp of 89F, anything over it will cause the machine to run non stop to maintain. IF your design temp was say, 90F, with a differential of 20F figured in, then you wont be able to be much below 70F at that temp.
Also, you state you HAD it serviced...well....service is a yearly thing, not when it acts up. IF your tech did NOT check the charge correctly, and just slapped a set of gauges on it, declaired that it needed refrigerant, and did nothing else...its wrong. Even if he added refrigerant, and did nothing else, its wrong. How can I state that with 100% accuracy? Cause thats NOT how you charge a unit...ever. That and I charge them correctly all day long.
Since that is the procedure all the local HVAC contractors seem to use, what is the correct procedure you describe?
Thanks!
Superheat, or Subcool. A good tech can actually charge a system without a manifold gauge. Pressures mean little, give a BASIC understanding whats going on, and are but ONE tool to use. They can show you when you have a valve fluttering, or stuck, but anyone that pops up with a tank of refrigerant, and a manifold and hooks up, throws some juice to it and comes in and charges you for Xlbs of R22, or R410 (Puron) and didnt use a scale for starters, you owe NOTHING. No scale, no way to know if he put in an oz, or a pound. Some, like Goodman on the heat pumps, have a method that words pretty good, and its a subcool variation...you measure the hot gas discharge temps, and normally, IIRC, its 125F above ambient temp and its charged the way they like..
In order to charge correctly, the tech needs to KNOW, and not guess, that the evap and condensor coils are clean, and both fans are operational, and at capacity...meaning, running correctly. Provided that the duct is sized correctly, and there are no restrictions in the duct that would alter the pressure and temp readings, he needs to know the wet bulb temp, ambient temps, metering device type on the evap coil, return air temp, suction line temp, and then run a quick couple of calculations and if the superheat figure that is listed for that particular unit is low, he needs to remove some refrigerant..if its high, add some. Oh..and he cant tell in 5 minutes either...so if you have one come out, and suddenly its cooling again, and hes not been in the house, hes used that favorite method of hacks...beer can cold method....hes when hes normally got the system overcharged, and the suction line starts to sweat like a pig, and then, its cooling...let the temps rise about 15F and then you think you have a problem again.
BTW, I didnt go into tons of detail on the subcool and superheat, as there are about 3X ways I know of to check it, and each unit has the superheat chart someplace on it...it wont have directions on how to check it, since the tech installing, or working on the unit is supposed to know. It varies. Some will argue this, but the basic principle is the same...you are looking to see how much heat the unit is picking up in the evap coil basically in a nutshell...since that is how an AC works...there is no such thing as "cold", just lack of heat. An AC is nothing but a method to move heat. You move it from inside your home, to the outside..the idea is to do it quickly, and efficently. Just because its "working" does not mean its doing it was well as it could, and most people find that after its done right, their bills tend to drop, even if slightly, and the unit makes the home much more comfortable..
And yes, I agree that there is not enough regulation in the industry to keep morons, hacks and otherwise dangerous people like some that actually post in here out of the trade. I dont mind telling you that StorminMoron...(SICOP) is one. Hes a locksmith that tries to be a pro, and he holds no professional licence, since its not required in his state...a shame. That one thing...along with some owners that dont follow up, or train, is what gives the industry a black eye...Mr. HVAC is Fun, AKA Dave, is another one that would like you to think that those of us that tell it like it is, and refuse to sugar coat things is what does...but hes proven unable to be correct, or safe on most of his advice, and refuses to try to listen to those that are proven to be professionals.....no matter if he does not agree with our way of conveying thoughts... If you have a tech that tells you...look, its screwed all to hell, here is why, shows you and explains it to you and you understand and trust him, there is no reason to have a guy that holds your hand and sugar coats the fact that hes about to hit you up for $8900 for a unit that some of us can put in for under $5000.
Added refrigerant? Did they fix the leak first?
You need service.
Today was a worst-case day for heat in Florida. High humidity, sunny,
90s. Your system could be running quite well.Typical hoped-for differential would be 15 to 20 deg F between ambient at the return and output from the vents. If your ducts are in a hot attic, and the house is at 75 deg F, then 60 deg F at the vent is reasonable.
Tip: Hang, permanently, one of those $10 indoor-outdoor digital thermometers from Wal-Mart or Radio Shack by the most visible vent, with the outdoor bulb immersed in the airflow in the vent. I have one permanently installed in the kitchen, which lets me check performance easily. Once you get to know how your system performs under different outdoor conditions, you can check performance any time you like.
Now you're gonna get a lot of cranky advice from all the experts here, about how A/C is too complicated for you to understand and you should just pony up for a service call, but this is one test you can do yourself that is cheap, easy, and impossible to misread.
You'r correct that there are too many untrained guys that have the nerve to work on HVAC systems. If a tech can't show you a superheat chart and doesn't have a set of electronic thermometers to take readings he's not likely to get the job done right. The old time hacks of chargeing to 30 over ambient or beer can cold were never sound methods and are even worse with higher effiency units. Not much has changed to increase effiency but the use of larger coils indoor and out to move heat with lower head pressures and remove humidity better with larger coil surfaces. To get the desirded results the systems must be charged by a trained tech that knows and understands what the hell is going. Even the lowest effiency system useing a metering device subjected to a hack method of chargeing in many cases will cool poorly, useing more electricity and in the worst cases slugging the compressor valves with liquid. I worked for a short time for a small HVAC company were several of their "techs" had no clue as to the proper methods of chargeing a system. They didn't know what a superheat chart was and had no clue as to how to charge to subcool or which type systems used this method. They were easy to spot as the only equipment used for evaluation were a set of gauges and a pocket thermomoter used to measure the discharge temperature of the outdoor coil. When on call I'd spend my weekends removeing refriderant from overcharged systems, that were just serviced. Luckily this type company is the exception to the rule and in most cases will not survive because money lost to improper work. As to trying to dignose a cooling problem with the only know values being the supply temperature, rough outdoor temp and a complaint of long run cycles let me guess it's a high head causeing a high suction pressure or normal if the latent load is high (humidity). Check the compressor to see if there is water running off it from condensation, if so, could be improper charge, dirty evap coil and or fan. All things that should have been noted when it was serviced,
When I had the home inspected by an inspection company, they did as you did. He put an analog temp probe into a vent, into the return, and into the main stack. He said it should be around a 20 degree difference between the air going into the return and the a/c coming out. At the time, I was 25F difference, and he said that indicates a problem. When checked yesterday, it was around 20F. It was 80-81F at the return, and 60F coming out of the vents. So I don't see how it could be operating so poorly. The thermostat in my living room is what decides to turn the thing on and off based on the setting I put in it. So if the fan/compressor cycle on/off based ont hat (which they do just fine), and it's blowing cold air, where else can there be a problem about it not cooling the house properly?
I guess the vents could be too small based on todays code, or not placed properly. But the house in 23 years old, so it's not up to today's code, so what can I suspect?
Or maybe some vents are blocked, I know at least once is in 1 room because of poor placements. But I seem to get plenty of CFM out of the other vents. But I don't know what it's supposed to be.
I'll most likely call my home warranty company and have it checked anyway. >
"Richard J Kinch" wrote
It's not too complicated. It is more complicated than an indoor/outdoor thermometer. They are called air conditioners, not air coolers for a reason - your idea doesn't leave much allowance for latent heat. The simple thermometer is good for a quick glance reference but is about as accurate as trying to back up 4 feet using your odometer.
- Robert
Correct. I also occasionally use a sling psychrometer if there's any doubt. A little harder for the do-it-yourselfer to find, but not expensive, or you can make your own.
Thank you. :-)
- Robert
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