I have two central ac units for my house in central NJ. The downstairs unit as always worked fine, but not the upstairs unit which is approx a 100,000 btu unit. I decided to start looking in to it and noticed that the evap coils are not all cold with the upstairs unit. Maybe 1/2 to 3/4's of them are cold and sweating. The suction line doesn't sweat on this unit, but always sweats on the downstairs unit back to the condensor. So, what are the possible reasons so that when I have somone take a look, I have a bit more understanding/knowledge. Thanks, Ben
Why do you need to understand it unless you're thinking you can fix it yourself. Since you've had the cover off already, I'd say it's a safe bet that you're just wanting a freebie. If you just have to know, there are precisely two possible reasons for what you're seeing:
1) Undersaturated coil.
2) Nothing wrong at all.
There are a ton of specific reasons that #1 can occur, and keep in mind that not all of those indicate a problem with the system itself.
Which of those possibilities do you think we should pick right out of our ass for you?
Wow.... I never imagined what I thought would be a simple quesiton would invoke so much hostility. You asked: 'why do I need to understnd it unless you think you can fix it yourself. I'd say it's a safe bet that you're just wanting a freebie' I wanted to understand because I never thought this system worked correctly. It never cooled well. Was never able to keep up with cooling on hot days and taking a long time in the evening, after the sun went down, to bring the room to a comfortable temperature. So what if I did want what you call a 'freebie' ? Or, what if I just wanted to have a better understanding so that I wouldn't need to take the word of a disreputable repair person, which I have seen plenty of
Maybe thats because you used the lowest bidder instead of looking for a top quality installation of top quality equipment by a master technician. Its hard to remember the sweetness of low price when the bitterness of poor quality remains.
If you want to understand, then I suggest a local community college. If you want it fixed, then I suggest you call a reputable service company. If the guy is willing to give you a lesson in hvac while he's there, then you're in luck on both counts. BTW, the previous post wasn't hostile, it was sarcastic. If you don't understand why some of use get cranked up every now and then, then its because you don't have to deal every day with people who think that every problem with a unit is written on some little list that we are given to memorize by our bosses. Contrary to your opinion, one observation doesn't automatically tell us what the problem is anymore than an MD can tell you what's ailing you without performing a few tests. Patient calls the doctor on the phone-- "Doc, I'm nauseated, can you help me understand why that is without me coming in for a checkup"?
I think I could understand the difference. Mo Hoaner's response was Sarcastic. Fair enough.... If I didn't supply enough information, my fault. Maybe a simple response like, you didn't supply enough info or what really needs to be done is a Service Tech, needs to hook up gauges to check the pressures to see if there within spec. Or, cut and past a dozen questions that you might ask all the time. So I guess what I see here is that all the coils not being cold, might or might not indicate a problem. Right now I'm leaning towards it being a problem and will have someone come out and take a look. All I was trying to do is to understand if my unit is working properly or if I should have someone come in to take a look or would that in itself be a waste of a hundred bucks.
In that case, yes you should have someone competent take a look at it. If it isn't keep up with the load, then there's definitely a problem. OTOH, there is nothing we can say that will help you understand, because we don't know ourselves what the problem is. Fair enough?
My last post.... I find it it very interesting there seem to be so many frustrated people adding to this forum. Why are you even answering at all? If you are so fed up with answering what you think are stupid questions, don't answer. One day you will need someone elses advice, auto mechanic, Lawyer, Dr. I don't care. I only hope they respond to you in the same professional and curteous manner.
"Noon-Air" , frowned down from the pulpit affixing the Mighty Eye of non Halogen Gas at the boy who asked for more pie:
/cut
oH pHuck..puuuuuuuuuuuurLeeeese!! What is it.. Pentecostal Sunday in a.hvac Land !! "Master Technician" indeed !! I will bet you have A/C in that Hummer (the one with the twin valved Magnum Pods mounted over the cow catcher) cos sure as hell if ya'll had to ride that White Horse to a call... ..well ya'll be nekkid when you got there. The tickets would have all blown 0ff !! LMAO
Ben, you are very correct, one day more than one of these hacks will need the aid of Professionals. Some who are no longer with this Group have already discovered that truth.
Your query is valid, sift through the responses if you have time to waste, however your best option is to do some smart investigating yourself. Too many of the hacks here collect a hundred bucks for merely trimming the hedge around your outdoor unit, for instance. Check: #Fans are all turning with correct rotation and are at speed. #Check for obstructions in ductwork adjacent registers and at the indoor coil/head. Places obstructions could impact are at "filters/ "dampers"/"splitter boxes"/access panels and drains. I use quotations so you can go check on the NET for what these devices actually look like. You are looking for any breakdown of the enclosed air space which feeds each outlet. This includes "illegal" openings and squashed or collapsed duct, busted drains. Look carefully, I have heard squirrels have strange mating habits Check _both_ systems at this level. You can then compare "apples with apples" relatively.
#Next, get two $2.00 alcohol thermometer from the local Walmart. Prepare a glass of ice and fill it with water and stir. When the glass is sweating externally drop the thermometers in it and stir. Wait maybe 1 minute and check the reading on the thermometer. They should be close to 32°F/0°C. Note any difference as a factor for later calculation. Now, find two testing points either side of the indoor coil/head. "Air in" and "Air out", basically. Adjust the unit so that the fan speed is around "medium" and take the two readings. You should allow some two to three minutes for that operation. Compare the readings and get a figure as a differential (deltaT). Do the same on the other unit. Should all be working well and the installed design be reasonable (in line with the load) both differentials should be within a degree or so of each other. The actual number depends on a number of factors , typically you could expect maybe 18°deltaT using Fahrenheit scale, 10°deltaT using the Celsius scale. IF the numbers are well apart in likeness or _neither_ falls within that ballpark range of deltaT, then, you do have a problem.
#Next, take a sheet (canvas preferably or cardboard) and design it to fit the inlet side of your coil/head so it covers the entire inlet face of the coil/head. Do I have to say the unit has to be "0ff" while you set this up? Once you have something that works as a "block", quickly.. remove it. Start the unit and allow it to run until you can see the first row of headers begin to "sweat". Apply your "block" now. Within maybe two minutes the whole of the coil should be saturated and all headers sweating, some may even begin to form a hard ice/frost. If the whole of the headers are equally covered in sweat then you can be reasonably certain there is no refrigeration problem of any great magnitude. Do _NOT_ fall asleep whilst doing this..or go answer the phone. You _must_ be in attendance for the whole of the test. Once the return pipe to the outdoor unit starts to sweat vigourously you have to remove the block, and this is where the original design is important, do not turn the unit "0ff" to remove the block. The unit must be allowed to run to "clear" the coil/head.
#When the indoor coil test has not met the conditions described you best get outside and do another general check around the outdoor unit. Look for any dust impregnated oil stains on pipework and make sure the fan and outdoor coil are not blocked with debris. Nothing obvious? Call your competent HVAC&R guy and let him run. Do not make the mistake of saying "I checked this and looked at that". One, you will maybe sidetrack his process of analysis, thereby doing yourself a disservice in the checkbook. Two,at worst you could have one of the hacks from here and thus "piss him off", bigTime
Any information you discover could help you later so make sure you record readings and observations. Field guys do this all the time so as to build up a knowledge base. You could learn by following that attribute of the Trade.
Whatever you find do not bother returning with a post saying "I found this, what now". I have no problem helping with what you originally asked, however I am a Professional (ret), therefore I can respect the need for the Industry to have its quaint ways. Besides, you have probably have had enough of the pranks these guys pull, on line.. if you are a genuine self helper. Thank you for your post. I did find it refreshing, in this place :)
My last post.... I find it it very interesting there seem to be so many frustrated people adding to this forum. Why are you even answering at all? If you are so fed up with answering what you think are stupid questions, don't answer. One day you will need someone elses advice, auto mechanic, Lawyer, Dr. I don't care. I only hope they respond to you in the same professional and curteous manner.
An Eight (8) Ton A/C for the upstairs of your home in central NJ with a similar Summer Design to SW WI? Is the upstairs level 4,000 to 8,000-sq.ft., how high are the ceilings in the rooms? Was a Manual J performed to indicate the heat-gain?
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