AC Problems - Time to Replace?

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  #1  
Old 06-06-02, 09:49 AM
L West
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Unhappy AC Problems - Time to Replace?

To give you a little background, we bought a two year old 2200 sf house (one story w/ bonus roon on a basement) a couple years ago in GA that has a 3.5 ton Rheem 10 SEER outdoor unit, an 80% furnace made by Consolidated with an no name 4 ton evaparator coil. The ductwork is ran in a "spider" configuartion vs. a main trunk with branches. Already sounds like crap huh.

The first summer we found that on 90+ degree days that the AC would not cool the inside below 80 degrees despite the AC running non stop all day long. We started checking into the system to find things like the return ducts not being sealed where they were attached directly to the side of the furnace cabinet. You could literally stick your finger in the openings which explained while pieces of insulation were being blow out the supplies in the house! Anyway, we sealed all the openings and installed an attic vent fan to help cool the attic and had the system checked out which required adding freon. It worked OK afterwards and last summer wasn't too bad.

We had the unit serviced in April to make sure everything was OK for this cooling season. The service tech mentioned that the compressor was pulling more amps than normal and that the warranty will expire this October. Other than adding some freon that all was "OK".

After the service visit when the AC would start the outdoor unit would make a horrible roaring sound for the first 30 seconds or so. We called the folks who did the service to come back and check it out. I wasn't home and not sure what they did. I did notice what looked like oil on the ground behind the outdoor unit and also in the attic floor near the furnace / evap coil.

We had our first heat wave the past week. One day when the outside temp was about 92 the house never cooled below 78 ( we find it comfortable at 76) Again the AC unit ran non-stop from about 10:30 am until almost midnight. So we called and asked for a tech to come and and check the system.

The tech evacuated the system, removed the evap coil, did something with nitrogen and recharged the system. He tells us the problem is with the evap coil not converting the freon from liquid to gas and that we need a new coil. He also says the coil design is ineffcient (an "M" shape vs. and "A" shaped coil). The service tech quoted a new evap coil at $850. Does this make sense considering the system is cooling the house on days with moderate outside temps?

Also, I'm wondering if whatever it was that happened at the first service visit that caused the unit to make the loud roaring sound at start-up damaged the evap coil?

I'm thinking I may be better off to replace the furnace, evap coil and outdoor unit and maybe the ductwork too with a more efficent and possibly larger system since the outdoor compressor is already pulling more amps than normal and the diagnosis of a faulty evap. coil.

I'm thinking maybe a 4 ton 12 SEER AC and a 90% Gas Furnace. Perhaps then energy savings will offset the monthly payments of the new equipemnt ( I can get a low interest loan from our local EMC).

What do you folks think? Any of this make sense?

What's you thoughts on Tempstart equipment?
 
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  #2  
Old 06-06-02, 01:01 PM
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Last edited by jonathanisaac; 08-03-06 at 07:51 PM.
  #3  
Old 06-06-02, 01:07 PM
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TIME TO SUE!!!!!!!!!!!

You must contact the original installer and tell them to make it right, 100% or you will take them to court!!!!!!!!! A 2 y.o. system should not have these problems!!!!!!!!!

Now,if you contacted the auto forum on DIYS and stated the following:::::I bought a brand new car 2 years ago---it has broken down 3 times.I get no heat out of it in the winter,the a/c does not work in the summer,there is oil all over the engine,etc,etc,etc----what do you thing they would say???? P.S. Don't be afraid to go after the G.C. who is responsible for all work.PDF
 
  #4  
Old 06-06-02, 02:10 PM
L West
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I actaully thought about legal action at one point. The house is about 4 years old. We bought it two years ago. I don't know how to find out who the orginal installer was. I though about going to the county building department and looking at the permits / inspection records. My guess is the installers argument is that "the county approved the installation" and "you bought the house from the orginal owner as-is"... blah, blah blah.

I had a home inspector check out the house before we purchased it, who apparently didn't know much about HVAC systems. He did check the air temp at the returns and checked it off as being OK.

My advice to others... have a HVAC pro check out the system before you buy a new or pre-owned home!
 
  #5  
Old 06-06-02, 03:16 PM
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Go after the

home inspector.Is he liscensed and bonded?Is he registered with the state in which you live??You are on the right track.Use your phone and find out whom is responsible.Almost bet you they have other law suits pending.PDF
 
  #6  
Old 06-06-02, 09:55 PM
ahasbeen
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Yep, you've got a couple problems. I'd try and go after the home inspector or perhaps some other legal means but it may be a lost cause since the unit is 4 yrs old. Not sure, but try anyway. First off, no a/c system is any better than its duct system. Its 50% of the cost and 100% of the satisfaction. You might want to get the best duct contractor and let them have a good look for recomendations or a better design. As for the compressor noise (30 seconds), .....slugging from an overcharge. The oilly ground and oil spots at the ahu are probably from dumping some refrigerant which is saturated. Its possible your captube is plugged but doubtfull on a 4 yr old unless its been opened up and the system had moisture introduced. If your "M" shaped coil is what I think it is, its a dog. If you're losing freon, have it leakchecked and repaired. By the way, if a tech removed the evap, reinstalled it and used nitro, thats fine to purge a system, but you better remove all of the nitrogen b4 rechargeing. Using a 4T coil with a 3.5 T CU, if fine. Compressors can handle it without excess amperage, providing everything else is up to snuff. Normal compressor amperage is varible depending on load conditions and should be kept at or under the stamped nameplate RLA (running load amps). Before running out and changing to a 4T, have the ductwork checked out for leakage, blockages or anything that would restrict air flow. Hopefully the ducts were sized for your a/c system correctly. Check around and get the best licenced a/c tech around. You may pay more but it will be worth it.
 
  #7  
Old 06-07-02, 05:42 AM
L West
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Question

Here's the report from the service tech on my AC problem (doesn't cool house below 78 on 90+ days / works OK otherwise) He says I need a new evap coil. Opinions please?

1) System returning liquid to compressor
2) Pulled evap coil = clean
3) Evap coil is M-style 3-1/2 tons
4) Pump freon down
5) Remove piston and clean
6) Pull vacuum
7) Re-charge system
8) Still pumps liquid back (flooding)
9) Evap Coil is bad
 
  #8  
Old 06-07-02, 12:10 PM
ahasbeen
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Flooding??? Its not the coil's fault Its either the wrong size piston or its not seating properly.
 
  #9  
Old 06-07-02, 01:14 PM
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Last edited by jonathanisaac; 08-03-06 at 07:51 PM.
  #10  
Old 06-07-02, 01:37 PM
L West
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Can the piston be replaced instead of the whole coil?
 
  #11  
Old 06-07-02, 01:42 PM
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Yep

It's too bad.When he had the piston out he could have called for the model coil and the right piston size.Usually the number is stamped on it.I do alot of refrigeration work.Manufacturers sell you an evap. coil for a walk-in cooler.The evap. coil will contain,in a package,3 orifices,pistons or as Carrier calls them "accuraters."Normally they will cover the range of use for R-416a,R-408a,or R-22.....It MUST be the correct one or flood back will occur---or the coil will be "starved" for refrigeration.You want to talk about a "nightmare." Go on a job with the wrong piston in it(installed by another company) it will drive you crazy.It may be possible that your air flow is real bad.Remove all supply duct work.Start unit up so there are no restrictions to air flow.If unit does not flood back,air flow could be the problem.Make sure your return air also is not restricted.PDF
 
  #12  
Old 06-07-02, 01:43 PM
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Last edited by jonathanisaac; 08-03-06 at 07:51 PM.
  #13  
Old 06-07-02, 06:47 PM
RichO
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Me too please,what are you refering to when you say "piston"
 
  #14  
Old 06-07-02, 06:59 PM
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a piston

is the metering device, literally a tiny bullet shaped piece of brass that has been machined to fit into the liquid line at the entrance to the evap coil. it has a tiny hole drilled through it that acts to spray the refrigerant into the evap coil. this hole is a different diameter depending on the tonnage of the unit. generally outdoor units come with the orifice/piston to match. does sound like a piston problem if units capacities are matched. what are superheat and subcooling temps...these tell exactly what the coil is doing
 
  #15  
Old 06-07-02, 07:54 PM
RichO
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I was a little confused with the terminology"piston"We usually call them TX valves,or depending on the type AX valves(unless this is something I'm not familiar with).
 
  #16  
Old 06-08-02, 11:18 AM
lynn comstock
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Don't Replace it...Fix it.

I agree that the metering device is not working properly and the system is flooding the coil and compressor with liquid refrigerant. This raises the coil pressure and temperature (reducing capacity and efficiency) and is potentially lethal to the compressor.

The metering device works for a heat pump or an air conditioner. In cooling the piston moves to force the entire liquid refrigerant through an orifice hole drilled down its centerline. In the heat mode the indoor coil piston moves and becomes positioned so that the liquid can flow around it without much restriction.

Either way, at this point replacing the piston with the correct size should correct the problem.
***********************************************
Don't consider a bigger air conditioner. The average air conditioner is 50% OVERSIZED. Small air conditioners are RARE. Big air conditioners with problems are common. The industry habits hide many of the problems from discovery. The system does the job, but the waste is enormous.
SEE:
http://homeenergy.org/archive/hem.di...96/960907.html
 
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