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  1. #1

    Unhappy Liquid Line Restriction, Need New Evaporator Coil?

    Hello all!

    I just had a 'professional' come out to the house to inspect my A/C. I live in a 6 year old house that has a 3-ton Carrier condenser on the side of the house, which is 1996 sqft. I have been getting around 60 degree air coming from the vents in the family room but about 73 degree air coming from the vents in my bedroom.

    So, the pro comes in, checks around the house, then goes up to the attic and doesn't report anything wrong. Then he goes outside to the condenser and gets a suction pressure reading of 80 and a liquid pressure reading of 315. From this, he tells me that i need to spend a boat-load of money on a 4 ton evaporator coil with TXV in order to fix the problem, and I need to do it now before my condenser gets ruined.

    Am I getting hosed here? There has to be something that can be done to reduce the liquid line restriction without replacing the evaporator coils, no?

    Any help you can give me would be appreciated!

    Thanks,
    shanebo2003

  2. #2
    Join Date
    Nov 2003
    Location
    Rochester, New York
    Posts
    392
    Hard to say whats really wrong without readings such as sh,sc,dt but i'm willing to bet that the problem isn't the evap coil. Maybe clean the condenser first to bring down the head. Whats the ambient oa? Temps inside? Ask them if they took these readings. Then run to another contractor.

  3. #3
    Join Date
    Jun 2008
    Location
    phoenix az
    Posts
    24

    yep, getting hosed

    sounds like to me your gettin hosed. did this so called pro only recommend replacing the indoor coil or did he mention the entire system? from your posting it sounded like he only mentioned the indoor unit. sounds like to me what you need is a new load calculation done on the home. have you added any new room additions? your system is most likely not sized properly. and if it is, you have some severe ductwork problems. anyway you slice it, you need to call another company and get a second opinion.

  4. #4
    Thanks for all the responses so far.

    I don't believe they took any of those other readings because they are blank on the invoice.

    No, they didn't mention anything about the outside unit, except that if I don't get the evap coils replaced then the condenser would blow and I would be out 10K. As it is, I don't necessarily think that the system is undersized ... 3 tons should be good enough for something in the 1900-2000 sqft range, no? I would most likely attribute the heat in the bedroom to ductwork problems, but I am no professional.

    If the evap coils were bad, wouldnt he know that before going outside? He didn't make this suggestion until after I told him the bedroom was hot.

    How do you fix a liquid line restriction?

  5. #5
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,517
    Before we get all load calc crazy here making sure it is done by NATE certified techs. Has the unit ever worked? Is this a new problem you've been having? If so, you're probably fine with the sizing. You could need a new coil, but maybe the metering device is clogged or has crap in it. What type of refrigerant is it? Maybe it is getting clogged with oil. Has the unit been serviced before? Maybe the last guy overcharged it? At any rate, I would call somebody else out to look at it. As far as putting a 4 ton coil on it if it does come to that. You need to match it to the condenser and see what is recommended to match to it. Older 3 ton Carrier units actually use a 2 1/2 coil now. Not sure of what brand you have, but I think you get the idea.

  6. #6
    Oh yea, the unit has been working ever since it was put in. I moved in a few months ago (this was a friend's house before I bought it) and I noticed that my bedroom and the study were hotter than the rest of the house. The guys today said that the level of freon was 'fine', but you never know.

    At any rate, is the condenser in danger right now? The guy obviously sounded like it was urgent and needed to be done today, but it has been running like this for months, so I don't see how it could be that fatal.

  7. #7
    Join Date
    Jun 2008
    Location
    phoenix az
    Posts
    24
    if the guys pressures were accurate at 80 and 315 pounds, i can tell you right now there is NO restriction in that system. i could sit here and get all technical on you but im keeping this as simple as possible. as far as the danger of the outdoor unit blowing up, i very highly doub it. but there is a simple thing you can do that requires no tools to see if the outdoor unit is in danger of failure. that is to simply go out to the condensing unit with the unit running and feel the bigger pipe of the 2. if it feels extremely cold, like almost freezing cold, then yes, there is some potential danger of slugging the compressor to death with liquid freon. there are so many variables here that i can only speculate on what should be your correct move. i can tell you that with those kind of pressures, but not knowing sh or sc readings, that most likely the unit is either under a huge load, or is overcharged. if the bigger pipe is almost freezing it most likely is over charged, if the bigger pipe is not very cold, it most likely is under a huge load, which is mostly due to undersizing, abnormally high humidity and a return in a attic (if in attic?) that has fallin from unit.

  8. #8
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    Quote Originally Posted by hvacguru69 View Post
    if the guys pressures were accurate at 80 and 315 pounds, i can tell you right now there is NO restriction in that system. i could sit here and get all technical on you but im keeping this as simple as possible. as far as the danger of the outdoor unit blowing up, i very highly doub it. but there is a simple thing you can do that requires no tools to see if the outdoor unit is in danger of failure. that is to simply go out to the condensing unit with the unit running and feel the bigger pipe of the 2. if it feels extremely cold, like almost freezing cold, then yes, there is some potential danger of slugging the compressor to death with liquid freon. there are so many variables here that i can only speculate on what should be your correct move. i can tell you that with those kind of pressures, but not knowing sh or sc readings, that most likely the unit is either under a huge load, or is overcharged. if the bigger pipe is almost freezing it most likely is over charged, if the bigger pipe is not very cold, it most likely is under a huge load, which is mostly due to undersizing, abnormally high humidity and a return in a attic (if in attic?) that has fallin from unit.

    i tend to agree to some extent
    did this guy clean the condenser coil before he made his disicision. With a head pressure that high i would think cleaning the outside coil is in order to try to lower the pressure. High head in most cases is over charge or dirty outside coil.

    you low side pressure of 80 may be caused by high load or improper orfice and a over charge also. There are a few other things that will give high low side pressure

    80/318 isnt saying restriction IMO it is saying fix me

  9. #9
    Alright, so the pipe is not freezing at all. That would dispel the chance that it is going to burn up, no?

    We have two return air vents - one in the hall between the master and the kitchen, and one between the family room and the hall in the front of the house that leads to the guest bedrooms and study.

    I also might mention that I live in Houston, which is only the most humid climate on the face of the earth

    So, what would be the problem? Having knowing minimal information about HVAC stuff, I would guess that the house was simply built poorly (as far as ductwork goes) The master has only one vent for cool air to come through, and that is in the middle of the room. Seems there should be two, but what do I know.

    Also, the attic unit sits right over the family room, so the coolest room has the shortest run of ductwork, and vice versa. That would lead me to believe that something in the attic is wrong as well.

    The guy also said that after the unit is turned off, the condenser whistles for 3-5 seconds, and he said that is due to the restriction. Any input on that?

  10. #10
    I should also mention that the temperature reading was 69 degrees when he measured the 80/315. What would that mean?

  11. #11
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    Quote Originally Posted by shanebo2003 View Post
    I should also mention that the temperature reading was 69 degrees when he measured the 80/315. What would that mean?


    truth is
    means absaluty nothing. Pressures give you a point of refrence but sh and sc and a few othe readings need to be taken to mean anything of importance

    what you have given here isnt enough to make a real disision weather you have a serious problem or not

    dirty coil
    attic heat in return maybe
    leaks in supply duct maybe

    need more conclusive info

  12. #12
    Would it at least rule out having to spend a bunch on a new evap coil? I mean, I am not going to hurt anything by waiting for a second opinion, correct?

    I'm guessing not because it has been this way for monnnnnnths, but just checking!

  13. #13
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,517
    Quote Originally Posted by shanebo2003 View Post
    Would it at least rule out having to spend 3K on a new evap coil? I mean, I am not going to hurt anything by waiting for a second opinion, correct?

    I'm guessing not because it has been this way for monnnnnnths, but just checking!
    There isn't any pricing allowed. But I will say that unless that thing is made of gold. That is a very expensive coil for Texas. I would find a new company.

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