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  1. #1

    Carrier 48JZ dual-fuel problem with combustion motor

    First off, I am a woman with very little knowledge in search of some answers to how HVAC systems should work. I've been reading some of the posts and some of the abreviations I don't get so if someone can "spell it out" for me that would be GREATLY appreciated.

    I had a Carrier 48JZ unit installed on Jan 3, 2003. I've had it serviced faithfully 2 times a year.

    I am now told that the combustion motor is shot (I saw the blades were rusted right off today) and the heat exchanger needs to be replaced due to rust as well. The GOOD thing is the heat exchanger is still covered under the 10 year warranty (labor is extra - a lot), but the combustion chamber is not.

    I asked my tech was there ANYTHING that I could have done to prevent this from happening - NO, he said. He advised me that the combustion motors are a common problem with my model and in fact, the part is on back-order.
    He further commented the high humidity of our NC weather contributes to the rust.

    My question is... if this normal "wear & tear" or is this just an inferior product and ill-suited to the highly humid area where I live?

    I mean if rust is a potential/probable issue WHY would someone recommend a unit that is going to rust and need a repair in 5-6 yrs that about 1/2 the cost of the original unit??

    Shouldn't a "professional" recommend a unit that will hold up to the weather conditions? Or should I just expect/plan on replacing expensive parts every 5-6 yrs?

    I need someone I can trust and honest advice.

    Is it worth me calling Carrier to complain? (nicely of course) Because if the tech sees this problem "all the time" why has Carrier not addressed this?

    Again, I do NOT know what the life of a combustion motor should be. But my gosh, it seems that it should last at least 10 yrs.

    My last hvac unit lasted 12 yrs. I forget what kind it was, but it was faithful until the end...

    Thanks!

  2. #2
    Join Date
    Jun 2000
    Location
    B.C. Canada
    Posts
    147
    Most corrosion problems are caused by short cycling problems with the unit, this is caused by being oversized and the heat-exchanger never gets hot enough to dry out completely before the burner cycles off. This moisture rusts the crap out of everything, high humidity locations can cause issues but it would have to be off the charts humid. Like equipment in swimming pool areas are usually rusted out pretty good. Most HVAC systems should last 20-25 years unless the installation is unique.

  3. #3
    Join Date
    Aug 2009
    Location
    Beatrice, NE
    Posts
    1,747
    Juleous is right, another thought is indoor polution, ie hairspray, chemicals, paint/refinishing, etc. Anyting like that going on in the house.

  4. #4
    Juleous said... "Most corrosion problems are caused by short cycling problems with the unit, this is caused by being oversized and the heat-exchanger never gets hot enough to dry out completely before the burner cycles off. "

    Is this short cycling something that should have been caught by the regular maintenance? Can this be adjusted?

    Yes, I do use hairspray. How much of that can be detrimental?

    Thanks for the quick replies.

  5. #5
    How do I know if my unit is "oversized" for my 1600 sq ft home? It is a Carrier model# 48JZ-030060301.

  6. #6
    Now that I think about it 2 years ago we had a major remodel done to the inside of our house. New carpet, laminate flooring and painting too. Was there something we needed to do to prevent "contaminating" the HVAC system? Is it better to do those things during certain times of the year? We did it in Sept/Oct so the weather here in NC is mild at that time and not much heat/ac is needed. Although I must admit that I don't tend to open the windows because we live in a dirt road and I don't want the dust from the traffic getting in.

  7. #7
    Join Date
    Aug 2009
    Location
    Beatrice, NE
    Posts
    1,747
    The only way to know if the unit is oversized is to have a proper load calcultion done on the house. This us usually done when equipment is replaced, changes in the structure, ie windows, insulation, additions, appliances, can cause the size to go up or down from what the original equipment needed to be. Often times the origional equipment was "rule of thumb" sized instead of calculated. Also as equipment becomes more efficeint and rating procedures change going by the existing equipment size becomes more of a problem. Example a 100k furnace in 1970 had an output of 80k but an AFUE of maybe 65%{they weren't rated in AFUE then}, today an 80k, 95% AFUE furnace will give you more heat than the 1970's unit did. I hope that makes sense for you.

  8. #8
    Thanks for the input. All this sounds kind of greek to me. I really don't think a load calculation was done on my home. I think they just guessed according to my 1600 sq ft. I am very disappointed right now.

    I think I just need to get someone out here who can give me the "low down" on my situation.

  9. #9
    Join Date
    Aug 2009
    Location
    Long Beach CA
    Posts
    182
    Yea a glossary would be nice for the uninitiated. You can Google any term you don't understand. For instance:
    Annual Fuel Utilization Efficiency (AFUE)
    So what these pros are saying is that, if you got the same size equipment you had that was not very efficient, the new stuff is now oversized and does not run long enough. This is a big problem in this industry.

    I would definitely contact Carrier, customer satisfaction is important to them. I would be mad if my relatively new unit needed these repairs. It's not like you went with one of the no name brands. (although I don't know where you particular unit falls in Carrier's Good, Better, Best lineup.)

    And start running the bath fan when using spray products! I recommend replacing the bath fan switch with a countdown timer so it stays on a while after you finish in there.

  10. #10
    Thanks egads. I will call Carrier tomorrow!

  11. #11
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,399
    Not unusual for a Carrier gas pack unfortunately. On these units, the heat exchanger is in the cold air supply which means all summer they are wet from outside humidity. So they rust out very quickly. It is a big no-no to install a split system this way but yet most mfrs. do it on their packaged units.

    I don't think it has anything to do with sizing or hair spray in this case.

  12. #12
    Join Date
    Dec 2006
    Location
    Middle Tennessee
    Posts
    11,347

    *

    this is why every contractor should offer a 10 year parts and labor warranty

    then you would not be liable for these types of problems

    for the homeowner's reading this, inquire about warranties (before) you purchase a system



    .

  13. #13
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,512
    Quote Originally Posted by Airmechanical View Post
    this is why every contractor should offer a 10 year parts and labor warranty

    then you would not be liable for these types of problems

    for the homeowner's reading this, inquire about warranties (before) you purchase a system



    .
    i agree on the 10 year parts and labor warranty

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