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  1. #27
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,324
    Condensing unit and compressor set system capacity. If evaporator is physically smaller than it should be for the compressor and condenser it is attached to, it will run lower suction pressures than normal. Might be okay during a good heat load but when the heat load falls off, the coil suction pressure drops to where the surface temp of the coil begins freezing the condensate.

    I would also seek less intensive heat methods of cooking the evening meal during the summer months. Running an oven adds lots of heat to the house, and, depending on what's for supper, cooking can add a lot of moisture to the air as well, which the a/c system will spend some time removing, possibly far into the night.

    Airflow should also be looked at, as well as the actual performance of the refrigeration system (superheat, subcooling, etc.). It's not enough to say "pressures look good" and hold a hand up to a vent near the furnace and say "air flow is good". These parameters should be measured.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  2. #28
    Join Date
    Jun 2009
    Posts
    20
    Thanks classical. I'm thinking of getting a "second opinion" from another company. It will be worth the expense to make sure everything is correct.

    Since there is a TXV on the coils, should I suggest a compressor delay switch? I couldn't tell you why it might be needed, but I do remember it was suggested.

    Thanks again!

    PeteTx

  3. #29
    Join Date
    Jun 2009
    Posts
    20
    Thanks Shophound,

    I am going to install a new vent hood that should move more air out of the kitchen. My wife usually keeps the cooking to a minimum in the summer months. Unfortunately we were having company come over.

    If my tech doesn't do the things all of you have suggested, I will get someone else to look at it and present him with the bill! Probably won't do any good, but I'll have statisfaction. He really is a great guy. He just doesn't do mobile homes much.

    PeteTx

  4. #30
    Join Date
    May 2002
    Location
    Houston Texas
    Posts
    6,321
    Any compressor with a TXV should have a time delay and a recip should have a start assit kit. Some Scrolls should have an assist and all Scrolls should have a time delay TXV or not.

    Shophound is absolutely correct.

  5. #31
    Join Date
    Jan 2007
    Location
    Vancouver Island, B.C.
    Posts
    2,469
    The 13 SEER only law was brought in by the USA guys.....us dumb Canucks only follow what the USA decides......
    As for mixing and matching 10/13/15/17 SEER equipment.....remember 2/3 of 4/5 of 5/8 of f--- all is still f--- all.....
    The piston orifice is rated at 'X' tons at 'Y' PD across it and when the O/T goes down overnight the PD drops and the SST drops below 26 degF thus you go ice which slows the air flow which decreased coil temp which ices the coil more which slows the air flow which...........
    For the sake of $80-100 more in a coil you waste electricity (Mass flow X CR/42.42=HP required) on a smaller coil, risk oil return and shorten the compressor life......
    Short Version put matched equipment in with a TEV

    As my old partner used to say You don't beat refrigeration, it'll beat you though if you cut corners....every frickin' time
    "The quality you deserve is not expensive---it's priceless"

  6. #32
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,910
    A time delay won't prevent a coil from freezing up.

    It will protect the compressor from short cycling though.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  7. #33
    Join Date
    Jun 2009
    Posts
    20
    Thanks for all of the help and encouragement. My technician called to say he contacted Mortex to verify what the regional "experts" told him about mobile home units. He discovered the "experts" are full of something pretty foul. The coil they gave him is actually matched/certified to a 13AJA36 (3 ton 13 SEER Ruud). He is going by tomorrow to demand the correct coil and pack the foul stuff in some more. I hope he wears boots.

    Also, during the call after the first freeze-up he did measure the CFM. I wasn't home so I didn't see it. The wife thought he was putting some kind of ice chest over the floor vent.

    The specs indicate the compressor is self timed to prevent a startup for at least 4 minutes after it stops. Is that enough?

    After reading all of this stuff and getting lost at Mr. Udelhoven's web site, my head really hurts. Making industrial web applications is a lot easier. Cooler too. When it gets hot the servers shut down. I feel for you guys always having to sit in the sun, crawl through hot attics and stinking crawl spaces.

    PeteTx

  8. #34
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,324
    Quote Originally Posted by PeteTx View Post
    I feel for you guys always having to sit in the sun, crawl through hot attics and stinking crawl spaces.

    PeteTx
    We appreciate that. I was up on the roof of our woodshop building this afternoon changing out a condenser fan motor and blade that had died on a Trane Voyager package unit. We made the job go quick, but did it neat (no run cap bandit on my watch!) . On and off the roof in less than an hour. Hotter than blue blazes with a turbo booster up there. As a younger man I did that kind of thing day after day during southern California heat waves. HVAC service is not an easy life.

    I hope your guy can get you squared away. Sounds like he's doing due dilgence to that end.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  9. #35
    Join Date
    May 2002
    Location
    Houston Texas
    Posts
    6,321
    Glad to hear your tech is following up and will fix your problem, sounds like he has a flow hood.

  10. #36
    Join Date
    Jun 2009
    Posts
    20
    Oh well...

    The guy never came out and now he doesn't answer my calls. I filed a BBB complaint so hopefully the next guy won't get burned.

    I know I'm going to have to call another company and pay for fixing this mess.

    Would y'all be willing to answer a few more questions and offer advice? Thanks in advance!

    What does all of this do to my warranty?

    Can I call any authorized Ruud dealer for service? I know they won't fix the coil issue. I'm wondering about future compressor problems.

    Should I contact the Ruud rep for this area for a referral to another company?

    I can't believe this guy is doing this. Over the years I've called him several times thinking I needed a new system and he found minor problems. He could have charged me for a new system years ago. I hope he didn't "stroke out" in the heat and I'm bad-mouthing him when he's down.

    PeteTx

  11. #37
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,627
    with this heat wave were having in Texas he is probably very busy give him a chance to make it right

  12. #38
    Join Date
    Jun 2009
    Posts
    20
    Thanks catmanacman.

    I would have no problem if there were scheduling issues, but he's not taking or returning my calls for the last week. And I did have a hard time getting him to realize the coils were incorrect. In his favor, the place he got them from still insist they are correct. Mortex says different.

    As I said earlier, he's been great for the last 3 years. I have told everyone I know in the area to call him if they need work because he has always been so honest and friendly. It's not like him to not call for over a week. I just hope he's OK.

    PeteTx

  13. #39
    Join Date
    Feb 2006
    Location
    Somewhere in the midwest
    Posts
    405
    I know this subject has been beat on quite a bit but here is my 10 cents worth.
    Mobile Homes have limited duct systems, so you are at a disadvantage from the gitgo.That combined with the fact the Mortex coil is a four pass coil and is a more restrictive coil, if your ducts are not in a row,(pardon the pun) and your mismatch is a factor, at night you have lower ambient conditions which can contribute freeze ups. Is this a gas furnace or an electric furnace? If electric, you could put a higher profile 2 or three pass coil, which is less restrictive , and creates less static preesure on top of it. I am sorry I did not read all the threads, but what are your model numbers? I see this all the time, and have various fixes for it. How about adding a cross over on the duct if it is a double wide..................
    Sound installation practices is the key to success. Equipment is only as good as the person installing it.

    If I can't fix it, it ain't broke.

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