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Thread: System Rebuilds

  1. #1
    Join Date
    Jun 2007
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    Bucks County, PA
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    149

    System Rebuilds

    Hello, A Friends uncle calls me up and asks me an HVAC question, so I figured that I would run it past the experts. This person works at an apartment complex that has approximately 320 units. The HVAC systems are packaged type central units with gas heat that are originals, or re-builds from the late 1970’s early 1980’s.

    A new company has bought the complex, and they are doing upgrades, including hiring and professional HVAC Company to come out and do the service work, instead of the maintenance persons, which out of 6 only 2 were licensed.

    All of the A/C units have “Slide Out” chassis and are from 1.5-2.5 tons in capacity. These are all cap tube units, and some are original, some are “cobbled together” over the years to keep them working.

    The HVAC Company came out and did load calculations on each type of apartment offered, 5 in all, and realized that some of the systems are not properly sized.

    To make a long story short, they want to rebuild all the systems over the next 2-3 years, and install all new compressors, motors, reman coils and what not. They also want to install TXV’s on the units, at an additional cost over the standard rebuild with the Cap Tubes, this is my question:

    How much more Efficient will the TXV be over the cap tube systems?
    Will they see an increase in performance?
    Reliability?
    Lower electric bills?

    The reason that I ask this is I know that a TXV is more precise, however, these are not new units, and will be basically the old chassis with new or reman components. R-22 will be used in all units.

    Again, this will be a professional HVAC company doing this, not DIY, not the maintenance personal.

    Will the TXV be more trouble and cost than the older Cap Tubes?

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,080
    Not sure what the units are but rebuilding clunkers vs replacement doesn't make much sense. Are these a wall mount packaged unit like a Magic Pak?

  3. #3
    Join Date
    Jun 2007
    Location
    Bucks County, PA
    Posts
    149
    They are made by a company called PATCO INC from NJ. The units sit about a foot off the floor and are in a HVAC closet inside each apartment.

    The only thing on the outside is the Condenser and a grill for the exhaust, this is all flush with the wall on the outside.

    Aparently, the reason for the rebuild is the chassis is a old design, and any new units would require modifications to the exterior of building, or the inside closets.

    The heating systems work great, few complaints, and the heat is included in the rent price so they crank them up in the winter.

    The A/C on the other hand.... Well...... another story.

    But like I said before, they A/C chassis slide out for repalcement.

    I just took a look at the Magic PaK units online, yes, they look similar to them.

  4. #4
    Join Date
    Jan 2005
    Location
    Emerald Coast
    Posts
    934

    There's a career opportunity for ya...

    Rebuilds will appear cheaper but look at the bigger picture.

    Gas furnaces that are 20+ years old and cobbled together/rebuildt a/c.

    This situation is occuring all over the country. Cheaper to cobble/rebuild on the front end. Having a matched up higher seer brand name system 4 or 5 units at a time will lead to a better future.

    If it were easy to do everyone would do it.

    New systems seem to only happen in the med-higher end housing.

    Ask for quantity discounts.
    Do not attempt vast projects with
    half vast experience and ideas.
    ...

  5. #5
    Join Date
    Jun 2007
    Location
    Bucks County, PA
    Posts
    149
    From what I was told, if it were 20-30 units, then yea, new would be better. However, this is over 300, and the quotes came in at over 35% cheaper for the rebuilds.

    Again back to the TXV and the Cap Tube....

    Would the TXV be worth it on the old unit that originally came with Cap Tubes?

    Would you see a Efficient increase of overall performance?

    Could the TXV be troublesome?

  6. #6
    Join Date
    Jun 2007
    Location
    Bucks County, PA
    Posts
    149
    I also found out that they will actually install filters, as none of them had it on when they were put in.

    Oh yea, about those magic paks, if you look online and the specs, turns out that they are Cap Tube Systems, not TXV's.

    Back to the original question, will the TXV more efficient than the old cap tubes on the system rebuilds? Everthing in there except the chassis is either new, or rcertified reman (Coils) so will the TXV be worth the investment?

  7. #7
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
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    34,080
    TXVs do increase efficiency a bit and help with maintaining capacity in mild weather. They can also protect the compressor from slugging by keeping the supeheat up under low load or high head. Lately they have proved to be troublesome as is about everything to do with HVAC

  8. #8
    Join Date
    Jun 2007
    Location
    Bucks County, PA
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    I kind of figured it would be something like that.

    Now on a rebuilt system, would you take the risk of a TXV, or just stick to the Cap Tubes that have worked all this time?

    Is it something specific as of now that the TXV's have been giving more problems than they are worth, or has this been the overall trend?

    The systems that sit in the direct sunlight at 5 in the afternoon when they are charged correctly and clean will keep the 1200 sq foot 2 story town home apartment units at 70* insude they will blow 50-52* air from them The RH inside the Apartments is around 48-50%

    How much more could the TXV get it?

  9. #9
    Join Date
    Apr 2007
    Posts
    6,285
    It's a metering device that adjust the flow to always have a set superheat reading. Where as a cap tube super heat rating will vary from (hopefully no less) 5º-30º+ (In some cases). That means that as temps into the coil rises or falls it adjust it to always keep it a set point.


    So basically if both systems have the correct airflow and charge and they were vs. a TEV you would see little efficiency increase. However if the airflow changes or the charge is wrong. Your more likely to see better control over that bad circumstance with a TEV rather than a fixed bore type device like a cap tube.

  10. #10
    Join Date
    Jul 2007
    Location
    Phoenix, AZ
    Posts
    206
    Sounds like you are throwing away money on old equipment. You need to update this equipment to the R410A Freon equipment. We only have a couple years left with the R22 freon equipment. Just a thought.

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