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  1. #1
    Join Date
    Feb 2008
    Location
    NY
    Posts
    99

    new member - not sure where to post...

    Looking for some pro help...

    I own a Armstrong Air Ultra 80 oil furnace LUF80C112/125D20-1
    I want to replace my very old 8 SEER 3.5 ton outdoor compressor.
    My game plan...
    Replace the compressor with a 3 ton unit (I find that the current unit simply is not on that much in the summer (we do not put the temp. lower than 76 in hot weather) and we are usually very comfortable.
    I plan to buy a 3 ton Amana 18 SEER compressor (ASX18 0361A) and want to be sure I get the right coil to match.
    Looks like uncased coils CAUF3642D6A, CAUF4860C6A or CAUF4860D6A should match. (actual width might be an issue)
    The SEER ratings are based on a variable speed fan. My Armstrong Unit has a single speed direct drive fan with time delay.
    The folks at Armstrong gave me the part numbers for their 18 SEER unit and said I would need an Expansion Valve (part A4TXV0TTXV) to go with the coil.
    The Armstrong rep also said my fan is rated for 5 tons (seemed high to me)

    Can this set up work?
    What does the Expansion Value do and do I need it?


    Please note - I am not trying to do this on my own, just trying to get the best info.

    Thanks,

    Jrongo
    Last edited by jrongo; 02-26-2008 at 12:20 PM.

  2. #2
    Join Date
    Feb 2007
    Location
    18951
    Posts
    1,593
    It's best to ask your installer.

  3. #3
    Join Date
    Feb 2008
    Location
    NY
    Posts
    99
    I will. I am just trying to arm myself with the greatest amount of information before I start handing over hard earned dollars. This is clearly too complex to do on may own.

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,875
    Is that a 2 stage A/C.
    If so, it won't work right with a PSC blower.
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    How many times must one fix something before it is fixed?

  5. #5
    Join Date
    Feb 2008
    Location
    NY
    Posts
    99
    It is a two-stage system. Sould 2 stage systems be considered out of the question when dealing with a one speed direct drive blower?

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,875
    When a 2 stage is in its first stage. The blower needs to slow down the air flow.
    Your blower can't slow down for first stage.
    So a 2 stage would be a waste of money.

    1 possible exception, may be if you have your contractor also install a fan handler.
    It should be able to slow your blower down enough.

    Don't care for them myself, but thats JMO.
    But others seem to like them.
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  7. #7
    Join Date
    Mar 2002
    Location
    Concord, CA
    Posts
    2,635
    -Uncased coils have their purpose. However, why would you want an uncased coil? Is this one of those scenarios where the evaporator coil case is sort of built into the furnace assembly? If so, I doubt you'll fit any modern cooling coil into it. The new ones are much bigger.
    -I believe the coils you list are nominally rated for 3.5 tons and 5 tons. They'll both work great in a dry climate. However, they're both probably much bigger than your old coil and will dehumidify less. You can get stung on this issue real easy if you're not careful. You could end up with a cold, clammy, moldy home if you live in a humid area and choose the wrong coil. Find a good contractor to make this decision.
    -I believe you'll lose a point or so on the SEER rating with a standard blower.
    -The 20 in the model number indicates a 5 ton rating.
    -I don't get what Armstrong has to do with the TXV. If you're buying Amana air conditioning equipment then you'll need an Amana TXV. Buy the TXV. It's not that much and works much better.
    -Remove the pricing question please. It's not allowed.

  8. #8
    Join Date
    Feb 2008
    Location
    NY
    Posts
    99
    Yes the uncased A coil sits in the duct and not far above that is the basement ceiling. Size does become an issue. A 1 point loss in SEER does not seem like a terrible loss to me. Coming from 8 the saving should be nice to view come bill time. As for the A4TXV0TXV - that was given to be by Armstrong as he was telling me about Armstrong’s 18 SEER unit. He clearly could not comment on a unit they did not manufacture.

    A year and a 1/2 ago I company tried to sell me a 21 SEER Lennox system for about...well too much - that included: outdoor unit, new coil, new lines, new electrical feed and new concrete base but no mention of a blower that had variable speed. After that encounter I have found myself asking lots of questions.

    I think I covered the pricing issue, sorry
    Last edited by jrongo; 02-26-2008 at 12:27 PM.

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,875
    Considering you need over 1400CFM to keep the oil furnaces temp rise at 70*.
    I don't think the 3 ton coil is advisable.
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  10. #10
    Join Date
    Mar 2002
    Location
    Concord, CA
    Posts
    2,635
    The 3.5 ton coil listed has a pressure drop of .14 inches at 1400 CFM, which is pretty good. It can handle 2000 CFM at .27 inches. A rep said that the 3.5 ton use to be their 5 ton. I just don't see how it's going to fit. It's 23 inches wide and 28 inches tall.

    Don't get too excited about energy savings. About how much do you spend a year on air conditioning?

  11. #11
    Join Date
    Feb 2008
    Location
    NY
    Posts
    99
    Bill when AC is not running: 165 per month (about 30 KWH per day)
    Bill when AC is running: 350 a month (about 70 KWH per day)
    Rates are very high here.

  12. #12
    Join Date
    Mar 2002
    Location
    Concord, CA
    Posts
    2,635
    For how many months? In other words, what's your estimated annual expenditure on AC?

  13. #13
    Join Date
    Feb 2008
    Location
    NY
    Posts
    99
    AC runs for 3.5 months so 630 a year is a very reasonable estimate.

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