Air Conditioning

jwrocdJune 8, 2011

In January, I had A/C system replaced in my 2,000 S.F. south Florida home. Went from 3.5 ton/12 SEER to 4 ton/16 SEER, Trane 4TTR5049E & 4TEE3C09A.When a Bdrm. door is almost closed & system comes on, door will shut quickly. With the variable speed AHU, should I be able to tell (or hear) a difference in fan speed at any time (which I can't) ? And, at end of May, should I be realizing more than a 8% energy savings ? Thank you in advance for your help !

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To get a measure of energy efficiency, determine your electricity use for a period and then find out the "cooling degree days" for that period. Divide KWH by degree days and compare to a time when you had the old system. The calculation will be in error if other electrical use changed significantly.

    Bookmark   June 8, 2011 at 2:06PM
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Yes, I did compare May 2010 to May 2011 & came up w/ an 8% energy savings. After replacing a 14 year old system, I had hoped for a larger savings. Is this 8% about right? And, should I be able to hear or feel a difference in the AHU's varible speeds (which I cannot) ? Or, is it possible that the AHU is operating only at 1 speed ?

    Bookmark   June 9, 2011 at 1:16AM
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May 2010 may have been a lot cooler. Bill might list average temp but that is a less than perfect measure. My gas bill was $200 for winter 2010 and $100 for winter 2011 - no changes - just a warmer winter.

Yes you should notice a difference in speed unless you never reach high stage/speed.

    Bookmark   June 9, 2011 at 2:55PM
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Does anyone even know what cooling degree days are?

    Bookmark   June 9, 2011 at 7:50PM
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I do now. Thank you very much for your help !

    Bookmark   June 12, 2011 at 8:46PM
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Your 4 ton unit is likely oversized, and is running contantly in first stage. With a single stage stat, the on time is less than the board's set (timer) upstage time. The same could be said for a 2 stage stat.


    Bookmark   June 13, 2011 at 10:30AM
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eh, 4 ton is on the verge of oversized for a 2000 sq foot home in Florida, with 2 stories this is likely perfectly fine. How long does your unit run while it's cooling?

    Bookmark   June 14, 2011 at 7:10PM
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