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Thread: 13 SEER

  1. #1
    Join Date
    Sep 2005
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    Hey guys, been a while since I posted last, in fact this is only my second post. is what I use at home and although it will pull up this site, it will not allow me to post.

    Anyhow being a new tech and talking to folks about this new standard of the min SEER of 13, I've been told instead of figuring 4oo cfm per ton we need to figure 300 or 350 cfm per ton. Could someone please share some light on this subject for me and others that may be a litle confused?

    Now a little on the info that I got in the subject. With the higher SEER's there is gonna be a issue with mold thus being the reason for the change in cfm's per ton.

    I was tghinking that with that, you should be moving more air, so with the smaller cfm figure, that would require smaller duct causing the air to move faster.

    Am I even close?


  2. #2
    Join Date
    Mar 2004
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    Was told a seminars that tonnage is tonnage regardless of seer.Up north here ,we use 400 cfm/ton , I understand in the south,they use around 350 due to greater humidity removal demands.
    Some people swear by me and some at me

  3. #3
    Join Date
    May 2004
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    SEER has nothing to do with Capacity...
    400CFM/ton is the old school "rule of thumb"
    It still works today with standard multi-speed blowers.
    The 350CFM/ton has been used by some manufacturers on their variable speed systems (Carrier for one).
    Reducing your blower speed, increases your coil drop, allowing for more condensation and creating cooler temperatures. This is good, to a point, can be bad also...
    If a TXV is used, and subcooling is obtained (at high speed) then the 350cfm/ton will be helpful for dehumidification. You will also encounter a higher temperature rise during heating mode, which eliminates "cold draft" but could cause the system to reach high limit if it is not designed for 350cfm/ton.

    Basically, design the ducts for the requirements of the structure. Match the equipment size to the air flow and heating/cooling capacities required by the structure, and you'll have no problems with or need to be concerned about 400cfm vs. 350 cfm.

  4. #4
    Join Date
    Apr 2004
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    Forget everything you've been told and read the spec sheets and installation instructions.

  5. #5
    Join Date
    Nov 2004
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    You need to quit thinking and let an expert get into you wallet. your not ging to get sometnhg for noutin

  6. #6
    Join Date
    Nov 2000
    Eastern PA
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    Actually, this forum is all about getting something for nothing. We share information just because we want our industry to be overall better.

    400 cfm per ton is no longer a steadfast criteria. Some manufacturers need to stick to that amount of air in order to get the SEER rating they need for certain models, but that does not mean that lowering the amount of air in order to beef up dehumidification is not a good thing to do in the field. What good is efficiency without comfort?

    Anyway, there are some really good products on the market to deal with mold/mildew issues and there are definitely ways to set up our systems to make them more comfortable in wetter climates., and ye shall find;..
    So always seek the Truth, not just what you want to believe to be true…
    Ecclesiastes 10:2 NIV

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