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  1. #1
    Join Date
    Jan 2006
    Posts
    140

    Confused Ext. Static Pressure of Amer. Stand. Variable Speed

    I'm stumped, trying to design a zone system with a variable speed blower utilizing manual D but lookin at the vague info. they give in the booklet isn't helping at all. Its the american standard 16 seer, 4TEE3F65 for 5 tons but what they give for 2000 cfm on the airflow performance chart doesn't make any sense. I feel like I have to work this one out backwards and guess the ext. static aviailability. Any one have a solution?
    The only decision in life is to decide what to do with the time given to you

  2. #2
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    What doesn't make sense about it?

    If you look at the performance chart in the Service Facts, it makes ~2000 CFM from .1" wc through .5" wc with the dip switches set for a 5 ton outdoor unit and the cfm/ton set to 400.

    After .5" wc the cfm drops off because the blower is pushing close to its rpm limits.
    You can tell the drop off above .5" wc is due to the blower reaching its rpm limit by looking at the 450 cfm/ton data. Note that the blower performance is about the same at higher static pressures at 400 and 450 cfm/ton.

    Depending on the filter I was using, I'd pick either .3 or .4" wc and design from there, .3 if you have a very low resistance filter system, .4 if using a more restrictive filter. That should leave you with enough available static, after subtracting for the heat package and grills/diffusers, to design the duct system, and leave a little cushion for the filter getting dirty, etc.
    You could just pick .5" wc, but you would most likely end up having to upsize all the ducts to avoid velocity issues anyway, so is kinda pointless.
    Last edited by mark beiser; 09-26-2008 at 06:19 PM.
    If more government is the answer, then it's a really stupid question.

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