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  1. #1
    Join Date
    Aug 2005
    Posts
    9
    How can I tell if my HVAC system's fan is starved for air? Can the situation be improved by adding returns or is it limited mainly by the size of the main trunk duct work? In other words, if there are already N returns in the house does adding one more add much to the air supply?

    thanks for your help!

  2. #2
    Join Date
    Jun 2003
    Location
    Florida
    Posts
    9,548
    You must be having problems. Have you had any professional look at it,check the duct sizes, etc.? if you haven't, make the phonecall.
    If everything was always done "by the book"....the book would never change.

  3. #3
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,795
    Originally posted by smokin68
    You must be having problems. Have you had any professional look at it,check the duct sizes, etc.? if you haven't, make the phonecall.
    How can you tell? LOL...
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  4. #4
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    5,034
    Originally posted by cobra888
    How can I tell if my HVAC system's fan is starved for air? Can the situation be improved by adding returns or is it limited mainly by the size of the main trunk duct work? In other words, if there are already N returns in the house does adding one more add much to the air supply?

    thanks for your help!
    Do a little reading.

    http://www.udarrell.com/proper_cfm_b...g_systems.html

    Use manual D for duct sizing.

  5. #5
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304

    Why not this?

    I surely would think measuring ESP (External Static Pressure) could give you an important clue. The tools to do this could be as cheap as a $20 red oil manometer bought on Ebay. My understanding is an air handler starved for air, would show an excessively high reading. In the past I had a diagnosis of this.

    The following link shows a final auction price which is quite affordable:
    http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA%3AIT&rd=1

    Similar currently listed items new-in-box are #7556878115 in Houston TX, #7557210318 in Minneapolis MN.

    Just a homeowner myself, but even I have bought those manometers and measured ESP. You could ask a pro for this test and use it as a litmus test whether he knows "advanced" stuff.

    Hope this helps -- P.Student

    [Edited by perpetual_student on 10-25-2005 at 10:38 AM]

  6. #6
    A really basic test would be to try and pull your filer out as it runs(this is assuming that you have a filter holder external to furnace) if it pulls hard into furnace it usually means lack of cold air return

    Another way is to see if the air flow increases with the filer out of the holder.

    Your trunk line maybe under sized in which case not much can be done.

    Removal of the trunk end cap would allow you to se if they are any there were any obstructios in the trunk and while cap is off you could run furnace to see if air flow improves. If it does than you might consider cutting a register or two down stream of the furnace.

  7. #7
    Originally posted by curry
    A really basic test would be to try and pull your filer out as it runs(this is assuming that you have a filter holder external to furnace) if it pulls hard into furnace it usually means lack of cold air return

    Another way is to see if the air flow increases with the filer out of the holder.
    Both of the above examples would happen if the filter were too restrictive. The ducting could be adequate, but you could have a very restrictive filter.

    Temperature rise and TEST will answer your question.

  8. #8
    Join Date
    Aug 2005
    Posts
    9
    thanks everyone for your help!

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