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  1. #1
    Join Date
    Mar 2010
    Location
    North Louisiana
    Posts
    16
    Post Likes

    Please evaluate static pressure measurements on my system

    Furance is upflow 100 btu with variable speed blower. Dryer manometer readings
    Static pressure delta across electronic filter with metal pre filter (both cleaned) =.055"
    SP across furnance = .25" fan on set to heat
    SP across evaperator =. 08"
    Amp = 1

  2. #2
    Join Date
    Aug 2013
    Location
    Visalia California 93291
    Posts
    7,549
    Post Likes
    With your probe @ the intake of the furnace and the discharge of the furnace you are @ .25? Set the fan on high speed and the coil should be wet so if you can run the AC- that will give you a better idea of your duct system

  3. #3
    Join Date
    Apr 2012
    Location
    Millsboro, DE
    Posts
    181
    Post Likes
    The coil PD is way low for 100 MBH - I'm guessing you have 4 or 5 tons in Louisiana - a home there can't require that much heat. Wet coil should be 4 to 6 times that. Your external to the furnace PD of 0.39"+/- will jump. The filter PD sounds low too, check the manufacturer for a chart. Keep in mind you can use your measurements and filter, furnace and coil charts to estimate total airflow. Don't expect them to agree, but you'll certainly know more about how it's operating. As always, be within manufactutrer's CFM range on the cooling and the TR on the furnace nameplate.

    Use the heating formula to estimate heating airflow: Output in BTU's divided by the product of 1.085 and TR. There's a more complicated cooling formula too, let me know if you need that.

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