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Thread: Duct work

  1. #1
    Join Date
    Aug 2005
    Posts
    26

    Confused

    Hi there,my name is Mike and I'm in commercial.We are about to put a furnice in a house that my friend bought.40 years old.Any tips on running the duct work?

  2. #2
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,467
    There are too many things ton list here.
    Here is a little info:

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

    http://ducts.lbl.gov/HVACRetrofitguide.html

    First, contact your electric power company, or some other entity in your area, and find out if they conduct manual J heat-gain audits and if they can recommend things to do to reduce your home's energy usage.

    "Only after you have reduced your home's energy heat-gain and heat-loss should you consider installing new equipment that has to be accurately manual J sized to the new lower heat-gain heat-loss conditions."

    Air Conditioning Efficiency Recommendations Summary List:

    * Wherever possible reduce the cooling load of the house. Overhangs above east and west windows are particularly effective in reducing cooling load.

    * Perform Manual J for all installations and select equipment by using Manual S.

    * Insure that the system installed never exceeds the capacity of the equipment suggested by Manual J or N for commercial buildings and Manual S for selecting equipment sizing.

    * Size duct systems based on Manual D. (If in doubt size upwards.)

    * Determine the grille location and characteristics using Manual T.

    * Confirm proper evacuation of the line set and indoor coil with a micron gauge.

    * Confirm proper charge using the manufacturers' suggested method.

    * Confirm proper airflow by test. The flow can be determined from the coil pressure drop when pressure/flow data is available from the equipment manufacturer or can be determined with a duct test rig or flow hood.

    * Increase the duct insulation to R-6 (at least on long runs in the attic).

    * Confirm that the duct leakage is less than 3% of coil airflow for a new system and less than 6% of coil airflow for an existing system.

    Do the ductwork installation right, or don't do it!
    - Darrell

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