Should HVAC duct installations use elbow fittings with a flat bottom or a flat top?
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Today, while looking at the blueprints, it was stated that for the parts of the HVAC ductwork that are buried underground, eccentric bottom flat elbows should be used. So, will eccentric bottom flat elbows also be used for the HVAC systems indoors? I’m not sure which standard specifies this in detail
Article 8.2.11 of the \"Code for Acceptance of Construction Quality of Building Water Supply, Drainage and Heating Engineering\" GB 50242-2002 stipulates that in a top-supply and bottom-return system, the diameter changes in the hot water pipes should be connected with the top aligned and eccentrically, while the diameter changes in the steam main pipes should be connected with the bottom aligned and eccentrically.