HVAC Duct Branches

A duct run is very rarely just a straight run through, often it is required to branch off the main run into other areas. To achieve this there is an HVAC branch which will allow this.

Branching off the main run has considerations though, you will need to ensure that the air movement equipment has enough duty to get the air through. This is done by calculating the resistances of the different elements of the HVAC system.

Once the calaculations have been carried out and you are confident that there is going to enough pressure in the system to get the air to where it needs to be, you can start adding branches to the main run.

What type of duct branches for ventilation are available?

  1. A simple flat spigot or IL as it is known in the trade, used to branch off flat recangular duct.
  2. A 90 degree equal Tee, attaches to the main run and has an outlet at 90 deg.
  3. A 45 degree Y piece. Install at the end of a section of spiral duct and allows two runs to branch off at 45 degs.
  4. Pressed Saddle – Simply fixes onto the main duct, pressed saddles come in a range of diameters, however there is no leading edge so be aware of turbulant air.
  5. Curved Boot – does a similar job to a pressed saddle but it has a leading edge to help with airflow.
  6. Flat Shoe – similar to a curved boot in the sense it has a leading edge, but it is used when branching off rectangular ducting to circular ducting.