Click "Loads | System Duct Load Factors" to open this page. You must have a project open in order to open this page.

System: Specifies the system you want to edit on this page.

Scenario Number: Displays the current scenario number. If ducts in this system all have the same properties and run through only one kind of location, you only need to fill in data for duct scenario number 1. If the ducts have varying properties or run through multiple locations, you can fill in up to 5 different duct scenarios.

Scenario Name: Specifies the name you want to give the current scenario. If ducts in this system all have the same properties and run through only one kind of location, you only need to fill in data for duct scenario number 1, which by default is called "Main." If the ducts have varying properties or run through multiple locations, you can fill in up to 5 different duct scenarios and give each one its own name.

Duct Location: Specifies the kind of area that the ducts run through, such as Attic or Basement. If you select Attic, be sure to also specify the Attic Ceiling Type.

Attic Ceiling Type: When the Duct Location input is set to Attic, specifies the attic roof category. The categories each have their own approximate ambient temperature in the summer and winter.

Duct Leakage Rate: Specifies the leakage rate in CFM/sq.ft of the ductwork in the specified location. The rate you enter is multiplied by the duct surface area to give a leakage CFM.

Duct Insulation R-Value: Specifies the R-value of the insulation around the exterior of the ducts.

Supply Duct Surface Area, Return Duct Surface Area

Status: This gray box shows which option you selected on the Duct Surface Area Calculator page. Here are the four possibilities:

•"Using ASHRAE 152 (auto tracking with floor area)"

•"Using ASHRAE 152 (no auto tracking)"

•"Using custom calculated duct surface area"

•"Using user-defined duct surface area"

Duct Surface Area: This gray box shows the square footage of the supply or return ducts to use for the current duct load factor scenario. Click the Calculate button below this input to open the Duct Surface Area Calculator page.

Manual Override and Percent of Total Load: Lets you specify sensible loss, sensible gain and latent gain as a percentage of the total load instead of using the scenario selections you made above on this page. To override the loss or gains, check the appropriate box, then enter a percentage in the box to the right. For example, if you checked the box on the Sensible Loss row, then entered 10% for the sensible loss, if your system had 9,000 Btuh of sensible loss due to everything other than ductwork, the program would add 1,000 Btuh of duct sensible loss, which would be 10% of your total loss of 10,000 Btuh.