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Learn McQuay DuctSizer in 6 Steps

Learn McQuay DuctSizer in 6 Steps


McQuay DuctSizer is one of the most important tools for MEP Engineer, it is used for determining the size of the air duct either rectangular or radial.It is a simple software and easy to learn.




Duct Design, DuctSizer, HVAC, McQuay, Tutorials,

First of all Download McQuay DuctSizer if you don't have it
We have two ways to calculate the duct size:

1- Equal friction method
2- Equal velocity method

Most of the designers prefer the first method and that I will explain below step by step.
Let's start with explaining the program lists!


1-      Exit: to exit from the DuctSizer.
2-      Print: to print the data and calculations.
3-      Clear: to clear the entered data.
4-      Units: to choose the units either (metric) or (ips US units).
5-      About: introduces some information about the program.
Duct Design, DuctSizer, HVAC, McQuay, Tutorials,



 I will use the drawing in the figure to explain on it.

Duct Design, DuctSizer, HVAC, McQuay, Tutorials,

Step 1:
  • Insert the climate conditions: (Temperature, Relative Humidity, and Pressure.)
  • And in our example it will be 75oF, 50%RH and 1atm.


Duct Design, DuctSizer, HVAC, McQuay, Tutorials,


Step 2:
  •  Insert the flow rate in CFM for the main branch (and don't forget to click on the check box) in our example the flow rate is 3200 CFM for the main branch.
  • we use the equal friction method so we have to find the head loss in in.WC/100ft , we will use the equal velocity method to find it.

Duct Design, DuctSizer, HVAC, McQuay, Tutorials,






Step 3: 

  • Assume velocity = 1200 ft/min ( you select the optimum velocity from AHRAE tables to reduce the noise).
  • "Acceptable duct noise levels can often be achieved by limiting air velocities in mains and branches" ASHRAE series.



Duct Design, DuctSizer, HVAC, McQuay, Tutorials,


Step 4:

  • The program will calculate the value of the head loss.
  • It equals to 0.088 in.WC/100ft  in our example
  • Write this value in a note because we will use it later.



Step 5:

  • The program calculated the crossection area of the duct, now enter the first dimension and the DuctSizer will automatically find the second one.
  • We choose 18'' for height and the DuctSizer choose 23'' for width.
  • but the even numbers is better for duct construction so we will take the width 24'' ( the closer even number above).
  •  In case of radial duct the equivalent diameter is found in one step = 22.2'' .

Duct Design, DuctSizer, HVAC, McQuay, Tutorials,



Step 6:

  • Now you have the value of the head loss so you can complete your designation by the equal friction method which equal 0.088 in.WC/100ft in our example.
  •  Enter the value of flow rate of the first branch (in our example = 1800 CFM)  and value of the head loss which = 0.088.
  • Now the program will calculate the crossection area.
  • You enter the first dimension and the DuctSizer will calculate the second one.
Duct Design, DuctSizer, HVAC, McQuay, Tutorials,

NOTE:
  • We should unify a dimension in the main branch and secondary branches.
  • i.e. we will take the height = 18'' in all mains and branches.