Ductwork – Part 1

1. Ductwork – Part 1

2. In this exercise you will be faced with a new installation of a new heat pump and making the transitions necessary to connect the return air to the filter, the filter to the heat pump and the heat pump to the ductwork. There are 3 transitions. Ductwork Top view Side view 18” tall “can” Return air Filter Heat Pump

3. Let’s take a closer look at this transition Return air Filter

4. The filter is 8” deep, 25” tall & 25” wide The return air is 18” tall & 25” wide The distance between them is 10” 8” 25” 10” 18”

5. Notice that both the return air and the filter box have 1” flanges that turn in. This is good because it will allow us to use S-slips to hold our transition to both of them. 8” 25” 10” 18”

6. An S-slip looks like this When joining ductwork together, the pieces go in like this

7. This is good because it will allow us to use S-slips to hold our transition to both of them. An S-slip looks like this When joining two flanges together, they go together like this When joining ductwork together, the pieces go in like this

8. Back to our transition. The transition is shaped like this. This is the transition you will be building so to demonstrate, we’re going to do an easier one. It will be a 14” x 10” to 14” x 8”. We’ll get back to this one later. 8” 25” 10” 18”

9. This tutorial will show you how to layout a 14/10 to 14/8 transition with a flat bottom and total length will be 12". The first thing you need to do is cut a piece of steel 12" wide and approx. 36" long. We need to consider the way we need to connect the transition to the other duct. We are going to use S-Slip & drive connections on this one. These connectors require 1" so we need to scribe a line along the top and bottom at 1" This will give us the required allowance.

10. We will make this transition in 2 pieces. The one piece will contain the bottom and 2 sides. We know the duct work is 14" wide so we will start by making 2 lines (A) 14" apart from each other keeping them somewhat centered on the steel. You'll find out that if you don't, you will not have enough steel to layout the sides.

11. Now that you have the bottom layout done, you need to determine the sides and you know that 1 side is 10" x 14"( 14" being the bottom and 10" being the sides)so make a mark 10" from line (A) to line (C). Do this on both sides as I did above. Now that you have the 14" x 10" done you need to do the same thing for the 8" side (On the top of the plan) Mark your line 8" from line (A) to line (B) on both sides Sides Bottom

12. Now you need to connect points (B) & (C) and you may start to see the fold out view of the bottom and the 2 sides...

13. Now that we have the 2 sides and bottom we need to consider how we will connect the top. There are several different methods. The 2 most common are the Pittsburgh and the snap lock. Most Pittsburgh machines require an additional 1- 1/8” allowance and the snap-lock former requires 1 5/16". We’re going to use the Pittsburgh. So we need to add a line ( D,E) parallel to lines(B,C) out by 1-1/8" .

14. Once this is done you can cut along the outer lines and notch in about 1" as shown. Now you should have something that looks like this once you’ve made your cuts.

15. The next thing you need to do is cross brake all three sides (This helps reduce noise in the ductwork) You should cross brake any duct larger than 8". Next you run the tabs labeled “lock” thru the Pittsburgh machine. If the connection for this transition is like the others where we are using S-slips, the tabs at the top and the bottom are braked up 90 degrees. The lines “A” are braked up 90 degrees.

16. You should end up with something that looks like this The top is going to be 14” wide plus 3/8” on each side for the tabs to slip into the Pittsburgh. To get the other dimension, measure from here to here and add 2” for the flanges. Top

17. It goes together like this

18. It goes together like this Then the tabs on the Pittsburghs are pounded over with a hammer making the whole thing nice and tight.

19. Back to your transition. The transition is shaped like this and is 25” wide. There are 1” flanges on each side so it can be connected to the return air and the filter using S-slips. Draw it out showing dimensions, final shape of each piece, folding lines, tabs, etc. Use the graph paper provided. Make it to scale. It will take two pieces of steel , each 36” X 48” 8” Bring your layout to our second week lab. 25” 10” 18”

20. Good luck