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Install a Trunk Line for HVAC

There could be a couple of reason why you need to install a trunk line for HVAC. The trunk is sized incorrectly so you need to replace it, building a home, or you just want too. Whatever your reasoning I want to share how to install a trunk line yourself to save you money. Because it could save you thousands!

If you’re wondering if you need to install a new trunk line or redo your HVAC, read this article to help you decide that.

Are you needing to install a trunk line for HVAC? Maybe your not even sure what a trunk line is? Learn how to DIY and install a trunk line yourself.

THE SIZE

This is the most important step! The trunk line needs to be sized correctly for everything to work properly. And because it factors in everything (vents, furnace type, & AC type) you should have a professional do this part.

I know I said you could save money doing it yourself and you can. What you need to do is hire a local HVAC company to size your trunk line and build it. Because this will take them very little time to fabricate the line (it comes in pieces to put together). Plus it will be sized correctly. The way you save money is by installing it (putting it together).

So you will NOT be sizing the line but installing it.

Things to things about before:

  • The number of vents you will have in your home, their sizes, and where they are placed.
  • If you are replacing the furnace, AC, or both

With our home, we were replacing all the HVAC minus some return ducts. So we added a new furnace & AC, moved both units, and removed all the old air ducts. Here is what we were working with…

Something that is very important is a working furnace and AC unit. Should you replace the HVAC in your home? Or maybe just part of it?

Something that is very important is a working furnace and AC unit. Should you replace the HVAC in your home? Or maybe just part of it?

But before we could do anything we had to remove the old and this was a dirty job (dusty) so tape off parts of the house with plastic before starting.

Something that is very important is a working furnace and AC unit. Should you replace the HVAC in your home? Or maybe just part of it?

Something that is very important is a working furnace and AC unit. Should you replace the HVAC in your home? Or maybe just part of it?

SIDE NOTE: My uncle helped us install the furnace and AC. It was not hard but they both needed to be adjusted for the elevation & test levels to work properly. So if you do not know someone that is an HVAC tech, hire a PRO to install them! You could have them placed before hand and have the PRO hook everything up but call the company first to see if they will do that.

Disclosure: This post contains some affiliate links for your convenience, click here to read my full disclosure policy

INSTALL A TRUNK LINE FOR HVAC

NOTE ABOUT SUPPLIES: We purchased all our supplies from a local construction store (AC & Furnace store) so check your area to see if you can purchase from a specialty store.

SUPPLIES:

  • trunk line metal (from a company)
  • duct sealant
  • 1.25″ sheet metal screws (attaching trunk line to ceiling)
  • 3/4″ sheet metal screws (attach takeoffs to trunk line)
  • vent top takeoffs
  • vent pipe

TOOLS:

  • tin snips
  • crimper tool
  • cheap paint brush (to install sealant)
  • hammer
  • tape measure
  • sharper marker
  • drill
  • flat head screw driver

Find the list of tools we use.

Once you have all your supplies you can install the trunk line. The company that we used supplied all the metal pieces needed for the trunk line. They also gave us a paper that showed us where to place each trunk piece.

We had to purchase all the takeoffs, duct pipe, and duct sealant separately. I will be sharing another tutorial on just the ducts and I will show you the different types! But the most common sizes are 6″ and 7″, we are using both!

THINGS TO NOTE:

  • INSTALL TAKEOFFS FIRST: What you need to do is measure the distance need for each takeoff. Then using a template (I used a cardboard box the size of the takeoff opening) trace and cut out the opening. TIP: Use a drill bit to start the hole. Then install the takeoff with some extra pipe attached. The extra pipe will make it easier to install more pipe after (have it just pass the trunk line or wall).Are you needing to install a trunk line for HVAC? Maybe your not even sure what a trunk line is? Learn how to DIY and install a trunk line yourself. Are you needing to install a trunk line for HVAC? Maybe your not even sure what a trunk line is? Learn how to DIY and install a trunk line yourself.Are you needing to install a trunk line for HVAC? Maybe your not even sure what a trunk line is? Learn how to DIY and install a trunk line yourself.Are you needing to install a trunk line for HVAC? Maybe your not even sure what a trunk line is? Learn how to DIY and install a trunk line yourself.
  • Make sure the pieces are pushed completely together using the metal pieces. Use the crimpers if you have to cut the pipe. Are you needing to install a trunk line for HVAC? Maybe your not even sure what a trunk line is? Learn how to DIY and install a trunk line yourself.Are you needing to install a trunk line for HVAC? Maybe your not even sure what a trunk line is? Learn how to DIY and install a trunk line yourself.
  • Attach trunk line to wood using 1.25″ screws (use two for both sides) but DO NOT over tighten.
  • Attach the bottom of the trunk at an angle hammering into place.
  • Hammer the ends of the metal to attach the pieces together, later seal with sealant. Are you needing to install a trunk line for HVAC? Maybe your not even sure what a trunk line is? Learn how to DIY and install a trunk line yourself.

Sorry, I did not video the actual process but I would suggest this being a two-person job. I hope the video will help you know how to install a trunk line for HVAC yourself.

Are you needing to install a trunk line for HVAC? Maybe your not even sure what a trunk line is? Learn how to DIY and install a trunk line yourself.

2 Comments

  1. This is a big job, and better off hiring a Pro. I have changed my HVAC 2 times and would never attempt such a job. By the way in a one story home, you only need 2 return vents, and all vents are in the ceilings.

    Our attic is a small area to work, Pro’s took several days to complete job.

    1. It would be more difficult in a small attic space, I can see the benefit of hiring a Pro! Thanks for pointing out that the vents can be on the ceiling, I forgot to mention that… Thanks for sharing!

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