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Im trying to DIY fix my ducts

SouthDakotaRoof | Posted in Mechanicals on

I hired the wrong guy. He removed a 10+ year old furnace and unsealed/uninsulated ducts from vented attic (Yay!). Then it went downhill. He installed a oversized 96% 2 stage condensing unit in my heated basement, and now The outdoor ac unit bangs loudly as it turns off its short cycling runs. It’s return air (trunk, plenum?) Is too small to fit the size of filter the manual says it should have. Unsealed ductwork (im working on it).  Panned return. The pvc exhaust and intake run out my rim joist together directly touching each other and end touching eachother which is great for intaking the exhaust. (🤬) and the duct layout design is utterly incomprehensible to me, and the condensation line is mostly fishtank type tubing instead of pvc with a trap thats higher than it should be-(manual has a picture with a arrow saying ‘Dont install trap above this’) gahhh it’s just a bit worse than average for my local hvac companies work, in my experience. 

No, I wont waste my money calling in another company. Im going to take measurments and see if energy vanguard will do the magic number calculations for me on duct design etc. And then i will replace ductwork myself, learn as i go. 

Air Return, no more panning! The return is supposed to intake an equal amount or more of air as the supply side blows- why am i not finding register boots (for floor or wall) that are larger than 6x12x6? Menards & Lowes sell many vent covers of a large size but no boots to match them?  (Panning, ick) Im assuming I may have to form a boot on my own to match those sizes or else run multiple returns in rooms? I should just wait till i get info from E.V (or whichever willing company) but im a impatient tinkerer so im wanting to get in some practice on building duct now by replacing the panning. In addition to any suggestions on large boots I could use any suggestions on .coms or videos that are useful for a advice. I will not be touching the units themselves, no electrical or otherwise. Im just turning my hand to hard metal duct only. 

2nd question: i need to replace the unit too but id like to wait as long as i can, t(budget is tight)i be resizing ducts later on when i buy the much smaller and correct sized unit?

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  1. walta100 | | #1

    I say now that the ducts are inside the conditioned space the leaks are almost irrelevant. If you had a manual J and D calculations it would be nice if the planned amount of air got to each room but in the real world as long as you keep all the conditioned air in a well sealed and insulated house things tend to work just fine.

    As long as the returns are big enough to not restrict the air flow and you keep your doors open the returns make almost no difference. Do not sweat the panned returns so what if they leak 20% it just does not matter.

    I am guessing the larger vents you are seeing are intended for use as return grills and not supply registers so no boots needed.

    If you do downsize your unit remember having oversized ducts is a good thing and a luxury.


  2. SouthDakotaRoof | | #2

    Thank you for your input Walta, that has eased my concerns some! Do you have an idea on why the outdoor condensing ac unit thing slams off loudly? I intend on a service call to make sure the fan blade isnt loose or anything but my gut is telling me its connected to the new ducts/furnace inside as it became a issue with the new changes. The ac is still the same unit from before with the attic 80%, i cheaped out and did not update it as well.

    1. ohioandy | | #3

      Tia, that loud banging is probably the contactor, an electrical relay that turns the outdoor unit on and off. Typical noise, normal operation. New equipment is considerably quieter, good ones are almost silent. You said it yourself--you "cheaped out."

      Sheet metal work is accessible to the DIYer, but like all trades there's a learning curve and specialized tools. As frustrating as you find your local professionals (in this and previous posts) it would be to your advantage to figure out how to work with them a little more at the outset, in order to establish your expectations.

  3. walta100 | | #4

    Please post a YouTube video of the unit shutting making the sound down 3 different times.

    Assuming the unit is under warranty I would not touch it and call the installer.

    My wild guess is it is the fan blades or motor hitting something.


  4. Expert Member


    I've got to agree with Andy - there is s sense of deja vu about this problem, in that the way it has unfolded seems to be very similar the other ones you have posted about. I'm sure you are right that the work you are getting done isn't up to snuff, but something about the way you and contractors are interacting isn't working. You need to find out why before continuing to hire them.

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