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I'm a handy guy and can do pretty much anything around the house that I put my mind to.

Assuming I can handle the part of the install that is outside (the concrete pad, the hole in the crawlspace wall, the electric), is it realistic for a handy homeowner to run flexible ductwork throughout a small (1000 sq. foot) house and hook the whole thing up?

What are the most likely mistakes a newbie would make in this process?

  • Depends largely on how much you know about ductwork design, return air handling, plenum building, etc. Are you hooking into an existing air handling system? – Comintern Jun 23 '15 at 23:43
  • One thing that would be useful for making the decision to do it myself or not...other than the potential for it not being as comfortable as I like if I do it wrong...what other "bad thing" could result from poor duct design? – Jeff Pritchard Jun 24 '15 at 2:20
  • Air quality for one. Also, unbalanced systems run much less efficiently. – Comintern Jun 24 '15 at 2:26
  • I'm in a similar position. I can do most home improvement tasks, and I just purchased a condo in Chicago with 3 PTAC's (all broken). So Jeff, what's the verdict? Is this a DIY task or did you leave it to the pro? – user44024 Sep 28 '15 at 17:58
  • I did it myself and it works very well. Still finishing up the ducting bit by bit to less-used rooms. If you're handy and have the intestinal fortitude to do all the work, it is definitely within range of a DIY. Some folks should definitely consider having the electric part done by a pro. As far as laying out the system and running flex duct and making a concrete base to place the unit on...all very doable by DIY. Just read up on it and watch a dozen or so youtube videos and you're good to go. – Jeff Pritchard Sep 29 '15 at 18:22
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If you're willing to blur the line between homeowner and HVAC tech, sure. If this is a split system, hooking up the linesets, purging the lines with compressed nitrogen, pumping it down, measuring the vacuum, adjusting the charge, and ensuring that the system is leak-free are all likely to be the most challenging parts. These tasks require specialized tools and knowledge. You can certainly get the tools and acquire the knowledge, but once you do that, you're basically as good as an HVAC guy, many of whom don't actually know how to do this stuff very well themselves.

Duct design is also its own huge field. If you just haphazardly run flex duct off a main trunk, you're getting a pretty typical professional residential job. But if you're doing it yourself, you have the opportunity to fabricate rigid sheet metal ducting, seal all the seams and gaps perfectly, design the entire system to be balanced, have enough returns, etc. This information would all be found in ASHRAE Manual D (D for Duct). Keep those ducts out of the attic! A crawlspace duct install is fine as long as there's a sealed vapor barrier over the dirt and the crawlspace walls are insulated.

  • Thanks iLikeDirt. Just one point...not a split system. As mentioned in the title it would be a package unit, with all of the tricky bits fully set up at the factory. I think all I would need to do is supply it with proper power, proper in and out of air, and a connection for the thermostat. – Jeff Pritchard Jun 24 '15 at 2:18
  • Oh, a PTAC? That's easy then. Just install the sleeve in the hole in your house and hook it up. Unless you get a heat pump model, it'll cost you a fortune to use for heating, though. – iLikeDirt Jun 24 '15 at 3:49
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    +1 for stating that you can do duct work at least as good as what is typically done by pros. Every pro-installed home forced air system I've examined closely has had major problems (duct that's too small, no fresh air, no means of balancing, fresh air ported through attic with exposed fiberglass insulation, air path that bypasses filter, etc). The real question should be "If I get a pro to install an HVAC system, how much of it should I expect to have to re-do myself?" – alx9r Jun 25 '15 at 20:13

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