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  1. #1
    Join Date
    Jun 2019
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    2
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    Confused Consensus on whether or not twist elbows are acceptable

    Hello!

    I have just received two bids for replacing my 4T rooftop over under packaged heat pump. There is a significant gap in the two bids and the difference seems to mostly be attributable to the fact that contractor A wants to redo/replace significant amounts of stuff in my attic to accommodate a new side by side unit while contractor B seems to be fine using a 'twist elbow'/'twist adapter' or whatever the proper term is to more or less drop-in replace the new system.

    I have googled and found opinions ranging from "Twist elbows are the worst and anyone who believes in them should be burned for heresy " to "They are fine if done right". I read some other posts on this forum but couldn't find anything that seemed conclusive.

    I am hoping for some more definitive opinions since the difference is thousands of dollars.

    Thank you all!

    -dn

  2. #2
    Join Date
    Mar 2018
    Location
    Chico, Ca #StateofJefferson
    Posts
    687
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    Like most things in life it can work fine if done right, and Ive only seen it done right a few times and done wrong a lot more. Is your ductwork in the attic underneath or does it go into the side of the building? If you have uneven room temps or noisy returns/registers, that is a ducting issue which may become worse with either company. A manual D should be performed after sizing for the buildings heat load with manual J. This will show the heat gain and loss of each room and how much air needs to be delivered. Id ask the guy for some photos of other units hes done with the twist elbows to see what his install skills look like

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    39,869
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    Get an American Standard/Trane over under heat pump and don't worry about the twist


  4. #4
    Join Date
    Feb 2014
    Location
    Phoenix Arizona
    Posts
    944
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    Were in the east valley near Phoenix, so we do a lot of residential rooftop units(RTU). As youve already read if done right there is nothing wrong with a twist elbow per se, but it is a rare thing that we find a house with adequate ducting for it. Most RTU homes around here have under sized returns and poorly designed supplys.
    Im going to guess that you need the new jack and drop cut in.(the more expensive option.)

    Ask for a copy of the Manuel J and D. If they cant give you one, move on until you find a company that can. Its a simple way to weed out 80% of the hacks


    Sent from my iPhone using Tapatalk

  5. #5
    Join Date
    Jun 2019
    Posts
    2
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    Thread Starter
    Quote Originally Posted by Makeitcold View Post
    Like most things in life it can work fine if done right, and Ive only seen it done right a few times and done wrong a lot more. Is your ductwork in the attic underneath or does it go into the side of the building? If you have uneven room temps or noisy returns/registers, that is a ducting issue which may become worse with either company. A manual D should be performed after sizing for the buildings heat load with manual J. This will show the heat gain and loss of each room and how much air needs to be delivered. Id ask the guy for some photos of other units hes done with the twist elbows to see what his install skills look like
    The ductwork is in the attic underneath. Obviously not an expert but for the most part i never had problems with air distribution. The only issue is the master bedroom, because it is farthest away from everything (split floor plan) and is serviced by a big ol piece of flex duct that has to go over a vaulted ceiling in the living room. Still, the airflow in there is actually pretty good all things considered (i've seen vents on similar runs before that were worthless). I had planned to address this by adding a return in the master.

  6. #6
    Join Date
    Mar 2018
    Location
    Chico, Ca #StateofJefferson
    Posts
    687
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    Then forget about the twist locks and have them make it a down shot. Just about every RTU is adaptable to change airflow from horizontal to vertical. Basically they remove the elbow coming out of the roof and put the unit on a stand over the ducts, easy peasy

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