Results 1 to 10 of 10
  1. #1
    Join Date
    May 2008
    Posts
    31

    booster fan or mini-split

    I had a new furnace and a/c installed and at the same time additional ductwork to a new addition. The new ductwork is 2 6" supplies and 1 8" return. The airflow is almost non existent so I need to do something. I looked into Fantech fans which look like high quality but even so the consensus here seems to be they don't work. Fixing the duct work with bigger runs is NOT an option as space is extremely limited. The system was sized with this addition in mind (about 20% of total house) so there should be plenty of airflow available. Do these fans really not work or is it just another Goodman scenario where some people just don't like them?

    My other choice is a mini split which sounds like it will work well but obviously a lot more money in addition to the thousands I just spent on the new equipment. If I do go this route will the return and low flowing supplies effect the performance of the mini split? Do I need to close them off to keep the room sealed and separate?

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,334
    Properly applied, they can work.
    You got a new system sized for the addition?
    Or you got new equipment, and they reused your old ductwork, and just tapped the 2-6" supplies off of it.
    I wouldn't close off those supplies if they increased equipment size.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  3. #3
    Join Date
    May 2008
    Posts
    31
    Quote Originally Posted by beenthere View Post
    Or you got new equipment, and they reused your old ductwork, and just tapped the 2-6" supplies off of it.
    Yes this one. They used two previously unused 6" taps off of the original plenum. What I meant by sizing for the addition is the a/c went up 1/2 ton for the additional sq. feet.

    I wouldn't close off those supplies if they increased equipment size.
    Even if I go with a mini split?

  4. #4
    Join Date
    Jun 2008
    Location
    south central pa
    Posts
    133
    Quote Originally Posted by Bushum View Post
    Yes this one. They used two previously unused 6" taps off of the original plenum. What I meant by sizing for the addition is the a/c went up 1/2 ton for the additional sq. feet.



    Even if I go with a mini split?
    i wouldnt close off the supplies even with a mini split. ive seen this happen so much a customer adds an addition and the contractor gives the impression that it will work but just hooking new ductwork to an existing setup usually causes more problems. im sure if you had any rooms that had a slight temp difference from the main part of your house they are probably even warmer now. even if the duct work was "big enough" to handle the increased air flow it probably wasnt sized and ran properly from the beginning.

    do feel bad this is a very common problem especially with the new home construction. when a duct system is sized and ran properly you will get the same amount of airflow out of every register regardless how far away from the system it is. its just like your blood pressure its at your heart and the same at your little toe.

    either way you look at it your not traveling down a cheap route. you need to redo all of your duct... lol... or put in a mini split to properly condition your new area.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,334
    You increased the size of the new A/C. It needs X amount of air flow weather or not your addition is cooling right. If you shut thos 2 supplies down. You may not have enough air flow, and could shorten the life span for your new A/C.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  6. #6
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Larger system,same ducts,tapped off for new supplies instaed of bringing them off the new,likely larger plenum,bad idea,poor air flow to addition.


    Get a real Pro to evaluate the ducts.

  7. #7
    Join Date
    May 2008
    Posts
    31
    According to this site http://www.engineeringtoolbox.com/eq...ter-d_443.html my 2 six inch supplies should flow 600 cfm. I don't know how accurate that is but I'd say they are flowing less than 100 cfm each just by comparing to my computer fans. (I know this isn't a great comparison but just know the airflow is almost non-existent) The Fantech fans say they can boost at least 300 cfm each. If the system was sized correctly and these fans actually work I think this should be enough airflow. Assuming the contractor installed something that had a chance of working. Now I know I can't ask prices but would you guys even take on a job as small as installing duct fans or is this a strictly DIY fix?

  8. #8
    Join Date
    May 2008
    Posts
    31
    Quote Originally Posted by dash View Post
    Larger system,same ducts,tapped off for new supplies instaed of bringing them off the new,likely larger plenum,bad idea,poor air flow to addition.


    Get a real Pro to evaluate the ducts.
    The ducts work ok for the rest of the house. All rooms are within 1 degree except the new addition which has virtually no airflow. It's hard to explain but the furnace and new addition are right where two roof lines of the old house come together and structurally it is a nightmare. The very low crawl is also restrictive to the plenum because there are footers everywhere and there is no room to do it over without major work to much more than just the HVAC. My only realistic options are get the new flex duct to flow more or get a mini split. My house is only worth $130,000. I'm not going to throw 5-10% of it's worth into something that will get no return.

  9. #9
    Join Date
    May 2008
    Posts
    31
    Quote Originally Posted by beenthere View Post
    You increased the size of the new A/C. It needs X amount of air flow weather or not your addition is cooling right. If you shut thos 2 supplies down. You may not have enough air flow, and could shorten the life span for your new A/C.
    Ok that makes sense. So whatever I decide those will stay. Thanks!

  10. #10
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,334
    Your 2-6" don't flow 600 CFM, if they did, you wouldn't hear anything but the air coming out of them.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event