Results 1 to 4 of 4

Thread: Ducting

Hybrid View

  1. #1
    Join Date
    Apr 2005
    Posts
    4
    I've been getting a few quotes on a new forced air furnace and AC. I have been reading these forums and trying to educate myself on how to pick an installer, since that seems to be the key. The only thing is I wish is that the installers came out to give the estimates and not the salesmen. Seems like they all have their own selling points and none has even included a Manual J. I do have a specific question though.

    I have been told my return is to small for the AC and would have to be enlarged, which made sense. However, the last guy just came in and said my return trunks did not provide the necessary airflow either. He recommended adding 2 more returns to increase the returns by 600-700 CFM as well as increase the size of the return.

    My existing system is 16 years old and has an 8x20 return with 2 trunks (8x10 and 8x14)coming in. The house is 2400 sq ft and has 2 6x30" returns and 5 6x15" returns in the rooms. The supply trunks are 8x8 and 8x18 at the plenum and feed a total of 13 18" floor vents and 2 12" floor vents.

    The existing system has been fine over the years.

    Does this make sense, is it important to increase the ductwork in my system or is there sufficient airflow as is and this is a non issue. Thanks for any help.

    Marty

    P.S.

  2. #2
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    We can't really tell from here,but the heating and cooling sizes and model numbers would help to give an opinion.

  3. #3
    Join Date
    Apr 2005
    Posts
    4
    Knew I would forget something.

    Current System 75000 BTU 90% Heil, no A/C

    Proposed system 80,000 BTU 2 Stage 90% Trane (maybe variable speed), 3 ton A/C

    I guess my question is also how many CFM can my existing ductwork handle. Or if I just have the return fixed and leave the trunks alone.

    Thanks

  4. #4
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    You need to find a Pro that will do the Calculations needed to determine the size of the system and the duct system.They are Manual J and D ,from ACCA.


    Ask if they can/will,and keep calling until you find someone that can and will.


    Without all the details of your duct system,I'd say it might be large enough for two tons of A/C ,outside chance 2.5,but not 3 tons.

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