Technician says I need more return air... is he right?
Page 1 of 2 12 LastLast
Results 1 to 13 of 23
  1. #1
    Join Date
    Jan 2011
    Posts
    9

    Question Technician says I need more return air... is he right?

    Last summer I asked an HVAC technician to come out and check on my AC. My house was built in 2005, so the AC is around five years old, and runs pretty much constantly throughout the day on hot days (90+ degrees in northern Alabama). He peeked into the attic and said my return air ducts were too small and quoted me a price on replacing the return ducts and filter box with larger ones. Before I spend the money (because it is quite a lot), I'd like to know if I really do need larger ducts and a larger air filter box. Could some kind soul please offer their opinion?

    I have a 2000 sq ft house, single floor with a bonus room above the garage (the bonus room is about 220 sq ft of the 2000).

    I have a 3.5 ton unit, which is serviced by two return vents: a 20" x 30" filter box into a 16" flexible duct (~30 ft long) and a 12" x 12" filter into a 10" flexible duct (~5 ft long). Is this sufficient?

    Here are the unit models:
    outside: Goodman CPLE42-1C
    attic a/c: Goodman CHPF042B2C
    attic furnace: Goodman GMS80904BNA

    If you need any other information, I can try to get it!

  2. #2
    Join Date
    Apr 2007
    Location
    Philadelphia
    Posts
    2,192
    Quote Originally Posted by Nate79 View Post
    Last summer I asked an HVAC technician to come out and check on my AC. My house was built in 2005, so the AC is around five years old, and runs pretty much constantly throughout the day on hot days (90+ degrees in northern Alabama). He peeked into the attic and said my return air ducts were too small and quoted me a price on replacing the return ducts and filter box with larger ones. Before I spend the money (because it is quite a lot), I'd like to know if I really do need larger ducts and a larger air filter box. Could some kind soul please offer their opinion?

    I have a 2000 sq ft house, single floor with a bonus room above the garage (the bonus room is about 220 sq ft of the 2000).

    I have a 3.5 ton unit, which is serviced by two return vents: a 20" x 30" filter box into a 16" flexible duct (~30 ft long) and a 12" x 12" filter into a 10" flexible duct (~5 ft long). Is this sufficient?

    Here are the unit models:
    outside: Goodman CPLE42-1C
    attic a/c: Goodman CHPF042B2C
    attic furnace: Goodman GMS80904BNA

    If you need any other information, I can try to get it!
    how are the flex runs connected to the furnace?
    Do they run into a common box on the return side of the furnace? If so what size is that?

  3. #3
    Join Date
    Apr 2007
    Location
    Philadelphia
    Posts
    2,192
    Quote Originally Posted by d_griff View Post
    how are the flex runs connected to the furnace?
    Do they run into a common box on the return side of the furnace? If so what size is that?
    Your home must be old and not very tight?

  4. #4
    Join Date
    Aug 2004
    Location
    Wpg Mb Canada.
    Posts
    338
    Most technicians arent going around condemning duct work for no reason as it is usually a pain in the ass to replace. Undersized ductwork is a frequent problem where im from. And hard to diagnose.
    Im thinking if you had freeze up problems in the past this would correlate with undersized ductwork.
    Best bet is to trust your technician on this one. If he is planning on replacing the flex duct especially.
    gahh

  5. #5
    Join Date
    Jan 2011
    Posts
    9
    Quote Originally Posted by d_griff View Post
    how are the flex runs connected to the furnace?
    Do they run into a common box on the return side of the furnace? If so what size is that?
    Yes, they run into a common box. Well, actually they both connect to the furnace box; one from the top, the other from the side.

  6. #6
    Join Date
    Jan 2011
    Posts
    9
    Quote Originally Posted by skr0oface View Post
    Most technicians arent going around condemning duct work for no reason as it is usually a pain in the ass to replace. Undersized ductwork is a frequent problem where im from. And hard to diagnose.
    Im thinking if you had freeze up problems in the past this would correlate with undersized ductwork.
    Best bet is to trust your technician on this one. If he is planning on replacing the flex duct especially.
    Well, to be honest, the tech did not seem very thorough. He peeked into the attic for less than 15 sec (to his defense, it was really hot up there), saw the duct and we went and sat in the kitchen and he did some napkin calculations. I don't think he really knew the duct dimensions or that even I had a second air return connected (the 12" x 12") when he was doing his calculations. I mentioned the second return and he stated that it really didn't make a difference.

    I'd just like to have more confidence in his opinion before I go and spend the $1800 to change out a return duct.

  7. #7
    Join Date
    Dec 2003
    Posts
    2,347
    Without seeing the sytem its hard to say for sure, but it sounds like you have enough return duct to me. Are the ducts sealed up good? A little duct leakage in a attic adds a lot of load to the system. Leaks in the supply are the worst, youre losing the cold air and the hot air from the attic goes through the structure cracks to replace it. In the summer youre losing 60deg air and getting 135deg air in its place.

  8. #8
    Join Date
    Aug 2004
    Location
    Des Moines, IA
    Posts
    76
    Get second opinion, attic units often are too short on supply also. Check TD. [18-22]

  9. #9
    Join Date
    Nov 2007
    Location
    Olympia, Wash.
    Posts
    192
    Nate, three months ago I spent somewhat less than you were quoted on re-doing my cold air return and adding a second return. I don't know if you are having "noise" issues" when the system runs, but my home -- four years old in March-- had a 16 inch single upstairs hallway return and it was choked down to 10 inches.

    Noisy... very noisy. Different company fixed the problem and all is quiet and more air is blowing. Temps more even, too. And... no more orange flashing light on the furnace. Second opinion wouldn't hurt.
    "Therefore, since we have been justified through faith, we have peace through our Lord Jesus Christ.." (Romans 5:1)

  10. #10
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,627
    Ask your tech to check the system static pressure.

  11. #11
    Join Date
    Dec 2003
    Location
    Citrus County, Florida
    Posts
    1,473
    3 1/2 ton needs 3.5 sq ft of filter. Allowing for the face area of your returns equals 4.19 sq ft. You should be ok as far as the filter sizes. As stated, you need the tech to measure static pressure. The 16in flex may be too small.
    Doug

  12. #12
    Join Date
    Jan 2011
    Location
    Vermilion, Ohio
    Posts
    31
    Quote Originally Posted by martyinlincoln View Post
    Ask your tech to check the system static pressure.
    +1, and maybe it couldn't hurt if it was a different tech. One thing I will say though, skr0oface's comment has some merit too, especially if your attic is as hot as you say it is. I know I wouldn't want to charge somebody a bunch of money to do something in a scorching hot attic unless I was really sure of my diagnosis of the problem and that the action being taken would make a formidable difference.

  13. #13
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,896
    Before spending that kind of money I would look into replacing your roofs shingles with the new reflective shingles, and you may get a tax credit for doing it. I've only read a little bit about them, but they look just like ordinary roof shingles but they say they can significantly reduce the roofs temp-thereby reducing the attics temp which will greatly improve your cooling systems capacity.
    Maybe look into exterior shading of your windows to cut down the heat gain to your home also.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

Page 1 of 2 12 LastLast

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