Results 1 to 8 of 8
  1. #1
    Join Date
    Jul 2006
    Posts
    24

    Ducting issue or replace system?

    I have a 17 yr. old Lennox system (4 ton), metal ducts (except at plenum), 30 yr. old house (Dallas, Tx), 2500 sq. ft., 6" insulation & w/high pitch metal roof. Last elec. bill was $330 (of which I figure $200 of it for ac)
    The problem is kitchen and master bedroom/bath always run 3-4 degrees warmer due to being furtherest away from system (attic mounted).

    On 100+ degree days, w/thermostat set at 77-78F, system holds temp. fairly well with run times of probably 30-45 min. on-time & 10-15 off. Even at 80F (outside/night) on-time usually 10 min. or so. (I know, heat load in afternoon--I need more insulation)

    The A coil has a small leak requiring about 1-2 lbs. freon beginning each summer. (remember, we use a/c about 6-7 mo. of the yr. here). Had system checked a few months back and tech said compressor was in good shape, A coil had small leak and rusty, contactors were marginal and A coil could use cleaning. Also found all flex at plenum had small air leaks. All return air ducts have been checked and any leaks fixed. Also, instead of using Y's or sub boxes for split off of ducts, most ducts just branch off larger runs for various rooms.

    I called 3 contractors for system bids and here is what I got:

    Company A) Would redo flex at plenum to remove the mess of kinks and turns. Correct other duct problems utilizing as much of my existing metal duct as possible.Increase return duct size from kitchen, correct ducting to bedroom/bath area for more airflow, add to vents plus return for enclosed patio we would add in. Recommends Amer. Standard 14 SEER (R22), 4 ton w/5 ton coil for extra cooling = 15 SEER?)

    Company B) Found no ducting issues except mess at plenum.
    Would install Amana 4 ton 15 SEER (RCE 48 w/410 A) plus additional ducting at patio.

    Company C) Found all the ducting to be a mess and poorly designed. Would scrap all, redesign and redo w/flex & add patio ducting. Recommend 5 ton, Amana 16 SEER.

    The only company that has not pushed a new system is company A which feels that a large part of the comfort issue is due to ducting problem.

    Assuming my system works now, would'nt it be smarter to go with company A in correcting the assumed duct problem before investing in a new system? If ducting improves comfort level and cooling, would it be smarter to run my system until it has a major problem? Company A is willing to do the duct work first w/no pressure on a new system. Both B & C were pushing for new system. Company B & C did heat load calc's and have a comfort guarantee in writing (for what thats worth) Company A measured return & output vent sizes etc. but I never really saw a heat load calc. I think he thinks that since my 4 ton is doing an adequate job now, and with improved ducting, more insulation, larger A coil and more efficient system that 4 tons would be fine. Company A--very helpful, answers all questions, many yrs. in business--dealt with owner. Company B & C--old established companies, dealt with sales reps. All pricing seems reasonably close in comparison w/ exception of duct work.

    In researching both Amana and Amer. Standard, both seem to be good systems. However, Company A pointed out that Amana derives their SEER using 80F-95F (smaller envelope that makes SEER look better) while most others use 75F-100F. Of course Amer. Standard has spine fin coils (I won't go there).

    Also, I did some research on EER & SEER. Since EER is efficiency of unit at higher outdoor temp. vs. SEER being seasonal avg., I would think that EER would be just as or more important in hotter climate (Dallas) at temps. in the summer of 100+ for most of the summer. Can anyone find EER ratings on Amana & American Stand. 14/15 SEER units? I looked at websites, but did'nt see them listed. Why is that?

    Can I get some others thoughts on all this?

    [Edited by shelby1 on 08-21-2006 at 10:33 PM]

  2. #2
    Join Date
    Feb 2005
    Posts
    249
    I'd go with company A,except for the commnet on how SEER is derived,they all use the same temps..



    I'd still go with A,but it's time to replace the old system too.

  3. #3
    Join Date
    Aug 2006
    Location
    knoxville ,tn
    Posts
    51

    Thumbs up my opinion

    I can not judge a company not knowing them ,but I think company 1 is on the right track. Sounds like to me you only have a duct issue.Upsizing the evaporator coil to a 5 ton does'nt sound like a bad idea either, although your system being 17 yrs old it probably will not last much longer.I would repair ductwork first.Give it a try, you can allways replace unit later,good luck.

  4. #4
    Join Date
    Feb 2006
    Posts
    468
    I like A's focus on fixing the ductwork. I'm not sure I agree with oversizing the evap in a humid climate nor with buying R22 equipment so near its phaseout (2010)

    Maybe the thing to do is pay A to just fix the ductwork and run for luck awhile longer with the equipment you have.

    The recurring theme around here is that so many houses have poor ductwork.

  5. #5
    Join Date
    Nov 2000
    Location
    Memphis TN USA
    Posts
    6,969
    First, your system is running fine now except for duct problems. I also notice you plan to add additional space to the cooling load. That space might be to much. Now your system is not running 100% of the time, so you do have extra capacity.
    Also, you don't want to put a return in the kitchen.

    I would fix the duct problems. It must be fix eventually. might as well do it now. You might want to upsize the return ducts now for a possible increase system size.
    While you are at it, 4" media filters would be a great upgrade.
    If the superheat ain't right it ain't charged right.

  6. #6
    Join Date
    Jul 2006
    Posts
    24

    Ducting issue or replace system?

    Watercop--and others--thanks for your input. In Dallas, our humidity is not all that bad for the most part. Company A states that by using a matched 5 ton coil this would give the system a little better cooling on really hot days and is almost like getting a 5 ton system for little over a 4 ton price. Plus, being a variable speed he claims the first stage cooling is primarily for humidity control. Then, after about 10 min. if set temp. is not satisfied, hi speed cooling kicks in and completes cycle. He further states that the newer systems generally have about 20% more airflow than ones like mine and that plus humidity control and more efficient system will make a big difference in the comfort of all rooms (plus duct correction).

    I would love to hear more of you guys input on this and can anyone tell me EER ratings for both Amana & Amer. Standard 14/15 SEER units? He is quoting a 15 SEER (14 SEER outdoor unit w/matched 5 ton coil) 2 stage furnace & 1 stage cooling function. Am I understanding all of this correctly?

  7. #7
    Join Date
    Jul 2006
    Posts
    24

    Ducting issue or replace system?

    Kim, you are correct. I forgot to mention those things. The enclosed patio was originally built as literally part of the house (completely under the roofline). It has atrium doors that open onto the patio from both the kitchen on one side and master bedroom on the other. Previous owner added exterior wall (about 12') that faces north and none of the windows ever get direct sunlight. Total sq. footage is about 200 sq ft) In past summers we have opened doors from kitchen and bedroom on 95F plus days w/no noticable additional runtime on unit. Two companies said w/ additional insulation and the way the room was built that still a 4 ton should handle w/no problem.

    As for the return ducts being larger, the return vent is in the wall near floor level in the dining room and den wall (ajacent to kitchen, but not in kitchen). He feels not strong enough flow coming out vents in kitchen/bedroom areas to properly cool. Plus said my 4 ton is only getting about 3 tons of return air now. Yes, I am going to a 4" filtration w/new system. If I understand right, this would mean that I may never have to worry about the aspect of dirty A coils degrading system efficiency like the cheapo filter do.

  8. #8
    Join Date
    Nov 2000
    Location
    Memphis TN USA
    Posts
    6,969
    Many people undercondition attrium rooms. It takes the edge off and allows them to be considered heated and cooled space for selling purposes. Typically you are not in the attrium in the heat of the day anyway.
    If the superheat ain't right it ain't charged right.

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