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]