A little background seeing this is my totally newbie post. Am almost thankful when I was having this house built that I didn't know what I know now as I would probably have driven my builer nuts. Home was NOT a custom built home so the heating choices were basically not mine. Not that I would have known much of anything about hVAC during that time and really without this forum and the internet I'd still be totally stupid.
My background is as as cientist who works in the nuclear industry, dealing with radiation protection, degreed in same field and with some civil engineering background though I am NOT an engineer!
My home is approx 2700 heated square feet. The foyer is 2 story and I ahve a 19 x 19 bonus room over the garage. I also have 2 HVAC systems, one fo reach floor. We are not considering replacing the downstairs unit as it is mostly the upstairs one which is having the problem.
The upstairs is approx 1580 sq feet of living space. The system is composed of a Trane furnace along with a 2.5 ton Trane AC unit. Oddly, the coils used are a cheap 3rd party ( All Style I think? ) and not well matched unit. I am alos less than impressed with the ductwork ( there are 2 separate square/rectangular ( not sure of name ) boxes coming off the coils box along wiht the supply hose for my bonus room. One of these has a very hsort run folowed by a 90 degree bend and has I believe 3 flex lines attached, the third coming off the end of the line.
The systme has never been stellar since adding the bonus room ( room wass emi finished when home was built and finished out after the fact ). The bonus room also faces south. Bonus rom has a single 10 inch line feeding a pressure box to which 3 6 inch lines are attached feeding the vents to the room. In a nutsheel, in the summer I cannot keep the upstairs cool, and the bonus room often varies by more than 10 degrees. Last summer the upstairs would cool to 78 degrees at best and would be past midnight before it would get back below this mark. Currently I have closed a few dampers in order to keep our bedroom cool and bonus room about right. Thi swill not work in the summer.
Thus, I began getting quotes for a new system and have been amazed at the difference sin what people want to do! None thus far have even suggested leak testing my current system or fully load evaluating the home. The first company that came in did do a basic heat load calculation for the home and recommended 2 systems. They were a Lennox house.
System 1 was using a 13 seer Lennox AC unit and a dual speed 80% Furnace ( 2.5 ton unit + 3 ton blower ). They also wanted to run new ductwork from top to bottom. Basically a newer version of what i have but better installed. Price was semi expensive. Now, quote 2 was interesting. They wanted to keep my existing ductwork but wanted to use a Lennox Signature furnace for the variable speed blower and a 16 Seer dual stage AC system. Price about 60% more than the first system. I really disagreed with the decision to not replace the ductwork because the variable speed blower would make up the difference.
To me, the ductwork needs to be evaluated all by itself. Either it needs to be replaced, modified, repaired or nothing at all but it needs to be evaluated without regard to price of the system. Am I wrong in this assumption?
Most of the other quotes ranged from " winging it" to again keeping existing ductwork without testing it and using higher end equipment ( one was a 16 Seer Trane Heat Pump along with 80% furnace w/ variable speed fan and doing a hybrid system ).
The last quote is actually more interesting. It composed of replacing my ductwork, using a Carrier Infinity dual stage variable speed blower 80% furnace, Carrier coils, Carrier 16 seer 2 stage AC, and using a zoned system to provide a separate thermostat for my bonus room from rest of upstairs. Price with 10 year bumper to bumper Carrier warranty was in keeping with other systems. My trust level for the installer in this one is medium to high which is about what I have for the best of the rest.
I have one more installer coming out who is going to leak test my ventilation now, and will perform more elaborate load calcs. He does NOT do higher end equipment installations unless he has to as he prefers to design the ductwork well ( according to him ) and use single stage AC's and furnaces where possible to keep things simple.
I live in NC so we have plenty of hot days and usually mild short winters though we do occasionally get down in the teens.
Based on this, my questions are mostly am I headed in right direction pushing for having my existing duct tested ( even though I doubt it will be useable but again my gut instinct isnt based on knowledge, just how crappy the current air flow is and how hard it has been to keep the entire upstairs both cooled and evenly cooled ). I do have 2 separate air returns, one in the bonus room the other a few feet away in the hallway.
Next, is there a lot to be said for a simple 13-14 seer system and just properly designed ductwork versus new ductwork plus more complex solutions such as the zoned system plus variable speed blower and double stage AC unit? I have to admit I really do not want to have to climb in the attic very often to rebalance dampers to account for cooling season and heating season, and the thought of a well designed zones system to help keep the bonus room and rest of upstairs balanced is attractive. Assuming, of course, that it will work in that manner.
I am learning how difficult it is to find installers you feel very comfortable with as each seems to have their own twist. For example, the one who said I needed new ductwork to run a basic system but my existing ductwork would work with the more elaborate system. Just seemed inconsistent to me and would also seem if my existing ductwork were to have excessive leaking that a variable speed fan would not be a good thing!
I'm not very brand orientated and do want to ensure the replacement system is properly designed and evaluated. The last quote will come after I have had my existing ductwork properly tested which may well be the deciding factor in what system/installer I go with. assuming I do replace my ductwork ( which is what I am assuming will happen, or at the very least have what I have resealed and slightly modified as needed ), it will then come down to going with either a very basic system, no frills, 13-14 Seer level equipment and only manual dampers, or considering the more complex Carrier Infinity system with 2 zones to assist with temp control between the bonus room and rest of upstairs.
Of course, if the ductwork is properly sized and designed, would I even need the zoning? I'm fearful the heat load characteristics of the bonus room will make it very difficult at best to maintain constant temps between that room and rest of upstairs using a single stat in the hallway.
Sorry for long post and any comments are appreciated. I've already benefitted from the many posts I have read and probably learned enough to partially confuse myself )