Replacing upstairs HVAC: ducting q's.. and Carrier or Trane?

14 years ago

2 story 7 year old home.. about 1800 square feet upstairs and 2000 downstairs. Upstairs AC being replaced. Some rooms have been hot, some cold, regardless of season... some have little airflow out of ceiling vents. Ducting is first issue - both vendors offer to replace existing big flexible tubes & distribution boxes with a new main metal trunk, 24 feet in each direction off the attic furnace/coil unit, and suspend it from the 2x4 roof trusses. One vendor offers dampers on each existing flexible tube "feed" at the main metal trunk; the other says just use the ceiling vent dampers to control the flow. One offers volume control dampers on each "wing" main trunk; the other has not said anything. One offers radius elbows atop the furnace/coil - called them "cheeks" (cute but descriptive) - to make the airflow smooth, rather than just putting a box atop the unit and attaching the trunks. One said ductwork would be $3600, the other said $4800 but has since reduced it to $4200.

Are the room dampers on each room feed a better approach or unnecessary?

Is the "cheeks" plenum better than a box atop the furnace/coil?

Next, Trane offers a 20i w/ a 95% efficient furnace, but is proposing an XV95 rather than the website-recommended 20i match XC95.. says the XC gets the efficiency without the cost of 3-stage furnace.. XV95 is only a 2-stage furnace. Both get power company credit of $750.

Next, Carrier says not to waste money on 95% efficient furnace for upstairs, and oh by the way, because it requires a PVC exhaust pipe, would involve working on roof to replace cureent 80% exhaust pipe, which for my house is a very steep roof. Trane sales rep said it was the installers problem, not his!

Third item.. evap coil.. Trane uses aluminum and Carrier uses ADP brand (and it is not tinned copper, which some have said is the only way to go) in order to get tax credit. Thoughts?

Overall systems:

Carrier: Infinity 21 - 24ANA136A33 outdoor AC 36000BTU; offbrand ADP indoor 3ton coil #C36A; 80% efficient furnace #58CVA090-16; #SYSTXCCUIDOI-B Control ("thermostat"); EER of 14 and SEER of 19. Includes new lineset and 10 year parts&labor. $12,650 excluding Energy Tax credit of $1500 and state credit of $350.

Trane: 4TTZ0036A1000A 20i outdoor AC (1.5/3ton dual), TUH2C100A9V4VA 95% furnace, 4TXCC043BC3HCA 3.5ton coil, TCONT900AC43UA communicating thermostat. EER 13? SEER 18+? Including new lineset and 10 year parts & labor: $13,950 excluding Energy Tax credit of $1500 and state credit of $750.

Carrier net: $10,800 (better ducting) Trane: $11,700 (95% furnace)

Flip a coin? Thanks!

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Comments (7)

ryanhughes
14 years ago
I certainly wouldn't want the XV95 if I was getting all other communicating components. The XC95 is the matching furnace for the ComfortLink II system. Personally I didn't even know the 900 thermostat could be used with any other furnace.

For the Carrier setup, if you wanted a Carrier coil a tin-plated one could still be used (10-year warranty) and qualify for the fed. tax credit (13+ EER, 18+ SEER matchups with Carrier CNPVP----ATA coils.
poppie_doppie
Original Author
14 years ago
Thank you very much, RH... I didn't know the Trane XV95 was not a communicating unit, and I shrugged about Carrier not using one of their better(?) coils. I'm surprised that each kind of short-changed the solution. Both seemed knowledgable and defended their choices otherwise. I've read your other posts re Carrier CNPVP--ATA coil so thanks for pointing me back to them. Would still appreciate answer on duct q's if you have time, tho' I'll bet you're getting busy with the heat coming back!
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I am trying to answer as best I can. I am not trying to be difficult, I was just not expecting having to face this major expense right after closing. The real estate market in Dallas is crazy & we were on a time limit to buy a home. Most homes have multiple offers as did ours & we had a short option period. I realize no one forced us to buy this home but I am just frustrated that 3 top rated companies are coming up with different recommendations. The system currently in place is working but if we are not going to be comfortable & it is undersized I'd rather bite the bullet now & replace before we do other work & paint before moving in. I would think that an inspector who told us he has inspected 17,000 homes in DFW would have given us a heads up that a 2 or 2 &1/2 ton mismatched system would be undersized for a close to 2,300 SF home, The ducts are located in the soffits below the attic (as was apparently done in the 60's in these homes) running in a t-shape down 2-hallways perpendicular to each other, The quotes I have received are to install all new ductwork in the attic so we can at some point knock out the existing ductwork & soffits & raise the ceiling height in the 2 hallways to that of the rest of the home. The all new duct work is approx $2,500-$3,500 of the quotes I have mentioned (although we would still have some cost even if we retrofit) . This would be done if we installed a 3, 4 or 5 ton replacement system including furnace, coil etc. I just have a hard time understanding how a 3 ton system would cool a 2,300SF home. I have attached a copy of the floor plan that the Carrier dealer created. He would not give me the load calc. We also requested an additional supply in the MBR and they will be installing a 2nd (additional) return. Thank you.
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ryanhughes
14 years ago
Airflow does not like to make sharp turns, so either elbows or turns with what are called turning vanes within each turn is preferred (turning vanes are sort of like "swoops" so as to avoid sharp angular turns). I would have no problem with the metal trunkline, insulated, with flex duct connectors preferably no longer than 6 feet, sized properly for the needs of each room. The dampers within the main trunkline, if installed, would help the installers balance the air distribution for the needs of each room. This is the best way to do it, but they need to take the time out to examine how much airflow each room will need, and the installers will have to be competent. I would clarify with this dealer how they will determine the airflow sent to each room; this would give you an indication of how much they understand airflow and its great importance to your comfort. These dampers are not something you would control, as they would be in the attic, but ideally they should only need to be adjusted once, PROPERLY. If the one who discussed radius elbows and volume dampers at each flex feed, and displayed an overall greater concern for the least airflow resistance, was the higher priced dealer, I would not be surprised.
poppie_doppie
Original Author
14 years ago
Thanks RH. Actually, I don't think I can tell which is the lower-priced one b/c the deals are packaged and the higher-priced one included the 95% efficient furnace but was the one less knowledgable about ductwork... just said the installer (who came by to inspect the ductwork) would take care of it. Now, your comment about 6 foot long flex ducts is a concern... mine are mostly 9-12 feet long with two longer. Should I get a bigger blower to push the air? Also, is the 80% efficient furnace ok or should I push for the 95%?
ryanhughes
14 years ago
Give or take 6 feet length runs are ideal for flex duct, but as long as the flex duct is done right (hung properly, no sharp turns, etc.), it should be fine. If you had significant issues with longer flex runs, I think you'd know if by now. So, no bigger blower necessary. The variable speed motor adjusts its RPM to maintain proper airflow anyway.

Sorry if I missed it, but where are you located? How often do you use heat?
poppie_doppie
Original Author
14 years ago
I'm here in Maryland.. South Anne Arundel County. Our house has a huge two-story family room so hot air moves upstairs quickly. In winter, the only cold room is my office over the garage. In summer, the MBR is cold but the other rooms are hot, even with the main plenum damper to the MBR almost completely closed... clearly duct problems. Thanks again!
poppie_doppie
Original Author
14 years ago
Do you recommend replacing linesets? Existing R22 ones had sealant put in them last year for a supposed leak, so I didn't want to re-use if it would cause problems. Prices are $838-$919 additional depending on vendor. Thanks Again!

Replacing upstairs HVAC: ducting q's.. and Carrier or Trane?

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Replacing upstairs HVAC: ducting q's.. and Carrier or Trane?

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