Why upsize from 2 to 2.5 tons? I am not against increasing capacity when it is necessary and confirmed by a load calc, but was there ever a cooling problem when the system worked properly? 1000 sqft shouldn't need 2.5 tons. Ductwork should be sealed and insulated completely.. Oversizing decreases humidity control. I somewhat disagree with the tech's opinion that a 2-stage system would run on high stage all the time. When sized and set up properly. this is not true. Think about the milder days where you need better humidity control without full cooling capability. 2-stage systems are an improvement, though those which feature a Copeland Ultratech scroll compressor (most including all Carrier) have a net capacity of around 75% on low stage. So yes, there is not a huge drop off but considering most systems are oversized to begin with, the longer runtimes in low stage and the lowered airflow will *tend to* result in a quieter, more efficient system with more even comfort throughout the home. If a load calculation (which should be performed) reveals that a 2 ton will meet the upstairs' load needs, then a 3 ton two-stage system would be a mistake and negate the advantages a properly sized 2-stage system has to offer. This post was edited by ryanhughes on Thu, Jun 6, 13 at 19:06

Just had one installed. Do not let anyone install as you mentioned. You need a concentric vent. In my area not one of the 4 a/c contractors that quoted me had installed a 95% furnace. By chance the contractor I used went to a class given by the a/c distributor the night before. Please go over the specification with the contractor. there are certian requirements base on unit vent/combustion sizes. this may vary with manufacture and furnace. Some require minimum/maximun number of pvc elbows to balance system base on condition and lenght. You can go thru the same vent hole but you will need a new vent assembly to pass thru roof and is designed for your concentric vent. It should be part of the kit. Use this link to see one. Play video. http://www.alpinehomeair.com/viewproduct.cfm/productID/453056394/p/Goodman_DCVK_20

RE: AC and Furnace replacement NEW DETAILS In Atlanta / one-story / 1,800 sq ft / furnace in attic / easy installation / both quotes from reputable contractors / Already at top of my budget (including rebates/tax credits) without upgrades, but can finance if some upgrades worth it 2 Quotes, both @$6,000 (another Carrier quote of $9-11,000 was so out of budget) Thank you for your insights. See new details/answers below. "What mdl. thermostats? What mdl. evap coils? These are not insignificant details." "Generally you can not pair a two stg. condenser w/out a var. speed furnace" CARRIER 4.0 Ton, 16 Comfort Series Gas Furnace 16 SEER Rating Comfort Series 16 A/C (24ACC648A003) Coil (CNPV 4821) 80% Performance Boost Furnace (58PH0110-16) Carrier Thermostat Edge VERSES TRANE XV80% afue 100,000 BTU Variable Speed 2 stage gas furnace Model# TUD2C100A9V5VA and the Trane 4 ton XR13 SEER high efficiency R410a Puron air conditioner Model# 4TTR3048D1000A and Trane 4 ton all aluminum cooling coil Model# 4TXCC049BC. Trane Touchscreen Super Dehumidification Thermostat Model# XL803 "considering the carrier is a 2 stage comfort series and costs $1,000 less, go with it..." It is $1,000 more (not less). Is the long-term savings of variable speed worth the upfront upgrade cost? "certainly would not recommend the larger XV80 furnace. It will only cost you more to operate..." Thank you, we were questioning this "are you familiar with heat pumps. You want one if you don't have one�" That would be a $600 upgrade. Is this worthwhile? "Dealers are quoting new line sets?..." I don't know what this means? Still wondering *Is there a significant difference between Trane and Carrier parts/engineering? *Is there another suggested brand within range of these systems? *Who are you guys answering these questions? ïÂÂ

dadams your ductwork system needs a complete evaluation. Regardless whether you go two stg or three stg, you will not see any noticeable improvement to rooms that have comfort issues. ask dealer to make recommendations for improvement. The problem with heat exchanger is not covered by warranty? while Carrier and Bryant are fine furnaces and really are the same depending on model, neither offer a true modulating furnace in their product line. I am told one will roll out for next heating season. A true modulating furnace that moves up and down based on demand would be more effective for your problem areas than the two or three stg Carrier/Bryant. York/Luxaire offers mdulating furnaces at 97-98% AFUE efficiency. And I agree with previous post about HPs. A dual fuel system is worthy of consideration especially with your heating fuel being the more expensive propane. IMO