Not so fast boys & girls; there's something else here that I didn't expect to see. The technical manual for the 25VNA series says in the Electrical Data that the Compressor LRA/RLA, FAN & MCA for the 024 & 036 are in fact all exactly the same! The 048 & 060 are likewise the same but of a higher value than the 024/036 series. The only electrical difference between the 024 & 036 is the MAX FUSE or CKT BRK AMPS (30-amps/024, 40-amps/036). When you compare the dBA levels between the 024 & 036 you will also notice the there is a substantial difference in MAX RPM between these 2 machines. That may be due to a programmed difference between the 2-sizes and could be what the trainer is alluding to. The shipping weights & operating weights are also exactly the same for the 024/036 as are the 048/060. Ditto for the dimensions, all 4 share the same size cabinets. This again may mean the 024/036 and the 048/060 are mechanically the same units. Maybe the dealer trainer knows something we don't! I guess we'll have to wait and see what develops. SR Here is a link that might be useful: 25VNA Carrier infinity Greenspeed Installation Manual

Heres a Link: http://www.greenbuildingadvisor.com/blogs/dept/musings/saving-energy-manual-j-and-manual-d Even when they do the calculations, the results are usually wrong In his posted comment, Bailes raised an interesting point: the problem of “garbage in, garbage out” (GIGO) Manual J calculations. Several energy experts have commented on the GIGO problem, including John Proctor, Hank Rutkowski, and Allison Bailes. Hank Rutkowski, the mechanical engineer who wrote the original Manual J document, was recently interviewed for a profile posted on the Green Building Talk Web site. The piece notes, “Rutkowski estimates that only 10% of heating and cooling equipment sizing decisions are based on some type of Manual J calculation and that less than 1% of the jobs are based on an aggressive implementation of the recommended design procedures.” Rutkowski explains the GIGO problem this way: “Manual J is a good tool if you use it aggressively. Follow the rules and it will give you a reasonable margin of safety. But the average contractor says, ‘Better safe than sorry,’ so he fudges here and there. He adds 5 to 10 degrees to the summer and winter design temperatures, calls the building ‘average’ instead of ‘tight’ and doesn't take credit for shading by interior blinds and drapes. Then when he finally comes up with a load number for sizing, he throws in an extra half-ton of AC just for the heck of it.” For a high-performance home, sizing by Manual J may still result in oversizing Several years ago, I had a conversation with building scientist Joe Lstiburek about air conditioners installed in Building America homes in Las Vegas. “HVAC designers are committed to the institutional oversizing of air conditioning equipment,” Lstiburek told me. “The average system is sized at 150% to 200% of the requirements of Manual J. They oversize because they don’t know what they will get for a building envelope, and to compensate for duct leakage and inappropriate refrigerant charge. If you size according to Manual J, there is already a fudge factor built in. But most designers then add another fudge factor.” According to Lstiburek, their experience proved the high-performance Building America homes in Las Vegas could have had HVAC systems sized at about 60% of Manual J. To be conservative, his team recommended installing systems sized at 80% of Manual J. Does oversizing matter? There are strong arguments against routine oversizing of HVAC equipment. The best argument is simple: oversized equipment usually costs more than right-sized equipment. Oversized equipment suffers from short cycling. For example, an oversized furnace brings a home up to temperature quickly, and then shuts off. A few minutes later, it comes on again, only to shut off quickly. Many homeowners find the see-saw sound of a short-cycling furnace to be annoying. When air conditioners short cycle, the units don't run long enough to achieve much dehumidification ��" at least in theory. (During the first few minutes of operation, an air conditioner cools a house. But not enough moisture has collected on the cold coil or on the pan below for any water to have actually gone down the drain. When the air conditioner turns off, all of the moisture in the pan and on the coil just re-evaporates.) The conventional wisdom may be wrong, however Increasing evidence shows that energy experts have exaggerated the negative effects of equipment oversizing, however. Studies have confirmed that oversized furnaces don't use any more energy than right-sized furnaces. Moreover, newer modulating or two-speed furnaces operate efficiently under part-load conditions, solving any possible problems from furnace oversizing. Although there are ample reasons to believe that oversized air conditioners are less effective than right-sized equipment at dehumidification, at least one field study was unable to measure any performance improvements or energy savings after replacing an existing oversized air conditioner with a new right-sized unit. The bottom line The main reason to choose right-sized equipment is to avoid paying too much money for equipment you don't need. A Manual J calculation will ensure you don't spend more than necessary for your furnace, boiler, or air conditioner. Moreover, a Manual J calculation will provide room-by-room heat loss and heat-gain information that is essential to good duct design. Without good duct design, you're running the risk of comfort complaints.

What size living area is this upstairs zone?...how do you filter your return air?...if 1" filter, i would add a pleated filter media cabinet, preferably Trane's Perfect Fit...it gives you superior indoor air quality and protection of blower motor and evap coil....while the coil selection is a good match, I would ask dealer about this coil that reaches 15 SEER. 5865924 ActiveSystems TRANE XR16 TRANE 4TTR6030B1 4TXCC005CC 3890 *UD2B060A9V3 28800 13.00 15.25 1RCU-A-CB All 240 A very nice system... IMO

mike_home, you make the perfect argument for why Manual J should be mandatory for all HVAC contractors. It would protect the customer from hacks and unscrupulous contractors. Smaller equipment means less cost for electricity over the life of the AC unit and less cost up front which saves the buyer money. The electricity savings is why the utility companies and many states are making it part of their mandatory requirements to have their HVAC contractors perform Manual J. Here's a good explanation from Dean Heating and Cooling on HVAC Talk Forum that explains the benefits of using a Manual J and also talking about proper duct design (Manual D). "A load calculation known as Manual J is the only correct way to determine heat loss and heat gain. Once equipment size has been determined, the duct system is designed by Manual D. These are design protocols formulated by ACCA. Duct design takes into account the location and potential gain (or loss) of having ducts in an attic, crawlspace, or even exposed on a roof. You are correct the installing a larger air conditioner on an undersized duct system is pointless. We have all seen it many times. Frequently, putting in smaller equipment delivers greater comfort when the existing equipment is too big. For example, a 4 ton unit on a 2.5 ton duct system can only deliver 2.5 tons worth of air flow. The oversized equipment still uses the electricity for 4 tons of cooling but the delivery system still limits what arrives in the space. The equipment actually uses more energy because of inadequate air flow. Plus it cycles more often than smaller equipment so its life is shortened." Here's a good discussion about Manual J calculations also from the HVAC Talk forum. There's an HVAC designer and an HVAC contractor that post over there that seem to have the most input on Manual J. Their user names are "dan sw fl" (AKA Designer Dan) and lkapigian.