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.

Ok that does make a difference. Still think it's overkill though. Ask for price on following: Performance 15 HP condenser FV4CN005 air handler Carrier Edge Thermidistat 9 KW pre wired staged heat strip. AHRI #3676240 3676240 Active Systems PERFORMANCE 15 PURON HP CARRIER AIR CONDITIONING 25HCC530A**30 FV4CN(B,F)005 28800 13.00 15.50 27600 9.00 16700 1 HRCU-A-CB 225 646 Yes Warranty and performance/efficiency numbers just as good as Infinitity system and would be my choice if Carrier s the brand you want. Personally prefer Trane because of electronic demand defrost which is a big deal for your area/climate. IMO This post was edited by tigerdunes on Tue, Jun 18, 13 at 16:32

1 and 3 would need externally mounted hot water coils and the pump as you say. Be nice to have the all in one unit from First Co. The Bryant quoted can do 16 SEER but not on a mismatched air handler, probably more like 14 SEER. The variable speed blowers on 1 and 3 are nice as well. The Carrier is a 2 stage outdoor unit that rates up to 17 SEER and would qualify for the $1500 tax credit and maybe other utility or state incentives. The A-S proposal is the builder model, not the Allegiance. Not quite as nice of a unit. The system quoted is 14.75 SEER, if a different air handler is used, you'd get over 16 and a tax credit. Pretty dumb of him to quote you the 4TEE3F31.

Thanks for the suggestion. Yes the old unit heated our home just fine. Also cooled it just fine, too except it cost too much whenever freon got low. Question: Why would you not purchase an extended warranty? Got quoted from a reputable company to replace the old unit. Their suggestion was the Trane 4YCY-4036B1075a which I believe is the XL14c gas-pack, correct? I can't find the spec sheet on it anywhere, just the basic info from Trane's site which is pasted all over dealers pages. Their customer "Specification Details" only says 14.20 seer, 80% afue, 2stage heat, s-steel hx, dual-speed Vortica blower. The rest is filled with useless marketing Terms like: * State-of-the-art fan system * Ultra-quiet operation * Climatuff compressor delivers superior reliability * Durable Weather Beater Top shrugs off the elements year after year * And don't forget those "functional louvers" and "sleek rounded corner guards" ;-) I have this 2008 dealer sheet Question: Is this the only sheet or does anyone have a real updated spec sheet? Model # nomenclature, detailed specs & installer docs are easy to google for other brands, not sure why they aren't indexed for trane. The dealer sheet states "Heating Input 56/75 or 72/96" but I don't know which it is since the model # nomenclatures I have are either old or don't cover packaged units. I'm sure Tigerdunes knows this answer off the top =) Chris