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.

Hi TD.. Haven't been on the boards in a bit so I apologize for the late response. Everything is working perfectly since the tstat was replaced on the 12th. System was charged and turned on and the difference from the previous system is amazing. The temps in the house are much more consistent and the upstairs is actually warm now. I think the replaced ductwork has made a big difference. The air flow upstairs seems a bit high compared to the downstairs (than the old system) so Ive got it on my list of things to ask the dealer whether it can be adjusted. They did install dampers on all the supplies so I'm sure something can be done. I am glad I followed the advice of many here and got the VP IaQ. It's full featured and very easy to program. I've set the Aux heat to only come on if outside temps are below 35 degrees and it seems to be working well so far. Will be interesting to see my first full month electric bill for January usage so I can compare it to the old system. And regarding the VP IAQ, maybe someone can answer this question for me. Over the weekend I noticed that the touch panel/display of the IAQ is loose inside the plastic frame. That is, when I tap it to change settings, it will move about 1/8" in all directions. Is this normal or should it be securely attached within its plastic frame? I am completely satisfied with the system and the installation performed by the dealer. Many thanks to you and Ryan for all your help during this process. It is greatly appreciated. Happy Holidays!!! Regards, Rich

Mike, yes. They have to give me the wired ODT sensor so I can lock out the heat pump. This was discussed between them and I several times before I signed on the dotted line and they had assured me this was possible. So as far as I am concerned they have to deliver on it even if it required ODT sensor. I just found another issue as I dig into this mess. I was trying to understand the fan behavior. In particular, from the sound it seemed the fan always ran at one speed. I was puzzled and digging into the thermostat menus, I confirmed this. The fan was either 100% or 0% speed. And it runs for additional 1 minute or so after the compressor shuts off (cooling fan delay). I found this odd - why did I buy a variable speed blower and why was I sold one. I mentioned this to the dealer and could get a satisfactory explanation. And then I checked the install guide - and it was there (see attached, in particular the graph and the table). There are four settings one can choose from. To really benefit from the variable speed the jumpers on the inside unit need to be configured in so called enhanced mode (option 4 in the table) where the fan starts at 50% speed and then to 80% for about 1 minute (fast cooling); the fan then stays on at 80% for 7.5 minutes (dehumidification); if necessary, ramps to 100% to get to the set point temperature and stays there as long as required, and ; ramps down to 50% and then 0% over three minutes to extract extra cooling efficiency. Well, this is not how my system has been configured. Mine is configured as option 2 in the table - 100% fan speed, followed by 1.5 minute delay - there is no variability of fan speed that can kick in. I have call in to my dealer...

Sure, and the ball on the half yard line is not a Touch Down. 'Comfort means different things, to different people... and because neither of you have a communicating system doesn't mean I can explain fully in text what that means.' But if you were comparing a Trane 2 speed non-communicating (legacy) system to a Goodman / Amana 2 speed communicating system and the price was similar for either one... which one would you choose? That is what changes the dynamics of the equation --- does it not? BUT, you have to know which is actually the better of the two and why. #Ah that old devil in the details again! On a side note: Have either one of you dealt with a customer who was a 'hot box'? Someone that is highly sensitive to heat? Not everyone deals with these issues... especially men. Women are known to suffer from what are called 'hot flashes'. And so because you don't realize this you are going to cut yourself off from 50% more business to actually solving a big problem? Yeah more unadulterated non-sense from me. Pay no attention to it.