The OP didn't mention anything about cost in their inquiry but rather seemed interested in the advantages of this setup. So, the 803 or 8321 and TAM7 is a good combination and a nice balance of comfort/economy. This setup will overcool to dehumidify to an extent. With Comfort-R enabled this works well in controlling indoor humidity WHEN the systems are not oversized. Since they aren't buying a "top of the line" system, the TAM8 and ComfortLink II thermostat may not be worth it to them. To get much of the full benefits of these thermostats, the full communicating system (20i and TAM8) is required. They will however obtain the dehumidify on demand function with the XL900 thermostat. I was not expecting this to be an unreasonable upgrade charge -- perhaps it is, but the OP did not mention it (of course perception of cost/benefit is subjective). It's up for them to decide now. Tiger as always I do respect your opinion and don't necessarily disagree with you on the (sometimes) unreasonable upgrade charges and whatnot. There are good, competent, and honest dealers out there that don't charge an arm and a leg for nicer systems that benefit the HO. I think the OP is working with one of them compared to what you see elsewhere. There is a jump in cost for two stage systems across all brands. We are talking two complete change-outs here (albeit based on the descriptions they don't sound "overly" difficult -- absolutely no way to know for sure from here, though). I know you disagree, but it's all good with me and I hope it is with you. Differing opinions are good sometimes, right? It is ultimately the OP's call. My own personal experience with communcating 2-stage systems (not just Trane) is that they do provide comfort and control advantages that justify the upgrade cost in many cases. Look forward to seeing how this progresses. Ditto on the load calc! This post was edited by ryanhughes on Fri, Aug 16, 13 at 18:59

tigerdunes - I have learned a lot from reading your postings on this forum and I appreciate your inputs. Your minimum specs list has already been very useful (though a lot of sales people really struggle to find answers about some of the items on that list), and IâÂÂm leaning now toward the XL15i instead of the $660 more expensive XL16i. I still havenâÂÂt completely ruled out Carrier and Rheem, but a neighbor has had a 4-ton Trane XL14i for over three years and I like the way it does not seem to have collected very many of the evergreen needles that are everywhere around here. I am curious though just why the XL16i has so much trouble with dehumidification, and whether that is important to our well-shaded house just outside of Seattle. We havenâÂÂt bothered to run our heat pump in cooling mode for at least the last decade, so I remain mostly concerned with heating performance and expect to use very little cooling. Also, is the XL16i any less reliable that the XL15i, or is it just (as I understand from other forum postings) that it is more complex to hook up and hence more prone to improper installation? I am also puzzled when I compare ARI heating performance of the XL15i and XL16i. At 47 degrees their ARI heat capacity and COP are identical, and at 17 degrees the 15i has only 1% more heat capacity. The 16i has the better 17 degree COP, 2.86 versus 2.82, but it falls down on HSPF to 8.50 versus 9.00 for the 15i. This seems to imply that the 16i spends more time in defrost mode, but I do not understand why. Returning of your spec list, I assume âÂÂstaged backup heat stripsâ refers to the capability to selectively turn on part instead of all of the backup heat? Our old heat pump has this feature, but I have yet to find a sales person who can tell be whether modern systems can do this. One issue is not really relevant until our new heat pump is being installed, but opinions about it are so amusingly diverse I cannot resist asking. Our power utility offers an extra rebate if we install a lockout control. What should it control? We have a lockout set at 32 degrees on our old heat pump and I understood it prevents the backup heat from coming unless the outdoor temperatures is below 32 degrees. The âÂÂenergy expertâ I talked to at our power company agreed, but said the lockout should also turn off the heat pump compressor at 32 degrees to âÂÂprevent a spike in our electric bill.â I recognize efficiency is down at that temperature, but unless there is a lot of icing up it still seems to make sense to run the compressor. Sale personnel were about evenly split whether the lockout should turn off the compressor. Is there any clear answer on this?

ok guys, finally got the vibration absorbers installed on my freon lines today.. unfortunetly not very cold here tonight so the unit's not running alot. If you'll remember before I said there was a very loud Hum and vibration noise coming from a 5 ton hp. I first noticed the hum when I was sitting in the Den watching tv one night. ( please note the heat pump unit is located right outside the den so I wasn't that surprised that I could hear this hum in the den.. but when I went upstairs the hum was very noticeable in a spare bedroom and adjoining bathroom. So today my contractor comes out and installs 2 vibration absorbers on my freon lines..( 2 different sizes ) one is made by Mars ( motors and armatures inc ) the other is made by a company called "Packless" ( see thier website @ http://www.packless.com/splash.html. Once you get to the homepage, click on the logo, then on vibration absorbers for more details ) Anyway they have been installed and I can honestly say I notice a difference. Is the hum completely gone? well the answer to that is not completely downstairs in the den, but it does seem to be much better..In fact with the television on it is hardly noticeable. And my wife says I'm being Anal about it saying she can't hear anything but the unit ( which again, is located on the other side of the wall ) running. It is slight so she may be right, and of course that's a good thing. I can tell you there is a world of difference upstairs in the spare bedroom and adjoining bathroom. Hardly noticeable at all. In addition to installing the vibration absorbers my contractor also ran a metal rod down into the ground and then tied the freon lines to the rod to help divert vibration away from the house and down into the soil. so the big question is did this help? The answer is very much so...and if my wife is right, and all I'm now hearing in the den is the hp unit itself running, then it worked 100 %. But even in the worse case, it has helped tremendously. HOpe this helps you guys... Good luck with it and by the way... Merry Christmas Roland

Lennox is expensive most of the time. Real expensive. I have replaced many of fan motors on their equipment and they certainly charge for them. Since the cost of the part is triple that of other manufacturers, it kind of gets thrown on you @ $690.00. Lennox is big about making it very difficult to install other types of motors in their equipment, the physical size of the motor is engineered differently, and so is how it lines up and mounts inside the unit. They make the motors to where common/generic motor mounts that you get with generic parts just wont line up and they basically go out of their way to make you go through hell to try and install a generic part that matches the Lennox motor speed and specs - They really want you to have to go back with their motor, and that's something as a repair company I don't agree with, especially on weekends when parts houses are closed I have to tell a customer - "Well, we could fix it today because I have generic motors, but unfortunately since it's lennox, we can't and you have to wait until Monday when I can call these guys and go pick up the motor that fits this unit". I usually see strange motors from these guys, 6 speed options on 1 motor.. And the motor only uses 1 speed after it's installed in your specific system, but you pay for all those other speeds that your system doesn't use, that's for sure.