Let me first state I am a homeowner, not a contractor. I have a poorly insulated/sealed 3000sq ft home in southern Louisiana. I am steadily improving my insulation problems, and would like to rework the entire HVAC system in the near future.
The system in place is a 4.5ton and a 3ton Rheem 10SEER, with electric resistance heating. This is too much cooling for my home, despite its poor insulation, as a result of typical "throw more tonnes at it" homeowner mentality down south (I know someone with a 5ton system on a 1550sq foot home.,.. yes, its ice cold, and very humid inside). With almost 8 tonnes of cooling, I get short cycles very frequently with higher humidity, or by cranking up on the cooling anticipators, deep cycles with dramatic temperature swings, but much less humidity. I favor the deep cycles, as dehumidification is what drives comfort here, not cold air. Additionally, my larger unit has developed a leak in the evaporator coil, and despite a proper charge, the compressor is getting noisy.
The current duct layout sprawls across my attic from the center out in every direction, and only has one return air duct per unit, dead center in the attic where I would like to make a room. I would like to get two new, smaller heatpump systems, both with 3 zone controls, energy recovering ventilators, with a highly integrated control system.
The "Acadian" style construction of my home will make installation of a new ductwork system easy, therefore I plan on replacing all of the garbage ductwork in the attic.
Here are my expectations, I am looking for manufacturer recommendations so I can start consulting with a professional:
Variable speed compressor (not multi-speed)
Variable speed blower (not multi-speed)
LAT sensor, EEV, or other means for the control system to precisely manage compressor and blower performance to perfectly match zone heat/cool demand and system efficiency.
Electric damper motors.
Ethernet connectivity (optional, but hey, I am a network guy...)
Nordyne's upcoming IQdrive heatpump seems to have alot of promise, except for their pneumatic damper zone controls seem to be out of date, and according to a factory rep, aren't even compatible with the IQdrive system.
I'm looking forward to everyone's recommendations. NO, I haven't run a heat load calc on my place yet, but I plan on doing this soon. I'm hoping to throw whatever it takes at the place to get my cooling load to six tonnes or less. I keep my house at a reasonable temperature, around 74F, and around 68 in the winter.
PS: Since the 3 tonne unit is in good working order, I will have a new job for him in an 1850sq foot garage/recroom application (which won't be cooled continuously.)