Louisnana home HVAC/heatpump upgrades
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upcoming IQdrive heatpump seems to have alot of promise, except for their pneumatic damper zone controls seem to be out of date, and according to a factory rep, aren't even compatible with the IQdrive system.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.)
Have you though about incorporating a whole house dehumidifier for real humidity control during the low/no cooling load conditions? A whole house dehu provides <50%RH without a/c operation or regardless the inside temperature. Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
Currently, there are no ducted Variable speed compressor heat pumps.
2 manufacturers have 2 stage heat pumps, that offer 50/100 capacity as their stages.
I'm not a Carrier dealer. But would recommend a 2 stage Carrier Infinty heat pump with teh Infinity zoning system.
Its a modulating zoning system, that will also help to prevent short cycling at low load conditions.
Last edited by beenthere; 07-20-2008 at 11:10 AM.
Reason: spelling/word corrections.
I think you meant "no" beenthere.
Nordyne's technology is simply using what has been available around the rest of the world for years. Nordyne uses Panasonic compressors.
Check out Daikin, Sanyo, and Mitsubishi. Each have in their respective VRV/VRF lines (Variable Refrigerant Volume/Flow) fully variable compressors and fully variable indoor air handlers. Each air handlers is a zone, with up to nine air handlers connected to a single outdoor unit (This is not to be confused with the what these manufactures call multi-split systems where there will be 2, 3 or 4 indoor units to one outdoor. These are not VRV/VRF systems). Outdoor units range in size from 3 to 5 tons.
The systems have highly sophisticated central controllers that can be tucked away in a utility closet with small sensors in each zone (the size of a match book) linked back for the controller to monitor the zone. Web access is available and home automation systems can be incorporated too. When there is a problem with the system the controller will tell you where and what the problem is. There are sensors throughout to monitor all operations. Because of this these systems rarely self destruct due to poor installation issues.
With the ability to be fully modulating (Daikin air handlers operate as low as 10% of its nominal rating), the system has almost continuous run times, and thus, very good humidity control.
Since the zoning is done with multiple air handlers, complex ducting is eliminated along with damper motors and such. These are the top of the line comfort systems that have been in use around the world for years.
But you have to cosider the possible loss of resell value, when a prospective buyer, doesn't like seeing a unit in almost every room.
Using ducted air handlers the installation would look just like any other home. The small compact size of the air handlers allows for ease of installing multiple units in the attic, crawl space, basement, or other area. Personally, I don't like the ductless units as it concentrates the air flow and the conditioning of the air to a relatively small area. I would only considered a clean ducted install and I think the OP was looking for that too.
Originally Posted by beenthere
And is this 3 or 4 times the cost of a conventional 2 stage heat pump.
If the OP wants variable and not staged, as stated, then this is what is currently available. While I will agree the cost of a VRV system can seem high, it must be compared to what the other options are.
Originally Posted by beenthere
For a home that typically has two systems, one up and one down, the cost for those two systems - assuming higher end two staged heat pumps, is not much less than a single Daikin with four indoor air handlers. The user ends up with four zones instead of two and a top end comfort system.
Installation costs should be less as running the refrigerant lines should be an easier task than the expansive ducting required for a typical multi-zoned system. No bypass ducting, no over sized ducts, no requirement that ducting take up space going from one floor to another, and no dampers.
LAT controlling variable speed compressor
If a variable speed compressor is monitoring system performance based on the LAT sensor, even with just a two stage blower instead of variable speed blower, wouldn't the compressor performance adjust automatically to airflow as it affects the LAT?
I don't know how much Nordyne's IQ drive heatpump will cost... How much more does their IQ drive AC cost over a very high efficiency two stage outdoor unit?
So nobody makes a variable speed blower?
I did read about the mitsubishi system yesterday, I think a ducted system is the right way to go in my house.
Nordyne IQ drive heatpump
I forgot to mention, a nordyne rep informed me that IQ drive heatpumps are coming early 2009. 21 SEER and 9.5 HSPF, IIRC.
Do any of the VRV/VRF split multi systems operate as AC and heatpump? Daikin appears to be either/or but not both. I do like the layout of that system, I think five tonnes might be attainable in my house (especially considering the zoning can follow the solar load from east to west).
A heatpump will heat and cool..