I recently had a 3 ton dual capacity Water Furnace Envision unit installed in my new 2400' (main floor)ICF house. the dealer tells me that it is the most efficient water to air unit on the market. The manufacturer posts a 30 EER  and 5 COP.
   Just out of curiosity, is this unit far above other brands or about the same as the rest of the pack?

   At this point (still under construction) I'm heating the main floor, no door to the insulated attic, three ducts to the full basement, and an open connecting door to the insulated garage. Thats around 6000 square feet and I haven't seen it go past stage 1 heat. So far I'm pretty impressed with geo.

Geo is pretty impressive.  :)

Climate Master touts their latest as producing 27 EER and 4.6 COP.

Of course any EER and COP numbers are totally dependent on what the entering water temp is.

Water furnace does have that COP and EER, but only if you maintain an entering water temp. of 53 deg. or something. It's only on an open loop (pump and dump) not on their closed loop. They get to make that claim, only with fine print...

I don't understand why the more efficient unit has longer run times in both heating and cooling. Unless running on first stage is counted as full speed run time.

Did you ask the installer the same question? I would be interested in what he says.

Do you live in a high humidity area? Since you are very heating dominate, you might want a two stage unit so that when cooling you can have longer run times on first stage to better dehumidify.

That would be the only reason I can see to pay for a two stage unit.

Where I live, we don't have to worry about humidity. I really can't offer any advice to you there. How much does a stand alone dehumidifier cost to purchase and run?

The longer run time is a good sign to me that it's not just the efficiency difference. Usually with longer run times, there will be a more comfortable, even temperature in the home. It's definitely not just about paying for a little bit better efficiency. Rather, it's about comfort. That's really why you want a heating and cooling system anyway, right? For the comfort!

Most likely, any one of the three systems would be comfortable, because they are geothermal. However, I would bet the most efficient unit is more comfortable than the less efficient ones.

What is the big deal with 2 stage systems anyway? So what the blower runs at two different speeds, I thought the lion share of energy consumed was used by the compressor. I would think you would want the blower speed to be fast as possible to minimize the amount of time the compressor is on.
 
As for the EER and COP ratings, so the manufactures tweak there numbers to get the highest rating possible? So when your shopping for systems, you could be comparing apples to oranges since they are using different input temperatures to get there ratings.  

 

On a two stage the compressor has two output levels. Stage one is usually 40% of capacity. It is not just the blower running slower.

Even though the advertising can be mis leading the ARI numbers are all done when testing at 32° incoming water temps. This is so you can compare apples to apples.

is that with running a desupe?

Klorinth, 
   What part of the country are you in? $26.5k seems pretty high compared to the cost in western KY. Maybe its just something thats less expensive here, I don't know, but the 3 ton Envision unit installed with desuperheater, horizontal loop, and all metal duct work(no flex) was less than $14k.

Greg

"Of course any EER and COP numbers are totally dependent on what the entering water temp is."

So if you are going to compare units can you just look at their tables and pick a constant entering water temp (say 50 degrees) and then compare the COP at that temp?

That is how I would do it.

I compared CM and WF and the Envision series seemed to be about 10% more efficient. That and their heat exchangers run at lower heads, useful in my situation. Definitely only compare COPs and EERs at same water and air conditions (flows AND temps). Advertised efficiencies are supposed to be at ARI-standard conditions, leveling the playing field. Envision gets 30 EER with 3 ton unit (only) at low speed at ARI standard 59 degree groundwater temp. CM around 27 EER at same conditions

Standalone dehus are fairly cheap but typically noisy and quite inefficient. Exception is those by Therma-stor, but those ain't cheap. Any central AC, geo or conventional, will typically remove much more water than a portable dehu, but the compressor needs long run times to do it - hence the interest in 2 speed systems - longer run times at low speed.

Two speed systems offer greater comfort (less noise, better dehumidification) along with greater efficiency

Dehus add sensible heat to the surrounding air at the rate of (3.413 Btu / hr per running Watt) + ~1000 Btus for every pint of water removed. Hows that for quantification? As a practical matter, it tends to mean that rooms with operating dehus are quite a bit warmer. This is nice in case of a cool damp basement in a heating climate / season, but miserable during cooling season.

A single speed unit along with a portable dehu waould result in less comfort at likely greater cost than a 2 speed without a dehu.