SEER / EER - you have to watch the measurement conditions. EER of 30 for cooling may be with entering water of 59, a temp not available in Florida.

Feeding open loop geo with a domestic well pump can be done, but cost of operation (well pump power) may render it relatively inefficient. Well pump may not happily handle the 10-50x greater flow. Well pumps aren't particularly efficient, 50% or less, and pumping water to 50 psig and then throttling it back down to the 5 psig or so needed for a geo unit is a substantial waste on top of the low efficiency.

I believe the Air Generate does qualify for the Energy Star tax credit since it is both AHRI listed and has an EF > 2.0.

Unfortunately I also believe it works by having single wall refrigerant lines in direct contact with potable water. That likely contributes to simplicity, efficiency and lower first cost (no water plumbing or water pump)

The refrigerant side pressure will greatly exceed the water side pressure during the run cycle. I can imagine failure modes where refrigerant, oil, and possibly even acids and whatnot originating from compressor internals enter the water.

IMO these failure modes become significantly less probable if the system incorporates a double walled and vented heat exchanger (leaks on either side likely go to atmosphere, the least harmful outcome).

Codes and their enforcement vary widely, and I don't know them all. I can tell you that as an engineer and contractor I wouldn't recommend, sell or install a system for potable water use that does NOT incorporate a double wall and vented heat exchanger or functionally equivalent design. Safety of potable water trumps efficiency and cost considerations for me.

I don't know if the Rheem or upcoming GE Hybrid storage tank HPWHs (these units may be one and the same - GE has resold Rheem models in the recent past and may still do so) incorporate vented heat exchangers. Obviously, I hope they do.

I'm told the Geyser add-on unit does incorporate a vented heat exchanger, though I have not disassembled the unit sufficiently to verify that.

Geonovice:

A typical irrigation pump is about 1 hp. Most 1 hp pumps use 1 - 1.4 KWH. A typical geothermal pump is 1/12 to 1/6 hp I think and uses 0.2-0.4KWH. A typical four ton unit uses about 3-3.4 KWH so you would destroy the SEER/EER using that large of a pump. Example: 48000 BTU/3000watts = 16 EER. If you used a 1 hp pump at 1.3KWH then 48000/(3000 + 1300 - 300) = 12 EER. And if you got a two speed unit the EER would fall even more drastically.

The two speed unit is a very good investment. Why? Because your unit is sized for worst case use which is generally only 3-10 days per year. The rest of the time it is over sized. People will say you get better dehumidification too but studies do not support this.

I think you'll be happier with two systems. I had a single unit for a two story house in TX. If the upstairs is comfortable the downstairs was a tad cool while if downstairs was comfortable the upstairs was a tad hot. I moved within that neighborhood and got a two story with two units - MUCH better. Same for here in FL where I have two units (up/downstairs). I went with a two speed downstairs and single speed upstairs. The reason is the two speed 4 ton was not much more than the 1 speed and had a better warranty. For the 1.5 ton unit the two speed was almost $800 more.

Bigger is not better. Nor is it more comfortable. I do highly recommend a manual J no matter what you do. And I recommend a 2 speed for the larger unit. If you go air source look into Goodman and Amana (great warranties and reasonable prices).

Regarding the ultra high EER/SEER numbers - Engineer is right.  Also, the cost savings drops dramatically.  A 11 SEER unit is about 10% cheaper to run than a 10 SEER unit.  However, a 20 Seer  unit is not going to save you much over an 18 SEER unit. A  four ton 20 SEER unit at rated conditions uses about 2.4KWH.  A four ton 18 SEER unit uses about 2.67 KWH.  While this is a 10% more efficient unit you are talking about 0.27 KWH per hour of run time (less than a nickel an hour at FPL rates).  Over a 3600 hour cooling year you might save $100 (not $180) because the unit rarely will run at full load.

Suggestions:
1.  Demand a manual J calc (pay up to $100 to get it if necessary)
2.  Get a proper sized unit (more comfort and less up front cost and lower operating costs)
3.  Get bids from 3 different contractors
4.  Ask you neighbor who they used and if they would use them again
5.  Check with BBB (Better Business B)
6.  Do not use Joe and Me Fly by night - a quality install is worth a little more money
7.  Ask for estimated cost savings and pay back calculations if somebody starts waving ultra high SEER/EER units at you.
8.  Don;t get too hooked up on SEER ratings above 18 to 20.  Keep in mind that companies optimize units to run at 80F outdoor temp because that is the testing temperature.  The unit may not be optimized for the 88 degree 70% humidity you have most of the time.

Best of luck.

Alex

So Engineer, let me pick your brain some more. I'm looking at Florida Heat Pump's performance sheet on their Aquarius II AP Series AOP61, which I believe is roughly a 5 ton unit. They show an EER of 27.7 partial load & 18.5 full load with a ground loop temperature of 77 degrees. Although, my current plans are aimed at an open loop system, this temperature is almost the exact temperature of my well water this time of year. I haven't considered the COP numbers because heating is almost never needed in this region. Is this a valid comparison? How would these specs. stack up against a comparable air to air system? Thanks again.

Alex_in_FL You are right, my well pump is 1 hp & I had wondered if the pump would eat up some of the geo savings. So let's assume that my water quality/quanity checks out OK & I decide to go with an open loop geo system. To remedy the pump situation are you suggesting that the irrigation well pump be removed and a much smaller pump be installed down the well in its place? Or is there a way to have two pumps, one for the open loop & the other for irrigation. Or could a large storage tank that is filled by the irrigation pump and drawn from by the smaller geo pump be used. 27 GPM into the tank 12 to 15 GPM out, when the unit is running? For those of you who understand wells, pumps, & water flow this probably seem rather "Rube Goldberg" ish. As you can tell I have almost no clue, but I'm learning. I do not want to give up the irrigation, as it saves me almost $50 dollars a month compared to my water bills before I had the well drilled. Reguarding two systems vs. one: I have a home up north with a single ac system on a two story plus basement home & know what you are saying about "hot upstairs, cold downstairs" etc. In that home we run an extra window unit upstairs during the summer. However, My Florida home is all on one level & the 1.5 ton unit only cools the master bedroom master bath & a small office/den. For this reason I don't see the advantage of the dual system. Can you site other advantages. Thanks again.

Does your well produce free-flowing water that your irrigation pump boosts pressure? If so a second reinjection well with a very small pump sized only to push water thru geo unit and back down reinjection well could be an economical choice aside from having to drill the reinjection well. Place it as far as possible from the irrigation well. Have water tested and matched against geo unit heat exchanger specs.

I'm partial to Waterfurnace Envision, but FHP Aquarius II series has similar performance. FHP lagged for years, then got bought out (Bosch?) so appears to have turned a new leaf. WF is a more stable player in this biz.

Pay attention to Alex's advice, although I disagree with his remark about 2 speed and dehumidification - I haven't seen the studies (if any exist) but have seen the pleasant, low humidity, low noise, even temperature results of a two speed system with its longer runtimes coupled with reserve capacity for extreme weather or house parties, etc.

Engineer, I'm pretty sure I do not have free flowing water, but, correct me if I'm wrong. I would have to turn off the pump power & let the tank pressure drop to zero to see if water continues to flow, right? The times that I have made repairs to the irrigation system I don't recall any continued water flow without pressure in the system. Reguarding the reinjection well, If I do have free flowing water, You are saying that the free flowing water from the irrigation well is boosted only by the secondary geo pump and the irrigation pump is not used at all with the geo system. But, could it still be used as an irrigation pump/well? In addition, I would need a second well & its sole use is to dispose of the heated water. Or did you say a second reinjection well? If I do not have free flowing water are there options other than the 1 HP irrigation pump? I think the phrase "second irrigation well" has me confused. Reguarding WF vs. FHP I have been considering both of these companies, & have read more favorable comments about the WF Envision on this & other sites. Thanks again.

Engineer,
The one link mentioned in this thread said heat pump water units that were add-ons were not eligible for energy star, but the Energy Star Web site doesn't mention that. So maybe the Air Generate and other add-ons are eligible but it wasn't specific. I like the GE and Rheem option because you could shut off the element and be down to one tank with the desuperheater and still be much more efficient than plain ol' electric. Don't know much about the mechanics of it but I trust your recommendation to steer clear of the Air Generate because of its construction. I'm skeptical of a unit that's cheaper than the others anyway, but thanks for your input.

I believe to be eligible a unit must have EF >2.0 and be AHRI certified. Last I checked only AirGenerate was listed. I'm not sure Rheem / GE units are actually in production yet.

Geyser is not listed, but ought to be, unless something is wrong such as can't quite make EF = 2.0. I have on my todo list to ask them about AHRI rating and energy certificate.

Regardless of how you heat  domestic water a desuper will be ineffective without its own buffer tank. It heats water slowly and not at times when you need it, so the only way around that is to store it separately. If you can't or won't plumb a desuper to its own buffer tank don't count on its savings to ever pay off its cost.

Don't rely solely on my analysis of the AirGenerate unit. I haven't actually inspected one to verify my findings.

Ideal is to use two pumps for a GSHP and irrigation or domestic water system. A smaller than typical one to provide the low pressure for geothermal and a surface booster pump where higher pressure is needed.

Engineer: I cannot find the large study I read but see this one: http://www.fsec.ucf.edu/en/publications/pdf/FSEC-CR-1641-06.pdf   In paragraph 3 of the excutive summary, it states that a properly sized unit in some cases provided energy savings but also resulted in higher humidity.

I absolutely want my 2 speed unit!   I like the longer runtimes and I think it saves me money too. 

I keep meaning to see if the sensual to total heat load ratio is the same for high and low speed operation. I also suspect that the unit is not cooling the air as much on low speed as high speed thus it does not remove as much moisture.

Geonovice: Seems like you might could tee off the existing line and install a back flow preventer and then a pump to the geo unit. If you go with an open flow unit, get a Cu/Ni heat exchanger as they are far more resistance to corrosion. And since you don't have a two story home it might not make much difference getting a single vice double unit. I would like to have your set up so I could cool my bedroom and extra 2 degrees for the night!

You are going to have to check the line before the pump. You can't tell by working on the sprinkler system as the pump would block the flow. Or you could just call a local well driller (that's what I would do) and ask him. Lots easier in my opinion.

You need a second well to return the water to the aquifer - you can't pump it out of a well and back into it at the same time without concentric tubing or double pipes - which you don't have. And if you could it would destroy the energy efficiency as the warm water would flow right back to the unit.

Sensual heat...is someone's Freudian slip showing? (Sorry -Ii just can't resist such opportunities)

I've wondered if SCW could be applied to a deep Floridan Aquifer well, that is reinject to a different height within the same well, but it likely wouldn't work nearly as well as a 2nd, distant reinjection well.

look for a hose bib on well BEFORE the pump. They are often installed on artesian wells in North FL and quickly answer the question of artesian flow / pressure.

I've been letting the geo vs. conventional a/c thoughts sit on the back burner for now. It seems that my time & money might be better spent on reducing the heat load in my home before I consider replacing my current a/c equipment. Thank you all for your input. I will start a new thread in the section on insulation, as I have many questions on that subject.

You are a smart man . Good luck

Best watts are 'Negawatts' - those gained by NOT using power in the first place.

Definitely pluck the low-hanging conservation fruit. Then run a revised load calculation before replacing HVAC

Split systems can have all components inside.

RE payback, if you compare the price of 18 seer equipment (and the $1,500 cap on their tax credit), you might find that geo payback is good. Leave it to the bidders to convince you one way or the other.

Good luck,
Joe

We're doing splits on the next job so as to keep all the geo water in the garage and have one air handler on the third floor. House is on beach, so salt air avoidance is a major driver for choosing geo

Here's some rambling thoughts on reducing the heat load. Let me know what you think. I have done a number of improvements to the house since I moved in, in 1995. For example, having the a/c ducts sealed up (Tampa Electrric), having 3M tinted window film installed, insulating the garage doors, adding insulation above the garage, the shrubs and trees provide more shade now! heavier draperies on southern facing windows, a large awning that keeps the sun off of the 16' glass door, lanai curtains, use of more CFL's, putting the cat door through the wall vs. the sliding door insert style cat door. Maybe I've reduced the heat load by 1/2 a ton or more already. I can only assume when the house was built the builder "did the math" and it came out at 5 tons. But, what is the heat load now, & what is a realistic level that I could achieve by improving the ceiling insulation from the current R-30, and sealing up the air leaks around the numerous recessed ceiling lights & wall switches/plugs? Trying to create a cool attic area for the a/c ducts, on burying them in insulation might be a real expensive improvement. What about doubling up some of the ducts (a 6" inside an 8" or an 8" inside a 10"). Does this make any sense??? Maybe just on the returns? If this makes any sense what R value improvement, if an, might be attained. What other attic improvements might I consider to keep the ducts cooler?

A pricey though effective attic improvement is to seal it up with sprayfoam - bring the attic and all its ductwork into the conditioned envelope. Then duct insulation and leaks become comparatively minor issues.

Keeping solar gain out of the house entirely via an awning is much better than trying to block it once it passes through the window glass (shades or curtains)

Don't be too confident builder 'did the math'. Many, if not most systems here in FL are both oversized and underducted, a miserable combination hard on both electric bills and comfort.

There is way too much area too try to enclose in my attic. There is an area big enough to make a full 8" high 22' X 7' room but none of the duct work is in this area. In addition, there are other areas big enough to walk through. I would have to enclose an offset "U" shaped area approximately 40' X 65" to get all the ducts enclosed. How much larger does an a/c system have to be to cool this additional space?