So, I've been thinking about an idea I had posted a similar, but completely different idea in another thread quite some time ago, but I can't find it. The new idea is pretty much for a closed loop air source heat pump. We all know that air source heat pumps don't work that well with air that is below 30 degrees F. Auxiliary heat is needed. We all know that a closed loop geothermal heat source works by using an antifreeze solution to act as the heat transfer medium and then goes through a water to air heat ex-changer (for those with forced air heating) We also know that the ground loop water temperature should be above 50 degrees F. So, by using air as your heat transfer medium, I think one could save some money compared to conventional ground source heat pumps. Air to air heat exchangers are less expensive than water to air. Also, you wouldn't have to pay for the anti freeze. And because the specific temperature of air is so much less than that of anti freeze, it wouldn't take as long of pipe runs to get to the same temperature. During the winter, the air heats up quicker, during the summer, the air cools down quicker. With a closed source ground loop filled with air, you've made yourself a year round heat source/heat sink for an air source heat pump that won't leak water (even though the 50 yr warranty on field tile is not shabby at all) and eliminate the need for aux heating. What do you think? Possible idea, or crack pot idea?

While typing this, I thought of another crazy idea: just run the tube for the compressing fluid in the ground. In the winter, the ground warms up the compressing fluid and in the summer the ground cools down the compressing fluid. Of course, I don't think Copper would be good use with constant contact in soil, but perhaps stainless steel or aluminum or some other material that I can't think of at the moment.

Posted By Cgallaway on 25 Feb 2013 08:59 PM
While typing this, I thought of another crazy idea: just run the tube for the compressing fluid in the ground. In the winter, the ground warms up the compressing fluid and in the summer the ground cools down the compressing fluid. Of course, I don't think Copper would be good use with constant contact in soil, but perhaps stainless steel or aluminum or some other material that I can't think of at the moment.

These type of systems have been in use for 20 years or so.  They come with their own set of problems and are not widely used.  Google DX heat pumps.

Posted By Cgallaway on 25 Feb 2013 08:55 PM

We all know that a closed loop geothermal heat source works by using an antifreeze solution to
act as the heat transfer medium and then goes through a water to air heat ex-changer...

I didn't know that.

We also know that the ground loop water temperature should be above 50 degrees F.

I didn't know that.

Air to air heat exchangers are less expensive than water to air.

I didn't know that.

And because the specific temperature of air is so much less than that of anti freeze,
it wouldn't take as long of pipe runs to get to the same temperature.

a) What is "specific temperature?"

b) Why are they called "heat pumps" -- rather than "temperature pumps?"

CG - I suggest college level courses in thermodynamics, fluid dynamics and heat transfer, followed by certification in HVAC, water source heat pumps, and geothermal loops.

After you have that coursework and certs under your belt, feel free to return to us with your "ideas" for reforming our industry.

I looked up the DX heat pumps, but they still seemed to be talking about using a liquid/water in ground loops.

CG, are you talking about just burying tubing (diam? 3", 6" or larger)in the ground, and then using an air to air heat pump to get heat/cold out of it? I think I have seen stuff about earth air tubes of various types that sound great in practice but present problems with moisture control and mold growth. Is this what you are thinking? http://www.greengaragedetroit.com/index.php?title=Earth_tubes

http://www.builditsolar.com/Projects/Cooling/EarthtubeNotes.htm

-Rosalinda

Earth tubes and direct exchange systems (DX) are what you have described. Both have been around for decades and yet water source heat pump sales have exploded.

All, I'm not suggesting this idea is worth doing, nor am I suggesting it's somehow better than what's on the market. Fact is, its an idea, one that may have been thought of before, but perhaps I don't have the right words to google to get a decent result. Geodean, thanks for giving me something to look up. Rosalinda, Thanks to you as well. Apparently, Earth tubes is what I was describing. The difference possibly being where the outside air would go through the outside wall, into the house, and into perhaps an erv or hrv or some other type of humidifying/dehumidifying device to deal with the moisture issue. A filter, of course would take care of the particulates.

Joe.Ami, thanks for also giving me the proper words to describe what I was thinking in order to do more research. Looby, sorry my terminology may not have been correct, and perhaps my "facts" aren't exactly solid. I've read up on the stuff a bit, and am no expert, so perhaps I am wrong. So glad you could contribute constructively to the conversation///Ends Sarcasm.

Engineer, Curt Dierden, thanks for reinforcing the bad stereotype of the contractor. That stuck up, egotistical attitude is precisely why I try to learn about stuff so I can do it myself and avoid people like you. Concerning I wasn't the first person to think of the idea, and it apparently is in practice, I would say that I wasn't trying to "reform" your industry. Of course, I suppose many years ago, some other HVAC engineer or contractor might have said the same thing about the ideas your company espouses. Certainly about just about any "Green" idea. Simple ideas like putting the HVAC inside the thermal envelope of the house at one time was a radical idea and every installer knew it was a bad idea. Today, depending on who you talk to, having an unvented attic is either good or bad. Of course, the older generation are the ones who say it's bad. Who needs more than R-13 in their walls? Certainly not the contractors of 1970. Having your heat registers in the middle of the house instead of under the windows was once a very boneheaded move. And don't get me started on the number of contractors who refuse to do a manual J because they "know better". In fact, it was your predecessors in the industry (other "Professionals") who oversized hvac equipment based on rules of thumbs and square footage instead of thinking about what that specific house needed.

So Curt, I'm on here, looking for information,I have a few ideas that I don't know if they are good or not, much less why. So, I look for answers. Knowing I am not an expert in HVAC, I go to people who know a lot more than I do on the subject for reasoned analysis. I wasn't looking some jerk to express how stupid I am and how I shouldn't try to "reform [y]our industry". Of course, I should now point out how hypocritical it is of you to not want your industry reformed, but don't mind other people's industries to be reformed. Window manufacturers, roofing contractors, plumbers, typical home builders and yes, even electricians and the electric industry (by advocacy for solar energy or wind energy to produce electricity). I would have been OK with you had you just not responded, which you could have done. But instead, you wanted to show your ass to me, for whatever reason. Sorry if I offended you with my original post, I wasn't meaning to.

NEWS FLASH!

Hordes of straw men slaughtered by anti-thermodynamic insurgent...

...film at 11:00,

Looby

We do stumble on the same "new" ideas here every few months. Most times we are not sarcastic, but I have caught myself congratulating people for inventing the single stage heat pump when asked "if first stage is so efficient why not oversize a 2 stage unit so it never has to use 2nd stage.......?"
Many of the ideas are of "momentum engine ilk" or already on the scrap heap, but occasionally one will strike our fancy and get many thoughtful responses- and occasionally one will be a "been there done that" that draws a snippier reply.
One way around it is a forum and google search that many skip before trying on their new ideas.
Glad we gave you the keywords.
Now the end result of both systems is to have sporadic success. DX is not without warts but more likely to satisfy a heating requirement than earth tubes. Earth tubes lack the ability to amplify the heat that heat pumps have and further dehumidification with a HRV will reduce (or even negate) the modest amount of heat collected.
I have a friend and fellow blogger that has installed some in his new green house and suggests he might get limited use in bumper seasons. We hope to hook it in as the first stage of the heating system with a relatively high outdoor lock out temp.
Without being able to amplify heat collected you would have to have a huge foot print of earth tubes to get the job done (we're talking miles) for a relatively modest amount of conditioned space.
Good Luck,
joe

It's always important to do at least the crayon-on napkin or lipstick on mirror math on any of it before running it up the flagpole.

The apparent brightness of flashes of epiphany are usually illusory, and cannot overcome the laws of physics, and usually the first-order simple model math will tell you've take a flight of fancy.

I'm not an HVAC pro or a building contractor, but I DO have a physics degree, only rarely do I need to dig into the hard-math version to reach a conclusion about most things HVAC- a crayon and a grasp of the fundamentals can get you to 95% certainty, and the 5% hardly matters. (But I LOVE it when the simple model gets it wrong, since there's a nugget of insight there when it does!)

My crayon sez:

In terms of heat capacity per unit volume, water is about 3300 times better than air.
So, a typical 3 GPM per ton loop water flow translates to 10,000 GPM/ton air flow.

For a 3-ton unit, that works out to about 4000 CFM of air through the loop field...

...plus one kick-a$$ flow center!

Looby

Thanks all...I wasn't expecting to heat a house with this, but instead, for a tight house (that I one day hope to make this 1915 special), be able to get the fresh air needed, in the middle of winter (-20 degree F sometimes before windchill) with only using minimum energy to heat the outside air from that -20 degree F to the 120 degree F that is common at the heat register. I will be doing more research on it, as I don't really have much of a timetable (I want to get rid of the old knob and tube electricity and get the new stuff in conduit, then new windows, then see if I need to fill the stucco walls all before I get the new geothermal/earth tubes/erv/or whatever else to replace the electric furnace in the attic and the natural gas furnace in the basement).

Hmm... 3 gpm/ton water versus TEN THOUSAND gpm/ton air?

Engineer recommended college level courses in thermodynamics;
but first, I'd suggest a remedial course in LITTLE versus BIG.

Yes, Looby, I get it, but I am not a fish, nor do I have gills. Water filled pipes are great for heat, but not so good when wanting to supply fresh air. well, I guess I found what I was looking for....http://www.amvicsystem.com/Ecoair

Yes, the makers of ICF blocks also make this. From what they say, it's not for supplying the home with heat, but instead to precondition the incoming fresh air so the actual furnace (geothermal, natural gas, electric, etc) doesn't have to use as much energy to raise the temperature of the air. Still a lot of research to do on it, but when I find someone selling it with a recognizable name and reputation like amvicsystems, I have to think it is worth investigating.

It's far cheaper to move heat in water than with air.

120F is an excessive register output temp for heating a space to 70F. It's a common output temp for fossil-fired heating systems though (and even some mini-splits), but bad for efficiency on heat pump systems. That efficiency hit is why many GSHP air-distribution systems run at fairly tepid temperatures well below human body temperature. But radiant floors & ceilings can function just fine with pumped water at similar temps, with lower power in the pumping than in air handlers, and without the wind-chill discomfort of a tepid-air distribution systems that make register-placement critical for true comfort (which IS achievable, if care is taken in the duct design.)

You have to be VERY careful in your hygro-thermal analysis when insulating behind stucco, since that leaves susceptible wood behind the stucco at lower temps, potentially increasing moisture loading in winter, and slowing the shoulder season drying. Is this a plank-sheathed studwall with some sort of tar-paper on the exterior of the sheathing, with at least a 1/2" gap between the sheathing and stucco (I hope)? If yes, there' a chance this can be done, but if it's stucco on lath applied directly to the studs you're better off insulating on the exterior with enough foam to keep the average mid-winter temp at the lath above 40F with whatever R you put in for cavity fill, and putting up new siding, which is not a cheap option. With a wall-stackup and an exact location (postal code, city, whatever for climate data) we'd be able to narrow in on an approach that won't cause the house to rot out from beneath you.

Dana, Thanks for the info. I am unsure about the stucco wall build as it is now....I haven't actually opened it up, except for taking out a light switch. There appears to be some steel wool with paper backing in the outside walls, towards the outside. It appears the sunrooms (double decker porch that was later inclosed) was closed in the 1930's...at least that would be the time frame the vintage of the wiring. The outside stucco of the sunrooms match the rest of the house, which was built in 1915, so I doubt any sheathing exists. I have read about insulating the walls in the old homes causing rotting problems, so I was going to take a wait and see approach. If sealing the inside seams and holes and getting new windows makes the place comfortable enough, then there really is no need to fill the walls. However, to get a good grasp on everything, I've been looking at both retrofoam (possible shrinkage issues) and high density cellulose (could possibly pop the wood lath from the nails). There is no doubt that nothing I do will pay itself back...I am lucky to live in an area with low gas rates, so comfort is more of an issue. I do have an electric furnace in the attic, and that has been taking $200 a month to heat this year (moved in back in June...and apparently the 15 kW furnace had 2-5KW elements unplugged, so I still have another month before I get a full bill since the furnace was fixed). Also concerning the stucco; there is a line in between the main and second floors where the stucco has bowed a little, I expect from the house settling over the course of the past 95 plus years. It's fixable and won't require removing stucco, which means I won't be replacing the stucco with siding. That said, perhaps 20 yrs down the road, I might want to replace the stucco, and perhaps that will be the time to get the vapor barrier installed.

About the register temperature...Yeah, I understand the gas furnace output is more than other types of heating in terms of temperature. I do like radiant heating systems, but I won't install one, on account of 2 reasons. Most importantly, I get worried about something breaking and water leaking everywhere. As it is, the house was designed very well, where the hot water heater in the basement is directly below the kitchen sink on the main floor and the bathroom on the second floor. The only other water runs are in the basement, which is concrete floor and brick walls. If this were a newer built house, I wouldn't worry about it so much, but the possibly of ruining the maybe original (I don't know if they are vintage 1930's or 1915), hardwood floor makes me shy away from it. So, forced air is my choosing...and 90 degree air blowing around feels a lot cooler. Which is why I expect the 110-120 degree temp at the register. At least for now.

I am in the very beginning of design stages on this, and I still have a few years before it becomes reality, but I am trying to look stuff up, get it straight in my head, understand it, before the "moment of truth" is upon me. I don't have a whole lot of contractor options in this area, so I want to ensure that I know exactly what I want or need and exactly how to do it before I sign anyone up. I don't want to end up on "Holmes" or any other of those shows.

I'm perfectly content to be "avoided" by such a Johnny-come-lately.

I routinely spend an average of at least 8-12 hours per week refining my own knowledge and understanding of HVAC, building science, and energy conservation, so the idea that I, or for that matter most of the rest of the veteran members here, are against new ideas or practices is both ludicrous, and, quite frankly, highly offensive.

That said, meanwhile, feel free to continue reforming your knowledge and understanding of these subjects with decades-old, new-to-you ideas. We'll kick back and enjoy the show!

120F register air will make geo very inefficient, so expectations are not in line with an efficient geo system. You should follow your notions and go with a good old natural gas system!

engineer: Thanks for that. For me, sometimes, the issue isn't always if the idea has been around a long time, but sometimes the technology has come a long way since the idea was last looked into. Battery powered cars are a good example. Some of the first cars were battery powered. And now, we as a society are starting to push it again. But the technology is completely different, even if the bigger picture is the same. In this particular case, I had an idea that apparently had been around for a while. As evidenced by my first few posts here, I didn't even have a decent phrase that I could Google to find out more. I do spend some time trying to inform myself, but HVAC is not my career, and life simply gets in the way of other interests. Raising a family and trying to research all aspects of making the home energy efficient in addition to trying to better myself in my own career does require some prioritization. So, thanks for the parting thoughts. Sorry I got so riled up so quickly.

DocJenser: The natural gas is the measuring stick at this point, thanks for your input.