*
I am looking for peoples input with the use of Geothermal HVAC on a residential project… Want to use closed loop ground source system for whole house heating and cooling. The house will have traditional duct work system (no radient or other technology). Any concerns about “drafty houses” like the units of old…. Will I just be buying an expensive electric or gas unit that will use the “backup” all of the time?????
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
The "She Build" initiative is empowering women in Seattle, WA by ensuring they have safe, healthy homes.
Featured Video
Video: Build a Fireplace, Brick by BrickHighlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
*
How timely!
I just came here to ask for input on closed loop ground water systems for cooling. My understanding is that many of the major air conditioning manufacturers once offered residential systems in which ground water was used to cool the condenser unit. I am told that at least one of the majors, carrier or trane, maybe, still offers commercial units starting at 7 tons. I'm interested in a four ton equivalent.
Any info will be appreciated.
*Trane makes water to air heat pumps down to one ton. I am currently using a 2 ton unit. It is nice to not have a noisy outside unit to clean. I also divert the loop water to my pool for free heat while I am air conditioning. I can also use the unit for space heat but due to the high cost of electricity here I use oil for my primary heat. Comfort of a heatpump installation depends upon proper duct work.
*John et al,Two years ago my boss and I helped install 2 Waterfurnace GHP's in an 8000+ sq. ft. home. I cannot speak highly enough of the quality and success we have had with these units and strongly encourage you to use GHp's. His heating / cooling bill is roughly $100/ month (remember the footage?) We run the blowers at idle full time and this is the most comfortable house I've ever been in. My office desk is literally 3 feet from the 4 ton unit, behind a closet door, and my fridge at home annoys me more than this unit. I would put one in a bedroom closet. In retrospect, we wish we had used the desuperheater option to heat water for free all summer with the rejected heat. Also, we might well have done closed loops in wells rather than the horizontal trenches. In SE Ohio clay, we finally had to go to a trackhoe to step the trench walls due to collapses. But given the electric savings, even this expense will have been worth it. Just make sure you understand the excavation required to do 5-6' trenches. It will settle over time and likely require at least one re-filling and leveling if it's in yard space. Personally, I am convinced that the GHP companies are doing themselves a disservice by not pushing the closed-loop wells (bore holes, really, as no water is used...)Hope this puts you over the edge.Aaron
*Aaron,I am located in SE Ohio. I do nothing but radiant floor heat. I have always considered GEO as a perfect match to my low temperature hydronic distribution systems. For various reasons, I have not been able to "hookup" with a local GEO firm (they dabble in RFH and may see me as a competitor?) so I don't have anything other than hearsay to go on. The complaints I have heard from the many folks who have used GEO concerns the first year or two of operation. They were totally dissatisfied with the performance. Could the "excavation/settling" problem you speak of be contributing to the initial ground to loop heat transfer efficiency? I would presume if there was settling after the first year or so that may be the problem.......incomplete conductive surface?
*Thanks all for the advice - I think that the GEO system (with vertical bores) is the way to gooooooo....
*Ron:Care to expand on your statement "Comfort of a heatpump installation depends upon proper duct work."?Thanks
*jj,I have a hard time believing settling could affect conductive heat transfer, even in SE Ohio's finest clays.... Our systems worked perfectly from the get go, and I have never heard that complaint myself. Could it be due to users' unfamiliarity with system, perhaps unwittingly turning on Electric backup when not needed? The only real complaint I have heard lately was a system that gathered all the lines into the manifold inside the basement, rather than in a pit outside. This, combined with what was described as a normal deep well loop circulation pump, lead to noise in the basement. On the plus side, having the manifold in the basement allows shutting down one loop in the extremely unlikely event of a leak. I would still put it outside, though, and have a silent system, which is what the Waterfurnace pumps are.Aaron
*Matt,Since any heat pump will not have as high of a discharge temp. as a gas or oil furnace, the placement of the registers and the speed of the airflow thru them is more important. There is more airflow also so ductwork sized for gas would probably be undersized or not enough registers for a heatpump.Ron
*I'll put in my two cents. First, there are a ton of web sites on this subject. Try the International Ground Source Heat Pump Association. Web site is run out of Oklahoma State University at http://www.igshpa.okstate.edu. Gives you a lot of x-references to manufacturers, installers, etc. Many electric utilities have a division that can give you more info. Many of them are pushing ground source. Some offer rebates for homes with geothermal systems. Here in Maryland, there is a lot of discussion on using ground-source systems in our schools due to often tremendous energy savings. All new schools under design are required to do a life-cycle analysis with geothermal as one of the options to be analysed. I am looking into it for my new home to be built next year. Final decision has not been made, but it looks like substantial energy savings can be gained, but I don't think I can afford the additional up-front capital cost (these systems definately more expensive up-front). Lastly, they perform well only IF well-designed and installed (what else is new?). Find someone who has done many and check references. GOOD LUCK.
*John,I am in the process of building a 2,100 sq ft house with an earth coupled heat pump (think geothermal is a term that is more suitable to heating from a hot spring). The unit we are getting is rated at 4 tons. Last week we put in 2,000 feet of loop in 750 feet of trench. I don't have any operational experience to share but there are a number of these systems here (NE Ark) and all of the owners we talke to are enthusiastic.My vendor is Hydro-Tech Corporation of Pocahontas, AR. They have an informative web site [http://www.hydro-temp.com/]. They manufacture their own systems. They install locally and through dealers nation wide. Steve Hansen
*Gentlemen ... geothermal heating and cooling may have its appeal and I can understand that, but tell us the truth about the capital and installation costs. Then tell us how many years it takes to pay back.
*PS Don't forget to tell us the electricty bills.
*I have seen the cost of installing a loop for a 2 ton unit range from $250 to over $5000. It's hard to guess the pay back time with that range. If you have a pond near the house its a no brainer. Just tie some cement blocks to the pipe bundle and throw it in.
*Tedd,My installation costs (above and beyond duct work and actual equipment costs) will be about $6.00 / foot for closed loop vertical bores. At 150' of bore per ton, 3 tons for the house, that comes to $2700.00. Projected electric bill about $25-30 a month. You do the math on the payoff period. Well under ten years.Aaron
*This is an interesting thread. I have a boiler with radiant floor heat (including the garage). We're still heavily in the gut and renovate stage, but eventually we plan to add a full basement addition and a burried water cystern to collect rain water. I've been toying with the idea of laying a swack (much as I can reasonably afford) of heating pex under the cystern. Not to heat, but to cool in summer. I would plumb the loop on valves which would be used to bring the loop into the system in summer (isolate the boiler and DHW) and take it out in winter (let it cool down). If I insulate heavily, I suspect that between the ground sink, and the garage floor mass (4 car which will be kept just above zero all winter) I can circulate the cooler temperatures through the house floors and keep things reasonably comfortable through the summer without resorting to air conditioning (Heat recovery ventilators would be involved here). Not exactly geothermal HVAC (not heat pumps, no air conditioners), but more of a free summer cooling source. Any comments?BTW- summers are short, winters are long. Some years, AC only amounts to a luxury for 1 or 2 weeks out of the year.
*Scott,According to sources in the RFH/RFC cooling industry, radiant floor cooling can be expected to catch about 20% of your cooling needs. Radiant cooled ceilings provide a much greater effect.Of course then you have to take into consideration the humidity level, solar gain of the radiantly cooled surfaces, floor coverings, the ability to adjust your circulated around the dewpoint, etc.I have experimented on a small scale with floor cooling in agricultural pole buildings using pond water and heat exchanger arrangements. The simplicity of this type of application is great for cooling livestock but as we speak, I have not found a control that will modulate the temperature of the circulating water to adjust for the dewpoint during humid periods.Another factor you have to consider when using radiant cooling via the same tube as radiant floor heat is the amount and on center spacing of the tube in the concrete. I have some nomographs (somewhere in this mess) that plot the effectiveness based upon tube spacing and GPM.I also have a small project of my own in the works that will couple closely spaced 4-6" radiant ceiling tube with a desiccant type of dehumidification system using the natural gas boiler for drying the desiccant. Again, I don't expect anything wildly successful until an appropriate automatic control based on dewpoint is available for small scope systems. But at least I will have everything in place to utilize a control when it is offered.Doesn't really do much good to run water thru your home or shop if all you are creating is a semi-tropical rain forest.Jeff
*Thanks for info Jeff.I expect a air to air heat exchanger and (maybe?) dehumidifier in the air stream would deal with the humidity. Climate in these parts are temperate. Summers tend to be short, hot and dry. To be sure the humidity goes up, but it's not the "get out your bathing suit and swim for it" kind of stickiness I've experienced else where. Besides, I keep a large number of aquariums. Indoor humidity is always problem, regardless of the conditions outside.My boiler distributor and HVAC guide thought cooling radiant spaces would cause no end of trouble with condensation until I explained that I only wanted to create a temperature differenctial of 1 or 2 degrees, not pump super chilled AC powered cooling. Then he thought it might have merit, particularily if the house is well insulated. It shouldn't be that difficult to control the mixer to do just that, knock the circulating fluid down to just a degree or two below room temp.I know ceiling panels would be more efficient for cooling, but I wonder if a cold floor under foot in summer can create the same experience as a warm floor in winter?
*.....Scott..it doesn't take long to transfer all of the btus out of your cistern to the point where there is no transfer left...unless your cistern is a lot bigger than I'm envisioning...One thing I note is that the Geothermal heat pump mfrs don't have a long business history..they are thin on customers.. and the ones with deep pockets have heartless accountants for decsion makers..my point is will they be there to service you in 5 years? Geothermal heat pumps are relatively high tech...
*Hope your house is loose because 4 tons is to much.
*Ron I have seen you give some good advice before, and since you mentioned ponds, I'll ask you. Anyone else feel free to answer.I was looking at a water sourcing heatpump that would use a good sized pond as it's source. A glycol loop would run to a coil weighted to the bottom of the pond. The pond would be about ten feet deep. I cannot get concrete answers on this, but some people tell me the pond would eventually heat up to where I could not cool the house. The house only needs 4 ton of heat, I think it needed 2 tons of cooling.I am not so worried about heating up the pond due to the downspouts and foundation drains tiled to it (well downhill), and we are going to run a 6" pipe from an uphill crek to it also to insure no stagnation.I was also wondering about heating in the winter. I found a company that makes an apparently real nice water sourcing setup, but they are in texas and never put one under a pond in upstate NY. The guy I spoke to says I cannot freeze the pond solid (for density reasons) but he also says I can't supercool or subcool it due to constant heat gain from the earth at the bottom of the pond. Ever put one in a pond for heating?I am looking for real numbers or installations.-Rob
*There was a good article, don't remember where, on radiant cooling. The author mentioned radiant coolers used ina soffit structure along exterior walls.The author found radiant floor cooling most effective in eliminating heat buildup due to solar gain. Like under tile floors in a south facing glass atrium or vestibule, and other "spot" cooling needs to stop heat buildup at it's source. If this heat wasn't taken up by the cooling loop it would otherwise be emitted as ifra-red and buildup in the space, especially due to Low-E coatings on the glass.-Rob
*These posts prove that construction is regional. Here in Dallas we pay about $ 900.00 per ton for AC with a gas fired forced hot air furnace. (new construction) We have priced geothermal. The cost here is about $ 3000.00 per ton. With a 5 ton unit it would take about 10 years to recover costs. The only problem I have with that is that the effective life of the system would be about 12 to 15 years. I just don't think the over all return on investment is high enough to justify these systems.
*I am in the process of getting bids for installation of radiant floor heating for my 150 year old farmhouse with hardwood flooring throughout. This will be a typical between the floor joist installation. My problem is that each contractor's specifications are different. Some say you must have the metal snap on plates for the system to work. Others say that they never use the plates because it creates" hot spots". They staple the tubing so that it hangs below the flooring and never actually touches the floor. Still others staple the tubing to the floor and than cover it with a reflective foil.I need to make a choice but am finding it very confusing. Which system is better, or are they comprable? Are there factors other than cost that I should be aware of?
*harry.. u big lug...repost yur question... or get outta town...ask jeff...he knows radiant....
*Thank You very much Mike.After going on 3 years of being involved with Breaktime either as a listener or pro-activist promoting RFH in one form or another, your vote of confidence in my expertise feels as good as a damned healthy 'raise' or a Gold Watch at retirement. Man!! How I wish I was able to watch this/these threads, contribute freely and without abandon. 't ain't so as we speak. Hopefully, career/education and family obligations will temper themselves shortly so I can free up some time to "show off" with what I love most, RFH.In the meantime, I am busting ass to free the weekend for PeteFest.Thanks Mike Smith. I never made a dime off you but I have never experienced such appreciation and gratitude from any contractor as I have from you. Mike and his wife have unselfishly offered me a home away from home whenever I was in their end of the country. Someday Mike, will take yous'e guys/gal up on the offer. I am humbled.Why did I write this? Because I can. Who cares?I do.Sincerely,Jeffie
*aw shucks, jeff , ya got me blushin now...blodgett... ya got a shirt fer jeff ?
*I was looking at this month's FHB. Neat article on Geothermal. Looks pretty expensive though digging those World War I looking trenches in the yard. A thought occured to me-other then probably being some horrendous code violation, why couldn't you just lay those pipes in the trenches for the septic system?You could dig the septic trenches a little deeper then usual.There has got to be some heat generated by all that sewage fermenting as well.Well I know it sounds crazy, but I had to ask. Flame away . . .
*Can't believe I just posted the same question as a new post....Let's see what comes up.
*
I am looking for peoples input with the use of Geothermal HVAC on a residential project... Want to use closed loop ground source system for whole house heating and cooling. The house will have traditional duct work system (no radient or other technology). Any concerns about "drafty houses" like the units of old.... Will I just be buying an expensive electric or gas unit that will use the "backup" all of the time?????