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Geothermal - well question

Posted by mees135 (My Page) on
Wed, Jul 30, 08 at 17:08

Hi! Totally new to this whole geothermal heat pump way of heating/cooling, but sounds fantastic. I was wondering - we have an old unused well from the 1800's on our 3.5 acre lot - can they use this well (and maybe minimal drilling) to install one of the loops? Water table is high - just a couple feet and you hit water (we're just south of Lake Erie a few miles).

Also, we have no duct work in this old house (early 1900's) - its 2 story, about 2,00 sq ft. Is it possible to install tiny tubes to carry heat/cool to the second floor and put them in the walls, or do we need to add duct work? (i love our old plaster walls, and would love to avoid having to disrupt too much of the architecture).

Thanks for any advice / input!


Follow-Up Postings:

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RE: Geothermal - well question

Hi Mees.

I won't presume to be qualified to give you advice, but my input would be that you might very well be able to make this work.

Geothermal heat pumps work very well- but there are a lot of ways to drive the upfront costs to the point that it takes forever to enjoy the payback. For example, I installed an open loop system (works great) but because I am lifting water about 60 feet to provide the geoexchange I am spending a large part of my savings on electricity to pump water! A closed loop system with vertical bore holes probably would have been completely beyond our means, and a system that used trenches would have been impossible on our lot.

You might be in a better position. It would definitely be worth the investment to find out.

I can't answer the second part of your question- although I suspect that the tiny tubes alternative is a no-go, if by tiny you mean 1/4" or thereabouts. But If by tiny you mean 1", well, that might be a whole 'nother story. There's a lot of space behind the plaster in my 100 year old house, and I suspect there is in yours, too. We've kept our plaster pretty much original too- we do love it.

Good luck,

Mark


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RE: Geothermal - well question

Mark -

Thanks! Don't mind the 1" holes - that wouldn't be too big. Lots of space behind the plaster, some cellulose insulation, but shouldn't be a problem. Now i'm looking forward to seeing if the well is deep enough for this project!


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RE: Geothermal - well question

Keep in touch Mees- there are other people on this forum much better qualified than I to offer suggestions. And the more information you can find time to help them the more they can help.

I hope this works out for you.

Best wishes,

M


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RE: Geothermal - well question

First of all youre looking at a very expensive installation with a big outlay of money up front because you want geothermal, which is always very expensive in its own right and because you have no existing distribution system suitable for geothermal. Its still worth doing due to the direction energy costs are going in, for comfort, and for resale value, not to mention the environment. Its also the best solution to preserve the visual integrity of a heritage home, such as yours may be, as no visible mechanical systems are installed, anywhere, outside.

Regarding your distribution system, yes its possible to install tiny tubes instead of conventional forced air ducts or even the smaller high velocity (HV) ducts for that matter too. The system you would be looking at is a liquid system with low temperature fan coil units. The beauty of this system is the relative ease in which it may be installed AND unlike the hydronic system you probably now have, this is a hydronic system fully capable of reversing during the summer such that the geothermal unit will create and distribute chilled water to these hydronic fan coil units and you will have central air-conditioning as well. It is also very easy to add individually temperature control for each area where a hydronic fan coil unit is installed.

As for the geothermal component, your best choice for high efficiency and low maintenance would be with a closed loop system. However, this installation choice may be complicated by the high water table which may make excavating trenches for a conventional liquid to water system difficult. I would recommend the possible use of a DX geothermal installation, as trenching would be minimal. Drilling could be done in a radial pattern, 30 off axis, such that at the surface, your borefield resembles the apex of a pyramid, taking up very little ground surface area. DX also has the added advantage of better being able to make use of the high water table (particularly if this water is moving!). The phase change of the refrigerant from liquid to gas (and vice-versa) takes place directly in the ground (DX=Direct Exchange), as opposed to inside a secondary heat exchanger (which does not exist in a DX GSHP) inside the HP in a conventional GSHP. So the effect of the water table on the copper ground loops and refrigerant in a DX system is not only immediate in the DX system but also virtually exponential as compared to a conventional plastic HDPE ground loop circulating a liquid (water & antifreeze). This is basically also why DX ground loops can be much shorter than conventional liquid ground loops; that and copper being a better conductor than plastic.

Thats the short answer to your questions (from my point of view). This type of installation requires marrying two separate, highly specialized technologies. Its only simple when its done (designed & installed) right. Do your homework carefully hire the right professionals!

SR


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RE: Geothermal - well question

Mees- I couldn't agree more with what SR says -never mind that he's a pro and I'm just a homeowner!- what he's saying is well informed, especially about hiring the right professionals.

I know nothing about DX systems, which I take to be SW's system of choice where applicable, and only a limited amount about closed loop and open loop geothermal systems, so please take everything I say with a grain of salt.

Still, it occurs to me that with your water table as high as it is you might in fact be a good candidate for an open loop, since trenching would be "challenging". i'd appreciate hearing SR & others views on that. I'm thinking in terms of quite a shallow well (say, 20 feet) for the supply side. But, I can only guess what nightmare you might run into on the discharge side!

Again, good luck and stay in touch.

M


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RE: Geothermal - well question

Re: Mark

Open loop does have its challenges. Water resources should be used responsibly. Water should either be discharged from where it came from or be able to find its way back there. If the well is too deep and the required GPM too large (could require over 20,000 gal/day), pumping power will reduce the over all system efficiency. Then there is the question of long-term water availability as well as quality. WSHP will require more maintenance, particularly if the water quality is poor.

Open loop WSHPs become interesting when the demand for A/C is high and the EWT is low enough to permit passive cooling. Some WSHPs have an EER as high as 118 (not a typo!). That means a WSHP (excluding well pump), open loop, passive cooling, can cool a large home using about 1/3 the energy of a handheld blow-dryer!

SR


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RE: Geothermal - well question

WOW! Thanks for all the info - i have soooo much still to look into!

Actually, right now we have electric baseboard heat (expensive!!!)- the house, believe it or not, does not have a fireplace. there is an old chimney, but its capped off in the attic from an old coal furnace in the cellar.

So, maybe we can do the geothermal and do the first floor this year with either air ducts (the floor has places where the register used to be) or radiant heat, and next year do the second floor.... trying to look at cost and what we can do feasibly each year!

thanks for all the input . . . we've got folks coming out next week, i'll post what they suggest for others to see!


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RE: Geothermal - well question

Hi SR, and thanks for sharing your knowledge. We're particularly lucky in many ways here in that we can readily discharge our water into an old, rock-filled cesspool and have it istantly drain just thirty feet from our intake well (and lest anybody wince at the image, the cesspool was abandoned over fifty years ago.) And, we were able to avoid excessive trenching because we located the old tile drain to that cesspool and used it as a sleeve to slide the discharge line into. And, we sit about sixty feet above an underground river that is said to move fast enough to replace all the water in the acquifer daily -although I have no idea how they can say that with authority.

The efficiency of these systems, designed and operated correctly, can indeed be wonderful, but the devil is in the details. So I hope Mees and others will take care to be well informed and to have complete confidence in their sources before they commit.

As for the amount of water used: our little three ton system runs a large part of the day during the worst of the winter weather. If it did run all 24 hours it would take about 13,000 gallons. At roughly eight pounds to the gallon that's a lot of lifting for that little 1/2 horse pump! I am not trained in engineering but I suspect that there might be efficiencies to be gained if the water moved through the system less quickly and more BTU's were recovered from it before discharge. I suspect that a system specifically designed for open loop might benefit that way, and I also suspect that "most" technologies (I'm thinking ClimateMaster and Waterfurnace, for example) are biased in their design towards closed loop applications, but I'm just muttering here and don't expect my thoughts to withstand close scrutiny!

Thoughts, comments and elucidations gratefully anticipated.

Best to all,

Mark


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RE: Geothermal - well question

Thanks all!

Argh - fall is coming and boy, there is SO much information out there ! ! ! Well, I think geothermal, although i would *love* it, is out of the question. I had one guy look at the house and I asked him about the existing well, he said we'd need more wells than the one from the 1800's. He didn't even bother figuring out how many wells we would need, and seemed more interested in getting some bulldozers and setting up below ground. Even then he didn't seem thrilled to give me an estimate.

so then there is the air pump - but THAT requires duct work (which our two story old house has none of, except some old boarded up floor patches where the coal furnace would connect to). more money, duct work, air pump, back up furnace, etc...

now i'm looking at wood stove for the front of the house (living room and foyer are pretty much connected), and maybe a small propane fireplace for the kitchen.

in the future, i'd like to do photovoltaic. . *something* greener to make the world a bit better environmentally (socially, i'm stay at home mom raising two great kids, another along the way soon).

Thanks for all the input!


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RE: Geothermal - well question

Good luck with it Mees. I think geothermal is something that will work for more and more people in time, but it does take a lot of planning and always, always the right professionals.

In the meantime never underestimate the value of insulation. The earth under your house is already contributing to the house temperature a great deal. If you insulate against heat loss/gain that earth mass has a greater influence. Just imagine what it would be like to live in the basement all the time. Insulation makes everything you do with heating/cooling much more meaningful and cheaper.

Best,

M


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RE: Geothermal - well question

Thanks so much everyone for all the input!

Yes, geothermal was VERY expensive - we had an energy star home performance assessment done to the house, so i think we're gonna do the wood or gas stove to heat and put the rest of the money (money? ha! loan!) towards insulation.

Thanks again! I LOVE this website!


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RE: Geothermal - well question

A couple of observations:
Any system is expensive when starting from scratch.
Putting ductwork in an old farmhouse is difficult and will cost some bucks, but it would be required for any forced air system (geo or otherwise).
I grew up near lake Erie myself and one of the big things that varies and is important to an open loop geo is water quality. High mineral contents can exponentially increase your maintenance. Saturated soils also make disposal of the water more complex (vs dry sand for instance).
Incidentally the water used is about 1.5 to 2 gallons/ton. A 5 ton might be required for an old farm house, and go through about 1 million gallons a year. as these units don't run 7/24/365 the 10-20kgal/day indicated above is a little heavy.
Regarding the upstairs question you may run heated and chilled water lines, but you can also run refrigerant lines through interior walls or even outside. This is true of water source or DX units. The most obvious problem is that this will cause you to buy more than 1 appliance (further increasing the cost regardless of system).
If you have natural gas available, it may be hard to get payback with geo, but against propane or fuel oil it's easy to recover the expense. Currently there is a 30% federal (un capped) tax credit that will help as well, while air source heat pumps or conventional systems offer only a $1,500 max credit.
Excavators know how to dig in soil like yours (even back when your house was built they dug the foundation), so horizontal loops are not a problem. Saturated soil as you describe would make a DX or water source trench about the same length 100-125'/ton (12,000 btu's of capacity). It makes for very good heat transfer. The typical soil around the Lake basin usually does not support diagonal boring, but more contractors are working with directional boring.
In most cases, customer satisfaction is impacted more by the installing contractor than the brand or type (water source or direct exchange). Good contractors have very sophisticated operating cost calculation software, so get several bids and challenge them to convince you that it will be worth your investment.
Good luck,
j


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RE: Geothermal - well question

I just built my house (2100 SF) using Geo. Since we had 2.5 acres, we used horizontal loops (cheeper). The WHOLE system (ducts, loops, labor & all Bryant equipment), with emergency heat backup (live in Northern Illinois) was $18,000! Then the energy company just sent us a $2000 rebate check and the Feds will give me money back next Spring on my taxes. Since the high efficiency conventional system would have cost be $14k, I figure I came out pretty good on the deal.

I came home last night and the house was 80 degrees and really humid. I closed the windows and turned on the Geo. The house was cooled in no time.


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RE: Geothermal - well question

We installed a gas fireplace, Valor, and added the fan kit.
We did this after "This Dummy" replaced the forced air heater/AC for about 8 grand. In the 2 or 3 years we have had that fireplace, it would surprise me if that new furnace was turned on more than 3 times or so, and that was only to heat the upstairs. When we redo our master bed/bath I will put another Valor up there. It probably uses less than a 10th the electricity & gas that the forced air does. I have yet to see a $40 gas bill in the winter.
One thing I would warn about is that not all gas fireplaces are for heating, some just pure decoration, they throw out very little heat---fortunately we had a showroom close to us where we could see and "Feel the heat" from different fireplaces.
I know you are getting a gas stove, so maybe there is not such a heat output differences as with fireplaces.
We also put in high effieiency windows and french door--ya even here in Sunny S Calif. I have no desire to make the utility companies any weathier than they already are.

Good Luck with your project.

Gary


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