Wacky old House Question

FME · January 6

Thinking of a custom geothermal installation.

I have a 9000 sqft house in NH built in 1921. Original heating was coal forced hot air. I've got large ducts coal in the coal bin and 3 10T oil fired furnaces. It costs a fortune to heat the place even just to 64! (I know get and audit and insulate the air infiltration).

My question is kind of wacky. Geothermal here would be very expensive (15-20K just to drill one well 250'). My thought is to create a large temporary water holding tank to serve as the heat sink and put heat exchangers inthem conected to a geo- heatpump. I have done some rough calculations and I think this could work up to about 20 tons.

I also have two 1200 gallon water storage tanks that are original to the house but no longer used ( Thick plate steal with rivets and all). It was used as an expansion tank until about 10 years ago so I shouldn't have any really leak issues. I also have an original well that I am not using but has plenty of water (15-20 GPM).

Plan would be to put heat exchanger in water tank. Fill tank with water, pump heat out of the tank in the winter from well temp of 55 down to 35 or so. That's a 20 degree drop for 1200 gallons or 200,000 BTUs per tank change (20 degrees x 1200 gal x 8.34lb/gal). The ability to use access up to 20 degrees of temp changes is a real plus here.

I would need to drill one drain well to return water to aquafer but could replace water volume in tank every 1hr-1.5hrs if needed.

I will need to find a local pro to properly size and design this, but wanted to check with the Pros here to see if I missed something and am way off base. Has anyone here of people using large water tanks in this way.

Thanks,
Fred

Jamie Hall · January 6

Unnecessarily compilated. If your steady state well yield really is 15 to 20 gpm -- which by the way it very likely isn't -- you need to do at least a 24 hour and preferably 72 hour drawdown test on it to see what it stabilises at) -- you can use that wonderful formula for hydronics. Let's say a 20 degree delta T, 20 gpm, gives you 200,000 BTUh to play with. You can't get more out of the well than that, even if you store it and draw it down (you'd could get more power briefly, but not more energy, and you need heat all 24 hours...)(note that a heat pump doesn't change the energy derived from the source -- it just makes it available at a different temperature).

You'd still have to drill the return well, of course.

Unless that house is right on the coast or perhaps no farther inland than Durham or Exeter, that might be enough heat. Might not, too.

On tightening up and insulating the house. How much is feasible depends on what you are doing to the place. Restoration? Modernization? Gut rehab? Makes a big difference. Reducing infiltration, however, is a good place to start on any of those -- particularly restoration. Be wary of slick salesmen with modern windows, however (a particular beef of mine, sorry). You'll do at least as well if not better on a hose built in 1921 and save a real bundle of money by tightening up the original windows and making sure they operate properly, and then using either inside storm windows or outside ones -- inside is preferable in a restoration, although they do have to be removed seasonally unlike triple tracks. But triple tracks look tacky... ! You may also be able to do a lot in the basement by sealing up infiltration around the sills.

ethicalpaul · January 6

You don't want an "open" system like this. You want a closed system with a loop. I think you are overestimating the cost of drilling.

jesmed1 · January 6

Jamie Hall said:
You'll do at least as well if not better on a hose built in 1921 and save a real bundle of money by tightening up the original windows and making sure they operate properly, and then using either inside storm windows or outside ones --

^^This. I maintain a circa-1930 4-unit condo building outside of Boston. Two units have had their windows professionally weatherstripped with spring bronze and silicone rubber bulb seals, new parting beads and sash ropes, and the windows are now sealing/operating better than when they were new and will last another 100 years.

The other two units trashed the original windows against my advice/pleading, with cheap double pane vinyl windows that won't last 20 years. Based on energy consumption comparisons, the weatherstripped original windows with storms are performing just as well as the new vinyl windows.

leonz · January 6

Hello Fred,

An open loop system would be capable but very expensive to drill and then you have to worry about a possible refrigerant and lubrication leak in the future or sooner from a failed compressor that would pollute the water table and upset the neighbors as the water would be contaminated FOREVER!!!!!!!!!!!!!!

Your 15-20K estimate for a geothermal open system well is much too low as you may be looking at $100.00 a foot of steel cased well to bed rock with a sand mix concrete annulus poured and pushed into the well casing with a pipe swab pushing concrete through the casing and out up through the annulus of the well bore up all the way to the surface plus a concrete pad surrounding the well to divert surface run off, plus a well screen, the cost of a jet pump, and secondary pressure tank if used and building permits to name but a few items.

Do not ever let anyone tell you that a geothermal grouted system is more efficient!!!!! it is not!! this is because clay geothermal grout is a net insulator and mason sand is a better heat exchanger in a closed loop system but you still have to worry about a refrigerant leak and compressor failure that would cause a refrigerant leak with both a closed and open geothermal system.
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Coming back to what you have, as you have coal, a coal bin and furnace ducting already that may still be in good condition I would find a EFM stoker coal stove dealer near you and ask them to give you an estimate for a coal stoker furnace and or coal stoker boiler with an in plenum heat exchanger to heat your home and ask about selling the coal you have to a local coal yard or coal user to make room for the new coal you would need as it will cost you much less to heat this home with coal and your payback will be immediate.

You will spend a great deal less money on a coal stoker furnace or coal stoker boiler from EFM and you will save a great deal of money on heating and you can also make all your domestic hot water the year round if you wish to do that as well.

Please send me a PM as I would be more than happy to help you with this if you have questions as I have been a heating my home with coal since 1982 and its easy to manage especially with a coal stoker boiler as the heat is smooth and even.

The EFM companies phone number is 570-385-1892 and they will help you with any questions that you may have and who the local EFM dealer is in your area.

If your coal bin has rice coal in it, you will be able to use it in either the EFM DF-520 coal stoker boiler with a heat exchanger in the furnace plenum or the EFM AF model warm air furnace to heat your home.

Leon

Hot_water_fan · January 6

I usually am extremely anti-geothermal because of its expense. However! In this situation, I think it might work. It’s got to be closed loop though.

Jamie Hall · January 6

ethicalpaul said:
You don't want an "open" system like this. You want a closed system with a loop. I think you are overestimating the cost of drilling.

Two thoughts here. First, on the cost of drilling. Like many other things, the cost of drilling a well varies widely from region to region. Further, there are well drillers... and well drillers. Constructing a well properly, as @leonz described, is a good deal more expensive than running a drill down X feet, pounding a casing down a bit (almost ensuring a failed well) and beating it out of town before the posse gets there.

Bottom line - considering where our OP is, I don't think the cost of drilling and properly competing a well is out of line. If anything, low.

I have no particular beef with open systems. They are, however, quite different, thermodynamically, from closed systems. If anything the risk of groundwater contamination is higher in a closed system, as the coolant is likely to be treated at least with antifreeze, if not corrosion inhibitors -- and you are deliberately running it through pipes buried in the ground without any form of secondary protection. Also, if you dealing with a high yielding well (or a year round stream!) the flow rates and thus power of the source can be remarkably high, whereas to get that power from a closed system you are depending on the heat exchange rate of your buried lines and may need more wells for vertical systems. On the other hand, permitting a closed system is likely to be much easier (it may not even be possible to permit an open system) as you are not actually withdrawing water from the ground.

mattmia2 · January 6

Youre6 concerned about underv a quart of refrigeration oil in millions of gallons of water but not about burning coal...

pecmsg · January 6

mattmia2 said:
Youre6 concerned about underv a quart of refrigeration oil in millions of gallons of water but not about burning coal...

It's a legitimate concern. Only a few gallons of POE oil can do a lot of damage.
Many areas are banning open loop underground systems.

Hot_water_fan · January 6

If an open loop turns out to be feasible, the tank is totally unnecessary. Pump, then dump.

leonz · January 6

mattmia2 said:
You're concerned about under a quart of refrigeration oil in millions of gallons of water but not about burning coal...

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I am simply trying to explain to the best of my ability and knowledge about well drilling.

I use a coal stoker boiler to heat my home because oil is too expensive and my oil dealer let me run out of fuel 4 times too many.

Giving you a direct example of water contamination is the Coors brewery in Golden Colorado.
Over 24 years ago the sanitary sewer line buried in the basement floor of the brewery developed a crack in it.

The solvent and water they use to clean the aluminum before it is pressed/punched into can form and coated with the plastic liner leaked into one of the water wells they use for the brewery for beer making from the cracked sanitary sewer pipe and they spent a great deal of time flushing out the well and using more electricity to pump the lost water to the sanitary sewer to dispose of it and pay the City of Golden for their sanitary increased use rate.

It is never easy to clean up a mess like that as "safety solvents" that have a high flash point can and do cause a great deal of harm where simple isopropyl alcohol can accomplish the same work.

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Water tanks in basements were used as water cisterns as they typically collected rain water for drinking, bathing, clothes washing and dish washing.

The general rule for geothermal wells is 100 feet of drilled well depth for every ton of useable heat exchange-(Cough, Hack, Wheeze) and at a $100.00 a foot..................

The oil is the problem because it will contaminate the aquifer and once that happens it will never flush out.

He has a home that was built to house several generations of one family and it is a very old home with little if any insulation.

The home may very well have had an octopus coal furnace that was hand fired using gravity heat to heat the home.

An underfed coal stoker boiler will provide less costly heat per million BTU using rice coal each and every year with minimal work using its underfed/tuyere/pot stoker that is auger fed from a coal bin IF the air plenums are intact and not rotted out and a heat exchanger can be used in an intact plenum for the forced air heat.

If the air plenums are rotted out it would be possible to use the existing vents for bottom one pipe steam more easily.

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If a homeowner has enough useable land like a grass runway using a trencher to install a geothermal pipe is easy but the proper amount of care in burying the pipe is necessary as the pipe has to be buried in a layer of sand to protect it from any rocks to prevent any damage form compaction as much as possible.

I would cringe when I saw pictures of geothermal well drillers using small track drills and drilling a radial pattern of drill holes at a 45 degree angle in a circle in a small confined space and inserting copper pipe
as the method of exchange in bare ground and tying in all the pipes together in a small vault in the center.
All I could do is shake my head.

I hope we hear more from this gentleman as he needs help.

old_diy_guy · January 6

You neglected to mention what's coming out of the chimney when burning coal.

JUGHNE · January 6

I have done several pump and dump water to air heat pumps, although many years ago.
These were all in the country on ranch or farm.

We would use their water well for supply and are fortunate to have sandy soil that allowed the dump water to go into a small pond on their property.

In some cases we used an abandoned well on the property, or an option is to drill a dump well.

The early ones put a lot of cycles on the submersible pump. Now variable speed/output pumps are available to deliver the correct amount of water as needed.

As far as comp oil contamination of the groundwater, IIRC the heat exchangers are double walled so any gas or oil loss would be within the machine and it would shut down on low pressure.

hot_rod · January 6

A good first step is a heatloss calculation for the home. You need some solid number to build a system around.
I would guess a 200 225,000 btu/ hr design load. So a 18- 20 ton heat pump. 2.5 gpm per ton as a guesstimate . So a well capable of 30 gpm.

Ground loops 5-600 feet per ton. Trenched with a large bucket allowing multiple loops per trench could be less than wells? Depends on the land you have available and the ability to trench 5’ or so deep

Jamie Hall · January 6

A word about contaminating soil and aquifers. First, it's not a good idea. Just sayin'. However, having said that, one must remember that there are differences between the various contaminants as to the problems they pose. For example, a leaking underground fuel tank with fuel oil or diesel in it is going to cause a costly soil remediation problem. However, diesel or fuel oil doesn't migrate much in ground water, so once the contaminated soil is removed one is pretty much done. Gasoline, however, does migrate -- and leaking underground gasoline tanks involve expensive and long duration -- sometimes years -- pumping of contaminated ground water to clean up.

Here we are talking about other contaminants, however, and without knowing the chemical composition of what is in the refrigerant, for instance, speculation is useless -- or worse, uninformative. Some coupounds -- trichloroethylene, for instance -- are particularly evil. One quart of TCE will render some 15 acres of aquifer permanently unusable. (well permanent in the sense of a human lifetime or two).

leonz · January 6

old_diy_guy said:
You neglected to mention what's coming out of the chimney when burning coal.

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I did not neglect mentioning it because I was concentrating on explaining the issues with geothermal heating and cooling and the pollution risks with water to water heat exchange systems.

Anthracite coal burns much cleaner than wood or bituminous coal because it is pure carbon in composition and has a much greater BTU value per pound.

Anthracite coal and Bituminous coal are totally different in thier burning characteristics as Bituminous coal has a higher volatile composition and lower carbon content and requires huge amounts of combustion
air to burn and does not burn cleanly like anthracite coal.

The only reason power plants burn Bituminous coal in the east is because it is abundant and costs much less than anthracite coal.

hot_rod · January 6

leonz said:

old_diy_guy said:
You neglected to mention what's coming out of the chimney when burning coal.
=================================================================

I did not neglect mentioning it because I was concentrating on explaining the issues with geothermal heating and cooling and the pollution risks with water to water heat exchange systems.

Anthracite coal burns much cleaner than wood or bituminous coal because it is pure carbon in composition and has a much greater BTU value per pound.

Anthracite coal and Bituminous coal are totally different in thier burning characteristics as Bituminous coal has a higher volatile composition and lower carbon content and requires huge amounts of combustion
air to burn and does not burn cleanly like anthracite coal.

The only reason power plants burn Bituminous coal in the east is because it is abundant and costs much less than anthracite coal.

I think you want a gasification coal boiler to keep emissions clean, maybe be EPA compliant?

leonz · January 7

Good morning Bob,

As far as I know, none of the lignite, bituminous, anthracite or lignite fired coal stoves or stokers are gassifier's that use a catalyst and they are not designed to create coke while burning or burn coking coal.

A professor in South Africa designed a forced draft catalytic coal stove that created coking coal and also burned coke with a forced air perforated vertical combustion chamber design back in 2004 that could be used for cooking and heating but the coal mined in South Africa.

96 percent of the coal in South Africa is Bituminous Coal, 2 percent is Anthracite Coal, and 2 percent is Metallurgical grade Bituminous coal. Seventy percent of the coal mine din South Africa is used in South Africa.

The catalyst substrate used for wood burning would be plugged with fly ash and be damaged.
Stove makers that build stoves that can burn both wood and coal recommend that the catalyst be removed before burning coal for this reason.

The anthracite coal stoker stoves, furnaces and boilers whether they are of the forced draft flat fire grate, forced draft sloped fire grate or rolling fire grate stokers that use induced draft combustion pulling combustion air over the coal burn cleaner because of the pure carbon content in the Anthracite Coal and the huge amount of combustion air used with the induced or forced draft fans used to maintain combustion.

The western Sub Bituminous Coals mined in Western Canada, Alaska, Wyoming and Montana burn very well in stoker stoves and hand fed stoves and boilers as they are more friable (break more easily) and have half the BTU value per pound so they burn to a much finer ash more quickly in and create much less dead ash per pound of Sub Bituminous coal.

The lignite coal mined in North Dakota, Texas and Louisiana is Lignite coal and is a very dirty soft coal which is referred to as slack coal in England.

If anyone is interested they can wander over to youtube and type in AHS S130 coal stoker boiler in Montana
and learn how a coal mine electrician in Montana is using an AHS S130 rolling grate coal stoker boiler to heat his home and his domestic hot water the year round.

He removed his forest eater and has much less work and dead ash to deal with his coal stoker boiler as his rolling grate coal stoker burns the Montana Sub Bituminous coal very cleanly with barely any smoke and the local Sub Bituminous oiled stoker coal he uses creates very little dead ash because it burns so well as it is very friable and breaks up easily while burning to release the volatiles to create heat. He burns more of it but the cost of oiled Sub Bituminous Coal per 5 ton trailer load is less than a quarter of the cost of a ton of Anthracite Pea Coal.

ethicalpaul · January 7

There's a lot of fear uncertainty and doubt in this thread. I'll throw some of my experience out here (again, sorry) for people to consider, I don't care to get into a fight about it because I've done it and I know.

- The drilling cost is the drilling cost, but it's not as outrageous as people want people to think. The contractors know what they're doing. They are licensed, and permits are pulled. They know how to place the loop and terminate it in your basement and pressure test it.
- The steel casing is only required until you get to bedrock. In the East, that's damn quick. Then after that the solid rock supplies a good structure. In my case in CT, I needed only 20 feet of steel pipe.
- The grout is engineered, and it's tested. I don't know what you have against grout, @leonz but its thermal properties are known and measured. There's not some "thermal grout" mafia out there that is trying to trick people. Geez.
- My antifreeze in my loop (which I never actually needed--my loop temp never got much below 40F) was edible and wasn't going to poison anything even if it did ever leak, which is extremely unlikely.

The "pump and dump" systems, in addition to needlessly wasting groundwater, and being about impossible to get approval for nowadays (I believe), can damage the heat pump due to mineral deposit buildup. Why you would want to take a thing that in the correct conditions will run for 20 years without service and instead gunk it up with a bunch of lime, iron, etc, is beyond me.

Jamie Hall · January 7

Perhaps you can hepl me, @ethicalpaul , since you seem to have some good sources on deep well type geothermal. What I am interested in -- in a purely intellectual way at the moment -- is what research has been done on, and what data are available, on the long term heat transfer rates for these things for various types and conditions of rock -- or for those lucky enough to have them, unconsolidated aquifers. Particularly such aspects as the permeability of the aquifer -- possibly relating to well yields, for instance (NOT pump and dump as you describe it, that's quite straightforward, but essentially a heat exchange pipe solidly grouted into an aquifer) Is the mechanism primarily conductivity through the solid aquifer material? Is it actually extracting heat from flowing groundwater?

leonz · January 8

ethicalpaul said:
There's a lot of fear uncertainty and doubt in this thread. I'll throw some of my experience out here (again, sorry) for people to consider, I don't care to get into a fight about it because I've done it and I know.

- The drilling cost is the drilling cost, but it's not as outrageous as people want people to think. The contractors know what they're doing. They are licensed, and permits are pulled. They know how to place the loop and terminate it in your basement and pressure test it.
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No, the statement "the drilling cost is the drilling cost" is not that simple nor is it a blanket statement that is a fits all, does all.

($100.00 a foot is still $100.00 a foot for a water well or a geothermal well)

- The steel casing is only required until you get to bedrock. In the East, that's damn quick. Then after that the solid rock supplies a good structure. In my case in CT, I needed only 20 feet of steel pipe.

(rock can be close to the surface or very deep in gravel soils or in my case my water well was drilled below 292 feet in solid colloidal clay with no rock in sight and my well caved in all the way to the bottom of the 92 foot well casing).

- The grout is engineered, and it's tested. I don't know what you have against grout, @leonz but its thermal properties are known and measured. There's not some "thermal grout" mafia out there that is trying to trick people. Geez.

(BAROID LAUGHS ALL THE WAY TO THE BANK. Any well driller that does this for a living will tell you it is a net insulator. There are a great number of published papers discussing geothermal heating and cooling and the many components involved in it).

- My antifreeze in my loop (which I never actually needed--my loop temp never got much below 40F) was edible and wasn't going to poison anything even if it did ever leak, which is extremely unlikely.

(the compressor oil and the gas refrigerant is what I worry about).

-The "pump and dump" systems, in addition to needlessly wasting groundwater, and being about impossible to get approval for nowadays (I believe), can damage the heat pump due to mineral deposit buildup. Why you would want to take a thing that in the correct conditions will run for 20 years without service and instead gunk it up with a bunch of lime, iron, etc., is beyond me.

(Many semi open loop systems are water wells that have been drilled deep in granite bedrock (1,550 feet deep in Manhattan and other wells nearby in and around the City of New York.
They are still being drilled and installed.
They use and reuse the same well water as the heat exchange medium where the water is pumped from a deeper depth in the bore hole and pumped through the geothermal physical plant via a separate heat exchanger and allowed to drain back to the water well through a 2 pipe sanitary seal in the well casing.
Many pump and dump geothermal wells have 2 wells where one is used for seasonal cooling and the other used for heating with two different well depths to water.
You can have a semi open loop system in a deep drilled well with a sealed base sump in the deep drilled well casing which is mud drilled in place with a sand mix concrete pumped in the annulus of the bore hole once the desired well depth is reached (100 foot of well depth may provide up to one ton of cooling in gravel soils or bed rock).

I worked for a bad careless well driller and I learned what not to do for sure.

=================================================================

ethicalpaul · January 8

Jamie Hall said:
Perhaps you can hepl me, @ethicalpaul , since you seem to have some good sources on deep well type geothermal. What I am interested in -- in a purely intellectual way at the moment -- is what research has been done on, and what data are available, on the long term heat transfer rates for these things for various types and conditions of rock -- or for those lucky enough to have them, unconsolidated aquifers. Particularly such aspects as the permeability of the aquifer -- possibly relating to well yields, for instance (NOT pump and dump as you describe it, that's quite straightforward, but essentially a heat exchange pipe solidly grouted into an aquifer) Is the mechanism primarily conductivity through the solid aquifer material? Is it actually extracting heat from flowing groundwater?

It's a great question! I thought about this myself quite a bit, but I don't have a good answer for you!

I can tell you that my well filled with water up to the level of the water table the day he drilled it, and it was relatively shallow--shallower than 50 feet as I recall. They have to fill the loop with water as they lower it to be able to push it down the well otherwise it wants to float as you can imagine.

This led me to believe that there was flowing water almost the entire depth of my well...but how much flow? I have no idea but I'm quite sure it does pull heat from the groundwater around it and the groundwater, however much it is flowing, is carrying "fresh" heat to the well.

If every home in a dense neighborhood had a vertical ground source loop would it become less and less efficient due to heat loss? I think it's possible--the ground is heated by the sun, not from the internal heat of the earth--and it's finite! Heat is restored during the hot seasons from the air conditioning, but it's not as much as is lost during the winter (at least where you and I live).

There was a whole community of homes in Canada I read about where they made a bunch of common wells, I wonder if I can find information about how that worked long term...

Hot_water_fan · January 8

@ethicalpaul have you seen this Canadian subdivision? It's called Drake's Landing. https://www.dlsc.ca/

ethicalpaul · January 8

Yes! that's the one I was thinking of. They have community solar as well as community ground-source heating/cooling (what they call "borehole")

https://www.dlsc.ca/borehole.htm

JUGHNE · January 8

As far as the "Pump & Dump" systems, we are located in an exception area with the Ogallala aquifer beneath us. All of these I have installed were in the country for farms and ranches.

IMO, the only groundwater wasted is what is pulled up and then contaminated before returning to the earth. Mostly nitrates from previous ag practices. But that is now monitored more than ever.

One might say the energy used to pump the water is wasted, but is part of the cost of HVAC operation.

I just pulled a file of the last one installed, that was in 1995. Still running after 28 years. A testimony to the water we have available here. That project also has 2 electric WH's that are still in use.

I installed at least 7 water to air HP's in that decade. At least 4 of them have failed within the last 10 years.
Owners were complimentary that I had advised them this route rather than LPG.

All installations had a 3 way dump valve that would allow the discharge water to be used on the lawn during the AC seasons. Some used the water year around for livestock watering.

Again this is the exception.......not for everyone.

ethicalpaul · January 8

The reason I consider it wasted is because water deposited on the surface is not the same as water in an aquifer. The surface water will run somewhere, and will evaporate and doesn't all (if any) make it back to the aquifer.

JUGHNE · January 8

But then we get more rain

ethicalpaul · January 8

Someone does! I don't think they do in Arizona...it blows up here to New Jersey!

FME · January 15

Thanks for all your comments. To clarify the house nolonger uses coal which was removed in the 50s or 60s. Currently burning oil for forced hot air.

Initital thought was not to have an open loop system because of contamination issues discussed above.
Would have a closed loop system with a heat exchanger installed withing the 1200 gallon water tank the heat exchanger would be one end of a closed loop that would connect to the heat pump in a closed loop. The open loop portion would be used to fill the water tank. Also would likely need to drill 2nd well since source well is not deep enough to accept the discharge without a likely adverse impact to well temperature,

Thanks all.

Wacky old House Question

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