Geothermal Heating/Cooling

GreenPowerManiac · October 2015

Just keeping everyone updated on my dual Geo system installed last January late.

After about $35,000 invested, $23,000 after tax credits, got it fine tuned.
Systems include:

3 ton electric scroll Heat pump radiant floor heating (Water to water). Already working in unison with the Solar water heating/Solar voltaic system I designed and implemented via ATS (Auto Transfer Switches).
&
3 ton electric water to air stand up furnace for additional heat or AC. Supplemental.
The well pumps have been converted to constant pressure pumps which work beautifully. One pump for house, the other for Geo.

Off of LP gas almost completely. Still need to fire up the gas grill outside....hehehe

Had a lot of fixes to mostly water usage and control of flow and one water valve went bad inside stand up unit, however, regulated it nicely to which the well pump would not be overloaded.

The trade off from LP to Geothermal is electricity consumption. Had to contact the power company to switch my electric usage to ALL electric heating/cooling. Saved a few cents per Kwh.

Everyone learned a Ton of stuff setting this up including my well guy... Just an update. Will have to update my website too, which is FREE of ads by the way.......

techntrek · November 2015

I was big on geothermal, even talked a friend into it for his new house 6-7 years ago, until the mini-splits started catching up on the SEER/HSPF ratings a few years ago. With less cost, complexity, and little maintenance I would go with air-source mini-splits now.

westbranch · November 2015

Techntek, Have you thought of using it in a NORTHERLY longitudinal location where it dips to -40? (Celsius or Fahrenheit, your choice...) and is -30 in the daytime.... Burrrrr!!

techntrek · November 2015

LOL, obviously not an option up there. But some are good to -13 F (-25 C), not that they'll keep you toasty at that point.

westbranch · November 2015

Ya, a buddy has a Geo unit with 2 loops at 10 feet and another 2 above those at ~ 6 feet down.. he lives on a near-desert site with 45% slope to the S and SW forested with Douglas Fir trees so he ground does not warm up that much, he 'thinks' that his underground temp in march is close to 32* and the exchanger in the house runs 24/7. He is lucky that he gets solar warming through his large S facing windows on sunny days.

inetdog · November 2015

westbranch said:

Ya, a buddy has a Geo unit with 2 loops at 10 feet and another 2 above those at ~ 6 feet down.. he lives on a near-desert site with 45% slope to the S and SW forested with Douglas Fir trees so he ground does not warm up that much, he 'thinks' that his underground temp in march is close to 32* and the exchanger in the house runs 24/7. He is lucky that he gets solar warming through his large S facing windows on sunny days.

If the soil temperature is 32F in march at 10' underground, that is clearly not deep enough for the earth loop of the system.
A vertical drilled well configuration might be more suitable for that kind of winter, but would require the ability to bring in a largish well drilling machine.

westbranch · November 2015

On that slope he did the best he could, as far down as he could dig on that side slope * (his backhoe) plus access for the dump truck to bring in the washed sand needed to lay in around the pipe. I keep trying to convince him ti get some evacuated solar tubes and reheat the 'underground' when he gets all that sun all summer long. Cheap solar heating in my book, all the other paraphernalia is there, pumps location etc

PS the bottom of his well is over 700 feet below the basement floor and the well pipe is ~ 200 feet away and down from the house too... ouch and only 3 gal/min...

inetdog · November 2015

westbranch said:

... I keep trying to convince him ti get some evacuated solar tubes and reheat the 'underground' when he gets all that sun all summer long. Cheap solar heating in my book, all the other paraphernalia is there, pumps location etc

That is a very interesting possible way to store thermal energy! I suspect that too much of that heat would just be conducted outside the ability of the heat pump loop to recover it again, but it is worthy of some calculations.

westbranch · November 2015

I was thinking of countering the cooling effect caused by the winter heat extraction if nothing else

GreenPowerManiac · November 2015

That's the way a ground loop Geo works. Heats in summer, extracts in winter. Although the efficiencies dwindle after a month or two of cooling/heating. Was going to do that, yet with harsh winter temps, decided to drill a well for consistent water temps of 54 degrees here.

techntrek · November 2015

With evac tubes in the system they would provide some useful heat during the winter, too.

GreenPowerManiac · November 2015

Yea, I guess we can get some heat out of an ice cube.......LOL

Solar2 · January 2016

Some forty years ago when Geothermal was just starting I got involved with a research project to see if we could store waste heat from air conditioning in the ground for subsequent use in heating. We ran a bunch of heat into the ground for several days then reversed the system. We didn't get even one percent of the heat back.

The Geothermal system I have now uses three 350 ft vertical loops. They are in granite, wet and are grouted with high thermal conductivity grout. The max I have seen the 3.5 Ton HP pull the loop temperature down is 5 deg F. If we shut off the Geothermal and burn wood for a day the loop completely recovers.

LucMan · January 2016

You are lucky that your geology supports Geo. The reason that your system is working properly is because the verticle wells are "wet" and properly sized for your equipement.
Most of the Geo systems that I see work poorly after January as the loop temp is now below 32 degrees and can't recover.
The loop temps keep dropping until the systems occasionally lock out on low temp. The electric backup heaters keep the indoor temps comfortable, not good for overall COP's, basically running on electric resistance heating.
Loops in clay or dry rock just don't work. Do a search on Cornell college Geo system failure.
Anyone that doesn't consult with a geologist before installing Geo is asking for disappointment.

WaterWheel · January 2016

LucMan, Thanks for the heads up about loops in dry clay. I had slightly considered bringing a directional drill in to run a large loop about 15-20 feet deep on my property which is all red clay about 50' deep before hitting rock.

Can anybody tell me if using a 390' deep water well for a thermal source will work. The water table on the property is about 45' down but the well was pushed to 390' before we hit a 100 gpm stream.

Brock · January 2016

Our field is horizontal and mostly in clay at about 10 foot depth. I did have our field over-sized to 6 ton instead of the 4 ton to match the heat pump, it didn't add that much in cost and I figured it would hold up better in winter and if I ever wanted to up-size the heat pump I could. Although now I think I would down-size it or go with a two stage for even more efficiency

At the end of the heating season it has been rising about 1 degree a year, I attribute it to settling and making better contact with the pipes. The first year we went to 32F but this year so far I am only at 39F, but it has been a warmer winter, last winter was 36F for a low, starting at 70F in the fall after the cooling season.

LucMan · January 2016

foolami said:

LucMan, Thanks for the heads up about loops in dry clay. I had slightly considered bringing a directional drill in to run a large loop about 15-20 feet deep on my property which is all red clay about 50' deep before hitting rock.
Can anybody tell me if using a 390' deep water well for a thermal source will work. The water table on the property is about 45' down but the well was pushed to 390' before we hit a 100 gpm stream.
You could do a pump & dump system. 1 well with a pump to supply water and another to dump the water back into the aquifer. The only issue is you have to run a 1-1/2+ hp pump to supply the water to the Geo.

WaterWheel · January 2016

With 100 gpm flow through the lower part of the well I had hoped it would provide enough temperature difference to allow a 1" line to drop down and back up through 345' each way (water is 345' deep in well).

Solar2 · January 2016

foolami said:

With 100 gpm flow through the lower part of the well I had hoped it would provide enough temperature difference to allow a 1" line to drop down and back up through 345' each way (water is 345' deep in well).

Sounds like you have a good well. I would recommend open loop.
This gives you top incoming water temp that will stay up all season.
Usually you can size the HP to do all your heating and DHW needs.
You benefit from lower initial cost and a definite efficiency boost.
You didn't give us your static water level but a loop hanging in an empty casing or uncased rock well will do you no good.

LucMan said:

You are lucky that your geology supports Geo. The reason that your system is working properly is because the verticle wells are "wet" and properly sized for your equipement.

I thought we were un-lucky because we could not go open loop.
We just don't get good flowing wells up here.

Actually the grouting is the big difference in vertical systems.
I went through the math and came out with 11 deg F difference in entering water temp
between high thermal conductive and regular grout.
Eleven deg makes a big difference in the efficiency and output of a HP.
High thermal conductive grout is not much more costly than regular.
It is harder to work with however, harder to mix and you need a good pump to get it down.
It is a job for the well drillers with big equipment.

LucMan · January 2016

The grout means nothing if you are in dry solid granite, because it doesn't seem to recover quick enough. Read the report from Cornell's Geo install, lots of excellent info available from their miscalculations.

Solar2 · January 2016

LucMan said:

The grout means nothing if you are in dry solid granite, because it doesn't seem to recover quick enough.

Any tables I have found show Granite to be the highest thermal conductivity of any of the common rocks
and much higher than soil, sand etc..
This is also consistent with literature from the companies offering high thermal conductivy grouts.

WaterWheel · January 2016

Static water level is 45'.

Geothermal Heating/Cooling

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