Geo Thermal Heating/Cooling

[dodgecharger]

There is a vast knowledge base on this forum which is what makes it so great. Do any of the members on here have any knowledge of or using geothermal heating and cooling in the Midwest? How well it works, life span and reliability?

 

[Ivan the Butcher]

I know a very small amount! Our church had a Horizontal system (several hundred feet of lines about 5" below the surface) we ran 3- 5 ton heat pumps. These lasted far better than expected, 35 to 40 years. But as the lines get old and leak, it was less expensive to replace them with conventional heat pumps.

Since I was in charge of repairing them, and knew little about the Geo part (Been a A/C guy for years) I talked to some real geo Thermal guys.

Vertical wells are far more efficient than "field" of horizontal lines. But a 5-ton system will need 3 or 4 wells in the 85 to 100 foot deep area. One or more wells can be used as your water supply, but water wells have to be much further apart (around 150') than thermal wells (30').

I have a friend that tried to use a lake as part of his Horizontal Field, but the problems out weighed the savings.

I haven't talked to a real Geo guy in 20 years so I am sure there are improvements!

Just a related note: If you have a swimming pool and a Central A/C or Heat Pump, there is an affordable add-on that takes the A/C waste heat and heats your pool with it! It is very affordable and adds efficiency to cooling the house. Industrial welding systems have been doing this with ponds since the 60's.

Lastly; a Water Furnace is an air handler, that has a water heater as the heat source, and are very affordable (especially for 1500 sq. ft. or less living units) with electric heat & hot water. These could be part of a geothermal system, but I've never heard of a off the shelf one.

Ivan

 

[bigwheelzip]

Furman University across the street from me has converted their 10 North Village dorms using vertical wells.
It was more challenging drilling, and less efficient energy transfer ground conditions than anticipated. It required additional wells beyond the original design requirement. The required expertise was not available locally, which meant additional expenses for contractors travel.
The drilling cost was higher than estimated, and the highest portion of the project cost.

When the University did their second project, they selected a horizontal design. A future garden area was excavated, and copper tubing from spools was looped. Extra loops were spooled out for future use. This design reduced installed costs.


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[comfortsource]

OP,

as a fellow midwestern'er and HVAC/Plumbing contractor, I can vouch for the energy savings of a "geo" unit in our parts. You are a little further north so YMMV. However, the great benefits to geo units are the fact that instead of ambient air circulating around an "outdoor unit", you are using a way more effective media to dissipate and absorb "heat" (water).

this allows for a very energy efficient AIR CONDITIONER. Where "geo" units lack a bit for us in the colder climates, is the heating side.

air to air heat pumps ( the ones that a person normally sees with an outdoor unit above ground) will drastically lose operational efficiency and productivity at and below 30-35 degrees F (depending on humidity). But can work effectively above those temperatures. A geothermal system allows for that compressor to be operating in its "wheelhouse" of 50 degrees all the time. This would potentially be kicking out anywhere from 105 degree outlet air, up to, maybe 120 deg. if you are fortunate.

in contrast, a high efficiency gas furnace would be somwhere around 135-145 (depending on temp rise furnace is rated for) so in IA and your northern neighbors, a gas furnace would help heat a home a bit better in the darkest, coldest times of the year.

recap: geothermal is an EXCELLENT cooling system as that compressor will pull less amps (equals less energy cost) and produce satisfactory results.

a geothermal system may not adequately heat the home in the dead of winter and will subsequently require some "back-up" source to aid in the additional heating requirements. This is typically done with resistance heat and that will cost more than a gas furnace, operationally.

disclaimer: all homes are not equal, nor the locations. A manual J heat load calc will be required for proper sizing. I also agree, deep well-type piping schematics are much better than horizontal runs due to available real estate. Things to consider is soil composition and typical moisture levels in said soil. That is usually the limiting factor on design.

hope that helps and doesn't muddy the water too much...

 

[jeffrefrig]

This was interesting. I'm a retired Steamfitter on the HVACR side, and my last 17 years was spent at The Pittsburgh Public Schools. One of our schools was slated for Geothermal HVAC, but it was cost prohibitive and they nixed it; mainly because of the footprint of the building and the amount of drilling they'd have to do. That was the closest I came to a Geothermal system! In downtown PGH there is a river below the rivers and the city that many buildings tapped into for water-cooled condensers, but that's a little different. I think that was part of an old canal system. I'd be interested to see a Geo system installed, but I'm in no mood to ever work on any HVAC or refrigeration system ever again! (Except mine...maybe!)

 

[MetalMan]

I have a geothermal system which was installed as part of new home construction 10 years ago - Columbus, OH area. I bought the home with the system already installed so don't know the installation costs.

Heating and cooling ~3500 sq. ft.

Have been extremely pleased with ours...very quiet and apparently very efficient. No outside unit to deal with.

We keep temps at 68 in winter and 72 in summer and system has not had any problems keeping up during extremes in outside air temp. The "emergency" electric supplement strips have never turned on even in below zero weather.

Only issue early on was when it was determined that all of the air had not been bled out of the system which caused some erratic pressure readings but no issues in system operation.

This past summer, I replaced both circulating pumps as one of them had started leaking. Service cost was $2k for the pumps and re-pressurization of the system.

I have the system checked twice per year and nothing else has needed to be done over the years.

Happy camper.

 

[dodgecharger]

Thank you folks for your help and information. It is greatly appreciated as I know nothing about geothermal heat. You guys are fantastic.