What is the process to install a geothermal heat exchange system for residential heating and ac?

Question

Our home is in Minnesota and was built in 1907. We heat our house with a gas/forced-air furnace (less than 10-years old) and seek information on how we might retrofit to a geothermal heating and cooling system. How much a pool or coil is needed per sq/ft of heated/cooled interior space ? Is the installation expensive?

Answer 1

For starters as far as retrofitting. The only certain significant change in the house will be the introduction of a electric duct heater, above the actual furnace. They both will go in the spot that your old furnace occupied. The duct heater is usually installed only as a backup to the geo unit and to provide fast heat or additional heat on cold days. You may be able to use the existing ducting or part of it. Your local geo dealer will be able to tell you when he does his site survey.
The type of loop you use, will depend on the site. There are several types for different property layouts and resources.
1/ A closed lake loop. Line out in a lake and back. Gaining acceptance now, as materials used in the loop are more enviro freindly, but you will likely still need approval from your municipality. Relatively cheap to install.
2/ Horizontal loop. A series of trenches on your property, connected at a header trench, dug below frost line. Not as cheap as a lake loop and requires a good size parcel of land.
3/ Vertical loop. A series of wells, drilled on your property, connected together with a header trench to below frost level.. The most expensive loop as a well driller is involved. Generally these loops go to 500 feet and return. Not much land is needed, can be put into the space of an average subdivision home's driveway.
4/ Open well loop. The cheapest solution of all the loops as a rule. It requires an existing water well that can produce at a minmum, 16 gallons per minute without running dry. You need that much to still be able to use the heat pump and for your domestic water needs. You also need a enviro freindly place, for the discharge water to go. It will be a different temperature than the surroundings, so you may need a municipal approval to go this route. By the way, if the discharge goes to your pond, forget about stocking it later with trout. We had a customer do this with $10,000 of rainbow. I guess he wasn't thinking and had some cooked fish in days.
Before you invest much time or effort in this, take a good look at what your current energy costs are and how long you plan to be in the home. You likely will save money going geo, but it may not pay itself back in the timeframe you need to make it worthwhile.
How much piping will be needed for your house? Generally, for a 2,000 square foot home, you'll need to run between 1300 - 1800 feet of pipe, depending on how damp the ground conditions are. The damper the better. A lake loop that's well below ice to avoid damage, requires the least pipe. A vertical or horizontal loop in sandy soil, generally the most pipe. The size of the actual furnace for a home that size is around a 3 ton unit.
To get an idea of price, you'll have to get a dealer in to discuss your options. I've seen these go in, from 14 thousand canadian dollars to 30 thousand dollars.
I found a link at an old co worker's web site that may help you, it's an installation manual in pdf form and contains a lot of useful info http://www.proventmechanical.com/r300manual.pdf
Hope this all helps. They are a good idea if your payback for them can be justified. I think Water Furnace will likely have a tool on their site to help you calculate your local energy savings, or even perhaps your local electrical utility will have one online.

Answer 2

Are you talking about straight geothermal exchange heat exchange or a geothermal heat pump system? There is a difference, the later has a compressor like an air conditioner has.

Straight geothermal exchange is simply pumping a water mixture through a long set of pipes in the ground and then pump the water straight to a radiator unit. It is limited and simplistic. Ground temperature vary. In the south this could be used for heating a house on cool days, but in general is it just for air conditioning.

Geothermal heat pump is a reversible central air conditioning unit that has a coil in the ground where it is cooler instead of in the hot summer air that normal central air pumps the heat out to. Or warmer in the freezing winter air. The unit could potentially do any amount of heating or cooling with any length of pipe in the ground, dependent that the unit is capable of concentrating heat that well and either pushing it in or out of the house as required (remember I said reversible). The longer the coil in the ground or pond, the better. Don't even think of trying it with less than 500 feet. 2000 feet will always be better. Most mid sized houses will be able to get away with something in between with no trouble.
I understand that for residential housing the prices are getting to the 3000 to 6000 US dollar range in many places in the US.

If you are serious about doing this, then you should either find an installer you trust or buy a book on the subject. I hate to say it, but there isn't that much information available on the internet for free on assembling these systems. I've looked.

Do note that geo thermal system will cut expenses of heating, but doesn't get rid of the cost. Have you thought about solar heating? Solar collectors combined with a large insulated water tank will just about eliminate the price of heating where geothermal will merely reduce the price of heating. It costs less too. Although, it won't do cooling.

Answer 3

Geothermal (ground loop) will depend on your constant ground temperature range and the specific mix of your soil. Water based geothermal (circulating water from wells) are based on the temp of the water and how many gallons you are moving.

This is a complex subject and does not lend itself to quick and easy answers. I just went through this for a home in Oklahoma and got conflicting information from three different companies.

The upfront costs are higher than conventional systems. Your local utility costs are the determining factor. Sometimes the cheapest answer isn't to use geothermal at all. There is some push to use high efficiency dual fuel heat pumps coupled with a 90+% efficient conventional heater to reduce costs.

Something that is often overlooked - heat pump systems require larger air ducts because the air volumn must be higher to offset the lower tempereatures put out by heat pumps. Back pressure from undersized ductwork is a leading cause of premature system failure.

I have some information in a pdf format if you'd like me to send it to you.

Answer 4

Unless you have a geothermal vent under your house that'd be kinda difficult.