Barron Green Team: 6. Geothermal Heat Pumps

If you have read my article, The Mighty Heat Pump, you now know the basics of heat pump operation. A Geothermal Heat Pump is based on the same concept of moving heat from one place to the other, but instead of taking heat from the outside air, we are now pulling it from the earth.

Simply put, a GHP system moves the heat from the earth (or a groundwater source) into the home in the winter, and pulls the heat from the house and discharges it into the ground in the summer. While it may get hot in the summer and freezing in the winter; a few feet below the surface, the ground remains at a relatively constant temperature. This allows you to maintain even heating and cooling in your home throughout the year with minimal back-up heat.

The mechanical installation of a Geothermal Heat Pump is pretty simple, it goes in much like a furnace, just bigger. You can either attach a GHP to a traditional ducted system or apply it to an in-floor radiant system. The sticky part is the ground loop; please CLICK HERE to view ground loop applications.

Now, there is almost always a way to go geothermal on a property, it is generally how much you are willing to pay to get it. For instance, if you have a small lot and want to go GHP, we can drill all the holes (200 ft deep each) and lay all the tubing under the house before it is built. If you want to use an easy rule of thumb here is one easy equation; take your air to air heat pump bid and triple it. Sometimes it is only double, but be ready for triple. I am not trying to scare you away from doing it, but the high cost is just a reality.

While all homes can save money and benefit from a GHP installation; the best application for this type of heating system is the large or giant home. As far as savings go, large or giant homes have the most to gain from a GHP and can minimize their environmental impact by up to 72%. Case studies have shown that a large, 3,400 sq. ft. home can operate on an average of about $34 per month year around. Compare this to an average of $300 per month for a high efficiency furnace system running on propane and you can see how big the pay-offs can get, especially on the giant projects!

There are, of course, many common questions associated with this type of system. I have assembled as many as possible; please CLICK HERE to read Geothermal Heat Pumps: Frequently Asked Questions

Remember, you can call me anytime if you would like to chat about this or anything else that is on your mind.

How efficient is a GHP?
The GHP is one of the most efficient residential heating and cooling systems available today, with heating efficiencies 50 to 70% higher than other heating systems and cooling efficiencies 20 to 40% higher than available air conditioners. That directly translates into savings for you on your utility bills.

Can one system provide both space heating and cooling for my home? And what about heating hot water?
Yes. A GHP can be a combination heating/cooling and hot water heating system. You can change from one mode to another with a simple flick on your indoor thermostat. Using a desuperheater, some GHPs can save you up to 50% on your water-heating bill by preheating tank water.

How does a GHP system heat water for my home?
Using what is called a desuperheater; GHPs turn waste heat to the task of heating hot water. During the summer, when the system is in cooling mode, your hot water is produced free as a byproduct of the thermal process. In winter, with the heating mode, the desuperheater heats a portion of your hot water. Desuperheaters are standard on some units, optional on others. Stand-alone systems that will heat water all year around can be purchased.

How much space does a GHP unit require?
Most of a GHP installation is underground. Inside the house, the heat pump units are about the same size as a traditional heating and cooling unit.

How long will my GHP system last?
GHPs are durable and highly reliable. The GHP contains fewer mechanical components, and all components are either buried in the ground or located inside the home, which protects them from outside conditions. The underground pipe carries up to a 50-year warranty.

How noisy is the GHP unit?
GHPs are very quiet, providing a pleasant environment inside & outside of the home. GHPs have no noisy fan units to disturb outdoor activities, on or near the patio.

How safe are GHPs?
GHP systems are safe and protected. With no exposed equipment outdoors, children or pets cannot injure themselves or damage exterior units. GHPs have no open flame, flammable fuel or potentially dangerous fuel storage tanks.

What about comfort?
A GHP system moves warm air (90-105(F) throughout your home or business via standard ductwork. An even comfort level is created because the warm air is moved in slightly higher volumes and saturates the building with warmth more evenly. This helps even out hot or colds spots and eliminates the cold air blasts common with fossil fuel furnaces.

How effective is this underground system?
The buried pipe, or ground loop, is the most recent technical advancement in heat pump technology. Recently, new heat pump designs and improved buried pipe materials have been combined to make GHP systems the most efficient heating and cooling systems available.

Are GHP systems guaranteed?
Nearly all GHP system manufacturers offer a warranty for major components that is equivalent to the warranties for conventional heating and cooling systems. Manufacturers of plastic pipe used for ground loops warrant their products for 50 years.

Can these systems be used for commercial, industrial, or apartment requirements?
Yes! Many GHP systems are being installed using a multitude of systems hooked up to an array of buried vertical or horizontal loops. This simplifies zone control and internal load balancing.

Savings / Costs:

How will I save money with a GHP?
GHPs save money, both in operating costs and maintenance costs. Depending on installation; investments can be recouped in as little as three years. There is a positive cash flow, since the energy savings usually exceeds payment on the system.

How much does a GHP cost?
The initial investment for a GHP system is greater than that of a conventional system. However, when you consider the operating costs of a geothermal heating, cooling, and water heating system, energy savings quickly offset the initial difference in purchase price.

What other costs are there besides the GHP system?
You can expect an installation charge for any electrical work, ductwork, water hook-up, and other provisions or adaptations to your home that are required. Your installer can estimate these costs in advance.

How would increased use of GHP systems affect electricity cost and availability?
The reduced peak load requirements would allow utilities to serve more customers and to lower fixed costs per customer, thus offsetting some increased variable costs. This would result in less cost per kilowatt, since fixed investment for new capacity is high.

Installation:

Are GHP systems difficult to install?
Most units are easy to install, especially when they are replacing another forced-air system. This is known as a retrofit. GHPs can be installed in areas unsuitable for fossil fuel furnaces because there is no combustion and thus no need to vent exhaust fumes. Ductwork must be installed in homes without an existing air distribution system.

Can I install a ground source heat exchanger myself?
It's not recommended. Thermal fusion of the pipe, drilling and trenching are procedures best handled by licensed professionals. Nonprofessional installations may result in less than optimum performance, which could cancel out anticipated savings

How far apart are trenches and vertical boreholes spaced?
Trenches are spaced four to five feet apart while boreholes are spaced five to fifteen feet apart.

How long does it take to install a horizontal system?
This depends on soil conditions, length and depth of pipe, and equipment required. A typical installation can be completed in two or three days.

How long does it take to install a vertical system?
With the vertical installation, time varies with conditions on the site such as type and depth of the overburden, type and hardness of the bedrock, and the presence of aquifers. Typical drilling times are one or two days; total installation can usually be accomplished in three days.

What are the advantages and disadvantages of the horizontal and vertical installations, respectively?
Horizontal installations are simpler, requiring lower-cost equipment. However, they require longer lengths of pipe due to seasonal variations in soil temperature and moisture content. Since a horizontal heat exchanger is laid out in trenches, a larger area is usually required than for a vertical system. If regional soil conditions include extensive hard rock, a vertical installation may be the only available choice. Vertical installations tend to be more expensive due to the increased cost of drilling versus trenching, but since the heat exchanger is buried deeper than with a horizontal system, vertical systems are usually more efficient and can get by with less total pipe.

Is it advisable to install a GHP system large enough to handle my total heating needs?
GHP systems are generally sized to meet all your cooling needs. Depending on heating needs, a GHP system usually supplies 80-100 percent of your design heating load. Sizing the system to handle your entire heating needs may result in slightly lower heating costs, but the savings may not offset the added total of the larger system. Special consideration should be given to systems in the north where multiple capacity units should be considered to handle the large variation between heating and cooling loads.

Environment / Climate:

How do GHPs protect the environment?
GHP systems conserve natural resources by providing climate control very efficiently-thus also lowering emissions. GHPs also minimize ozone layer destruction by using factory-sealed refrigeration systems, which will seldom or never have to be recharged.

What are the environmental benefits of GHP systems?
Currently installed systems are making a huge difference in our environment! The systems are eliminating more than three million tons of carbon dioxide and is equivalent of taking 650,000 automobiles off the road. GHP systems conserve energy and, because they move heat that already exists rather than burning something to create heat; they reduce the amount of toxic emissions in the atmosphere. They use renewable energy from the sun, and because the system doesn't rely on outside air, it keeps the air inside of buildings cleaner and free from pollens, outdoor pollutants, mold spores, and other allergens.

Do soil freezing conditions create any problems?
Not if a system is properly designed and installed. The three to four foot depths allow the sun to melt the frozen soil during the summer. Adequate length per ton capacity prevents objectionable soil movement.

Does this mean that in extremely cold climates additional heat sources are necessary?
All systems require an emergency back up. Heat pumps can provide all the heat necessary even in the coldest weather. An economic analysis by your contractor should dictate what portion of the heat should be provided by the heat pump and what portion by auxiliary means.

Concerning Your Home:

Will my existing ductwork function with this system?
Yes, in most cases.

Will an underground loop affect my lawn or landscape?
No. Research has shown that loops have no adverse effects on grass, trees, or shrubs. Most horizontal installations require trenches about six inches wide. Temporary bare areas can be restored with grass seed or sod. Vertical loops require little space and do not damage lawns significantly.

My yard contains many shade trees. Will this affect ground temperature and my ability to use it as an energy source?
Not at all. The system is installed deep enough that it utilizes constant ground temperature.

Can a GHP system be added to my fossil fuel furnace?
Yes. Called dual systems, they can easily be added to existing furnaces for those wishing to have a dual-fuel heating system. Dual-fuel systems use the GHP system as the main heating source, and a fossil fuel furnace as a supplement in extremely cold weather should additional heat be needed.

Will I have to add insulation to my home if I install one of these systems?
Ground source heat pump systems will reduce your heating and cooling costs regardless of how well your home is insulated. However, insulating and weatherizing are key factors in gaining the maximum amount of savings from any type of heating and cooling system.