Geothermal works differently than conventional heat pumps that use the outdoor air as their heat source or heat sink. Geothermal systems don’t have to work as hard (which means they use less energy) because they draw heat from a source whose temperature is moderate. The temperature of the ground or groundwater a few feet beneath the Earth’s surface remains relatively constant throughout the year, even though the outdoor air temperature may fluctuate greatly with the change of seasons.At a depth of approximately six feet, for example, the temperature of soil in most of the world’s regions remains stable between 45 degrees F and 70 degrees F. This is why well water drawn from below ground tastes so cool even on the hottest summer days.

In winter, it’s much easier to capture heat from the soil at a moderate 50 degrees F than from the atmosphere when the air temperature is below zero. This is also why Geothermal systems encounter no difficulty blowing comfortable warm air through a home’s ventilation system, even when the outdoor air temperature is extremely cold. Conversely, in summer, the relatively cool ground absorbs a home’s waste heat more readily than the warm outdoor air.

Studies show that approximately 70 percent of the energy used in a Geothermal heating and cooling system is renewable energy from the ground. The remainder is clean, electrical energy which is employed to concentrate heat and transport it from one location to another. In winter, the ground soaks up solar energy and provides a barrier to cold air. In summer, the ground heats up more slowly than the outside air.

This can be highly economical, especially if the home already has a Geothermal system, hence a ground loop, in place.

One economical way to obtain a portion of domestic hot water is the addition of a desuperheater to the geothermal unit. A desuperheater is a small, auxiliary heat exchanger that uses superheated gases from the heat pump’s compressor to heat water. This hot water then circulates through a pipe to the home’s water heater tank. In summer, when the Geothermal system is in the cooling mode, the desuperheater merely uses excess heat that would otherwise be expelled to the loop. When the Geothermal unit is running frequently, homeowners can obtain all of their hot water in this manner virtually for free. A conventional water heater meets household hot water needs in winter if the desuperheater isn’t producing enough and in spring and fall when the Geothermal system may not be operating at all.

Because geothermal systems heat water so efficiently, many manufacturers today are also offering triple function Geothermal systems. Triple function systems provide heating, cooling, and hot water. They use a separate heat exchanger to meet all of a household’s hot water needs.

The geothermal heat pump is packaged in a single cabinet and includes the compressor, loop-to-refrigerant heat exchanger, and controls. Systems that distribute heat using ducted air also contain the air handler, duct fan, filter, refrigerant-to-air heat exchanger, and condensate removal system for air conditioning. For home installations, the geothermal heat pump cabinet is usually located in a basement, attic, or closet. In commercial installations, it may be hung above a suspended ceiling or installed as a self-contained console.

Most residential geothermal systems use conventional ductwork to distribute hot or cold air and to provide humidity control. (A few systems use water-to-water heat pumps with one or more fan-coil units, baseboard radiators, or under-floor circulating pipes.) Properly sized, constructed, and sealed ducts are essential to maintain system efficiency. Ducts must be well insulated and, whenever possible, located inside of the building’s thermal envelope (conditioned space). Geothermal heating and cooling systems for large commercial buildings, such as schools and offices, often use a different arrangement. Multiple heat pumps (perhaps one for each classroom or office) are attached to the same earth connection by a loop inside the building. This way, each area of the building can be individually controlled. The heat pumps on the sunny side of the building may provide cooling while those on the shady side are providing heat. This arrangement is very economical, as heat is merely being transferred from one area of the building to another, with the earth connection serving as the heat source or heat sink only for the difference between the building’s heating and cooling needs.

Many residential-sized systems installed today are equipped with desuperheaters to provide domestic hot water when the system is providing heat or air conditioning. The desuperheater is a small auxiliary heat exchanger at the compressor outlet. It transfers excess heat from the compressed gas to a water line that circulates water to the house’s hot water tank. In summer, when the air conditioning runs frequently, a desuperheater may provide all the hot water needed by a household. It can provide four to eight gallons of hot water per ton of cooling capacity each hour it operates. A desuperheater provides less hot water during the winter, and none during the spring and fall when the system is not operating. Because the heat pump is so much more efficient than other means of water heating, manufacturers are beginning to offer “triple function,” “full condensing,” or “full demand” systems that use a separate heat exchanger to meet all of a household hot water needs. These units cost-effectively provide hot water as quickly as any competing system.

EfficiencyGeothermal heat pumps are much more efficient than air source heat pumps because earth temperatures are much more uniform through the year than air temperatures. Not only are earth temperatures more constant, but also the range of temperatures in groundwater is rather small in the United States, varying from the upper 40s to upper 70s nationwide. To further improve efficiency, many manufacturers use variable-speed, electronically-controlled motors on the duct system fans. Depending on unit size, manufacturers may opt for reciprocating, inertia, rotary, or scroll compressors — all of which are hermetically sealed and mounted in the indoor cabinet. Some advanced heat pumps feature two-speed or variable speed operation while others feature dual compressors to vary output capacity and match loads.

The Benefits Speak for Themselves

Tens of thousands of homes are being built or retrofitted with geothermal heating and cooling systems every year, because of the advantages these systems offer: economical operation, noise reduction, and product quality. Initially reserved for the most expensive homes, now these systems have become affordable options for thousands of low and moderate income housing units because of the system’s low life-cycle costs compared to all other alternatives in almost every region of the country. According to the Environmental Protection Agency, geo-exchange systems save homeowners more than 30-70% in heating costs 20-50% in cooling compared to conventional systems.

There are four basic types of ground loop systems. Three of these—horizontal, vertical, and pond/lake—are closed-loop systems. The fourth type of system is the open-loop option

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• Deciding on which one of these is best for your home or building depends on the climate, soil conditions, available land, and local installation costs at the site.
• All 4 of these approaches can be used for both residential and commercial building applications.

This type of installation is generally most cost-effective for residential installations, particularly for new construction where sufficient land is available. It requires trenches at least four feet deep. The most common layouts either use two pipes, one buried at six feet, and the other at four feet, or two pipes placed side-by-side at five feet in the ground in a two-foot wide trench. The Slinky™ method of looping pipe allows more pipe in a shorter trench, which cuts down on installation costs and makes horizontal installation possible in areas it would not be with conventional horizontal applications.

Large commercial buildings and schools often use vertical systems because the land area required for horizontal loops would be prohibitive. Vertical loops are also used where the soil is too shallow for trenching, and they minimize the disturbance to existing landscaping. For a vertical system, holes (approximately four inches in diameter) are drilled about 20 feet apart and 100–400 feet deep. Into these holes go two pipes that are connected at the bottom with a U-bend to form a loop. The vertical loops are connected with horizontal pipe (i.e., manifold), placed in trenches, and connected to the heat pump in the building.

If the site has an adequate water body, this may be the lowest cost option. A supply line pipe is run underground from the building to the water and coiled into circles at least eight feet under the surface to prevent freezing. The coils should only be placed in a water source that meets minimum volume, depth, and quality criteria.

This type of system uses well or surface body water as the heat exchange fluid that circulates directly through the GHP system. Once it has circulated through the system, the water returns to the ground through the well, a recharge well, or surface discharge. This option is obviously practical only where there is an adequate supply of relatively clean water, and all local codes and regulations regarding groundwater discharge are met.

A radiant hydronic heating system circulates warm water (typically 30-40 degrees) through special tubing in or beneath floors to distribute heat. Radiant energy warms the surfaces of all objects which are in direct line of sight, including all floors, walls, furniture, and people which can be ‘seen’ by the floor.

Radiant systems provide the inverse of conventional space heating patterns: they provide warm floors and cool ceilings, resulting in greater comfort and energy savings. It does not rely on ducting, furnaces, fans or blowers and therefore the system is virtually noiseless due to the lack of air movement.

Geothermal systems are efficient, environmentally-sensitive, comfortable, and economical. Operating savings often provide paybacks of considerably less than five years — sometimes less than two years. The key is that geothermal heat pumps use electricity to move heat, not to generate it by the burning fuel or using electric resistance elements. Indeed, the U.S. EPA has found that no other technology with more favorable operating efficiencies and economics than emerging geothermal heat and cooling systems.

The U.S. Environmental Protection Agency has concluded that well-designed and properly installed high-efficiency geothermal heat pump systems produce less environmental harm than any other alternative space conditioning technology currently available. On a full fuel cycle basis, emerging geothermal systems are the most efficient technology available, with the lowest CO2 emissions for minimum greenhouse warming impact. Overall, the EPA found emerging geothermal heating and cooling systems to have the lowest environmental cost of all technologies analyzed — including air-source heat pumps and natural gas furnaces

No existing space conditioning technology offers greater comfort, economy, or environmental benefits than the geothermal heat and cooling systems now available for residential and commercial installations. Over 250,000 installations are in place in the United States today, and the number is rapidly increasing. More than 95 percent of all geothermal heat and cooling customers are completely satisfied with their systems.

Piping
Special thick but flexible piping is used in geothermal installations. The most commonly used type of pipe is high quality, high-density polyethylene. All below-grade connections must be made by heat fusing, which yields connections stronger than the pipe itself and without any threads. All installations must be purged to remove construction debris, flushed to remove air, and pressure tested (to 100 PSI) before backfilling or grouting. Ground Loop guarantees their loops for twenty years.Sizing
Numerous studies have shown that residential heat pumps are often sized too large. Heat pumps that are too large waste energy and do not provide proper humidity control. Where heating needs are much greater than cooling needs, advanced heat pumps (see above) can improve Summer comfort. Ground Loop uses detailed information about your home as well as their experience to recommend the right type of unit and loops for your home.Purchase and Installation
As in the case of all major decisions, choosing a geothermal heating and cooling system requires some careful consideration to ensure that the consumer receives the highest quality system and installation.The Geothermal Heat Pump Consortium (GHPC) offers the following Guidelines:Ratings and certification:
The Air-Conditioning and Refrigeration Institute (ARI) is a non-profit organization that certifies the performance of residential and small commercial geothermal equipment. For equipment classes rated by ARI, the GHPC suggests that consumers look for the ARI seal. (ARI does not rate large, commercial geothermal equipment greater than 135,000 Btu/hr).Warrantees:
Manufacturers’ terms of warranty vary. To assure a high-quality installation, consumers should seek a performance guarantee on the installed system, as opposed to coverage limited to the heat pump itself.Sizing:
Numerous studies have shown that heat pumps are often sized too large. For maximum efficiency, heating and cooling loads should be carefully determined. The actual unit size should be within 15 percent of the calculated load. Heat pumps that are too large waste energy and do not provide proper humidity control. For an excellent article on sizing,

Design:
Residential system design is straight-forward, but the most satisfactory results are obtained with experienced contractors. Aspects to consider include careful duct design and installation in which ducts are kept in conditioned spaces and are permanently sealed; high-quality insulation, glazing, and other envelope features to minimize loads and reduce air infiltration; and careful matching of the heat pump and earth connection capacity to building load. It may be advantageous to specify two-speed or variable speed systems where heating requirements are much greater than cooling, to assure good humidity control. Finally, the contractor should examine ways to use the geothermal system to provide hot water.

Installation:
Proper installation is a key to success. The GHPC recommends that consumers employ experienced contractors who will provide the names of customers with comparable systems.Dealing with experienced professionals who size and install ground loops is essential. It is critical that the installation prescriptions of the International Ground Source Heat Pump Association (IGSHPA) are followed.

Benefits of Geothermal.

• Energy savings
• Environmental savings
• Protection from energy cost increases
• Scaled application delivers earlier ROI
• Reliable, low maintenance, long life
• Versatile and works anywhere
• Quiet
• Efficient
• Comfort
• Third-party verifications

One system, many uses
Whether you live in an urban location or a remote area, you can use the same unit for heating and cooling of living space, domestic water or swimming pools. Direct Energy’s products provide the simple and convenient solution to create a comfortable home environment for your family and guests all year around.Quiet comfort in your home
You can benefit from stable and comfortable temperatures all year long without the noise of typical air conditioners or heat pumps. During winter, you will experience warmth without the hot blasts of gas furnaces; when cooling, you will benefit from crisp, dehumidified air.Small and convenient
Direct Energy has a small geothermal heat pump and earth loop footprint, making it convenient to install and easy to fit in your home and yard, no matter how constrained the space.Technically simple and reliable
Because of its unique mechanical simplicity, the system offers greater reliability, minimal maintenance, and long useful life.Works anywhere
From Australia, Sitka-Alaska, or Siauliai-Lithuania, Direct Energy’s system is designed to work anywhere seamlessly, regardless of your climate conditions, always quietly delivering comfort, savings and the performance you desire in your home.