Geothermal Heat Pump

Introduction to Geothermal Systems

Homeowners in most regions of North America are enjoying unsurpassed levels of comfort and significantly reduced energy costs by using leading edge geothermal central heating and cooling. This technology relies primarily on the earth's natural thermal energy, "a renewable resource", to heat or cool a house or multifamily dwelling. The only additional energy geothermal systems require is a minimal amount of electricity they employ to concentrate the natural thermal energy which, Mother Nature provides and to circulate high quality, central heating and cooling throughout the home.

Homeowners who use Geothermal systems rate them as superior to other conventional heating and cooling systems because of their ability to deliver comfortably warm air and/or hydronic in-floor heating, even on the coldest winter days and because of their extraordinarily low operating costs. Since a Geothermal System is reversible, they offer the added benefit of central A/C and dehumidification. As an additional benefit, geothermal systems can provide inexpensive domestic hot water, either to supplement or replace entirely the output of a conventional, domestic water heater.

Geothermal heating and cooling is cost effective because it uses renewable underground energy, in an extremely efficient manner. In the heating season, a Geothermal System will absorb approximately 75% of the energy from the ground and the remaining 25% would come from the electrical grid. For this reason, GSHP Systems are considered, very environmentally friendly and many government agencies endorse geothermal technologies. Geothermal Systems are the most energy efficient heating and cooling systems available.

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How Geothermal Systems Work

Each year, the sun supplies us with about 500 times more energy than we could possibly use. The Earth absorbs solar energy and retains it below the frost level, thereby maintaining a constant underground temperature, depending on geographic location. The underground temperature will be directly related to the average air temperature above ground. For example, the below frost level underground temperature in Toronto will be approximately 50 degrees F or 10 degrees C. Working with a customized underground loop or open well water system, a complete geothermal system utilizes this constant temperature to exchange energy between your home/space and the Earth, as needed for heating and cooling. Geothermal Systems dramatically reduce CO2 emissions, as compared to fossil fuel burning systems, which add to the CO2 emission problem. The specific amount of CO2 reduction would be based on the electrical fuel grid in a given country or region. Since a Geothermal Systems do not burn fossil fuels, a chimney is not needed in the home.

In the heating season, the open or closed loop fluid/well water is circulated the through the system to absorb heat from the earth/water, and then that heat is transferred to your home. The geothermal system processes the extracted heat and compresses it to a higher temperature, which is then distributed throughout the home using traditional duct systems.

In the air conditioning season, the heating process is reversed, and the geothermal unit absorbs heat from inside the home and sends it back to the cooler earth. The energy then re-warms the Earth for the next heating season.

By using the natural, constant temperature of the earth or a water source, a geothermal system is the most efficient method available to provide year round comfort and high efficiency performance. There are many basic energy sources available to earth energy systems or ground-source heat pump (GSHP) customers. The most common are, "Closed Vertical Loop", "Closed Horizontal Loop", "Closed Pond, River or Lake Loop" or and "Open Well" System. You are standing on a free energy source. The secret is, how we economically take advantage of these energy sources available to us.

It should be noted that a geothermal heat pump is simply and vapor compression based, energy transfer mechanism and in that, they can be used to heat or cool and myriad of air and water (hydronic) elements and with then right system you can simultaneously heat and cool. Eg. heat your pool while using the normally wasted air conditioning process heat, etc.

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AHRI (Air-Conditioning, Heating & Refrigeration Institute)

An AHRI Certification label tells the consumer that the product (heat pump) that you are assessing or have chosen have gone through a rigorous third party verification and certification process, qualifying the manufacturers efficiency & specification numbers, in a sense leveling the "product to product" playing field. AHRI is a primary 3rd party certification organization within the residential and commercial, air conditioning, heating, water heating and commercial refrigeration equipment market in North America.

AHRI's mission is to ensure human comfort, productivity, and safety, while practicing environmental stewardship is the mission of the Air-Conditioning, Heating, and Refrigeration Institute (AHRI). The AHRI certification program, standards, advocacy, and other activities help save energy, improve productivity, and ensure a better environment. Geoflex products are AHRI certified.

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Energy Star®

Earning the ENERGY STAR® means products have generally been third party tested and meet strict energy efficiency guidelines. The Energy Star® label is only applied to products which have been through the rigorous Energy Star process. Energy Star is a certification process designed to encourage the highest efficiency equipment available. By choosing ENERGY STAR qualified heating and cooling equipment and taking steps to optimize its performance, you can enhance the comfort of your home while saving energy. Saving energy helps you save money on utility bills and protect the environment by reducing greenhouse gas emissions in the fight against climate change.

Geothermal heat pumps (GHP's) are among the most efficient and comfortable heating and cooling technologies currently available, because they use the earth’s natural heat to provide heating, cooling, and often, water heating.

As of December 1, 2009 homeowners in the United States who install ENERGY STAR qualified geothermal heat pumps are eligible for a 30% federal tax credit. There is also a federal grant available in Canada for Geothermal Heat Pumps. You should check as there could also be provincial and power provider grants available, depending on your specified region.

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Technology

An earth energy installation or ground-source heat pump (GSHP) is one of the most efficient means available to provide space heating/cooling for homes and offices, in virtually all regions throughout the world. It transfers the heat located immediately under the earth's surface (or in a body of water) into a building in winter, using the same principle as a refrigerator that extracts heat from food and rejects into a kitchen. A heat pump takes heat from its source at a low temperature and discharges it at a higher temperature, allowing the unit to supply more heat than the equivalent energy supplied to the heat pump.

Many people are familiar with air-to-air heat pumps, which use outdoor air as the source of heat. These units are well suited for moderate climates, but they do not operate efficiently when the outdoor temperature drops below -10 degrees C and there is little "heat" left in the air to extract. It is more difficult to extract or reject heat to air because of its low density. A Liquid Energy Source will always outperform an "air to air" system, even given the same operating temperatures. Don't be confused, when calculating efficiency geothermal heat pumps are measured based on steady state points of measure, as they utilized constant underground temperatures. Air to air heat pumps must be measured within seasonal factors, as the air temperature is constantly changing and steady state would not offer and appropriate comparable measure.

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Environmental Benefits

Governments and energy planners prefer GSHP technology because it is an environmentally benign technology, with no emissions or harmful exhaust. The GSHP industry was the first to move away from damaging CFC's (chlorofluorocarbons). Since geothermal systems take 70% of the energy they use from the earth, the environmental benefits are obvious. Although GSHP units require electricity to operate the components, a high COP means that GSHP systems provide a significant reduction in the level of CO2, SO2 and N0x emissions (all linked with the issue of greenhouse gas emissions and global warming).

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Renewable Energy Factor

Although to date, there is no such rating as a Renewable Energy Factor (REF), but if there was, Geothermal Heat Pump Systems would score well beyond any other environmentally friendly or encouraging technology. As an example, in the heating mode, a Geothermal System, absorbs 70 to 75% of the heat energy from the earth, utilizing various earth coupled technologies and through an “energy transfer” geothermal heat pump, adds 25 to 30% of the energy to transfer all energy to the space. Therefore the COP would be 3.3 to 4 heat energy output for every 1 unit of energy input, the renewable energy factor is obvious. Geothermal Systems do not compete with other technologies but are actually commonly integrated with them. To compare technologies consider the following, Wind and Solar technologies offer obvious renewable opportunities, when the sun is shining and the wind is blowing, when a geothermal system offers 75% of the energy from the earth 100% of the time.

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Durability

Geothermal Systems last longer than conventional systems since they are self-contained, sitting in the place where a standard furnace would sit, completely indoors. Therefore, a Geothermal System is sheltered from extreme outside weather conditions. It is not uncommon to see geothermal system lasts well beyond 20 years. The system has no noisy, rattling parts to disturb your family. Also, since they are completely inside your home, you will eliminate any noise complaints from your neighbors. A Geothermal System has few moving parts subject to breakdown, helping to keep maintenance to a minimum. With a properly maintained system, the homeowner will enjoy many years of unencumbered comfort. Simple maintenance would include, changing the filter and yearly oiling of the fan motor, as with most conventional furnace and A/C Systems. If an open well system is used the maintenance would include, inspection and maintenance of the well water supply.

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General Cost

Earth energy heat pumps provide one of the lowest life-cycle costs for heating and cooling in North America (i.e. the total cost for initial installation and annual operating costs, will be lower than the comparable cost for a conventional heating/cooling system). Earth energy technology is different from a gas or an oil furnace, and it is a long-term investment in comfort and home equity. If a homeowner requests regular servicing, this could easily be arranged through a service contract. Proper performance reflects the quality of installation. Consumers should insist a reputable geothermal contractor install the system. The national installation standard in Canada (CSA C448) addresses aspects of design and installation, but many important points are left to the discretion of the contractor and/or manufacturer. With a bit of homework by the homeowner, the design and installation of an earth energy unit will provide many years of trouble-free operation and lower costs.

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Comfort Advantages

A GSHP system warms air in smaller increases over a longer period of time, as compared to the "burst" of a combustion oil or gas furnace. As a result, homeowners notice a stable level of heat with no peaks or troughs, less drafts, etc.

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Terminology

Due to the large demand for GSHP as cooling devices in the United States, the earth energy industry uses the term "ton" to describe a unit that will provide approximately 12,000 BTU's of cooling or heating capacity. The cooling capacity on average, for a typical 2,000 square-foot new residence would require a 4-ton unit for sufficient heat, depending on the location.

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Co-efficient of Performance (COP)

The major advantage of a GSHP system is that the heat obtained from the ground (via the condenser) is much greater than the electrical energy that is required to drive the various components of the system. The efficiency of a unit is the ratio of heat energy provided versus the electrical energy consumed to obtain that heat, and it is called its "Coefficient of Performance" (COP). As an example, under the "Energy Efficiency Act" in Canada all GSHP units that are sold must exceed a COP of 3.0 (i.e. for every kilowatt of electricity needed to operate the system, the GSHP provides three kilowatts of heat energy).

With a COP of 3.0, the cost of heating would be one-third (i.e. two-thirds less) of the cost to operate an electric resistance heating system, such as baseboards or electric furnace. With a COP of 4.0, the savings can be as much as three-quarters off the price of electric heating, with an EER at 14 the cooling costs will also be reduced dramatically. As earth energy technologies and techniques improve and as the COP increases, the operating savings also increase.

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Electrical Efficiency Ratio (EER)

EER is the "Steady State", "energy efficiency ratio" rating when operating in the cooling mode. EER ratings are arrived at by, dividing the cooling output of the Geothermal Heat Pumps (in Btu/Hour) by, the power input (in Watts). For example an EER of 14 would mean that you would receive 60,000 BTU's for the cost of 4286 watts or 4.286 kW. If your electrical rate is $.06/kW, you would pay (6X4.286) to run a 5 ton, 60,000 BTU forced air cooling system. Fuel prices and electrical prices vary dramatically throughout North America and Europe. You may have come across a SEER rating. This is an acronym for Seasonal Energy Efficiency Ratio, which is commonly used to calculate the general efficiency of a conventional "air to air" heat pump or standard air conditioner. A Geothermal heat pumps efficiency does not fluctuate because of outdoor air temperatures, as with "air to air" systems, therefore the "steady state" EER rating is commonly used by the industry. Do not be confused the two ratings are not comparable.

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Heat Loss/Gain

A very important first step in the design of a GSHP installation is to determine how much heat or cooling is required to satisfy your comfort level. There are standards to calculate the heat loss and heat gain throughout the world The national Canadian installation standard for residential earth energy units (CSA C448) states that the heat loss must be calculated in accordance with a recognized heat loss program. This method needs to establish, the insulation levels of all walls, ceilings and windows, the number of occupants, your geographic location and soil type, and many other factors, to determine the total annual heat loss in British Thermal Units (BTU) or kilowatts (kW). It will also calculate the heat gain, which is used to determine the cooling load for summer (all units will generally provide sufficient cooling, if the unit is large enough to provide sufficient heat). With this final heat loss, the installed unit will match your specific demand.

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Ventilation Requirement

A very important first step in the design of a GSHP installation is to determine how much heat or cooling is required to satisfy your comfort level. As the heat loss and heat gain is calculated, it is equally important to include all ventilation requirements. This is especially important in newer energy efficient homes, as the ventilation requirement can affect the heat loss/gain numbers in a dramatic way. As mentioned in the heat loss section of this tutorial, there are standards when it comes to the required amount of ventilation for a given space, depending on several factors including occupancy. Suffice to say that this must be taken into consideration when doping the heat loss and heat gain.

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Balance Point

The outdoor temperature at which a GSHP system can fully satisfy the indoor heating requirement is referred to as the balance point, and is usually -10oC in most regions of Canada and the Northern U.S., specifically. At outdoor air temperatures above this balance point, the GSHP cycles on and off to satisfy the demand for heat indoors. At temperatures below this point, the GSHP unit runs almost continuously, and will also turn on the auxiliary heater (called second stage heat) to meet the demand. In the case where a large residence is concerned, it is common for the GSHP heat pump to be sized to cover 100% of the heat loss. Normally a larger home would require a "Two Stage" or "Dual Staged" (two compressor sections in one unitary system) unit to accomplish this goal. A two-stage system will run at two separate speeds while maintaining the same COP on either speed. This differs on a two speed system in that, a "Two Speed System" will drop the COP when operating in high speed mode, whereas a Two Stage System will not. In a Two Stage System the second compressor becomes the second stage heat/cool. The secondary benefit to a Two Staged System is that the customer can use both stages to cool when the outdoor temperatures increases dramatically in a short period of time, as is common in many locations, globally.

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Auxiliary Back-up or Emergency Heat

When the outdoor air temperature drops below the design balance point, the GSHP unit cannot meet the full heating demand inside the house (for units sized to 100% of heat loss, this is not an issue). The difference in heat demand is provided by the supplementary or auxiliary heat source, usually an electric resistance element or in some cases a hydronic hot water coil, positioned in the unit's plenum. Like a baseboard heater, the COP of an "electric" auxiliary heater is 1.0, so excessive use of backup heat decreases the overall efficiency of the GSHP system and increases operating costs for the homeowner. A Hydronic fan coil can be employed where a customer has the opportunity to use hot water directly from their domestic hot water tank to help boost the heat output at times of high demand. A hydronic hot water coil would only be used when the customer has a low operating cost (fuel type is the key), quick response, hot water tank available. Using a GSHP complete with a Hydronic Hot Water Coil as backup is commonly referred to as a Dual Fuel System. An electric Hot water tank would not be used in this application, except where a Demand Hot Water Option has been built into the GSHP. See Hot water Options

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Sizing - Water to Air (Forced Air) GSHP

A Water to Air GSHP is commonly referred to as a Forced Air system or visa versa. Depending on the climate, for an optimal design, forced air GSHP units are not generally designed to meet 100% of the calculated heat loss of a building and generally do use an auxiliary electric or hydronic coil, heating source for backup and for emergencies. In a situation where the heating and cooling loads are reasonably balanced, approximately 97% of a home's heat load can be met by a GSHP unit that is sized to 70% of the heat loss, with the remaining 3% of load is supplied by an auxiliary method, commonly built into the heat pump as an option. You should note that a homes heat loss is directly related to outdoor temperatures. Therefore even if the system is sized at 70% of the heat loss, the temperature may only drop for a short duration. Over sizing can result in control and operational problems in the cooling mode as well as short cycling in the heating mode and the installed cost will increase significantly for little or in some cases even lower operational savings. In a retro-fit application, over sizing of a Geothermal forced air system can also cause issues where the ducting will be over sized and the cost will increase without the benefit. Conversely, under-sizing can lower the installed cost, but the additional length of time that the GSHP unit will operate will place excessive demand on many components and may result in unacceptable chill. Although the Canadian CSA standard for installations says that 65% of the heat loss is the minimum, the industry has moved to a sizing level of 95% of the run time, which is different type of calculation but much more accurate. In short, an optimally designed system is the best way to receive and maintain the lowest operating cost, with the best capitol cost.

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Sizing - Water to Water (Hydronic) GSHP

A Water to Water GSHP is commonly referred to as a Hydronic system or visa versa. Although Water to Air or forced air systems are commonly sized to cover only a portion of the heat loss, a water to water (Hydronic) system is generally sized to cover the complete heat loss, unless a back-up system is included in the design. Hydronic systems are commonly used to in conjunction with one or two buffer tanks, which feed heated water to an in-floor or air handler and chilled water to an air handler. Water to Water (Hydronic) GSHP systems offer various zoning opportunities because of the delivery system. For cost reasons, basic insulated hot water tanks are commonly used as buffer tanks but should offer 2 ports for water entry and two ports for water exit. With appropriate heat exchangers a Water to Water, can and commonly are used to heat indoor or outdoor swimming pools.

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Power Supply Considerations

GSHP units do not generally need any different kind of power supply. However, It should be noted that the power supply should be considered when employing GSHP Systems. As it is common in a residential application to use single phase power and since a GSHP unit uses a motor, the initial power up, which is reflected as LRA (Locked Rotor Amps) needs consideration before installing a system. A motor will normally cause a higher than operating initial draw for a split second, upon start-up and the service to the house could be an issue. Most power providers have basic "conditions of service" which will say that if you have a higher than 100A LRA, (Locked Rotor Amp) rating, which is the start-up rating, they need to be notified to be sure that the pre-existing service, not just the panel, is sufficient. The LRA is commonly available with most heat pump specifications and always available on the name plate data. In some cases a soft start system can be factory installed to reduce the LRA rating, to avoid any potential affect with this issue. For example a 6 ton GSHP can have a LRA rating of up to 150A but if a soft start system is installed, the LRA can drop by as much as 100 amps. As a matter of fact the LRA should be a consideration with any motor, as motors carry an inductive power load. If you presently have a GSHP and you notice the dimming of lights when the system is starting, then you likely already have an issue. In this case, you will need to have the problem resolved before your unit is further damaged. It should also be noted that a GSHP, as with any electrical device that is hard wired to your home, should be approved by the authority having jurisdiction in your region.

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Hot Water Options

Desuperheaters and Partial Hot Water (PHW) are the most popular hot water option, usually adding less than $1,000 to the total installation, but reducing approximately 60% to 70% of domestic hot water heating cost to an average household. This option is automatically activated to heat hot water whenever the system is operating either in the heating, cooling or "Demand Hot Water" mode. A desuperheater can be set up as "low" or "high" priority, depending on whether the homeowner wants the ground heat diverted to the domestic hot water first (thereby turning on the auxiliary backup heater) or to heat water only after the space heating requirement has been satisfied. In the cooling mode the Desuperheater will take hot water off the system for domestic hot water use, instead of rejecting the heat to the ground loop which essentially causes free hot water.

On Demand Hot Water Systems (ODHW) are most commonly used to heat a hydronic in-floor or a zoned hydronic hot water air coil heating system. With a specifically designed water coil, an On Demand Hot Water System can also be used to heat an indoor or outdoor swimming pool on demand. The difference between a Desuperheater (PHW) and a On Demand Hot Water (ODHW) system is that the Desuperheater will heat a small portion of the domestic hot water, only when the other modes are operating. An On Demand Hot Water System will turn on simply to make hot water with no other modes operating and the amount of hot water will be based on the size of the main systems compressor. An On Demand Hot Water System tied directly to a hot water tank, would be considered a "Quick Response" system. An On Demand Hot Water Option can be added to a water to air or a water to water heat pump. Please on previous links for either type to see a typical installation of installation drawings..

On Demand Hot Water, plus Systems (ODHW+) complete with the forth mode is not commonly available and is exclusively manufactured by Geoflex. The ODHW+ system goes one step beyond a standard ODHW system. This option is employed to allow for your hot to be heated by the air conditioning process heat whenever both and A/C and ODHW are calling. In this mode the system will essentially heat your hot water by using the normally wasted heat from the air conditioning process. While operating in this mode the COP will essentially double. This Geoflex option is commonly used where there would be a very large hot water need (eg. restaurant) or in some cases to heat a pool in the summer. The ODHW+ system will also operate as is described above, which are most commonly used to heat a hydronic in-floor or a zoned hydronic hot water air coil heating system. With a specifically designed water coil or specialized heat exchanger, an On Demand Hot Water System can also be used to heat an indoor or outdoor swimming pool on demand.

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Air Distribution

GSHP, forced air units work efficiently and offer excellent comfort levels because they provide a small temperature rise, but this means that the air coming through the register on your floor is not as hot as the air from a gas or oil furnace. The lowering of the difference between incoming and outgoing air temperatures, helps to maintain a more constant and comfortable indoor environment. Since the air must circulate at a defined rate through the air coil of the GSHP, airflow is a critical component to efficiency and a quality installation. Since the air temperature differential is lower, a GSHP unit must heat more air to supply the same amount of heat to your home and duct sizes are generally slightly larger to reduce noise and to accommodate the higher CFM (Cubic Feet per Minute) air flow rate than those used for combustion furnaces. The GSHP ducting system is generally designed to reduce air noise at every point within the system. It is standard practice to insulate the ducts with noise dampening duct insulation at least 10 feet from the system. It is also common practice to use canvas connections at the main supply and return plenum to avoid noise migration to the house. These two issues, among others are are generally covered under installation best practices and procedures. Although all installers will strive to keep competitive, issues such as these should never be overlooked for cost savings.

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Optional Configurations

There are a number of factors that will have a major influence on the installation and performance of an earth energy or ground source heat pump (GSHP) system. It is important for a homeowner to understand these issues. The hot water and other options will all affect the operational efficacy and efficiency, therefore it is very important to look at all options during the design and selection process.

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Dual Stage vs. Two Speeds

A dual system differs from what is commonly referred to as a two-speed system in many specific ways. A two-speed system would be used for instance when the cooling load is dramatically different than the heating load or visa versa. Two-speed systems utilize the same compressor where a two staged system uses two separate compression sections. A two Speed System will operate very efficiently on low speed but when you switch to high speed the efficiency will drop. Therefore sizing will be a much more important factor with two speed systems. The benefit to using a Two Stage or two separate compressors, is that the COP will be relatively equal whether you are operating in stage one or both stages. A dual staged system would commonly be used in a home where the heat loss is above 60,000 BTU. This would traditionally be a larger home in a very cold climate or a very hot climate. In a climate where the heat loss and heat gain are reasonably close to one another a single system would be used. Dual Compressor Systems offer unparalleled efficiency because they can be sized specifically to the heat loss and heat gain. For example, in a home that has a heat loss of 90,000 BTU and a heat gain of 30,000 BTU, a two staged system would be used to offer the total heat loss with both compressors operating, then one compressor would be used for the cooling mode. Although a dual system offers excellent efficiency and comfort levels, the capitol cost is obviously higher, therefore, capitol cost vs. efficiency and zoning must be considered at the design stage.

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In-floor Heating & Hydronic Backup Hot Water Fan Coils

As stated in the Auxiliary/Emergency heat section, a "Hydronic Hot Water Coil" is often employed where a customer has the opportunity to use hot water directly from their domestic "quick response" hot water tank. Fuel type is the key to help boost the heat output at times of very high heating demand. Using a GSHP complete with a Hydronic Hot Water Coil as backup is commonly referred to as a Dual Fuel System. An electric Hot water tank would not be used in this application, except where a Demand Hot Water Option has been built into the GSHP. An ODHW System is designed to offer the homeowner a fully functional "quick response" hot water system, which can be turned on and off based on the hot water demand. If a hydronic fan coil or In-floor heating has been installed, along with an ODHW, the ODHW would be the, highly efficient source of heat. If a hydronic fan coil has been installed along with an independent quick response hot water tank or boiler, that system would operate independent to the Geothermal System.

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Dual Fuel Option or System

A Dual Fuel Option or System, describes the ability to use two fuel sources. It can be added as a second fuel source to a Geothermal System or it can be manufactured as a specified dual fuel system. Dual fuel systems commonly utilize any combination of electric, gas, propane, oil or solar as the energy source. As energy costs are increasing it is becoming more common to integrate Solar Hot Water Heating into a dual fuel heating and electric or geothermal cooling system.

The dual fuel option can be built into any Geoflex, Forced Air Heat Pump or Liquid Cooled Air Conditioning System and will operate as a forced air hydronic back-up, emergency or can be configured as a dual fuel system. The Dual Fuel System/Option allows the homeowner to take heated water from any hot water source and circulate it through the Dual Fuel Hydronic Coil, allowing the heat to be circulated throughout the space via the existing forced air system.

Here is a good example where a dual fuel system would make perfect sense. You could use a liquid cooled air conditioning which could heat your pool water with the normally wasted rejection heat, while air conditioning your space then you could heat a hydronic air coil within the same forced air system fed from a hot water tank to heat the space. In this case the dual fuel could be natural gas, propane, oil and electric. In this example the dramatic savings will come from the extra benefit of pool heating from energy that would normally cost more to throw away.

The operation of a dual fuel system is relatively simple. When the dual fuel or hydronic back-up option is chosen, the room thermostat will energize a small internal or external circulating pump and will circulate hot water from any hot water source but commonly from a hot water tank, to the dual fuel hydronic coil within the system. The blower fan forces cooler return air over the dual fuel heat transfer coil and the heat from the water will transfer to the cooler incoming air and the heated air will transfer and be circulated throughout the homes ducting system.

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Passive Cooling Option

Passive Cooling is an option that is available in some Geothermal, including Geoflex Heat Pumps. It is an optional system which is added to the system to take advantage of pre-cooled lower underground temperatures at the end of the heating season. When the heating season ends, it is common to switch over to the air conditioning mode and if you have a cool ground loop or water source, you can circulate the cooler fluid through an optional Independent Passive Hydronic Coil, which would be installed in the return side the geothermal forced air system, offering cooling without the need to turn on your compressor. The fluid is commonly circulated through the Independent Passive Coil by using the pre-existing, low wattage loop pumps or in the case of a water well system, the pre-existing well pump would take care of the circulation. If it is an automated thermostatically controlled system, the two stage thermostat will call for cooling and the unit will automatically default to Passive Cooling as the first stage of cooling operation. In the case where the ground temperature or water source is cool enough to deliver the required air temperature to the space, then the Passive will continue to operate, eliminating the need to turn on the compressor for the hours, days or months that the ground bank is cool enough to supply the required cool temperature. If the ground bank heats up and the Passive cannot keep up with the demand of the space, the automated system will automatically switch to active cooling, based on the thermostats staging system. The savings can be very dramatic, again depending on the ground or water source temperatures and the base loading of the space.

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Loops, Open or Closed

A loop describes and open or closed system of transfer in a loop. A Closed Loop System, whether it be on the inside of the space, outside or in the earth, simply describes a loop which is closed and in the case of a Geothermal Heat Pump with liquid circulating through it to efficiently transfer heat energy. An Open Loop or Ground Water System is generally used to describe a open well system, where you would take water out of the well and after taking or rejecting some of the heat energy then dump the water somewhere else on the property. A Pump & Dump System commonly refers to a system which would take water out of a body of water eg., a pond, river, lake or any other water reservoir opportunity and then return the water back to the same body of water.

Slinky (Concentrated) Closed Loops

A Slinky loop refers to a closed loop which is wound in a circular (slinky) fashion, in a sense concentrating the loop pipe in a wide, normally horizontal trench. Slinky loops have been researched and applied over the years and used for specific applications, however, "a professional design is crucial" to a high quality installation. As with any concentrated closed loop arrangement, a slinky loop does not reduce the land mass required to accommodate the "load of the building". The trenches for a slinky loop are commonly, wider and further apart than with a standard straight run out loop. The slinky loop arrangement is also commonly used in a pond or lake loop, as the slinky arrangement offers an excellent way to tie the loop circuits together in a grid fashion, commonly on a mat. Horizontal slinky loops can be "set on their ends with the loop circles standing up" or "laying down with the loop circles touching and commonly attached to one to the next". Spacing is a very important design issue. A Slinky loop standing up can be more difficult when is comes to purging, as there is a higher potential for air to trap at the top of each standing circle pipe. Laid down Slinky loops are commonly horizontally laid in a circular pattern within a trench of varying widths, depending on the chosen pipe size, selected in the design, with one circle overlapping onto the next and so on. There are pros and cons to Slinky and other Concentrated Closed Loop arrangements and a professional design must be done to avoid potential short or long term problems with the loop.

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Open-Water or Open-Well

An open well system borrows water from a dug or a drilled well, then directs the water through the GSHP system. Heat is then extracted from the water in winter or rejected in summer, then the cooled/heated water is returned to a pond, river, lake, weeping discharge pit or discharge well, in accordance with local environmental regulations. Depending on the location, the standard environmental "rule of thumb" is to return the water that is utilized to the same aquifer level, at another point on the same property, where the water was originally drawn. A Geothermal System does nothing to negatively affect the water quality that it uses; it absorbs or rejects heat only. The discharge system must be designed to accommodate any locally sensitive environmental issues.

If the source of water is a lake, river or pond, the body of water must be large enough to provide a sufficient "heat sink" capacity. Rivers can be used as a source of water, but sources with high levels of salt, chlorides or other minerals are not recommended for most units. Each region/province/state has regulations concerning the use of water and if a closed loop is used in the body of water, there are generally laws/guidelines concerning the position of GSHP loops in navigable waterways.

It should be noted that it is common to order your geothermal heat pump with a specialized water coil when using an open well system to avoid any potential water quality issues and allow for periodic flushing, if required..

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Water Quality

Open water systems depend on a source of water that is adequate in temperature, flow rate and mineral content. A national Canadian performance standard (CSA C446), rate GSHP Systems, based on their heating efficiency when the entering water temperature is 10oC (0oC for closed loop units). The output drops, when the entering temperature of water is lower. Each GSHP model has a specified flow rate of water that is required, and its output drops if this rate is reduced. The flow rate required for cooling can be set much lower than for heating, since it is much easier to reject heat than to absorb heat. The CSA installation standard demands an official water well log to quantify a sustainable water yield. Water for open-loop systems must be free of many contaminates such as chlorides and metals, which can damage the heat exchanger of a GSHP unit. Specially designed heat exchangers can be installed at the manufacturing level, if there is a concern in regards to water quality. Contact your manufacturer or installing dealer, if have a concern.

A closed loop system must be filled with good quality water and must be free from any contamination or any kind of debris, including things like pipe shavings, etc.

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Water Discharge

There are environmental regulations which govern how the water used in an open-loop system can be returned to the ground. A return well is acceptable, as long as the water is returned to the same aquifer or level of water table. A discharge pit can also be acceptable, as long as local regulations are followed and appropriate conditions are considered in the design. Water discharge is not an issue with a closed loop system.

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Horizontal Closed Loops

Horizontal loops are the most common configuration of closed loop systems in North America. A trench is dug on the property and High Density, Fusible, Polyethylene pipe is laid and appropriately spaced in the bottom of the trench, then buried in a continuous or parallel loop (depending on size of unit). The most common depth is to bury a loop at least 300mm (1 foot) below the frost level. It is possible to layer more than two pipes in each trench, thereby reducing the cost of digging. If a double layer of pipe is used in a single trench, then the trench must be deep enough to allow for thermal separation. It is important to backfill the trench properly, to avoid air pockets that can reduce the transfer of heat, and to ensure that the pipe is not damaged by large sharp rocks.

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Pond, River and Lake Closed Loops

A closed pond, river or "lake loop" system is positioned on the floor of a body of water instead of being buried in the ground, as with a standard horizontal loop. The pipe must be weighted properly to remain on the bottom of the lake and to avoid shifting caused by spring ice movement. It is common to attach the loop pipe to a non-polluting plastic mesh, such as winter snow fencing, then floated out to the area of choice. This configuration will create a loop grid as one circuit. The circuits are then connected together to create one loop system, appropriately sized to the installed system. When the loop is filled, it will sink to the bottom of the lake, pond or riverbed. Weights are commonly attached to the top of loop grid to hold them in position. Over a short period of time the lake bed will cover the loop, creating a protective barrier and aqua culture. Care must be taken to avoid harming the pre-existing aqua culture. You should consider the positioning of the loop to avoid areas that boats commonly anchor. An anchor can cause a loop to be moved and or ruptured.

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Vertical Closed Loops

This is the most expensive type of closed loop but is a very efficient configuration, due to the fact that the under-earth level of heat increases and generally stabilizes with depth. It is also more than likely that a drilled hole will pierce through an aquifer running water across the loop on a regular basis, which helps to increase efficiency. This option is viable when surface property is limited or has difficult terrain. Care must be taken to ensure that the vertical bore holes are drilled according to provincial/state/regional regulations.

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Septic Systems and Loop

A common question is, "Can I install my loop close to my septic system to take advantage of the heat that is going down my drain"? The answer is, it is not wise to place your loop close to your septic bed. Although a Geothermal System can easily take the heat away from the septic bed, a septic bed requires heat to help with microbial action to break down the sewage, which weeps from the system. If you take that heat away, the microbial action can stop and you may harm your septic bed. Local building codes will apply with this issue. There are methods to take advantage of gray water heat but this application should be discussed with your local building officials to ensure a proper system. A grey water re-capture system would require two separate sewage systems within your home, one for sewage and one for grey water.

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Thermal Fusing, Headered Loop

Thermal fusing of closed loop circuits (circuit and loop size based on design) underground or above ground, refers to the process of joining polyethylene pipe, using heat fusion, in which two sections of plastic pipe are trimmed, cleaned, aligned, heated to the melting point, brought together, and allowed to cool. Heat fusion generally results in a joint that is actually stronger than the pipe itself. For reliability, all underground piping must be thermally fused, rather than mechanically coupled. It is common to "heat fuse" pipes together in a reverse parallel fashion underground and then only two pipes would be fed into the building for hook-up to the Geothermal Heat Pump, creating a reverse parallel closed loop. After the header has been completed and hooked to the Geothermal Heat Pump you have a closed loop, which is commonly purged of all air, then pressurized to approximately 30 psi, standing pressure. Reverse parallel is use on an underground header to ensure balanced flow between circuits.

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Manifold Closed Loops

It is common to use underground thermal fusing to create and underground header arrangement, however, another method would be to bring each individual circuit into the building to a Manifold System. Once the circuits of pipe have been fed through the wall an onto the Manifold, two lines would be taken and joined to the Geothermal Heat Pump. Although an internal Manifold is commonly used, an outdoor Manifold can also be created and then bring only two pipes through the wall to be joined to the Geothermal System inside the building. As a Manifold generally requires no underground joints, heat fusing is not normally required, eliminating the need for specialized loop fusion tools. Once the Manifold has been installed and hooked up to the Geothermal Heat Pump, you have created a Closed Loop System. Manifolds commonly come with individual valve controls for each circuit, which will help reduce the time and effort required for air purging. Purging air is necessary on any closed loop but a manifold with individual circuit control makes the job easier because you can then purge one circuit at a time, requiring a smaller pump. Since each circuit is controls with shut off valves, you essentially have a serviceable loop. As with any closed loop, on a retro-fit application, if all pipes are brought through the wall and into the building, care must be taken to ensure that the the pipes are sealed against water leakage. It is common to use a corrugated pipe sleeve to house all of the incoming and outgoing pipes when going through the wall of the building but again, properly sealing the sleeves is imperative. On a newly constructed building it is common to run the sleeves, under the foundation walls and pre-locating them in the building close to the geothermal heat pump, prior to pouring the foundation.

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Soil Type

Loose dry soil traps air and is less effective for the heat transfer required in GHSP technology than moist packed soil. Besides building loads, soil type is a major factor with appropriate loop sizing and design. Each manufacturer provides specifications on the relative merits of soil type; low-conductive soil may require as much as 50% more loops than a quality high-conductive soil. The more moisture, the better conductivity..

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Loop Pipe Type

The pipe that has been most commonly used for GHSP installations is a high density, polyethylene pipe. There would normally be two grades: "series 125" for residential installations, and "series 160" for commercial installations. However, there are various new types of pipes used in geothermal applications. PE100 is a pipe is now commonly used, as it offers higher pressure rating with a thinner wall thickness. A thinner wall thickness will help to increase the thermal transfer capabilities of the pipe and should ultimate reduce pipe cost. Pipe is commonly thermally heat fused at the time of installation to eliminate any underground mechanical joints. When a pipe is properly heat fused, the point of fusing is stronger than the pipe. Most loop pipe manufacturers offer a 50-year warranty. GSHP pipe comes in three common diameters: 0.75", 1" and 1.25". Coiled loops (commonly called a "Slinky") can require less trenching than conventional straight pipe, however, land mass should remain the same. However, a spiral loop is considered a more concentrated loop and care should be taken to make sure that the loop is not too concentrated otherwise, ice lensing can occur causing long term issues with efficiency and ground settling issues.The ground overall mass required with straight verses the slinky pipe should be approximately the same. Care must be used when back filling a slinky type loop to ensure that pipes are spaced properly. In some cases a slinky loop requires sand back filling around the loop pipe itself. Although straight and slinky pipes are commonly used, the installing dealer will generally install their preferred pipe size and type.

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Loop Location

A closed loop can be located anywhere on the property. It should be noted that as a general rule of thumb, the loop could be placed in the wettest portion of the property. The wetter the better for thermal transfer reasons, generally holds true, so for example if you have an area of swampy ground, the loop would be well located in that area. Loop pipe size, spacing and trench or vertical hole spacing must be considered as critical variables when designing the loop. Spacing and In any case, provincial/state/regional regulations and safety precautions must be observed at all times.

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Loop Sizing

Loop sizing is a critical component of a properly designed geothermal closed loop system, no matter what the loop type. It should be noted that the loop sizing is based on the total heating cooling loads of the space. It is common to try to use basic rules of thumb sizing based on the size of the heat pump, which is not recommended. A qualified designer should be employed to design an appropriate loop system to match the building loads. the loop circuiting is a also a critical component, as the circuiting, pipe size, initial soil temperatures in the project region and of course building loading factors are all variables of consideration. the circuiting relates the Reynolds number, which essentially measures the ability for the loop to pick-up or reject energy and the associated pressure drops of the loop. Suffice to say that loop sizing is without question and incredibly important part of overall good system design and should be be taken lightly. A geothermal system offers incredible efficiencies, if properly designed and the ground loop is what enables us to take advantage of renewable energy which is available 100% of the time. Given the high COP's that today's advanced Geothermal heat pumps offer, you could note that we can essentially heat our spaces with 3/4 of the energy coming out of the ground 100% of time. So suffice to say that loop sizing and design is an incredibly important part of the story.

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Loop Depth

GSHP technology relies on stable underground (or underwater) temperature to function efficiently. In most cases, the deeper the loop is buried, the more efficient the system. Normally a loop pipe will be buried approximately 1 foot or 30 cm below the frost level. A vertical bore hole type loop is commonly the more efficient configuration, but this type of drilling can be very expensive. Column loops offer similar benefits to vertical but can be much less expensive to install, depending on the region and soil type.

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Loop Length

The longer the amount of piping used in a GSHP outdoor loop, the more heat that can be extracted from the ground (or water) for transfer to the house. Installing less loop than specified by the manufacturer will result in lower indoor temperature, and more strain on the system as it operates longer to compensate for the demand. However, excessive piping can also create a different set of problems, as well as additional cost. Each manufacturer provides specifications for the amount of pipe required. As a broad rule of thumb, a GSHP system requires 400 to 500 feet of horizontal loop, or 300 to 350 feet of vertical loop to provide heat for each ton of unit size. With proper design, the loop field is normally cut into a number of circuits, depending ion many design variables. For example, a 3/4" pipe would normally not go beyond 600' in length per circuit, so a horizontal loop field could consist of 4 X 600' circuits of 3/4" pipe to accommodate a specified load.

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Loop Spacing

The greater the distance between buried loops, the higher the efficiency. Industry guidelines suggest that there should be 3 meters (10 feet) between sections of buried loop, in order to allow the pipe to collect heat from the surrounding earth without thermal interference from the neighboring loop. This spacing can be reduced under certain conditions. It is common to bury one set of loops above another set with a deeper trench. This would be covered under application designs. A rule of thumb here would be, "more ground mass is "always" better than less".

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Heat Transfer Fluids

Closed-loop GSHP units can circulate any approved "anti-freeze" fluid inside the pipe, depending on the performance characteristics desired. Each manufacturer must specify which fluids are acceptable to any particular unit, with the most common being denatured ethanol or methanol (the latter is not approved for use in Ontario, Canada because of the high flash point). It should be noted that generally the anti-freeze on an indoor system is commonly not the same anti-freeze used on an outdoor loop, as the pumping characteristics are different for each application.

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Other Applications for GSHP's

With modifications, GSHP units can be used for the dehumidification of indoor swimming pool areas, where the unit can dehumidify the air and provide condensation control with a minimum of ventilation air. The heat recovered from the condensed moisture is then used for heating domestic/pool water or for space heating. Although this is an application for GSHP systems, specific geoflex systems are more commonly used to accomplish the goal of dehumidifying indoor poolrooms.

Efficient heating performance makes GSHP a good choice for the heating and cooling of commercial and institutional buildings. Some examples of commercial applications would include offices, stores, hospitals, hotels, apartment buildings, schools, restaurants and larger government buildings.

GSHP systems heat water or heat/cool the interior space by transferring heat from the ground outside, but they can also transfer heat within buildings with a heat producing central core. Since GSHP technology facilitates Energy Transfer, they can move heat from the core to the perimeter zones where it is required, thereby simultaneously cooling the core and heating the perimeter.
GHSP systems are also used as heat recovery devices to recover heat from building exhaust air or from the wastewater of an industrial process. The recovered heat is then supplied at a higher temperature at which it can be more readily used for heating air or water.

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